针对2012年5月28日唐山M_L5.2地震发生在老震区5级地震平静17年的背景，且其震级与唐山大地震序列强度衰减趋势相比明显偏高这一现象，采用双差层析成像方法，以2年为时间间隔对唐山地区2010年5月～2016年5月的地震数据进行反演，获得该区2012年唐山M_L5.2地震前后地壳的三维地震P波和S波速度的空间分布，结合此次地震的精定位震源参数，对比分析地震前后震源区地下介质波速的变化特征。研究结果发现此次地震发生前，震中处在高低速过渡带的位置，震后震中附近的波速出现一定程度的降低。

The Tangshan M_L5.2 earthquake in 2012 occurred against the background that earthquake with M ≥ 5.0 in the old earthquake zone was calm for 17 years,and its magnitude was significantly higher than that of the Tangshan earthquake sequence. In this paper,the TomoDD method was used to invert the seismic data from May 2010 to May 2016 in the Tangshan area at two-year intervals,and obtain the three-dimensional seismic P and S waves of the crust before and after the 2012 Tangshan M_L5.2 earthquake. Combining the precise positioning of the source parameters of the earthquake,this paper compared and analyzed the variation characteristics of the velocity of the subsurface medium in the source region before and after the earthquake. The study found that the epicenter was in the high-low-speed transition zone before the earthquake,the wave velocity near the epicenter after the earthquake has decreased to some extent.

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中国地震局地震科技星火计划（XH18008Y）、中国地震局震情跟踪课题（2019010105）、河北省地震局星火项目（DZ20180319008、DZ20170509039）共同资助