Accuracy and Precision of Earthquake Location Programs: Insights from a Synthetic Controlled Experiment based on 2019 Ridgecrest Earthquake Sequence

Yifan Yu, William L. Ellsworth, & Gregory C. Beroza

Published September 8, 2024, SCEC Contribution #13716, 2024 SCEC Annual Meeting Poster #021

Earthquake location programs use a variety of algorithms to overcome the challenges posed by incomplete knowledge of complex Earth structures, making them essential for accurate hypocenter determination. However, evaluating their reliability in estimating locations and uncertainties is difficult, as the suitable ground truth datasets with known event locations are rare. This study assesses eight earthquake location programs (Hypoinverse, VELEST, NonLinLoc, NonLinLoc_SSST, HypoSVI, HypoDD, Growclust, and XCORLOC) through a controlled synthetic experiment based on the 2019 Ridgecrest earthquake sequence. We construct a travel time dataset using the Fast-Marching Method and a 3D velocity model extracted from the Community Velocity Model, incorporating a von Karman perturbation to represent small-scale heterogeneity and including elevation effects. The picking errors, phase availabilities, and phase outliers are introduced to mimic obstacles encountered in seismic network monitoring scenarios. The location results from the same travel time dataset and 1D velocity structure reveal the superior accuracy and precision of relative location methods compared to absolute location methods and validate the significance of compensating 1D velocity structure approximation by either direct corrections or cancellation. We also evaluate the uncertainty quantification of each program and suggest that most of the programs underestimate the errors. This computational workflow is easily expanded to other regions or different scales.

We acknowledge the help from Dr. Guoqing Lin, Anthony Lomax, Zach Ross, and Daniel Trugman for providing guidance running the location programs.

Key Words
Earthquake Location

Citation
Yu, Y., Ellsworth, W. L., & Beroza, G. C. (2024, 09). Accuracy and Precision of Earthquake Location Programs: Insights from a Synthetic Controlled Experiment based on 2019 Ridgecrest Earthquake Sequence. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology