High resolution seismic waveform migration location method and its applications to induced seismicity

Abstract

Locating seismic events is a central task for earthquake monitoring. Compared to arrival-based location methods, waveform-based location methods do not require picking phase arrivals and are more suitable for locating seismic events with noisy waveforms. Among waveform-based location methods, one category is to stack different attributes of P and S waveforms around arrival times corresponding to potential event locations and origin times. At correct event location and origin time, the stacking value will be maximized. In this study, to obtain high-resolution location image, we improve the waveform-based location method by applying hybrid multiplicative imaging condition to characteristic functions of seismic waveforms. In our new stacking method, stations are divided into groups and characteristic functions of seismic waveforms at stations in the same group are first summed and then multiplied among groups, which can largely eliminate the cumulative effect of noise in the summation process and thus improve the resolution of location images. We test the new method and compare it with the other three stacking methods using both synthetic and real datasets that are related to induced seismicity by oil/gas production. The results show that the new stacking method can provide higher-resolution location images.

Passive Seismic Structure Imaging of a Coal Mine by Ambient Noise Seismic Interferometry on a Dense Array

“…Selection of only one day of recordings is dictated by the inherent temporal and spatial variations of noise sources causing destructive interferences for potential reflection events (i.e., the probability of this destructive interference is increased when longer data are used for stacking). We start our processing from applying waveform migration and tomoDD methods (Zhang and Thurber, 2003;Miao et al, 2021) toward locating all ambient-noise events recorded by our array. Eventually, we detected 576 high SNR events which are are mostly concentrated on the northwest part of the array.…”