Detecting small offshore earthquakes with Back-Projection Imaging and Match-filter Method

Tian Feng, & Lingsen Meng

Published August 14, 2017, SCEC Contribution #7674, 2017 SCEC Annual Meeting Poster #150

The detection of offshore seismicity in shallow portion of the subduction zones is ineffective due to the large distance from landward instruments. To better understand the offshore seismicity and slow slip around recent megathrust earthquakes, we propose to improve the capability of detecting offshore events by combing two recently developed techniques: Back Projection (BP) imaging and match-filter detection (MF). The MF method searches for similar patterns by cross correlating waveforms of known template events with continuous seismic records. However, the MF method is heavily relying on known earthquake templates, which are obtained from the routine catalogs that lack events in the offshore region. by including BP-detected events as additional templates in the MF detection, we can potentially improve the picture of offshore seismicity. To enhance the accuracy of the imaged aftershock locations in the BP imaging, we apply the recently developed slowness correction that accounts for the 3D travel-time uncertainty. In our initial effort, we studied the 2011 M 9.0 Tohoku-Oki earthquake: We first perform BP imaging in the first 24 hours following the mainshock and detected 538 new events previously undocumented in the JMA catalog. We then take them as MF templates and find additional 9098 new events within 60 days after the mainshock.

Key Words
Back Projection, Match Filter, Small Earthquakes

Citation
Feng, T., & Meng, L. (2017, 08). Detecting small offshore earthquakes with Back-Projection Imaging and Match-filter Method. Poster Presentation at 2017 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology