2016年8月21日17时15分，河北省唐山市开平区（39.70°N，118.35°E）发生ML 3.5地震，震源深度6 km。据河北省快报目录，8月21日至10月24日共发生可定位小震694次，最大地震为9月10日ML 4.7地震。计算本次震群序列参数，分析其物理特性。精定位结果显示，ML 4.7震群集中在唐山-古冶断裂，属唐山老震区余震活动。与该区同等震级地震相比，震群中几次3级以上地震视应力水平较低，震源机制一致性较好，表明该区存在较为一致的稳定应力场。震群活动显示，该震群为非典型前兆性震群。分析结果对正确了解此次震群特征及判断序列发展趋势具有较高的帮助作用。
At 17:15 on August 21th, 2016, an ML 3.5 magnitude earthquake occurred in Kaiping District, Tangshan City, Hebei Province (39.70°N, 118.35°E) with a focal depth of 6 km. According to the Hebei Express List, from August 21 to October 24, there were 694 small earthquakes that could be located. In this article, the parameters of the earthquake swarm sequence are calculated and its physical characteristics are analyzed. The fine location results show that the ML 4.7 earthquake cluster in the Tangshan-Guye fault and it still belongs to the aftershocks of the Tangshan old earthquake area. The magnitude of the apparent stress of earthquakes above magnitude 3 in the earthquake swarm is lower than that of earthquakes of the same magnitude in the area, and the consistency of the focal mechanism is good, indicating that there is a consistent and stable stress field in this area. The swarming activity shows that the swarm is an atypical precursory swarm. Analysis results is helpful for correctly understanding the characteristics of the earthquake swarm and correctly judging earthquake tendency.
2018,39(6): 37-44 收稿日期：2018-05-02
DOI：10.3969/j.issn.1003-3246.2018.06.006
基金项目：地震科技星火计划（项目编号：XH17007）；河北省地震局星火项目（项目编号：DZ20170509039，DZ20170109002，DZ20180319008）
作者简介：郭蕾(1989-),女,硕士,主要从事数字地震学相关研究工作。E-mail:guolei0430@126.com
参考文献：
曹凤娟,尹涛,马丽,等. 岫岩MS 5.4地震前后视应力时空变化特征[J]. 东北地震研究,2005,21(1):14-19.
陈学忠,李艳娥. 2006年7月4日河北文安MS 5.1地震前震中周围地区小震视应力随时间的变化[J]. 中国地震,2007,23(4):327-336.
陈颙. 用震源机制一致性作为描述地震活动性的新参数[J]. 地球物理学报,1978,21(2):142-159.
国家地震局预测预防司. 测震学分析预报方法[M]. 北京:地震出版社,1997:108-115.
黄德瑜,冯浩. 强震前大范围地震活动性参数的时空扫描[J]. 地震学报,1981,3(3):283-291.
李芳,李宇彤,刘友富. 视应力方法在震群性质判定中的应用研究[J]. 地震,2006,26(4):45-51.
林邦慧,李大鹏,刘杰,等. 前震和前震序列的研究[J]. 地震学报,1994,16(Z1):24-38.
刘正荣,钱兆霞,王维清,等. 前震的一个标志——地震频度的衰减[J]. 地震研究,1979,2(4):1-9.
陆远忠,陈章立,王碧泉,等. 地震预报的地震学方法[M]. 北京:地震出版社,1985:175-196.
马鸿庆. 华北地区几次大震前的b值异常变化[J]. 地球物理学报,1978,21(2):126-141.
冉志杰,杨歧焱,周月玲,等. 唐山丰南M 4.1级地震强震记录分析[J]. 震灾防御技术,2012,7(4):367-376.
宋俊高,王炜. 震群活动和地震预报综述[J]. 国际地震动态,1998,(9):6-11.
王炜,杨德志. 利用Weibull分布研究华北地区前兆震群的特征[J]. 中国地震,1987,3(4):13-21.
朱传镇,傅昌洪,罗胜利. 震群与大地震关系的研究(华北地区)[J]. 地震学报,1981,3(2):105-117.
朱传镇,王琳瑛. 震群信息熵异常与地震预报[M]//国家地震局科技监测司. 地震预报方法实用化研究文集:地震学专辑. 北京:学术书刊出版社,1989:229-242.
Evison F F. The precursory earthquake swarm[J]. Phys Earth Planet Interiors, 1977, 15:19-23.
Gutenberg B, Richter C F. Seismicity of the earth and associated phenomena[M]. Princeton:Princeton University Press, 1954:16-21.
Kanamori H. Relation between tectonic stress, great earthquakes and earthquake swarms[J]. Tectonophysics, 1972, 14:1-12.
Yang X, Long H Y, Shangguan W M, et al. Research on the application of time structure variation analysis to the Jiashi-Bachu earthquake swarm sequence[J]. Earthquake Research in China, 2008, 22(3):251-264.
Zhao L S, Helmberger D V. Source estimation from broadband regional seismograms[J]. Bull Seismol Soc Am, 1994, 84(1):91-104.
Zhu L P, Helmberger D V. Advancement in source estimation techniques using broadband regional seismograms[J]. Bull Seismol Soc Am, 1996, 86(5):1 634-1 641.
