An M5.1 earthquake occurred in Badong County, only 66 km from the Three Gorges Dam, on De- cember 16, 2013. The continuous gravity observation data obtained at Yichang seismostation nearest to the epi- center （96 km...An M5.1 earthquake occurred in Badong County, only 66 km from the Three Gorges Dam, on De- cember 16, 2013. The continuous gravity observation data obtained at Yichang seismostation nearest to the epi- center （96 km） were analyzed, and it was found that the continuous gravity observation data obtained in this rainy season did not exhibit a characteristic of seasonal change in gravity identical to that in the past years, and thereafter the M5.1 Badong earthquake occurred. Numerical simulation revealed that the water storage and discharge of the Three Gorges reservoir generated seasonal change in gravity, and the changes in atmospheric pressure and gravity load were not the main sources of the seasonal change of continuous gravity observation data whether in respect of magnitude or phase and did not have obvious breaking change on annual variation before the earthquake. Through analysis of the seasonal change data observed on the same site including cavern temperature, rainfall data and global terrestrial water model （CPC） simulated water load, it was thought that, in the observation room with cavern temperature change of only -0.1 l^C/a at Yichang seismostation, the sea- sonal change of continuous gravity observation result mainly originated from the seasonal change in rainfall. In the case that the changes in rainfall and its water load did not have evident breaking change on annual varia- tion law before the earthquake, if the MS. 1 Badong earthquake was the cause of the breaking change on annual variation law in Yichang this time, then it was believed through analysis of crust expansion ratio that similar a- nomaly should occur at a crust expansion and compression intersection, no more than 100 km away from the epicenter.展开更多
The focal mechanism solutions of the MS. 1 Badong earthquake and subsequent 34 aftershocks at ML 2.0 or more were calculated using the P-wave first motion method; the main earthquake was normal fault dip slip type, an...The focal mechanism solutions of the MS. 1 Badong earthquake and subsequent 34 aftershocks at ML 2.0 or more were calculated using the P-wave first motion method; the main earthquake was normal fault dip slip type, and the slip types of the seismogenic rupture surfaces of the subsequent aftershocks primarily include normal dip slip （14 times）, reverse dip slip （9 times）, normal strike slip （9 times） and reverse strike slip （2 times）. The MS. 1 Badong earthquake activities may be related to the stress adjustment caused by the rise of the groundwater level and the decrease of the frictional resistance between structural planes of rock forma- tions due to the effect of reservoir water penetration, and related to the joint activities of the NE-strike Gaoqiao fault and the near EW-strike Daping fault.展开更多
基金supported by the Director Foundation of Institute of Seismology,China Earthquake Administration(IS201156069,IS201326123)the National Natural Science Foundation of China(41204058)
文摘An M5.1 earthquake occurred in Badong County, only 66 km from the Three Gorges Dam, on De- cember 16, 2013. The continuous gravity observation data obtained at Yichang seismostation nearest to the epi- center （96 km） were analyzed, and it was found that the continuous gravity observation data obtained in this rainy season did not exhibit a characteristic of seasonal change in gravity identical to that in the past years, and thereafter the M5.1 Badong earthquake occurred. Numerical simulation revealed that the water storage and discharge of the Three Gorges reservoir generated seasonal change in gravity, and the changes in atmospheric pressure and gravity load were not the main sources of the seasonal change of continuous gravity observation data whether in respect of magnitude or phase and did not have obvious breaking change on annual variation before the earthquake. Through analysis of the seasonal change data observed on the same site including cavern temperature, rainfall data and global terrestrial water model （CPC） simulated water load, it was thought that, in the observation room with cavern temperature change of only -0.1 l^C/a at Yichang seismostation, the sea- sonal change of continuous gravity observation result mainly originated from the seasonal change in rainfall. In the case that the changes in rainfall and its water load did not have evident breaking change on annual varia- tion law before the earthquake, if the MS. 1 Badong earthquake was the cause of the breaking change on annual variation law in Yichang this time, then it was believed through analysis of crust expansion ratio that similar a- nomaly should occur at a crust expansion and compression intersection, no more than 100 km away from the epicenter.
基金supported by the Director Foundation of the Institute of Seismology,China Earthquake Adminstration(IS201246114)the Special Fund of China Three Gorges Corporation(SXSN/3354)
文摘The focal mechanism solutions of the MS. 1 Badong earthquake and subsequent 34 aftershocks at ML 2.0 or more were calculated using the P-wave first motion method; the main earthquake was normal fault dip slip type, and the slip types of the seismogenic rupture surfaces of the subsequent aftershocks primarily include normal dip slip （14 times）, reverse dip slip （9 times）, normal strike slip （9 times） and reverse strike slip （2 times）. The MS. 1 Badong earthquake activities may be related to the stress adjustment caused by the rise of the groundwater level and the decrease of the frictional resistance between structural planes of rock forma- tions due to the effect of reservoir water penetration, and related to the joint activities of the NE-strike Gaoqiao fault and the near EW-strike Daping fault.
