2009年7月24日西藏尼玛西南MS5.6地震研究

沈小七1， 索仁2， 王俊1， 曹华文2

(1.安徽省地震局，安徽 合肥230031； 2.西藏自治区地震局，西藏 拉萨850000)

摘要：主要研究2009年7月24日西藏尼玛西南MS5.6地震的基本参数、地震序列特征、震源参数、发震构造等；利用震中附近600 km范围内台站测定参数研究地震的震源机制解，与哈佛大学给出的震源机制解较一致，且与通过现场考察的发震断层走向具有一致性。研究认为本次地震发生在冈底斯山—拉萨块体内部，断裂为NNW向，主要受张应力作用产生左旋走滑正断层活动。此外还分析了震前地震学条带异常特征，结束表明，震前1年出现NW向条带非常显著，研究结论为该地区今后地震预测提供科学依据。

关键词：尼玛西南5.6级地震； 地震参数； 地震条带

收稿日期：*2013-03-23

基金项目：中国地震科技星火计划攻关项目(XH14026)；地震行业专项(20130812)；安徽省地震局地震科研基金重点项目(20110502)

作者简介：沈小七(1969-)，男(汉族)，安徽安庆人，高级工程师，主要从事地震分析预报、地震地质等研究工作.E-mail：ahqxs@sina.com

中图分类号:P315.2文献标志码：A

DOI:10.3969/j.issn.1000-0844.2015.01.0181

Research on theMS5.6 Earthquake of July 24，2009 in

Southwest Nima，Tibet

SHEN Xiao-qi1， SUO Ren2， WANG Jun1， CAO Hua-wen2

(1.EarthquakeAdministrationofAnhuiProvince，Hefei，Anhui230031，China；

2.EarthquakeAdministrationofTibetAutonomousRegion，Lhasa，Tibet850000，China)

Abstract：An M5.6 earthquake struck Nima，in Tibet，on July 24，2009.According to the displacement of the earthquake surface rupture and destruction of buildings， the earthquake macroscopical epicenter lay between Juncang Town in Nima County and Cishi Town in Cuoqin County.The intensity of seismic area was VII.This article studies the basic parameters of earthquake sequence features, source parameters，seismogenic structure，and so on，making use of related parameters to discuss the focal mechanism solutions identified as consistent with the event by Harvard University.The results are confirmed by field investigation.An inspection of the scene of the earthquake recorded the seismic characteristics of every type of building in the region，and the reasons for damage are summarized，and suggestions made for earthquake disaster prevention and mitigation.This article establishes that the earthquake occurred within the Kailash-Lhasa block，displaying NNW trending mainly under tensile stress generated by a sinistral strike slip with normal faulting. In addition，this article analyzes minor earthquake activity and the imaging features of regional seismicity in Nima before the MS5.6 earthquake，and compares these with regional seismicity during the MS5.0 earthquake here in 2009.One to two years before the MS5.6 earthquake，Nima experienced strong earthquake bursting，and moderate earthquakes of magnitude 3.0 and 4.0 were assigned a state of “Significantly Enhanced” across the area.Twelve months before the MS5.6 earthquake，a seismogenic gap of earthquakes of magnitude 3.0 and 4.0 occurred in the source area，with abnormal images of almost adjoining distribution.Before the MS5.6 earthquake，the strong seismic status and abnormal images of small earthquakes in Tibet were the same as associated with the M4.9 earthquake in 2009.The outcomes of this paper are a scientific basis with which to predict earthquakes in future.

Key words： southwest NimaMS5.6 earthquake； seismic parameters； seismic belt

0引言

2009年7月24日在西藏那曲的尼玛县西南部(31.3°N，86.1°E)发生MS5.6地震。地震发生后自治区地震局组成地震现场工作组于当日下午从拉萨出发，奔赴震区开展地震现场的灾害评估、科学考察和地震应急工作。

本文对该地震的主要研究成果进行整理分析，以期为本区的地震事件研究提供参考。

1地震参数

根据中国地震台网中心(CENC)记录(表1)，2009年尼玛西南MS5.6地震的发震时间：2009 年7月24日11时11分58.0秒；震中位置：北纬31.30°，东经86.1°；……