The existence of saturated vapors in the deep source region of 2017Pohang earthquake evidenced from seismic tomography  

作　　者：JiaWei Qian HaiJiang Zhang Lei Guo Uzonna Okenna Anyiam Changsoo Cho Kang Hyeun Ji HaoRan Ma 

机构地区：[1]School of Carbon Neutrality Science and Engineering,Anhui University of Science and Technology,Hefei 231131,China [2]College of Oceanography,Hohai University,Nanjing 210098,China [3]Laboratory of Seismology and Physics of Earth’s Interior,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China [4]Hebei Earthquake Agency,Shijiazhuang 050022,China [5]Geological and Environmental Science,Hope College,Holland,MI 49423,US [6]Earthquake Research Center,Korea Institute of Geoscience and Mineral Resources,Daejeon 34132,Korea

出　　处：《Earth and Planetary Physics》2024年第5期811-821,共11页地球与行星物理（英文版）

基　　金：supported by the National Natural Science Foundation of China(42304056);the Natural Science Foundation of Hebei Province(D2023305007);supported by the Basic Research Project(GP2020-017,GP2020027)of the Korea Institute of Geoscience and Mineral Resources(KIGAM)funded by the Ministry of Science and ICT of Korea;。

摘　　要：Geothermal resources are a promising approach to clean renewable energy;90%of them are deep reservoirs of hot dry rock that require hydraulic fracturing to create a network of connections among wells to enable efficient heat exchange,known as an Enhanced Geothermal System(EGS).The Pohang EGS project in south Korea led to a devasting Mw5.5 earthquake,triggered by the reservoir's EGS stimulation,the largest earthquake known to have been induced by EGS development.Detailed investigations have been conducted to understand the cause of the Pohang earthquake;the conclusion has been that overpressurized injected fluids migrated into an unknown fault triggering this large earthquake.Detailed velocity images for the source zone of the 2017 Pohang earthquake,which could be helpful for further understanding its inducing mechanism,are unavailable.However,we have assembled detailed aftershock data recorded by 41 local stations installed within about three months after the Mw5.5 Pohang earthquake,and have then applied the V_(p)/V_(s)model's consistency-constrained double-difference seismic tomography method to determine the high-resolution three-dimensional Vp(compressional wave velocity),Vs(shear wave velocity),and V_(p)/V_(s)models of the source region that we report here,as well as earthquake locations within the source region.The velocity images reveal that the deep source area of the 2017 Pohang earthquake is dominated by low Vp,high Vs,and low V_(p)/V_(s)anomalies,a pattern that can be caused by overpressurized vapors due to high temperatures at these depths.Based on aftershock locations and velocity features,our studies support the conclusion that the 2017Pohang earthquake was triggered by injected EGS fluids that migrated into a blind fault.

关 键 词：Pohang earthquake tomoDDMC low V_(p)/V_(s) saturated vapors EGS 

分 类 号：P631.4[天文地球—地质矿产勘探] P314[天文地球—地质学]