汤西断裂的断层围陷波初步研究
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摘要
作为断层围陷波方法在城市活断层探测中的首次尝试,我们针对太行山山前断裂带南段的汤西断裂开展了爆炸震源的观测试验。运用数字滤波和频谱分析等技术,由地震记录图分离出了断层围陷波。根据2横测线的观测结果,可确定断层的位置,并可推测断层在该处宽度为200～300m。破裂面较宽,可能与其张性特征有关。分频道地震图显示,断层围陷波具有正频散现象,其低频分量传播较快。这表明断层围陷波是一种面波,可利用其频散规律研究断裂带内介质的物理性质。这次的观测结果也表明,断层围陷波并不局限于新破裂带,在老断层中也能形成和传播。事实上,只要断层带内外的介质在物理性质上有较大的差异,均能产生沿断层传播的围陷波。在城市活断层探测中,断层围陷波的方法具有非常独特的优越性。
As the first application of fault zone trapped waves to the active fault exploration in urban areas,an experiment aimed at Tangxi Fault of Taihang Mtns.Fault Belt was performed with explosion sources.By using digital filtering,spectral analysis and other techniques,the fault zone trapped waves were separated from seismograms.Based on the observational data of two transverse profiles,the position of the fault was detected,and its width was assumed to be 200～300m.The great width of the fractured zone may be due to the tensional action.The normal dispersion nature of the fault zone trapped waves was revealed from multiple band-pass filtered seismograms.The waves with lower frequencies travel faster than those with higher frequencies.This indicates that the fault zone trapped waves are surface waves and their dispersions can be used to study physical properties of the medium in the fault zone.The results also show that the fault zone trapped waves can be formed and propagate not only in new fractured zones,but also in old faults.Indeed,they can be generated if the physical properties of the mediums inside and outside the fault zone are quite different.The method using fault zone trapped waves is of great advantage for active fault exploration,especially in urban areas.
As the first application of fault zone trapped waves to the active fault exploration in urban areas,an experiment aimed at Tangxi Fault of Taihang Mtns.Fault Belt was performed with explosion sources.By using digital filtering,spectral analysis and other techniques,the fault zone trapped waves were separated from seismograms.Based on the observational data of two transverse profiles,the position of the fault was detected,and its width was assumed to be 200～300m.The great width of the fractured zone may be due to the tensional action.The normal dispersion nature of the fault zone trapped waves was revealed from multiple band-pass filtered seismograms.The waves with lower frequencies travel faster than those with higher frequencies.This indicates that the fault zone trapped waves are surface waves and their dispersions can be used to study physical properties of the medium in the fault zone.The results also show that the fault zone trapped waves can be formed and propagate not only in new fractured zones,but also in old faults.Indeed,they can be generated if the physical properties of the mediums inside and outside the fault zone are quite different.The method using fault zone trapped waves is of great advantage for active fault exploration,especially in urban areas.
引文
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Li Y G,Aki K,Adams D,et al.1994a.Seismic guided waves trapped in the fault zone of the Landers,California,earthquake of1992[J].J Geophys Res,99(B6):11705—11722.
Li Y G,Vidale J E,Aki K,et al.1994b.Fine structure of the Landers fault zone,segmentation and the ruptureprocess[J].Science,256:367—370.
Li Y G,Aki K,Vidale J E,et al.1998.Adelineation of the Nojima fault ruptured in theM7.2Kobe,Japan,earth-quake of1995using fault zone trapped waves[J].J Geophys Res,103(B4):7247—7263.
Li Y G,Aki K,Vidale J E,et al.1999.Shallow structure of the Landers fault zone using explosion-excited trappedwaves[J].J Geophys Res,104(B9):20257—20275.
Li Y G,Vidale J E,Aki K.2000.Depth-dependent structure of the Landers fault zone using fault zone trapped wavesgenerated by aftershocks[J].J Geophys Res,105(B3):6237—6254.
Li Y G,Vidale J E.2001.Healing of the shallowfault zone from1994—1998after the1992M7.5Landers,Califor-nia earthquake[J].Geophys Res Lett,28(15):2999—3002.
Li Y G,Vidale J E,Day S M,et al.2002.Study of the1999M7.1Hector Mine,California earthquake fault planeby trapped waves[J].Bull Seismol Soc Am,92(4):1318—1332.
Li Y G,Vidale J E,Oglesby D D,et al.2003.Multiple-fault rupture of theM7.1Hector Mine,California earth-quake from fault-zone trapped waves[J].J Geophys Res,108(B3):2165—2190.
Rovelli A,Caserta A,Marra F,et al.2002.Can seismic waves be trapped inside an inactive fault zone?The case studyof Nocera Umbra,Central Italy[J].Bull Seism Soc Am,92(6):2217—2232.
刘尧兴,周庆,荆智国.2001.豫北地区新构造活动特征及中长期地震预测研究[M].西安:西安地图出版社.LIUYao-xing,ZHOU Qing,Jing Zhi-guo.2001.Study on the Characteristics of the Recent Tectonic Movement andMiddle-long Term Earthquake Prediction in North Henan[M].Map Press of Xi an,Xi an(in Chinese).
楼海,王椿镛,丁志峰,等.2006.昆仑山断层围陷波的分析和研究[J].地球物理学报,49(3):788—796.LOUHai,WANG Chun-yong,DING Zhi-feng,et al.2006.Analysis of the trapped wave recorded in Kunlun Faultzone[J].Chinese J Geophys,49(3):788—796(in Chinese).
王椿镛,丁志峰,杨建思,等.2004.2001年11月14日昆仑山口西MS8.1地震产生的断层带细结构研究[A].见:中国大陆地震学与地球内部物理学进展:庆贺曾融生院士八十寿辰.北京:地震出版社.38—58.WANG Chun-yong,DING Zhi-feng,YANG Jian-si,et al.2004.A study on the detailed shallow structure of seismicfault zone generated by the KunlunMS8.1earthquake on Nov.14,2001[A].In:Advances in Seismology andPhysics of the Earth s Interior in China:in Honor of Academician Zeng Rongsheng s80thBirthday.SeismologicalPress,Beijing.38—58(in Chinese).
Li Y G,Aki K,Adams D,et al.1994a.Seismic guided waves trapped in the fault zone of the Landers,California,earthquake of1992[J].J Geophys Res,99(B6):11705—11722.
Li Y G,Vidale J E,Aki K,et al.1994b.Fine structure of the Landers fault zone,segmentation and the ruptureprocess[J].Science,256:367—370.
Li Y G,Aki K,Vidale J E,et al.1998.Adelineation of the Nojima fault ruptured in theM7.2Kobe,Japan,earth-quake of1995using fault zone trapped waves[J].J Geophys Res,103(B4):7247—7263.
Li Y G,Aki K,Vidale J E,et al.1999.Shallow structure of the Landers fault zone using explosion-excited trappedwaves[J].J Geophys Res,104(B9):20257—20275.
Li Y G,Vidale J E,Aki K.2000.Depth-dependent structure of the Landers fault zone using fault zone trapped wavesgenerated by aftershocks[J].J Geophys Res,105(B3):6237—6254.
Li Y G,Vidale J E.2001.Healing of the shallowfault zone from1994—1998after the1992M7.5Landers,Califor-nia earthquake[J].Geophys Res Lett,28(15):2999—3002.
Li Y G,Vidale J E,Day S M,et al.2002.Study of the1999M7.1Hector Mine,California earthquake fault planeby trapped waves[J].Bull Seismol Soc Am,92(4):1318—1332.
Li Y G,Vidale J E,Oglesby D D,et al.2003.Multiple-fault rupture of theM7.1Hector Mine,California earth-quake from fault-zone trapped waves[J].J Geophys Res,108(B3):2165—2190.
Rovelli A,Caserta A,Marra F,et al.2002.Can seismic waves be trapped inside an inactive fault zone?The case studyof Nocera Umbra,Central Italy[J].Bull Seism Soc Am,92(6):2217—2232.
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