采用双差定位法对2013年7月22日甘肃岷县-漳县交界地区M6.6地震及主震后48小时内388次余震序列进行重新定位，得到350个精定位地震数据。结果表明，余震优势展布以北东向较大倾角的铲状结构为特征，长约12 km，以主震为中心两侧对称分布；震源深度主要集中在4-10 km范围内，但余震震级由10 km左右深度的3-4级向3 km深度之上近地表的2-3级迁移变化；余震分布清晰呈现双层结构，较深层分布在4-10 km深度，而较浅层分布3 km深度之上，2层之间地震分布较少。分析认为，浅层地震可能为本次地震地表破坏较强原因之一。震源深度剖面显示，破裂面向NE倾斜，推测此次地震的发震断裂为临潭-宕昌断裂。
Applying the double-difference algorithm to the Minxian-Zhangxian, mainshock (M6.6) and its 388 aftershocks after 48 hours, Gansu on July 22 2013, we obtained 350 relocated earthquakes. Our results show that the aftershocks are shown as a shovel-shaped structure with a large northeastward dip extending for over 12 km long along the north-west direction and have an approximately symmetrical distribution about a center of the mainshock. The aftershocks are focused at depths of 4-10 km, but they migrate from about 10 km depth to above 3 km depth and their magnitudes range from 3-4 in a deeper layer to 2-3 in a shallower layer. The aftershocks show clearly a double-layer structure, one of which is at 4-10 km depth, while the other is above 3 km depth. There are few events between these two layers. The shallow earthquake layer could be one of causes that made a strong damage in the event. The vertical cross section of aftershock hypocenters shows a northeast tilt of the fault plane, suggesting that the seismogenic fault of this mainshock could be the Lintan-Diachang fault.
2017,38(2): 12-16 收稿日期：2016-04-27
DOI：10.3969/j.issn.1003-3246.2017.02.003
基金项目：中国地震局地震科技星火计划（项目编号：XH17049Y）
作者简介：梁姗姗(1989-),女,工程师,主要从事小地震定位和震源机制反演工作。E-mail:liangshanshan@seis.ac.cn
参考文献：
邓起东,张培震,冉勇康,等.中国活动构造基本特征[J].中国科学(D辑),2002,32(12):1020-1030.
房立华,吴建平,王未来,等.四川芦山MS7.0地震及其余震序列重定位[J].科学通报,2013,58(20):1901-1909.
何文贵,周志宇,马尔曼,等.岷县-卓尼5.0级地震的基本特征和地质背景研究[J].地震研究,2006,4(26):372-378.
李少华,王彦宾,梁子斌,等.甘肃东南部地壳速度结构的区域地震波形反演[J].地球物理学报,2012,55(4):1186-1197.
王健,李春峰,雷建设,等.华北地区地震活动与地壳热结构关系研究[J].地震学报,2016,38(4):618-631.
王卫民,郝金来,姚振兴.2013年4月20日四川芦山地震震源破裂过程反演初步结果[J].地球物理学报,2013,56(4):1412-1417.
王周元,范世宏,姬凤英,等.甘肃地区地壳速度的非均匀分布[J].西北地震学报,1996,18(2):18-25.
徐云马.兰天武地区(2000-2006年)重力场时变分析[D].中国科学技术大学,硕士论文,2008.
杨中书,曾文敬.利用双差法对2005年江西九江-瑞昌5.7级地震序列重新定位[J].地震地磁观测与研究,2007,28(2):25-31.
张广伟,雷建设,谢富仁,等.华北地区小震精定位及构造意义[J].地震学报,2011,33(6):699-714.
张广伟,雷建设.四川芦山7.0级强震及其余震序列重定位[J].地球物理学报,2013,56(5):1764-1771.
张勇,许力生,陈运泰.芦山4.20地震破裂过程及其致灾特征初步分析[J].地球物理学报,2013,56(4):1408-1411.
郑文俊,雷中生,袁道阳,等.1573年甘肃岷县地震史料考证与发震构造探讨[J].中国地震,2007,23(1):75-83.
郑文俊,雷中生,袁道阳,等.1837年甘肃岷县北6级地震考证与发震构造分析[J].地震,2007,27(1):120-130.
郑文俊,刘小凤,赵广堃,等.2003年11月13日甘肃岷县MS5.2地震基本特征[J]. 西北地震学报,2005,27(1):61-65.
Evans J, Eberhart D, Thurber C. User's manual for SIMULP12 for imaging VP and VP/VS:a derivative of the "Thurber" tomographyic inversion SIMUL3 for local earthquakes and explosions[R]. US Geological survey, Open File Report, 1994:94-431.
Lei J S, Zhang G W, Xie F R, et al. Relocation of the 10 March 2011 Yingjiang, China, earthquake sequence and its tectonic implications[J]. Earthquake Science, 2012, 25:103-110.
Waldhauser F, Ellsworth W. A double-difference earthquake location algorithm:method and application to the Northern Hayward Fault, California[J]. Bull Seismol Soc Am, 2000, 90(6):1353-1368.
Wang C S, Gao R, Yin A, et al. A mid-crustal strain-transfer model for continental deformation:A new perspective from high-resolution deep seismic-reflection profiling across NE Tibet[J]. Earth Planet Sci Lett 306:279-288.
