SM6.1 | Advances in monitoring and studying the presence and migration of fluids within the crust using multi-disciplinary approaches
EDI
Advances in monitoring and studying the presence and migration of fluids within the crust using multi-disciplinary approaches
Co-organized by ERE5/GMPV5
Convener: Grazia De LandroECSECS | Co-conveners: Tony Alfredo Stabile, Jean Vandemeulebrouck, Nicola DAgostino, Michele Paternoster
Orals
| Thu, 27 Apr, 08:30–12:30 (CEST)
 
Room D2
Posters on site
| Attendance Thu, 27 Apr, 14:00–15:45 (CEST)
 
Hall X2
Orals |
Thu, 08:30
Thu, 14:00
Fluids permeate and diffuse within the crust being originated by internal or external natural sources or by industrial activities for modern energy exploitation and production. Fluids are involved in several geological processes occurring within the seismogenic crust. Fluid-induced stress changes (seasonal forcing due to surface water redistribution, overpressure within the natural reservoirs and/or along the fault planes, industrial wastewater injection, etc.) can reactivate faults and generate deformation and earthquakes. In volcanic environments, fluids play a key role in governing the evolution of magmatic processes and eruption. In this view, it becomes crucial to reliably image fluid storages and track their movement through the crust. New and innovative methodologies and technologies permit 1) to reconstruct the 4D (space and time) variations of rock physical and geochemical properties in a fluid-filled porous medium, 2) detecting and tracking fluids migration, and 3) studying fluid-related effects (such as induced microseismicity, electric properties changes and surface ground deformation). Hence the scientific communities have a new generation of powerful tools for seismic, volcanic and industrial hazard assessment.
This session focuses on main results obtained within the project FLUIDS funded by the Italian Ministry for Research, which was aimed at developing and applying an integrated multi-parametric and multi-disciplinary approach to image and track crustal fluids at selected test-sites in volcanic, tectonic and industrial exploitation environments. The session focuses also on latest research, field studies, modelling aspects, theoretical, experimental and observational advances on detection and tracking of fluid movements and/or pore fluid-pressure diffusion in different environments worldwide, and on the analysis of their correlation with the induced/triggered seismicity.
We welcome contributions on advances in seismic, geochemical and deformation monitoring; multidisciplinary studies combining different data types and observations; characterization and space-time variations of electrical and seismic elastic/anelastic crustal properties, including stress and pressure changes; and physical and/or statistical analyses for the recognition of peculiar seismicity patterns. The session also encourages contributions from early career scientists.

Orals: Thu, 27 Apr | Room D2

Chairpersons: Grazia De Landro, Nicola DAgostino
08:30–08:35
08:35–08:45
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EGU23-12491
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SM6.1
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solicited
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Highlight
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On-site presentation
Federica Magnoni, Emanuele Casarotti, Dimitri Komatitsch, Raffaele Di Stefano, Maria Grazia Ciaccio, Carl Tape, Daniele Melini, Alberto Michelini, Antonio Piersanti, and Jeroen Tromp

The evolution and state of geological structure at Earth’s surface is best understood with an accurate characterization of the subsurface, where fluid distribution plays a key role. We present high-resolution seismic tomographic images of tectonic and geological features of the Italian lithosphere based on ground motion recordings and obtained through an iterative procedure. Enhanced accuracy is enabled by state-of-the-art three-dimensional wavefield simulations in combination with an adjoint-state method. The resulting tomographic model characterizes the subsurface structure in terms of compressional and shear wavespeed values at remarkable resolution, corresponding to a minimum period of ~10 s. As primary findings of our work, images of the lithospheric structure in Central Italy are consistent with recent studies on the distribution of fluids and gas (CO2) within the Italian subsurface, allowing us to infer the presence of deep melted material that induces shallow gas fluxes, or traps and deep storage of gas that can be correlated with seismicity. We illuminate Mt. Etna volcano and support the hypothesis of a deep reservoir (~30 km) feeding an intermediate-depth magma-filled intrusive body, which in turn is connected to a shallow chamber. We also investigate the intriguing features of the Adriatic plate offshore of the eastern Italian coast. Tomographic evidence reveals a structure of the plate made of two distinct microplates with different fabric and behavior, and separated by the Gargano deformation zone, indicating a complex lithosphere and tectonic evolution.

How to cite: Magnoni, F., Casarotti, E., Komatitsch, D., Di Stefano, R., Ciaccio, M. G., Tape, C., Melini, D., Michelini, A., Piersanti, A., and Tromp, J.: Adjoint Tomography of the Italian Lithosphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12491, https://doi.org/10.5194/egusphere-egu23-12491, 2023.

08:45–08:55
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EGU23-7667
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SM6.1
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Highlight
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On-site presentation
Ortensia Amoroso, Ferdinando Napolitano, Gylfi Páll Hersir, Þorbjörg Ágústsdóttir, Vincenzo Convertito, Raffaella De Matteis, Sveinborg Hlíf Gunnarsdóttir, Vala Hjörleifsdóttir, and Paolo Capuano

The harnessed Nesjavellir geothermal area is one of several geothermal fields on the flanks of the Hengill volcano, SW-Iceland. In this study, we present a detailed seismic imaging of the area through the mapping of the VP, VS and VP/VS ratio using seismic data recorded from 2016 to 2020 and compare them to a resistivity model from the same area and rock temperature measured in boreholes. To obtain reliable initial hypocenter locations and a reference seismic velocity, we solve the coupled hypocenter-velocity problem and obtain a reliable minimum 1D P-wave velocity model for the study area. First, we performed the relocation of all the events in the catalogue using the new 1D velocity model and the estimated  VP/VS value of 1.77. We chose the highest quality events based on the quality of the relocations and used them to perform the 3D tomographic inversion. We used an iterative linearized delay-time inversion to estimate both the 3D P- and S-wave velocity models and earthquake locations.

The results highlight that at depths less than 1 km the crust has a high VP/VS ratio (around 1.9) and low VP and VS values. Low resistivity at comparable depths in the same region has been explained as being due to the smectite clay cap. The observed low VP/VS ratio of 1.64 to 1.70 for depths between 1 and 3 km coincides with high resistivity values. The seismicity in this region, where temperatures often exceed 240°C, seems to be sparse and concentrated near the production wells. This seismicity has been explained as being caused by both production and tectonic activity.  At depths larger than 3 km significant high VP/VS ratio anomaly (>1.9) is observed and coincides spatially with a deep-seated conductive body that domes up at about 4.500 m b.sl. Elevated temperatures are observed above this structure in borehole temperature data. We propose that these signals reflect hot 600-900°C cooling intrusives, close to the brittle ductile transition - possibly the heat source(s) of the geothermal field above. These anomalies are at the same location as the last fissure eruption in Hengill almost 2,000 years ago. A deeper NNE-SSW trending seismic cluster at 3-6 km depth, likely outlining an active fault, is observed at the edge of this high VP/VS anomaly. The heat source of the Nesjavellir geothermal field is most likely connected to this most recent volcanism as reflected by the deep-seated low resistivity body and high VP/VS ratio, located beneath the deep fault that connects the flow path of the high temperature geothermal fluid, resulting in an actively producing reservoir.

The availability of a 3D model represents a starting point for 4D tomography study which will allow us to track changes in crustal properties over time and the estimation of fault mechanisms and kinematic source parameters.

This work has been partially supported by PRIN-2017 MATISSE project, No 20177EPPN2, funded by the Italian Ministry of Education and Research.

How to cite: Amoroso, O., Napolitano, F., Hersir, G. P., Ágústsdóttir, Þ., Convertito, V., De Matteis, R., Gunnarsdóttir, S. H., Hjörleifsdóttir, V., and Capuano, P.: Seismic Imaging of the Nesjavellir geothermal field, SW-Iceland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7667, https://doi.org/10.5194/egusphere-egu23-7667, 2023.

08:55–09:05
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EGU23-5861
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SM6.1
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ECS
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On-site presentation
Simona Gabrielli, Aybige Akinci, Luca De Siena, Edoardo Del Pezzo, Mauro Buttinelli, Francesco Maesano, and Roberta Maffucci

The Amatrice (Mw 6.0) - Visso (Mw 5.9) - Norcia (Mw 6.5) seismic sequence (hereafter AVN) struck the Central Apennines (Italy) in 6-7 months during 2016-2017, and it has been widely associated with fluid migration in the normal faults network. The analysis of attenuation parameters (e.g., scattering and absorption) gives information about material properties and the presence of fluids and fracturing. In this study, we investigate in a 3D mapping the scattering contribution to the total attenuation of the AVN seismic sequence (August 2016-January 2017), together with a pre-sequence dataset (March 2013-August 2016). We applied peak delay as a proxy of seismic scattering, to obtain further information on the fracturing processes in time and space. Previous 2D mapping of peak-delay time and coda attenuation tomography in the same study area indicated a substantial control on the scattering of seismic waves by structural (e.g., Monti Sibillini thrust) and lithological (e.g., Umbria- Marche and Lazio-Abruzzi geological domains) features.
Our 3D results show clear differences between the pre-sequence and the sequence, where we can identify an increase of scattering with time after the mainshocks. The substantial alterations in scattering are observed between 4 - 6 km depth, in the hanging wall of the Monti Sibillini thrust, which acts as a rheological barrier between high and low scattering zones. Peak delay variations detected a significant anomaly in the Triassic deposits layer, at the roots of the Acquasanta thrust, east of Monti Sibillini. Here, low scattering during the pre-sequence epoch is replaced by high scattering during the mainshocks. The low scattering along the Acquasanta thrust suggests an increment of pore pressure, associated with the presence of fluids in this geological formation. The subsequent release of those fluids may have caused the mainshocks of the seismic sequence, and a subsequent increase in fracturing, as observed by the high scattering anomaly. These results bring a new light on the importance to consider the thrusts systems in the tectonic framework of the Central Italy.

How to cite: Gabrielli, S., Akinci, A., De Siena, L., Del Pezzo, E., Buttinelli, M., Maesano, F., and Maffucci, R.: The impact of tectonic structures on the 3D scattering imaging of the Central Italy Seismic Sequence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5861, https://doi.org/10.5194/egusphere-egu23-5861, 2023.

09:05–09:15
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EGU23-6668
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SM6.1
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ECS
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On-site presentation
Stefania Tarantino, Piero Poli, Nicola D'Agostino, Gaetano Festa, Maurizio Vassallo, Gerardo Ventraffrida, and Aldo Zollo

Non-linear response of the elastic properties of the crust has been studied using the analysis of seismic velocity variations induced by various natural forcing agents (earthquakes, tides, volcanic processes, and others). Here we study 1) the variations of seismic velocities in response non-tectonic deformations associated to phases of groundwater recharge/discharge in large karstic aquifers in the Southern Apennines of Italy and discuss 2) the implications in terms of non-elastic behavior of the crust. Karst systems are complex aquifers common within the carbonate rocks of the Apennines. They store large amount of groundwater producing significant horizontal dilatational strains that modulate the secular, tectonic deformation (~3 mm/yr extension across the Apennines) and background seismicity (Silverii et al., 2019; D’Agostino et al., 2018) with seasonal and multi-seasonal signatures. The availability of accurate and temporally-long hydrological measurements (rainfall and karst spring discharge) in addition to dense seismic and geodetic networks provide the opportunity to assess the elastic response of the crust to strain forcing at various periods and the sensitivity of relative velocity variations to non-tectonic, hydrological strain variations. We performed velocity variation measurements on seismic noise autocorrelation signals recorded at seismic stations for different coda waves time lapse and compared them with strain measured by the GPS network. We observe that seismic velocities decrease during dilatation episodes (high hydraulic head) and increase during contraction (low hydraulic head). We find that the retrieved strain sensitivity of seismic velocity changes is of the order of ~103 and discuss such sensitivity with previous natural and laboratory results.

How to cite: Tarantino, S., Poli, P., D'Agostino, N., Festa, G., Vassallo, M., Ventraffrida, G., and Zollo, A.: Strain sensitivity of seismic velocity variation induced by hydrological forcing of karst aquifers in the Apennines, Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6668, https://doi.org/10.5194/egusphere-egu23-6668, 2023.

09:15–09:25
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EGU23-1774
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SM6.1
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ECS
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solicited
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Highlight
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Virtual presentation
Shujuan Mao, Albanne Lecointre, Robert D. van der Hilst, and Michel Campillo

Historic levels of drought, globally, call for sustainable freshwater management. Under pressing demand is a refined understanding of the structures and dynamics of groundwater systems. Here we present an unconventional, cost-effective approach to aquifer monitoring using seismograph arrays. Employing advanced seismic interferometry techniques, we calculate the space-time evolution of relative changes in seismic velocity, as a measure of hydrological properties. During 20002020 in basins near Los Angeles, seismic velocity variations match groundwater tables measured in wells and surface deformations inferred from satellite sensing, but the seismological approach adds temporal and depth resolutions for deep structures and processes. Maps of long-term seismic velocity changes reveal distinct patterns (decline or recovery) of groundwater storage in basins that are adjacent but adjudicated to water districts conducting different pumping practices. This pilot application bridges the gap between seismology and hydrology, and shows the promise of leveraging seismometers worldwide to provide 4D characterizations of groundwater and other near-surface systems.

How to cite: Mao, S., Lecointre, A., van der Hilst, R. D., and Campillo, M.: Space-time monitoring of groundwaterfluctuations with passive seismicinterferometry, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1774, https://doi.org/10.5194/egusphere-egu23-1774, 2023.

09:25–09:35
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EGU23-2254
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SM6.1
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ECS
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On-site presentation
Francesco Pintori, Federica Sparacino, and Federica Riguzzi

The Matese massif is an extensive outcrop of Apenninic Platform carbonate rocks located at the boundary between Central and Southern Apennines (Italy), extending ~74 km from NW to SE over an area of ~1600 km² and reaching a maximum height of 2050 m. Its geological history documents different phases of compressional and extensional tectonics which modeled the shape and size of faults within the massif. The present seismotectonic background belongs to the extensional style of the Central-Southern Apennine chain, with a series of NW-SE active extensional faults and occurrence of seismic activity, which reached intensities up to IX MCS.
The karst features of the Matese significantly affect the hydrology of the massif, where rainfall trends lead to large variations in the water reservoirs.
Recent papers report the presence of deformations induced by the elastic response of the loaded surface and the poroelastic properties of the ground. These two mechanisms are different: in the first the water load causes subsidence, in the second uplift. However, under anisotropic conditions, water pressure changes in poroelastic rocks can induce large horizontal deformations especially where highly fractured rocks may provide permeability for fluid flow. When the porosity is determined by systematic fractures, the medium is anisotropic and the surface deformation is mainly perpendicular to the fracture system. To study such processes, we analyzed the time series of 7 GNSS permanent stations located in the Matese area, and the seismicity, covering the 2005-2022 time interval. The GNSS time series of each station were detrended from a best-fitted linear model plus eventual steps due to instrumental changes, without modeling periodicities, obtaining three time series of residual displacements (N, E, Up) for each site. 
We also analyzed spring discharge and pluviometric data. The latter are used to compute the rainfall excess as the difference between the cumulated daily rainfall and the best-fitting straight line of the cumulated rainfall. Then, we applied an Independent Component Analysis to the GNSS data. This allowed us to extract from the time series, in a blind way, a signal very well correlated with hydrological data. This geodetic signal has a large horizontal amplitude and occurs perpendicular to the fracture orientations. This is also shown by the horizontal strain tensor estimated from the displacements associated with this signal, whose maximum extension axis reaches up 1µstrain perpendicular to the fault direction.
During wet periods, characterized by high rainfall excess and increasing values of spring discharge, we observe extensional deformation with stations moving “away” from the massif center; during dry periods a compressional deformation occurs, with stations coming back “toward” the massif. This suggests that the water stored within the massif is the driver of such geodetic signal: the larger the water pressure is, the larger the extensional deformation becomes; when the water level decreases, the water pressure is reduced and then compressional deformation occurs. 
Further studies should be done to understand if water circulation also indirectly affects the background seismicity. 

How to cite: Pintori, F., Sparacino, F., and Riguzzi, F.: Hydrogeologic processes drive deformations in the Matese massif (Southern Italian Apennines), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2254, https://doi.org/10.5194/egusphere-egu23-2254, 2023.

09:35–09:45
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EGU23-11775
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SM6.1
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ECS
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Highlight
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On-site presentation
Léa Perrochet, Giona Preisig, and Benoît Valley

Natural groundwater level fluctuation in karstic networks resulting from significant recharge (precipitation and/or seasonal snowmelt) can potentially induce seismicity. Triggering is often considered to be the result of pore pressure diffusion front migrating from the surface to focal depth, assuming a homogeneous crust. Although this assumption can be acceptable in some cases (e.g. homogeneously fractured basement) it is hardly justified in known karstic area. Considering the specific features of karst and data of three case studies, we elaborate a conceptual model of rain-triggered seismicity in karstic regions by identifying potential triggering mechanisms and, using simplified analytical solutions, quantifying their impact on fault stability. Results of this analysis indicate that a direct hydrogeological connection between karstic conduits and the hypocenter can lead to pore pressure variation of the order of MPa, potentially initiating a rupture. To test the conceptual model, field investigations are carried out in the Jura Mountains, a well-known karstic area with low to moderate seismicity. Data acquisition consists in monitoring the natural microseismicity and the flowrate at karstic springs, used as a direct proxy for groundwater level fluctuations.Combining both data sets allows to identify events that are potentially rain-triggered and to acquire a quantitative knowledge on what pressure change, inferred from the hydraulic head increase, is affecting the fault’s stability, a valuable information when planning underground projects.

How to cite: Perrochet, L., Preisig, G., and Valley, B.: Hydrogeologic and microseismic monitoring as a tool to evaluate fault criticality in karstic regions, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11775, https://doi.org/10.5194/egusphere-egu23-11775, 2023.

09:45–09:55
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EGU23-15583
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SM6.1
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On-site presentation
Thanushika Gunatilake and Stephen A. Miller

Earthquakes are typically followed by a series of aftershocks. Deeply trapped and internally generated high-pressure fluid diffuses along permeable paths and subsequently reactivates faults that drive thousands of seismic events. The thermal decomposition of CO2 in the carbonate regime in the central Apennines contributes significantly to seismogenesis and provides substantial quantities of internally derived high-pressure fluids. We develop a 3-dimensional model of non-linear diffusion with a source term that diffuses along faults and to the surroundings, triggering seismicity along the flow paths, and compare model results with the spatial and temporal observations from the 2009 L'Aquila (Mw 6.3) and the 2016 Amatrice-Visso-Norcia (Mw 6.5) earthquake sequences. The model mimics the generation of additional fluid by thermal decomposition and shows solid correlations in space by comparing the calculated fluid pressure field and the locations of over 50,000 well-constrained hypocenters.

In contrast, other earthquakes result in only a small number or even no aftershocks. These include the Peru earthquake (Sep. 25, 2013 -Mw 7.1), the Mexiko earthquake (Sep. 19, 2017 - Mw 7.1), and the Crete earthquake (Oct. 12, 2021). Additionally, great earthquakes in Pakistan (Jan. 18, 2011 - Mw 7.2) and Iran ( Apr. 16, 2013 -Mw 7.7) also spawned no aftershocks despite the high magnitudes. These phenomena can be linked to the dynamics of volcanic arcs.

How to cite: Gunatilake, T. and Miller, S. A.: Linking Aftershock-free significant earthquakes to the dynamics of volcanic arcs; and linking aftershock-rich significant earthquakes to devolitization., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15583, https://doi.org/10.5194/egusphere-egu23-15583, 2023.

09:55–10:05
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EGU23-1017
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SM6.1
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ECS
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On-site presentation
Alessio Lavecchia, Andrea Tallarico, Vincenzo Serlenga, Tony Alfredo Stabile, Giacomo Prosser, Marilena Filippucci, and Stuart Clark

Over the last decades, many studies highlighted the close relationship between thermal structure, surface processes, and tectonic forces in controlling the deformation of the lithosphere. The contribution of these key factors, however, is not constant in time and may result in a complex deformation history, as already observed in many regions around the globe. In this view, the rheology of the crust is pivotal to leading regional tectonic evolution.

Among the factors that may cause remarkable strength and rheological variations in the crust, the presence of fluid phases is undoubtedly one of the most prominent. The mechanisms of rock-fluid interaction are still a debated field of research. However, it has been suggested in many studies that a major effect of fluids is enhanced seismicity of regions where they are present.

In this framework, the Val d’Agri represents a perfect example of how crustal evolution can be influenced by several factors interacting with one another. In this region, we analyze the relationships between different mechanisms in the final structural setting of the region, with implications on the natural and induced seismicity. To this aim, we built up a numerical model that integrates the combined effects of rheological stratification of the crust, inherited zones of weakness, variations in the tectonic regime, surface erosion, and fluid presence. Our results show that variation in the strength of the evaporite layer between the carbonate platform and the basement has a profound impact on the tectonic style of the Val d’Agri. The uplifting and subsidence pattern in the region follows stages of slow vertical movements to stages of very fast uplifting and denudation, due to the activation of new tectonic structures where movement is enhanced. This reflects on pressure and temperature variations in time, that follow typical yo-yo patterns observed in several tectonically active regions. The present-day configuration of the VA is also influenced by the erosion rate. More in detail, a comparison between the observed structures in the area and our model’s results with varying erosion rates suggests that the VA has been subjected to medium to fast erosion during its evolutionary history. In addition, our model predicts the presence and orientation of faults where fluid percolation or injection at high pressure can generate clusters of microseismicity.

How to cite: Lavecchia, A., Tallarico, A., Serlenga, V., Stabile, T. A., Prosser, G., Filippucci, M., and Clark, S.: Effects of rheological variations, erosion, and geotherm characteristics on tectonic setting and seismic activity in the Val d’Agri (Southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1017, https://doi.org/10.5194/egusphere-egu23-1017, 2023.

10:05–10:15
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EGU23-13270
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SM6.1
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ECS
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Highlight
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On-site presentation
Andrea Barone, Gianluca Gola, Antonio Pepe, Pietro Tizzani, and Raffaele Castaldo

In volcanic environment, the fluids migration in the crust can affect the evolution of magmatic processes. Meteoric water can for instance infiltrate volcanic rocks developing shallow hydrothermal systems and descending meteoric water may encounter fluids rising up from deep magma feeding system. The accurate tracking of fluid storages and movements turn out to be crucial for the evaluation of the seismic and volcanic activity. Specifically, Campi Flegrei caldera is an example of fluids interaction of different nature, especially at Solfatara crater, where the complexity of this volcanic system is highlighted by diffuse degassing, high temperatures and bradyseism phenomenon.

The Solfatara crater was formed at about 4.2 ka and it consists of a sub-rectangular depression, whose geometry is controlled by N40-50W and N50E trending fault systems. Nowadays, degassing and fumarolic emissions occur at the Solfatara crater, together with a series of small uplift episodes and seismic swarms, particularly from 1984 to 2006 when the whole caldera subsided. Specifically, these earthquakes are likely to be associated with a buried cavity filled with a water-vapour mixture at poor gas-volume fractions.

In this scenario, we propose a 2D multi-physics study of Solfatara volcanic system via the integration of thermodynamic and poroelastic model results.

We start with the first model, for which we collect the available geological and geophysical information, such as the main faults, crustal parameters and the temperature distribution in the conductive regime. This information is merged into a multiphysics Finite Element Model by using COMSOL Multiphysics software: we simulate the crustal thermal regime beneath the Solfatara crater by performing a time-dependent convective thermal model in porous media. We also simulate the fluids circulation in accordance with the Darcy’s Law by considering the bi-phasic water properties (i.e., liquid and vapor states) as approximation to characterize the modelled fluid. Furthermore, the seepage of meteoric water through the high permeable volcanic rocks is also considered. At the end of the simulation, we observe the activation of a convective cell below the Solfatara crater, where the 250°C isotherm reaches ~500 m b.s.l.. The retrieved results is compared with the available data, as the resistivity model proposed by Siniscalchi et al. (2019) and the measured temperature at the CF23 well.

Within the same discretized numerical domain, we perform the second model by considering the previous fluid pore pressure modelled field; we detect the pressure source parameters better explaining the observed ground deformations of Campi Flegrei caldera. The analysed dataset consists of processed SAR images acquired by Sentinel-1A/B satellites constellation during the 2020 – 2022 time interval. We here compare the retrieved stress field within the caldera with the hypocenters distribution.

In conclusion, this study contributes to improve the knowledge about the role of fluids migration in the framework of the magmatic processes.

How to cite: Barone, A., Gola, G., Pepe, A., Tizzani, P., and Castaldo, R.: Fluid migration in volcanic environment: thermo-poroelastic modelling of Solfatara crater., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13270, https://doi.org/10.5194/egusphere-egu23-13270, 2023.

Coffee break
Chairpersons: Tony Alfredo Stabile, Michele Paternoster, Jean Vandemeulebrouck
10:45–10:50
10:50–11:00
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EGU23-4376
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SM6.1
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solicited
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Highlight
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On-site presentation
Antonio Caracausi

In seismic regions, fluids play active roles during the preparatory phases of large earthquakes and, through their chemical and isotopic signature, transport to the surface information about deep processes within the fault zones.

In this scenario, noble gases are useful to investigate earth degassing, and their isotopic ratios help to decipher the dynamics of natural processes such as volcanic eruptions and earthquakes. The lightest of noble gases is helium (He), and in natural fluids, it is present with two isotopes, 3He and 4He. The former being mainly primordial and stored in the mantle, the latter continuously produced by U and Th decay in the earth interior. In stable continental region the He flux is dominated by the radiogenic 4He that is produced into the crust (mantle He <1%).  In contrast, primordial 3He escape to the atmosphere in regions of active tectonic (from extensive to compressive).

Experimental studies highlighted that during rocks deformation micro-fracturation increases as an effect of dilation, and consequently, He is liberated from rocks and it escapes towards the pore fluids and successively to the atmosphere. Hence, it indicates a direct link between seismicity and the crustal 4He degassing. However, it is mandatory to know the volume of the rocks involved in earthquakes-induced rock-fracturation to quantify the amount of He released in seismic processes.

Fault zones are complex systems whose mechanical properties evolve over time. Field observations and experimental works allow to schematically simplify these zones into two main structural regions: (1) the fault core and (2) the damage zone. However, the lack of direct observations limits the knowledge of their architecture at depth. Thus, in order to understand the multi-scale, physical/chemical processes responsible for the faulting that earthquakes occur on, it is fundamental to consider phenomena that intersect different scientific research fields. Near Fault Observatories (NFOs) are grounded on multidisciplinary infrastructures, collecting near fault high resolution scientific data that allows generation of innovative observations (Chiaraluce et al., 2022).

Here, we analysed a 12-year earthquake catalogue (M<4) in the IRPINIA NFO (Italy), a region affected by high-magnitude disastrous earthquakes (i.e. M= 7.0 in 1857 and M= 6.9 in 1980).

The analysis of this earthquakes catalogue allows reconstructing year by year the volumes of both the fault core and the damage zone. We computed the 4He output from the two faults zone observing that the low-magnitude earthquakes (M < 4) efficiently contribute to variations of the crustal helium output into the atmosphere. Our results support the impulsive nature of He degassing in tectonically active continental regions (Caracausi et al., 2022). We recognized a quantitative relationship between crustal helium outputs and the volume of fault zones, and  we suggest that variations in helium flux may represent a gauge of changes in the stress field that are related to the nucleation of earthquakes.

 

References

Caracausi et al. (2022). doi:10.1038/s43247-022-00549-9.

Chiaraluce et al. (2022). doi:10.4401/ag-8778.

How to cite: Caracausi, A.: Earthquakes and helium: evidences of the impulsive nature of earth degassing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4376, https://doi.org/10.5194/egusphere-egu23-4376, 2023.

11:00–11:10
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EGU23-2043
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SM6.1
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ECS
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On-site presentation
Lorenzo Chemeri, Marco Taussi, Jacopo Cabassi, Francesco Capecchiacci, Franco Tassi, Alberto Renzulli, and Orlando Vaselli

The Province of Pesaro-Urbino (northern Marche, central Italy) represents one of most seismically active areas in Italy, since it is interested by the presence of two major composite seismogenic sources: i) the first one is located in the Umbria-Marche Apennines; ii) the second one is along the Adriatic coast from Cattolica to Ancona cities. This area has recently experienced an intense seismic activity, e.g., the 1781 “Cagli Earthquake” with a magnitude of 6.4 Mw, and the 1930 “Senigallia Earthquake” of 5.8 Mw. The last earthquake (5.5 Mw) occurred on November 9, 2022, with its epicenter located in the Adriatic Sea, 35 km away from the city of Pesaro. Since the geochemical knowledge of this area is limited, a large-scale sampling survey was carried out during spring and autumn 2022. A total of 87 samples were collected from different types of emergencies (i.e., cold springs, wells, mineral springs, sulfur springs and ditches) and various geological and tectonic-structural contexts. The study area is dominated by a complex sedimentary structure (e.g., limestones, clays and alluvial deposits) and by climatic and topographic conditions that may influence the chemical and isotopic composition of the investigated fluids. A detailed geochemical characterization is thus of paramount importance in order to define a geochemical background. The aim of this study was to (1) understand the possible interaction of deep-originated fluids and shallow aquifers and (2) evaluate the use of selected geochemical parameters as possible seismic tracers. The results showed the presence of five different geochemical facies: (i) calcium-bicarbonate waters with low TDS (<500 mg/L); (ii) calcium-bicarbonate waters with a strong enrichment in sulfate (up to 200 mg/L); (iii) waters with extreme sodium-carbonate composition and an alkaline pH (>8.8); (iv) calcium-sulfate waters; and (v) sodium-chloride waters. The water isotopic composition showed a clear meteoric origin for all the investigated samples. The composition of major dissolved gases showed two different compositional clusters: (a) N2-dominated gases with N2/Ar ratios similar to those of air and ASW (Air Saturated Water); (b) CO2- and CH4-rich gases pertaining to mineral and sulfur springs. The origin of Ca-HCO3 waters is almost exclusively related to the dissolution of carbonate minerals. On the contrary, Ca-HCO3(SO4) waters are probably originated by deep circulation pathways and interactions with the Upper Triassic Burano Formation, composed by anhydrite layers. The Ca-SO4 waters should be considered as the product of ongoing flows within Miocene gypsum formations, whilst Na-HCO3 waters as the consequence of long-lasting interactions between meteoric waters and silicate rocks (containing albite) in saturation/oversaturation conditions for carbonate-bearing minerals. Finally, the Na-Cl waters probably derive from mixing processes between meteoric and highly saline connate waters trapped into the foredeep clayey deposits. Therefore, the Ca-HCO3(SO4) and Ca-SO4 waters can be regarded as the most interesting fluids to be monitored for a geochemical network aimed at recognizing chemical and isotopic variations related to seismic activity. They are indeed showing a deeper hydrogeological pathway and appear to be less influenced by surface processes.

 

How to cite: Chemeri, L., Taussi, M., Cabassi, J., Capecchiacci, F., Tassi, F., Renzulli, A., and Vaselli, O.: Hydrogeochemical characterization of the waters circulating in the seismically active area of the Pesaro-Urbino province (northern Marche, central Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2043, https://doi.org/10.5194/egusphere-egu23-2043, 2023.

11:10–11:20
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EGU23-8292
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SM6.1
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On-site presentation
Francesca Di Luccio and the The FURTHER Team

An accurate survey of old and new datasets allowed us to probe the nature and role of fluids in the seismogenic processes of the Apennines mountain range in Italy. Geodynamics, geophysical and geochemical observations highlight differences between the western and eastern domains of the Apennines, and the main characteristics of the transition zone, which spatially corresponds with the overlapping Tyrrhenian and Adriatic Mohos. Tomographic images exhibit a large hot asthenospheric mantle wedge that intrudes beneath the western side of the Apennines and disappears at the southern tip of the southern Apennines. This wedge modulates the thermal structure and rheology of the overlying crust as well as the melting of carbonate-rich sediments of the subducting Adriatic lithosphere. As a result, CO2-rich fluids of mantle-origin have been recognized in association with the occurrence of destructive seismic sequences in the Apennines. The stretched western domain of the Apennines is characterized by a broad pattern of emissions from CO2-rich fluids that vanishes beneath the axial belt of the chain, where fluids are instead trapped within crustal overpressurized reservoirs, favoring their involvement in the evolution of destructive seismic sequences in that region. In the Apennines, areas with high mantle He are associated with different degrees of metasomatism of the mantle wedge from north to south. Beneath the chain, the thickness and permeability of the crust control the formation of overpressurized fluid zones at depth and the seismicity is favored by extensional faults that act as high permeability pathways. This study strongly relies on the multidisciplinary analysis of different datasets (both existing and newly acquired) with the most advanced methodologies to stimulate the knowledge of the fluid-related mechanisms of earthquake preparation, nucleation and space-time evolution. Ongoing and future investigations will include the continuous and simultaneous geochemical and geophysical monitoring at the scale of the outcropping seismogenic faults to properly decipher the link between earthquake occurrence, surface rupture and fluid release.

How to cite: Di Luccio, F. and the The FURTHER Team: The role of CO2 degassing in the seismogenic process of the Apennines, Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8292, https://doi.org/10.5194/egusphere-egu23-8292, 2023.

11:20–11:30
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EGU23-8375
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SM6.1
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ECS
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On-site presentation
Matteo Scarponi, Francesca Di Luccio, and Claudia Piromallo

The Apennines mountain range develops all along Italy, presenting important variations in terms of both structural and tectonic environments, and seismogenic patterns as well. This is observed not only along the main NW-SE chain axis, but also by comparing multidisciplinary observations between the western Tyrrhenian and the eastern Adriatic domains (Di Luccio et al., 2022).

We focus on the southern Apennines, where the Adriatic plate subducts westward under the thinner Tyrrhenian plate and the highest seismic release is documented.

Recent studies showed that fluids play an important role in the seismic behavior of the area. The western domain is associated with heterogeneous and distributed patterns of CO2 gas emission at the surface; the latter ceasing in the east, where high-pressure fluids are trapped in crustal pockets and affect the seismogenic cycle (Chiodini et al., 2004; Improta et al., 2014; Di Luccio et al., 2022 and references therein).

We perform regional-scale P- and S-body waveform analysis and forward numerical modeling, for a selected catalog of crustal events recorded by the broadband seismic stations of the italian network, as well as of temporary passive seismic experiments. We focus on a SW-NE transect, which cross-cuts the southern portion of the Apennines chain, and along which the recorded waveforms exhibit important differences in terms of frequency content and pulse shape. Along the same transect, the waveforms from two events (2013 Mw5 Sannio-Matese and 2014 Mw4.5 Gargano earthquakes) show significant differences in the propagation towards the east and west, respectively.

Starting from two velocity models such as EPcrust (Molinari et al. 2011) and the adjoint tomographic model of Magnoni et al. (2022), we use the finite difference numerical modeling code nbpsv2d (Li et al. 2014) to produce synthetic waveforms to fit and explain the observations. By including information on the earthquake source mechanism and by improving the waveform fit in terms of both arrival time and body-wave coda, we provide new, preliminary information on the crustal structure of the southern Apennines, aimed at improving our understanding of the fluid-seismicity interaction in the area.

 

Research performed in the framework of FURTHER project (https://progetti.ingv.it/en/further).

 

References:

 

  • Chiodini G., Cardellini, C., Amato, A., Boschi, E., Caliro, S., Frondini, F., and Ventura, G. (2004). Carbon dioxide Earth degassing and seismogenesis in central and southern Italy. Geophys. Res. Lett., 31, L07615, doi:10.1029/2004GL019480.
  • Di Luccio et al., (2022). Geodynamics, geophysical and geochemical observations, and the role of CO2 degassing in the Apennines. Earth-Sci. Rev., https://doi.org/10.1016/j.earscirev.2022.104236
  • Improta L., P. De Gori, and C. Chiarabba (2014). New insights into crustal structure, Cenozoic magmatism, CO2 degassing, and seismogenesis in the southern Apennines and Irpinia region from local earthquake tomography, J. Geophys. Res. Solid Earth, 119, 8283–8311, doi:10.1002/ 2013JB010890.
  • Li, D., Helmberger, D., Clayton, R. W., & Sun, D. (2014). Global synthetic seismograms using a 2-D finite-difference method. Geophysical Journal International, 197(2),1166-1183.
  • Magnoni, F., Casarotti, E., Komatitsch, D., Di Stefano, R., Ciaccio, M. G., Tape, C., ... & Tromp, J. (2022). Adjoint tomography of the Italian lithosphere. Communications Earth & Environment3(1),1-12.
  • Molinari, I., & Morelli, A. (2011). EPcrust: a reference crustal model for the European Plate. Geophysical Journal International185(1), 352-364.

How to cite: Scarponi, M., Di Luccio, F., and Piromallo, C.: Waveform modeling of moderate earthquakes for the comprehension of the seismic structure and the fluid-seismicity interaction beneath the southern Apennines (Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8375, https://doi.org/10.5194/egusphere-egu23-8375, 2023.

11:30–11:40
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EGU23-9565
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SM6.1
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On-site presentation
Luisa Valoroso, Spina Cianetti, Pasquale De Gori, Giovanni Diaferia, Carlo Giunchi, Luigi Improta, Davide Piccinini, Luciano Zuccarello, Rocco Cogliano, Antonio Fodarella, Felice Minichiello, Stefania Pucillo, and Francesca Di Luccio

The role of fluids in the preparatory phase of major earthquakes and in the evolution of aftershocks and swarms in space and time is well-documented. In particular, numerous studies evidence the primary role that mantle-derived fluids play in the generation of large upper crustal earthquakes in extensional domains, where crustal-scale faults act as preferential hydraulic pathways.  

We focus on the Mefite D'Ansanto degassing site, the largest low-temperature non-volcanic CO2 emission in the world, located at the northern tip of the Mw6.9 1980 Irpinia faults. The study area experienced strong historical earthquakes (1702, 1732 and 1930 M6+ earthquakes) but it is characterized by a relatively low background seismicity rate with respect to the nearby Sannio and Irpinia regions.    

To collect high-quality microseismicity data in this key sector of the southern Apennine extensional belt and investigate the relationship among seismicity, crustal fluids, and physical-hydraulic properties of the crust, we installed in July 2021 (up to May 2023) a temporary network composed of 10 stations equipped with short-period velocimeters (5 sec). The temporary network covers an area of approximately 30x30 km2 surrounding the Mefite d’Ansanto site and integrates with the numerous permanent stations of the INGV and ISNet networks located at the boundary of the survey area. 

Within the Mefite area, we also deployed a temporary seismo-acoustic dense array to study two CO2 vents. The seismo-acoustic array is composed of 5 infrasonic stations equipped with IST-2018 broadband microphones developed by The ISTerre (Université Savoie Mont Blanc, France), in addition to one seismo-acoustic station equipped with a co-located digital broadband seismometers (120s). The array is positioned approximately at the vertices of a star, with an aperture of about 50 meters. The deployment lasted for 1 week at the end of May 2022, allowing us to sample the emission site during “dry” weather conditions. 

We show first results of the analysis of seismicity recorded by the temporary network applying both standard (STA/LTA) detection algorithms or innovative enhanced techniques such as cross-correlation based template-matching algorithms and/or Deep-Learning-Phase-Recognition methods.

The activities are developed in the framework of the multidisciplinary project FURTHER (https://progetti.ingv.it/en/further).

How to cite: Valoroso, L., Cianetti, S., De Gori, P., Diaferia, G., Giunchi, C., Improta, L., Piccinini, D., Zuccarello, L., Cogliano, R., Fodarella, A., Minichiello, F., Pucillo, S., and Di Luccio, F.: Passive seismic and infrasonic monitoring at the Mefite d’Ansanto deep-CO2 degassing site (Southern Apennines, Italy)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9565, https://doi.org/10.5194/egusphere-egu23-9565, 2023.

11:40–11:50
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EGU23-14488
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SM6.1
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ECS
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Virtual presentation
Elzbieta Weglinska, Andrzej Lesniak, Andrzej Pasternacki, and Pawel Wandycz

Structures created by hydraulic fracturing can be identified using the location of induced microseismic events. Estimating the effectiveness of stimulation depends on fracture mapping. Event location errors make precise imaging of fractures in a scattered seismic cloud challenging. In order to increase the reliability of the determined structures on the basis of events with location error, we proposed a several-stage procedure. This procedure was demonstrated on microseismic events located during the fracturing of the Wysin-2H/2Hbis horizontal well, an exploration well for shale gas in northern Poland from June 9, 2016 to June 18, 2016. All located events were subjected to a collapsing that allows obtaining new locations of events that are equivalent to original locations in a statistical sense. The creation of such an equivalent point cloud allows us to see certain structures that may reflect, for example, fractures. To validate the results before and after collapsing method, all events were set against the probability of a given brittleness index map.  It is demonstrated that the collapsed events occurred in regions that were more rigid, while the locations of events prior to this procedure showed no relationship with the occurrence of areas with higher susceptibility to fracking. The unsupervised machine learning algorithm HDBSCAN was used on a collapsed cloud to automatically detect clusters of events. The directions of identified clusters agree with the direction of regional maximum horizontal stress.

How to cite: Weglinska, E., Lesniak, A., Pasternacki, A., and Wandycz, P.: Mapping of structures formed by hydraulic fracturing based on microseismic events location., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14488, https://doi.org/10.5194/egusphere-egu23-14488, 2023.

11:50–12:00
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EGU23-7137
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SM6.1
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ECS
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On-site presentation
GuangYao Yin, Huai Zhang, and YaoLin Shi

This study investigates the perturbations of the surrounding stress field caused by the cascade effect of Xiluodu and Xiangjiaba reservoirs after impoundment and a three-dimensional pore-elastic coupling model of the impoundment of cascade reservoirs are established. The finite element method calculates the pore pressure field, elastic stress field, and variation of Coulomb stress on local faults. The results show that: 1) the spatial distribution of the earthquake cluster is obviously consistent with the area where the pore pressure increases; 2) The ΔCFS at the epicenters of the April 2014 Yongshan M_L5.1 earthquake and the August 2014 Yongshan M_L5.2 earthquake imparted by the reservoirs are: 0.67kPa and 10.87kPa, respectively, indicating that impoundment promotes these two earthquakes at different levels, and the latter is more significant; 3) The elastic stress field change imparted by the impoundment of Xiluodu reservoir has an impact on the Xiangjiaba Reservoir in the early stage. However, the earthquakes between two reservoirs are possibly triggered by the latter. The Xiangjiaba reservoir increases the pore pressure in its upstream part by 1.0 kPa; 4) the impoundment of the reservoirs increases the seismic risk of the southern section of the Yanfeng fault and the middle section of the Lianfeng fault, while the Manao fault is less affected.

How to cite: Yin, G., Zhang, H., and Shi, Y.: Cascade effects of triggered earthquakes of cascade dams: Taking Xiluodu and Xiangjiaba reservoirs as examples, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7137, https://doi.org/10.5194/egusphere-egu23-7137, 2023.

12:00–12:10
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EGU23-7351
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SM6.1
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ECS
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On-site presentation
Valeria Longobardi, Sahar Nazeri, Simona Colombelli, Raffaele Rea, Grazia De Landro, and Aldo Zollo

Water injection in geothermal areas is the preferential strategy to sustain the natural production of geothermal resources. In this context, monitoring microearthquakes is a fundamental tool to track changes in the reservoirs in terms of soil composition, response to injections, and resource exploitation in space and time. Therefore, the refined source characterization is crucial to better estimate the size, source mechanism, and rupture process of microearthquakes, as possibly related to industrial activities and to identify any potential variation of the background seismicity. Standard approaches for source parameters estimation are ordinarily based on the modelling of Fourier displacement spectra and its characteristic parameters, the low-frequency spectral level and corner frequency. Here we apply a time-domain innovative technique that uses the curves of P-wave amplitude vs time along the seismogram. The methodology allows estimating seismic moment, source radius, and static stress drop from the plateau level and the corner-time and of the average logarithm of P-wave displacement versus time with the assumption of a triangular moment rate function, uniform rupture speed, and constant/frequency-independent Q-factor. In the current paper, this time-domain methodology is implemented to a selected catalog of micro-earthquakes consists of 83 events with moment magnitude ranging between 1.0 and 1.5, occurred during 7 years (2007-2014) of fluid extraction/injection around Prati-9 and Prati-29 wells at The Geysers Geothermal field.

How to cite: Longobardi, V., Nazeri, S., Colombelli, S., Rea, R., De Landro, G., and Zollo, A.: Time-Domain Source Parameter Estimation of natural and man-induced micro earthquakes at The Geysers geothermal field, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7351, https://doi.org/10.5194/egusphere-egu23-7351, 2023.

12:10–12:20
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EGU23-7724
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SM6.1
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ECS
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On-site presentation
Sahar Nazeri, Fatemeh Abdi, Amir Ismail, Habib Rahimi, and Aldo Zollo

The rupture process of the recent moderate-to-large earthquakes in the longest seismic sector in Iran's plateau, the Zagros area, has been modeled using the strong motion data provided by the Iranian Building and Housing Research Center (BHRC). The selected dataset includes the largest and deadliest seismic event, the 2017 Mw 7.3, Sarpol-e Zahab earthquake. The earthquake source parameters (moment magnitude, source duration, rupture dimension, and average stress drop) are determined by implementing a parametric modeling technique in the time domain based on the time evolution of the P-wave displacement signals. The seismic source parameters are calculated from simulated trapezoidal and triangular moment-rate functions assuming the unilateral rectangle and circular crack models, respectively, where the rupture propagates at a constant velocity as a fraction (90%) of the average shear-wave velocity in the medium. The anelastic attenuation effect assuming the independent frequency-Q parameter ranging from 50 to 200 is accounted for by a post-processing procedure that retrieved the observed moment-rate triangular shape. Hence, the average stress drop with different varies between <Δ𝜎>=1.50 (1.14−1.95) and <Δ𝜎>=0.90 (0.71−1.14) MPa. Assuming a circular rupture model for Sarpol-e-Zahab, we estimate a moment magnitude of 7, rupture duration of 7 seconds, source radius of 16 km, and statistical stress drop of about 3.5 MPa. Alternatively, a unilateral rupture model calculates the fault length and width at 45 and 16 km, with a lower stress drop of 2 MPa.

How to cite: Nazeri, S., Abdi, F., Ismail, A., Rahimi, H., and Zollo, A.: Earthquake source parameters in the Zagros region (Iran) from the time of evolutionary P-wave Displacement, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7724, https://doi.org/10.5194/egusphere-egu23-7724, 2023.

12:20–12:30
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EGU23-16074
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SM6.1
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ECS
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On-site presentation
Ivana Ventola, Gerardo Romano, Marianna Balasco, Michele de Girolamo, Salvatore de Lorenzo, Marilena Filippucci, Roselena Morga, Domenico Patella, Vincenzo Serlenga, Tony Alfredo Stabile, Andrea Tallarico, Simona Tripaldi, and Agata Siniscalchi

Seismo-electromagnetic signals are electromagnetic signals generated by the propagation of a seismic wave in a porous media containing fluids (Gao & Hu, 2010).These signals can potentially provide useful information on the poro-elastic media and the hosted fluids (Garambois & Dietrich, 2002).Thus, there has been a growing interest in the study of SES in recent years, due to their potential.

Researchers are focusing both on modelling and analysis of both passive and active experiments to investigate the characteristics of these signals (e.g. Honkura et al., 2000; Matsushima et al., 2002; Warden et al., 2013; Gao et al., 2016; Balasco et al., 2014; Dzieran et al., 2019).Passive experiments involve the observation and analysis of naturally occurring SES triggered by earthquakes, while active experiments involve the controlled generation of these signals using seismic source.

The aim of our work is to present the results deriving from the analysis of SES recorded with both approaches. As for the passive one, the data set consists of the time series recorded by two magnetotelluric stations in continuous monitoring, co-located with two seismic stations, in seismically active areas of Southern Italy (the Gargano promontory and the Agri valley).

As for the active one, the data set derives by an active seismic experiment carried out in the caldera of the Phlegrean Fields, the Italian super-volcano.

How to cite: Ventola, I., Romano, G., Balasco, M., de Girolamo, M., de Lorenzo, S., Filippucci, M., Morga, R., Patella, D., Serlenga, V., Stabile, T. A., Tallarico, A., Tripaldi, S., and Siniscalchi, A.: Exploring the characteristics of seismo-electromagnetic signals (SES) in both passive and active experiments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16074, https://doi.org/10.5194/egusphere-egu23-16074, 2023.

Posters on site: Thu, 27 Apr, 14:00–15:45 | Hall X2

Chairpersons: Grazia De Landro, Tony Alfredo Stabile
X2.150
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EGU23-9324
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SM6.1
Tony Alfredo Stabile, Matteo Picozzi, and Vincenzo Serlenga

Reservoir-induced seismicity (RIS) related to water-level changes in artificial lakes is a well-documented phenomenon. The best known RIS example is the 6.3 Mw 1967 Koyna-Warna earthquake. However, it must be considered that small-to-moderate magnitude RIS occurs very often, both in relation to water load changes and poroelastic stress perturbation in pre-existing faults. Monitoring the temporal and spatial evolution of RIS is very important for assessing the mechanical state of faults, especially when artificial lakes are located in areas characterized by a high seismic hazard. Indeed, where the crust is affected by the presence of faults with a stress level close to failure, even static stress changes of a few tens of kPa associated with RIS might promote the worst-case scenario of large earthquakes.

Understanding of the physical processes that generate and characterize natural and induced earthquakes, including RIS, is often improved by studying the spatiotemporal evolution of the source parameters obtained through inversion of the seismic data, or by studying the mechanical properties of rocks through seismic velocities. Nevertheless, the source parameters for small magnitude earthquakes such as stress-drop and seismic energy are difficult to estimate, are model-dependent, and, above all, are affected by large uncertainties. Alternatively, the variability of RIS source processes can be investigated by studying the temporal and spatial variability of the ground motion intensity (δBe).

In this work, we investigate the spatiotemporal evolution of ground motion caused by RIS at the Pertusillo artificial lake in southern Italy. The area has a strong seismogenic potential, having been affected in the past by the 1857, Mw 7.0 Basilicata earthquake. We consider ∼1,000 microearthquakes that occurred from 2001 to 2018 and were recorded by a local network of nine seismic stations. The ground motion intensity associated with microseismicity allows us to identify two periods, each lasting approximately 2 years. They are characterized by a high rate of events but exhibit different source properties and spatial distributions. In the first period, the seismicity is spatially clustered close to the lake, on faults with different orientations and kinematics. In the second period, the seismicity is distributed along the Monti della Maddalena faults. Comparing the ground motion intensities of the two periods, we observe that events that occurred in the first period are associated with higher stress levels than others, in agreement with the b-values of the respective frequency-magnitude distributions. We compare the temporal evolution of the ground motion intensity with the rainfall and water levels measured at the artificial lake, as well as with the discharge of a ∼80 km distant spring, which is strictly controlled by climate trends. The results provide information about the regional processes acting on the southern Apennines. Our results show that the microseismicity is clearly associated with the Pertusillo artificial lake in the first period, whereas in the second period is a result of a combination of local effects due to water table oscillations of the lake itself, regional tectonics, and the poroelastic and elastic phenomena associated with carbonate rocks hosting aquifers.

How to cite: Stabile, T. A., Picozzi, M., and Serlenga, V.: Spatio-temporal evolution of ground motion intensity caused by reservoir-induced seismicity at the Pertusillo artificial lake (southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9324, https://doi.org/10.5194/egusphere-egu23-9324, 2023.

X2.151
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EGU23-9822
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SM6.1
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ECS
Grazia De Landro, Tony Alfredo Stabile, Titouan Muzellec, Vincenzo Serlenga, and Aldo Zollo

Monitoring conditions of the medium embedding the reservoir is strictly required for the hazard assessment in exploited areas.

Fluid injection/extraction operations cause a pressure perturbation into the volume hosting the reservoir which, in turn, may trigger new failures and induce changes in the elastic properties of rocks. Therefore, technologies are needed to reconstruct pore-pressure evolution around injection wells.

To test how the conditions of the reservoir can be monitored noninvasively by using induced micro-seismicity, here we show a rock physics approach aimed to reconstruct the pore-pressure temporal evolution from the changes in Vp/Vs ratio.  

We applied this strategy to the volume affected by the wastewater disposal activity of the Costa Molina 2 injection well, located in the High Agri Valley (Southern Italy) and belongs to the Val d’Agri oilfield, the largest productive onshore oil field in West Europe that produces hydrocarbons (oil and gas) from a fractured carbonate reservoir. We analyzed an enhanced seismic catalogue of the induced micro-seismicity, occurred between 2016 and 2018, that consists of 196 located earthquakes in the magnitude range − 1.2 ≤ Ml ≤ 1.2. For the same period, both seismicity recordings and fluid-injection data are available.

For the evaluation of Vp/Vs ratio with the Wadati formula, the accurate measure of arrival time is critical, especially in case of micro-events. So, we first refined with high precision the first P- and S-wave arrival times by using waveform cross-correlation and hierarchical clustering and selected the events with a high DD location quality; then, we calculated the Vp/Vs ratio for each source-station couple and averaged the ratio values for all the events at the stations nearest to the well (INS1, INS2, INS3) to reconstruct the elastic properties temporal evolution in the source region around the well. 

We found that the Vp/Vs ratio temporal evolution well correlates with injection operational parameters (i.e. injected volumes and injection pressures). With a rock physics model, by using the Pride approach of the Biot theory, we reconstruct the pore-pressure temporal variation starting with the Vp/Vs as known parameters, thus demonstrating the value of seismic velocity monitoring as a tool to complement a monitoring system.

How to cite: De Landro, G., Stabile, T. A., Muzellec, T., Serlenga, V., and Zollo, A.: Monitoring pore-pressure from Vp/Vs ratio around the Costa Molina 2 wastewater disposal well in southern Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9822, https://doi.org/10.5194/egusphere-egu23-9822, 2023.

X2.152
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EGU23-12756
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SM6.1
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ECS
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Highlight
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Annukka Rintamäki, Gregor Hillers, Sebastian Heimann, Torsten Dahm, and Annakaisa Korja

Understanding fluid injection induced seismicity is key to safe and successful operations of deep geothermal systems. Efficient geothermal energy extraction by an enhanced geothermal system (EGS) requires increased fluid flow between geothermal wells. The experimental 6-km-deep EGS in the Helsinki capital region, southern Finland is an intriguing natural laboratory in a cool Precambrian shield setting that yields excellent seismic data quality. We investigate the source processes of the earthquakes induced by weeks-long EGS stimulations in 2018 and 2020 via a probabilistic waveform fitting method. Detailed resolution of full moment tensor solutions and their opening components can reveal crucial information on earthquake nucleation and fluid flow patterns.

We present results of a centroid full moment tensor analysis for ~250 events from 2018 and 16 events from 2020 in the moment magnitude range 0.5–1.9. We use three-component data of ~30 stations within a 9-km radius of the well-head site. We fit P- and S-phases by modeling synthetic waveforms using Green’s functions with a 20 m grid spacing based on a homogeneous velocity model. We employ automatic high signal-to-noise ratio waveform selection and automatically determined channel-wise correction coefficients for time shifts and amplitude scaling to represent small scale crustal variations not reflected in the velocity model. With the application of both waveform selection and channel corrections, the uncertainty of the moment tensor decreases on average by ~60 % and the location uncertainty by ~85 %. This results in a catalog of well-resolved moment tensors and centroid locations.

The obtained high-quality solutions are dominated by reverse faulting mechanisms with variable compensated linear vector dipole (CLVD) contribution and non-significant isotropic component. The 3D event distribution reveals largest positive CLVD contribution in seismic sources close to the injection well, which indicates localized fracture opening under constant volume with a simultanous adjacent shear event. Farther from the well, seismic sources have pure double-couple mechanisms or even negative CLVD contribution which may be indicative of fracture lengthening or closing under constant volume at later stages of the stimulation.

Identifying clusters with respect to source type and location within the 3D event distribution supports the interpretation of physical source processes and reveals fluid flow channels, and zones of weakness. Events with positive CLVD component occurring close to fluid-filled fractures are potentially nucleated by direct contact with the injected fluid and the associated pore pressure change. Events with zero or negative CLVD component on the outer parts of the seismicity distribution may have been nucleated by poroelastic stress transfers without a direct hydraulic contact to the injected fluid. Our findings suggest that the full extent of injection induced seismicity may not be indicative of fluid flow and thus it should not be used to estimate the extent of an artificially created connected fracture network of a geothermal reservoir.

How to cite: Rintamäki, A., Hillers, G., Heimann, S., Dahm, T., and Korja, A.: Centroid full moment tensor analysis reveals fluid channels opened by induced seismicity at EGS, Helsinki region, southern Finland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12756, https://doi.org/10.5194/egusphere-egu23-12756, 2023.

X2.153
|
EGU23-17093
|
SM6.1
Aldo Zollo, Sahar Nazeri, Jin Zhen, and Grazia De Landro

To determine the crustal rock rheological properties and model wave propagation in an anelastic attenuating medium, it is necessary to determine the quality factor Q, which expresses the fraction of friction-dissipated energy to total seismic energy. Measuring time-broadening of the first P- and S-wave pulses, we propose a time-domain method to estimate the frequency-independent Q parameter of body waved from microearthquake records. We assume a uniform velocity, circular rupture model as represented by a triangular moment rate/displacement function, whose attenuated velocity pulse widths are analyzed in the near-source distance range. The attenuated velocity pulse width data allow the calculation of the source parameters, including rupture duration/radius and stress drop values, as well as the attenuation factor t* (travel distance/quality factor), used to determine the attenuation structure in the study area. It is noted that the constant coefficient of the pulse-width vs t* relationship, required for calculating the t* catalog, have been calibrated for a triangular displacement waveform through simulation analysis. An evaluation of the methodology was carried out on 126 micro-events with Mw ranging from 1 to 3 located around the PRATI-9 and PRATI-29 injection wells at the Geyser geothermal field, California. The analysis of the P- and S-waves indicates a Qp range of 55 to 100 and a Qs range of 89 to 189. To validate the the t* data, we have inverted them to obtain a 1D QP model that matches consistently with the profiles derived from existing tomographic QP models in the area.

How to cite: Zollo, A., Nazeri, S., Zhen, J., and De Landro, G.: Application of a time-domain method to estimate the attenuation quality factor from the Geysers geothermal field microearthquake records, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17093, https://doi.org/10.5194/egusphere-egu23-17093, 2023.

X2.154
|
EGU23-2027
|
SM6.1
Investigations on the seismic attenuation properties of the High Agri Valley, southern Italy: preliminary results by coda attenuation method
(withdrawn)
Vincenzo Serlenga, Salvatore Lucente, Teresa Ninivaggi, Salvatore de Lorenzo, Edoardo del Pezzo, Marilena Filippucci, Tony Alfredo Stabile, and Andrea Tallarico
X2.155
|
EGU23-1018
|
SM6.1
Andrea Tallarico, Alessio Lavecchia, Marilena Filippucci, Giulio Selvaggi, Gianpaolo Cecere, and Sierd Cloetingh

Several regions around the globe are characterized by a seismically active lower crust, at depths where lithological, thermal and rheological conditions suggest stress release by ductile flow. The Gargano Promontory (GP, southern Italy) is an example where a recently installed seismic network has recorded an intense seismic activity at depths between 20 and 30 km, i.e. in the lower crust. We analyze a possible mechanism controlling the distribution of seismicity in the GP to identify the factors that make the lower crust seismically active. To this aim, we construct a thermo-rheological model of a layered continental crust, calibrated on the basis of geometrical, lithological and thermal constraints. The model takes into account a multiphase crustal lithology, the presence of fluids in the crystalline basement, lateral variations of geotherm and stress field.

The numerical simulations show that the presence of fluids is a key factor controlling the cluster of seismicity in the lower crust. Moreover, the presence of water in the upper crystalline basement and sedimentary cover provides a plausible explanation for upper crustal seismicity in a zone of very high heat flow SW of the GP. The distribution of the seismicity is probably affected by the composition of the crystalline basement, with mafic bodies injected into the crust during the Paleocene magmatic phase that affected the Mediterranean region. Our findings suggest that the presence of hydrous diapiric upwelling(s) in the upper mantle can feed a deep fluid circulation system, inducing lower crustal seismicity.

How to cite: Tallarico, A., Lavecchia, A., Filippucci, M., Selvaggi, G., Cecere, G., and Cloetingh, S.: Role of crustal fluids and thermo-mechanical structure for lower crustal seismicity: the Gargano Promontory (southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1018, https://doi.org/10.5194/egusphere-egu23-1018, 2023.

X2.156
|
EGU23-11047
|
SM6.1
|
Suhee Park, Dabeen Heo, Tae-Seob Kang, Junkee Rhie, Seongryong Kim, and Jan Dettmer

Since the early 2000s, lots of induced earthquakes have occurred due to fluid-injection during the development of unconventional resources at the Kiskatinaw Seismic Monitoring and Mitigation Area (KSMMA) located in northeastern British Columbia, Canada. The spatial-temporal distribution of microearthquakes induced by fluid-injection are important to understand the characteristics of crack and movement of fluid. Also, to mitigate earthquake disasters, it is essential to continuously monitor microearthquakes in fluid-injection areas. We used the seismic data recorded at the EON-ROSE seismic network, which is a dense seismic network consisting of 16 broadband seismic stations, and GSC-BCOGC seismic network to analyze the characteristics of microseismicity of the KSMMA in 2020. We detected the seismic signal (P- and S-wave) using the automatic seismic phase detection method, which is based on the short-term-average to long-term-average ratio (STA/LTA) and kurtosis. And then, we associated the seismic phase arrival data to combine to earthquakes from the automatic seismic phase association method using the temporal distribution of the detected signals and the spatial distribution of the seismic stations used. The hypocenter parameters of associated earthquakes were determined with the HYPOINVERSE location algorithm and the existing 1-D velocity model of KSMMA. The epicenter distributions of the detected earthquakes are concentrated in the area known as active fluid-injection, and the focal depths are also distributed at about 2 km. We analyzed the seismicity by dividing it with three periods based on COVID-19 lockdown and confirmed the low-seismicity of the lockdown period, which is consistent with the result of the independent study performed at the region.

How to cite: Park, S., Heo, D., Kang, T.-S., Rhie, J., Kim, S., and Dettmer, J.: Characteristics of microseismicity in the Kiskatinaw area, northeastern British Columbia, Canada, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11047, https://doi.org/10.5194/egusphere-egu23-11047, 2023.

X2.157
|
EGU23-11035
|
SM6.1
|
ECS
Riddhi Mandal and Semechah Lui

Various injection parameters have been shown to pose significant effects on human-induced seismicity due to a variety of activities such as wastewater injection, carbon storage and geothermal energy production. In this study, we used numerical modeling to investigate how different injection parameters, namely injected volume and injection rate, affect the behavior of faults in the context of fluid-induced seismicity. We tested a large model space (4500 simulations) and modeled injection cases with both spatially homogenous and heterogenous pore-pressure perturbations. Simulation results showed that the two parameters can have various impacts on fault behavior, and that in some cases their effects are interconnected. We discovered that aseismic slip plays a significant role in altering the timing of triggered earthquakes and has lasting impacts on future seismic activity. Moreover, we found that increasing the injection rate tends to increase the size of the triggered cluster of earthquakes, while increasing the injection volume increase the overall rate of earthquakes. We find that spatial heterogeneity has qualitatively similar effects as compared to spatially homogenous cases, with a few quantitative differences. Lastly, we also performed a case study of an injection scenario based on realistic values of pore-pressure diffusion and injection operations in Oklahoma, and we found that for an injection duration of one year, the pore pressure on the faults in the region does not go back to zero even after 70 years and can cause earthquakes years after the end of injection, perturbing the seismic cycles for ~200 years. Our work has potential important implications for safe operation of injection processes which can reduce the risk of seismic hazards.

How to cite: Mandal, R. and Lui, S.: Interdependent effects of injection volume and rate on fault slip behavior: A large-scale numerical study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11035, https://doi.org/10.5194/egusphere-egu23-11035, 2023.

X2.158
|
EGU23-5872
|
SM6.1
|
ECS
Ling Zeng, Hengxin Ren, Kaiyan Hu, Xuzhen Zheng, and Changcheng Li

The current theoretical study of the seismoelectric method is based on two sets of the governing equations, one is the electrokinetic coupling coefficient proposed by pride (1994) which is characterized by the zeta potential. The other is the electrokinetic coupling coefficient proposed by Revil & Linde (2006) which is based on the amount of excess charge in the pore volume. In this study, the Luco-Apsel-Chen generalized reflection and transmission method was used to solve the second set of seismoelectric governing equations and separate their interfacial response signals. The correctness of the algorithm is determined by comparing the consistency of the total interface signal with the superposition of the interface signals of each layer. The properties of the interface signals are investigated and it is found that different interface responses contribute differently to the overall signal and that the amplitude and phase of the interface signals are influenced by frequency and medium parameters.

How to cite: Zeng, L., Ren, H., Hu, K., Zheng, X., and Li, C.: Study of interfacial seismoelectric signals in unsaturated pore media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5872, https://doi.org/10.5194/egusphere-egu23-5872, 2023.

X2.159
|
EGU23-6023
|
SM6.1
|
ECS
Xuzhen Zheng, Hengxin Ren, Changcheng Li, and Ling Zeng

The penetration and diffusion of fluids in fluid-saturated porous media can cause electromagnetic (EM) disturbances due to the electrokinetic effect. These mechanically induced EM waves, often known as the seismoelectric wave fields are sensitive to hydraulic parameters such as porosity and permeability. For in-situ seismoelectric field observations, the source and receivers are usually located at or near the ground surface. However, the current reflectivity-method-based seismoelectric modeling algorithms will suffer computational difficulties due to the slow convergence problem occurring when the source and receiver are located at close or the same depths. To overcome this problem, we extend the peak-trough averaging method to update the seismoelectric modeling algorithm based on the Luco-Apsel-Chen generalized reflection and transmission method. The updated seismoelectric algorithm is then applied to study the seismoelectric coupling phenomena. The results demonstrate that the electric signals recorded by a surface receiver are several milliseconds earlier than their causative seismic waves due to the evanescent seismoelectric conversion. This is capable to interpret similar phenomena reported in seismoelectric field observations over a long history. This time difference may have the potential to identify the location of the groundwater table. Therefore, the updated seismoelectric algorithm is a precise and efficient tool for forward modeling, which also benefits the interpretations of field seismoelectric observations.

How to cite: Zheng, X., Ren, H., Li, C., and Zeng, L.: Seismoelectric conversions due to a ground source in stratified porous media, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6023, https://doi.org/10.5194/egusphere-egu23-6023, 2023.

X2.160
|
EGU23-7574
|
SM6.1
Antonio Troiano, Claudio De Paola, Maria Giulia Di Giuseppe, Carmela Fabozzi, and Roberto Isaia

The hydrothermal area of Pisciarelli, together with the adjacent Solfatara volcano, currently represents the most active structure of the Campi Flegrei caldera in terms of degassing and seismic activity and recently manifesting significant morphological variations, including the opening of new fumarolic vents and mud emission episodes as well as changes in the geochemical characteristics of the gases/fluids. 
To define the structural setting of the Pisciarelli fumarolic field, Electrical Resistivity (ERT) and Time-Domain Induced Polarization (TDIP) tomographies, Self-Potential (SP), Temperature (T), PH and Magnetic (Mag) mapping have been recently realized. 
The geophysical tomographies furnished a 3D model of the area, which reconstructs the Pisciarelli subsurface in its area of maximum degassing, containing the main fumarole (“soffione”) and the mud pool. The comparison of the 3D model with SP, T, PH and Mag maps acquired in the area revealed the occurrence of zones characterized by intense and complex faulting and fracturing processes, affected by fluid circulation, as well as identifying sectors of the subsurface where gases accumulate as also evidenced at the surface by the presence of fumaroles and intense hydrothermal rocks alteration. In particular, the 3D model evidenced an upwelling channel in which fluids stored in a more profound reservoir rise toward the surface. Such a structure seems to be surmounted by a clay-cap formation that could govern the circulation of fluids and the abundance of gases/vapours emitted by the soffione.
The conceptual model proposed for the Pisciarelli fumarolic field suggests plausible mechanisms for explaining, at the same time, the soffione activity and the role played by the deeper origin fluid/gas in the shallow fluid circulation system. In addition, the advance in the understanding of the Pisciarelli fumarolic field setting could also improve the strategy for monitoring the unrest processes in the area and evaluating the associated hazards.

How to cite: Troiano, A., De Paola, C., Di Giuseppe, M. G., Fabozzi, C., and Isaia, R.: Monitoring active fumaroles through electrical and magnetic survey: an application to the Pisciarelli fumarolic field (Campi Flegrei, Italy)., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7574, https://doi.org/10.5194/egusphere-egu23-7574, 2023.

X2.161
|
EGU23-8732
|
SM6.1
Marco Liuzzo, Andrea Di Muro, Andrea Luca Rizzo, Antonio Caracausi, Fausto Grassa, Guillaume Boudoire, Massimo Coltorti, and Bhavani Bénard

Located within the Mozambique Channel, the Comoros archipelago is situated within a complex geodynamic system of great interest owing to recent volcanic and seismic activity (2018-20), but where little gas geochemistry research has been conducted.

Focusing on Grande Comore and Petite Terre, a small islet off the northeast coast of Mayotte, our investigations set out to identify the gas-geochemistry characteristics of the islands, and explore any potential influence from the then ongoing unrest and/or volcanic activity.

Geochemical surveys included measurements of soil CO2 flux on both islands, and gas sampling from fumarolic areas at Karthala volcano (Grande Comore) and two bubbling areas at Petite Terre, with the aim of determining the chemical and isotopic characteristics of the main gases (CO2, CH4, He, Ne, Ar) and equilibrium temperatures of the hydrothermal system at Petite Terre.

δ13C values of soil CO2 emissions highlight evidence of a low magmatic contribution at Grande Comore, while a significantly higher contribution is evident at Petite Terre. 3He/4He data are consistent with average values of fluid inclusions for both Grande Comore and Petite Terre rocks, and are fixed at low value ranges (4.7≤Rc/Ra≤5.9 and 5.3≤Rc/Ra≤7.5 respectively). The gases detected at the two sites of Petite Terre primarily reflect the signature of deep gases in terms of geochemical tracers such as R/Ra and δ13C in CO2.  At one of the two emission sites at Petite Terre, namely the meromictic lake Dziani Dzaha, the gases are relatively more variable in relative proportion of CO2, CH4  and C isotopes; at this specific site, a significant influence from microbial activity is evidenced.

Our results allow us to infer that the general degassing characteristics between the two islands are similar. They also shed light on their reciprocal differences, which may either be attributable to local specifics within Petite Terre, or to different states of volcanic activity between Grande Comore and Petite Terre at the time of the surveys, the latter being a consequence of fluid migration to the mainland of Mayotte during the offshore submarine activity (2018-20).

The outcomes of this work provide a necessary step towards filling gaps in the knowledge of gas-geochemistry in Comoros, and contribute potential support for volcanic and environmental monitoring programmes.

How to cite: Liuzzo, M., Di Muro, A., Rizzo, A. L., Caracausi, A., Grassa, F., Boudoire, G., Coltorti, M., and Bénard, B.: Grande Comore and Mayotte gas-geochemistry and evidence of deep fluid migration during the 2018-2020 submarine eruption off Mayotte, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8732, https://doi.org/10.5194/egusphere-egu23-8732, 2023.

X2.162
|
EGU23-16539
|
SM6.1
|
ECS
Eleonora Vitagliano, Luigi Improta, Luca Pizzino, and Nicola D'Agostino

Pore pressures at depth are usually described in relation with hydrostatic pressures, implying an interconnection between pores and fractures from the earth's surface up to a certain depth. In some cases, pore pressures exceed hydrostatic values, and these overpressures can be interpreted as an equilibrium between geological pressurization mechanisms (e.g., under compaction, tectonics, hydrocarbon generation, dehydration reactions, various sources of fluids, etc.) and pressure dissipation processes, which mainly depend on rock properties (e.g., hydraulic diffusivity).

In actively deforming regions, other subsurface mechanisms may favor the generation of overpressure (e.g., parallel shortening of strata) and in addition, surface topography may drive meteoric groundwater to flow from positive reliefs to nearby lowlands, interacting with deeper fluids.

Within the framework of the PRIN FLUIDS project, the research presented here aims to study the pore pressures collected in 30 exploration wells of the Sannio and Irpinia regions (Southern Apennines thrust-and-fold belt, Italy), with the objective of clarifying if and how deep fluids (e.g., free gas phases such as CO2 and HCs, as well as saline paleo/formation waters with Na-Cl chemistry and high pCO2) interact with shallow waters and to investigate the relation between shallow and deep crustal fluid dynamics and seismogenesis. In the proposed study, pressures, normalized to a hydrostatic profile, have been first retrieved from borehole pressure data, and then projected on five geological transects, to recognize the spatial distribution of the pressure trends (i.e., hydrostatic, over-pressured and hydrostatic over-pressured zones) underneath the Apennines range (from the internal to the external thrust belt) and the Plio-Pleistocene Bradano foredeep. In addition to the structural features, we also used other information available from well profiles (i.e., litho-stratigraphy, geochemical data, thermal data and petrophysical parameters) and open sources (i.e., geothermal gradient and sedimentary facies distribution maps). This material was integrated with the distribution, at the surface, of deep-derived fluids (gas manifestations, thermal springs, CO2-rich groundwater) to calibrate the system. Moreover, the overall data enabled deepening the comprehension of the role of the pressurized layers in acting as possible vertical and lateral barriers to/for fluid migration, and estimating the possible origin and depths reached by the thermal circuits. Finally, with respect to the distribution of pore pressure zones, two other aspects related to the active deformation and fluid leakage were addressed: vertical stress magnitudes at depth and distribution pattern of low-magnitude background seismicity of the area. The analysis on these topics and the preliminary results will be shown at the end of the proposed workflow.

How to cite: Vitagliano, E., Improta, L., Pizzino, L., and D'Agostino, N.: Insights into shallow and deep fluid circulation of the Southern Apennines seismic belt (Italy) using borehole pore pressures, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16539, https://doi.org/10.5194/egusphere-egu23-16539, 2023.

X2.163
|
EGU23-12806
|
SM6.1
Simona Morabito, Lucia Nardone, Simona Petrosino, and Paola Cusano

Mefite d’Ansanto (Italy) is the largest non-volcanic CO2 emission field on the Earth. The isotopic signature of the CO2 testifies a deep origin of the gases emitted at this site, whose source is probably the mantle wedge beneath the Apennines along the Tyrrhenian side (Chiodini et al., 2010). Mefite is located between the Sannio and the Irpinia seismogenic regions, that are considered among the most active areas of the southern Apennines. The emission site falls at the northern tip of the Irpinia fault system that is associated with the destructive MS = 6.9, 1980 Irpinia earthquake. The gas leakage from this zone is linked to active faulting that characterized the area and determined large historical earthquakes

A temporary acquisition survey close to the Mefite emission field was carried out between 8 June and 28 September 2020 by using a seismic array, named Array MEfite (AME), composed of seven short-period stations. We have analyzed the characteristics of the recorded background seismic noise, e.g., spectral properties, energy temporal pattern (RMS) and polarization (Montalbetti et al., 1970), and estimated site effects (Nakamura, 1989; http://www.geopsy.org/). The seismological temporal patterns have been compared with the meteorological parameters, such as temperature and rainfall, to find possible relationships with exogenous factors. We found a well-defined spatial pattern for the spectral components above 5 Hz, which appear clearly linked to the emission field dynamics. On the other hand, the spectral components below 5 Hz result from the overlapping of multiple sources, of both exogenous, such as anthropogenic and meteorological factors, and endogenous nature. Application of the Independent Component Analysis (ICA) technique (Hyvärinen et al., 2001) contributed to discriminate between natural and anthropogenic sources.

 

References

Chiodini, G., D. Granieri, R. Avino, S. Caliro, A. Costa, C. Minopoli, and G. Vilardo (2010). Non‐volcanic CO2 Earth degassing: Case of Mefite d’Ansanto (southern Apennines), Italy, Geophys. Res. Lett. 37, L11303, doi: 10.1029/2010GL042858.

Hyvärinen, A., Karhunen, J. & Oja, E. (2001). Independent Component Analysis. Wiley, New York,

Montalbetti, J. R., Kanasevich, E. R. (1970): Enhancement of teleseismic body phase with a polarization filter. Geophys. J. Int. 21 (2), 119–129.

Nakamura, Y. (1989). A method for dynamic characteristics estimation of subsurface using microtremor on the ground surface, Railway Technical Research Institute, Quarterly Reports, 30 (1), 25-33.

How to cite: Morabito, S., Nardone, L., Petrosino, S., and Cusano, P.: Seismological temporal patterns at Mefite d’Ansanto CO2 emission field., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12806, https://doi.org/10.5194/egusphere-egu23-12806, 2023.

X2.164
|
EGU23-8421
|
SM6.1
|
ECS
Dario Buttitta, Giorgio Capasso, Michele Paternoster, Marino Domenico Barberio, Francesca Gori, Marco Petitta, Matteo Picozzi, and Antonio Caracausi

The geochemical characteristics of fluids that emerge at the Earth's surface are influenced by gas-rock-water interactions in the deep and shallow crustal layers, including mixing, outgassing of volatiles, and precipitation of minerals. The goal of the study was to understand the various interactions that influence the migration and behaviour of fluids within the Earth's crust and how they may change during the process of crustal fluid migration towards a hydrothermal system in the shallow crustal layers and within (Contursi basin, Italy). These processes can make it difficult to identify the source of deep gas by using the classical approach based on mixing processes of fluids and carbonate dissolution. Therefore, alternately the relationship between Total Dissolved Inorganic Carbon (TDIC) and the δ13CTDIC in groundwater from the Contursi hydrothermal system investigating the water-gas-rock interaction at the local scale through the detailed reconstructions of the geological framework at depth have been taken into consideration. We found that both the dissolved and free gas in the hydrothermal system probably originated from a deep CO2 endmember with a δ13CCO2 value ranging from +2.12‰ to +3.20‰ (PDB) depending on the presence of brine or freshwater in the local aquifers. However, we observed that this CO2 lost its pristine carbon isotopic signature during its storage in the deep dolomite-composed reservoirs (6-8 km), making it challenging to figure out its deep origin (decarbonation vs mantle/magmatic CO2). Our calculations also showed that the output of CO2, taking into account secondary processes (i.e. degassing CO2 and calcite precipitation) and interactions with water at different salt concentrations, could be at least 40% higher than estimates from the mixing-only approach, such that it is comparable with several active and quiescent worldwide volcanic systems. In order to interpret potential geochemical changes that may occur during future seismic events in sites like Contursi, which are earthquake-prone areas, it is necessary to implement models that can help us understand fluids origin and the processes that influence their chemical and isotopic signature.

How to cite: Buttitta, D., Capasso, G., Paternoster, M., Barberio, M. D., Gori, F., Petitta, M., Picozzi, M., and Caracausi, A.: Crustal fluid migration and gas-water-rock interaction processes in a seismic area: the case study of the Contursi hydrothermal system (Southern Appenines), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8421, https://doi.org/10.5194/egusphere-egu23-8421, 2023.

X2.165
|
EGU23-16829
|
SM6.1
Geochemistry and chemical U-Pb dating of U-Th mineralization of the Shkhara crystalline massif, Greater Caucasus,  Georgia
(withdrawn)
Avtandil Okrostsvaridze, Franziska Wilke, Davit Bluashvili, Giorgi Boichenko, Salome Gogoladze, and Rabi Gabrielashvili