与地方中强震伴生的钻孔应变脉冲信号特征分析
|
摘要
分量式钻孔应变观测是当今国际上地壳岩石应变相对测量的主流方法,其中探寻异常信号与地震的关系是地震预测的首要任务。文章选取云南省腾冲地震台8年钻孔应变观测资料进行分析,发现原始分钟值曲线上记录到一种肉眼可识别的脉冲信号,波形与地震波相近。将其出现的时间和振幅与地方中强震(M_S>3.0,震中距<100km)的震级做逐年对比分析,结果表明二者存在一定的伴生现象。应变仪四个分量元件不一定都能同时记录到该种信号,气压、水位和人为干扰不是引起该信号的原因。为判断该信号的性质,进一步搜集当地小震目录(M_S=2.0～3.0)和微震目录(M_S=0.1～1.9),发现一半信号原来是应变小震波(震中距一般<70km),另有24%为应变微震波(震中距大多在16km以内),剩余的26%没有对应地震,推测地震目录可能记录不全。认为这部分信号也应是小震或微震引起,均由钻孔附近岩石的微破裂所致,与区域性地震活动存在一定的关联。
Component-type borehole strain observation is the mainstream method of relative measurement of crustal rock strain in the world today,among which exploring the relationship between abnormal signals and earthquakes is the primary task of earthquake prediction.In this study,the 8-year borehole strain observation data of Tengchong seismic station in Yunnan Province were selected for analysis.It was found that an identifiable impulse signal is recorded on the original minute-value curve with a period of approximately 2～4 minutes and an amplitude of(4～30)×10-10.The variation of tension and pressure is uncertain each time,but the waveform is similar to the seismic wave.The time and amplitude of their occurrence were compared with the magnitude of local moderate-strong earthquakes(M_S>3.0,epicentral distance<100 km)year by year.The results show that there are some concomitant phenomena between them.The four components of the strainmeter can not always record the signal at the same time.Air pressure,water level and human disturbance are not the causes of the signal.In order to judge the nature of the signal,we further collected the local catalogue of small earthquakes(M_S2.0～3.0)and the catalogue of micro-earthquakes(M_S0.1～1.9).We found that half of the signals are originally strained small-earthquakes(the epicentral distance is generally less than 70 km),24%are strained micro-earthquakes(the epicentral distance is mostly less than 16 km),and the remaining 26%do not correspond to earthquakes.It is speculated that the catalogue of earthquakes may not record completely.Based on the analysis we think that this part of the signal should also be caused by small earthquakes or microseisms,all of which are caused by micro-rupture of rocks near boreholes,and are related to regional seismicity.
Component-type borehole strain observation is the mainstream method of relative measurement of crustal rock strain in the world today,among which exploring the relationship between abnormal signals and earthquakes is the primary task of earthquake prediction.In this study,the 8-year borehole strain observation data of Tengchong seismic station in Yunnan Province were selected for analysis.It was found that an identifiable impulse signal is recorded on the original minute-value curve with a period of approximately 2～4 minutes and an amplitude of(4～30)×10-10.The variation of tension and pressure is uncertain each time,but the waveform is similar to the seismic wave.The time and amplitude of their occurrence were compared with the magnitude of local moderate-strong earthquakes(M_S>3.0,epicentral distance<100 km)year by year.The results show that there are some concomitant phenomena between them.The four components of the strainmeter can not always record the signal at the same time.Air pressure,water level and human disturbance are not the causes of the signal.In order to judge the nature of the signal,we further collected the local catalogue of small earthquakes(M_S2.0～3.0)and the catalogue of micro-earthquakes(M_S0.1～1.9).We found that half of the signals are originally strained small-earthquakes(the epicentral distance is generally less than 70 km),24%are strained micro-earthquakes(the epicentral distance is mostly less than 16 km),and the remaining 26%do not correspond to earthquakes.It is speculated that the catalogue of earthquakes may not record completely.Based on the analysis we think that this part of the signal should also be caused by small earthquakes or microseisms,all of which are caused by micro-rupture of rocks near boreholes,and are related to regional seismicity.
引文
[1]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.
[2]张宝红.美国板块边界观测(PBO)中的钻孔应变观测设备[J].大地测量与地球动力学,2010,30(增刊Ⅰ):40-44.
[3]刘序俨,王紫燕,方宏芳.对当前四分量钻孔应变观测的审视---以应变不变量为标尺[J].地球物理学报,2014,84(6):895-900.
[4]Roeloffs E.Tidal calibration of Plate Boundary Obervatory borehole strainmeters:Roles of vertical and shear coupling[J].JGR,2010,115,B06405:25.
[5]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.
[6]欧阳祖熙,张钧,陈征.地壳形变深井综合观测技术的新进展[J].国际地震动态,2009(11):1-13.
[7]邱泽华,张宝红,池顺良,等.汶川地震前姑咱台观测的异常应变变化[J].中国科学:地球科学,2010,40(8):1031-1039.
[8]邱泽华,唐磊,张宝红,等.用小波-超限率分析提取宁陕台汶川地震体应变异常[J].地球物理学报,2012,55(2):538-546.
[9]刘琦,张晶,池顺良,等.2013年芦山MS7.0地震前后姑咱台四分量钻孔应变时频特征分析[J].地震学报,2013,36(5):770-779.
[10]骆鸣津,顾梦林,杨毅.用固体潮观测资料将钻孔应变变化换算为地层的应力变化[J].地壳形变与地震,2000,20(1):73-78.
[11]龚汉松,杜传杨.声发射预报地震的岩体力学分析[J].地球科学进展,2008,23(12):1293-1298.
[2]张宝红.美国板块边界观测(PBO)中的钻孔应变观测设备[J].大地测量与地球动力学,2010,30(增刊Ⅰ):40-44.
[3]刘序俨,王紫燕,方宏芳.对当前四分量钻孔应变观测的审视---以应变不变量为标尺[J].地球物理学报,2014,84(6):895-900.
[4]Roeloffs E.Tidal calibration of Plate Boundary Obervatory borehole strainmeters:Roles of vertical and shear coupling[J].JGR,2010,115,B06405:25.
[5]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.
[6]欧阳祖熙,张钧,陈征.地壳形变深井综合观测技术的新进展[J].国际地震动态,2009(11):1-13.
[7]邱泽华,张宝红,池顺良,等.汶川地震前姑咱台观测的异常应变变化[J].中国科学:地球科学,2010,40(8):1031-1039.
[8]邱泽华,唐磊,张宝红,等.用小波-超限率分析提取宁陕台汶川地震体应变异常[J].地球物理学报,2012,55(2):538-546.
[9]刘琦,张晶,池顺良,等.2013年芦山MS7.0地震前后姑咱台四分量钻孔应变时频特征分析[J].地震学报,2013,36(5):770-779.
[10]骆鸣津,顾梦林,杨毅.用固体潮观测资料将钻孔应变变化换算为地层的应力变化[J].地壳形变与地震,2000,20(1):73-78.
[11]龚汉松,杜传杨.声发射预报地震的岩体力学分析[J].地球科学进展,2008,23(12):1293-1298.