气枪震源激发条件对走时变化观测结果的影响
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摘要
基于4支单枪容量2 000 in3的气枪组成的阵列,2017年2月在宾川地震信号发射台大银甸水库内开展了不同激发气枪压力、沉放深度和水平位移情况下的对比试验。利用发射台周边9个流动宽频带数字地震仪与震源附近3个参考台的数据,使用互相关时延检测的方法计算了不同激发条件下的气枪信号的走时变化,并结合激发条件进行了分析。研究表明:(1)不同气枪压力或沉放深度下,激发的气枪信号的波形和互相关系数存在明显差异;(2)气枪压力从9 MPa升为15 MPa,走时变化可达0.06 s;(3)走时变化的可能原因是主频段(3~5Hz)中的相对高频成分发生变化,相对低频成分未变化,二者耦合在一起形成了伪走时变化;(4)由于气枪信号不同时窗走时变化不尽相同,技术手段难以消除压力的影响,所以建议未来气枪激发时固定激发条件;利用已有资料做走时变化相关研究时选用震幅相近的数据。
Airgun source is a newtype of artificial source,and it performs very well in travel-time changes research because of its high repeatability. To get the effect of exciting condition,we carried out the time changes analysis with excitement in different pressure,depth and location. The results showed that:(1) Shapes and cross correlation coefficients between waveforms in different exciting conditions showclear diversities.(2) Travel time changes reach 0. 06 s if air-gun's pressure increased from 9 MPa to 15 MPa.(3) High-frequency component of the received data has changed and low-frequency component has not,so the reason of the time changes which associated with triggering condition change is the coupling of the two components. These changes do not real travel-time-changes.(4) Because the tendency of different time windowof received data is not similar,it is difficult to remove influence of triggering condition. We suggest keeping triggering condition unchanged in later experiment if possible. If the already produced data are used,it's better to select data which have the same amplitude.
Airgun source is a newtype of artificial source,and it performs very well in travel-time changes research because of its high repeatability. To get the effect of exciting condition,we carried out the time changes analysis with excitement in different pressure,depth and location. The results showed that:(1) Shapes and cross correlation coefficients between waveforms in different exciting conditions showclear diversities.(2) Travel time changes reach 0. 06 s if air-gun's pressure increased from 9 MPa to 15 MPa.(3) High-frequency component of the received data has changed and low-frequency component has not,so the reason of the time changes which associated with triggering condition change is the coupling of the two components. These changes do not real travel-time-changes.(4) Because the tendency of different time windowof received data is not similar,it is difficult to remove influence of triggering condition. We suggest keeping triggering condition unchanged in later experiment if possible. If the already produced data are used,it's better to select data which have the same amplitude.
引文
陈惠芳,林彬华,金星,等.2016.水库大容量气枪震源激发条件优化实验研究[J].中国地震,32(2):241-248.
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夏季,金星,蔡辉腾,等.2016.大容量气枪震源子波时频特性及其影响因素[J].中国地震,32(2):249-260.
杨微,葛洪魁,王宝善,等.2010.由精密控制人工震源观测到的绵竹5.6级地震前后波速变化[J].地球物理学报,53(5):1149-1157.
郑定昌,王俊.2017.基于背景噪声的川滇地区勒夫波层析成像[J].地震学报,39(5):633-647.
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Nadeau R M,Foxall W,Mc Evilly T V.1995.clustering and periodic recurrence of microearthquakes on the San Andreas faults at Parkfield,California[J].Science,267(5179):503-507.
Niu F,Silver P G,Daley T M,et al.2008.Preseismic velocity changes observed from active source monitoring at the Parkfield SAFOD drill site[J].Nature,454:204-208,doi:10.1038/nature07111.
Schaff D P,Beroza G C.2004.Coseismic and postseismic velocity changes measured by repeating earthquakes[J].Journal of Geophysical Research,109,B10302,doi:10.1029/2004JB003011.
Wang B S,Ge H K,Yang W,et al.2012.Transmitting seismic station monitors fault zone at depth[J].Eos Transactions American Geophysical Union,93(5):49-50.
Wang B S,Zhu P,Chen Y,et al.2008.Continuous subsurface velocity measurement with coda wave interferometry[J].J Geophys Res,113,B12313,doi:10.1029/2007JB005023.
Yao H,Vander Hilst R D,De Hoop M V.2006.Surface-wave array tomography in SE Tibet from ambient seismic noise and two-station analysis-Ⅰ,Phase velocity maps[J].Geophysical Journal International,166(2):732-744.
Zheng D C,Saygin E,Cummins P,et al.2017.Transdimensional Bayesian seismic ambient noise tomography across SE Tibet[J].Journal of A-sian Earth Sciences,134:86-93.
陈佳,李孝宾,杨军,等.2016.云南宾川大容量气枪震源波形频谱特征分析[J].中国地震,32(2):216-221.
陈佳,叶泵,高琼,等.2017.利用气枪震源信号研究2016年云龙MS5.0地震前后波速变化特征[J].地震研究,40(4):550-556.
陈蒙.2014.利用水库大容量非调制气枪阵列进行区域尺度地下结构探测和监测[D].北京:中国地震局地球物理研究所.
陈颙,朱日祥.2005.设立“地下明灯研究计划”的建议[J].地球科学进展,20(5):485-489.
何汉漪.2001.海上高分辨率地震技术及其应用[M].北京:地质出版社,52-77.
刘自凤,苏有锦,王宝善,等.2015.宾川主动源地震波走时变化分析方法研究[J].地震研究,38(4):591-597
栾奕,杨宏峰,王宝善,等.2016.大容量气枪主动源波形资料处理(一):云南宾川[J].中国地震,32(2):305-318.
王宝善,葛洪魁,王彬,等.2016.利用人工重复震源进行地下介质结构及其变化研究的探索和进展[J].中国地震,32(2):168-179.
王彬,李孝宾,刘自凤,等.2016.宾川地震信号发射台的震源系统、观测系统和观测结果[J].中国地震,32(2):193-201.
王彬,吴国华,苏有锦,等.2015.宾川地震信号发射台的选址、建设及初步观测结果[J].地震研究,38(1):1-6.
王俊,郑定昌,郑江蓉,等.2016.利用背景噪声自相关研究芦山M7.0地震震源区地壳相对波速的时空变化特征[J].地震地质,38(1):15-168
王鹏,郑建常,谭毅培.2016.利用重复地震研究山东乳山地区地壳介质波速变化[J].地震学报,38(5):728-738.
王伟涛,王宝善,蒋生淼,等.2017.利用气枪震源探测大陆浅部的地震学研究回顾与展望[J].地震研究,40(4):514-524.
魏芸芸,王海涛,苏金波,等.2016.新疆2次中强地震前气枪震源反射波震相走时异常变化初步研究[J].中国地震,32(2):270-281.
夏季,金星,蔡辉腾,等.2016.大容量气枪震源子波时频特性及其影响因素[J].中国地震,32(2):249-260.
杨微,葛洪魁,王宝善,等.2010.由精密控制人工震源观测到的绵竹5.6级地震前后波速变化[J].地球物理学报,53(5):1149-1157.
郑定昌,王俊.2017.基于背景噪声的川滇地区勒夫波层析成像[J].地震学报,39(5):633-647.
Bensen G D,Ritzwoller M H,Barmin M P,et al.2010.Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements[J].Geophysical Journal of the Royal Astronomical Society,169(3):1239-1260.
Nadeau R M,Foxall W,Mc Evilly T V.1995.clustering and periodic recurrence of microearthquakes on the San Andreas faults at Parkfield,California[J].Science,267(5179):503-507.
Niu F,Silver P G,Daley T M,et al.2008.Preseismic velocity changes observed from active source monitoring at the Parkfield SAFOD drill site[J].Nature,454:204-208,doi:10.1038/nature07111.
Schaff D P,Beroza G C.2004.Coseismic and postseismic velocity changes measured by repeating earthquakes[J].Journal of Geophysical Research,109,B10302,doi:10.1029/2004JB003011.
Wang B S,Ge H K,Yang W,et al.2012.Transmitting seismic station monitors fault zone at depth[J].Eos Transactions American Geophysical Union,93(5):49-50.
Wang B S,Zhu P,Chen Y,et al.2008.Continuous subsurface velocity measurement with coda wave interferometry[J].J Geophys Res,113,B12313,doi:10.1029/2007JB005023.
Yao H,Vander Hilst R D,De Hoop M V.2006.Surface-wave array tomography in SE Tibet from ambient seismic noise and two-station analysis-Ⅰ,Phase velocity maps[J].Geophysical Journal International,166(2):732-744.
Zheng D C,Saygin E,Cummins P,et al.2017.Transdimensional Bayesian seismic ambient noise tomography across SE Tibet[J].Journal of A-sian Earth Sciences,134:86-93.