Wirp, Sara Aniko, Gabriel, Alice‐Agnes, Ulrich, Thomas and Lorito, Stefano (2024) Dynamic Rupture Modeling of Large Earthquake Scenarios at the Hellenic Arc Toward Physics‐Based Seismic and Tsunami Hazard Assessment. Journal of Geophysical Research: Solid Earth, 129 (11). e2024JB029320. DOI 10.1029/2024JB029320.

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Abstract

The Mediterranean Hellenic Arc subduction zone (HASZ) has generated several 8 earthquakes and tsunamis. Seismic‐probabilistic tsunami hazard assessment typically utilizes uniform or stochastic earthquake models, which may not represent dynamic rupture and tsunami generation complexity. We present an ensemble of ten 3D dynamic rupture earthquake scenarios for the HASZ, utilizing a realistic slab geometry. Our simplest models use uniform along‐arc pre‐stresses or a single circular initial stress asperity. We then introduce progressively more complex models varying initial shear stress along‐arc, multiple asperities based on scale‐dependent critical slip weakening distance, and a most complex model blending all aforementioned heterogeneities. Thereby, regional initial conditions are constrained without relying on detailed geodetic locking models. Varying epicentral locations in the simplest, homogeneous model leads to different rupture speeds and moment magnitudes. We observe dynamic fault slip penetrating the shallow slip‐strengthening region and affecting seafloor uplift. Off‐fault plastic deformation can double vertical seafloor uplift. A single‐asperity model generates a 8 scenario resembling the 1303 Crete earthquake. Using along‐strike varying initial stresses results in 8.0–8.5 dynamic rupture scenarios with diverse slip rates and uplift patterns. The model with the most heterogeneous initial conditions yields a 7.5 scenario. Dynamic rupture complexity in prestress and fracture energy tends to lower earthquake magnitude but enhances tsunamigenic displacements. Our results offer insights into the dynamics of potential large Hellenic Arc megathrust earthquakes and may inform future physics‐based joint seismic and tsunami hazard assessments.

Plain Language Summary

The Mediterranean region around Greece and Crete is a hotspot for earthquakes and tsunamis. Here, the tectonic plates of Africa and Europe collide. History shows that this region has experienced damaging earthquakes. These earthquakes can cause tsunamis, sea waves that may lead to widespread destruction along coastlines. Our study aims to understand better how future earthquakes can be modeled. We use computer models to simulate different earthquake scenarios. Initially, we use simple conditions in our models, showing that if an earthquake propagated across the entire region, it could reach a moment magnitude of 9. When we move the earthquake's location within our model, the size and impact of the resulting earthquake change; some locations lead to larger seafloor displacements, which may cause more dangerous tsunamis. When introducing more complicated loading and fault strength conditions, the resulting earthquakes become smaller, consistent with historical observations. We also simulate how the fault‐surrounding rocks can deform during an earthquake. Such deformations can increase the uplift of the seafloor, increasing the potential for tsunamis. Our work shows that computer modeling can be a powerful tool for understanding earthquakes and tsunamis and better prepare for future events.

Key Points

We present the first 3D dynamic rupture earthquake scenarios for the Hellenic Arc megathrust
Epicenter location is a dominant factor controlling the occurrence and intensity of shallow slip and uplift
Dynamic rupture complexity tends to lower earthquake magnitude but enhances tsunamigenic displacement

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