汶川地震区平通镇断层围陷波探测
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摘要
平通镇位于汶川8.0级地震断层带上,地表破坏十分严重。该断层围陷波测线横跨断层,以地震探槽为大致中点,沿NW-SE方向两端延伸,测线长约400m。观测结果表明,在汶川8.0级地震的新破裂带中可以观测到断层围陷波,反映了断层带内外的介质在物理性质上有较大的差异。该测线记录的断层围陷波优势频率大约为3～4Hz。探槽附近的台站断层围陷波较强,初步推测,该地段地壳内断层的宽度有200多米。另外,从一些地震记录上可以看出,以探槽为界,两侧波形差异十分明显,S波到时错位也很明显。地壳内波形明显差异的部位与考察看到的地表隆起边界位置一致。
Pingtong Town locates just over the fractured zone of the Wenchuan Ms8.0 earthquake and the damage at the surface is very serious.The observational line with its middle point at an earthquake exploration trough crosses the fractured zone,and stretches in NW-SE direction,whose total length is about 400 m.The observational results show that the fault zone trapped waves from the fractured zone of Wenchuan Ms 8.0 earthquake were observed.That indicates that there is a great difference in physical property between the media inside and outside the fault zone.The predominant frequency of the fault zone trapped waves is about 3-4 Hz.It is stronger near the exploration trough.The width of the fault zone in the crust in this region is estimated to be 200 m.Furthermore,from some records it can be seen that the waveforms between the two sides of the trough are quite different and the arrival times of the S waves are also different.The sudden variation point of the waveforms is consistent with the boundary of the uplift at the surface.
Pingtong Town locates just over the fractured zone of the Wenchuan Ms8.0 earthquake and the damage at the surface is very serious.The observational line with its middle point at an earthquake exploration trough crosses the fractured zone,and stretches in NW-SE direction,whose total length is about 400 m.The observational results show that the fault zone trapped waves from the fractured zone of Wenchuan Ms 8.0 earthquake were observed.That indicates that there is a great difference in physical property between the media inside and outside the fault zone.The predominant frequency of the fault zone trapped waves is about 3-4 Hz.It is stronger near the exploration trough.The width of the fault zone in the crust in this region is estimated to be 200 m.Furthermore,from some records it can be seen that the waveforms between the two sides of the trough are quite different and the arrival times of the S waves are also different.The sudden variation point of the waveforms is consistent with the boundary of the uplift at the surface.
引文
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14徐锡伟,等.川西及其邻近地区活动构造基本特征与强震复发模型[J].地震地质,2005,27(3):446-461.14Xu Xiwei,et al.Features of active tectonics and recurrence behaviors of strong earthquakes in the western sichuan prov-ince and its adjacent regions[J].Seismology and Geology,2005,27(3):446-461.(in Chinese)
2Li Y G,et al.Fine structure of the Landers fault zone:seg-mentation and the rupture process[J].Science,1994b,256:367-370.
3Li Y G,et al.A delineation of the Nojima fault ruptured in theM7.2Kobe,Japan,earthquake of1995using fault zone trapped waves[J].J Geophys Res,1998,103:7247-7263.
4Li Y G,et al.Shallow structure of the Landers fault zone u-sing explosion-excited trapped waves[J].J Geophys Res,1999,104:20257-20275.
5Li Y G,Vidale J E and Aki K.Depth-dependent structure of the Landers fault zone using fault zone trapped waves gen-erated by aftershocks[J].J Geophys Res,2000,105:6237-6254.
6Li Y G and Vidale J E.Healing of the shallow fault zone from1994-1998after the1992M7.5Landers,California earthquake[J].Geophys Res Lett,2001,28:2999-3002.
7Li Y G,et al.Study of the1999M7.1Hector Mine,Califor-nia earthquake fault plane by trapped waves[J].Bull Seis-mol Soc Am,2002,92:1318-1332.
8Li Y G,et al.Mulyiple-fault rupture of theM7.1Hector Mine,California earthquake from fault-zone trapped waves[J].J Geophys Res,2003,108:2165-2190.
9李松林,张先康,樊计昌.利用断层围陷波研究昆仑山口西8.1级地震破裂面[J].地震学报,2005,27(1):42-50.9Li Songlin,Zhang Xiankang and Fan Jichang.Study on rup-ture zone of theM8.1west Kunlun mountains earthquake u-sing fault zone trapped waves[J].Acta Seismologica Sinica,2005,27(1):42-50.(in Chinese)
10楼海,等.昆仑山断层围陷波的分析和研究[J].地球物理学报,2006,49(3):788-796.10Lou Hai,et a1.Analysis of the trapped wave recorded in Kunlun fault zone[J].Chinese J Geophys,2006,49(3):788-796.(in Chinese)
11王椿镛,等.2001年11月14日昆仑山西口Ms8.1地震产生的断层带细结构研究[A].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[C].北京:地震出版社,2004,38-58.11Wang Chunyong,et a1.A study on the detailed shallow structure of seismic fault zone generated by the KunlunMs8.1earthquake on Nov.14,2001[A].Advances in Seis-mology and Physics of the Earth’s Interior in China:in Honor of academician Zeng Rongsheng’s80birthday[C].Beijing:Seismological Press,2004,38-58.(in Chinese)
12李松林,等.汤西断裂的断层围陷波初步研究[J].地震地质,2007,29(2):354-361.12Li Songlin,et al.A preliminary study on tangxi fault using fault zone trapped waves[J].Seismology and Geology,2007,29(2):354-361.(in Chinese)
13张培震,等.2008年汶川8.0级地震发震断裂的滑动速率、复发周期和构造成因[J].地球物理学报,2008,51(4):1066-1073.13Zhang Peizhen,et al.Slip rates and recurrence intervals of the Longmenshan active fault zone,andtectonic imlications for the mechanism of the May12Wenchuan earthquake,2008,Sichuan,China[J].Chinese J Geophys,2008,51(4):1066-1073.(in Chinese)
14徐锡伟,等.川西及其邻近地区活动构造基本特征与强震复发模型[J].地震地质,2005,27(3):446-461.14Xu Xiwei,et al.Features of active tectonics and recurrence behaviors of strong earthquakes in the western sichuan prov-ince and its adjacent regions[J].Seismology and Geology,2005,27(3):446-461.(in Chinese)
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