Geological Background Analysis of the 5.1 Magnitude Earthquake in Tangshan on July 12, 2020, Based on the PALM Detection Method
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摘要: 本文利用PALM(Phase picking, Association, Location, and Matchedfilter)全流程地震编目框架构建了2020年7月12日唐山5.1级地震前4天至后13天的高分辨率地震目录,共检测出135次地震事件,揭示了唐山地震序列的空间分布特征。从剖面看,唐山5.1级地震发震断层近直立,主震发生在深部15 km处,余震分布呈现从深到浅的趋势,整体分布呈现NW向,在东南部深度15 km处出现了微震丛集,定位后的地震分布与震源机制解NW向界面一致性较好。结合该区的VP和VP/VS波速比分析,显示地震震中成北西向展布,具有较好的收敛性,在深度8~12 km和20 km处存在着高波速比特征。Abstract: The template matching process of PALM is used to automatically create a high-resolution earthquake catalog for the Tangshan 5.1 earthquake that occurred on July 12, 2020, covering the period from 4 days before to 13 days after the event in this paper. A total of 135 earthquake events were detected, revealing the spatial distribution of the Tangshan earthquake sequence. From the cross-section view, the fault that triggered the Tangshan 5.1 earthquake is nearly vertical, with the main shock occurring at a depth of 15 km. The aftershock distribution shows a trend from deeper to shallower depths, with an overall NW orientation. A microseismic cluster was observed at a depth of 15 km in the southeast.The distribution of the located earthquakes is in good agreement with the NW-oriented fault mechanism solutions. The analysis of the VP and VP/VS velocity ratios in the area shows that the earthquake epicenter is distributed in a northwest direction, exhibiting good convergence, with high velocity ratio characteristics present at depths of 8~12 km and 20 km.
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Key words:
- PALM detection method /
- Earthquake catalog /
- Earthquake location /
- VP/VS ratio
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图 2 PALM工作流程(Zhou等,2022)
Figure 2. PALM workflow diagram(Zhou et al.,2022)
表 1 定位所用一维分层速度模型
Table 1. One-dimensional layered velocity model used for location
深度/km 0 5.0 10.0 15.0 20.0 25.0 35.0 P波/(km·s−1) 5.2 5.8 6.0 6.3 6.5 6.7 7.0 -
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