The process of mass movements and their consequent turbidity currents in large submarine canyons has been widely reported, however, little attention was paid to that in small canyons. In this paper, we document mass m...The process of mass movements and their consequent turbidity currents in large submarine canyons has been widely reported, however, little attention was paid to that in small canyons. In this paper, we document mass movements in small submarine canyons in the northeast of Baiyun deepwater area, north of the South China Sea （SCS）, and their strong effects on the evolution of the canyons based on geophysical data. Submarine canyons in the study area arrange closely below the shelf break zone which was at the depth of -500 m. Within submarine canyons, seabed surface was covered with amounts of failure scars resulted from past small-sized landslides. A complex process of mass transportation in the canyons is indicated by three directions of mass movements. Recent mass movement deposits in the canyons exhibit translucent reflections or parallel reflections which represent the brittle deformation and the plastic deformation, respectively. The area of most landslides in the canyons is less than 3 km2. The trigger mechanisms for mass movements in the study area are gravitational overloading, slope angle and weak properties of soil. Geophysical data indicate that the genesis of submarine canyons is the erosion of mass movements and consequent turbidity currents. The significant effects of mass movements on canyon are incision and sediment transportation at the erosion phases and fillings supply at the fill phases. This research will be helpful for the geological risk assessments and understanding the sediment transportation in the northern margin of the SCS.展开更多
The summer resort of Murree and adjoining areas is characterized by high degree of erosivity and erodibility due to both natural and man induced factors. This area is part of a young orogenic belt that is experiencing...The summer resort of Murree and adjoining areas is characterized by high degree of erosivity and erodibility due to both natural and man induced factors. This area is part of a young orogenic belt that is experiencing one of the world’s most rapid uplift rates, and is located in near vicinity of major thrust faults. Shear zones associated with still active faults, such as Murree Thrust and also the folding generated due to thrusting induce an inherited weakness and natural instability potential in the rocks of the Murree Hills. Ever increasing population pressure, deforestation, large\|scale construction works including a new township and a road network have further aggravated the problem. In order to study the landslides and other mass movement related problems in Murree, an area around the main town is selected for detailed analysis of the problem as it has been focus of major development and road construction work. This study is an attempt to prepare a preliminary hazard/landslide map along major road network, around Murree town to identify the unstable areas. Data collection during the fieldwork and its analysis were carried out on Geographic Information System (GIS) based on ILWIS format of the ITC, the Netherlands. Detailed study of a few selected landslides has also been conducted to understand the mechanism of failure and extent of damage.展开更多
The idea of research started with a crazy imaginary theory in the field of astrogeography, saying: We often taught ourselves and then convinced the students that the planet Earth moves despite not feeling the vibratio...The idea of research started with a crazy imaginary theory in the field of astrogeography, saying: We often taught ourselves and then convinced the students that the planet Earth moves despite not feeling the vibrations of traffic, and we listed successive scientific confirmations to indicate the rotation of the planet in a regular movement around its axis once every 24 hours, and it is running in another second movement around the sun once every 365¼ days, so are they only two movements, no more?! Is it possible for him to run at a regular speed in an additional direction?展开更多
Based on the horizontal movement velocities and their error estimations of 144 GPS stations in North China de-duced from the results obtained from multiple GPS measurements carried out in the period of 1992~2001, the ...Based on the horizontal movement velocities and their error estimations of 144 GPS stations in North China de-duced from the results obtained from multiple GPS measurements carried out in the period of 1992~2001, the horizontal deformation in the area is studied. The movements, entire deformations, local deformations, activity patterns and intensities along the boundary zones are derived. And then the risk of strong earthquake in the area is estimated. In the research, the horizontal displacement observations can be considered as the sum of three parts. The first part is the entire motion following Eurasian plate, which can be derived from NUVAL-IA model; the second part is the relative motions and deformations between the sub-tectonic blocks in the studied area, which can be derived from a set of displacement observations determined by the expanded QUAD method in the paper; the third part is the local deformations and errors in the sub-tectonic blocks, which can be described as the inhomoge-neous strains of the block. The method and results are introduced in detail in the paper.展开更多
Based on the high-accuracy data obtained from the GPS measurements carried out in 1992, 1995 and 1996, the isochronous active units with different kinematic property inside the North China area have been distinguished...Based on the high-accuracy data obtained from the GPS measurements carried out in 1992, 1995 and 1996, the isochronous active units with different kinematic property inside the North China area have been distinguished, 4 active units and 1 transition zone with distinct differential movement have been determined. They are Ordos-Yinshan unit, Yanshan unit, Shanxi-Hebei-Shandong (Jin-Ji-Lu) unit, Jiaodong-Liaoning-Shandong (Jiao-Liao-Lu) unit and Yanshan-Hebei (Yan-Ji) transition zone. The relative movements among the neighboring units in this period have been given. ① The compressive movement between Ordos-Yinshan unit and Yanshan unit is not obvious with an amount of 0.4(1.3 mm/a.②in-Ji-Lu unit moves E40(S off the Ordos-Yinshan unit and the magnitude is 4.4(1.0 mm/a. ③elative to the Yan-Ji transition zone of differential movement, Yanshan unit shifts W38(N with a value of 2.4(1.3 mm/a and Jin-Ji-Lu unit moves eastward 35( by south with an amount of 2.3(0.9 mm/a. ④Jin-Ji-Lu unit has a tensional left-lateral movement of 4.7(1.4 mm/a in the direction of E37(S relative to Yanshan unit. ⑤ Some area near Tanlu belt which is located in the southern part of Jin-Ji-Lu block has a southward movement 14( by west with a magnitude of 1.5(1.1 mm/a off the Jin-Ji-Lu unit. ⑥ Relative to Jin-Ji-Lu unit, Jiao-Liao-Lu unit has a trend of clockwise movement with a tensional right-lateral motion at the north end which neighbors Yanshan unit and a compressive motion at the south end. It should be noted that the errors given in the paper are obtained based on the divergence among the displacements of the sites in the unit, rather than the value calculated from the displacement error of the sites. The analyzed results indicate that: ① Shanxi tectonic zone and Yan-Ji transition zone are the major tectonic active zones to show the frame and magnitude of interior relative movement in North China area, and others are the secondary tectonic active zones; ② The complete horizontal deformation in the North China area is not homogeneous nor successive; ③ The kinetic model of North China area might be (mantle dragging plus boundary coupling(.展开更多
We analyzed the present state of crustal horizontal movement in part of the North China region using existing GPS re-observation data (1992-1995) and drew the following conclusions: (1) The monitored region appears to...We analyzed the present state of crustal horizontal movement in part of the North China region using existing GPS re-observation data (1992-1995) and drew the following conclusions: (1) The monitored region appears to be in tensile movement, with the trend of the principal tensile strain in the WNW-ESE direction; (2) There are two zones of higher maximum shear strain in the monitored region, namely, the Beijing zone and two sides of the Tancheng-Lujiang fault near Linyi; (3) There exists a striped compressive zone which stretches in the NNE-SSW direction; the zone of maximum planar compression is located in the Beijing zone; (4) The displacement field has an obvious zoned distribution.展开更多
In this paper, based on the large scale uplift, lateral inhomogeneity and low interface velocity along the Moho as well as the soft low velocity layer under it obtained from deep seismic sounding (DSS), we deduced tha...In this paper, based on the large scale uplift, lateral inhomogeneity and low interface velocity along the Moho as well as the soft low velocity layer under it obtained from deep seismic sounding (DSS), we deduced that the southern region of North China Plain is characterized by continental rift and abnormal mantle in the lithosphere.Summarizing geological and geophysical data, we try to state that the forming and developing of abnormal mantle and the intermittent activity of asthenosphere are the dynamic sources to dominate the geologic structure and tectonic movement in this region. We also point out that the research of deep process is important to probe timespace law of earthquake occurrence.展开更多
Global Positioning System (GPS) observations during four measurement campaigns from 1992 to 1999 are used in a study of the temporal and spatial variation characteristics of crustal deformation of active tectonic bloc...Global Positioning System (GPS) observations during four measurement campaigns from 1992 to 1999 are used in a study of the temporal and spatial variation characteristics of crustal deformation of active tectonic blocks in North China. The Euler vectors for these active blocks are determined on the basis of GPS velocities of a group relative stable points in 1992,1995,1996 and in 1996,1999 respectively. We have studied the relative motion between blocks at the boundaries and the intra block deformation field. We have also inverted the strain rate fields for these active blocks by bi cubic spline model based on the GPS velocity field. The results show that the intra block deformation rates are different from those in block boundary zones, and are also different in different periods; the deformational field is generally characterized by intra-block extension in North China.展开更多
基金The National Science and Technology Major Project under contract No.2011ZX05056-001-02
文摘The process of mass movements and their consequent turbidity currents in large submarine canyons has been widely reported, however, little attention was paid to that in small canyons. In this paper, we document mass movements in small submarine canyons in the northeast of Baiyun deepwater area, north of the South China Sea （SCS）, and their strong effects on the evolution of the canyons based on geophysical data. Submarine canyons in the study area arrange closely below the shelf break zone which was at the depth of -500 m. Within submarine canyons, seabed surface was covered with amounts of failure scars resulted from past small-sized landslides. A complex process of mass transportation in the canyons is indicated by three directions of mass movements. Recent mass movement deposits in the canyons exhibit translucent reflections or parallel reflections which represent the brittle deformation and the plastic deformation, respectively. The area of most landslides in the canyons is less than 3 km2. The trigger mechanisms for mass movements in the study area are gravitational overloading, slope angle and weak properties of soil. Geophysical data indicate that the genesis of submarine canyons is the erosion of mass movements and consequent turbidity currents. The significant effects of mass movements on canyon are incision and sediment transportation at the erosion phases and fillings supply at the fill phases. This research will be helpful for the geological risk assessments and understanding the sediment transportation in the northern margin of the SCS.
文摘The summer resort of Murree and adjoining areas is characterized by high degree of erosivity and erodibility due to both natural and man induced factors. This area is part of a young orogenic belt that is experiencing one of the world’s most rapid uplift rates, and is located in near vicinity of major thrust faults. Shear zones associated with still active faults, such as Murree Thrust and also the folding generated due to thrusting induce an inherited weakness and natural instability potential in the rocks of the Murree Hills. Ever increasing population pressure, deforestation, large\|scale construction works including a new township and a road network have further aggravated the problem. In order to study the landslides and other mass movement related problems in Murree, an area around the main town is selected for detailed analysis of the problem as it has been focus of major development and road construction work. This study is an attempt to prepare a preliminary hazard/landslide map along major road network, around Murree town to identify the unstable areas. Data collection during the fieldwork and its analysis were carried out on Geographic Information System (GIS) based on ILWIS format of the ITC, the Netherlands. Detailed study of a few selected landslides has also been conducted to understand the mechanism of failure and extent of damage.
文摘The idea of research started with a crazy imaginary theory in the field of astrogeography, saying: We often taught ourselves and then convinced the students that the planet Earth moves despite not feeling the vibrations of traffic, and we listed successive scientific confirmations to indicate the rotation of the planet in a regular movement around its axis once every 24 hours, and it is running in another second movement around the sun once every 365¼ days, so are they only two movements, no more?! Is it possible for him to run at a regular speed in an additional direction?
基金State Key Basic Research Development and Programming Project Mechanism and Prediction of Strong Continental Earthquakes (G1998040703).
文摘Based on the horizontal movement velocities and their error estimations of 144 GPS stations in North China de-duced from the results obtained from multiple GPS measurements carried out in the period of 1992~2001, the horizontal deformation in the area is studied. The movements, entire deformations, local deformations, activity patterns and intensities along the boundary zones are derived. And then the risk of strong earthquake in the area is estimated. In the research, the horizontal displacement observations can be considered as the sum of three parts. The first part is the entire motion following Eurasian plate, which can be derived from NUVAL-IA model; the second part is the relative motions and deformations between the sub-tectonic blocks in the studied area, which can be derived from a set of displacement observations determined by the expanded QUAD method in the paper; the third part is the local deformations and errors in the sub-tectonic blocks, which can be described as the inhomoge-neous strains of the block. The method and results are introduced in detail in the paper.
基金The National Key Basic Research Project Mechanism and Prediction of Continental Earthquakes (G1998040700).
文摘Based on the high-accuracy data obtained from the GPS measurements carried out in 1992, 1995 and 1996, the isochronous active units with different kinematic property inside the North China area have been distinguished, 4 active units and 1 transition zone with distinct differential movement have been determined. They are Ordos-Yinshan unit, Yanshan unit, Shanxi-Hebei-Shandong (Jin-Ji-Lu) unit, Jiaodong-Liaoning-Shandong (Jiao-Liao-Lu) unit and Yanshan-Hebei (Yan-Ji) transition zone. The relative movements among the neighboring units in this period have been given. ① The compressive movement between Ordos-Yinshan unit and Yanshan unit is not obvious with an amount of 0.4(1.3 mm/a.②in-Ji-Lu unit moves E40(S off the Ordos-Yinshan unit and the magnitude is 4.4(1.0 mm/a. ③elative to the Yan-Ji transition zone of differential movement, Yanshan unit shifts W38(N with a value of 2.4(1.3 mm/a and Jin-Ji-Lu unit moves eastward 35( by south with an amount of 2.3(0.9 mm/a. ④Jin-Ji-Lu unit has a tensional left-lateral movement of 4.7(1.4 mm/a in the direction of E37(S relative to Yanshan unit. ⑤ Some area near Tanlu belt which is located in the southern part of Jin-Ji-Lu block has a southward movement 14( by west with a magnitude of 1.5(1.1 mm/a off the Jin-Ji-Lu unit. ⑥ Relative to Jin-Ji-Lu unit, Jiao-Liao-Lu unit has a trend of clockwise movement with a tensional right-lateral motion at the north end which neighbors Yanshan unit and a compressive motion at the south end. It should be noted that the errors given in the paper are obtained based on the divergence among the displacements of the sites in the unit, rather than the value calculated from the displacement error of the sites. The analyzed results indicate that: ① Shanxi tectonic zone and Yan-Ji transition zone are the major tectonic active zones to show the frame and magnitude of interior relative movement in North China area, and others are the secondary tectonic active zones; ② The complete horizontal deformation in the North China area is not homogeneous nor successive; ③ The kinetic model of North China area might be (mantle dragging plus boundary coupling(.
基金This work was supported by Project No. 95-04-01-02 of the Key Problem Tackling Program under the 9th Five-Year Plan, State Commission of Science and Industry for National Defence and China Seismological Bureau.
文摘We analyzed the present state of crustal horizontal movement in part of the North China region using existing GPS re-observation data (1992-1995) and drew the following conclusions: (1) The monitored region appears to be in tensile movement, with the trend of the principal tensile strain in the WNW-ESE direction; (2) There are two zones of higher maximum shear strain in the monitored region, namely, the Beijing zone and two sides of the Tancheng-Lujiang fault near Linyi; (3) There exists a striped compressive zone which stretches in the NNE-SSW direction; the zone of maximum planar compression is located in the Beijing zone; (4) The displacement field has an obvious zoned distribution.
文摘In this paper, based on the large scale uplift, lateral inhomogeneity and low interface velocity along the Moho as well as the soft low velocity layer under it obtained from deep seismic sounding (DSS), we deduced that the southern region of North China Plain is characterized by continental rift and abnormal mantle in the lithosphere.Summarizing geological and geophysical data, we try to state that the forming and developing of abnormal mantle and the intermittent activity of asthenosphere are the dynamic sources to dominate the geologic structure and tectonic movement in this region. We also point out that the research of deep process is important to probe timespace law of earthquake occurrence.
文摘Global Positioning System (GPS) observations during four measurement campaigns from 1992 to 1999 are used in a study of the temporal and spatial variation characteristics of crustal deformation of active tectonic blocks in North China. The Euler vectors for these active blocks are determined on the basis of GPS velocities of a group relative stable points in 1992,1995,1996 and in 1996,1999 respectively. We have studied the relative motion between blocks at the boundaries and the intra block deformation field. We have also inverted the strain rate fields for these active blocks by bi cubic spline model based on the GPS velocity field. The results show that the intra block deformation rates are different from those in block boundary zones, and are also different in different periods; the deformational field is generally characterized by intra-block extension in North China.
