Abnormal Phenomena Recorded by Several Earthquake Precursor Observation Instruments Before

Abnormal Phenomena Recorded by Several Earthquake Precursor Observation Instruments Before the Ms 8.0 Wenchuan, Sichuan Earthquake

OUYANG Zuxi;ZHANG Hongxun;FU Zizhong;GOU Bo;JIANG Wali

【期刊名称】《地质学报（英文版）》 【年(卷),期】2009(083)004

【摘要】The paper introduces the anomalies observed by digital tiltmeter, cross-fault deformation meter, 4-component borehole strainmeter and geothermometer before May 12, 2008, Ms8.0 Wenchuan earthquake, Sichuan. The digital tiltmeter installed in the epicentral region in Shifang County recorded the tilt anomalies 15 days before the earthquake with variation amplitude of 3.7 times larger than the annual deviation of 2007. The cross-fault deformation meter installed at Zimakua station on the Xianshuihe-Anninghe fault zone detected displacement anomaly occurring since 2006 with the variation amplitude exceeding the cumulative value of the last ten years. Five borehole strainmeter stations in the Chongqing section of Three Gorges Reservoir area observed unconventional strain changes occurring in the period from May 1 through 12, 2008. Among them, the strainmeter at Wanzhou station recorded the great compression strain rate on the EW component at 14:00 o'clock of May 10, and the anomaly amplitude was so large that the instrument output exceeded its dynamic range,