大姚地热动态特征分析

Analysis on Geothermal Behavior in Dayao

通过大姚高精度水温观测井水文地质、井孔条件的分析 ,震例观测资料、实验观测数据的处理 ,以及井水水质分析结果 ,表明大姚水温周期性变化的突出位置是井深 75m左右 ,根本原因是该地层石膏脉稳定释热 ,含水层热水与井内冷水混合过程中 ,在通道内形成钙盐类沉淀物 (如CaSO4 CaCO3 ) ,堵塞对流通道 ,含水层内外压差突破被阻塞通道 ,热水反复侵入井内 ,便形成水温周期性变化。地震的孕育、发生和调整过程 ,由于应力场作用 ,产生附加地热场 ,水温基值发生变化 ,周期畸变或消失 ,这种附加地热动态是可以恢复的。

Through analyzing of the hydrogeology and well conditions for the high-precision observation well of water temperature,processing of the observation data of earthquake examples and experimental data and analyzing of water quality in the well in Dayao,it is show that notable position of periodic variation in the water temperature in Dayao is located in the depth of about 75m of the well.The basic reason is that in the course of stable thermal release of gypsum vein in the stratum and mixing of the hot water in the aquifer and the cold water in the well,calcium salt precipitates such as CaSO 4 and CaCO 3 are formed in the passbands and stop up convective passbands.Blocked passbands are broken through because of pressure difference between internal and external aquifers and hot water repeatedly enters into the well,forming periodic variation in water temparature.In the course of preparation,occurrence and regulation of earthquake,additional geothermal field and variation in basic value of water temperature will take place due to action of stress field.Periodic distortion might disappear and the additional thermal behavior can be restored,and therefore the geothermal behavior in Dayao reflects the thermal information in specical stratum in the well region.