Based on the integrative interpretation of travel-time data and amplitude information obtained from the deep seismic sounding experiment on the Chuxiong-Luoping profile, eastern Yunnan province, carried out in January...Based on the integrative interpretation of travel-time data and amplitude information obtained from the deep seismic sounding experiment on the Chuxiong-Luoping profile, eastern Yunnan province, carried out in January of 2005, we present a 2-D P wave velocity structure along the profile. The crustal structure shows remarkable contrasts between the two sides of the Xiaojiang fault zone, although the whole profile is situated within the Yangtze platform. The average P wave velocities of the crust on the west and east sides of the fault zone are 6.21 km/s and 6.32 km/s, respectively, and the crustal thicknesses are 41 km and 45 km, respectively. These results imply that the crust to the east of the Xiaojiang fault zone presents characteristics of crustal structure in a stable platform, while the crust to the west is complicated with a lower velocity zone in middle of the upper crust. The average velocity of 6.21 km/s is lower than the global continental crustal average （6.30 km/s）, indicating that the region is tectonically active. According to the lateral variation of velocity and depth of interfaces （including the Moho）, it is inferred that the Xiaojiang fault zone has cut through the whole crust. It is also deduced that existence of low velocity zone in middle of the upper crust is conducive to the south-southeastern sliding of the Sichuan- Yunnan （Chuan-Dian） rhombus block.展开更多
The crust/upper-mantle velocity structure and deep tectonic features are obtained in Haiyuan M = 8. 5 earthquake region from data processing of Xiji-Zhongwei deep seismic sounding (DSS) profile. The result shows that ...The crust/upper-mantle velocity structure and deep tectonic features are obtained in Haiyuan M = 8. 5 earthquake region from data processing of Xiji-Zhongwei deep seismic sounding (DSS) profile. The result shows that there is a great difference between the velocity structures on the two sides of the epicenter. The crust consists of alternative high and low velocity layers on the southern side while on the northern side it consists of a series of layers with positive velocity gradient. There exists a deep fault cutting Moho or an anomalous deep structural zone in the epicentral region.展开更多
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
基金supported by the project "Exploration of Active Seismic Faults in Large Cities and Earthquake risk Assessment"National Natural Science Foundation of China (Grant No. 40774037)Contribution No.is 09FE3004 of Institute of Geophysics,China Earthquake Administration
文摘Based on the integrative interpretation of travel-time data and amplitude information obtained from the deep seismic sounding experiment on the Chuxiong-Luoping profile, eastern Yunnan province, carried out in January of 2005, we present a 2-D P wave velocity structure along the profile. The crustal structure shows remarkable contrasts between the two sides of the Xiaojiang fault zone, although the whole profile is situated within the Yangtze platform. The average P wave velocities of the crust on the west and east sides of the fault zone are 6.21 km/s and 6.32 km/s, respectively, and the crustal thicknesses are 41 km and 45 km, respectively. These results imply that the crust to the east of the Xiaojiang fault zone presents characteristics of crustal structure in a stable platform, while the crust to the west is complicated with a lower velocity zone in middle of the upper crust. The average velocity of 6.21 km/s is lower than the global continental crustal average （6.30 km/s）, indicating that the region is tectonically active. According to the lateral variation of velocity and depth of interfaces （including the Moho）, it is inferred that the Xiaojiang fault zone has cut through the whole crust. It is also deduced that existence of low velocity zone in middle of the upper crust is conducive to the south-southeastern sliding of the Sichuan- Yunnan （Chuan-Dian） rhombus block.
基金State Natural Scientific Foundation of China (No. 49734240) the China Seismological Bureau in the Project 95-04-09 and the Xinjiang Uygur Autonomous Region in the National 305 Project 96-915-07-03.
基金the State Key Project(95-13-02-02),China.Contribution No.200012,the Research Center of Exploration Geophysics,CSB.
文摘The crust/upper-mantle velocity structure and deep tectonic features are obtained in Haiyuan M = 8. 5 earthquake region from data processing of Xiji-Zhongwei deep seismic sounding (DSS) profile. The result shows that there is a great difference between the velocity structures on the two sides of the epicenter. The crust consists of alternative high and low velocity layers on the southern side while on the northern side it consists of a series of layers with positive velocity gradient. There exists a deep fault cutting Moho or an anomalous deep structural zone in the epicentral region.
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.
