A Multiscale Seismic Deployment with 463 Sensors Following the 2019 Ridgecrest Earthquake Sequence in Eastern CA

Amir A. Allam, Rufus D. Catchings, Jamison H. Steidl, Elizabeth M. Berg, Nathan Downey, Yehuda Ben-Zion, Mark R. Goldman, Joanne H. Chan, Coyn J. Criley, Daniel Langermann, Adrian T. McEvilly, Ziqiang Ma, & Daniel D. Mongovin

Published August 15, 2019, SCEC Contribution #9756, 2019 SCEC Annual Meeting Poster #255

The 2019 Ridgecrest Earthquake sequence in the Eastern California Shear Zone includes the M6.4 and M7.1 July 4-5 events and numerous aftershocks that extend to the north towards the Owens Valley and to the south towards the Garlock fault. The July 4 M6.4 event had aftershocks on nearly orthogonal faults, with both left- and right-lateral slip. The M7.1 earthquake on July 4th re-ruptured the right-lateral fault and dramatically extended the surface rupture close to the Coso geothermal field to the north and close to the Garlock fault to the south. To gain insight into the faulting processes involved in this complex earthquake sequence, we deployed a multiscale 463-instrument temporary array of three-component seismometers for one month, beginning on July 6th. The deployment includes a 42-station regional-scale grid, with 10-km spacing, four fault-normal arrays (100-m spacing) that cross the M7.1 surface rupture, four fault-normal arrays across the nearby Garlock fault, and one array across the primary left-lateral rupture of the M6.4 event. The arrays were designed to answer specific questions: what is the nature of the barrier between the NW end of the M6.4 event and the hypocenter of the M7.1 earthquake? Why did the M6.4 event produce aftershocks on orthogonal segments? What is the width and intensity of the mainshock’s damage zone, and how does it vary along strike? What is the nature of the newly excited seismicity on the formerly quiescent Garlock fault? The aftershock waveforms and ambient noise recorded by this deployment will be used to derive detailed velocity models and spatial spatio-temporal seismicity patterns that will address these and other questions.

Citation
Allam, A. A., Catchings, R. D., Steidl, J. H., Berg, E. M., Downey, N., Ben-Zion, Y., Goldman, M. R., Chan, J. H., Criley, C. J., Langermann, D., McEvilly, A. T., Ma, Z., & Mongovin, D. D. (2019, 08). A Multiscale Seismic Deployment with 463 Sensors Following the 2019 Ridgecrest Earthquake Sequence in Eastern CA. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes