【作者】 刘耀炜；

【导师】 李慈君； 邵景力；

【作者基本信息】 中国地质大学（北京） ， 水文学及水资源， 2009， 博士

【摘要】 地下水物理动态中的井孔水位、水温观测是地震预测预报中重要的前兆观测项目。本文通过远场地震波的动力加载作用和人工爆破动力加载作用分析,研究井-含水层系统井孔水位、水温动态响应特征,旨在揭示地震孕育过程中地下水物理动态与地壳介质应力应变之间的关系。本文统计了2004年印尼苏门答腊8.7级地震和2008年四川汶川8.0级地震中国大陆地震地下水观测网井孔水位、水温同震效应类型和特征,提出了“热对流-传导模式”并对井孔水位震荡、水温下降的物理机制进行了解释;应用600kg炸药在10m深地下的野外爆破试验结果,分析了爆破动力加载对井孔流量的影响特征,并与地震波效应进行对比分析。以上统计分析、数值模拟与野外试验获得以下研究结果。1、中国大陆103个井孔有78个记录到苏门答腊8.7级地震水位同震效应;218个井孔有196个记录到汶川8.0级地震水位同震效应。113个井孔有69个记录到苏门答腊8.7级地震水温同震效应;216个井孔有132个记录到汶川8.0级地震水温同震效应;两次地震对比分析表明,井孔水温下降比例高于水温上升,水位震荡比例高于其它类型;汶川8.0级地震对中国大陆某些地区的影响大于苏门答腊8.7级地震,表明这些地区的应力状态产生了新的变化,对震情跟踪有重要的指示意义。2、井孔水位振荡伴随水温的快速下降主要是由于井孔周围含水层垂直渗流作用引起的,地震波结束后水温缓慢恢复是围岩热传导效应。用“热对流-传导模式”完成的模拟结果表明,含水层中的水混入井孔水的混合比θ直接影响水温下降速度,θ越大混合速度越快;而温度下降幅度除了与θ有关,还与混入井孔的初始水温T0有关;影响水温恢复快慢的主要因素是井孔周围垂直渗流混合区范围的大小。在不同的井-含水层系统中,井水温度下降的幅度是受该井本身水文地质环境条件控制;在同一个井-含水层系统中,地震波作用的大小以及水位振荡幅度与水温下降的幅度具有指数统计关系。3、爆破试验在地表布设5套强震仪,在井下布设1台地声仪。用强震记录直接计算得到了在150m深处的井底由于SH波场而引起介质的附加应力:切向σt=318.2Pa,径向σn=735.7Pa,垂直σu=2851Pa;爆破时在井底150m处接受的地声声波效声压约为110Pa;爆破激发的能量相当于ML1.3级地震(MS0.37),可以模拟100km以远发生的中强地震对流体观测点的作用。地震波和爆破动力加载作用产生的弹性冲击作用会使井水流量瞬时增加,而由地震波(或爆破)激发的流体孔隙压扩散造成了2天后流量的显著增加。更多还原

【Abstract】 Observations of borehole water level and water temperature in the physical dynamics of groundwater are the important observed components of precursores for earthquake prediction. In this paper, by analyzing the dynamical loading of far-field seismic wave and artifical explosion, the dynamic response characteristics of borehole water level and water temperature in well-aquifer system is investigated and deeply studied in order to reveal the relationship between physical dynamics of groundwater and crustal stress and strain in the process of earthquake gestation.In this study, we made a statistic of types of coseismic effects and characteristics of groundwater level and water temperature in the boreholes of earthquake ground water net between 2004 Sumatra earthquake with magnitude 8.7 in Indonesia and the 2008 Wenchuan 8.0 earthquake in the Chinese mainland. Through these work, we proposed the "thermal convection - conduction model" and interpreted physical mechanism of the borehole water level shock as well as water temperature decline. Using explosion test results, which was generated by 600kg -weighed explosives in the depth of 10m in underground explosion field, we analyzed the impact characteristics of explosion dynamic loading on the borehole flow, and compared them with seismic wave effects. By the statistical analysis, numerical simulation and field tests above-mentioned, the key findings are obtained as follows.1. It is found that in Chinese mainland 78 out of 103 boreholes tracked records of water level coseismic effect associated with the Sumatra 8.7earthquake, while water level in 196 out of 218 boreholes showed coseismic responses to Sichuan 8.0 earthquake. Moreover 69 out of 113 boreholes recorded cosesimic water temperature effect related to the Sumatra earthquake, and 132 out of 216 boreholes demonstrated cosesimic water temperature responses to Sichuan 8.0 earthquake. Through comparison and analysis of the two earthquakes related responses, it found out that the proportion of borehole numbers with borehole temperature decreasing is higher than that of temperature-increasing ones, with oscillations type higher than other types. The impact of Wenchuan 8.0 earthquake on some areas of China is greater than Sumatra 8.7-magnitude earthquake, indicating that the stress state in these areas has changed, which has inductive indicating significance to the earthquake tracking.2. Borehole water level oscillations with rapid decline of temperature are mainly caused by the vertical seepage in the aquifer surrounding the borehole, and the slow recovery of the water temperature after the transportation of seismic waves are contributed to the surrounding rock thermal conduction. Using "thermal convection - conduction model" to perform the simulation , it shows that the mixture rate (θ) of the aquifer water with the borehole water has directly impact on the decline of water temperature, with greaterθresulting in higher mixing velocity. Besidesθ, temperature decrease depends on the initial mixed borehole temperature T0 . It is seen from the calculated results that the main factor impacting on water temperature recovery velocity is the size of vertical seepage mixture area around the borehole. A key finding is that ,for different wells - aquifer systems, the decline amplitude of well water temperatures is dominated by hydrological environment of the well itself. While, for the same well - aquifer system, the exponential statistic relationship between the intensity of seismic wave as well as water level oscillation has been obtained.3. In the explosion test, five sets of strong motion seismograph are installed on the earth surface with one earth acoustical instrument installed in the well. With the strong motion records, the additional stresses induced by SH waves in the depth of 150m have be obtained . The tangentialσt, radialσn, and vertical stressσu are 318.2Pa, 735.7Pa and 2851Pa, respectively. Results show that the acoustical wave pressure received in the depth of 150m from the well bottom reaches approximate110Pa. While Energy induced by explosion is equivalent to ML1.3 earthquake (MS 0.37), which can simulates effects of medium and strong earthquakes occurring beyond 100km on fluid observation points. It proves that the flow of wells is instantaneously enhanced by seismic waves and elastic impacts due to explosion dynamical loading. While porous pressure diffusion induced by seismic waves or explosion contributes to the considerable increase of well flows after two days.更多还原