芦山地震序列中地震预警震级估计参数随时间与震级的变化

Magnitude estimation parameters for earthquake early warning of Lushan earthquake sequence changed in lapse-time and magnitude

以探究地震波初期信息能否反映地震的最终震级为目标,选取芦山地震序列中主震与3次余震强震动记录,分别计算P波触发后3 s、4 s、5 s、10 s、20 s和30 s六个时间窗内的加速度幅值P_a、速度幅值P_v、位移幅值P_d和特征周期值τ_c,分析这4种地震预警震级估计参数随时间以及震级的变化趋势。结果表明,在芦山地震主震震源破裂过程的初期,都可以利用这4种震级估计参数快速判断出这是一次大震级事件。幅值参数随时间窗的增长而增大、直到震源破裂结束而不再发生变化,这表明幅值参数的变化趋势与震源破裂过程相关、特别是位移幅值P_d参数,同时,利用幅值参数可以明显的区分主余震的震级大小。特征周期τ_c参数不随时间窗的增长而增大,芦山地震主余震的特征周期参数变化差异也不明显。

To explore whether the initial seismic wave can reflect the final magnitude of the earthquake, we select the records of the mainshock and 3 aftershocks in Lushan earthquake sequence. After calculating the valuesof acceleration amplitude Pa, velocity amplitude Pv, displacement amplitude Pd and characteristic τc period in time window of 3 s, 4 s, 5 s, 10 s, 20 s and 30 s after P-wave onset respectively, the trend of these 4 kinds of earthquake early warning magnitude estimation parameters with time and magnitude is analyzed. The result shows that in the early stage of the source rupture process of Lushan earthquake, we can find it quickly to identify a large earthquakeby using these 4 parameters.The amplitude parameters increase with the extension of the time window, does not change until the end of the source rupture process.This shows that the variation trend of the amplitude parameters is related to the rupture process of the source, especially the displacement amplitude Pd. Meanwhile, the magnitude of the main shock aftershocks can be distinguished distinctly by the amplitude parameters. The characteristic period τc does not increase with the extension of the time window, and the variation of this parameter in the main shock and aftershocks in Lushan earthquake is not obvious.