SEISMOLOGY AND GEOLOGY ›› 2015, Vol. 37 ›› Issue (4): 1004-1019.DOI: 10.3969/j.issn.0253-4967.2015.04.006

• Special topic on earthquake prediction method • Previous Articles     Next Articles

comprehensive study on the changing process of focal mechanisms of the 2014 huoshan ms4.3 earthquake sequence

NI Hong-yu1,2, LIU Ze-min1, HONG De-quan1,2, WANG Xiao-li1, ZHAO Peng1   

  1. 1. Anhui Earthquake Administration, Hefei 230031, China;
    2. Mengcheng National Geophysical Observatory, Mengcheng 233500, China
  • Received:2015-10-23 Online:2015-12-20 Published:2016-01-28

综合研究2014年霍山MS4.3地震序列的震源机制变化过程

倪红玉1,2, 刘泽民1, 洪德全1,2, 汪小厉1, 赵朋1   

  1. 1. 安徽省地震局, 合肥 230031;
    2. 蒙城地球物理国家野外科学观测研究站, 蒙城 233500
  • 通讯作者: 刘泽民
  • 作者简介:倪红玉, 女, 1982年生, 2008年于中国科学技术大学获物理化学专业硕士学位, 工程师, 主要从事震源机制和构造应力场等数字地震学研究, 电话: 0551-62528690, E-mail: hyni@mail.ustc.edu.cn。
  • 基金资助:

    中国地震局震情跟踪定向工作任务(2014020113)和中国地震局地震科技星火计划项目(XH14026)共同资助。

Abstract:

In this paper, the focal mechanisms of Huoshan MS4.3 earthquake sequence since October 2013 are calculated with the method developed recently by Snoke, which combines the use of first motion of P, SV and SH waves and their amplitude ratios(referred to as Snoke method). We estimate the difference(also referred to consistency parameter θ)between the stress axis direction of focal mechanism solution and the mean stress tensor on one hand, and get the relative changes of focal mechanisms rather than the focal mechanisms themselves on the other hand, by using methods of correlation coefficient of body-wave spectral amplitudes, first motions and amplitude ratios of vertical P wave of single station, as limited by the network layout and density of observation points, focal mechanism solutions of small earthquakes are not easy to obtain. We studied the changing process of focal mechanisms of Huoshan MS4.3 earthquake sequence since October 2013 with many methods such as consistency parameter, correlation coefficient of body-wave spectral amplitudes, first motion and amplitude ratio of vertical P wave of single station, to determine the type of the sequence. The result shows that: before Huoshan MS4.3 earthquake of April 20, 2014, the consistency parameter of the earthquake sequence was lower than the mean for a long period, correlation coefficient of body-wave spectral amplitudes was always at high values(about 0.9), odds ratio of first motions of vertical P wave of single station near the epicenter, defined as the ratio of predominant number to contrast number of first motions, was up to 13.8 at station SJH, 3.8 at BZY and 3.6 at LNA, respectively; first motions of vertical P wave of single station showed an obvious predominant distribution as a whole, and the amplitude ratios of vertical P were consistent, which suggests that before Huoshan MS4.3 earthquake, focal mechanisms were consistent, so the earthquake sequence before Huoshan MS4.3 earthquake is the foreshock sequence. After Huoshan MS4.3 earthquake, correlation coefficient of body-wave spectral amplitudes was lower(about 0.6), first motions and amplitude ratios of vertical P wave of single station were in disorder, which suggest that the focal mechanisms are inconsistent after the Huoshan MS4.3 earthquake, so the earthquake sequence after Huoshan MS4.3 earthquake is the aftershock sequence, and subsequent larger earthquakes are not likely to occur. The focal mechanisms in Huoshan region during the period of Huoshan MS4.3 earthquake experienced a process from scattering to convergency and to scattering again.

Key words: consistency of focal mechanisms, parameter correlation coefficient of body-wave spectral amplitudes, initial motion, amplitude ratio, Huoshan MS4.3 earthquake

摘要:

综合利用震源一致性参数、体波谱振幅相关系数、单台的P波初动和振幅比方法研究2013年10月以来霍山MS4.3地震序列震源机制的变化过程, 进而科学判定该序列的类型, 探索震后地震趋势的判别方法。结果表明, 2014年4月20日霍山MS4.3地震前, 霍山地震序列的震源一致性参数低于多年均值, 体波谱振幅相关系数在0.9附近波动、持续处于高值状态, 单台的P波初动总体优势分布明显、振幅比较为一致, 均显示霍山MS4.3地震前序列的震源机制较为一致, 为前震序列; 霍山MS4.3地震后, 序列的体波谱振幅相关系数较低, 在0.6附近波动, 单台的P波初动、振幅比较为紊乱, 表明霍山MS4.3地震后序列的震源机制较为紊乱, 为余震序列, 后续发生更大地震的可能性不大。因此, 霍山MS4.3地震前后震源区的震源机制经历了散乱—一致—散乱的过程。

关键词: 震源一致性参数, 体波谱振幅相关系数, 初动, 振幅比, 霍山MS4.3地震

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