Broadband Ground Motion Simulations for a Türkiye-like Earthquake “Doublet” on the Hayward and Calaveras Faults
Description:
The occurrence and impact of the February 2023 earthquake doublet in Türkiye, where an Mw 7.8 event was followed roughly 9 hours later by an Mw 7.5 event on an adjacent fault, begs the question: What would be the impact of such a sequence in California? Here, we consider a comparable doublet scenario on the Hayward and Calaveras faults in the San Francisco Bay region. The first phase of this work involves characterizing the fault ruptures and simulating the ground motions. We base the fault locations and orientations on the 2023 USGS National Seismic Hazard Model. Both faults have creeping zones, so we use a simple scheme in our kinematic rupture generator to taper the coseismic slip in the upper 10 km based on the ratio of long-term creep rate to long-term fault slip rate along each section. The resulting magnitudes are Mw 7.15 for the 95-km Hayward rupture and Mw 7.16 for the 100-km Calaveras rupture. We compute broadband motions using a combination of deterministic and stochastic approaches for the lower- and higher-frequency components, respectively. Our deterministic calculations use the USGS 3D San Francisco Bay region velocity model (v21.1) with a minimum shear velocity of 400 m/s, and our stochastic simulations use a 1D reference model with Vs30-based site-specific adjustments using period-dependent factors. We saved waveforms on a 1.2 km by 1.2 km grid of points, and we extracted PGA, PGV, and spectral accelerations at periods of 0.3, 1.0, and 3.0 s to produce scenario ShakeMaps. Additionally, we save ground acceleration time histories at other sites corresponding to locations of mid- and high-rise buildings for later use in structural response analysis. Comparison of the simulated motions with empirical ground-motion models (GMMs) are generally favorable; however, noticeable differences exist due to rupture directivity and basin response effects. Furthermore, simulated motions along the creeping fault sections are generally smaller than GMM predictions. The second phase of this work is ongoing and involves analyzing potential impacts on the built environment using the simulated ground motions.
Session: 3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling - I
Type: Oral
Date: 5/2/2024
Presentation Time: 08:30 AM (local time)
Presenting Author: Robert
Student Presenter: No
Invited Presentation:
Authors
Robert Graves Presenting Author Corresponding Author rwgraves@usgs.gov U.S. Geological Survey |
Jia Wang-Connelly Jia.Wang-Connelly@CalOES.ca.gov California Office of Emergency Services |
Eric Thompson emthompson@usgs.gov U.S. Geological Survey |
Vincent Quitoriano vinceq@contractor.usgs.gov U.S. Geological Survey |
David Wald wald@usgs.gov U.S. Geological Survey |
Kevin Milner kmilner@usc.edu University of Southern California |
Selim Gunay selimgunay@berkeley.edu University of California, Berkeley |
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Broadband Ground Motion Simulations for a Türkiye-like Earthquake “Doublet” on the Hayward and Calaveras Faults
Category
3D Wavefield Simulations: From Seismic Imaging to Ground Motion Modelling