分量钻孔应变观测的理论频响分析
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摘要
为了探讨分量钻孔应变地震波测量的可能性,本文引入空孔对入射平面弹性P波散射模型来研究分量钻孔应变观测的理论频响。通过计算空孔对入射波的散射波场,从而得到钻孔直径的变化。类似于分量钻孔应变静态观测,引入不同的钻孔直径变化的组合,来反映入射P波的面应变和最大剪切应变。不同的钻孔直径变化组合的理论频响受入射P波的无量纲波数k1a和钻孔周边介质的泊松比影响。分量钻孔应变波观测等效为低通滤波器,■和■1%频带宽截止k_1a为0.061(ν=0.25),■1%频带宽截止k_1a为0.037(ν=0.25)。在测量钻孔直径变化的传感器带宽足够高的情况下,可实现入射高频地震应变波的定量测量。
In order to discuss the possibility of measuring seismic strain wave by borehole tensor strainmeters,a model of the scattering of plane elastic P-wave by an empty borehole is introduced to investigate theoretical frequency response of a borehole tensor strainmeter. The calculation of scattering waves around the borehole gives diameter change of the borehole. Similar with the static cases,different gauge combinations are introduced to reflect the areal strain and the maximum shear strain of the incident wave. It is shown that the theoretical frequency responses different gauge combinations are determined by non-dimensional wave numberk1 a of the incident wave and Poisson ratio of surrounding rock. Borehole tensor strain observation is equivalent to a low pass filter. the 1% cut-off k_1 aof bandwidth of ■ and.■. is 0.061( ν = 0.25) and 1% cut-off k_1 a of bandwidth of ■ is 0.037( ν = 0.25). In the case that the sensor bandwidth is high enough to measure borehole diameter,quantitative measurement of the incident highfrequency seismic strain wave could be realized.
In order to discuss the possibility of measuring seismic strain wave by borehole tensor strainmeters,a model of the scattering of plane elastic P-wave by an empty borehole is introduced to investigate theoretical frequency response of a borehole tensor strainmeter. The calculation of scattering waves around the borehole gives diameter change of the borehole. Similar with the static cases,different gauge combinations are introduced to reflect the areal strain and the maximum shear strain of the incident wave. It is shown that the theoretical frequency responses different gauge combinations are determined by non-dimensional wave numberk1 a of the incident wave and Poisson ratio of surrounding rock. Borehole tensor strain observation is equivalent to a low pass filter. the 1% cut-off k_1 aof bandwidth of ■ and.■. is 0.061( ν = 0.25) and 1% cut-off k_1 a of bandwidth of ■ is 0.037( ν = 0.25). In the case that the sensor bandwidth is high enough to measure borehole diameter,quantitative measurement of the incident highfrequency seismic strain wave could be realized.
引文
[1]邱泽华,石耀霖.观测应变阶在地震应力触发研究中的应用[J].地震学报,2004,26(5):481-488.
[2] Linde A T,Agustsson K,Sacks I S,et al. Mechanism of the 1991 eruption of Hekla from continuous borehole strain monitoring[J]. Nature, 1993, 365(6448):737-740.
[3]邱泽华,周龙寿,池顺良.用超限率分析法研究汶川地震的前兆应变变化[J].大地测量与地球动力学,2009,29(4):1-4.
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[7]池顺良,武红岭,骆鸣津.钻孔应变观测中潮汐因子离散性与各向异性原因探讨——“十五”数字地震观测网络分量钻孔应变仪首批观测资料分析解释[J].地球物理学进展,2007,22(6):1746-1753.
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[11]毕永强,王琳,王宝鹏,等.安图M3.7及柳树M4.3地震前后YRY-4钻孔应变观测曲线异常形态[J].世界地质,2013,32(3):579-583.
[12] Pan Z S,Xu Y G,Lai A J. Characteristics of borehole strain anomalies in Wushi before earthquakes[J].Inland Earthquake,2015,29(1):43-49.
[13]赵慧琴,王艳,张肖,等.易县地震台四分量钻孔应变观测震前异常特征[J].地震地磁观测与研究,2017(4):132-136.
[14] Qiu Z H,Zhang B H,Chi S L,et al. The abnormal strain changes observed in Zagu station before the Wenchuan earthquake[J]. Scientic Sinca(Terrae),2010,40(8):1031-1039.
[15]池顺良.用于地层应力—应变观测的压容式钻孔应变仪[J].地震,1985(3):20-31.
[16]邱泽华,池顺良. YRY-4型钻孔应变仪观测的P波剪应变[J].地震,2013(4):64-70.
[17] Pao Y H,Mow C C,Achenbach J D. Diffraction of elastic waves and dynamic stress concentrations[M].New York:Crane Russak and Company,Inc,1973.
[18] Gladwin M T,Hart R. Design parameters for borehole strain instrumentation[J]. Pure&Applied Geophysics,1985,123(1):59-80.
[19]甘本祓,吴万春.现代微波滤波器的结构与设计[M].北京:科学出版社,1974.
[20] Savin G N. Stress concentration around holes[M].Pergamon Press,1961.
[21]陈子光.岩石力学性质与构造应力场[M].北京:地质出版社,1986.
[22]刘迎春,叶湘滨.传感器原理、设计与应用[M].北京:国防工业出版社,2015.
[23]陆基孟.地震勘探原理[M].北京:石油工业出版社,2011.
[2] Linde A T,Agustsson K,Sacks I S,et al. Mechanism of the 1991 eruption of Hekla from continuous borehole strain monitoring[J]. Nature, 1993, 365(6448):737-740.
[3]邱泽华,周龙寿,池顺良.用超限率分析法研究汶川地震的前兆应变变化[J].大地测量与地球动力学,2009,29(4):1-4.
[4] Linde A T,Gladwin M T,Johnston M J S,et al. A slow earthquake sequence on the San Andreas fault[J].Nature,1996,383(6595):65-68.
[5] Sacks I S, Linde A T, Suyehiro S, et al. Slow earthquakes and stress redistribution[J].Tectonophysics,1978,275(5681):599-602.
[6]吴立恒,李涛,陈征,等. RZB-2型电容式钻孔应变仪研究进展[J].地壳构造与地壳应力文集,2006(18):131-138.
[7]池顺良,武红岭,骆鸣津.钻孔应变观测中潮汐因子离散性与各向异性原因探讨——“十五”数字地震观测网络分量钻孔应变仪首批观测资料分析解释[J].地球物理学进展,2007,22(6):1746-1753.
[8] Gladwin M T. High-precision multi-component borehole deformation montoring[J]. Review of Scientific Instruments,1985,55(12):2011-2016.
[9]张宝红.美国的板块边界观测(PBO)计划[J].大地测量与地球动力学,2004,24(3):105-108.
[10]陈会忠.中国数字地震观测网络工程的科技进步[J].防灾博览,2007(5):20-21.
[11]毕永强,王琳,王宝鹏,等.安图M3.7及柳树M4.3地震前后YRY-4钻孔应变观测曲线异常形态[J].世界地质,2013,32(3):579-583.
[12] Pan Z S,Xu Y G,Lai A J. Characteristics of borehole strain anomalies in Wushi before earthquakes[J].Inland Earthquake,2015,29(1):43-49.
[13]赵慧琴,王艳,张肖,等.易县地震台四分量钻孔应变观测震前异常特征[J].地震地磁观测与研究,2017(4):132-136.
[14] Qiu Z H,Zhang B H,Chi S L,et al. The abnormal strain changes observed in Zagu station before the Wenchuan earthquake[J]. Scientic Sinca(Terrae),2010,40(8):1031-1039.
[15]池顺良.用于地层应力—应变观测的压容式钻孔应变仪[J].地震,1985(3):20-31.
[16]邱泽华,池顺良. YRY-4型钻孔应变仪观测的P波剪应变[J].地震,2013(4):64-70.
[17] Pao Y H,Mow C C,Achenbach J D. Diffraction of elastic waves and dynamic stress concentrations[M].New York:Crane Russak and Company,Inc,1973.
[18] Gladwin M T,Hart R. Design parameters for borehole strain instrumentation[J]. Pure&Applied Geophysics,1985,123(1):59-80.
[19]甘本祓,吴万春.现代微波滤波器的结构与设计[M].北京:科学出版社,1974.
[20] Savin G N. Stress concentration around holes[M].Pergamon Press,1961.
[21]陈子光.岩石力学性质与构造应力场[M].北京:地质出版社,1986.
[22]刘迎春,叶湘滨.传感器原理、设计与应用[M].北京:国防工业出版社,2015.
[23]陆基孟.地震勘探原理[M].北京:石油工业出版社,2011.
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