利用纵、 横波的拐角频率比值和位移谱零频极限比值计算波速比以芦山MS7.0地震序列为例

摘要/Abstract

摘要： 使用区域固定台网数字地震记录资料, 计算2013年4月20日四川芦山MS 7.0地震余震序列的震源谱参数, 通过纵、横波的拐角频率比值和纵、横波位移谱零频极限比值计算波速比。结果显示: ① 拐角频率比值得到的波速比平均值约为1.27, 零频极限比值得到的波速比平均值约为1.67, 零频极限比值得到的结果更接近泊松介质的波速比1.73; ② 两种方法得到的波速比变化趋势基本一致: 在主震后均处于较低异常水平, 最后一个M_S5.4余震后, 波速比回返升高; ③ 零频极限比值得到的波速比异常形态较明显, 在3个M_S5.4余震前都呈现出“降低-回返”的过程, 在回返之后发生最大余震; ④ 在数据处理过程中, 是否对介质做非弹性衰减校正对两种方法的结果影响不大; ⑤ 单台波速比与多台波速比的变化趋势基本一致。

关键词: 纵、横波拐角频率比, 纵、横波位移谱零频极限比, 波速比, 芦山地震

Abstract: Based on seismic waveform data recorded by National Digital Seismic Network from April 20,2013 to December 2013, we calculated the source spectrum parameters of earthquakes with M_L≥3.0 of the Lushan earthquake sequence, using the ratio of P-wave to S-wave corner frequency and the ratio of P-wave to S-wave long-period spectral level to calculate the velocity ratio. The results indicate that: ① The average V_P/V_S obtained from the ratio of corner frequency is 1.27 while the average V_P/V_S obtained from the ratio of long-period spectral level is 1.67, which is closer to the value 1.73 of Poisson medium. ② Velocity ratios obtained from the two methods have a common variation tendency: after the mainshock the velocity ratio was at a low value anomalies until the last M_S5.4 aftershock , since then the velocity ratio recovered to the level above the average. ③ The velocity ratio anomaly calculated from the long-period spectral level behaved more evidently, it presents a ‘decline-recovery-occurrence’ process before the three M_S5.4 aftershocks. ④ Correction for medium attenuation has no big effect on the results getting from the two methods. ⑤ The velocity ratios obtained from single seismic station and multi-station have the same variation tendency.

Key words: Velocity ratio V_P/V_S, Source spectrum parameters, The 2013 Lushan earthquake sequence

中图分类号:

P315.7

陈丽娟, 陈学忠, 李艳娥, 王生文, 郭祥云. 利用纵、横波的拐角频率比值和位移谱零频极限比值计算波速比以芦山M_S7.0地震序列为例[J]. 地震, 2015, 35(2): 11-25.

CHEN Li-juan, CHEN Xue-zhong, LI Yan-e, WANG Sheng-wen, GUO Xiang-yun. Calculating Wave Velocity Ratio V_P/V_S of the 2013 Lushan Earthquake Sequence from Source Spectrum Parameters[J]. EARTHQUAKE, 2015, 35(2): 11-25.

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