SM7.1

Seismologists use elastic waves to probe and study the Earth’s interior. With the advent of more portable instrumentation and dense sensor coverage, recent attention has been directed to small scales near our planet’s surface. The resulting field of “environmental seismology” includes a particular focus on natural hazards and mass movements ranging from small rock falls to massive avalanches made up of snow, ice and/or rock. Local and regional seismic networks also capture seismic signatures of stable deformation including sliding and fracture signals accompanying glacier and landslide creep. With the help of passive interferometry, such data furthermore reveal structural changes of potentially unstable masses that may represent failure precursors.

Over the past 1-2 decades, numerous studies have revealed the usefulness of seismology in environmental studies. Consequently, seismic instrumentation is being introduced into monitoring infrastructure to improve warning capabilities and scientific research. This presentation discusses recent seismometer deployments and data mining approaches in environmental seismology. The focus is on Alpine terrain, where dense coverage of earthquake monitoring stations and other seismometers exist, which lends itself to environmental studies. Provided that specific challenges in sensor design and data processing are soon tackled, a range of pilot projects suggests that seismic techniques will soon be part of the next generation of operational monitoring and warning systems in Alpine terrain.

How to cite: Walter, F.: Recent Developments in Environmental Seismology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2585, https://doi.org/10.5194/egusphere-egu22-2585, 2022.

The Tibetan plateau, an uplifted topography situated to the north of the Himalayas, acts as a decisive region for interpretation of the mechanism of continent-continent collision between Indian and Eurasian plates. Sandwiched between the Tethyan Himalaya in the utmost south and Songpan-Gangze plate in the extreme north, the central Tibetan plateau is constructed of two major geological blocks named the Lhasa and Qiangtang terrane, which are detached by the Bangong-Nujiang suture belt. We have calculated Lg Q and shear velocity crustal structure across the ~900 km long Himalayan-Tibetan Continental Lithosphere during Mountain Building (Hi-CLIMB) profile using the decisive two-station method and joint inversion of receiver function and Rayleigh wave group velocity data. The vertical component of broadband seismograms of 37 regional earthquakes, well distributed in NE, SE, and NW backazimuths, recorded by 171 stations are refined to extricate the Lg amplitude spectra. The 1 Hz Lg Q (Q₀) estimated between 29716 pairs of two stations and out of these estimates 2228 number of high trait interstation Q₀ values are used as an input to the 1-D inversion done through singular value decomposition method with Tikhonov regularization to obtain a lateral variation of Lg Q along the profile. To reduce the inherent error in Q₀ measurements, the maximum azimuthal difference between the source and two stations is set to 5⁰ although a threshold of 15⁰ is allowed. The inversion results provide Lg Q₀ values ranging from 66 (parts of lesser Himalayas including Nepal) to 177 (Qiangtang terrane). Previous studies show that the Main Himalayan Thrust (MHT) underthrusting low-velocity sediments from the Ganges Basin manifest the ubiquity of water released from the underthrust sediments hence decreasing the fault strength and triggering large earthquakes. This instability in this part of the profile correlates well with extremely low values of Lg Q₀. Although inside the plateau Lg Q₀ values are seen to be increased, we observe consistent low Q₀ values across the profile which can be associated with a high Vp/Vs ratio, hence reflecting partial melt in the region. Based on our inversion, we estimated crustal thickness along the profile ranging from 45 km to 72 km (South to North) which is well correlated with the previous studies in this region as well as established a positive correlation with our measured Lg Q₀ values. The most striking result is the high Q₀ value in the Qiangtang terrane compared to the previous studies (Q₀<100). The observed difference may be due to the use of a small number of earthquake data, data used from NE and NW backazimuths, use of the high azimuthal difference between the source and two stations (15⁰), and due to the source/path effect, which is not completely removed in the two-station method. To reduce the attenuation-source tradeoffs and improve the resolution a joint tomography of single station and two stations method might be benevolent. The current study provides a new understanding of the region, improving our perception of the crustal formation of the region.

How to cite: Sarma, B., Borah, K., Anand, A., and Santra, S.: Lateral Variation of Shear Velocity and Lg Attenuation Structure along the Hi-CLIMB Profile in Tibet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-238, https://doi.org/10.5194/egusphere-egu22-238, 2022.

Measuring debris-flow properties remains a significant challenge in studies of natural hazards. Recent works suggest that the seismic signals generated by debris flows can help analyze flow dynamics, but theoretical details for estimating bulk flow properties from seismic signals are not fully understood or comprehensively tested. Here, we invert basal force fluctuations on the torrent bed using high frequency seismic signals generated by 6 well-documented debris flows at Illgraben, Switzerland. Verified against independent measurements, our seismically-derived basal force fluctuations match well with the measured basal fluctuations at a force plate and correlate with the bulk flow properties, including flow depth and weight. We propose a physical model employing the multi-particle force chains and random single-particle impacts within a debris flow to simulate the generation of high frequency seismic signals. We find that the random impacts of single particles and of multi-particle force chains are active at the same time, and together they control the debris-flow’s basal force fluctuations. For different events and different positions within events, the relative contributions of single particle impacts and of multi-particle force chains dominating the basal fluctuations vary significantly and control the non-linear relation between the high-frequency seismic signal strength and the bulk flow characteristics. According to our model, fluctuating basal forces are strongly controlled by particle sizes and flow depth. Our results open new perspectives for the understanding of high frequency seismic signals generated by debris flows and the estimation of bulk flow characteristics, such as flow depth and weight.

How to cite: Zhang, Z., Walter, F., McArdell, B., de Haas, T., Wenner, M., Chmiel, M., and He, S.: Linking characteristics of debris flows to their high frequency seismic signature: insights from field measurements and model predictions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2096, https://doi.org/10.5194/egusphere-egu22-2096, 2022.

Debris flow hazard often brings huge economic losses and fatalities downstream. Despite the traditional in-field monitoring system developed, the apparatus is vulnerable to being damaged in the process of hazards, resulting in limited in-situ data collected to analyze the dynamic process. Recently, with the development of seismology, the seismic signals from geophones become an effective method to analyze the process of debris flow for hazard assessment. The scientific challenge lies in how to get the seismic signals of the whole process of debris flow accurately for analyzing the seismic signal characteristics and of debris flow. In this study, two debris flow gullies (Er gully and Chediguan gully in Wenchuan county) are selected to install the monitoring apparatus after field investigation, and two monitoring sites are selected for each gully. The ground vibration monitoring system consists of geophone and Data-Cube. The geophone is fixed in the concrete base which is clinging to the bedrock firmly to collect the seismic signals and save the seismic signals in the Data-Cube. In addition, each monitoring site is equipped with an infrared camera for recording the geomorphologic changes of the monitoring section in the gully, and a rain gauge is installed at the monitoring site upstream of each gully to obtain rainfall information during the whole observation period. The ambient noise in raw seismic signals will be filtered out, and the filter seismic signals are combined with rainfall information to analyze the moment of potential hazards. Then identify debris flow by checking the video of the infrared camera and analyzing the spectrum, spectrogram, and power spectra density of these potential hazards. Finally, the seismic signal characteristics of the debris flow are extracted and analyzed. Based on this, the monitoring and early warning work of debris flow hazards can be guided.

How to cite: Zhou, K., Cui, Y., Yan, Y., and Liu, D.: Research on the seismic signal characteristics of debris flow: an in-field monitoring approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2101, https://doi.org/10.5194/egusphere-egu22-2101, 2022.

Geological hazards occur frequently in Qilian Mountain, causing economic losses and casualties, therefore, this scientific expedition mainly investigates the geological hazards in the Qilian Mountain where the distribution of hazards is uneven, mainly concentrating in the southeast. Due to the inaccuracy of remote sensing interpretation of hazard sites, it is necessary to combine field investigations to calibrate hazard distribution and development trend forecast. Through on-site survey and investigation of each hazard sites, field survey forms and hazard plane sketches should be finished on site. Through unmanned air vehicle survey and on-site sampling, the specific situation of the hazard sites can be acquired, and we can summarize the hazard data to obtain the distribution of hazard sites. We studied the damage forms and characteristics of engineering structures within the influence range of typical disaster chains, and analyzed the combined damage characteristics of different disaster chains and different engineering structures. We researched the possible development trends of potential disaster chains, and predicted their impact and damage on engineering structures. On-site investigation of hazard sites is of great significance in exploring the key links of disaster chain control and proposing monitoring measures for engineering hazard prevention and mitigation.

How to cite: Zeng, C. and Hu, S.: Distribution law and development trend forecast of geological hazards in Qilian Mountain, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2142, https://doi.org/10.5194/egusphere-egu22-2142, 2022.

When studying large landslides any data matters. In fact, in contrast to other scientific branches, data scarcity is a pressing issue especially for high altitude landslides. When large rockslides occur in steep valleys, long runouts can threaten buildings and infrastructures, even though the source area is well above the exposed elements. In such cases, usually no ground-truth monitoring data is available on site, which is needed to understand the causes and processes of the collapse.

Seismic data from a widespread network of seismographs can help to partially fill gaps in the characterization of the above mentioned processes. The most straightforward information that can be inferred from ground motion recordings is the duration of the event – or at least the duration of the most intense and violent phase of the runout. By coupling the velocity of the event with some topographic data leading to the estimation of the detached volume and the deposit distribution, the user may gather sufficient information to produce a satisfactory numerical model through back analysis. In case the topographic data are characterized by high uncertainty and/or poor resolution, seismic records are particularly useful for ground-truthing because they represent an independent source of data.

This study describes the modelling approach used to understand the dynamic of a 365,000 m³ rockslide in the Dolomites (UNESCO World Heritage, North-East Italy). The landslide detached from a steep slope located between 3100 and 2800 m a.s.l. and almost free fell for 600 m. Then it crashed and fragmented in a small rocky hanging valley of glacial origin, subsequently reaching 1400 m a.s.l. with a runout of approximately 2 km. For this area, pre-event and post-event DEMs were available but with different resolution, alignment and coverage. The comparison of pre- and post-event topography allowed the identification and quantification of erosional and depositional areas, the estimation of landslide volume and of the potential errors associated with this type of analysis.

A DAN3D numerical model of the landslide was calibrated using both DEM of Difference (DoD) maps and seismic data. The ground motion records proved to be remarkably useful, as they ensured the reliability of the model notwithstanding the DoD maps intrinsic uncertainties. The seismic data provide a new layer of information in a swiss cheese model of reliability focused on reducing model equifinality and on increasing the overall robustness of the analysis. This finding is fundamental as the results of the back analysis may be used to model and test future scenarios, which can be used to support risk assessment and mitigation.

How to cite: Bossi, G., Gatter, R., Crema, S., and Cavalli, M.: Seismic data as an additional layer of information for large rockslide modelling through back analysis, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2417, https://doi.org/10.5194/egusphere-egu22-2417, 2022.

            We present an update to the collection of seismogenic mass movements that forms the basis of the Exotic Seismic Events Catalog (ESEC), doubling the number of events in the catalog from 121 to 242 while broadening the geographic distribution and range of event types. The ESEC is available online through the Incorporated Research Institutions for Seismology (IRIS) Searchable Product Depository (http://ds.iris.edu/spud/esec) or as a downloadable SQLite database from USGS ScienceBase. This update adds more instances of seismogenic landslides, debris flows, snow avalanches, outburst floods, and lahars as well as some new event types: two mine collapses, a submarine landslide, and a volcanic flank collapse. We also now incorporate infrasound detection. Whereas the first version of the catalog focused on mass movements located primarily in the Western United States and Canada, this update includes events from Europe and Pacific Islands. We only include events for which seismic data are openly available.

            We provide both basic seismic information (e.g., station detections on different frequency bands, seismic data location, etc.) and ancillary data such as geometric measurements, references, photographs, and satellite imagery. When available we use published values such as source location, drop height, runout distance, and volume, and when not documented, we estimate values from satellite imagery or photographs. Events are categorized in terms of the quality of the ancillary data, and we provide estimates of uncertainty on parameters such as location and volume. This update increases the availability of seismogenic mass movement data to the community to promote research that betters our understanding of event dynamics and improves methods for exotic event detection, classification, and characterization. Future updates could allow for the incorporation of other exotic event types like blasts and glacial events. The ESEC has a mechanism for community members to contribute events to the collection, so we encourage other researchers to join in the effort.

How to cite: Collins, E., Allstadt, K., Groult, C., Hibert, C., Malet, J.-P., Toney, L., Bessette-Kirton, E., Bahavar, M., and Van Fossen, M.: A major update to the Exotic Seismic Events Catalog: A compilation of seismogenic mass movements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3172, https://doi.org/10.5194/egusphere-egu22-3172, 2022.

The high-speed landslide may result in varying degrees of damage to downstream, such as dammed lake and subsequent dam failure and outburst flood. Nowadays, the seismic station is able to records the seismic signals of the entire process of landslide, provides valuable data for understanding the landslide process. Meanwhile, numerical simulation can also simulate the entire landslide process. However, it is seriously affected by variability of input parameters. To tackle the scientific challenge, we comprehensively analyzed the 2018 Baige landslide by firstly performing a joint time-frequency domain transform of the seismic signal using short-time fourier transform. We then reconstruct the land slide force history using empirical Green’s function. We used the constructed landslide force history inversion to calibrate the numerical input parameters using Discrete Element Method. Finally, we use the calibrated parameters to construct the whole process of landslide numerically. This study provides a potential way that improves the rationality and reliability of the landslide reconstruction using multi-method joint analysis.

How to cite: Cui, Y.: Link Between the Landslides and the Generated Seismic Signals: Dynamic Inversion and Numerical Simulation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3347, https://doi.org/10.5194/egusphere-egu22-3347, 2022.

Landslides are one of the most destructive geohazards due to their high mobility and long runout. Numerical prediction of their motion and deposit behavior is an effective method for quantitative hazard assessment. The numerical approaches can get more insight into the landslide dynamics such as displacement, momentum, and impact forces. One of the crucial aspects in the application of continuum models is how to choose an appropriate rheology law for the materials. However, this issue remains poorly addressed in the geo-hazards simulations community. In this study, two constitutive models are applied to interpret landslide materials that integrated within Smoothed Particle Hydrodynamics (SPH) scheme. The elastoplastic Drucker-Prager (DP) model from soil mechanics and its counterpart in fluid mechanics, the non-Newtonian rheological Drucker-Prager (RDP) model. The results indicate that both the soil mechanic model and the fluid model can reproduce key dynamic processes (e.g., acceleration, deceleration, rebound stages) and deposition morphology (e.g., deposit area and height), within different values of input parameters given equivalent burst simulations. There is no order of which is better than another, only the more appropriate model that depends on landslide characteristics.

How to cite: Li, S., Tang, H., Peng, C., Chen, X., Chen, H., and Chen, J.: Identifiability of rheological models in landslides modeling: a 3D SPH study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3351, https://doi.org/10.5194/egusphere-egu22-3351, 2022.

Among slope instabilities, prone-to-fall rock columns are known to exhibit features of strong vibration modes. Corresponding resonance frequencies can be tracked by seismic instrumentation for monitoring column’s mechanical and structural properties, as well as preventing any irreversible failures. In previous studies, superficial thermoelastic effects were supposedly driving resonance frequencies daily fluctuations, but not qualitatively neither quantitively evidenced[1]. Our work corroborates this hypothesis and quantifies the physical processes involved. We interpret daily variations of resonance frequencies in Les Arches study site (Vercors, French Prealps) [2] through a thermo-mechanical model based on finite-element method. The fluctuations of modelled resonance frequencies along day match closely the observed ones, reproducing the frequency increase at daytime of around 2%. In addition, our model allows explaining the various behaviors observed across study sites: the frequency response strongly depends on solar exposition, as well as timing and intensity of both radiative and convective heat fluxes. For future instrumentation, we hence recommend the deployment of pyranometers on rocky sites in order to accurately invert acousto-elastic parameters along time, thus tracking rock fracturing through acousto-elasticity monitoring.

How to cite: Guillemot, A., Baillet, L., Larose, E., and Bottelin, P.: Thermoelastic effects on resonance frequency of rock columns at daily scale, and modeling by acousto-elasticity , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3738, https://doi.org/10.5194/egusphere-egu22-3738, 2022.

In recent decades, loess landslides (clusters) induced by agricultural irrigation activities are accelerating the evolution of the loess tableland. However, how loess landslides (clusters) remodel the tableland has not been fully discussed in the previous studies. The lack of such research hinders people’s understanding of the role and mechanism of landslides in the geomorphological evolution of the modern Loess Plateau. In this paper, taking South Jingyang Tableland, Shaanxi Province, China as an example, through remote sensing interpretation, landslide monitoring (including remote sensing satellite monitoring, remote online monitoring and 3D laser scanning), electrical resistivity tomography (ERT) survey, field survey and sampling, geomorphic change detection (GCD) and numerical simulation, we try to conduct multidisciplinary study to reveal the dynamic evolution of landslides (groups) in South Jingyang Tableland and their influence on the tableland landform. This study revealed the temporal and spatial distribution of landslides in the study area and the dynamic change of the tableland edge. It is found that since 1974, the area of the tableland eroded by landslides has reached 221, 320 m², and the maximum retreat of the tableland edge is 139.6m and the maximum retreat rate is 2.97m/yr. The hydrogeological structure of five profiles was found out by means of ERT surveys, which provides important evidence for identifying the distribution and migration channels of the groundwater. We successfully monitored the processes of three landslides using multi-temporal data of terrestrial laser scanner (TLS) surveys and estimated the impact of these landslides on geomorphic changes. Using the on-line monitoring equipment installed at the top of L3 landslide, we realize that the tilt deformation process of L3 landslide top is not a single linear trend, but a complex deformation process. Finally, we use Massflow software to simulate the movement process of L3 landslide and reconstruct the likely stages of the L3 landslide development. On the one hand, this study provides a reference for the monitoring of landslides in loess tableland, on the other hand, it provides a scientific support for the study of interaction between loess landslides and geomorphic evolution. 

How to cite: Hu, S., Wang, X., and Wang, N.: Dynamic process, influence and triggering mechanism of remolding landform by landslide clusters in South Jingyang Tableland, China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3846, https://doi.org/10.5194/egusphere-egu22-3846, 2022.

Due to the construction of Three Gorges Dam, many old landslides have been revived with the impoundment of reservoir water, which pose great threaten to the lives of residents. Deformation observed in a reservoir landslide is the result of a complex multi-field and dynamic evolution process. In order to gain a comprehensive understanding of the deformation mechanism and evolution process of a reservoir landslide, multi-fields information need to be monitored. Taking Majiagou landslide located at Three Gorges Reservoir Region (TGRR) as an example, a Distributed fiber optic sensing (DFOS) based monitoring system was developed and implemented. The multi-fields information including seepage (rainfall, water level, pore water pressure), deformation and strain-stress variation were monitored in real time. Through analyzing the recorded data with grey correlation analysis method, the factors that trigger the deformation of Majiagou landslide were identified. By further linking the mechanical parameters of soil with seepage field, the deformation mechanism was revealed as well. This paper has provided an advanced multi-fields information monitoring and data interpretation method, which can be widely adopted in reservoir landslide study. 

How to cite: Zhang, L.: Triggers and deformation mechanism study of reservoir landslide through multi-fields information interpretation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4593, https://doi.org/10.5194/egusphere-egu22-4593, 2022.

Continuous, high resolution records provided by seismo-acoustic data are particularly valuable in studying processes that occur stochastically or in settings that are traditionally challenging to observe. The scarcity of data on these processes and their controls is largely responsible for a longstanding gap between event-scale observations and our ability to predict landscape or system behavior over larger scales. In this contribution, we discuss two ongoing studies in which seismo-acoustic methods are beginning to bridge this gap to enable new insights on the coupling between surface or near-surface processes and environmental controls.

Heavily instrumented small-scale studies (e.g., Marshall, 2018) have recently demonstrated that transmission of wind energy by plant roots plays an important role in the mechanics of soil production on hillslopes. At present, however, this process is entirely unconstrained at larger scales, though vegetation is known to be a primary driver of physical and chemical bedrock weathering. Seismic monitoring may open the door to studying how interactions between wind and vegetation impact rock weathering at scales relevant to human infrastructure, hazards and the global cycling of biogeochemical mass fluxes. Here we use data recorded by the US Transportable Array in Alaska to build on previous work (Dietze et al, 2015) exploring the role of trees in moderating the relationship between wind speeds and seismic activity. We examine rain-free, high-wind events across variations in vegetation cover and lithology to isolate the seismic signature of trees blowing in the wind and ask how their contributions to regional weathering budgets may evolve in a changing climate. 

In contrast, river-generated signals recorded by riverbank seismometers have been far more extensively studied, but remain challenging to interpret due to the reach- or regional-scale integration of many sources, processes and materials that are spatially heterogeneous and may covary in time. Recent advances in fiber optic distributed acoustic sensing (DAS) technology show promise for addressing some of these challenges by resolving signal sources over smaller scales. DAS systems provide continuous records of ground motion similar to large-N arrays of single-component accelerometers or geophones, but can be tens of kilometers in length with spatial resolution of meters and frequencies from millihertz to kilohertz. We present the first report on a DAS deployment in a river, focusing on meter-scale spatial variations in the signal recorded by a cable submerged along the thalweg of Clear Creek in Golden, CO. We leverage this novel dataset to reveal new insight into the relationship between the turbulence-generated seismo-acoustic frequency spectrum and river morphology.

References

Dietze, M., Burtin, A., Simard, S., & Hovius, N. (2015). The mediating role of trees - transfer and feedback mechanisms of wind-driven seismic activity. EGU General Assembly Conference Abstracts (p. 5118).

Marshall, J.A. (2018). From ice to trees, surprising insights into past and present processes that sculpt our earth. AGU Fall Meeting Abstracts (Vol. 2018, pp. EP44A-01).

How to cite: Roth, D., Zhang, M., Sahakian, V., Marshall, J., Jin, G., Titov, A., Siegfried, M., Masteller, C., and Jacobson, H.: Bridging the data gap: seismo-acoustic advances from ridgelines to rivers, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11066, https://doi.org/10.5194/egusphere-egu22-11066, 2022.

Landslides are one of the most dangerous natural hazards. Despite several efforts to study this phenomenon, there is still little clarity regarding dynamic processes associated with landslides. Recently, seismic signals are used to analyze the dynamic properties of landslides, because seismograms provide time-series recordings of sliding during run out. One of the important steps is to achieve a microseismic location. By analyzing the source, the events and the magnitude of the microseismic generated by landslides can indicate the risk of the slip surface. In previous studies, many people have outstanding performance at one aspect of microseismic localization. But those methods often need too many specialist operations and are difficult to achieve real-time and automatic operation. In this paper, we proposed the automatic microseismic location technology by CNN and applied it to landslide monitoring at Deda town, Tibet.

This automatic microseismic location technology is mainly divided into four steps: signal classification, first picking, phase connection, and hypocentral location. Both signal classification and first picking are based on CNN, which can automatically extract waveform features and avoid the tedious parameter setting from traditional detection technology. CNN is also a key point of intelligent processing of microseismic signals. In our study, different network architectures are used to improve the accuracy of these two tasks. Signal classification focuses on the difference between microseismic signals and noise, while time pick-up is the identification of the first starting point of microseismic signals after obtaining effective microseismic signals. In microseismic phase connection, we modify the “coincidence_trigger” function provided by Obspy(a Python library for seismic) to adapt to CNN predictions. Events identified by CNN were saved as waveform fragments containing multiple stations after phase connection. Meanwhile, timestamps were also saved. In the last step, the Newton method was adopted for source location, which proved to be very reliable in accuracy and stability through experimental comparison. By loading the time of microseismic events and station positions, we can achieve location. Since the number of stations detected by each microseismic event was not the same, dynamic processing was also carried out here. Therefore, the whole process of microseismic positioning only needs to input waveform data obtained by geophone and corresponding station information, without the operation of experts.

We applied this scheme to the field data are collected from Deda town, which is located in Tibet. There are faults on both sides of the mountain slopes. A total of 76 microseismic events were detected in 27 days by using our automatic microseismic location technology. All the events were located near the faults, and some events happened near the slip surface. But the magnitude of almost all of the events is less than 0 so we think these events are related to the landslides' energy release.

How to cite: Wang, Y., Qiu, Q., Zhang, W., Zhou, J., and Gao, P.: Monitoring of landslide affecting factors using automatic microseismic location technology in Deda town, Tibet, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4111, https://doi.org/10.5194/egusphere-egu22-4111, 2022.

Earthquakes–induced landslides generally provide abundant loose materials at hillslopes, possiblly triggering morphological reshaping processes at river channel and riverbed during the large flash flood hydrograph and bringing huge risk to downstream. Therefore, in a Wenchuan earthquake-affected catchment, the collected hydro-meteorological data and high-precision small Unmanned Aerial Vehicle (sUAV) data were used to quantificationally analyze channel evolution by a large flash flood event on 25^th and 26^th June, 2018. It was found that the stable riverbed structure formed by the coarsening layer appeared in the tenth year after the Wenchuan earthquake. In confined channel, the layer can protect the channel and resist the drastic change after the flash flood event with only small bed elevtion from 0.2 m to 2 m. Without the protection of the coarsening layer, the change could reach 6 m in unconfined channnel. Meanwhile, more materials with deposition volume of 753,108 m³ from tributaries were generally taken to main channel,and more intense erosion with the volume of 1.010⁷ m³ mostly occurred in the downstream of tributaries. It was noted that, in the cross-section, the increased channel width could lead to the significant change with the large volume of 35 m³. Additionally, conceptual model of the generalized channel response to large flash floods was provided during multi-stage periods after the Wenchuan earthquake. It determined the rebalance processes of channel evolution in the tenth year after the earthquake. This study will contribute to understanding the post-earthquake long-term channel evolutions and could provide decision-makers of assessing the mitigation strategies for higher-magnitude flood disasters triggered by channel change in earthquake-affected watershed.

How to cite: Jin, W.:  Channel evolution triggered by a large flash flood based on sUAV at an earthquake-affected catchment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4820, https://doi.org/10.5194/egusphere-egu22-4820, 2022.

Rapidly-rising jökulhlaups, or glacial outburst floods, are a phenomenon with a high potential for damage. The initiation and propagation processes of a rapidly-rising jökulhlaup are still not fully understood. Seismic monitoring can contribute to an improved process understanding, but comprehensive long-term seismic monitoring campaigns capturing the dynamics of a rapidly-rising jökulhlaup are rare. In 2012, we installed a seismic network at the marginal, ice-dammed lake of the A.P. Olsen Ice Cap in NE-Greenland. Episodic outbursts from the lake cause flood waves in the Zackenberg river, characterized by a rapid discharge increase within a few hours. We deployed industrial geophones (4.5 Hz) for the five on-ice stations. Two stations were designed as mini-arryas with three vertical sensors, and the remaining were equipped with three-component sensors. All sensors were sunk about 3 m into the ice. Our 6 months long seismic dataset comprises the whole fill-and-drain cycle of the ice-dammed lake in 2012 and includes one of the most destructive floods recorded so far for the Zackenberg river. Seismic event detection reveals periods of high seismicity during enhanced surface melting prior to the outburst flood. During the outburst itself the number of detected events dropped due to the elevated seismic noise level. Furthermore, different beamforming methods were tested to infer back azimuth changes during periods of elevated seismicity. We propose that the changes of back azimuth are related to the subglacial infiltration of water and evaluate the role of the ice-dammed lake within this context.

How to cite: BInder, D., Mertl, S., Citterio, M., Hillerup-Larsen, S., Langley, K., Walter, F., and Eibl, E. P. S.: On-ice seismicity of a rapidly-rising jökulhlaup cycle at the A.P. Olsen Ice Cap, NE-Greenland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5685, https://doi.org/10.5194/egusphere-egu22-5685, 2022.

A large landslide impacting a river may cause a multi-phase chain of hazards, comprising landslide-generated waves, inundation as a barrier lake develops upstream a landslide dam arising from rapid sediment deposition, and downstream flooding due to barrier lake outburst. Two major landslides (each of volume ~ 10⁷ m³) occurred successively on 10^th October and 3^rd November 2018 at Baige village, Tibet, China. Both landslides led to a natural dam that completely blocked the Jinsha River, along with a barrier lake filled with upstream river inflow. Although the first barrier lake breached naturally, a significant quantity of residual material from the first landslide dam was left behind without being eroded. After the second landslide occurred, a flood channel was urgently constructed to facilitate an artificial breach of the barrier lake as it formed. Here a computational investigation is presented of the hydro-sediment-morphodynamic processes of the Baige barrier lake, using a recent 2D double layer-averaged two-phase flow model. This is the first modelling study of the whole field and whole processes for the formation and outburst of a landslide-induced barrier lake as well as the resultant floods, without evoking presumptions on dam breach (which have prevailed for decades and bear much uncertainty). The computed results agree well with field observations in terms of landslide-generated waves, landslide dam morphology, stage and discharge hydrographs at the dam site and downstream flood hydrographs. The artificial flood channel is shown to be effective for alleviating downstream inundation. Relatively low inflow discharge and large initial landslide volume favour landslide dam and barrier lake formation, but delay the outburst and downstream flood. The present 2D double layer-averaged two-phase model holds great promise for assessing future landslide-induced multi-hazard chains in rivers, and informing mitigation and adaptation strategies.

How to cite: Li, J., Cao, Z., and Borthwick, A.: Hydro-sediment-morphodynamic process of landslide-induced barrier lake, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6348, https://doi.org/10.5194/egusphere-egu22-6348, 2022.

Glacier lake outburst floods (GLOFs) are a recurring hazard in Alpine environments and can occur in orogenies with steep topography and short subglacial flood paths. In Iceland, the topography can be more flat and longer distances can be travelled below the ice. There, the locally named jökulhlaups can propagate tens of kilometers before emerging to the surface. It is difficult to monitor remote places, especially water movement below extensive icecaps. Permanent monitoring stations on ice are difficult to maintain. Off the ice, the networks are too sparse. By contrast, temporarily installed seismic arrays provide a tool to locate the flood front and issue early warnings of the subsequent flood of areas below the glacier. This is possible, as the flood-associated seismic signals migrate significantly during the event.

Seismic array analysis is in general a suitable method to locate weak, distant seismic events and observe floods. However, locations of long-lasting, emergent signals such as tremor are difficult to analyze. Due to the lack of clear onsets, travel time estimates are usually not possible. The location depends on other methods and the azimuthal station coverage. From 30 September to 3 October 2015, a flood drained from the eastern Skaftá cauldron in Iceland, reaching a peak discharge of 3000 m³/s in the Skaftá river. The seismic data were analysed using classical fk-analysis (Eibl et al. 2020). Here we advance the seismic processing including Pyrocko-based modules cake and parstack, and matched-field processing that allows to mute for example dominant noise sources. This helps to address the following questions: Can we detect signals of the flood along the uppermost part of the flood path? Can we detect the seismic signal during the subglacial flood propagation on an array which is dominated by river noise? Can we enhance the characteristics when correlating in the time domain? Our goal is to refine the location of the seismic tremor to enhance our understanding on the tremor generation and flood propagation, but also to test whether the analysis is stable enough to apply it to other floods of similar systems e.g. Grimsvötn.

How to cite: Dietrich, T., Eibl, E. P. S., Binder, D., Lindner, F., and Heimann, S.: Advancing seismic processing of the Skaftá jökulhlaup in 2015, Iceland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7190, https://doi.org/10.5194/egusphere-egu22-7190, 2022.

Dispersion curve inversion is a key step of analyzing data from multichannel surface wave method (MASW) for investigating the shear wave velocity-depth (v_s-h) profile. The profile is usually simplified to be a stratification model consisting of horizontal and homogenous layers. Model parameters include the number (N) and thicknesses (h) of layers and shear wave velocity (v_s) in each layer. The N represents model complexity. The larger N value is, the more complex the model is. A model that is too complex is prone to overfitting. The opposite is true for too simple models that underfit. Mathematically, the dispersion curve inversion problem is ill-posed, that is, there are a number of stratification models of the v_s-h profile with different N, h, and v_s values resulting in identical, or at least, similar dispersion curves. Because the N value is usually unknown during the inversion, the model selection is necessary in which a model fitting well with data and proper model complexity is identified in a pool of competitive models.

Nonetheless, research is rare that addresses the model selection issue in dispersion curve inversion problems. Bayesian framework can be used in model selection by quantifying the uncertainty in the stratification model. In this study, critical issues of Bayesian frameworks for quantifying the uncertainty in stratification model selection are discussed, including Bayesian inversion with a variable or a fixed number of layers in stratification models. Then, the major difficulties in computing the posterior distribution and Bayesian model evidence for determining N are demonstrated and discussed, which are mainly caused by the high-dimensional and highly nonlinear likelihood function. Finally, the sensitivity of model complexity to the error associated with the dispersion curve is explored preliminarily.

How to cite: Wang, X., Cao, Z., and Du, W.: Bayesian inversion of shear wave velocity profile based on dispersion curve , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7701, https://doi.org/10.5194/egusphere-egu22-7701, 2022.

The failure of landslide dams is a sudden geological disaster, with its formation and failure greatly threatening the security of local people’s lives and property. In this research, we conducted 12 sets of model experiments, considering the influence of different angle of flume bed, dam heights, and downstream slopes on the process of overtopping breaching of noncohesive landslide dams. Based on these experimental results, we analyzed the characteristics of the longitudinal and transverse evolution, and outburst discharge of landslide dams in detail. At first, we divided the failure process of landslide dams into four stages, including initiation, headward erosion, downcutting erosion, and riverbed rebalancing. In addition, the quantitative analysis of breaching evolution model and the numerical method for simulating landslide dam failure due to overtopping has also been introduced in this research. This paper provides the research basis for the following two papers, which also provide a scientific reference for the prevention and mitigation of landslide dams.

How to cite: Zhu, X., Kang, Y., and Kong, J.: Experimental study on the failure modes and process of the overtopping breaching of noncohesive landslide dams, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8074, https://doi.org/10.5194/egusphere-egu22-8074, 2022.

In order to better understand the influence factors of the seismic response of the deep-seated unstable rock slope, we installed four high-sensitivity three-component integrated seismometers on Shidaguan slope (SDG slope) in Mao County, Sichuan Province, China. One of the seismometers was located at the stable part of SDG slope and at the highest elevation, while the other three were located in the deformation area of SDG slope. Nearly 100 sets of shallow source seismic data were acquired over a three-year period of seismic monitoring. Meanwhile, we carried out a detailed geological surveys by electrical resistivity tomography and drilling. Taking the monitoring point located at the stable part as a reference point, the peak acceleration obtained by the three seismometers located in the deformed area was compared to it. By this way, it is revealed that the seismic response of the reference point was the weakest, although it was at the highest elevation. The same phenomenon was obtained using the spectral ratio horizontal-to-vertical component of the seismic records (referred to here as HVSR). This is because that the fractured rock mass can act as a resonator, causing standing waves to develop in the broken rock mass. And the surface, as a free face, could show the strong ground shaking response. At the same time, we found that the seismic response was different for the three monitoring points in the deformed area of SDG slope. The seismic response of the deformed body with large thickness is smaller than that of the deformed body with small thickness. In order to analyse the reasons for the different amplification, we discussed the relationship between the amplification and the physical properties of rock mass. Rock mass with low resistivity and RQD caused seismic response amplification. However, this amplification was suppressed by that rock mass which exhibits viscoelasticity. The amplification of the ground shaking response would be influenced by the lithofacies difference degree in unstable areas, which should be taken into account when constructing buildings in landslide-prone mountainous areas.

How to cite: Cui, S., Pei, X., and Wang, H.: Seismic Response of A Large Deep-seated Rock Slope Revealed by Seismic Monitoring and Geological Surveys, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8259, https://doi.org/10.5194/egusphere-egu22-8259, 2022.

The Palu earthquake on September 28, 2018 with a magnitude of Mw 7.5 was one of the most destructive earthquakes in Indonesia. This earthquake also caused an underwater avalanche and caused a tsunami along the coast of the Palu bay. The source of the earthquake was the tectonic activity of the Palukoro fault. Until now, several research methods on earthquake precursors around the world have tried to find out whether there are long-term and short-term natural clues before the occurrence of a large and destructive earthquake. In this study, we examined the precursor anomaly of the earthquake in the Palukoro fault area using the least squares calculation method to obtain Vp/Vs by referring to the Wadati diagram. We used detailed earthquake catalog data from the nearest BMKG Station from the source, namely data on the arrival time of P and S waves from all earthquake events in the Palukoro Fault area from 2017 to 2017. 2020. The results show an anomaly pattern on the monthly Vp/Vs chart. The decrease in the value of Vp/Vs by an average of 6% occurred within a span of 9 months before the main Palu earthquake. Vp/Vs variations are an indication of the presence of tectonic stress and strain forces before an earthquake so that it can be used as an indication of earthquake precursors.

How to cite: Prayogo, A. S., Prasetyo, R. A., Perdana, Y. H., Martha, A. A., Yuliatmoko, R. S., Rohadi, S., Riama, N. F., and Triyono, R.: Vp/Vs Temporal Variation as Precursor Anomalies for the 2018 Palu Earthquake, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8573, https://doi.org/10.5194/egusphere-egu22-8573, 2022.

Earthquakes and landslides threaten the safety of human life and property. Fast and accurate location of earthquakes and landslides is critical to disaster mitigation and early warning of the secondary hazards. Hazards locating is a difficult issue in a remote region with sparse seismic network due to low resolution of the velocity structure model. Green’s functions from ambient seismic noises contain the information characterizing the anomalous velocity structure along the propagation path, and it can be used to calibrate effects due to the uncertainty of velocity structure, thereby improving the hazard location accuracy. In this study, we select the 2008 Wudu Ms5.5 earthquake, China, and a large landslide occurred in Nuugaatsiaq, Greenland, on 17 June 2017 as examples, to assess the accuracy of the relative location method based on Green’s functions from ambient seismic noises. The location result of the landslide is about 2.5 km away from the site given by satellite image, which is better than the result based on traditional location method, with a deviation up to ~17 km. Subsequently, we test some impact factors of the location accuracy via the 2008 Wudu earthquake, such as the epicentral distance of the reference stations and the networks with different sparseness. It shows that using a reference station within 30 km and about 4 remote stations for relocation, the relocation accuracy is about 5 km. Our results demonstrate that this algorithm can provide accurate location of earthquake and landslide with seismographic stations in global and regional networks, thus providing timely assistance to early warning of secondary hazards.

How to cite: Wang, S., Ni, S., Xie, J., and Zeng, X.: Accuracy of locating earthquakes and landslides in sparse seismic network with ambient noise Empirical Green’s Functions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9078, https://doi.org/10.5194/egusphere-egu22-9078, 2022.

  Bhopya K., Ghosal D., Verma S., Srivastav H., Verma S., Vikas

 The ongoing collision between the Indian and Eurasian plates has been accumulating strain along the Main Himalayan Thrust (MHT) causing the Sub-Himalaya highly vulnerable to Earthquakes. To examine seismic vulnerability in a hazard-prone area,  a complete understanding on its lithological properties like resonance frequency, shear wave velocity, bedrock depth, and thickness of overlying soft sediments is essential. As the study area spans from Madarsa Darul Quran to Mohand along the Himalayan Frontal Thrust (HFT) and lies in an earthquake-prone area, we record seismic ambient noise over twelve measuring points using a three-component portable seismograph (Tromino) with the natural frequency of 0.1 Hz. We carry out the HVSR (horizontal to the vertical spectral ratio) study on the recorded data using the Nakamura Method which is a technique for estimating the resonance frequency and site amplification caused by different stratigraphic units underlain by the top of the bedrock. The variable resonance frequency has been identified in this region in the range of 0.42 to 4.8 Hz, which indicates this region is prone to site amplification as overlain by Doon fan deposits. We invert the P-velocity (Vp), S-velocity (Vs), and density (ρ) by using Monte Carlo Inversion Method and identified three different stratigraphic units in this region. The top has a thickness of 3 meters with a mean Vs, Vp, and ρ as 218 m/s, 385 m/s, and, respectively. The second layer has a thickness of 6 meters with a mean Vs, Vp, and ρ of 406 m/s, 725 m/s, and 1.7 g/cm³, respectively. The bedrock depth in this region is 127 meters with a mean Vs, Vp, and ρ of 582 m/s, 1238 m/s, and 1.8 g/cm³ , respectively. This study will further help in response analysis up to a depth of bedrock.

How to cite: Bhopya Naik, K.: Site Characterization of Mohand Region along Himalayan Frontal Thrust (HFT) using passive HVSR method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12520, https://doi.org/10.5194/egusphere-egu22-12520, 2022.