中文摘要：

印度和欧亚陆-陆板块碰撞造就的青藏高原地震活动十分频繁.但由于地理因素限制，青藏高原内部地震台站分布稀疏，因此全球地震台网很难监测青藏高原内部发生的小型地震活动.本文通过对北京大学布设的流动台阵自2007年1月至2008年3月地震记录的分析，精确定位了拉萨周边地区的79个区域小震，发现了两个可能是受到岩浆或地下水活动影响而形成的震群，以及拉萨附近一条近期比较活跃的断层，并给出了全球台网对于该地区地震定位误差的估计.

英文摘要：

The continental collision of the Indian and Eurasia plates has created the Tibetan plateau which is also a zone of active earthquakes. Because of the high elevation, there are fewer seismic stations in Tibet and therefore, most of the （small） local earthquakes were not detected by the global seismic network. Here we report our analyses of the earthquake records for the period of January 2007 to March 2008 from a Peking University′s portable seismic array. We have relocated 79 local earthquakes in the study area. Among these events, there are two clusters that could be the resulted of either magma migration or the presence of water. The data have shown that a small but active fault exists near the city of Lhasa. We have also estimated the error in the epicenter determination of local earthquakes by the global seismic network.