Study on the relationship between geothermal exploitation and seismic activity in Xi＇an region

Based on the analysis of the induced earthquakes in China and abroad, we get some ideas about earthquakes induced by pumping water out of a well or injecting water into a well. The induced earthquakes usually occur near the well, and they are generally small earthquakes. The earthquake sources are shallow, and they belong to the main shock-after shock type of earthquake or the swarm-type of earthquake. The magnitude and the quantity of the induced earthquakes obviously depend on the pressure and the quantity of water pumped or injected. These earthquakes happen as soon as pumping or injecting occurrence, or after ten or twenty days, they may occur at the time of injecting mud or injecting high pressure water when a well is being drilled, or at the time when the ground water is being normally exploited. A large quantity of hot water has been exploited since 1990 in Xi＇an, and the quantity of water exploited has been increasing year by year, as a result the groundwater level has been dropping with the water pumped out and the water level is high in summer and low in winter. The earthquakes in Xi＇an region belong to the solitary-type and they spread outside Xi＇an city where the wells are concentrated but no earthquake happens.The seismic frequency and the energy released have no relation with the quantity of water exploitation or the water level in the well. It is considered that geothermal exploitation does not induce earthquakes in and around Xi＇an because of its specially geological condition.     

西安市地热水开采的现状分析

通过对西安地区承压井和地热井水位及开采量和分层沉降量等资料分析后得出：西安市区地面沉降和地裂缝活动是由于过量开采承压水所引起的。目前西安市深层地热水开采还没有加剧西安市区地沉降和地裂缝活动。控制并减少承压水的开采量，是减弱西安市区地面沉降和地裂缝活动的最在效的方法之一。     

西安市地热水开采与地面沉降、地裂缝关系的分析

西安市地面沉降和地裂缝在空间分布上有明显的一致性 ,它们的发展过程和强度变化在时间上也有明显的同步性。诱发地面沉降的主因是过量开采承压水导致承压水位下降 ,含水层介质的孔隙压力减小 ,黏性土层释水压密导致地面永久性的沉降 ,而且浅层的释水压密量大于深层 ;不均匀的地面沉降又诱发了地裂缝。无论是地热井水位或热水开采量的变化 ,还是分层沉降量的观测资料都表明 ,目前西安市深层热水开采还没有加剧西安市的地面沉降和地裂缝活动。控制并减少承压水的开采量 ,是减弱西安市地面沉降和地裂缝活动的最有效的方法     

Study on the relationship between geothermal exploitation and seismic activity in Xi''''an region

IntroductionGeothermal energy is a new and clear energy resource. It is very useful in heating and generating electricity and medical treating. The Assembly of International Environmental Protection in 1992 predicted that the usage and development of geothermal energy would exceed the traditional energy such as oil and coal, and its developmental prospect will be very bright.There are great geothermal resources in Weihe basin. The average value of heat flow in Weihe basin is 7.88(10(2 W/m2…     

西安地区的地热水开采与诱发地震关系的研究

通过对国内外众多震例的分析，发现了向深井抽（注）水（液体）诱发地震的一些普遍规律:诱发地震的震中在井位附近，震级小，震源浅且多为主余震型或震群型，绝少有孤立型地震发生；诱发地震的多少和大小与抽（注）水的压力和数量相关；诱发地震一般在钻井时注入泥浆、洗井时注入高压清水或正常的地下水开采等３种情况时马上发生，或滞后1～20天发生. 1990年以来西安地区大量开采地下热水，采水量逐年增多，水位逐年下降且具有夏高冬低等特征．西安地区的地震多为孤立型，震源都在10ｋｍ 以下，且多分布在西安外围地区，井群较密的城郊区鲜有地震发生；地震的频次和能量的释放与西安地区的地热水开采量和水位变化无明显的关系．因此，西安地区的地热水开采并未诱发西安及其周围地区的地震．