多种方法测定广东阳西3.7级地震震源深度
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摘要
应用CAP和深度震相方法,对2018年3月20日发生在广东阳西的M 3.7级地震震源深度进行了测定。首先通过CAP方法反演获得震源机制解,拟合最佳震源深度为12 km。然后在震中距100 km以内的近台识别出清晰的sPL和PmP、 sPmP震相,利用频率-波数(F-K)方法,计算出深度震相在不同深度下的理论地震图,与实际观测波形对比测定震源深度为12 km。再利用250～400 km震中距范围内台站上识别出的sPn与Pn震相的走时差,测得震源深度12.6 km。多种方法的研究结果一致,表明该地震震源深度为12 km比较可靠。
By using CAP and depth phase method, the focal depth of the M 3.7 earthquake happened on March20~(th), 2018 in Yangxi of Guangdong Province was determined. Firstly, the focal mechanism solution is inverted by CAP, and the optimal focal depth is got as 12 km. Then the sPL, PmP and sPmP phases are identified clearly at near stations of epicenter distance within 100 km. By using frequency-wavenumber(F-K)method,theoretical seismograms of deep phases at different depths are calculated, and the focal depth is determined as12 km after compared with the actual observed waveforms. Meanwhile, according to the travel time difference between sPn and Pn phases identified on the stations within the epicenter distance of 250-400 km, the focal depth is measured as 12.6 km. The consistency of the results obtained from several methods indicates that the focal depth of 12 km for this earthquake is a reliable result.
By using CAP and depth phase method, the focal depth of the M 3.7 earthquake happened on March20~(th), 2018 in Yangxi of Guangdong Province was determined. Firstly, the focal mechanism solution is inverted by CAP, and the optimal focal depth is got as 12 km. Then the sPL, PmP and sPmP phases are identified clearly at near stations of epicenter distance within 100 km. By using frequency-wavenumber(F-K)method,theoretical seismograms of deep phases at different depths are calculated, and the focal depth is determined as12 km after compared with the actual observed waveforms. Meanwhile, according to the travel time difference between sPn and Pn phases identified on the stations within the epicenter distance of 250-400 km, the focal depth is measured as 12.6 km. The consistency of the results obtained from several methods indicates that the focal depth of 12 km for this earthquake is a reliable result.
引文
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[4] Geiger L. Probability method for the determination of earthquake epicenters from arrival time only[J]. Bull. St. Louis.Univ.,1912,8:60-71.
[5]罗艳,曾祥方,倪四道.震源深度测定方法研究进展[J].地球物理学进展,2013,28(5):2309-2321.
[6]郑勇,谢祖军.地震震源深度定位研究的现状与展望[J].地震研究,2017,40(2):167-175+333.
[7] Zhang X, Ye X,Lv J,et al. Crustal structure revealed by a deep seismic sounding profile of Baijing-Gaoming-Jinwan in the Pearl River Delta[J]. J. Ocean Univ. China,2018,17(1):186-194.
[8]王力伟,王小娜,吴国瑞等. 2018年3月20日阳江新湖水库ML4.2级震群发震机理分析[J].华南地震, 2018,38(S1):1-8.
[9]魏柏林,薛佳谋,秦乃岗等.阳江地区的震源机制解、发震构造与应力场[J].华南地震,1988,8(1):1-11.
[10] Zhao L S,Helmberger D V. Source estimation from broadband regional seismograms[J]. Bull. Seism. Soc.Am.,1994,84:91-104.
[11] Zhu L P,Helmberger D V. Advancement in source estimation techniques using broadband regional seismograms[J]. Bull. Seism. Soc. Am.,1996,86(5):1634-1641.
[12]郑勇,马宏生,吕坚等.汶川地震强余震(Ms≥5.6)的震源机制解及其与发震构造的关系[J].中国科学D辑:地球科学,2009,39(4):413-426.
[13] Aki K,Richards P G. Quantitative seismology(second edition)[M]. Sausalito,CA:University Science Books,2002.
[14]崇加军,倪四道,曾祥方. sPL,一个近距离确定震源深度的震相[J].地球物理学报,2010,53(11):2620-2630.
[15] Zhu L,Rivera L A. A note on the dynamic and static displacements from a point source in multilayered media[J]. Geophys. J. Int.,2002,148(3):619-627.
[16] Waldhauser F,Ellsworth W L. A double-difference earthquake location algorithm:Method and application to the northern Hayward fault,California[J]. Bull. Seism. Soc. Am.,2000,90(6):1353-1368.
[17]孙茁,吴建平,房立华等.利用sPn震相测定芦山Ms7.0级地震余震的震源深度[J].地球物理学报,2014,57(2):430-440.
[18]杨凯,倪四道,何骁慧,等.中强地震震源机制解目录发展综述[J].地球物理学进展,2018. http://kns.cnki.net/kcms/detail/11.2982.P.20180122.1443.158.html.