| 2014年新疆于田MS7.3地震序列重定位及其发震构造初步研究 |
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| 引用本文： | 唐明帅,王海涛,李艳永,热依木江,孔祥艳,魏芸芸,上官文明,魏斌.2014年新疆于田MS7.3地震序列重定位及其发震构造初步研究[J].地球物理学报,2016,59(6):2126-2137. |
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| 作者姓名： | 唐明帅 王海涛 李艳永 热依木江 孔祥艳 魏芸芸 上官文明 魏斌 |
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| 作者单位： | 新疆维吾尔自治区地震局, 乌鲁木齐 830011 |
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| 基金项目： | 中国地震局"测震台网青年骨干培养"专项(20160527),地震科技星火计划项目(XH15046),新疆维吾尔自治区科研机构创新发展专项资金(2013016),新疆地震科学基金项目(201405),国家自然科学基金(41274104,41474051,41174086)联合资助. |
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| 摘 要： | 2014年2月12日在新疆于田县发生了MS7.3地震,主震前一天在震区发生了MS5.4前震,震后余震活动频繁,由于震区台站十分稀疏和不均匀、地壳速度结构复杂,台网常规定位结果精度有限,很难从中获得序列的空间分布特征和活动趋势的正确认识.本文首先利用位于震区附近的于田地震台5年记录的远震波形数据,采用接收函数方法研究了震区附近的地壳结构,建立了震源区的地壳速度模型.在此基础上,联合震相到时和方位角对2014年于田MS7.3地震序列(从2014年02月11日-2014年04月30日,共计577次地震)进行了重新绝对定位.结果显示,(1) 重定位后的前震和主震震中位置明显向地表破裂带及其附近的阿尔金分支断裂(南肖尔库勒断裂和阿什库勒-肖尔库勒断裂)靠近,两者相距5.4 km,主震位置为36.076°N、82.576°E,震源深度为22 km, 前震位置为36.055°N、82.522°E,震源深度为19 km;(2) 本文重定位结果显示,余震序列沿NEE-SWW展布,优势分布长度约73 km、宽度约16 km,平均震源深度为14.8 km,其中77%的余震分布在地表破裂带的西南端,这部分余震中少数沿阿什库勒-肖尔库勒断裂分布,绝大多数沿北东东向的南肖尔库勒断裂分布,位于地表破裂带东北端的余震沿阿什库勒-肖尔库勒断裂分布,但发生在地表破裂带的余震极少;重定位后,位于地表破裂带西南侧的震中分布由台网目录的近南北向变为北东向,与地表破裂带、南肖尔库勒断裂和阿什库勒-肖尔库勒断裂走向一致;(3) 沿重定位剖面的地震分布,可推断位于地表破裂带西南段的南肖尔库勒断裂与位于北东段的阿什库勒-肖尔库勒断裂倾向反向,南肖尔库勒断裂的倾向为SE,阿什库勒-肖尔库勒断裂的倾向为NW,这与本次地震野外考察得到的断裂性质一致.综合重定位结果、地表破裂带分布、震源机制解、南肖尔库勒断裂和阿什库勒-肖尔库勒断裂的性质认为,2014年于田MS7.3地震的发震构造为阿尔金断裂西南尾段的两条分支断裂——南肖尔库勒断裂和阿什库勒-肖尔库勒断裂.
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| 关 键 词： | 2014年于田MS7.3地震序列 联合震相到时和方位角绝对定位法 重新定位 发震构造 |
| 收稿时间： | 2015-11-19 |
Relocation of the 2014 Yutian,Xinjiang, MS7.3 earthquake sequence and a preliminary study of its seismogenic structure |
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| TANG Ming-Shuai,WANG Hai-Tao,LI Yan-Yong,REYI-Mu-Jiang,KONG Xiang-Yan,WEI Yun-Yun,SHANGGUAN Wen-Ming,WEI Bin.Relocation of the 2014 Yutian,Xinjiang, MS7.3 earthquake sequence and a preliminary study of its seismogenic structure[J].Chinese Journal of Geophysics,2016,59(6):2126-2137. |
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| Authors: | TANG Ming-Shuai WANG Hai-Tao LI Yan-Yong REYI-Mu-Jiang KONG Xiang-Yan WEI Yun-Yun SHANGGUAN Wen-Ming WEI Bin |
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| Institution: | Earthquake Administration of Xinjiang Uygur Autonomous Region, Urumqi 830011, China |
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| Abstract: | On February 12, 2014, an MS7.3 earthquake occurred in Yutian County, Xinjiang, China. One day before this earthquake there was an MS5.4 foreshock occurred in the same place. After the mainshock, the seismicity of aftershocks was highly active. Study on the characteristics of this earthquake sequence may help us to strengthen our understanding of the seismogenic environment in this area. However, due to the sparse distribution of the seismic network and the complex crustal structure in the source region, it is hard to obtain a precise distribution of the earthquakes to further analyze the seismic sequence spatial distribution and the earthquake occurrence tendency in this source region.#br#Using the teleseismic waveforms data recorded by station Yutian near the 2014 Yutian epicenter region in Xinjiang, we investigated the crustal thickness, Poisson's ratio and the depth of crustal discontinuity beneath station Yutian by grid-search-stacking method of receiver function, further obtained the crustal S-wave velocity structure. Finally, we established the crustal velocity model in the source region for relocating the earthquakes. Based on the crustal velocity model, we relocated the 557 earthquakes which belong to the 2014 Yutian, Xinjiang, MS7.3 earthquake sequence (February 11-April 30, 2014) by the combined seismic phase arrival time and azimuth absolute location algorithm.#br#The following characteristics can be found in the relocated result. (1) The epicenters of the relocated mainshock and the foreshock are much closer to the surface rupture and the Altyn Tagh branch faults (the south Xor Kol fault and the Ashikule-Xor Kol fault) near surface fracture, and the two epicenters are only 5.4 km apart from each other. The location of the mainshock is 82.576°E, 36.076°N and the focal depth is 22 km. The location of the foreshock is 82.522°E, 36.055°N and the focal depth is 19 km. (2) The relocated distribution of the earthquakes are consistent with the surface rupture of the mainshock. The aftershock zone is mainly along NEE-SWW direction with a spatial scale of approximately 73 km long and 16 km wide. Strong variations can be found in the spatial distribution of the aftershocks southwest to the rupture fault, where the aftershock zone changes it strike direction from N-S to northeastward, which is consistent with the strike of the south Xor Kol fault and the Ashikule-Xor Kol fault, which are branches of the Altyn Tagh Fault that is close to the rupture fault. Around 77% aftershocks occurred at the southwest end of the surface rupture zone, mainly along the south Xor Kol fault, and few aftershocks occurred along the surface rupture zone, and the aftershocks at the northeast end of the surface rupture zone mainly occurred on the Ashikule-Xor Kol fault. (3) According to earthquakes distribution along profiles, the dip direction of the south Xor Kol fault (along SE direction) is opposite to that of the Ashikule-Xor Kol fault (along NW direction), which is confirmed by the field surveys.#br#Taking the characters of the south Xor Kol fault and the Ashikule-Xor Kol fault, and the distributions of relocation results, and focal mechanism solution and surface rupture zone into consideration, we speculate that the seismogenic faults of 2014 Yutian MS7.3 earthquake are the south Xor Kol fault and the Ashikule-Xor Kol fault, which are two branches of the Altyn Tagh fault zone. |
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| Keywords: | 2014 Yutian MS7 3 earthquake sequence Combined seismic phase and azimuth absolute location algorithm Relocation Seismogenic structure |
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