An Automatic Phase Picker for Local Earthquakes with Predetermined Locations: Combining a Signal‐to‐Noise Ratio Detector with 1D Velocity Model Inversion

Zefeng Li, & Zhigang Peng

Published August 24, 2016, SCEC Contribution #6547

We present a simple method to pick additional P and S phases for local earthquakes with predetermined locations. Different from conventional characteristic function techniques, our method incorporates 1D velocity inversion into phase picking. It first predicts phase arrivals using initial velocity models and available event locations and then applies a detector function to search genuine phase arrivals around the initial predictions. Using the newest searched phase arrivals (picks), the velocity models are updated accordingly and then used to predict more accurate arrival times. Such a procedure can be iterated multi- ple times, during which both phase picking and velocity model are improved. We perform a synthetic test with a 1D velocity model. The resulting phase picks are consistent with true arriv- als, and true velocity models can be well recovered. Another test with real data recorded by the Anza Seismic Network in southern California shows that the resulting velocity models agree with the average Southern California Earthquake Center community models in this region. Out of 23,932 event–station pairs, 23,770 P picks and 21,935 S picks are ob- tained from this method. After four iterations, 90% of our P picks and 80% of our S picks have differences within 0.15 s from the phase picks of the Southern California Earthquake catalog. Given its simplicity and efficiency and ability to pro- duce robust P and S picks and 1D velocity models, the tech- nique is particularly suitable for a wide range of seismological research in which phase picks at additional stations and/or re- fined 1D velocity models are needed.

Key Words
Phase picking, Velocity Inversion

Citation
Li, Z., & Peng, Z. (2016). An Automatic Phase Picker for Local Earthquakes with Predetermined Locations: Combining a Signal‐to‐Noise Ratio Detector with 1D Velocity Model Inversion. Seismological Research Letters, 87(6), 1397-1405. doi: 10.1785/0220160027. http://geophysics.eas.gatech.edu/people/zli/PSIRpicker/PSIRpicker.html

Related Projects & Working Groups
Seismology