唐山台跨断层基线破年变和趋势转折异常的数值模拟分析

唐山地震台多条短基线测线自2012年以来出现的破年变和趋势转折异常现象得不到合理解释。经核实,潜在干扰因素为观测场地附近的大型建筑施工。为定量分析建筑施工对趋势转折现象和年变消失现象的影响,本文基于多年跨断层数据,利用二维线弹性模型有限元方法,对断层运动进行模拟分析。结果显示:场地附近的大型建筑施工会造成断层水平张性运动趋势的转缓,且在时间上与观测异常现象匹配,但不会导致由张性转为压性的运动;同时,建筑施工会造成跨断层基线年变振幅减小,但不会引起年变消失。唐山台基线的短期快速变化和年变消失的异常变化具有较高的可信度,与区域构造运动和应力场改变有关。

Numerical Simulation of the Cross-fault Baseline Anomalies of Trend Break and Annual Cycle Disappearance at the Tangshan Station

There is no reasonable explanation for the abnormal phenomenon of the annual cycle disappearance and change of trend of the short baseline since 2012 at the Tangshan station. The potential interference factors are verified to be the construction of large buildings near the observation site. To analysis quantitatively the influence of building construction on the phenomena, this paper is based on many years of cross-fault data and uses a finite element method of 2-d linear elastic model to simulate the fault movement. The results show that nearby large building construction do cause a decrease in the tendency of the fault tensional movement and the starting point matches the observation in time. But it can't cause reverse to be compression. At same time, it can decrease the annual amplitude of fault-cross short baseline but can't lead the year cycle to disappear. So it can be considered that these abnormal phenomena have higher reliability and are related to the regional tectonic movement and stress field change. That means the tectonic compressive movement may have be strengthened by 2012 in north China.