Ground Motion Characteristics of the 2020 M6.4 Indios, Puerto Rico Earthquake Sequence

Session: Early Results from the 2020 M6.4 Indios, Puerto Rico Earthquake Sequence [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The 2020 Mw6.4 southwest Puerto Rico earthquake and the productive foreshock and aftershock sequence provide an unprecedented dataset for characterizing regional ground motions in Puerto Rico. Following the M_w6.4 mainshock, the United States Geological Survey (USGS) Advanced National Seismic System (ANSS) and Puerto Rico Seismic Network (PRSN) deployed 6 rapid response portable aftershock monitoring stations. The first three portable stations recorded the largest aftershock (Mw5.9) at an epicentral distance of less than 30 km. The portable stations supplement the permanent monitoring of the PRSN and Puerto Rico Strong Motion Network (PRSMN) and provide numerous near-source strong ground motion observations from the earthquake sequence. An instrumental ground motion dataset of peak ground acceleration (PGA) and 5% damped pseudo-spectral acceleration (PSA) (periods 0.02 to 10 s) was computed for earthquakes in the sequence with magnitudes from 4.0 to 6.4. In this study, we evaluate GMMs for use in the update of the USGS Puerto Rico Seismic Hazard Model (PRSHM). Our goal is to determine how well ground motion models (GMMs) developed for Puerto Rico and other regions (e.g. global subduction zones and active shallow crustal regions) estimate the ground motion observations from shallow strike-slip fault earthquakes in the plate overriding the Muertos subduction zone. We compute total residuals and compare the probability density functions (PDFs), means and standard deviation of the observed and predicted ground motions using the probabilistic scoring method (log likelihood (LLH)). To test logic branches used in the previous seismic hazard model for Puerto Rico, we evaluate GMM performance as a function of source region and mechanism, magnitude and depth, and we investigate the influence of local site amplification. Results from this analysis will inform GMM selection and logic-tree weights for the update of the PRSHM.

Presenting Author: Daniel E. McNamara

Authors