蓟县台小辛庄山洞周边短时地下水抽取对应变变化的影响

Study on strain change affected by short pumping around the Xiaoxinzhuang cave at the Jixian seismic station

摘要:

蓟县小辛庄伸缩应变受地下水抽取影响显著，在季节性抽水时段桑梓水位和伸缩应变二者表现出了很好的同步性变化。本文统计了2004～2013年年初季节性抽水时段水位变化量与伸缩两方向应变变化量，利用最小二乘法建立水位变化量与伸缩NS、EW向应变变化量的线性回归模型，模型分别满足：α＝0.05和α＝0.1的t检验，模型置信水平分别为95%和90%。利用该线性回归模型，计算2014年桑梓水位变化量所对应的应变变化量的估计值及变化区间，并与实测结果对比，发现应变实际观测变化量在该区间内，进而判定伸缩应变两方向2014年3月中旬以来出现的加速拉张变化，与季节性抽水有关，作为地震前兆异常的信度不高。结果表明，桑梓水位可以用于研究小辛庄伸缩应变受周边季节性抽水短时干扰的变化幅度，有利于辅助判定在季节性抽水时段伸缩应变出现短期加速拉张变化的异常信度。

Abstract:

Extensometer at Xiaoxinzhuang cave is disturbed seriously by pumping. Strain data and ground water-level at Sangzi show synchronous change in the pumping season. In this paper，the variations of water-level and strain at the two directions are calculated from 2004 to 2013. Regression models between water-level and strain variations at the two directions are built using the linear least square method. One model meets the t test with α＝0.05 and the other is α＝0.01. Therefore，the confidence level values are 95% and 90%. Corresponding estimator and prediction interval of stain at the two directions are calculated according to water-level variations in 2014 using the model. On account of that stain measured value is in the prediction interval，the accelerated change of stain at the two directions from mid-March,2014 is correlated with pumping with lower confidence as seismic precursor anomaly. The result indicates that it is possible to calculate the stain variations of Xiaoxinzhuang for pumping using water-level data of Sangzi and helpful to determine the anomaly confidence of stain accelerated change at pumping time.