The Zhangjiakou-Bohai Sea fault zone located in the northern part of the North China region is a seismotectonic zone controlling the present-day strong earthquake activities. Under the effect of regional principal com...The Zhangjiakou-Bohai Sea fault zone located in the northern part of the North China region is a seismotectonic zone controlling the present-day strong earthquake activities. Under the effect of regional principal compressive stress with the direction of NEE-SWW, a series of NE-trending active tectonic zones have developed, which form a group of conjugated shear fracturing systems and control the occurrence of the present-day strong earthquakes. The feature of crustal deformation around this fault zone is studied in the paper. The long-term crustal deformation pattern from GPS measurements exhibits a relatively complete left-lateral strike-slip movement along the active fault zone. However, studies on crustal deformation by stages indicate that a series of NE-trending large-scale anomalous gradient zones have appeared along the Zhangjiakou-Bohai Sea fault zone before moderately strong earthquakes. They are represented respectively by the activities of the Tangshan-Hejian, the Sanhe-Laishui and the Yanhuai-Shanxi seismotectonic zones. This may indicate the occurrence of med-term precursors to moderately strong earthquakes along Zhangjiakou-Bohai Sea zone. The results in the paper show that the crustal deformation pattern before strong earthquake reveals the information of strain status in the deep seismogenic zone, while the chaotic pattern after the occurrence of strong earthquake represents the adjustment of the covering strata.展开更多
The Zhangjiakou-Bohai Sea seismic belt is an important seismic zone in North China. The direction of principal compressive stress is near EW in this region. According to digital seismic data from the Capital Region fr...The Zhangjiakou-Bohai Sea seismic belt is an important seismic zone in North China. The direction of principal compressive stress is near EW in this region. According to digital seismic data from the Capital Region from September 2005 to September 2010,and using the SAM method,the spatial distribution of the crust anisotropy characteristics are studied and discussed in the middle-eastern part of the Zhangjiakou-Bohai Sea seismic belt. The principal polarization direction,which is near EW direction,is obvious in the middleeastern Zhangjiakou-Bohai Sea seismic belt. The spatial distribution of polarization direction crossing the Zhangjiakou-Bohai Sea seismic belt shows that there is little difference among the Yanshan uplift area,inside of the seismic zone and North China basin,and the principal polarization direction is near EW.展开更多
文摘The Zhangjiakou-Bohai Sea fault zone located in the northern part of the North China region is a seismotectonic zone controlling the present-day strong earthquake activities. Under the effect of regional principal compressive stress with the direction of NEE-SWW, a series of NE-trending active tectonic zones have developed, which form a group of conjugated shear fracturing systems and control the occurrence of the present-day strong earthquakes. The feature of crustal deformation around this fault zone is studied in the paper. The long-term crustal deformation pattern from GPS measurements exhibits a relatively complete left-lateral strike-slip movement along the active fault zone. However, studies on crustal deformation by stages indicate that a series of NE-trending large-scale anomalous gradient zones have appeared along the Zhangjiakou-Bohai Sea fault zone before moderately strong earthquakes. They are represented respectively by the activities of the Tangshan-Hejian, the Sanhe-Laishui and the Yanhuai-Shanxi seismotectonic zones. This may indicate the occurrence of med-term precursors to moderately strong earthquakes along Zhangjiakou-Bohai Sea zone. The results in the paper show that the crustal deformation pattern before strong earthquake reveals the information of strain status in the deep seismogenic zone, while the chaotic pattern after the occurrence of strong earthquake represents the adjustment of the covering strata.
基金funded by the Special Fund for Basic Research and Operating Expenses of Institute of Earthquake Science,CEA(2009-11)Key Project of International Science and Technology Cooperation and Exchange of Ministry of Science and Technology of the People's Republic os China(2010DFB20190)
文摘The Zhangjiakou-Bohai Sea seismic belt is an important seismic zone in North China. The direction of principal compressive stress is near EW in this region. According to digital seismic data from the Capital Region from September 2005 to September 2010,and using the SAM method,the spatial distribution of the crust anisotropy characteristics are studied and discussed in the middle-eastern part of the Zhangjiakou-Bohai Sea seismic belt. The principal polarization direction,which is near EW direction,is obvious in the middleeastern Zhangjiakou-Bohai Sea seismic belt. The spatial distribution of polarization direction crossing the Zhangjiakou-Bohai Sea seismic belt shows that there is little difference among the Yanshan uplift area,inside of the seismic zone and North China basin,and the principal polarization direction is near EW.
