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Correlated Noise in Source Time Functions: A Method to Generate Realistic High Frequency Earthquake Sources

Description: 

We perform broadband ground motion simulations with a new methodology to create kinematic sources that account for small-scale rupture heterogeneity, whereby we focus especially on realistic source time functions (STF). Our broadband kinematic source generator begins with Von Karman patterns to create future slip distributions from amplitude and geometry source parameters. Using Mai and Beroza (2002) relationships, findings of Thingbaijam and Mai (2016) on slip distribution parameterization, and slip-constrained hypocentre locations (Mai et al., 2005), our rupture generator creates dynamically self-consistent kinematic source realizations. We then apply the methodology of Liu et al (2006) to perturb rupture onset times and the local rise times to define the main parameters of the rupture propagation.

Using a regularized Yoffe as STF, our method describes the local slip evolution at each subfault. As marked in previous studies, the regularized Yoffe function well replicates, in time and frequency, dynamic STF‘s. However, the regularized Yoffe function generates spectral notches in the high-frequency amplitude spectra. Those notches render the high-frequency source implementation unrealistic, affecting also the total moment rate function and far-field ground motions. To create more plausible rupture realization based on a Yoffe STF, we propose adding correlated noise. The correlated noise follows a 1D Von Karman random field. The parameters to define this random field are estimated by comparing STF from dynamic rupture simulations and regularized Yoffe function, using 21 dynamic simulations (from Mai et al., 2018). Using our rupture generator, we compute the ground motion at different locations, reproducing the mean and standard deviation from GMM in different intensity measures in simulations of M 6.0-7.0. Additionally, our rupture generator allows us to integrate low-frequency inversions and stochastically complement the high frequency of the original source. In summary, our improved pseudo-dynamic kinematic rupture generator produces realistic high frequency sources essential for seismic hazard analysis.

Session: Physics-Based Ground Motion Modeling - II

Type: Oral

Date: 5/3/2024

Presentation Time: 11:30 AM (local time)

Presenting Author: David

Student Presenter: No

Invited Presentation: 

Authors