Abstract
The coseismic geothermal changes of ground temperature observed at observatories near the epicenter of the 2020 Jiashi Ms = 6.4 earthquake in China, provide a unique opportunity to study heat generation and conduction in rock. Here, evolutions of rock temperature at the Xikeer, Jiashizongchang, and Gedaliang observatories, which are located at epicentral distances of 1.4, 27.42, and 50 km respectively, were analyzed. Significant coseismic geothermal changes of 0.0432 °C were observed at the Xikeer observatory at the depth of 33.38 m, at which clear diurnal variations can be observed. Smaller changes of ~0.0001 °C were observed at the depths of 12.3 and 22.8 m at the Xikeer observatory and 22.3 m at the Jiashizongchang observatory. The stress transfer induced by the coseismic rupture induced a rise in local ground temperature, but the magnitude of the change was relatively small. The larger amplitude change at the Xikeer observatory was caused by fluid infiltration. We note that diurnal variation has been recorded at the Gedaliang observatory, but the coseismic response is no longer in existence. The temperature increases at the hypocentral area were higher than expected in the ground due to the coseismic stress transfer, but the change attenuated rapidly with distance.
Highlights
Accepted: 17 January 2022Coseismic geothermal change generally refers to the physical change process of ground temperature that is a direct response to the occurrence of earthquakes, which could be used as an effective and useful tool for studying and monitoring coseismic ground deformation and the rupture process
By comparing the coseismic responses recorded at different locations and different layers within 50 km of the epicenter, we examined the heat source, generation method, and conduction process of the coseismic geothermal change
This paper focuses on the explanation derived from the magnitude of the observed coseismic variations at different stations during the 2020 Jiashi Ms = 6.4 earthquake
Summary
Coseismic geothermal change generally refers to the physical change process of ground temperature that is a direct response to the occurrence of earthquakes, which could be used as an effective and useful tool for studying and monitoring coseismic ground deformation and the rupture process. A similar coseismic geothermal change on ground temperature was observed again when studying the meta-instability process before the Jiashi Ms = 6.4 earthquake in 2020 [12], and it has been speculated that the physical mechanism of the coseismic response can mainly be attributed to changes in seismic stress and secondary fluid effects. The physical mechanism of the coseismic geothermal change can be explained by the friction along the seismic fault plane [13], the ascension of underground heat flow [14], and the deformation or fracture attributable to local bedrock stress [15]. By comparing the coseismic responses recorded at different locations and different layers within 50 km of the epicenter, we examined the heat source, generation method, and conduction process of the coseismic geothermal change
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