2012年5月28日河北省唐山市古冶区与滦县交界发生4.8级地震,地震宏观震中位于古冶区的王辇庄乡。震中烈度为Ⅴ度,地震发生在NE走向的唐山断裂带附近。地震没有造成人员伤亡和经济损失。震源机制解P轴方位为SEE,T轴方位为SSW,接近水平,这与华北构造应力场的NE-NEE方向不一致。唐山4.8级地震是1976年唐山7.8级地震晚期余震的正常起伏,2004年以来唐山老震区的ML4.0以上地震呈现了很好的准周期性。唐山4.8级地震前地震活动性和测震学参数存在背景性异常,从不同角度反映了老震区地震活动平静、起伏的阶段性特征。前兆异常以中短期异常为主,其中地下流体异常、电磁异常表现更为突出。此次地震虽然震级不高,但无论是地震活动性还是前兆方面都出现了一定数量的异常。异常既有趋势性的,也有短临的,配套性很好。

An M4. 8 earthquake occurred in the joint area of Guye and Luanxian of Tangshan city on May 28，2012． The macroscopic epicenter was located in Wangnianzhuang in Guye region． The Intensity of epicenter was Ⅴ degree． The earthquake occurred in the middle of Tangshan Fault in the northeast direction． The earthquake caused no human casualties and economic losses． In the focal mechanism solution，the azimuth of P axis was SEE and T axis was SSW near horizontal． It was not uniform with the tectonic stress field in North China，which is in NE-NEE direction． The M4. 8 earthquake was undulation of the aftershocks of Tangshan M7. 8 earthquake occurred in 1976． The over ML4. 0 earthquakes in Tangshan area showed a quasi-periodic characteristic． There were some background anomalies both in seismicity and seismometry before the event，and they reflected the quiet and undulant process of the seismic activity in the old earthquake region from different views． The precursory anomalies were mainly middle and short term ones，in which groundwater and electromagnetic anomalies were obvious． The magnitude of the earthquake was not high，but it showed many anomalies，both in seismicity or precursor． The anomalies matched very well，in which there were both tendency and current ones．

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