海陆地震联测流动台站布设及信号分析
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摘要
利用海上大容量气枪作为震源,陆上固定台网和流动台站作为接收台阵的海陆地震联测试验在南海北部已开展多次,其中流动台站的布设一直是野外试验中至关重要的工作之一。作者以2011年海南岛海陆地震联测试验为基础,对野外流动台站的布设过程及注意事项进行了分析总结;从同一震源不同台基记录信号的差异性、不同震源同一台基记录信号的变化特征以及相近接收距离不同台基记录的信号特征等方面对以下3个不同类型台基上流动台站接收到的气枪信号进行了对比分析,发现接收到的气枪信号与台基的稳定性、环境噪音的大小存在紧密关系。在相近接收距离下,当布设台基为山脚成片的基性岩石时,流动台站接收到的信号信噪比很高,且波形持续时间较短,能量较为集中;当布设台基为河边冲积的岩石时,流动台站接收到的信号信噪比较差,且波形持续时间较长,能量较为分散,导致信号的到时难以分辨;而当布设台基为山顶半悬浮大块岩石时,流动台接收到的信号的信噪比最差。从处理的地震剖面可知,台基为成片出露的基性岩石时,震相数据最为清晰,拾取也更准确。
Onshore-offshore seismic experiment uses air-gun arrays as seismic sources,permanent and portable land stations and ocean bottom seismometers to form a signal record array.Such experiment has been carried out many times in the northern South China Sea,and layout of portable stations was always a key for the success in such a field experiment.This paper is based on the onshore-offshore seismic experiment in Hainan island during 2011.It summarizes the processes and matters that need attention during deploying portable stations,and analyzes air-gun signals received by portable stations on three different types of basements.We find that the received air-gun signals were closely related to the stability of the basement and the ambient noise.When using exposed abundant basic rock as the basement,portable stations acquired high signal-to-noise ratio(SNR),and long duration of the waveform and more concentrated energy.When the basement was large semi-floating rockmass on a mountaintop,the portable stations received general SNR,and long duration of waveform.When the basement was rocks exposed in the sedimentary layer,the signal received by portable station performed lower SNR,longer duration of waveform,and decentralized energy;even the arrival time was hard to identify.From the processed profiles,we conclude thatclearly seismic phase and more accurate arrival time were easily acquired when exposed abundant basic rock was used as the basement.
Onshore-offshore seismic experiment uses air-gun arrays as seismic sources,permanent and portable land stations and ocean bottom seismometers to form a signal record array.Such experiment has been carried out many times in the northern South China Sea,and layout of portable stations was always a key for the success in such a field experiment.This paper is based on the onshore-offshore seismic experiment in Hainan island during 2011.It summarizes the processes and matters that need attention during deploying portable stations,and analyzes air-gun signals received by portable stations on three different types of basements.We find that the received air-gun signals were closely related to the stability of the basement and the ambient noise.When using exposed abundant basic rock as the basement,portable stations acquired high signal-to-noise ratio(SNR),and long duration of the waveform and more concentrated energy.When the basement was large semi-floating rockmass on a mountaintop,the portable stations received general SNR,and long duration of waveform.When the basement was rocks exposed in the sedimentary layer,the signal received by portable station performed lower SNR,longer duration of waveform,and decentralized energy;even the arrival time was hard to identify.From the processed profiles,we conclude thatclearly seismic phase and more accurate arrival time were easily acquired when exposed abundant basic rock was used as the basement.
引文
[1]赵明辉,丘学林,叶春明等.南海东北部海陆联测与滨海断裂带两侧地壳结构分析[J].地球物理学报,2004,47(5):845–852.
[2]徐杰,张进,周本刚,等.关于南海北部滨海断裂带的研究[J].华南地震,2006,26(4):8–13.
[3]刘以宣,钟建强,詹文欢.南海北部陆缘地震带基本特征及区域稳定性初步分析[J].华南地震,1994,14(4):41–46.
[4]徐辉龙,丘学林,赵明辉,等.南海东北部南澳大地震(M=7.5)震中区的地壳结构特征与震源构造[J].科学通报,2006,51(SⅡ):83–91.
[5]刘以宣.华南沿海区域断裂构造分析[M].北京:地震出版社,1981:1-10.
[6]詹文欢,孙宗勋,唐诚,等.华南滨海断裂带及其对台湾海峡地震活动的控制作用[J].热带海洋学报,2004,23(4):19–24.
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[11]丘学林,陈颙,朱日祥,等.大容量气枪震源在海陆联测中的应用:南海北部试验结果分析[J].科学通报,2007,52(1):1–7.
[12]赵明辉,丘学林,夏少红,等.大容量气枪震源及其波形特征[J].地球物理学报,2008,51(2):558–565.
[13]陈颙,张先康,丘学林,等.陆地人工激发地震波的一种新方法[J].科学通报,2007,52(11):1317–1321.
[14]OKAYA D,HENRYS S,STEM T.Double-sided onshore-offshore seismic imaging of a plate boundary:“super-gathers”across South Island,New Zealand[J].Tectonophysics,2002,255:247–263.
[15]NAZARETH J J,CLAYTON R W.Crustal structure of theBorderland-Continent Transition Zone of southern Californiaadjacent to Los Angeles[J].J Geophys Res,108(B8):2404.doi:10.1029/2001JB000223.
[16]VAN AVENDONK H J A,HOLBROOK W S,OKAYA D,etal.Continental crust under compression:A seismic refractionstudy of South Island Geophysical Transect I,South Island,New Zealand[J].J Geophys Res,2004,109(B06302).doi:10.1029/2003JB002790.
[17]MELHUISH A,HOLBROOK W S,DAVEY F,et al.Crustaland upper mantle seismic structure of the Australian Plate,South Island,New Zealand[J].Tectonophysics,2005,395:113–135.
[18]MCINTOSH K,NAKAMURA Y,WANG T-K,et al.Crustal-scale seismic profiles across Taiwan and the westernPhilippine Sea[J].Tectonophysics,2005,401:23–54.
[19]赵明辉,丘学林,夏戡原,等.南海东北部海陆联测地震数据处理及初步结果[J].热带海洋学报,2004,23(1):58–63.
[20]夏少红,丘学林,赵明辉,等.香港与珠三角地区海陆联合地震探测的数据处理[J].热带海洋学报,2007,26(1):35–38.
[2]徐杰,张进,周本刚,等.关于南海北部滨海断裂带的研究[J].华南地震,2006,26(4):8–13.
[3]刘以宣,钟建强,詹文欢.南海北部陆缘地震带基本特征及区域稳定性初步分析[J].华南地震,1994,14(4):41–46.
[4]徐辉龙,丘学林,赵明辉,等.南海东北部南澳大地震(M=7.5)震中区的地壳结构特征与震源构造[J].科学通报,2006,51(SⅡ):83–91.
[5]刘以宣.华南沿海区域断裂构造分析[M].北京:地震出版社,1981:1-10.
[6]詹文欢,孙宗勋,唐诚,等.华南滨海断裂带及其对台湾海峡地震活动的控制作用[J].热带海洋学报,2004,23(4):19–24.
[7]陈恩民,黄泳茵.华南十九次强震既南海北部陆缘地震带概述[J].华南地震,1984,4(1):11–32.
[8]邹和平.南海北部陆缘地震带的深部结构和孕震机制[J].华南地震,1998,18(3):16–20.
[9]丘学林、施小斌、阎贫,等.南海北部地壳结构的深地震探测和研究新进展[J].自然科学进展,2003,13(3):231–236.
[10]丘学林,赵明辉,叶春明,等.南海东北部海陆联测与海底地震仪探测[J].大地构造与成矿学,2003,27(4):295–281.
[11]丘学林,陈颙,朱日祥,等.大容量气枪震源在海陆联测中的应用:南海北部试验结果分析[J].科学通报,2007,52(1):1–7.
[12]赵明辉,丘学林,夏少红,等.大容量气枪震源及其波形特征[J].地球物理学报,2008,51(2):558–565.
[13]陈颙,张先康,丘学林,等.陆地人工激发地震波的一种新方法[J].科学通报,2007,52(11):1317–1321.
[14]OKAYA D,HENRYS S,STEM T.Double-sided onshore-offshore seismic imaging of a plate boundary:“super-gathers”across South Island,New Zealand[J].Tectonophysics,2002,255:247–263.
[15]NAZARETH J J,CLAYTON R W.Crustal structure of theBorderland-Continent Transition Zone of southern Californiaadjacent to Los Angeles[J].J Geophys Res,108(B8):2404.doi:10.1029/2001JB000223.
[16]VAN AVENDONK H J A,HOLBROOK W S,OKAYA D,etal.Continental crust under compression:A seismic refractionstudy of South Island Geophysical Transect I,South Island,New Zealand[J].J Geophys Res,2004,109(B06302).doi:10.1029/2003JB002790.
[17]MELHUISH A,HOLBROOK W S,DAVEY F,et al.Crustaland upper mantle seismic structure of the Australian Plate,South Island,New Zealand[J].Tectonophysics,2005,395:113–135.
[18]MCINTOSH K,NAKAMURA Y,WANG T-K,et al.Crustal-scale seismic profiles across Taiwan and the westernPhilippine Sea[J].Tectonophysics,2005,401:23–54.
[19]赵明辉,丘学林,夏戡原,等.南海东北部海陆联测地震数据处理及初步结果[J].热带海洋学报,2004,23(1):58–63.
[20]夏少红,丘学林,赵明辉,等.香港与珠三角地区海陆联合地震探测的数据处理[J].热带海洋学报,2007,26(1):35–38.
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