The Kunlunshan Mountain Ms8.1 earthquake, occurred in Nov.14, 2001, is the first event with magnitude more than 8 in the China earthquake monitoring history, specifically at the beginning of digital techniques in prec...The Kunlunshan Mountain Ms8.1 earthquake, occurred in Nov.14, 2001, is the first event with magnitude more than 8 in the China earthquake monitoring history, specifically at the beginning of digital techniques in precursor monitoring networks. Any investigation of recorded data on this earthquake is very important for testing the operation of the digital monitoring networks and understanding the preparation, occurrence, and adjustment of stress/strain of strong continental earthquakes. In this paper we investigated the coseismic response changes of well water level of groundwater and volume strain meter of bore hole in digital earthquake monitoring network of Capital area and its vicinity, due to the Nov.14, 2001 Ms8.1 Kunlun Mountain earthquake. The responding time, shapes or manners, amplitudes, and lasting time of well water level and strain-meters to seismic wave are studied in comparison. Then we discussed the possibility that the response changes of groundwater to strong distant earthquakes can be understood as one kind of observing evidence of stress/strain changes induced by distant earthquake.展开更多
Usual ductile shear zone has relatively high strain magnitude. However,for high-grade metamorphic rocks in Daqingshan area,the related strain is very low with weakly developed lineation. Significantly,the finite strai...Usual ductile shear zone has relatively high strain magnitude. However,for high-grade metamorphic rocks in Daqingshan area,the related strain is very low with weakly developed lineation. Significantly,the finite strain type with a K-value slightly lower than 1 and is characterized by compressional strain. Because the special tectonic environment with high temperature,the percentage of melt is relatively higher,which leads to a series of microscopic phenomenon such as multi-grain quartz bands,feldspar three edges equilibrium-like texture,granular flow,etc. As a consequence,the tectonites in the studied area illustrate a unique character: obvious rheological meso-deformation structure but with very weak intracrystalline micro-deformation.展开更多
Extensional basins include mainly grabens and half grabens displaced along alower detachment. Based on area balance theory, there is a linear relationship between a height ofregional and the lower detachment h on the ...Extensional basins include mainly grabens and half grabens displaced along alower detachment. Based on area balance theory, there is a linear relationship between a height ofregional and the lower detachment h on the outside of the basin and 'lost area S' from the regionalin the basin. The pre-growth beds above lower detachment are of the same extensional displacement sothat an 'S-h diagram' can be used to determine the depth to lower detachment and to calculate thetotal extensional displacement of the beds above the lower detachment. The extensional displacementis dominated by the heave of various scale normal faults. The displacement of obvious faults can beimmediately figured out from the measured bed-length. The requisite extension calculated by areabalance is the layer-parallel strain, which could be accommodated by displacement on sub-resolutionfaults. Accordingly, the layer-parallel strain can help us predict the magnitude and distribution ofsub-resolution faults on the basis of analysis of the structural style and rheological behavior.展开更多
In this paper, we collect 6 361 waveform data to calculate the shear wave splitting parameters from a regional seismic network of 22 digital stations in Yunnan and its adjacent area from July 1999 to June 2005. By usi...In this paper, we collect 6 361 waveform data to calculate the shear wave splitting parameters from a regional seismic network of 22 digital stations in Yunnan and its adjacent area from July 1999 to June 2005. By using the cross-correlation method, 64 splitting events of 16 stations are processed. We also collect the splitting results of eight earthquake sequences to present the characteristics of shear wave splitting in Yunnan and its adjacent areas. The orientations of maximum principal compressive stress of three sub-regions in this area are derived from the CMT focal mechanism solutions of 43 moderate-strong earthquakes provided by Harvard University by the P axis azimuth-averaging method. The principal strain rate at each observatory is deduced from the observations of Crustal Movement Observation Network of China during the period from 1999 to 2004. In addition, the data of Pn aniso- tropy and SKS splitting of Yunnan and its adjacent areas are also collected. We have discovered from this study that the continental lithosphere, as a main seismogenic environment for strong earthquake, can be divided into blocks laterally; the mechanical behavior of lithosphere varies with depth and can be divided into different layers in the vertical orientation; the information of crustal deformation obtained from GPS might be affected by the type of blocks, since there are different types of active blocks in Yunnan and its adjacent areas; the shear wave splitting in this region might be affected mainly by the upper crust or even the surface tectonics.展开更多
In the western Dabie Mountain area, the eclogites have similar compositions and tectonic environment, which could be contrastively researched. Except for the reservation of the early structural deformation inside and ...In the western Dabie Mountain area, the eclogites have similar compositions and tectonic environment, which could be contrastively researched. Except for the reservation of the early structural deformation inside and outside of the eclogite lens, there is no obvious difference between the characteristics of the foliation and lineation in the eclogite lens from the one in surrounding region. So this paper concludes that the eclogites or blueschists (high pressure metamorphic rocks, i. e. HPM) are basically situated in the original position. The eclogites are mostly superposed by the ductile shear zone and show the feature of structural displacement, but so far we have not discovered any large scale structural zone to uplift eclogite return. Based on the analyses of finite strain measure, petrofabric analysis and TEM image for some minerals such as quartz and garnet, we could efficiently know the deforming characteristics of the eclogite in the prophase and anaphase of the main deforming epoch, and finally determine the forming condition of eclogite according to the strain and the differential stress. This paper puts forward preliminary conclusion that some HPM rocks could be formed by the deep layer embedding and local stress concentration in the process of regional metamorphism.展开更多
基金supported by Natural Science Foundation of China(41274061 and 40374019)
文摘The Kunlunshan Mountain Ms8.1 earthquake, occurred in Nov.14, 2001, is the first event with magnitude more than 8 in the China earthquake monitoring history, specifically at the beginning of digital techniques in precursor monitoring networks. Any investigation of recorded data on this earthquake is very important for testing the operation of the digital monitoring networks and understanding the preparation, occurrence, and adjustment of stress/strain of strong continental earthquakes. In this paper we investigated the coseismic response changes of well water level of groundwater and volume strain meter of bore hole in digital earthquake monitoring network of Capital area and its vicinity, due to the Nov.14, 2001 Ms8.1 Kunlun Mountain earthquake. The responding time, shapes or manners, amplitudes, and lasting time of well water level and strain-meters to seismic wave are studied in comparison. Then we discussed the possibility that the response changes of groundwater to strong distant earthquakes can be understood as one kind of observing evidence of stress/strain changes induced by distant earthquake.
基金Supported by Project of National Natural Science Foundation of China(Nos.41230206,41340032)
文摘Usual ductile shear zone has relatively high strain magnitude. However,for high-grade metamorphic rocks in Daqingshan area,the related strain is very low with weakly developed lineation. Significantly,the finite strain type with a K-value slightly lower than 1 and is characterized by compressional strain. Because the special tectonic environment with high temperature,the percentage of melt is relatively higher,which leads to a series of microscopic phenomenon such as multi-grain quartz bands,feldspar three edges equilibrium-like texture,granular flow,etc. As a consequence,the tectonites in the studied area illustrate a unique character: obvious rheological meso-deformation structure but with very weak intracrystalline micro-deformation.
文摘Extensional basins include mainly grabens and half grabens displaced along alower detachment. Based on area balance theory, there is a linear relationship between a height ofregional and the lower detachment h on the outside of the basin and 'lost area S' from the regionalin the basin. The pre-growth beds above lower detachment are of the same extensional displacement sothat an 'S-h diagram' can be used to determine the depth to lower detachment and to calculate thetotal extensional displacement of the beds above the lower detachment. The extensional displacementis dominated by the heave of various scale normal faults. The displacement of obvious faults can beimmediately figured out from the measured bed-length. The requisite extension calculated by areabalance is the layer-parallel strain, which could be accommodated by displacement on sub-resolutionfaults. Accordingly, the layer-parallel strain can help us predict the magnitude and distribution ofsub-resolution faults on the basis of analysis of the structural style and rheological behavior.
基金National Program on Key Basic Projects(2004CB418406)Social Commonweal Research Project of the Ministry ofScience and Technology(2004DIA3J010)Joint Seismological Science Foundation of China(106016).
文摘In this paper, we collect 6 361 waveform data to calculate the shear wave splitting parameters from a regional seismic network of 22 digital stations in Yunnan and its adjacent area from July 1999 to June 2005. By using the cross-correlation method, 64 splitting events of 16 stations are processed. We also collect the splitting results of eight earthquake sequences to present the characteristics of shear wave splitting in Yunnan and its adjacent areas. The orientations of maximum principal compressive stress of three sub-regions in this area are derived from the CMT focal mechanism solutions of 43 moderate-strong earthquakes provided by Harvard University by the P axis azimuth-averaging method. The principal strain rate at each observatory is deduced from the observations of Crustal Movement Observation Network of China during the period from 1999 to 2004. In addition, the data of Pn aniso- tropy and SKS splitting of Yunnan and its adjacent areas are also collected. We have discovered from this study that the continental lithosphere, as a main seismogenic environment for strong earthquake, can be divided into blocks laterally; the mechanical behavior of lithosphere varies with depth and can be divided into different layers in the vertical orientation; the information of crustal deformation obtained from GPS might be affected by the type of blocks, since there are different types of active blocks in Yunnan and its adjacent areas; the shear wave splitting in this region might be affected mainly by the upper crust or even the surface tectonics.
文摘In the western Dabie Mountain area, the eclogites have similar compositions and tectonic environment, which could be contrastively researched. Except for the reservation of the early structural deformation inside and outside of the eclogite lens, there is no obvious difference between the characteristics of the foliation and lineation in the eclogite lens from the one in surrounding region. So this paper concludes that the eclogites or blueschists (high pressure metamorphic rocks, i. e. HPM) are basically situated in the original position. The eclogites are mostly superposed by the ductile shear zone and show the feature of structural displacement, but so far we have not discovered any large scale structural zone to uplift eclogite return. Based on the analyses of finite strain measure, petrofabric analysis and TEM image for some minerals such as quartz and garnet, we could efficiently know the deforming characteristics of the eclogite in the prophase and anaphase of the main deforming epoch, and finally determine the forming condition of eclogite according to the strain and the differential stress. This paper puts forward preliminary conclusion that some HPM rocks could be formed by the deep layer embedding and local stress concentration in the process of regional metamorphism.
