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利用龙门山断裂带及其附近的GPS观测资料,分析了2013年四川芦山“4.20”7.0级地震震前变形场及同震位移场特征.结合震前GPS资料分析认为,这次地震以逆冲破裂为主兼有少量左旋错动,且破裂可能未达地表,发震断层很可能为灌县-安县断裂东侧的一条断层.具体结果:①发生芦山地震的龙门山断裂带南段一直处于闭锁状态,汶川地震后南东向挤压应变积累速率明显加大,且主压应变率方向使发震断层呈逆冲兼左旋剪切变形状态,表明汶川地震的发生加速了此次芦山地震的孕育过程;②GPS检测出同震位移的范围在垂直发震断裂带方向约为230km、平行发震断裂带约为100km,其中同震位移超过10mm的测点分布于垂直发震断层方向的100km范围内;③同震位移场在较大范围主要表现为发震断层逆冲错动的应变释放特征,但在靠近发震断层约70km范围逆冲位移显著偏小,不符合断层错动的位移衰减特征,推断地震破裂未达地表;④在靠近发震断层的上盘约50km范围显示有典型的断层左旋错动位移衰减特征.
Using the Longmen Shan fault zone and its GPS observations, the deformation field and the coseismic displacement field before the 7.0 magnitude earthquake in Lushan, Sichuan Province, China, are analyzed. Combined with the GPS data before the earthquake, it is considered that the earthquake There are a few thrust faults and a little left-hand-slip fault, and the rupture may not reach the surface, and the seismogenic fault is probably a fault on the east side of Guanxian-Anxian fault.Results: ①Lanmen Shan fault It has been in a locked state. After the Wenchuan earthquake, the accumulation rate of compressional strain in the south east direction obviously increases, and the direction of the principal compressive strain rate causes the seismogenic faults to show thrusting and left-lateral shear deformation. This indicates that the occurrence of the Wenchuan earthquake accelerated the current Lushan The range of coseismic displacements detected by GPS is about 230km in the vertical seismogenic fault zone and about 100km in the parallel seismogenic fault zone. The measuring points with the coseismic displacements exceeding 10mm are distributed in the direction of the vertical seismogenic fault (3) The co-seismic displacement field mainly shows the strain release characteristic of seismogenic fault thrusting in a large area, but the thrust displacement is obviously smaller in the range of about 70km near the seismogenic fault and does not accord with the fault dislocation Displacement attenuation characteristics inferred earthquake rupture less than the surface; ④ in the range of approximately 50km near the disc seismic fault display typical fault dislocation left displacement attenuation characteristics.