3D Ground Motion Simulations of the 1755 Lisbon Earthquake
A recurrence of the 1755 Lisbon earthquake would be devastating for present-day Portugal. However, despite widespread research into the possible sources for the event, the associated fault(s) and magnitude of the earthquake are still uncertain. Previous simulation studies have used velocity models with relatively coarse resolution (Grandin et al., 2007) or stochastic modeling techniques that exclude potentially important wave propagation effects (Carvalho et al., 2004; Carvalho, Zonno, et al., 2008). Here, we use 3D physics-based simulation in the recent PRISM3D reference model for Iberia (Arroucau et al., 2021), that we validate against data from a 2018 M4.3 earthquake near Lisbon. We obtain an optimal fit to the 0-1 Hz strong motion recordings of the validation event using a geotechnical layer with a tapering depth of 350 m, a statistical distribution of small-scale heterogeneities with a standard deviation of 5 percent, and anelastic attenuation for S-waves using Qs = 0.1Vs (Vs in m/s). We then use the validated model to simulate 0-1 Hz wave propagation for 40+ plausible earthquake scenarios across proposed fault structures. Most of the single fault sources tested for the 1755 Lisbon earthquake inadequately replicate the observed Modified Mercalli Intensity (MMI) pattern from the event, while other scenarios violate reported tsunami arrivals or ground motion durations. However, we find that a Mw8.3 scenario event on the Guadalquivir Bank Fault generates MMI patterns most comparable to the reports. Moreover, the combined wavefield from a Mw8.4 event on the Marques de Pombal Fault with that of a (possibly triggered) Mw7.75 earthquake on the Tagus Abyssal Plain fault yields a satisfactory fit to the isoseismal data from the 1755 earthquake.
Session: Physics-Based Ground Motion Modeling [Poster Session]
Type: Poster
Room: Exhibit Hall
Date: 5/3/2024
Presentation Time: 08:00 AM (local time)
Presenting Author: Anupam Patel
Student Presenter: Yes
Additional Authors
Anupam Patel Presenting Author Corresponding Author apatel7716@sdsu.edu San Diego State University |
Kim Olsen kbolsen@sdsu.edu San Diego State University |
Te-Yang Yeh tyyeh316@gmail.com San Diego State University |
Susana Custódio susanacustodio@campus.ul.pt University of Lisbon |
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3D Ground Motion Simulations of the 1755 Lisbon Earthquake
Category
Physics-Based Ground Motion Modeling
Description