地震研究

为研究噪音对主动源信号走时变化提取精度的影响,采用对比数值实验的方法。按照常规流程,首先用反褶积去除震源激发时间的不确定性干扰,压缩子波以得到更加尖锐的震相,由于发现反褶积会降低信号的信噪比,于是提出了台差法来代替反褶积矫正气枪激发的不确定性,再结合干涉法提取走时变化,并定量对比了两者的走时变化提取精度,最后尝试用台差法提取主动源走时的日变化。结果表明,台差法可以有效矫正震源激发时刻的影响,且不降低信噪比,从而也能获得较高走时变化提取的精度。

We adapt numerical tests to study the influence of noises on the precision of travel time drift of active source signals.In traditional ways,deconvolution is used to eliminate the uncertainty of the excitation time of active source.However,this process will significantly lower the signal-noise ratio and thus lead the decline of precision.We put forward a new method named pair difference to replace deconvolution for the sake of eliminating the influence of the active source.The results show that pair difference can effectively eliminate the impact of active source and will not affect the signal-noise ratio,thus improving the precision of extracting travel time drifts.

引言
1 干涉法提取走时变化简介
2 干涉法提取走时变化可能影响因素探究
3 替代方案——台差法及其有效性实证
4 讨论
5 结论

图1 干涉法提取走时示意图<br/>Fig.1 Schematic diagram of interferometry

图1 干涉法提取走时示意图
Fig.1 Schematic diagram of interferometry

图2 常规走时提取流程<br/>Fig.2 The traditional processing flowchart to extract the travel time drift of signals

图2 常规走时提取流程
Fig.2 The traditional processing flowchart to extract the travel time drift of signals

图3 台站及地震分布图<br/>Fig.3 The station network and the distribution of earthquake larger than MW4

图3 台站及地震分布图
Fig.3 The station network and the distribution of earthquake larger than MW4

图4 数值实验波形图和震源时间函数图<br/>Fig.4 Waveform used in the numerical and source time function map

图4 数值实验波形图和震源时间函数图
Fig.4 Waveform used in the numerical and source time function map

图5 53281台数据经过不同处理流程得到的波形图<br/>Fig.5 The waveform of 53281 after different processing flowchart

图5 53281台数据经过不同处理流程得到的波形图
Fig.5 The waveform of 53281 after different processing flowchart

图6 53281台数据在不同处理流程下提取的走时变化图<br/>Fig.6 Travel time drifts extracted from stacked waveform of station 53281 under four different processing flowcharts

图6 53281台数据在不同处理流程下提取的走时变化图
Fig.6 Travel time drifts extracted from stacked waveform of station 53281 under four different processing flowcharts

图7 滤波和滤波之后反褶积在提取不同信噪比信号走时变化时的表现<br/>Fig.7 Travel time drifts from filtered and unfiltered signals under continuous changeable noise and different process

图7 滤波和滤波之后反褶积在提取不同信噪比信号走时变化时的表现
Fig.7 Travel time drifts from filtered and unfiltered signals under continuous changeable noise and different process

图8 CKT0台和53281台走时变化<br/>Fig.8 Travel time drifts of stations CKT0 and 53281

图8 CKT0台和53281台走时变化
Fig.8 Travel time drifts of stations CKT0 and 53281

图9 气压变化与四个地震台信号走时变化图<br/>Fig.9 Barometric pressure change and the travel time drifts of the four studied stations

图9 气压变化与四个地震台信号走时变化图
Fig.9 Barometric pressure change and the travel time drifts of the four studied stations

图10 53274和53281台一天内的走时变化<br/>Fig.10 Travel time drift extracted from Stations 53274 and 53281 in one day

图10 53274和53281台一天内的走时变化
Fig.10 Travel time drift extracted from Stations 53274 and 53281 in one day

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.
罗桂纯,王宝善,葛洪魁,等.2006.气枪震源在地球深部结构探测中的应用研究进展[J].地球物理学进展,21(2):400-407.
王宝善,杨微,王伟涛,等.2011.宾川气枪信号发射台性能分析[C]//中国地球物理学会年会第二十七届年会论文集.
王彬,杨润海,王宝善,等.2012.地震波走时变化精确测量的实验研究[J].云南大学学报:自然科学版(增刊2):15-20.
王伟涛,王宝善,葛洪魁,等.2009.利用主动震源检测汶川地震余震引起的浅层波速变化[J].中国地震,25(3):223-233.
杨微,王宝善,葛洪魁,等.2013.大容量气枪震源主动探测技术系统及试验研究[J].中国地震,29(4):399-410.
LAY T,WALLACE T C.1995.Modern global seismology[M].Manhattan Academic press.
LEARY P C,MALIN P E,PHINNEY R A,et al.1979.Systematic monitoring of millisecond travel time variations near Palmdale,California[J].Journal of Geophysical Research Atmospheres,84(B2):659-666.
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(7201):204-208.
NUR A.1971.Effects of stress on velocity anisotropy in rocks with cracks[J].Journal of Geophysical Research,76:2022-2034.
SCHAFF D P,BEROZA G C.2004.Coseismic and postseismic velocity changes measured by repeating earthquakes[J].Journal of Geophysical Research:Solid Earth,109(B10):67-85.
SILVER P G,DALEY T M,NIU F,et al.2007.Active Source Monitoring of Cross-Well Seismic Travel Time for Stress-Induced Changes[J].Bulletin of the Seismological Society of America,97(1b):281-293.
SIMMONS G.1964.Velocity of shear waves in rocks to 10 kilobars,1[J].Journal of Geophysical Research Atmospheres,69(6):1123-1130.
SPANE F A.2002.Considering barometric pressure in groundwater flow investigations[J].Water Resources Research,38(6):14-1—14-18.
WALSH J B.1965.The Effect of Cracks on the Compressibility of Rock[J].Journal of Geophysical Research Atmospheres,70(2):381-389.
WANG B,ZHU P,CHEN Y,et al.2008.Continuous subsurface velocity measurement with coda wave interferometry[J].Journal of Geophysical Research:Solid Earth,113(B12):36-44.
YAMAMURA K,SANO O,UTADA H,et al.2003.Long-term observation of in situ seismic velocity and attenuation[J].Journal of Geophysical Research Solid Earth,108(B6):1-5.
YUKUTAKE H.1988.In situ measurements of elastic wave velocity in a mine,and the effects of water and stress on their variation[J].Tectonophysics,149(1-2):165-175.

备注

引言

1 干涉法提取走时变化简介

2 干涉法提取走时变化可能影响因素探究

3 替代方案——台差法及其有效性实证

4 讨论

5 结论

期刊信息