NH4.2 | Physical and data-driven models for seismic risk assessments toward disaster reduction
EDI
Physical and data-driven models for seismic risk assessments toward disaster reduction
Co-organized by SM7/TS3
Convener: Antonella Peresan | Co-conveners: Alik Ismail-Zadeh, Katerina Orfanogiannaki, Katalin GribovszkiECSECS, Elisa Varini
Orals
| Wed, 26 Apr, 08:30–10:15 (CEST)
 
Room 2.17
Posters on site
| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)
 
Hall X4
Posters virtual
| Attendance Wed, 26 Apr, 16:15–18:00 (CEST)
 
vHall NH
Orals |
Wed, 08:30
Wed, 16:15
Wed, 16:15
Earthquake disaster mitigation involves different elements, concerning identification, assessment and reduction of earthquake risk. Each element has various aspects: a) analysis of hazards (e.g. physical description of ground shaking) and its impact on built and natural environment, b) vulnerability and exposure to hazards and capacity building and resilience, c) long-term preparedness and post-event response. Due to the broad range of earthquake disaster mitigation various seismic hazard/risk models are developed at different time scales and by different methods, heterogeneous observations are used and multi-disciplinary information is acquired.
We welcome contributions about different types of seismic hazards research and assessments, both methodological and practical, and their applications to disaster risk reduction in terms of physical and social vulnerability, capacity and resilience.
This session aims to tackle theoretical and implementation issues, as well as aspects of communication and science policy, which are all essential elements towards effective disasters mitigation, and involve:
⇒ the development of physical/statistical models for the different earthquake risk components (hazard, exposure, vulnerability), including novel methods for data collection and processing (e.g. statistical machine learning analysis)
⇒ earthquake hazard and risk estimation at different time and space scales, verifying their performance against observations (including unconventional seismological observations);
⇒ time-dependent seismic hazard and risk assessments (including contribution of aftershocks), and post-event information (early warning, alerts) for emergency management;
⇒ earthquake-induced cascading effects (e.g. landslides, tsunamis, etc.) and multi-risk assessment (e.g. earthquake plus flooding).
The interdisciplinary session promotes knowledge exchange, sharing best practices and experience gained by using different methods, providing this way opportunities to advance our understanding of disaster risk in "all its dimensions of vulnerability, capacity, exposure of persons and assets, hazard characteristics and the environment", while simultaneously highlighting existing gaps and future research directions.

Orals: Wed, 26 Apr | Room 2.17

Chairpersons: Antonella Peresan, Elisa Varini, Alik Ismail-Zadeh
08:30–08:35
Seismic hazard assessment
08:35–08:45
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EGU23-346
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NH4.2
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ECS
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Virtual presentation
Chen-Yu Nieh and Szu-Yun Lin

Earthquake disasters may not only damage buildings but significantly influence the standard of living due to the impacts on critical infrastructure such as lifeline systems. This study focuses on the seismic risk and resilience of the natural gas network and the cascading effects. We analyze the risk of failure in the mid/low-pressure pipelines under a major earthquake scenario and evaluate the impacts on systemic service levels considering the secondary disasters of earthquakes. In this study, repair rate, R.R., is applied to evaluate the failure of natural gas pipeline. With the R.R. of pipelines and ground motion parameters, e.g., PGA and PGD, the failure probability of the pipeline can be derived by Poisson distribution. By overlay analysis with seismic parameters from Taiwan Earthquake Loss Estimation System (TELES) and the GIS data of the natural gas network, the number of damaged pipelines, the number of affected users, and the closure probability of valves can be estimated through Monte Carlo simulation. The service level and resilience of the system can be further assessed. In addition to the impacts on the natural gas system, the leaking gas can also cause a potential risk of worsening post-earthquake fire. On the other hand, the repairment of damaged pipelines may affect the surrounding traffic. These should be considered during the restoration process. This study proposes a risk assessment approach for the natural gas pipeline subjected to earthquakes considering not only the physical damage of the pipeline but the closure of valves, the risk of worsening post-earthquake fire, and the sequential influence on the traffic. The proposed framework was applied to the natural gas system in Tainan, Taiwan, as the case study. This study assesses the earthquake hazard risk of natural gas pipelines from the perspective of system functionality and community resilience. Decision-makers can plan appropriate disaster mitigation strategies based on the analysis results.

How to cite: Nieh, C.-Y. and Lin, S.-Y.: Seismic Risk Assessment of Natural Gas Networks considering Cascading Effects, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-346, https://doi.org/10.5194/egusphere-egu23-346, 2023.

08:45–08:55
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EGU23-11178
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NH4.2
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On-site presentation
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Konstantinos Leptokaropoulos

Seismic processes can be often time dependent at different time scales. Earthquake interactions (e.g., static and dynamic stress changes), anthropogenic activities (e.g., mining, fluid injection, hydrocarbon exploitation) fluid dynamics (e.g., in geothermal fields and volcanic areas) and periodic phenomena (e.g., earth and ocean tides) result to changes in frequency and magnitude distribution of earthquakes. These changes apply in a wide range of time scales from seconds to decades and their evaluation is vital, for seismic hazard assessment in the vicinity of urban and industrial areas. In addition, such estimates can be used in industrial sites to facilitate production optimization, and they also may offer better insights for the underlying physical mechanisms of seismogenesis (e.g., stress transfer, fluid migration pathways and pore pressure, chemical alteration and frictional properties in depth).

SHAPE (Seismic HAzard Parameters Evaluation), is an open source toolbox, based on MATLAB, developed within the SERA (Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe) Project, and is available for use by seismologists and other scientists and engineers in related fields. SHAPE probabilistically estimates the time-dependent, source components of seismic hazard, namely the magnitude distribution and the seismic activity rates, expressed jointly as changes in the exceedance probability of a given magnitude within a predefined period. Alternatively, the changes of the mean return period of a given magnitude is evaluated in moving time windows. Four different magnitude distribution models are included (unbounded and truncated Gutenberg-Richter law and non-parametric kernel). Interactive parameter selection and data filtering routines are also incorporated in the package.

The presentation will cover the capabilities of SHAPE and a demonstration of selected examples from published and ongoing case studies:

  • Mining induced seismicity at Rudna Mine, Poland.
  • Seismicity triggered by water reservoir impoundment in Song Trahn 2 artificial lake, Vietnam.
  • Tidal triggering of microseismicity recorded by an ocean bottom seismometer network in the equatorial mid-Atlantic ridge.

The SHAPE package is developed in two standalone versions (an interactive Graphical User Interface version and a function) as well an online version, integrated in the Thematic Core Service Anthropogenic Hazards (TCS-AH) of the European Plate Observing System (EPOS). The standalone versions can be downloaded for free from a public repository.

How to cite: Leptokaropoulos, K.: Time-dependent Seismic Hazard Parameters Evaluation with SHAPE MATLAB Package, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11178, https://doi.org/10.5194/egusphere-egu23-11178, 2023.

08:55–09:05
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EGU23-12982
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NH4.2
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Highlight
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On-site presentation
Marisol Monterrubio-Velasco, Marta Pienkowska, and Josep de la Puente

Urgent Computing (UC) refers to the use of High-Performance Computing (HPC) and High-Performance Data Analytics (HPDA) during or immediately after emergency situations. It typically combines complex edge-to-end workflows with capacity computing, where multiple model realizations are required (to account for input and model uncertainties) under strict time-to-solution constraints. Enabling urgent HPC for emergency scenarios, such as earthquakes, can prove valuable towards resilience and relief. The temporal horizon for UC typically ranges from minutes to a few hours.

A novel  HPC-based urgent seismic simulation workflow, the Urgent Computing Integrated Services for Earthquakes (UCIS4EQ),  focuses on short-time reports of the consequences of moderate to large earthquakes. UCIS4EQ automatically prepares and manages sets of physics-based deterministic simulations to rapidly obtain synthetic results. Based on pre-computed and on-the-fly simulations, UCIS4EQ delivers estimates of relevant ground motion parameters, such as peak ground velocity, peak ground acceleration, or shaking duration, with very high spatial resolution.  The physics-based engine includes pre-trained Machine Learning (ML) models fed with pre-computed simulation databases and r full 3D simulations on demand, providing results in minutes and hours, respectively.  The combined results, when well-calibrated, could complement GMPEs for rapid hazard assessment

To demonstrate the potential of UC in seismology, we show the capability of the UCIS4EQ workflow both for the ML predictions and for deterministic simulations in the South Iceland Seismic Zone (SISZ) and the Reykjanes Peninsula Oblique Rift (RPOR). The largest historic earthquakes in Iceland have occurred within these zones and have exceeded magnitude 7. The study region  (63.5°-64.5°N, 20°-22°W) is where the largely sinistral East-West transform motion across the tectonic margin is taken up by a complex array of near-vertical and parallel North-South oriented dextral transform faults in SISZ-RPOR. The high seismic activity in the area widely affects the capital Reykjavik, the most populous city in Iceland. 

This work has been supported by the ChEESE and eFlows4HPC projects.

How to cite: Monterrubio-Velasco, M., Pienkowska, M., and de la Puente, J.: UCIS4EQ applied to the South Iceland region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12982, https://doi.org/10.5194/egusphere-egu23-12982, 2023.

09:05–09:15
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EGU23-7780
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NH4.2
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On-site presentation
Why do seismic hazard models predict higher shaking than that observed historically?
(withdrawn)
Molly Gallahue, Leah Salditch, Madeleine Lucas, James Neely, Seth Stein, Norman Abrahamson, and Susan Hough
09:15–09:20
Earthquake and cascading risks assessment
09:20–09:30
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EGU23-17572
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NH4.2
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ECS
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On-site presentation
Hany Hassan and Antonella Peresan

A tsunami induced by a shallow offshore earthquake of magnitude Mw=6.7 occurred south of the island of Crete (Greece) on May 2nd, 2020. The initial tsunami alert message (TAMs) received by the Egyptian National Tsunami Warning Focal Point for Egypt (i.e. Egyptian National Research Institute of Astronomy and Geophysics-NRIAG) was issued by the Geodynamic Institute of the National Observatory of Athens (NOA-HLNTWC), and was based on preliminary, rather inaccurate hypocenter and magnitude estimates. About 36 minutes after the earthquake, a follow-up message with an increased tsunami warning level was issued; the updated warning was motivated by a significant revision of earthquake source parameters estimates. The later message, however, was issued without taking into account the available observations from sea-level data.

In this study we investigate the effectiveness and usefulness of the TAM messages received by NRIAG for the coastal areas of Egypt (including the issue time and the source parameters on which the messages are based), by cross-checking them against observed and modelled seismological and sea level data. Based on results from the critical review of the tsunami warning messages, disseminated by NOA-HLNTWC and other TSPs in the Eastern Mediterranean Sea and received by NRIAG (which is a TWFP for Egypt), a comprehensive revision of the tsunami early warning system tools and procedures seems urgently needed in the region. The active involvement of countries along the southern coast of the Mediterranean turns out to be crucial, as the analysis shows that tsunami warning can only be efficient with international cooperation on data (seismic and sea level) and procedures.

How to cite: Hassan, H. and Peresan, A.: Assessing Effectiveness of the Tsunami Alert Messages Issued by NEAMTWS-TSPs: a case study from May 2nd, 2020 South Crete Earthquake Tsunami alert for Egypt, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17572, https://doi.org/10.5194/egusphere-egu23-17572, 2023.

09:30–09:40
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EGU23-1710
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NH4.2
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On-site presentation
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Anastasia Nekrasova, Vladimir Kossobokov, and Ekaterina Podolskaia

Seismic hazard assessment (SHA) and associated risks (SRs) require necessarily an adequate understanding of earthquake distribution in magnitude, space, and time at regional scale. The Neo-Deterministic Seismic Hazard Assessment (NDSHA) is the innovative multi-disciplinary scenario-physics-based approach for reliable evaluation of seismic hazard and risks, which have been developed to overcome evident shortcomings of the outdated and very often wrong Probabilistic Seismic Hazard Analysis (PSHA). The NDSHA applications in many countries worldwide (Panza et al., 2021) pass intensive testing by instrumental and historical evidence, as well as by realistic modelling of scenario earthquakes. NDSHA results confirm reliable and effective input for mitigating object-oriented SRs. We applied two agents of the NDSHA synergy, i.e. Unified Scaling Law for Earthquakes (USLE) and anisotropic propagation of seismic effect, to evaluate SRs for the railway infrastructure in the Lake Baikal region.

USLE states that the logarithm of expected annual number of earthquakes of magnitude M or larger in an area of linear dimension L follows within the magnitude range [M– , M+] the relationship log N(M, L) = A + B×(5 − M) + C×log L, where A, B and C are constants. Naturally, A and B are analogous to the a- and b-values of the classical Gutenberg-Richter relationship (G-RR), while C compliments to G-RR with an estimate of local fractal dimension of earthquake epicentres allowing for realistic rescaling seismic hazard to the size of exposure at risk. USLE implies that the maximum magnitude MX expected with p% chance in T years can be obtained from N(MX, L) = p%, then used for estimating ground shaking effect.

We used as essentials (i) macroseismic intensity scale that provides a robust estimate for realistic modelling of maximal potential ground shaking in assessment of regional seismic hazard and associated risks and (ii) anisotropic propagation of seismic effect that is evidently following, in most cases of large earthquakes, dominant direction of active faults nearby epicentre and apply these to the earthquake catalogue compiled at the Baikal Division of the Geophysical Survey, Federal Research Centre of the Russian Academy of Sciences (http://www.seis-bykl.ru/), Active Faults of Eurasia Database (http://neotec.ginras.ru/database.html) and data on railroads from the OpenStreetMap project (https://www.openstreetmap.org).

We present the SRs for railway lines, hubs and tunnels in the Lake Baikal region based on the maps of maximum macroseismic intensity expected in a period of 50 years with a probability of 10%, 5% and 1% (Nekrasova&Kossobokov, 2022) and different model vulnerability functions attributed to the exposed infrastructure elements of different kind.

The study is carried on in the framework of the Russian State Task of Scientific Research Works of IEPT RAS and IPE RAS.

 

References

Nekrasova A, Kossobokov V (2022) Seismic risk assessment for the infrastructure in the regions adjacent to the Russian Federation Baikal–Amur Mainline based on the Unified Scaling Law for Earthquakes. Natural Hazards, https://doi.org/10.1007/s11069-022-05750-9

Panza G, Kossobokov V, De Vivo B, Laor E (Eds) (2021) Earthquakes and Sustainable Infrastructure: neo-deterministic (NDSHA) approach guarantees prevention rather than cure. Elsevier, xxv, 672 p. https://doi.org/10.1016/C2020-0-00052-6

How to cite: Nekrasova, A., Kossobokov, V., and Podolskaia, E.: Seismic risk assessment of the Lake Baikal railway infrastructure based on Unified Scaling Law for Earthquakes and anisotropic seismic impact, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1710, https://doi.org/10.5194/egusphere-egu23-1710, 2023.

09:40–09:50
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EGU23-15665
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NH4.2
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ECS
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Highlight
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On-site presentation
Dragos Toma-Danila and Iuliana Armas

Bucharest can be considered Europe's most endangered capitals due to earthquakes. Intermediate-depth events occurring in the Vrancea Area, with magnitudes greater than 7, can significantly affect Bucharest. In the XXth century, the city experienced two major damaging earthquakes: in 1940 and 1977. But lessons were not fully learned. The number of vulnerable buildings is highly considerable: over 30% are built before 1963 (of which 22%, before 1941). The increased complexity of our society and new challenges among which climate change, pandemics and globalization are new problems to address. In this context, multi-hazard and multi-risk analyses are more than ever necessary.

If the 1977 earthquake generated numerous research with the aim of quantifying the vulnerability of the building stock and improving seismic design, social vulnerability to seismic risk was addressed only after 2000 by the Risk Research Center, University of Bucharest, based on a repeated spatial vulnerability assessment at city-level. Applying the additive approach of the multi-criteria and decision-making analysis in GIS, the spatial social vulnerability was identified by indicators of social and economic metrics, among which social capital and inequality, distance analysis, and on empirical taxonomies: gender, age, social status, ethnicity, type of housing, etc., based on 1992, 2002 and 2011 census data. Calibrating results using remote sensing and social surveys, helped identify vulnerable hotspots and the dynamic of social differences at city level.  

Superimposed on these detailed vulnerability maps for Bucharest based on computed vulnerability indices, a critical decision-making tool for safe access routes in the emergency intervention was developed supported by large sets of traffic and network data, time-dependent analysis, and seismic loss-estimations. This tool, called Network-Risk, uses a state-of-the-art network analysis methodology embedded in GIS, with the potential of integrating live traffic data.

All these topics will be continued in the recently started PARATUS European Project, where Bucharest is a case-study area. In our presentation, we talk about the new data and procedures that we consider for seismic risk assessment (among which new exposure data from a recent census or retrieved from remote sensing missions using deep learning, new data collecting procedures, vulnerability models and city-scale ShakeMap development) and which are the challenges – especially in the nowadays context.

How to cite: Toma-Danila, D. and Armas, I.: PARATUS case-study Bucharest. A new seismic risk assessment model., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15665, https://doi.org/10.5194/egusphere-egu23-15665, 2023.

09:50–10:10
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EGU23-12679
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NH4.2
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solicited
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Highlight
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On-site presentation
Massimiliano Pittore, Juan Camilo Gomez Zapata, Christian Geiß, Piero Campalani, and Kathrin Renner

Exposure modelling is a critical factor in the assessment of risk from natural hazards. Athough often its role has been overshadowed by other risk components (most notably, hazard), an efficient estimation of exposure is key to improve confidence in impact analysis and forecasting and ultimately support decision makers to improve risk mitigation activities. This is particularly relevant in urban and metropolitan areas, where the density and complexity of the interplay between population, socio-economical assets and infrastructure is likely to foster non-linear risk amplification, possibly due to cascading phenomena. 
In the last decade several innovative methodological approaches have been proposed, building upon statistical modelling, exploiting heterogeneous data from remote sensing, and integrating machine learning techniques in order to improve understanding, formal description and representation of exposure in a wide range of applications. These activities have been originally developed within the community of seismic risk, and later increasingly extended to other natural hazards, acknowledging the need for a more general and flexible approach to exposure modelling in the context of multi-hazard and multi-risk applications.
This is ever more important considering also the ongoing convergence of Disaster Risk Reduction (DRR) and Climate Change Adaptation (CCA) in the broader context of Comprehensive Risk Management (CRM).
In this contribute we aim at providing an overview of the most recent advances that the authors have proposed in the field, outline the current challenge and perspectives in the field of exposure modelling, and draw a tentative roadmap for the next future. 

How to cite: Pittore, M., Gomez Zapata, J. C., Geiß, C., Campalani, P., and Renner, K.: Advancing exposure modelling from seismic risk to multi-hazard analysis in urban and metropolitan areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12679, https://doi.org/10.5194/egusphere-egu23-12679, 2023.

10:10–10:15

Posters on site: Wed, 26 Apr, 16:15–18:00 | Hall X4

Chairpersons: Alik Ismail-Zadeh, Katalin Gribovszki, Antonella Peresan
Earthquake clustering in hazard assessment
X4.62
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EGU23-1897
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NH4.2
Elisa Varini, George Molchan, and Antonella Peresan

We investigate earthquake clustering, a prominent feature of seismic catalogs, in terms of distribution of the number of triggered events as described by a branching process (Kagan and Knopoff, Phys. Earth Planet. Inter., 1976; Saichev et al., Pure Appl. Geophys., 2005, and references therein). According to recent literature (e.g. Shebalin et al., Geophys. J. Int., 2020, and references therein), the productivity of a magnitude m event is defined as the number of triggered events of magnitude above m-Δ, where Δ is a positive default value. For a magnitude m event, we distinguish between the number of its direct descendants and the total number of its descendants, denoted respectively by the random variables v and V, both depending on Δ. Empirical analysis often testifies in favor of the identity of the type of distribution of both quantities (v and V) associated with the main event, and hypothetically is exponential. The testing or substantiation of this hypothesis is important for modeling seismicity and presents a serious challenge for seismic statistics.

In the standard Epidemic Type Aftershock Sequence – ETAS – model (Ogata, Ann. Inst. Stat. Math., 1998), the distribution of v is Poissonian. Therefore we consider the general ETAS model adapted to any distribution of v and prove that the branching structure of the model excludes the possibility of having a common distribution type (for example, Poisson or exponential) for both v and V at once  (Molchan et al., Geophys. J. Int., 2022). The second theoretical result relates to the behaviour of the tails of the productivity distribution. We show that there is a fundamental difference in tail behavior of the V-distributions for general-type clusters and for clusters with a dominant initial magnitude:  the tail is heavy in the former case and light in the latter. The real data display similar behavior. Theoretical conclusions are also illustrated through the analysis of a synthetic earthquake catalog.

How to cite: Varini, E., Molchan, G., and Peresan, A.: Theoretical analysis of the productivity of seismic events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1897, https://doi.org/10.5194/egusphere-egu23-1897, 2023.

X4.63
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EGU23-17573
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NH4.2
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ECS
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Anastasiia Agaian and Anastasia Nekrasova

The study aims to get new insights in the evolving clustering of seismicity to be the preconditions for the further effective use of the improved SHA technique in earthquake-prone regions. Discrete Mathematical Analysis DMA (Gvishiani et al. 2008; Agayan et al. 2018) is a series of algorithms for analyzing discrete data, united by a common formal basis, which is fuzzy models of discrete analogs of the fundamental concepts of classical mathematical analysis: limits, continuity, smoothness, connectivity, monotonicity, extremum, etc. In this study, the use of DMA is associated with clustering: it has to select clusters of discrete observations according to a given criterion (classification of discrete observations belonging to one of the clusters) (Gordon, 1981). The results of application of the Discrete Perfect Sets DPS topological filtering algorithm to seismic events in the Baikal area are presented. For the purpose of our analysis, we consider the Baikal Division of the Geophysical Survey, Federal Research Center of the Russian Academy of Sciences, BDRGS (2020) catalogue data. Specifically the epicenters for magnitudes equal to or more than 2.6 (energy class K≥8.6, accepted in catalogue homepage) for the period 1989–2018 within 48–58°N and 99–122°E. The study was carried out as part of the Russian Federation State task of Scientific Research Works on "Seismic hazard assessment, development and testing of earthquake prediction methods"(No. 0143-2019-0006).

How to cite: Agaian, A. and Nekrasova, A.: Spatial clustering of seismic events analysis using the Discrete Perfect Sets (DPS)algorithm: Pribaikalye, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17573, https://doi.org/10.5194/egusphere-egu23-17573, 2023.

X4.64
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EGU23-1870
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NH4.2
Antonella Peresan, Mohammad Talebi, and Mehdi Zare

The features of earthquake clusters in two contactional domains, located in Northeastern Italy and North-Central Iran, have been investigated. The tectonic and seismicity of the two study areas, namely the Alps-Dinarides junction and the Alborz regions, are controlled by the convergence between the African and Arabian plates and the Eurasia plate. Both regions are characterized by a rather complex structural setting, mainly including reverse and strike-slip faulting systems, and by moderate to high seismic activity.

The nearest-neighbor approach has been used for the identification of the earthquake clusters in the space-time-energy domain. This approach permits for a data-driven identification of clusters so that, within multi-event clusters, the features of secondary and higher orders dependent events can be explored. The investigation of seismicity in Northeastern Italy is based on bulletins compiled at the National Institute of Oceanography and Applied Geophysics (OGS) in 1977-2018, while in North-Central Iran the dataset was extracted from the catalog compiled by the Iranian Seismological Center (IRSC) for the period 1996-2022. According to preliminary analysis of the used earthquake catalogs, two corresponding regions have been identified, where a satisfactory completeness level is assessed for events with magnitude greater than 2.0. Robust values of the scaling parameters, namely the b-value and the fractal dimension of epicenters, have also been computed and are used to calculate the nearest-neighbor distances and to identify the earthquake clusters.

The results obtained in the two regions confirm that the complexity of clusters structure depends on the tectonic, structural, and geophysical properties of the area. Moreover, the complexity measures, borrowed from network theory (i.e. the Centralization and Outdegree indexes), consistently capture the complexity of the identified clusters. Besides, in both investigated regions, the results allowed us identifying two macro-areas, which are characterized by different clustering features, namely: high complexity indexes,, which indicate simple (burst-like) structure of clusters, and low complexity indexes, corresponding to complex multi-level (swarm-like) structure of clusters. Specifically, we found that "swarm-like" (high complexity) sequences are prevalent along the thrust faulting Alpine and Central-West Alborz systems, whereas "burst-like" (low complexity) sequences prevail along the strike-slip Dinaric and Central-East Alborz domains.

How to cite: Peresan, A., Talebi, M., and Zare, M.: Characterization of Earthquake Clustering in Contractional Regions, based on Nearest-Neighbor distances and Network Analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1870, https://doi.org/10.5194/egusphere-egu23-1870, 2023.

Seismic hazard at national and local scale
X4.65
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EGU23-13313
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NH4.2
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ECS
Kendra Johnson, Thomas Chartier, Marco Pagani, Yesica Perez, Vladimir Guzmán, Maria Betania Roque Quezada, and Catalina Yepes Estrada

The Dominican Republic, situated on eastern Hispaniola Island in the Caribbean, is subject to moderate to high seismic hazard mostly controlled by oblique convergence at the Caribbean/North American plate boundary. Offshore of the island, the North Hispaniola Trench (NHT) and Los Muertos Trough (LMT) subduction-like structures accommodate shortening, while crustal faults both onshore and offshore also take up some deformation. Historically, the Dominican Republic’s large cities, as well as those in Haiti (which shares Hispaniola) have been damaged by earthquakes, the worst of which required the population to relocate (e.g. the 1562 Santiago de los Caballeros earthquake).  Given the elevated hazard, the Dominican Republic was selected to engage in the Global Earthquake Model (GEM) Foundation coordinated USAID-funded “Training and Communication for Earthquake Risk Assessment” project, which aimed to improve earthquake risk assessment capacity in Latin American cities. This project and the collaborations that emerged were the basis for developing a seismic hazard model for the Dominican Republic.

The seismic hazard model is implemented in the OpenQuake Engine, and mostly uses GEM’s model-building tools and state-of-practice. Two main datasets were used for the seismic source characterization: a homogenized earthquake catalogue that benefited from local seismicity records contributed by the Servicio Geológico Nacional (SGN) and Universidad Autónoma de Santo Domingo (UASD), and an active faults database that combines GEM’s global database and one compiled by SGN during recent seismic hazard projects. Together, these datasets were used to constrain seismic source geometries and rates for active shallow crustal earthquakes, subduction interfaces and subduction-like thrusts, and intraslab earthquakes. Active shallow crustal sources were characterized as a combination of fault ruptures and off-fault (distributed) smoothed seismicity. Fault rupture geometries were pre-defined using the Seismic Hazard and Earthquake Rate In Fault Systems (SHERIFS) method, which allows multi-fault ruptures, incorporating epistemic uncertainty in the magnitude scaling relationship (and thus maximum magnitude), portion of earthquakes modelled on and off faults, and slip rates of two major fault systems. Additional uncertainty was considered in the assumptions used to smooth distributed seismicity rates. The NHT and LMT were also modelled using the SHERIFS method, while the other subduction sources were modelled using GEM’s more standard approaches (i.e. a single fault with complex geometry for the interface and pre-defined ruptures constrained to the intraslab volume). Two end-member magnitude frequency distributions were used for the Puerto Rico Trench interface: one assigning more moment to large magnitudes, and one obeying the Gutenberg-Richter relationship. For intraslab sources, epistemic uncertainty was captured in the assumptions for smoothing rupture probabilities according to past earthquakes. The ground motion characterization relied on residual analyses performed in past GEM projects, but replacing outdated GMPEs on subduction sources with more recent counterparts.

Hazard results generally reinforce former perceptions. In Santiago de los Caballeros, PGA reaches ~1g for 2% probability of exceedance in 50 years, controlled by the Septentrional Fault, while in the capital (Santo Domingo) PGA of ~0.5g is impacted by all tectonic region types, and includes contributions from moderate magnitude earthquakes (Mw 5-6).

How to cite: Johnson, K., Chartier, T., Pagani, M., Perez, Y., Guzmán, V., Betania Roque Quezada, M., and Yepes Estrada, C.: PSHA for the Dominican Republic, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13313, https://doi.org/10.5194/egusphere-egu23-13313, 2023.

X4.66
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EGU23-17432
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NH4.2
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ECS
Aybige Akinci, Claudia Pandolfi, Matteo Taroni, Giusy Lavecchia, and Rita De Nardis

In any probabilistic seismic hazard analysis (PSHA), the computation of earthquake forecasting models is a fundamental step. A widely used approach is the smoothed seismicity, which uses seismic catalogs to produce earthquake forecasts in time, space, and magnitude. Early smoothed seismicity models, called fixed smoothing, used spatially uniform smoothing parameters such that the kernels were invariant to spatial variations in seismicity rate. However, recently developed adaptive smoothing methods spatially adapt the smoothing parameters according to the earthquake density. All these fixed or adaptive methods are mainly used in regions with complex seismic source characterization since they do not rely on geological, tectonic, or geodetic information, and they overcome the difficulties in characterizing and segmenting complex geological set-ups. Nevertheless, the standard smoothed seismicity approaches may not properly present the seismicity rates for complex seismotectonic areas.

In this study, we propose an innovative 3D approach for fixed and adaptive smoothed seismicity methods that can be advantageously exploited in all contexts with available well-constrained 3D fault models derived from high-quality seismic catalogs. This approach presents a 3D kernel in the algorithm to smooth the location of earthquakes on a spatial grid by considering the earthquake's depth and spatial coordinates. This allows the use of a three-dimensional grid built on a 3D fault model to represent the depth variations of the structure and also provide the rupture parameters. We tested our method with the Adriatic Basal Thrust (ABT) in eastern Central Italy, a regional active contractional structure with a well-constrained 3D fault model and a related high-quality location catalog.

The eastern Central Italy seismotectonic set-up is characterized by contractional active regional thrusts, such as ABT, representing the outermost and still active front of the Apennine fold-and-thrust belt and by coaxial extensional faults observable along the axis of the Apennine Chain. This complex framework shows different kinematic seismogenic sources overlapping at different depths and represents a perfect case study to test the 3D smoothed seismicity with fixed and adaptive methods. The 3D seismicity model was constructed for the ABT using a detailed catalog with completeness magnitude Mc ≥ 1.4 opportunely selected to identify ABT activity and declustered for the time-independent (Poisson) model.   We then applied the 3D kernel algorithm with the adaptive and fixed smoothed seismicity approaches to calculate the M ≥ 4.5 ABT earthquake rates. We also include a series of geological information regarding the depth, the fault strike, the dip angle, the seismogenic layers depth, and the rake of the slip direction that can be used for the seismic hazard analysis in the region. Finally, we presented the impact of the 3D smoothed seismicity model on PSHA in central Eastern Italy using OpenQuake software.

How to cite: Akinci, A., Pandolfi, C., Taroni, M., Lavecchia, G., and De Nardis, R.: Constructing a 3D Smoothed Seismicity Model for the Seismic Hazard Assessment in the Adriatic Thrust Zone, Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17432, https://doi.org/10.5194/egusphere-egu23-17432, 2023.

X4.67
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EGU23-10882
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NH4.2
Byeong Seok Ahn, Tae-Seob Kang, and Hyun Jae Yoo

Site effects caused by unconsolidated sediments laying on the bedrock amplify or attenuate ground motions propagated to the surface. Site effect is unique site-by-site, and thus, makes analyzing actual attenuation characteristics of ground motions difficult. In the southern Korean Peninsula, 17 seismic stations administered by KMA and KIGAM were equipped with a pair of accelerometers; one is installed at the surface, and the other at the borehole (namely SB station). We estimate the site response functions of the stations using ambient noise data. First, the horizontal-to-vertical spectral ratios (HVSR) of the stations were calculated. Then, calibration ratios to adjust the amplitude of HVSR to that of surface-to-borehole spectral ratio (SBSR) were estimated and applied to the amplitude of HVSR. These amplitude-corrected HVSRs are used as the site response function to correct linear site effects in ground motions. To deconvolve the site effect of ground motions, we designed linear zero-phase FIR filters based on the site response functions. Then we divided the spectral amplitudes of the ground motions by the frequency response of the FIR filter. For the SB stations, site response functions of ten stations were obtained, and ground-motion data of 39 events with ML > 2 were corrected using these site response functions. In the result, the peak ground motion (PGA) of corrected ground motions at the surface was reduced by 20-76% on average compared to raw ground motions. Comparing ground motions of the borehole and surface sensors, the corrected PGA of the surface was 1.8-4.9 times bigger than the raw PGA of the borehole. For the whole surface stations of 176, the site-response functions of 75 stations were estimated, and ground-motion data of 210 events with ML > 3 were corrected by their site-response functions. We found that surface ground motions are deamplified to the level of borehole ground motions through the site effect correction.

How to cite: Ahn, B. S., Kang, T.-S., and Yoo, H. J.: Deconvolution of site effects in ground-motion using site response function derived from HVSR method, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10882, https://doi.org/10.5194/egusphere-egu23-10882, 2023.

Earthquake risk: from exposure to impact
X4.68
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EGU23-17557
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NH4.2
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ECS
Alexandros Michailidis

This work investigates how the uncertainty in the soil parameters influences the frequency content of the earthquake accelerograms that are expected to occur at a specific site. To this end, the Clough-Penzien power-spectrum is parametrized using random variables to describe the stochastic soil parameters and an artificial set of accelerograms is generated using the Spectral-Representation method. Subsequently, the equations of motion of a single degree-of-freedom oscillator are solved numerically for each earthquake scenario and the response spectrum is extracted. By comparing the derived response spectrum with the one obtained from considering deterministic soil parameters, useful conclusions are drawn pertaining to structural design and analysis.

How to cite: Michailidis, A.: Uncertainty quantification of seismic structural response due to randomness in the soil properties, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17557, https://doi.org/10.5194/egusphere-egu23-17557, 2023.

X4.69
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EGU23-15231
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NH4.2
A census-derived building aggregated exposure model (AEM) for Japan
(withdrawn)
Simantini Shinde, Cecilia Nievas, Kevin Fleming, Laurens Jozef Nicolaas Oostwegel, Tara Evaz Zadeh, and Danijel Schorlemmer
X4.70
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EGU23-7690
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NH4.2
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ECS
Yilong Li, Zhenguo Zhang, Wenqiang Wang, and Danhua Xin

At present, seismic prediction technology is still not available. Scientific decision-making and rescue after an earthquake are the main means of mitigating the immediate consequences of earthquake disasters. If earthquake emergency response level, fatalities, and economic losses can be estimated rapidly and quantitatively, this estimation will provide timely, scientific guidance to government organizations and relevant institutions to make decisions on earthquake relief and resource allocation, thereby reducing potential losses and more conducive to the implementation of social activities such as post-disaster reconstruction and reinsurance. To achieve this goal, a rapid earthquake disaster loss estimation method is proposed herein, based on a combination of physical simulations and empirical statistics. The numerical approach was based on the three-dimensional curved grid finite difference method (CG-FDM), implemented for graphics processing unit (GPU) architecture, to rapidly simulate the entire physical propagation of the seismic wavefield from the source to the surface for a large-scale natural earthquake over a 3-D undulating terrain. Simulated seismic intensity data were used as input for the earthquake disaster loss estimation model to estimate the fatality, economic loss, and emergency response level. The estimation model was developed by regression analysis of the data on human loss, economic loss, intensity distribution, and population exposure from the composite damaging earthquake catalog. We used the 2021 Ms 6.4 Yangbi earthquake as a study case to provide estimated results. The number of fatalities estimated by the model was in the range of 0–10 (five expected fatalities). The most probable economic loss range was 1–10 billion RMB (the expected economic loss was 4.862 billion RMB). Therefore, Level IV earthquake emergency response plan should have been activated (the government actually overestimated the damage and activated a Level II emergency response plan). The local government finally reported three deaths and 3.32 billion RMB economic losses during this earthquake, which is consistent with the model predictions.

How to cite: Li, Y., Zhang, Z., Wang, W., and Xin, D.: Rapid Estimation of Earthquake Disaster Loss Based on Physical Simulation and Empirical Statistics—A Case Study of the 2021 Yangbi Earthquake, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7690, https://doi.org/10.5194/egusphere-egu23-7690, 2023.

Posters virtual: Wed, 26 Apr, 16:15–18:00 | vHall NH

Chairpersons: Elisa Varini, Katerina Orfanogiannaki
vNH.13
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EGU23-5879
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NH4.2
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ECS
Maitreyi, Chandrani Singh, Arun Singh, Mita Uthaman, Abhisek Dutta, Gaurav Kumar, and Arun Kumar Dubey

The b-value in the frequency-magnitude relation is one of the fundamental seismological parameters to define an assemblage of earthquakes. This study focuses on the use of b-value as a precursor to know the chances of occurrence of major earthquake events in Sikkim and adjoining Himalayas. A catalogue containing 9192 earthquakes (M ≥ 0.30) recorded across Nepal, Sikkim and Bhutan Himalayas during 1980-2022 is considered for the present study. The study area has been divided into three blocks encompassing Nepal, Sikkim and Bhutan segments and the b-values are computed. The results show variations in b-value across these three blocks which might be associated with the differential stress pattern across the regions. Further, we map the spatial variation of frequency-magnitude distribution by dividing the entire region into 0.1⁰ x 0.1⁰ grids. The grids with less than 30 earthquake events are excluded to ensure the reliability of our results. The results suggest that the entire segment belongs to a high stressed region. The lowest b-values are mostly observed in Sikkim and western Nepal, reflecting the possible zones of future earthquakes.

How to cite: Maitreyi, , Singh, C., Singh, A., Uthaman, M., Dutta, A., Kumar, G., and Kumar Dubey, A.: b- value mapping in Sikkim and adjoining Himalayas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5879, https://doi.org/10.5194/egusphere-egu23-5879, 2023.