SPATIAL-TEMPORAL CHARACTERISTICS OF THE FOCAL MECHANISM CONSISTENCY PARAMETER IN TIANSHAN (WITHIN CHINESE TERRITORY)SEISMIC ZONE

doi:10.3969/j.issn.0253-4967.2015.03.010

Abstract

Abstract:

Based on 306 focal mechanism solutions of M_S≥3.5 earthquakes from 2003 to 2014 in Tianshan seismic zone, we divide the Tianshan seismic zone into grids of certain size and use multiple focal mechanism solutions around each grid node to do the stress tensor inversion, and then calculate the temporal and spatial distribution of the focal mechanism consistency parameter for each grid node. On this basis the stress state of the Tianshan seismic zone is analyzed and the relationship between temporal and spatial distribution of focal mechanism consistency parameter and strong earthquakes is discussed. The result shows that the principal compressive stress of Tianshan is quite similar to the former research result; the P axis of the whole Tianshan is mainly in NS direction and in NNE and NNW in localized areas. There is a corresponding relationship between the temporal-spatial distribution of the focal mechanism consistency parameter and the strong earthquakes; strong earthquakes in the middle-east area of Tianshan Mountains often occur in the low value zones of focal mechanism consistency parameter or near the edge of the zones. Since the second half of 2011, the focal mechanism consistency parameter in the middle-east area of Tianshan Mountains presents a process from disorder to consistency, which corresponds to the group activity of strong earthquakes in Xinjiang in this period; the focal mechanism consistency parameter in the southern section of Tianshan also decreased before 2008 Wuqia M_S6.9 earthquake. In addition, we can see from the b-value image of Tianshan that earthquakes with magnitude larger than 5 occur mostly in the relatively low b value area.

Key words: Tianshan seismic zone, focal mechanism, consistency parameter, stress tensor, spatial-temporal characteristics

摘要：

基于天山地震带2003—2014年306个M_S3.5以上的震源机制解资料, 将天山地震带划分为一定的网格, 利用每个网格节点及其周围一定范围内的多个震源机制解进行应力张量反演; 计算各节点震源机制一致性参数的时空分布, 在此基础上研究了天山地震带的应力状态, 以及震源机制一致性参数时空分布与中强以上地震活动的关系.结果表明, 反演获得的天山地震带主应力与早期研究结果具有相似性, 整个天山地震带主应力轴以SN向为主, 局部区域呈现NNE、NNW向.震源机制一致性时空分布与天山地震带中强地震的发生具有一定的对应关系, 天山中东段地区中强地震大多发生在震源机制一致性参数低值分布区或其边缘附近.2011年下半年以来, 天山中东段地区震源机制一致性参数总体呈现由紊乱到一致的过程, 与该时段内新疆地区中强地震的成组活动相互对应; 2008年乌恰6.9级强震前, 南天山西段震源机制一致性参数也明显下降; 此外, 从计算得到的天山地震带b值图像来看, 2003年以来5级以上中强地震多分布于b值相对较低的区域.

关键词: 天山地震带, 震源机制解, 一致性参数, 应力张量, 时空特征

CLC Number:

P315.2

LI Jin, ZHOU Long-quan, LONG Hai-ying, NIE Xiao-hong, GUO Yin. SPATIAL-TEMPORAL CHARACTERISTICS OF THE FOCAL MECHANISM CONSISTENCY PARAMETER IN TIANSHAN (WITHIN CHINESE TERRITORY)SEISMIC ZONE[J]. SEISMOLOGY AND GEOLOGY, 2015, 37(3): 792-803.

李金, 周龙泉, 龙海英, 聂晓红, 郭寅. 天山地震带(中国境内)震源机制一致性参数的时空特征[J]. 地震地质, 2015, 37(3): 792-803.

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