浙江地下流体在汶川8.0级地震中的映震效应研究
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摘要
通过"十五"改造,浙江省目前有地震地下流体观测台站5个,10项测项,主要是水位,水温和水氡。在2008年5月12日四川汶川8.0级地震中有明显映震效应的台站为100%,测项为80%。水氡测值表现为临震向上突跳异常,最大异常幅度达23.7%,创历史之最;水温测项主要出现临震突跳或阶跃;水位测项主要是同震效应现象,为水震波引起的脉冲和阶跃变化。认为同震效应可能是地震发生后地震波传播引起的含水层弹性形变所致。并且认为观测效果不一定是井位越深越好,而是要看含水层封闭情况和仪器观测传感器的位置,没有明显的优劣之分。好的静水位观测井记录的水震波效果明显优于动水位观测井。由于前兆数字化仪器采样率相对较底(1次/min),记录数据缺失较多,记录的同震变化波形不完整,很难进一步分析。
After the reconstruction in"the tenth-five year plan",there are five underground fluid observation stations,with ten measure items,mainly water level,water temperature and radon, in Zhejiang Province.Before the Wenchuan M 8.0 earthquake in Sichuan Province on May 12,2008,100 percent of the stations,80 percent of the observation items have shown obvious earthquake response.The Radon measurements showed an imminent upward jump anomaly.The maximum anomalous amplitude is as high as 23.7%,and created a historic record. The water temperature mainly showed imminent jump or step.The water level showed co-earthquake effect phenomenon:pulse and step variation cased by water oscillation wave. It is considered that the co-earthquake effect may be attributed to the elastic deformation of water-bearing stratum,which in turn resulted in the propagation of seismic wave after the earthquake occurrence.It is also considered that the observation effect is not always better when the well level is deeper.The main factors are the seal status of water-bearing stratum and the position of the sensor of observation equipment.There is no good or bad condition. The record effect of water oscillation wave in a good stable water level observation well is much better than that in dynamic water level observation well.Since the relative lower sampling rate (one per minute) of the digital precursory equipment,many record data are lost. The waveform of co-earthquake variance is not integrity,and the further analysis is hardly possible.
After the reconstruction in"the tenth-five year plan",there are five underground fluid observation stations,with ten measure items,mainly water level,water temperature and radon, in Zhejiang Province.Before the Wenchuan M 8.0 earthquake in Sichuan Province on May 12,2008,100 percent of the stations,80 percent of the observation items have shown obvious earthquake response.The Radon measurements showed an imminent upward jump anomaly.The maximum anomalous amplitude is as high as 23.7%,and created a historic record. The water temperature mainly showed imminent jump or step.The water level showed co-earthquake effect phenomenon:pulse and step variation cased by water oscillation wave. It is considered that the co-earthquake effect may be attributed to the elastic deformation of water-bearing stratum,which in turn resulted in the propagation of seismic wave after the earthquake occurrence.It is also considered that the observation effect is not always better when the well level is deeper.The main factors are the seal status of water-bearing stratum and the position of the sensor of observation equipment.There is no good or bad condition. The record effect of water oscillation wave in a good stable water level observation well is much better than that in dynamic water level observation well.Since the relative lower sampling rate (one per minute) of the digital precursory equipment,many record data are lost. The waveform of co-earthquake variance is not integrity,and the further analysis is hardly possible.
引文
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邱永平.2004． 宁波地震台ZK03井水温异常与日本北海道8． 0级地震的关系[J].地震地磁观测与研究,25(6) :49～54
邱永平.2006． 宁波地震台水位、地倾斜在印尼8． 7、 8． 5级地震中的同震变化现象[J].内陆地震,20(4) :336～341
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邱永平.2007． 浙江温州4． 6级地震群前宁波地震台水温异常特征讨论[J].地震地磁观测与研究,28(3) :13～16
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