多种方法研究2012年7月20日江苏高邮M_S4.9级地震震源机制解和震源深度

Focal mechanism and focal depth of July 20 , 2012 JiangSu Gaoyou M_S4.9 earthquake

本文用多种数字地震学方法研究了2012年7月20日江苏高邮MS4.9级地震的震源机制解和震源深度.首先用CAP方法反演了江苏高邮MS4.9级地震的震源机制解和震源深度,最佳解节面I走向角为109°,倾角85°,滑动角18°;节面II走向角17°,倾角72°,滑动角175°;矩震级MW为4.82;优势震源深度为10km.为验证研究结果的可靠性,我们一方面用Snoke方法反演了高邮地震的震源机制解,反演结果与CAP方法反演的结果相差不大;另一方面,使用近震深度震相到时差的测量和对远震波形拟合的方法进一步研究震源深度,结果均表明江苏高邮MS4.9级地震的震源深度在9～10km左右,与CAP方法的结果一致.多种方法研究结果的一致性可以充分说明本文研究结果比较可靠.结合前人地质资料的研究成果和本文对高邮地震震源机制解的研究,我们认为滁河断裂很可能是江苏高邮MS4.9级地震的发震构造.

In this paper, several digital seismological methods ware used to study the source mechanism and focal depth of July 20, 2012 JiangSu Gaoyou Ms 4. 9 earthquake. At first, we inverted the focal mechanism by CAP method with Crustal 2. 0 velocity model, the epicentral distance of stations involved in are within 250 kilometers. The result showed that the best double couple solution of the Ms 4. 9 event is 109°, 85°and 18°, for strike, dip and rake angles respectively, and the other nodal plane is 17°, 72°, 175°.The estimated focal depth is about 10km To verify the reliability of the results, we used the Snoke method to invert Gaoyou earthquake focal mechanism again, using the same velocity model with that of CAP metode and depth input parameter of 10 kin, and the results ware basically consistent with that of CAP method. To further confirm the earthquake focal depth, we selected 8 station records with high signal to noise ratio. All of those traces can clearly distinguish the sPn phase. Through measuringthe arrival time difference between sPn and Pn phase of local earthquake, we found the differential arrival time is obout 3. 82 s on the average, which is significantly agreed with the theoretical result by calculating differential arrival time with Crustal 2. 0 velocity model and depth input parameter of 10 km. At last, by fitting the tele- seismogram with synthetic seismograms, we could basically confirm the focal depth of the Gaoyou Ms 4. 9 earthquake about 9 to 10 km. The consistency of the results of several method fully indicated the reliability of the results of this study. Combined with the previous researth on geological data and the focal mechanism solution of the Gaoyou earthquake, we refer that the the Chu-he fault is likely to be seismogenic structure of the Gaoyou Ms 4. 9 earthquake.