Pronounced Changes of Multi-geophysical Parameters Associated with Maduo (M= 7.4) Earthquake

Abstract

The China Earthquake Administration (CEA) has a large network for monitoring multiple geophysical parameters to forecast earthquake and to have early warning information about an impending earthquake. In this paper, we present the analysis of various geophysical measured and borehole parameters (resistivity, borehole strain, water level, water temperature, atmospheric temperature, etc.) within 400 km radius of the epicenter. The strain measured in the borehole show pronounced tensional and compressional changes, and the direction of the main compressive strain is found to rotate clockwise. The active compression of the whole Bayankara block is found to be affected, the resistivity near the fault began to decrease and increase in different directions. The water level observed at the Yushu water well located in the southwest from the epicenter is found to change in the opposite direction at the Huangyuan borehole located in the northeast from the epicenter. Yushu water well station is affected by the clockwise activity of the whole Bayankara block, at this water level increases from 2017 and begins to decline from August 2020. Such pronounced decline in water level far from the epicenter of the earthquake prior to the earthquake event provides an early warning of the Maduo earthquake. The decline of the water level is associated with the changes in the stress within the epicentral region, such changes could provide long-term precursory information about an impending earthquake.