论文部分内容阅读
应用1990年至1995年CDSN台网兰州数字台的记录和中法合作建立的朗索数字台的记录,研究了1995年7月22日甘肃永登5.8级地震前后剪切波分裂的特征.利用最大特征值法、波形识别算子法和最大似然法定量确定了剪切波分裂的快慢波时间延迟及快波偏振方向.结果表明,在永登地震前大约1年的时间内剪切波分裂延迟增大,快剪切波偏振方向也从NE向转为NW向,地震后剪切波分裂时间延迟和偏振方向很快恢复.其时间延迟变化与Peacock(1988)的结果很相似,而快波偏振方向的变化类似于1990年肃南地震过程.因此,可以认为,此次地震前S波分裂方面的前兆特征是明显的.
Based on the record of Lanzhou digital station of CDSN network from 1990 to 1995 and the record of Lanxess digital station established by China-France cooperation, the characteristics of shear-wave splitting before and after the May 1998 Gengsu Yongdeng earthquake . The maximum eigenvalue method, the waveform recognition operator method and the maximum likelihood method are used to quantitatively determine the time delay of fast and slow wave splitting and the polarization direction of fast wave. The results show that the splitting delay of shear wave increases within about one year before the Yongdeng earthquake, and the polarization direction of fast shear wave also changes from NE to NW. The time delay and polarization direction of shear wave splitting after the earthquake are very fast restore. The time delay variation is similar to that of Peacock (1988), while the change of polarization in fast wave is similar to that of the 1990 Sunan earthquake. Therefore, it can be considered that the precursory features of S-wave splitting before the earthquake are obvious.