The Red River Fault Zone is a gigantic slide-slip fault zone extending up to 1000km from Tibet to SouthChina Sea. It has been divided into the north, central and south segments according to the difference of thegeomet...The Red River Fault Zone is a gigantic slide-slip fault zone extending up to 1000km from Tibet to SouthChina Sea. It has been divided into the north, central and south segments according to the difference of thegeometry, kinetics, and seismicity on the land, but according to the contacted relationship between the old pre-Cenozoic block in Indochina Peninsula and the South China block, the Red River Fault Zone was divided into two parts extending from land to ocean, the north and south segments. Since the Tertiary, the Red River Fault Zone suffered first the sinistral movement and then the dextral movement. The activities of the north and the south segments were different. Based on the analysis of earthquakes and focal mechanism solutions,earthquakes with the focus depths of 0-33km are distributed over the whole region and more deep earthquakes are distributed on the northeastern sides of the Red River fault. Types of faulting activities are the thrust in the northwest, the normal in the north and the strike-slip in the south, with the odd type, viz. the transition type, in the other region. These show the Red River Fault Zone and its adjacent region suffered the extruding force in NNW direction and the normal stress in NEE direction and it makes the fault in the region extrude-thrust,horizontal strike-slip and extensional normal movement.展开更多
Based on the results of focal mechanism solutions in southeastern areas of China (south of 34°N and east of 105°E), this article analyzes the correlation of focal mechanism solutions with seismogenic structu...Based on the results of focal mechanism solutions in southeastern areas of China (south of 34°N and east of 105°E), this article analyzes the correlation of focal mechanism solutions with seismogenic structures of moderate strong earthquakes and the direction of potential source zones. The data show that the nodal planes of focal mechanism solutions and the principle stresses in southern China are of predominantly similar directions, most of the solutions for M≥4.0 earthquakes correspond to the main structure directions as well as the directions of potential source zones. The statistical results of multiple small earthquakes concerning nodal planes and main stress axes are also reliable for determining the direction of potential source zones. According to the analysis of focal mechanism solutions, long-axis direction of isoseismals distribution of aftershocks, geologic structures, and seismic activity in two areas of the M_S6.1 earthquake in the south Yellow Sea in 1996 and the M_S5.2 earthquake in Fujian in 1997, the potential source zone division is discussed.展开更多
The seismicity of Longrnenshan fault zone and its vicinities before the 12 May 2008 Wenchuan Ms8.0 earthquake is studied. Based on the digital seismic waveform data observed from regional seismic networks and mobile s...The seismicity of Longrnenshan fault zone and its vicinities before the 12 May 2008 Wenchuan Ms8.0 earthquake is studied. Based on the digital seismic waveform data observed from regional seismic networks and mobile stations, the focal mechanism solutions are determined. Our analysis results show that the seismicities of Longmenshan fault zone before the 12 May 2008 Wenchuan earthquake were in stable state. No obvious phenomena of seismic activity intensifying appeared. According to focal mechanism solutions of some small earthquakes before the 12 May 2008 Wenchuan earthquake, the direction of principal compressive stress P-axis is WNW-ESE. The two hypocenter fault planes are NE-striking and NW-striking. The plane of NE direction is among N50°-70°E, the dip angles of fault planes are 60°-70° and it is very steep. The faultings of most earthquakes are dominantly characterized by dip-slip reverse and small part of faultings present strike-slip. The azimuths of principal compressive stress, the strikes of source fault planes and the dislocation types calculated from some small earthquakes before the 12 May 2008 Wenchuan earthquake are in accordance with that of the main shock. The average stress field of micro-rupture along the Longmenshan fault zone before the great earthquake is also consistent with that calculated from main shock. Zipingpu dam is located in the east side 20 km from the initial rupture area of the 12 May 2008 Wenchuan earthquake. The activity increment of small earthquakes in the Zipingpu dam is in the period of water discharging. The source parameter results of the small earthquakes which occurred near the initial rupture area of the 12 May 2008 Wenchuan earthquake indicate that the focal depths are 5 to 14 km and the source parameters are identical with that of earthquake.展开更多
We estimate the focal depths and fault plane solutions of 46 moderate earthquakes in the Himalayan- Tibetan region by modeling the broadband waveforms of teleseismic P waves. The depths of 38 of these earth- quakes ra...We estimate the focal depths and fault plane solutions of 46 moderate earthquakes in the Himalayan- Tibetan region by modeling the broadband waveforms of teleseismic P waves. The depths of 38 of these earth- quakes range between 0-40 km, with a peak at -5 km. One earthquake is located within the lower crust of the Indian shield. The remaining eight earthquakes occurred between depths of 80 -120 km and are all located in the Pamir-Hindu Kush and the Indo-Myanmar deep seismic zones. None of the earthquakes outside these deep seismic zones are located in the mantle. Global centroid moment tensor （CMT） solutions indicate that most earthquakes in northern Tibet and northern India had thrust-faulting mechanisms and that normal and strike-slip faulting earthquakes occurred primarily in central Tibet. These mechanisms are consistent with the predominantly NNW-SSE compression in the direction of current Himalayan-Tibetan continental collision.展开更多
Objective Ependymal cells are thought to be the primary source of neural stem cells in the adult central nervous system. The purpose of this study is to examine spatial and temporal profiles of ependymal cell prolife...Objective Ependymal cells are thought to be the primary source of neural stem cells in the adult central nervous system. The purpose of this study is to examine spatial and temporal profiles of ependymal cell proliferation and migration after focal cerebral ischemia. Methods Eighty male Sprague Dawley rats underwent permanent middle cerebral artery occlusion after injection of 10 μL of 0.2% Dil into the lateral ventricle. Rats were sacrificed and brain sections were acquired for pathological evaluation and laser confocal imaging at day 1,3,7,11,14,21 and 28 after ischemia. Results The density of Dil-labeled cells in the ischemic ipsilateral subventricular zone was significantly higher than that in the control group and these labeled cells dispersed in the ischemic ipsilateral subventricular zone and/or were located in ependyma from day 1 to 11. In the ischemic ipsilateral cortex, some Dil-labeled cells occurred in peri-infarction and infarction of parietal region at day14 and peaked at day 21 when some Dil-labeled cell nodules were found in this region. During postischemic day 14-28, a significant decrease in labeled cell density in the ischemic ipsilateral subventricular zone was coincident with a significant increase in labeled cells density in the cortex (peri-infarction and infarction). Conclusion The results indicate that ependymal cells proliferate and migrate after focal cerebral ischemia in the adult rat brain.展开更多
基金supported by the Chinese Academy of Sciences(Project No.KZCX2-209-01)National Science Foundation(Project No.40276015)Guangdong Province Science Foundation(Project No.021561).
文摘The Red River Fault Zone is a gigantic slide-slip fault zone extending up to 1000km from Tibet to SouthChina Sea. It has been divided into the north, central and south segments according to the difference of thegeometry, kinetics, and seismicity on the land, but according to the contacted relationship between the old pre-Cenozoic block in Indochina Peninsula and the South China block, the Red River Fault Zone was divided into two parts extending from land to ocean, the north and south segments. Since the Tertiary, the Red River Fault Zone suffered first the sinistral movement and then the dextral movement. The activities of the north and the south segments were different. Based on the analysis of earthquakes and focal mechanism solutions,earthquakes with the focus depths of 0-33km are distributed over the whole region and more deep earthquakes are distributed on the northeastern sides of the Red River fault. Types of faulting activities are the thrust in the northwest, the normal in the north and the strike-slip in the south, with the odd type, viz. the transition type, in the other region. These show the Red River Fault Zone and its adjacent region suffered the extruding force in NNW direction and the normal stress in NEE direction and it makes the fault in the region extrude-thrust,horizontal strike-slip and extensional normal movement.
基金The research was supported by the key project entitled"Seismic Safety Evaluation and Seismic Structure Study"under the 10th Five-Year Plan of China EarthquakeAdministration
文摘Based on the results of focal mechanism solutions in southeastern areas of China (south of 34°N and east of 105°E), this article analyzes the correlation of focal mechanism solutions with seismogenic structures of moderate strong earthquakes and the direction of potential source zones. The data show that the nodal planes of focal mechanism solutions and the principle stresses in southern China are of predominantly similar directions, most of the solutions for M≥4.0 earthquakes correspond to the main structure directions as well as the directions of potential source zones. The statistical results of multiple small earthquakes concerning nodal planes and main stress axes are also reliable for determining the direction of potential source zones. According to the analysis of focal mechanism solutions, long-axis direction of isoseismals distribution of aftershocks, geologic structures, and seismic activity in two areas of the M_S6.1 earthquake in the south Yellow Sea in 1996 and the M_S5.2 earthquake in Fujian in 1997, the potential source zone division is discussed.
基金supported by National Key Basic Research 973bNational Scientific technology support plan (2006BAC01B02-01-01).
文摘The seismicity of Longrnenshan fault zone and its vicinities before the 12 May 2008 Wenchuan Ms8.0 earthquake is studied. Based on the digital seismic waveform data observed from regional seismic networks and mobile stations, the focal mechanism solutions are determined. Our analysis results show that the seismicities of Longmenshan fault zone before the 12 May 2008 Wenchuan earthquake were in stable state. No obvious phenomena of seismic activity intensifying appeared. According to focal mechanism solutions of some small earthquakes before the 12 May 2008 Wenchuan earthquake, the direction of principal compressive stress P-axis is WNW-ESE. The two hypocenter fault planes are NE-striking and NW-striking. The plane of NE direction is among N50°-70°E, the dip angles of fault planes are 60°-70° and it is very steep. The faultings of most earthquakes are dominantly characterized by dip-slip reverse and small part of faultings present strike-slip. The azimuths of principal compressive stress, the strikes of source fault planes and the dislocation types calculated from some small earthquakes before the 12 May 2008 Wenchuan earthquake are in accordance with that of the main shock. The average stress field of micro-rupture along the Longmenshan fault zone before the great earthquake is also consistent with that calculated from main shock. Zipingpu dam is located in the east side 20 km from the initial rupture area of the 12 May 2008 Wenchuan earthquake. The activity increment of small earthquakes in the Zipingpu dam is in the period of water discharging. The source parameter results of the small earthquakes which occurred near the initial rupture area of the 12 May 2008 Wenchuan earthquake indicate that the focal depths are 5 to 14 km and the source parameters are identical with that of earthquake.
基金funded by the grants of 100-talent program of Chinese Academy of Sciencesto L. Baithe US National Science Foundation (EAR-0944167) to J. Ritsemathe National Natural Science Foundation of China (40930317) to J. Zhao
文摘We estimate the focal depths and fault plane solutions of 46 moderate earthquakes in the Himalayan- Tibetan region by modeling the broadband waveforms of teleseismic P waves. The depths of 38 of these earth- quakes range between 0-40 km, with a peak at -5 km. One earthquake is located within the lower crust of the Indian shield. The remaining eight earthquakes occurred between depths of 80 -120 km and are all located in the Pamir-Hindu Kush and the Indo-Myanmar deep seismic zones. None of the earthquakes outside these deep seismic zones are located in the mantle. Global centroid moment tensor （CMT） solutions indicate that most earthquakes in northern Tibet and northern India had thrust-faulting mechanisms and that normal and strike-slip faulting earthquakes occurred primarily in central Tibet. These mechanisms are consistent with the predominantly NNW-SSE compression in the direction of current Himalayan-Tibetan continental collision.
文摘Objective Ependymal cells are thought to be the primary source of neural stem cells in the adult central nervous system. The purpose of this study is to examine spatial and temporal profiles of ependymal cell proliferation and migration after focal cerebral ischemia. Methods Eighty male Sprague Dawley rats underwent permanent middle cerebral artery occlusion after injection of 10 μL of 0.2% Dil into the lateral ventricle. Rats were sacrificed and brain sections were acquired for pathological evaluation and laser confocal imaging at day 1,3,7,11,14,21 and 28 after ischemia. Results The density of Dil-labeled cells in the ischemic ipsilateral subventricular zone was significantly higher than that in the control group and these labeled cells dispersed in the ischemic ipsilateral subventricular zone and/or were located in ependyma from day 1 to 11. In the ischemic ipsilateral cortex, some Dil-labeled cells occurred in peri-infarction and infarction of parietal region at day14 and peaked at day 21 when some Dil-labeled cell nodules were found in this region. During postischemic day 14-28, a significant decrease in labeled cell density in the ischemic ipsilateral subventricular zone was coincident with a significant increase in labeled cells density in the cortex (peri-infarction and infarction). Conclusion The results indicate that ependymal cells proliferate and migrate after focal cerebral ischemia in the adult rat brain.
