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根据作者与Hastie和Stacey提出的三维压磁效应模式计算方法,围绕1976年唐山大地震,计算了七种不同断层模式的压磁效应,比较了在不同磁纬处,走向滑动断层的不同走向、倾角和埋深在地面上所引起的压磁异常场。结果表明,震磁效应的可观测性同地震的破裂机制有着紧密的关系。断层倾角45°—60°对应着最佳观测条件,其压磁异常峰值可高达12nT;在最差观测条件时压磁异常量几乎无法测出,这时断层位于磁纬0°处,或走向为E-W,或埋深为10公里左右。在大多数模式中,垂直分量的异常略大于总强度异常,但在磁赤道附近可高达三倍左右。对唐山大地震的计算表明,压磁异常量约3—4nT,其异常大于1nT区域的线性尺度与断层长度之比仅为1.04—1.10。由于压磁场是地震过程的一种弱效应场,目前使用仪器的观测精度不够和磁测点的震中距过大,可能是未测出该地震明显的磁异常的原因。
According to the calculation method of three-dimensional piezomagnetic effect mode proposed by the author and Hastie and Stacey, the compression and magnetic effects of seven different fault modes are calculated around the Tangshan earthquake in 1976. Different directions of strike-slip faults at different magnetic latitudes are compared, Inclination and buried depth on the ground caused by the abnormal magnetic field. The results show that the observability of the seismic magnetic effect is closely related to the earthquake rupture mechanism. The fault dip angle 45 ° -60 ° corresponds to the best observation condition, and its peak value of anomalous pressure magnetic anomaly can reach as high as 12nT. In the worst observation condition, the anomalous amount of piezomagnetic anomaly can hardly be detected. At this time, the fault is located at 0 ° of latitude, EW, or depth of about 10 km. In most modes, the anomaly of the vertical component is slightly larger than the total intensity anomaly, but up to about three times the magnetic equator. Computation of the Tangshan earthquake shows that the anomalous amount of pressure magnetic anomaly is about 3-4nT, and the ratio of the linear scale to the fault length of anomalies larger than 1nT is only 1.04-1.10. Because the pressure magnetic field is a weak effect field of the earthquake process, the current observation accuracy of the instrument is not enough and the epicentral distance of the magnetic measuring point is too large, which may be the reason that the obvious magnetic anomaly of the earthquake is not detected.