Abstract
Stress may induce apparent resistivity changes. Clarifying the deformation process of the source media is critical for determining the correlations between resistivity variations and earthquake occurrence. In this study, the stress state of a medium was analyzed by integrating GPS measurements, the spatiotemporal evolution of the load/unload response ratio (LURR), geochemical monitoring, and synchronous apparent resistivity changes preceding the 2020 Mw 6.0 Jiashi earthquake. The medium hosting the Kalpin Observatory underwent elastic deformation before 2019, and the synchronous decreases in the E–W and N–S apparent resistivities from 2015 can be attributed to N–S-dominated compressive stress. The microdamage stage occurred in 2019, with subsequent E–W apparent resistivity variation amplitudes that were ~0.4 Ωm higher than those in previous years. This difference is a result of microdamage to the medium owing to tensile stress during the seismogenic process. The spatiotemporal evolution of the LURR and gas seepage monitoring data also indicate that the medium was damaged prior to the earthquake. Variations in the apparent resistivity measured at the Kalpin Observatory indicate that the medium underwent elastic deformation, followed by microdamage, until stress triggered the earthquake.
Highlights
Resistivity is an important physical property of geotechnical materials that varies with stress [1,2,3,4]
Zhao et al [49] investigated the response of apparent resistivity to tensile and compressive stresses under different conditions and found that the apparent resistivity usually decreased under compression (Figure 5a) and increased under tension (Figure 5b)
The resistivity increase recorded in the E–W direction tions can be attributed to compressive stress
Summary
Resistivity is an important physical property of geotechnical materials that varies with stress [1,2,3,4]. Determining the deformation state of a medium is an important step for establishing correlations between changes in apparent resistivity and earthquakes. When the stress accumulation increases, the rock enters the yield stage and its loading response rate exceeds that of unloading This decreases the strength of the rock or damages it, eventually causing failure. This mechanism has been exploited to propose a method for quantitatively describing the stage of damage to a medium, known as the load/unload response ratio (LURR) [35,36,37]. To determine the correlation between apparent resistivity changes and the Jiashi Mw 6.0 earthquake, the spatiotemporal evolution of the LURR, GPS strain monitoring, and synchronous gas seepage data were utilized in this study to investigate the deformation state of the medium in the seismogenic region.
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