2011年安庆4.8级地震序列S波分裂研究
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摘要
采用互相关系数法,计算了2011年安庆MS4.8地震的余震S波分裂参数。结果表明,余震序列的S波分裂现象明显,快S波平均偏振方向在近NNW向,与区域最大水平主压应力方向基本一致。通过分析延迟时间随时间的变化趋势,可以看出MS4.8地震后有明显的应力释放现象。在几次较大余震前,观测到延迟时间呈现增加的特征,并且其中一次余震在发生之前的短时间内还出现延迟时间减小的现象,这一现象符合震前应力长时间积累和短时间应力释放的结论,时间延迟在强震前会出现下降具有重要的地震短临预测意义。研究认为S波分裂参数可以反映区域应力场的动态变化信息,可以为安徽南部地区应力场研究与地震预测提供有用的信息。
Using correlation coefficient method,a study of shear wave splitting is made through the recording of aftershocks of the Anqing MS4.8 earthquake,Anhui province in 2011.The results show that the preponderant polarization of the fast shear wave is NNW.It accords with the regional predominant direction of principal compressional stress.By analyzing the change of S wave time delay,obvious stress relaxation could be seen after the MS4.8 earthquake.The time delay basically increases before strong aftershocks.However,it was observed that the time delay decreased abruptly immediately before one strong aftershock.It is coincident with the conclusion that long-term stress accumulation and short-term stress relaxation existed before earthquakes.It is significant for the short-term earthquake prediction that the time delay decreases before strong earthquakes.The result suggests that parameters of shear wave splitting may reflect the dynamic change of regional stress field and provide useful information for the study of stress field and earthquake prediction.
Using correlation coefficient method,a study of shear wave splitting is made through the recording of aftershocks of the Anqing MS4.8 earthquake,Anhui province in 2011.The results show that the preponderant polarization of the fast shear wave is NNW.It accords with the regional predominant direction of principal compressional stress.By analyzing the change of S wave time delay,obvious stress relaxation could be seen after the MS4.8 earthquake.The time delay basically increases before strong aftershocks.However,it was observed that the time delay decreased abruptly immediately before one strong aftershock.It is coincident with the conclusion that long-term stress accumulation and short-term stress relaxation existed before earthquakes.It is significant for the short-term earthquake prediction that the time delay decreases before strong earthquakes.The result suggests that parameters of shear wave splitting may reflect the dynamic change of regional stress field and provide useful information for the study of stress field and earthquake prediction.
引文
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[8]邬成栋,秦嘉政,皇甫岗.2001年永胜6.0级地震的余震S波分裂研究[J].地震研究,2004,27(2):140-145.
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[2]Crampin S,Volti T,Stefansson R.A successfully stress-forecast earthquake[J].Geopys J lnt,1999,138,Fl-FS.
[3]刘堑,张中杰,胡家富,等.中国陆区S波分裂的频带相关性及其意义[J].中国科学D辑:地球科学,2001,31(2):155-161.
[4]Zhang Z J,Teng J W,Badal J,et al.Construction of regional and local seismic anisotropic struc-tures from wide-angle seismic data:crustal deformation in the southeast of China[J].J Seismol,2008,doi:10.1007/s10950-008-9124-0.
[5]高原,郑斯华,孙勇.唐山地区地壳裂隙各向异性[J].地震学报,1995,17(3):283-293.
[6]华卫,刘杰,陈章立,等.2003年云南大姚6.2级、6.1级地震序列S波分裂研究[J].地震学报,2006,28(4):357-371.
[7]Crampin S,Gao Y.A review of techniques for measuring seismic shear-wave splitting above smallearthquakes[J].Phys Earth Planet Interi,2006,159(1/2):114.
[8]邬成栋,秦嘉政,皇甫岗.2001年永胜6.0级地震的余震S波分裂研究[J].地震研究,2004,27(2):140-145.
[9]王椿镛,丁志峰,陈学波,等.大别造山带地壳S波分裂和介质各项异性[J].科学通报,1997,42(23):101-109.
[10]高原,郑斯华.唐山地区剪切波分裂研究(Ⅱ)相关函数分析法[J].中国地震,1994,10(9):22-32.
[11]太龄雪,高原,曹风娟,等.辽宁1999年MS5.9岫岩地震的剪切波分裂特征[J].地震学报,2008,30(4):340-354.
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