摘要
文中基于中国地震台网中心在大同火山群及周边地区记录到的2008年1月-2023年1月期间3 218个地震的到时资料,采用双差地震重定位法开展了重新定位研究,获得了2 447个事件的重定位结果。结果显示,地震大多发生在16km深度以浅处,集中分布于断陷盆地内及盆地边界的断裂带附近,整体走向NE-SW,与区域活动构造的活动断裂及其控制的地堑、半地堑型断陷盆地的走向较为一致。这些地震E-W向、S-N向、垂直向的平均定位误差约为0.21km、0.22km、0.30km,平均均方根残差为0.14s。口泉断裂带附近的地震分布由南部的较深、较集中变化为北部的较浅、较分散,可能与矿山开采活动有关。大同-阳高地震震源区的地震多集中在与大王村断裂平行的东侧隐伏断层的3~16km深度处,该隐伏断层与团堡断裂和六棱山山前断裂交会,可能与大同-阳高地震的余震活动有关。火山区内部的地震活动并不强烈。结合该区域新的背景噪声层析成像结果分析发现,大多数地震发生在低速异常边界,可能暗示了这些地震的发生与热物质上涌所携带的流体上升至地壳深度,进而降低断面有效正应力密切相关。
In the present study we collect a large amount of arrival times from 3 218 earthquakes in the Datong volcanic group and surrounding areas from January 2008 to January 2023 through the China Seismic Network Center and relocated these earthquakes using double-difference location algorithm,finally obtain 2 447 relocate earthquakes.Our result shows that most earthquakes occurred above a depth of 16km,and earthquakes in the basin occurred at depths of 5-16km.There are fewer earthquakes occur near the surface at depths of 0-2km,while 6km and 11km are the dominant depths for earthquakes.The overall strike trending of these earthquake sequences is NE-SW,which is consistent with the regional active faults and controlled grabens and semi-graben-type faulting basins.In addition,these earthquakes are more concentrated near the Kouquan fault zone and in the Datong-Yanggao earthquake zone in the eastern part of the volcanic group.The average location errors of these earthquakes in the east-west,north-south,and vertical directions are about 0.21km,0.22km,and 0.30km,respectively,with an average travel time residual of 0.14s.The earthquakes near the Kouquan fault zone changed from deeper and more concentrated in the south to shallower and more scattered in the north.The earthquake sequences in the northern part of the southern section and the southern part of the middle section of the Kouquan fault zone are deeper along the NE-SW direction,roughly vertically distributed on the Kouquan fault.The earthquake sequences in the northern part of the middle section of the Kouquan fault zone did not occur on the Kouquan fault,and the distribution of earthquakes is relatively scattered,and earthquakes with larger magnitude are mostly concentrated at shallow depth,which may be related to the thick sedimentary coal-bearing strata and mining activities in the area.The strike trending of these earthquakes in the northern section of the Kouquan fault zone is,along the NE-SW direction,roughly distributed on the Kouquan fault.However,there are also earthquakes in the northern part of the Kouquan fault zone,which may suggest that the activity of the Kouquan fault zone has extended there.The focal depth in the source areas of the Datong-Yanggao earthquake is mostly concentrated at depths of 3-16km on the hidden fault parallel to the NE-SW trending Dawangcun fault to the east.The hidden fault has a large dip angle and dips towards NW,which intersects with the Tubao fault and the Liulengshan piedmont fault,likely related to the aftershock activity of the Datong-Yanggao earthquake.Earthquakes occur frequently in the middle section of the Huairen fault,followed by the southern section,and there are few earthquakes in the northern section.The seismic activity of the Shuiyu fault,the east fault of the Cailiangshan mountains,and the Yanggao-Tianzhen fault is relatively weaker.There are some seismic activities in the central part of the northern margin fault of the Tianzhen-Yanggao Basin.Earthquakes in volcanic areas occurred at the boundaries of volcanic clusters,while the seismicities inside the volcanic group area were not very strong,which suggests that the boundary of volcanic clusters is more prone to stress accumulation and earthquake generation than the interior of volcanic clusters.Based on the new seismic results of ambient noise tomography in the area,it is found that earthquakes are not only related to faults,but more importantly,most earthquakes occur near the high-to-low-velocity anomaly boundaries.Furthermore,there are obvious low-velocity anomalies visible beneath most earthquake source areas,which may suggest that the occurrence of these earthquakes is closely related to fluids carried by the upwelling of thermal materials rising to the crust from the mantle and reducing the effective normal stress on the fault planes.
作者
许永强
雷建设
XU Yong-qiang;LEI Jian-she(School of Coal Engineering,Shanxi Datong University,Datong 037000,China;Key Laboratory of Crustal Dynamics,National Institute of Natural Hazards,Ministry of Emergency Management of China,Beijing 100085,China)
出处
《地震地质》
EI
CSCD
北大核心
2024年第2期336-356,共21页
Seismology and Geology
基金
应急管理部国家自然灾害防治研究院科技创新团队建设项目(2023-JBKY-55)
国家自然科学基金(U1939206)
山西省研究生教育创新项目(2022Y764)
山西大同大学研究生教育创新项目(22CX05)共同资助。
关键词
大同火山群
口泉断裂带
大同-阳高震区
地震重定位
Datong volcanic group
Kouquan fault zone
Datong-Yanggao earthquake zone
earthquake relocation
