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A New Empirical Probability Model for Surface Faulting Utilizing Width-rupture Ratio for Crustal Earthquakes

Models for the probability of surface rupture are used in probabilistic fault displacement hazard analyses (PFDHA). Most existing empirical modelsfor the probability of surface rupture (PSR) are based on a magnitude and style of faulting. An advantage of empirical models is that they need fewer assumptions about the depth distribution of the top of rupture of large-magnitude earthquakes, but a disadvantage is they do not account for the differences in the seismogenic thickness. Faultswith down-dip widths that are much thinner than average (e.g., 5 km), have a larger chance of surface rupture from small-magnitude earthquakes. Notable examples include the 2010 Mw 5.0 earthquake in Ecuador and the 2019 Mw 4.9 quake in France. Mammarella et al. (2024) proposed a PSR model utilizing a numerical approach that accounts for the seismogenic thickness and dip of the fault. This model has the advantage that it uses the fault-specific hypocenter depth distribution and seismogenic thickness, but it has the disadvantage that it assumes that the depth distribution of the top of rupture can be computed from the distribution of hypocenters from all magnitudes. In this study, we adopted an approach that uses the strengths of the empirical and numerical approaches. An empirical model is developed using the width-rupture ratio (WRR) in place of magnitude for the logistic regression. The WRR is the rupture width divided by the fault width. We compiled an empirical dataset of crustal earthquakes that occurred between 1970 and 2023 with a magnitude greater than 6. About half of the events have fault rupture information from finite-fault inversion. In cases where fault rupture widths were not available, we utilized the source scaling model from Huang et al. (2024) to estimate the rupture widths. By using the WRR, the proposed model accounts for the fault-specific seismogenic thickness and dip, but with empirical constraints on the PSR, avoiding the key assumptions in the numerical approach. This model successfully accommodates both large-and small-magnitude cases, facilitating fault-specific evaluations of the PSR.

Session: Testing, Testing 1 2 3: Appropriate Evaluation of New Seismic Hazard and Risk Models [Poster]

Type: Poster

Room: Exhibit Hall

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: JyunYan Huang

Student Presenter: No

Invited Presentation: 

Poster Number: 66

Additional Authors