地震静应力作用与井水位孔压响应分析——以唐山古冶5.1级地震为例

Analysis of Seismic Static Stress and Response of Well Water Level and Pore Pressure:A Case Study of Tangshan Guye M_(S)5.1 Earthquake

计算古冶5.1级地震震前、同震、震后唐山地区9口流体井的孔压分布和实测井水位升降情况。结果表明:(1)震前,唐山古冶地区处于应力累积的状态,压缩区为近东西向,拉张区为近南北向,实测的井水位升、降情况基本与压缩、拉张情况一致;(2)震时,压缩、拉张区没有改变,但应力有所释放,实测的井水升、降情况存在与压缩、拉张情况不一致的现象;(3)震后,压缩区演变为拉张区,拉张区演变为压缩区,实测的井水位升、降情况也基本与压缩、拉张情况一致。本文较为全面地解释了地震静应力从震前到震后的调整过程,通过计算震前、震时、震后的井孔压分布得知,井孔压在走滑断层破裂带周边呈四象限分布,这种变化特征可用震前闭锁剪力模型解释。

Based on the calculation of the pore pressure distribution and the measured water level fluctuation of nine fluid wells in Tangshan area before,during and after the Guye M_(S)5.1 earthquake.The results show that:(1)Before the earthquake,the Guye area of Tangshan was in the process of stress accumulation,the compression area was nearly in the east-west direction,and the tension area was nearly in the north-south direction.The measured well water level rise and fall were basically consistent with the compression and tension.(2)During the earthquake,the compression and tension areas do not change,but the stress is released.The measured well water rise and fall are inconsistent with the compression and tension.(3)After the earthquake,the compression area evolves into the tension area,and the tension area evolves into the compression area.This paper explains the adjustment process of seismic static stress from pre earthquake to post earthquake.By calculating the distribution of well bore pressure before,during and after the earthquake,we find that the distribution of well bore pressure is in four quadrants around the fracture zone of the strike slip fault,which can be explained by the locking shear model before the earthquake.