Abstract
Eight soil gas measurements were performed in the Liupanshan fault zone (LPSFZ) to observe the concentration and flux of soil gas radon (Rn) and CO2 in October 2017 and October 2018. By combining the historical strong earthquake background and modern seismic activity of the fault zone, the relation between the geochemical distribution characteristics of soil gas and the seismicity of the fault zone was studied herein. Furthermore, the strong seismic hazard potential of the fault zone was discussed. Results show that the concentration of soil gas Rn and CO2 considerably varies in the northern segment of the LPSFZ and is relatively stable in the southern segment. The spatial distribution of the concentration intensity and flux is strong in the north and weak in the south. However, the southern segment of the LPSFZ has a seismic gap that has not been ruptured by strong earthquakes with Ms ≥ 6.5 for the last 1400 years, whereas the seismic activity in the northern segment is relatively frequent, indicating that the fault zone locking degree of the southern segment is higher than that of the northern segment. This observation is completely consistent with the geochemical characteristic distribution of soil gas. Therefore, the southern segment of the LPSFZ should be considered a hazardous segment, where major or strong earthquakes can occur in the future.
Highlights
The crustal fluid is an important constituent of the Earth and a ubiquitous and dynamic component of the Earth’s crust
Earthquakes are caused by a tectonic evolution accompanied by the exchange of matter and energy deep inside the Earth [1,2,3,4], which is mainly transmitted via the release of fluid through active faults and fractures at different depths [5] because faults and fractures are preferential migration pathways for gases (e.g., CO2 and radon (Rn)) in the deep crust to migrate upward to the surface owing to their enhanced permeability and porosity relative to the surrounding rocks [6,7,8]
This study selected Liupanshan fault zone (LPSFZ) as the research area and analyzed the observation of soil gas Rn and CO2 across the fault strike to investigate the geochemical characteristics of this fault zone, synthesize its seismic activities, and investigate its strong earthquake hazard background
Summary
The crustal fluid is an important constituent of the Earth and a ubiquitous and dynamic component of the Earth’s crust. The Liupanshan fault zone (LPSFZ) is located in the northeastern boundary of the Qinghai–Tibet Plateau and is an important part of the North–South seismic zone It undergoes frequent seismic activities and is a key area for earthquake prevention in Northwest (NW) China. Because of the occurrence of several major earthquakes in the western, eastern, and southern boundaries of the Qinghai–Tibet Plateau, after the M8.0 Wenchuan earthquake in 2008, significant deformation and gravitational changes occurred in the same area along the North–South seismic zone. This study selected LPSFZ as the research area and analyzed the observation of soil gas Rn and CO2 across the fault strike to investigate the geochemical characteristics of this fault zone, synthesize its seismic activities, and investigate its strong earthquake hazard background
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