中文摘要：

利用78364条Pn射线的走时资料，采用地震层析成像方法反演蒙古及邻区上地幔顶部Pn速度结构．反演结果表明，蒙古及邻区Pn平均速度为8．08km／s，横向速度变化量从0．39km／s至＋0．30km／s．速度高异常区主要分布在阿尔泰山地区及准噶尔盆地、塔里木盆地等地，在阿尔泰山地区Pn速度最大异常达＋0．30km／s．速度偏低的地区主要在贝加尔湖、华北平原、渤海湾等地，在贝加尔湖西南呈现出强烈的低速度异常达～O．39km／s，可能与该区新生代的火山活动有关．

英文摘要：

This paper uses the travel times of 78364 Pn waves and seismic tomography to invert for the Pn velocity structure at the top of upper mantle in Mongolia and neighboring regions. The result indicates that the Pn velocity is 8. 08 km/s on average and varies laterally between -0.39 km/s and ＋0.30 km/s. The high velocity anomalies are mainly distributed beneath the Altay mountains, ]unggar basin, and Tarim basin; in the Altay mountain region the largest Pn anomaly reaches ＋0.30 km/s. The regions of lower velocity include mainly Lake Baikal, North China Plain, and Bohai Bay~ to the southwest of Lake Baikal the strong low velocity anomaly reaches -0.39 km/s, which is probably related to the Cenozoic volcanic activity in the area.