Mao'ershan region is a representative natural secondary forested region in the eastern mountainous region, northeast of China.. Under the support of ARC/INFO and GIS technology, the landscape shape and fragment in...Mao'ershan region is a representative natural secondary forested region in the eastern mountainous region, northeast of China.. Under the support of ARC/INFO and GIS technology, the landscape shape and fragment indices of Mao'ershan experimental plantation were studied by combining the forest type map (1:10000), which was drawn from the aerial photographs (1999), field investigation (1999) and soil utilized map (1:10000). The results showed that the shape index and shape fragment index of natural landscape were higher than those of artificial landscapes and landscape patch fragment index depended on the number of patches. The natural forest had complex shape, suffering little jamming, and its shape index was higher than that of artificial forest. The manual controlled landscape (e.g. nursery, cropland and cutting blank) had regular shape, and its shape index was smaller. The fragment index of patches in natural forest was higher than that of artificial forest. The soft broad-leaved had the highest fragment index of patch amount.展开更多
This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long activ...This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long active fault zone with documented intraplate seismicity situated on the NE margin of the Bohemian Massif(the Czech Republic). The tectonic history of the SMFZ as well as its kinematic development has been rather complicated and not quite understood. A field structural investigation was carried out in extensive surroundings of the fault zone. The fault-slip data were collected in a number of natural outcrops and quarries with the aim at establishing a robust and field-constrained model for local brittle structural evolution of the studied area. A paleostress analysis was calculated using the collected fault-slip data inversion. The T-Tecto software was utilized for semiautomatic separation of the paleostress phases. Simultaneously three methods of data separation were employed:(1) the Gauss inverse method,(2) the Visualization of Gauss object Function, and(3) the frequency analysis. Within the fault zone multiphase movements were observed on various types of faults as well as wide range of the kinematic indicators orientations. The frequency analysis confirmed the multiphase history of the SMFZ. The calculated tectonic phases were divided according to their relative age as constrained by cross cutting relationships and, where observed, multiple striations on a single fault plane and classified from the oldest to the younger. Data separation and inversion usingT-Tecto software with the Gauss inverse method revealed four different stress phases which are 3 strike-slip stress regimes and one compressional regime. The strike-slip regimes are characterized by σ1 trending NW-SE(43), NNE-SSW(18), ENE-WSW(76) and the compressional one by σ1 trending W-E(26). First, compression occurred parallel to the SMFZ supposedly during the Variscan period. Second, compression at an angle of 60° to general direction of the SMFZ yielded right-lateral movement along the fault zone. This is considered to have occurred during the late-Variscan and post-Variscan period. Third, compression in the W-E direction with almost vertical extension led to reverse movement along the fault zone. This is considered to have occurred during Cenozoic. Fourth, compression almost perpendicular to the SMFZ led to left-lateral transpression along the SMFZ. This is considered to have occurred during Quaternary.展开更多
Based on the analyses of grouped activity features of deep-focus (M≥6.0) and shallow-focus (M S≥5.0) earthquakes in the Northeast China region, the time-space correlation between deep focus “strong earthquake group...Based on the analyses of grouped activity features of deep-focus (M≥6.0) and shallow-focus (M S≥5.0) earthquakes in the Northeast China region, the time-space correlation between deep focus “strong earthquake group" and shallow focus “strong earthquake group" have been studied. The study was mainly on the characteristics of earthquake distribution on the collision zone between the west Pacific plate and the Eurasian plate and on its relations to the morphological feature of the western Pacific subduction zone. Moreover, emphasis was laid on analysis of the effect of the west Pacific plate on the seismicity of Eurasian plate. It is shown that in the region where the west Pacific plate subducts at low angles, the seismicity on the plate collision zone is strong, the effect of plate subduction on Eurasian continent is strong too, and the subduction zone is under a state of high compressional stress. However, in the region where the west Pacific plate subducts at high angles, the seismicity along the plate collision zone is weak, the effect of plate subduction on Eurasian continent is weak too, and the tensile stress produced by the subduction zone at depth is enhanced. We therefore propose that the seismicity in the northeast China region will enter an active period of shallow “strong earthquake group" in the future 10 years. In the period, six earthquakes of M S≥5.0 may occur. Therefore, the work of earthquake monitoring and prediction in this region shall be strengthened.展开更多
First of all,using the GPS velocity field from campaign GPS measurements implemented by CMONC( C hina Crustal Movement Observation) a nd TEONC( C hina Tectonic Environment Observation Networks) u p to 2013, w e analyz...First of all,using the GPS velocity field from campaign GPS measurements implemented by CMONC( C hina Crustal Movement Observation) a nd TEONC( C hina Tectonic Environment Observation Networks) u p to 2013, w e analyzed the background of regional crustal horizontal movement and deformation before the M S7. 3 Yutian,Xinjiang earthquake on February 12,2014. Then,by comparing this to the vertical movement from leveling measurements,we studied the crustal movement deformation and the state of strain accumulation on the northeastern edge of Qinghai-Tibetan block.Finally,we investigated the possible effects on the earthquake activity of the northeastern edge of Tibet from the M S7. 3 Yutian earthquake. The result indicates that,the M S7. 3Yutian earthquake occurred against the background of strong tectonic movement and intensive intracontinental crustal differential movement on the edges of tectonic blocks in western China,and also that it happened in the period of the strong tectonic stress field in Qinghai-Tibetan block and its edges. The sinistral strike-slip and stress transfer of the Yutian M S7. 3 earthquake may accelerate the rupture of fault segments with high strain accumulation at the northeastern edge of Qinghai-Tibetan block( especially in Qilian Mountain fault zone,and border area of Gansu,Qinghai and Sichuan provinces on the south of western Qinling).展开更多
基金This paper was supported by National Key Technologies R&D Program of China during the 10th Five-Year Plan Period (2002BA515B040).
文摘Mao'ershan region is a representative natural secondary forested region in the eastern mountainous region, northeast of China.. Under the support of ARC/INFO and GIS technology, the landscape shape and fragment indices of Mao'ershan experimental plantation were studied by combining the forest type map (1:10000), which was drawn from the aerial photographs (1999), field investigation (1999) and soil utilized map (1:10000). The results showed that the shape index and shape fragment index of natural landscape were higher than those of artificial landscapes and landscape patch fragment index depended on the number of patches. The natural forest had complex shape, suffering little jamming, and its shape index was higher than that of artificial forest. The manual controlled landscape (e.g. nursery, cropland and cutting blank) had regular shape, and its shape index was smaller. The fragment index of patches in natural forest was higher than that of artificial forest. The soft broad-leaved had the highest fragment index of patch amount.
基金supported by the Grant Agency of Charles University (43-258020)the Czech Science Foundation (250/09/1244)the Institute of Rock Structure and Mechanics AS CR, v.v.i. (A VOZ30460519)
文摘This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long active fault zone with documented intraplate seismicity situated on the NE margin of the Bohemian Massif(the Czech Republic). The tectonic history of the SMFZ as well as its kinematic development has been rather complicated and not quite understood. A field structural investigation was carried out in extensive surroundings of the fault zone. The fault-slip data were collected in a number of natural outcrops and quarries with the aim at establishing a robust and field-constrained model for local brittle structural evolution of the studied area. A paleostress analysis was calculated using the collected fault-slip data inversion. The T-Tecto software was utilized for semiautomatic separation of the paleostress phases. Simultaneously three methods of data separation were employed:(1) the Gauss inverse method,(2) the Visualization of Gauss object Function, and(3) the frequency analysis. Within the fault zone multiphase movements were observed on various types of faults as well as wide range of the kinematic indicators orientations. The frequency analysis confirmed the multiphase history of the SMFZ. The calculated tectonic phases were divided according to their relative age as constrained by cross cutting relationships and, where observed, multiple striations on a single fault plane and classified from the oldest to the younger. Data separation and inversion usingT-Tecto software with the Gauss inverse method revealed four different stress phases which are 3 strike-slip stress regimes and one compressional regime. The strike-slip regimes are characterized by σ1 trending NW-SE(43), NNE-SSW(18), ENE-WSW(76) and the compressional one by σ1 trending W-E(26). First, compression occurred parallel to the SMFZ supposedly during the Variscan period. Second, compression at an angle of 60° to general direction of the SMFZ yielded right-lateral movement along the fault zone. This is considered to have occurred during the late-Variscan and post-Variscan period. Third, compression in the W-E direction with almost vertical extension led to reverse movement along the fault zone. This is considered to have occurred during Cenozoic. Fourth, compression almost perpendicular to the SMFZ led to left-lateral transpression along the SMFZ. This is considered to have occurred during Quaternary.
文摘Based on the analyses of grouped activity features of deep-focus (M≥6.0) and shallow-focus (M S≥5.0) earthquakes in the Northeast China region, the time-space correlation between deep focus “strong earthquake group" and shallow focus “strong earthquake group" have been studied. The study was mainly on the characteristics of earthquake distribution on the collision zone between the west Pacific plate and the Eurasian plate and on its relations to the morphological feature of the western Pacific subduction zone. Moreover, emphasis was laid on analysis of the effect of the west Pacific plate on the seismicity of Eurasian plate. It is shown that in the region where the west Pacific plate subducts at low angles, the seismicity on the plate collision zone is strong, the effect of plate subduction on Eurasian continent is strong too, and the subduction zone is under a state of high compressional stress. However, in the region where the west Pacific plate subducts at high angles, the seismicity along the plate collision zone is weak, the effect of plate subduction on Eurasian continent is weak too, and the tensile stress produced by the subduction zone at depth is enhanced. We therefore propose that the seismicity in the northeast China region will enter an active period of shallow “strong earthquake group" in the future 10 years. In the period, six earthquakes of M S≥5.0 may occur. Therefore, the work of earthquake monitoring and prediction in this region shall be strengthened.
基金sponsored by the Special Found for the Earthquake Scientific Research of China(201208009)the Earthquake Forecast and Prediction System Program of China Earthquake Administration in 2014
文摘First of all,using the GPS velocity field from campaign GPS measurements implemented by CMONC( C hina Crustal Movement Observation) a nd TEONC( C hina Tectonic Environment Observation Networks) u p to 2013, w e analyzed the background of regional crustal horizontal movement and deformation before the M S7. 3 Yutian,Xinjiang earthquake on February 12,2014. Then,by comparing this to the vertical movement from leveling measurements,we studied the crustal movement deformation and the state of strain accumulation on the northeastern edge of Qinghai-Tibetan block.Finally,we investigated the possible effects on the earthquake activity of the northeastern edge of Tibet from the M S7. 3 Yutian earthquake. The result indicates that,the M S7. 3Yutian earthquake occurred against the background of strong tectonic movement and intensive intracontinental crustal differential movement on the edges of tectonic blocks in western China,and also that it happened in the period of the strong tectonic stress field in Qinghai-Tibetan block and its edges. The sinistral strike-slip and stress transfer of the Yutian M S7. 3 earthquake may accelerate the rupture of fault segments with high strain accumulation at the northeastern edge of Qinghai-Tibetan block( especially in Qilian Mountain fault zone,and border area of Gansu,Qinghai and Sichuan provinces on the south of western Qinling).
