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Application of the G-Fast Algorithm to Rapidly Estimate Earthquake Ground Motion Using GNSS Slip Models on the Cascadia Megathrust

Session: Advances in Understanding Near-Field Ground Motions: Observation, Prediction and Application I

Type: Oral

Date: 4/22/2021

Presentation Time: 10:15 AM Pacific

Description: 

Ground motion prediction equations (GMPE) play a critical role in probabilistic seismic hazard analysis. In this study, we highlight our method to rapidly determine GMPE using finite-fault (FF) rupture models derived from near-field Global Navigation Satellite System (GNSS) stations. The geodetic approach using GNSS data is applicable for real-time monitoring of moderate to large destructive earthquakes. We use the Geodetic First Approximation of Size and Time (G-FAST) algorithm (Crowell et al., 2016) to compute FF rupture models using a synthetic dataset of 1300 simulated earthquake ruptures (M7.5-M9.5) distributed throughout the Cascadia subduction zone margin. We investigate whether the spatial distribution of slip from geodetic models can accurately constrain ground motion. Fault location and geometry are determined from either the geodetic CMT solution on a single rectangular fault plane or from a prescribed subduction zone megathrust geometry with two rectangular fault segments. We estimate horizontal ground motion amplitudes from the FF solutions using the Next Generation Attenuation Model (NGA) presented in Chiou and Youngs (2008). The geodetic derived ground motion predictions highlight a useful way to calculate Modified Mercalli Intensity (MMI) values within a few minutes of the mainshock rupture. We highlight uncertainties between the predicted versus observed ground motion. Geodetic algorithms such as G-FAST add important value in timely and robust estimation of earthquake magnitude and ground motion.

Presenting Author: Kevin Kwong

Student Presenter: No

Authors