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Exploring the Spatial Correlation of Ground Motions During the 2019 Ridgecrest Earthquake Sequence

Description: 

We consider patterns in spatial correlations of recorded ground motions during the 2019 Ridgecrest earthquake sequence. Ground motions are known to vary widely from their median expected values, yet their spatial distributions are not entirely random. To accurately estimate hazard across distributed systems we must understand how ground motions correlate over a range of inter-station distances. The spatial correlation of ground motions has been widely studied, but data are lacking at short interstation distances. The 2019 Ridgecrest earthquake sequence presents a unique opportunity to examine spatial correlations at a range of interstation distances. Following the Ridgecrest earthquake, the permanent seismic network (Hauksson et al., 2020) was augmented with tens of strong motion and broadband sensors that were installed for several months (Cochran et al., 2020). Additionally, nodal seismic sensors were deployed for two-months at 585 recording sites with station spacing as low as 100 m (Catchings et al, 2020). Using the gmprocess software package (Hearne et al., 2019), we determine peak ground velocity (PGV) and acceleration (PGA) for 16,416 recordings from 120 earthquakes (M3.3-M5.0). For each event and station pair, we compute the correlation of the within event residuals determined from the fit to the median ground motion model of Boore et al. (2014), considering local site conditions (Thompson 2020). We use the typical assumption that all locations separated by a given distance will have the same correlation and fit the results with an exponential semivariogram model (e.g., Baker and Chen, 2020). We find a nominal correlation distance (i.e., range measured from the fit to the exponential model) for PGA and PGV of approximately 20 km, similar to what has been found for other regions. We also explore whether the correlation distances vary spatially by determining correlation distances for sets of stations distributed around the Ridgecrest source rupture.

Session: How Well Can We Predict Broadband Site-Specific Ground Motion and Its Spatial Variability So Far? - II

Type: Oral

Date: 5/1/2024

Presentation Time: 10:45 AM (local time)

Presenting Author: Elizabeth

Student Presenter: No

Invited Presentation: 

Authors