2020年古冶M_(S)5.1地震序列微震检测及活动性研究

Microearthquake detection and seismicity analysis of the 2020 Guye M_(S)5.1 earthquake sequence

2020年7月12日河北省古冶(39.78°N,118.44°E)发生M_(S)5.1地震,震源深度10 km.本文通过对其周边500 km范围内的84个固定台站连续观测地震数据,采用基于图形处理器的模板匹配定位识别技术(GPU-M&L)对地震前后(2020年6月1日至2020年8月31日)共三个月的连续数据进行了微震检测和地震活动性分析.我们首先从台网目录的362个古冶地震序列事件中挑选了信噪比较高的118个地震作为模板,通过模板扫描和检测,获得共1017个地震,约为台网目录的2.8倍,然后运用双差定位方法(hypoDD)对669个地震事件进行了重定位.最后我们对古冶地震的事件序列进行时空分布、震源机制解以及b值空间分布等分析.结果显示古冶M_(S)5.1地震前,震中区周边地震活动性显著,地震前后地震序列分布优势方向为NE向,震源深度方向近直立分布;发震断裂为唐山—古冶断裂或其延伸部分,与1976年唐山M_(S)7.8地震同为唐山断裂带,发震断层走向基本一致.据此,我们推测古冶M_(S)5.1地震是1976年唐山M_(S)7.8地震后余震区应力调整所触发.

On July 12, 2020, a M_(S)5.1 earthquake (epicenter: 39.78°N, 118.44°E) with a depth of ~10 km struck Guye, Tangshan, Hebei province. In this paper, we performed microearthquake detection and seismicity analysis using the three-month continuous waveform data (from June 1, 2020 to August 31, 2020) recorded by 84 stations within 500 km radius around the epicenter. Firstly, we selected 118 high-quality events as templates from 362 events listed in the China Earthquake Network Center (CENC) catalog. By scanning through the three-month continuous data using the Graphic Processing Unit based Match and Locate (GPU-M&L) technique, a total of 1017 events were detected, which is approximately 2.8 times the number in the CENC catalog. Secondly, 669 earthquakes were relocated by applying the double difference relocation algorithm (hypoDD). We then analyzed the temporal-spatial distribution, focal mechanism solutions, and spatial variation of the b-value for the Guye earthquake sequence. Our results reveal that the Guye MS5.1 earthquake sequence exhibits a NE-striking pattern on the surface and a subvertical distribution in depth, which is spatially coincident with the eastward extension of the Tangshan-Guye Fault. Since both the seismogenic faults of the Guye M_(S)5.1 earthquake and the 1976 M_(S)7.8 Tangshan earthquake belong to the Tangshan fault system, we suggest that the Guye earthquake was triggered by stress adjustment of the Tangshan M_(S)7.8 earthquake.