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Project of monitoring of the fault activity using 3-component Gladwin Tensor Strainmeter (GTSM) was initiated by the Central Geological Surveyin October 2003 . These instruments are intended to supplement the deformation observations from the continuous GPS arrays as part of a systematic programof plate boundary observation across Tai wan oro-genic belt . Theseinstruments areinstalled at a depth of approxi mately 200 meters at 13 sites of 4 clusters which provide 3 component strain data on both crustal strain accumulation and transient strain variations induced by environmental change such as meteorological effect and earthquakes . TheMW7 .9 Wenchuan earthquake of 12 May 2008 was the most devastating earthquake in China inthe past 30 yearsinterms of humanlosses and property damage .The main shock ruptured with about 9 m of slip along the Longmenshan fault zone located the boundary of Tibetan plateau and Sichuan basin. About 5 ~6 m maxi mumvertical offset was identifiedin the field survey after the earthquake . Nine borehole strainmeters installed at western Foothills in Tai wan orogenic belt captured significant step-like variation of areal strain. The areal strain increasing was observed from0 .01 to 0 .2 microstrain at five bore-holes locatedin Chiayi area of southwestern Tai wan and Hisnchu area of northwest Tai wan. The areal strain decreasing was also observed from0 .05 to 4 microstrain at three boreholes located at Hisnchu and Taipei area of northwest Tai wan. We attribute these step-like transi-ent variations of areal strain to the dynamic triggering of the Wenchuan earthquake .
Project of monitoring of the fault activity using 3-component Gladwin Tensor Strainmeter (GTSM) was initiated by the Central Geological Survey in October 2003. These instruments are intended to supplement the deformation observations from the continuous GPS arrays as part of a systematic program of plate boundary observation across Tai wan oro-genic belt. Theseinstruments areinstalled at a depth of approxi mately 200 meters at 13 sites of 4 clusters which provide 3 component strain data on both crustal strain accumulation and transient strain variations induced by environmental change such as meteorological effect and earthquakes. TheMW7 .9 Wenchuan earthquake of 12 May 2008 was the most devastating earthquake in China inthe past 30 yearsinterms of humanlosses and property damage. The main shock ruptured with about 9 m of slip along the Longmenshan fault zone located the boundary of Tibetan plateau and Sichuan basin About 5 ~ 6 m maxi mumvertical offset was identified in the field surv Nine borehole strainmeters installed at western Foothills in Tai wan orogenic belt captured significant step-like variation of areal strain. The areal strain increasing was observed from0 .01 to 0 .2 microstrain at five bore-holes located in Chiayi area of south are Western Tai wan and Hisnchu area of northwest Tai wan. The areal strain decreased was also observed from0 .05 to 4 microstrain at three boreholes located at Hisnchu and Taipei area of northwest Tai wan. We attribute these step-like transi-ent variations of areal strain to the dynamic triggering of the Wenchuan earthquake.