A study on stress magnitude in the source regionof American 1992 Landers earthquake
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摘要: 给出了根据地震前后应力轴偏转、地震应力降和地震前后相对主应力大小，计算震源处应力量值的方法．并将该方法运用于兰德斯地震的霍姆斯特德谷断层段，获得了该子断层10 km深度处震前最大、中间和最小主应力的量值分别为271，266 MPa和259 MPa；震前断层面上的正应力和剪切应力分别为265 MPa和6.2 MPa； 震后断层面上的正应力和剪切应力分别为266 MPa和1.6 MPa．研究结果表明，地震发生后，正压应力增大，有利于破裂的终止；震前剪切应力大于震后剪切应力，且它们的差基本上与应力降大小相近. 从研究结果可以看出，虽然地下压应力很大，但是差应力并不大， 投影到断层面上的剪切应力也较小．Abstract: This study presented a method for estimating stress magnitude in earthquake source region based on rotation of stress axes, seismic stress drop and relative magnitude of principle stresses. We applied this method to the Homestead Valley fault segment of the 1992 Landers earthquake, and obtained the compressive, intermediate and extensional principal stress before the mainshock being 271, 266 MPa and 259 MPa, respectively. The preseismic normal and shear stress are 265 MPa and 6.2 MPa, respectively. The post-seismic normal and shear stress are 266 MPa and 1.6 MPa, respectively. The result shows that normal stress increase after the mainshock would have benefited to the rupture termination. The pre-seismic shear stress is higher than that of post-seismic one, and their difference corresponds to the stress drop approximately. The estimated underground compressive stress is very large, but the differential stress is small, and the shear-stress projected on to the fault plane is also relatively small.
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期刊类型引用(3)
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