北京一次小震级地震前异常声-重力波产生机理的研究

观测到北京一次小震级地震(ML=3.0)前的异常声-重力波,并同时记录到异常地表倾斜信号。二者相关系数比较高,在接近震中的地区相关系数达到最大值0.5,相关系数随着远离震中的距离增大而减小。经过研究表明,异常声-重力波的产生与震前的地表缓慢活动引发的山体缓慢晃动导致的气流风速波动变化有关。基于350 m高的气象铁塔观测的风速数据,对两层大气模型传播的声-重力波进行了数值计算,得到的相对山体非平稳气流引起的声-重力波与观测信号在特征周期、幅度和速度三个参数上近似。以地表倾斜为例的模型与观测数据的一致性表明该震前声-重力波与地震存在关联性。 

Study on generation mechanism of anomalous acoustic-gravity waves before the 2011 Beijing earthquake(ML=3.0)

Observation results of abnormal acoustic-gravity waves before a Beijing earthquake(ML = 3.0) are presented.During this period,abnormalities of earth surface tilt variations were also recorded.The cross-correlations between the both values are high,which reach maximal values of 0.5 in the area close to the epicenter.The correlations decrease with increasing distances from the epicenter.It was proposed that generation of the anomalous waves may be associated with the pressure and wind perturbations in the air flow caused by slowly shaking mountains during slow suface motion preceding the earthquake in Beijing.Based on the wind velocity data taken from a 350 m meteorological tower in Beijing,the propagation of ducted acoustic-gravity waves in a two-layer model of the atmosphere was numerically simulated.It is shown that characteristic periods,amplitudes and velocities of the simulated phases which were assumed from non-stationary air flow relative to mountains are approximate to the observed phases.A consistency between the simulated results and observation data indicates that a slow surface motion may be a possible source of the anomalous acoustic-gravity waves observed prior to the earthquake.