Radiated seismic energy from the 2021 ML 5.8 and ML 6.2 Shoufeng (Hualien), Taiwan, earthquakes and their aftershocks

• Published in: TAO : Terrestrial, atmospheric, and oceanic sciences Vol. 33; no. 1; pp. 1 - 10
• Main Authors: Hwang, Ruey-Der, Huang, Yi-Ling, Chang, Wen-Yen, Lin, Cai-Yi, Lin, Chiung-Yao, Wang, Sheng-Tung, Chan, Jing-Bei, Chang, Jo-Pan, Lin, Tzu-Wei
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 01.12.2022; Springer
• Subjects: 2021 Shoufeng earthquake; Atmospheric Sciences; Earth and Environmental Science; Earth Sciences; Local magnitude; Moment magnitude; Oceanography; Original Article; Radiated seismic energy; Seismic moment; Seismic moment; 2021 Shoufeng earthquake; Moment magnitude; Radiated seismic energy; Local magnitude
• ISSN: 1017-0839; 2311-7680
• DOI: 10.1007/s44195-022-00020-4

We calculated radiated seismic energy (E S ), seismic moment (M 0 ), and moment magnitude (M W ) and then determined the E S –M L , E S –M 0 , M 0 –M L , and M W –M L relations for the 2021 Shoufeng earthquake sequence (2.5 < M L  < 6.3), where M L is the local magnitude. Notably, a crossover magnitude was detected as M L  = 4.0 for the earthquake sequence. For M L  < 4.0, we obtained logM 0  ∝ M L , M W  ∝ 0.67M L , and a low E S /M 0 , indicating a low average stress drop; for M L  > 4.0, logM 0  ∝ 0.67M L , M W  ∝ M L , and a high E S /M 0 were present, and then there was a high average stress drop. These derived relations implied that source duration ( T ) is independent of M 0 for M L  < 4.0. Moreover, the M 0  ∝  T 3 relation seemed able to interpret those relations for M L  > 4.0. Nevertheless, the E S –M L relation remains logE S  ∝ 2.0M L for 2.5 < M L  < 6.3. From this study, the derived relations could not predict the source parameters for M L  > 6.3 events. This might indicate that M L saturates beyond M L 6.3. Through such analyses, we not only established the relations among source parameters but also elucidated the basic physics of the earthquake sequence. Key points logEs is proportional to 2.0M L for the Shoufeng earthquake sequence in Taiwan. A crossover magnitude detected at M L  = 4.0 divides the M W –M L relation into two parts. For M L  > 4.0, logM 0  ∝ 0.67M L and M W  ∝ M L ; for M L  < 4.0, logM 0  ∝ M L and M W  ∝ 0.67M L .