Near-source ground motions for complex-geometry scenario earthquakes

Abstract

This dissertation work concerns the effects of earthquake source geometry on nearfield ground-motions. Through numerical simulations, we investigate the following topics: (1) the effects of listricity on near-field ground motions, and (2) possible ground shaking levels in the Gulf of Aqaba region through multiple earthquake scenarios characterized by several fault segments rupturing either separately or jointly. Listric faults are defined as curved faults in which dip decreases with depth, resulting in a concave upwards profile. The profiles in this study are created by applying a specific shape function: by varying the initial dip and the degree of listricity, we create an ensemble of listric faults. We then define heterogeneous rupture speeds and slip distributions to generate a variety of kinematic source models. Finally, we compare them in terms of peak ground velocities to ground motion prediction equations and find two general features: (1) as listricity increases, the PGVs decrease on the footwall and increase on the hanging-wall; (2) constructive interference of seismic waves emanated from the listric fault causes PGVs over two times higher than those observed for the planar fault. The Gulf of Aqaba region has seen rapid growth in recent years, mainly fuelled by the increasing population, tourism, and investments in national projects. Such projects include the 26.500 km2 city of NEOM, backed by a 500 billion dollar investment by the Saudi Investment Fund and the King Salman bridge across the Straits of Tiran. The recency of the seismic network in the area provides limited information; moreover, no large earthquakes have occurred since its installation. The corresponding lack of data presents engineers with a severe knowledge gap. To contribute to closing this gap, we compute synthetic earthquake ground motions to study the consequences of large magnitude (Mw ~ 7.2) scenario seismic events. To this end, we conduct kinematic rupture simulations that mimic dynamic source behavior including both single- and multi-segment ruptures. Our simulations show higher ground velocities than predicted by GMPEs for the Straits of Tiran and lower for the NEOM area.