Determination of the major axis direction and macroseismic epicenter of the assessed intensity map based on relocated aftershock sequences

Frontiers in Earth Science

Earth Science

Xintao Wen¹  Jie Liu¹  Zhishuang Xu¹  Xiaoli Li¹  Jing Ren¹  Alimujiang Yalikun² 

[1] China Earthquake Networks Center, Beijing, China;Earthquake Administration of Xinjiang Uygur Autonomous Region, Urumqi, China;

关键词: assessed intensity map;    aftershock sequences;    major axis direction;    macroseismic epicenter;    earthquake emergency response;   

DOI  :  10.3389/feart.2023.1128827

 received in 2022-12-21, accepted in 2023-06-28,  发布年份 2023

来源: Frontiers

【 摘 要 】

The rapid assessment of an intensity map following a strong earthquake forms the foundation for risk assessment and emergency response in Chinese mainland. The determination of the major axis direction in the assessed intensity map depends on various factors, including nearby active faults, instrumental intensities, and the distribution of aftershocks. To evaluate the effectiveness of promptly determining the major axis direction based on early aftershock distribution, we relocated and analyzed aftershock sequences occurring within 2 h of eighteen aftershock-rich earthquakes with a magnitude of Ms ≥ 6.0 in Chinese mainland from 2012 to 2021. HypoDD was used for relocation, and the standard deviational ellipse fitting technique was employed for analysis. Comparing the aftershock ellipses resulting from our analysis with the macroseismic intensity maps obtained from field surveys reveals a high level of agreement, with an average difference of approximately 9° in the major axis directions of the aftershock ellipses and the meizoseismal zones. For the majority of earthquakes, regardless of focal mechanisms, the lengths of the major axes of the aftershock ellipses closely correspond to the intensity VIII scale. Additionally, the spatial distribution of aftershocks aids in distinguishing the seismogenic fault from the two fault planes with distinctly different dips as indicated by the focal mechanism solution. Moreover, the distance between the aftershock center and the macroseismic epicenter systematically increases as the dip decreases. These findings hold significant scientific value as they contribute to the prompt determination of assessed intensity maps and provide effective guidance for earthquake emergency response.

【 授权许可】

Unknown   
Copyright © 2023 Xu, Liu, Yalikun, Li, Ren and Wen.