【摘要】 基于川滇地区前兆台网资料,结合异常现场核实工作结果,对鲁甸6.5级地震前的地下流体异常现象进行了总结。遵循地震分析预报的基本思路,按照长期、中期、短期趋势异常、临震异常和宏观异常阐述了鲁甸6.5级地震前地下流体典型异常现象。结果表明,长期和中期趋势背景异常主要出现在距震中300~500km范围,短期趋势和临震及宏观异常集中于震中区100km范围内。这种流体异常特征反映了在较高密度的观测点区域,可以观测到流体活动加剧的前兆现象,有利于判定地震危险区和短期阶段跟踪分析。区域应力加载作用可能引起的断裂带裂隙的开启与闭合,导致温泉和井水温、深部气体与承压井水位的持续变化;水岩反应加剧和地下水混合作用增强,使地下水离子组分浓度发生变化,甚至导致显著宏观异常。在一定密度的前兆观测地区,能够获取用于判定地震危险性的前兆信息。更多还原

【Abstract】 We summarized the fluid anomalies associated with the Ludian MS6. 5 earthquake based on the Sichuan and Yunnan earthquake network observations and field survey. The fluid anomalies were divided into long-term,medium-term,short-term,imminent and macroscopic anomalies according to the basic principles of earthquake forecasting. The long-term and medium-term anomalies distributed mainly in the range 300 ~ 500 km away from the epicenter. By contrast,the short term,imminent and macroscopic anomalies clustered in an epicentral distance less than 100 km. The underground fluid anomalies in the higher station density area reflect the enhancement of fluid movement,which are conducive to determine the seismic risk area and trace the short-term precursor of earthquake. The regional stress variations may cause the fractures in a fault zone open and close,leading to the change of water level and temperature in boreholes or spring and emission of deep-sourced gases. It may also lead to intense water-rock reaction and groundwater intrusion,resulting in the change of ion contents in groundwater,or sometimes,the occurrence of significant macroscopic anomalies. Therefore,it is highly possible to obtain reliable earthquake precursor information for predicting the forthcoming earthquake risk zone in the region with dense observation stations.更多还原