2009年7月24日西藏尼玛西南MS5.6地震研究

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600km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。

Research on the MS5.6 Earthquake of July 24, 2009 in Southwest Nima, Tibet

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 M_S5.6 earthquake, and compares these with regional seismicity during the M_S5.0 earthquake here in 2009.One to two years before the M_S5.6 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 M_S5.6 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 M_S5.6 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.