In order to investigate the interrelations of crust and upper mantle tectonics and its velocity distribution as well as seismicity in the Yanhuai basin and its surrounding area, a nearly EW trending Beijing Huailai ...In order to investigate the interrelations of crust and upper mantle tectonics and its velocity distribution as well as seismicity in the Yanhuai basin and its surrounding area, a nearly EW trending Beijing Huailai Fengzhen wide angle reflection/refraction profile, which obliquely passes through seismic zone of Zhangjiakou Bohai Sea and coincides with a deep reflection profile in the Yanhuai basin, was completed recently. The results show: The crust presents layered structures and its thickness gradually increases from 35.0 km in Shunyi to 42.0 km in the west end of the profile; the interior crustal interfaces appear approximately horizontal or slowly sloping down from east to west; In the Yanhuai basin, the crust presents the characteristics of higher velocities alternating with the lower ones and the low velocity bodies obviously exist in the lower part of upper crust. Moreover, there are two deep crustal fault zones which stretch to the Moho discontinuity, are closely related with the seismicity in the Yanhuai area.展开更多
In this paper, the typical velocity structures and average velocities of the crust in six different active tectonic block regions are presented on the basis of previous studies and their tectonic implications are disc...In this paper, the typical velocity structures and average velocities of the crust in six different active tectonic block regions are presented on the basis of previous studies and their tectonic implications are discussed. The results show that different tectonic units have different features of crustal velocity structures. In general, there are low velocity distributions in the crust in regions with strong tectonic activities, and the scales of low velocity distributions are related to the tectonic activities. The average velocities are relatively low in such regions. This reflects strong crustal deformation and the variations of states of matter in the crust resulting from strong tectonic movements. These regions are also seismically active zones frequented by strong earthquakes. Therefore, studying crustal velocity structures of these regions is of great importance to understanding crustal geodynamic process and seismogenic tectonic background.展开更多
文摘In order to investigate the interrelations of crust and upper mantle tectonics and its velocity distribution as well as seismicity in the Yanhuai basin and its surrounding area, a nearly EW trending Beijing Huailai Fengzhen wide angle reflection/refraction profile, which obliquely passes through seismic zone of Zhangjiakou Bohai Sea and coincides with a deep reflection profile in the Yanhuai basin, was completed recently. The results show: The crust presents layered structures and its thickness gradually increases from 35.0 km in Shunyi to 42.0 km in the west end of the profile; the interior crustal interfaces appear approximately horizontal or slowly sloping down from east to west; In the Yanhuai basin, the crust presents the characteristics of higher velocities alternating with the lower ones and the low velocity bodies obviously exist in the lower part of upper crust. Moreover, there are two deep crustal fault zones which stretch to the Moho discontinuity, are closely related with the seismicity in the Yanhuai area.
文摘In this paper, the typical velocity structures and average velocities of the crust in six different active tectonic block regions are presented on the basis of previous studies and their tectonic implications are discussed. The results show that different tectonic units have different features of crustal velocity structures. In general, there are low velocity distributions in the crust in regions with strong tectonic activities, and the scales of low velocity distributions are related to the tectonic activities. The average velocities are relatively low in such regions. This reflects strong crustal deformation and the variations of states of matter in the crust resulting from strong tectonic movements. These regions are also seismically active zones frequented by strong earthquakes. Therefore, studying crustal velocity structures of these regions is of great importance to understanding crustal geodynamic process and seismogenic tectonic background.
