Strain-estimated ground motions of recent earthquakes in California

Noha Farghal, & Annemarie S. Baltay

Published August 15, 2019, SCEC Contribution #9795, 2019 SCEC Annual Meeting Poster #249

We utilize strain data from the Plate Boundary Observatory (PBO) borehole strainmeter network to estimate peak ground velocities (PGVs) and earthquake magnitudes from dynamic strains recorded during recent earthquakes in California. We show that strain data has good potential to complement seismometer data usage in earthquake early warning (EEW) applications, as strainmeters exhibit true broadband response, do not clip in response to intense ground motions, and tens of borehole strainmeters are already deployed along the Pacific-North America plate boundary, some of which have outputs available in real-time. We present a proof-of-concept for the use of empirically-derived equations to estimate earthquake moment magnitudes (from peak dynamic strains), and PGVs (from measured shear strain), for fifteen Bay Area and Southern California earthquakes of M 4.0-7.1 that occurred from 2007 to 2019, including the July 2019 Ridgecrest Earthquake Sequence. We compare the temporal magnitude evolution of our empirical strain-based magnitude scale from several stations closest to the earthquake locations to similar magnitude information from ShakeAlert, the U.S. West Coast EEW system which currently uses only seismic data. We also compare our shear strain PGV estimates to seismic PGVs from ShakeMap. Finally, we highlight issues with strain measurements that need to be addressed before this data is incorporated into any EEW system.

Key Words
strain, strainmeter, PGV, shear

Farghal, N., & Baltay, A. S. (2019, 08). Strain-estimated ground motions of recent earthquakes in California. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Ridgecrest Earthquakes