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2013年10月31日11时03分,在吉林省松原市前郭尔罗斯蒙古族自治县发生M_S5.5级地震,11时10分,震区再发生Ms5.0级地震.截止2013年11月23日,吉林前郭-乾安地区(本文统称为前郭-乾安震源区)已经发生Ms5.0级以上地震5次.虽然震源区外围中强地震活跃,但在前郭-乾安震源区内,据历史地震资料记载,仅2006年3月31日在距离本次地震序列以西8 km处发生过一次乾安、前郭交界Ms5.1级地震.除此之外,距离震源区90 km处,曾于公元1119年2月发生过M6.7级地震.为了更好地认识区域孕震环境,本文利用吉林、辽宁、内蒙古以及黑龙江数字地震台网的三分向宽频带波形资料,建立了适用于这些台站的分区速度结构模型,反演了2013年10月31日-11月23日前郭-乾安震源区M_L≥4.5级中强地震的矩张量解.结果显示,几次中强地震均呈现逆断层兼少量走滑性质,其中NW走向的节面Ⅰ为此次中强地震序列的断层面,发震断层的优势走向集中在320°左右,优势倾角分布在38°~65°.根据矩张量反演结果,结合地震序列重新定位(郑钰,待发表)后的空间分布情况,我们推测此次地震序列的发震构造可能是震源区基底深部一条NW向隐伏逆冲断层,这条断层延伸至地表的位置可能位于震源区北侧靠近124°经度隆起带附近.此外,震源区的发震构造和浅部应力场可能是在西太平洋板块俯冲产生的挤压应力场背景下,受控于郯庐断裂带右行走滑的次级应力场.
At 11:03 on October 31, 2013, an M5.5 M5.5 earthquake occurred in the former Guoer Rose Mongolian Autonomous County, Songyuan City, Jilin Province. At 1110, another Ms5.0 earthquake hit the quake zone. As of November 2013 On the 23rd, an earthquake of magnitude Ms5.0 or above occurred in the Qianqiang-Qian’an region of Jilin Province (referred to in this paper as Qian Guo-Qian’an seismic source area). Although moderately strong earthquakes were active in the periphery of the seismic source area, According to historical seismological data, only a dry-an-qian earthquake occurred at 8 km to the west of this earthquake sequence and the Ms5.1 earthquake at the Qian-Guo junction was recorded on March 31, 2006. In addition, km, a magnitude M6.7 earthquake occurred in February 1119 AD In order to better understand the geomagnetic environment in the region, this paper uses the tristimulus broadband waveform data of Jilin, Liaoning, Inner Mongolia and Heilongjiang Digital Seismic Networks, The model of zonal velocity structure applied to these stations was established and the moment tensor solutions of M_L≥4.5 moderate-strong earthquakes in Guo-Gan’an seismic source area were retrieved from October 31 to November 23, 2013. The results show that a few Both moderate and strong earthquakes show reverse faults and a small amount of strike-slip properties, of which the NW-facing nodal plane Ⅰ is the fault of this moderate-strong earthquake sequence , The dominant trend of the seismogenic faults concentrates at about 320 ° and the dominant dip angle ranges from 38 ° to 65 ° .According to the moment tensor inversion results and the spatial distribution after the earthquake sequence is relocated (Zheng Yu, to be published), we It is speculated that the seismogenic structure of this earthquake sequence may be an NW strike-buried fault in the deep basement of the source region, and the fault may extend to the surface near the 124 ° longitude uplift zone on the north side of the source region. Seismogenic structures and shallow stress fields may be controlled by the secondary stress field on the right-lateral strike of the Tan-Lu fault zone under the compressive stress field induced by the subduction of the western Pacific plate.