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Nonergodic Seismic Hazard Assessment Based on Multi-cycle Earthquake Simulations

Description: 

Seismic hazard assessment (SHA) is crucial for mitigating earthquake-related risks, yet, the short duration of recorded seismicity, the sparse distribution of seismic stations, and the paucity of ground motion data for short epicentral distances challenge accurate SHA-estimation. Physics-based simulations offer a pathway of enhancing SHA reliability and to improve estimating epistemic uncertainties. Focusing on the seismically active region of the Gulf of Aqaba, the southern extension of the Dead Sea fault zone, we conduct earthquake-cycle simulations using the MCQsim engine. We run 132 different realisations to address the epistemic uncertainties governing the (a) friction coefficients (μ_s, μ_d, and D_c), (b) spatial connectivity of fault segments, (c) total number of segments, and (d) seismogenic depth. The resulting synthetic seismic catalogues, spanning over 10,000 years and magnitudes 3 ≤ M < 7.5 provide insights into recurrence rates, multi-segment ruptures, and complex source rupture characteristics.
In addition, we introduce a SHA methodology that integrates our simulated rupture scenarios with wave propagation modelling, using a discrete wavenumber method in horizontally layered medium. This approach efficiently models ground motions while incorporating nonergodic effects due to the simulated source characteristics of the synthetic catalogues. We compare our seismic-wave based intensity measures with non-parametric probabilistic estimates from the OpenQuake engine and from stochastic simulations using aspects of our simulated seismic catalogues (a and b-values of magnitude-frequency distribution, aspect ratios and faulting style of ruptures, seismogenic depths). Our results reveal a significant effect of fault-segment connectivity and seismogenic depth on peak ground velocities. We observe that tighter fault-segment continuity enhances the likelihood of multi-segment ruptures, leading to broader areas of higher peak ground velocities. Furthermore, our ability to constrain near-source ground motions using our synthetic ruptures provides critical insights for reliable seismic hazard applications.

Session: Recent Advances in Modeling Near-source Ground Motions for Seismic Hazard Applications [Poster]

Type: Poster

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Theodoros

Student Presenter: Yes

Invited Presentation: 

Poster Number: 52

Authors