A Single‐Station Method for Seismic Detection of Slow Earthquakes: Applications to Japan and the Mexican Subduction Zone

Abstract

AbstractSlow‐earthquake signals are generally smaller than or comparable to noise levels at almost all seismological frequencies. Comprehensive detection of these events requires continuous waveforms from many stations, but such data are not always available, even in regions with high slow‐earthquake activity. We therefore need a simple and stable detection method that is also applicable to regions with sparse seismic observation networks to truly advance our understanding of slow earthquakes. Here, we utilize the proportionality between the seismic energy rate and seismic moment rate of slow earthquakes to develop a slow‐earthquake detection method using broadband waveforms from a single station. We introduce the method and estimate its performance using continuous waveform data in Japan. The new method only detects events when the tectonic tremors occur near the station, for example, 89.1% of the detections have corresponding tectonic tremor activities within 60 km, which suggests that the false‐positive rate is low. We then apply it to waveform data from the Guerrero, Oaxaca, and Jalisco regions along the Mexican subduction zone. The results for the Guerrero and Oaxaca regions are largely consistent with the geodetic and seismological results from a previous study. We also detect many events in the Jalisco region using a permanent station and provide the first seismological report of long‐term slow‐earthquake activity in this region. Some of the large‐scale slow‐earthquake activity that is detected in this study is consistent with the timings of known slow‐slip events, which implies that other unknown slow‐slip events may have occurred when we detected many events.