中国甘肃昌马断裂带及其现代活动
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摘要
昌马断裂带是是青藏高原北部一条活动强烈的左旋走滑断裂带。它表现为重力、航磁、地壳厚度的综合异常梯度带，属于断面陡、切割深的超岩石圈断裂。昌马断裂带由１２条长４公里至１８公里不等的不连续的主断层和４条次级断层组成，可划分为东、中、西三大段落。断裂的水平位移和滑动速率具有分段性，全新世以来，东、中、西三段的左旋水平滑动速率分别为４．１毫米／年，２．６毫米／年和１．５毫米／年。北东东、北北西和北西西三个方向断层的位移具有分级特征，不同级别的位移具有良好的同步性。全新世以来北东东、北北西和北西西三个方向断层的水平滑动速率分别为４．１毫米／年、３．８毫米／年和２．７毫米／年。白垩纪以来，昌马断裂呈天平式运动，显示了枢纽断裂运动特征，枢纽轴位于断裂中段。昌马地震震源破裂性质及其反映的震源应力场与地震破裂带的破裂性质及其反映的构造应力场不一致。昌马地震震源机制解反映了北北西～南南东挤压，作用应力近于水平的震源应力场；昌马地震破裂带的变形组合反映了东北～南西挤压的构造应力场。昌马地震破裂带长１２０公里，分为东部正走滑段、中部逆走滑段和西部尾端破裂段，显示了多个水平位移峰值。全新世以来，沿昌马断裂发生了６次强震事件，强震复发?
The Changma Fault Zone (CFZ) is the most active left lateral strike slip one at the north of Qinghai-Tibetan plateau. It appeared as a comprehensive anomalous gradient zones with regional gravity, aeromagnetism and the thickness of crust. It is recognized to be the ultra-lithosphere fault zone.The CFZ is comprised of 12 uncontinuous main and 4 subgrade shear faults,having lengths of 418km. The CFZ might be divided into the east, middle and west 3 segments. There existed the character of segmentation on the horizontal slips and slip rates of the fault zone. During Holocene the left lateral horizontal slip rates of the east, middle and west 3 segments were 4.1 mm/yr, 2.6 mm/yr and 1.5 mm/yr respectively. The displacements of NEE, NNW and NWW faults are provided with the feature of grade, the displacements of different grades possessed with fair synchronism. During Holocene the horizontal slip rates of NEE, NNW and NWW faults were 4.1 mm/yr, 3.8 mm/yr and 2.7 mm/yr respectively. Since Cretaceous, the CFZ had emerged the movements of balance fashion, appearing the feature of movement of hinge fault, the pivotal axis is located at the middle segment of the CFZ. The character of the focal rupture of Changma earthquake and its reflected focal stress field are not coincided with the character of the surface rupture zone and its reflected tectonic stress field. The focal mechanism solution of Changma earthquake reflected the focal stress field of NNW-SSE compression, while the deformation combination of the surface rupture zone reflected the tectonic stress field of the NE-SW compression.The Changma earthquake rupture zone having length of 120km is divided into 3 segments, i. e, eastern normal strike slip segment, middle reverse strike slip segment and the western emphenage rupture segment. Horizontal slips indicated multiple peak values along the rupture zone. During Holocene 6 surface-rupture earthquakes have occurred along the CFZ. The reccurrence interrvals for magnitude of Ms= 7 -7.5 are 2000 years. The model of the surface rupture earthquakes along CFZ was conformable to the characteristic earthquake one.
The Changma Fault Zone (CFZ) is the most active left lateral strike slip one at the north of Qinghai-Tibetan plateau. It appeared as a comprehensive anomalous gradient zones with regional gravity, aeromagnetism and the thickness of crust. It is recognized to be the ultra-lithosphere fault zone.The CFZ is comprised of 12 uncontinuous main and 4 subgrade shear faults,having lengths of 418km. The CFZ might be divided into the east, middle and west 3 segments. There existed the character of segmentation on the horizontal slips and slip rates of the fault zone. During Holocene the left lateral horizontal slip rates of the east, middle and west 3 segments were 4.1 mm/yr, 2.6 mm/yr and 1.5 mm/yr respectively. The displacements of NEE, NNW and NWW faults are provided with the feature of grade, the displacements of different grades possessed with fair synchronism. During Holocene the horizontal slip rates of NEE, NNW and NWW faults were 4.1 mm/yr, 3.8 mm/yr and 2.7 mm/yr respectively. Since Cretaceous, the CFZ had emerged the movements of balance fashion, appearing the feature of movement of hinge fault, the pivotal axis is located at the middle segment of the CFZ. The character of the focal rupture of Changma earthquake and its reflected focal stress field are not coincided with the character of the surface rupture zone and its reflected tectonic stress field. The focal mechanism solution of Changma earthquake reflected the focal stress field of NNW-SSE compression, while the deformation combination of the surface rupture zone reflected the tectonic stress field of the NE-SW compression.The Changma earthquake rupture zone having length of 120km is divided into 3 segments, i. e, eastern normal strike slip segment, middle reverse strike slip segment and the western emphenage rupture segment. Horizontal slips indicated multiple peak values along the rupture zone. During Holocene 6 surface-rupture earthquakes have occurred along the CFZ. The reccurrence interrvals for magnitude of Ms= 7 -7.5 are 2000 years. The model of the surface rupture earthquakes along CFZ was conformable to the characteristic earthquake one.
引文
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