The first 30 min hidden aftershocks of the 2022 September 17, ML 6.4, Guanshan, Taiwan earthquake and its seismological implications

• Published in: TAO : Terrestrial, atmospheric, and oceanic sciences Vol. 35; no. 1; pp. 1 - 14
• Main Authors: Huang, Bor-Shouh, Ku, Chin-Shang, Lin, Chin-Jen, Lee, Shiann‐Jong, Chen, Yen-Ling Eileen, Jiang, Juen-Shi, Sun, Wei-Fang
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 01.12.2024; Chinese Geoscience Union (Taiwan); Springer
• Subjects: Aftershocks; Atmospheric Sciences; Automatic control; Automatic gain control; Back-projection; Catalogues; Central Weather Bureau; Earth and Environmental Science; Earth Sciences; Earthquakes; Geological hazards; Geology; Guanshan earthquake; Hidden aftershocks; Oceanography; Original Article; Physics; Seismic activity; Seismic hazard; Seismology; Temporal variations; Waveforms; Philippine Sea; Taiwan; Guanshan earthquake; Back-projection; Hidden aftershocks; Central Weather Bureau; Automatic gain control
• ISSN: 1017-0839; 2311-7680
• DOI: 10.1007/s44195-023-00059-x

The first 30 min of the aftershock sequence following the 2022 September 17, M L 6.4, Guanshan, Taiwan earthquake is investigated by the back-projection (BP) method. Based on the Automatic Gain Control (AGC) to process individual earthquake record and sort waveforms by epicentral distance, 80 events are identified near the Guanshan earthquake epicenter to verify its temporal variation. However, most of these events cannot clearly image by the BP method to determine its spatial locations for its small amplitude and short time separation. In total, 29 aftershocks are imaged by this study to identify its spatial locations during this time period. The relocated events are compared with the Central Weather Bureau (CWB) rapid report catalogue. Only 5 events have been reported by the CWB rapid report catalogue. These unreported hidden aftershocks are identified to distribute surrounding the epicenter and extended to the east. This extracted information of hidden aftershocks is crucial for assessing the potential for future large aftershocks and estimating the associated seismic hazards in a given region, and provide extra message to evaluate the source physics in general. Key Points Propose and verify earthquake location using the back-projection method. Discover 29 hidden events with 30 min after the Guanshan earthquake. Provide extra information to study following large aftershocks and to estimate its associated seismic hazards.