Abstract: The study is based on the underground fluid observation data in Lijiang area, northwest Yunnan Province. The data include the water level and temperature in Dangxiao well and Jinjia well, and the ion measurements in Ganze spring. Combining with the data of regional hydrogeology, rainfall, well structures, and the geothermal gradient, we analyzed the variations of each measurement item before the Ludian M_S6.5 earthquake on August 3, 2014 and discussed the possible mechanism for the abnormal variations. The water levels of both Dangxiao well and Jinjia well are influenced by local rainfall, but the former shows hysteresis according to rainy seasons and is the long trend influence; while the latter shows synchronization between high water level and rainy season, indicating good connection between well water and shallow aquifer. The recharge water for Dangxiao well is in relatively low temperature, and the temperature sensor is located at the major connecting section between the well water and the aquifer; the water temperature variation is mainly affected by the discharge status and variation of water level. The Jinjia well is always in static level, and the temperature sensor is below the major connecting section between the well water and aquifer, so the water temperature is affected little by water level variations and in smooth fluctuation. The recharge source for Ganze spring can generally increase the contents of calcium and magnesium ions, so does the conductivity. The water level data of Dangxiao well since 2012 are decomposed with wavelet technique. The results, excluding such high-frequency components as the noise and the semidiurnal and daily wave components influenced by earth tide, are further processed with difference method in order to eliminate the trend effect. The results show that the relative change of water level is enhanced and in relatively rapid increase before the Ludian M_S6.5 earthquake; the corresponding water temperature values are high. The tendency of water level in Jinjia well displays descending, while the corresponding water temperature shows ascending. The content of calcium ion, magnesium ion, bicarbonate ion, and conductivity of Ganze spring are descending, while the content of fluoride ion is ascending. The abnormal variations of underground fluid in Lijiang area appeared in turns and were accompanied with minor earthquakes before Ludian M_S6.5 earthquake, which indicates enhancing of regional stress and increasing of fluid activity.

Key words: underground fluid, water level, water temperature, ion, Ludian earthquake, Lijiang

摘要： 基于云南西北部丽江地区党校井和金甲井的水位水温、甘泽泉的离子含量等地下流体观测数据，结合区域水文地质、降雨、井孔结构、水温梯度等资料，分析了各测项基本动态特征和在鲁甸M_S6.5地震前的异常变化。党校井和金甲井水位的动态特征都受当地降雨的影响，但是前者在时间上有滞后性，是趋势性的；后者水位高值与雨季同步，显示与浅层水沟通良好。党校井补给区水源温度较低，温度探头位于井孔与含水层沟通的主要段，水温动态主要受井水位泄流状态和水位变化的影响。金甲井水位处于静水位状态，温度探头位于井孔与含水层沟通主要段的下部，受水位变化影响小，水温波动平稳。甘泽泉的补给区水源正常情况下使钙离子、镁离子含量浓度升高，电导率增高。对2012年以来一直处于静水位状态下的党校井水位资料采用小波信号分解技术进行处理，去除干扰、固体潮半日波、日波等高频信息后，对保留的动态曲线做差分处理消除趋势影响，发现在鲁甸M_S6.5地震前水位呈现出较大的相对变化，快速上升，对应深部水温处于高值。金甲井水位趋势动态表现为下降，水温上升。甘泽泉的钙离子、镁离子、碳酸氢根离子、电导率测值下降，氟离子含量上升。鲁甸地震前，丽江地区地下流体观测值的异常变化在时间上依次出现并伴随中小震活跃，反映了区域应力状态的增强和流体活动的加剧。

关键词: 地下流体, 水位, 水温, 离子, 鲁甸地震, 丽江