【摘要】 藏北高原自新生代以来不仅发生了强烈的火山作用,而且现今的地震活动性仍然强烈.本文收集了2011年前藏北高原区发生的地震事件(源自NEIC)及相应的震源机制解数据(源自GCMT),结合地质与地球物理等相关资料,初步分析表明藏北高原地壳整体上处于伸展应力状态.然而,因区域构造应力场及构造环境差异,将藏北高原地震活动区分为两个地震活动区,即西昆仑地震活动区和藏北中部火山岩区.西昆仑区的地壳应力状态呈东西向伸展,而岩石圈地幔部分主要以南北汇聚为主,表明西昆仑区域下的地壳与岩石圈地幔应力状态是解耦的,而这种解耦机制需要更进一步的研究.而在藏北中部火山岩区的地壳的主张应力场为NNE-SSW的走滑和正断层性质的伸展,尽管缺乏该区域下的岩石圈结构特征认识,但是依据幔源性质的钾质和超钾质火山岩成因模式,认为其下的岩石圈地幔也处于伸展状态,该区域下的地壳与岩石圈地幔同处于伸展应力环境中,表明藏北火山岩区下的结构特征更加复杂,亟待开展相关探测与研究.更多还原

【Abstract】 Cenozoic volcanism was violent and Seismicity is still strong in the Tibetan Plateau.We have collected all the seismic events data from NEIC and focal mechanism solution data from GCMT before 2011 and combined with the geological and geophysical data beneath the northern Tibetan plateau.Analysis of data on the region suggest that the stress condition of crust is in extension.However,seismic activity area in the Tibetan plateau is divided into western Kunlun and volcanic zone of northern Tibet by the differences of areal structure stress field and tectonic setting.Eastward extension of the crust stress condition and the major convergent in nearly NS oriented of lithospheric mantle beneath western Kunlun suggests that the stress condition of crust and mantle had decoupled on the region.But the crust stress field beneath volcanic zone of northern Tibet is mainly NNE-SSW extension of the strike-slip and normal faulting.Though the lack of understanding of lithospheric structure on this region,but according to the petrogenesis of mantle-derived potassic and ultrapotassic volcanic rocks suggests that the structure of lithospheric mantle was stretching yet.The crust and lithospheric mantle extension beneath volcanic area in the northern Tibetan plateau suggests that structural features is very complex and explotation and research work will be carried.更多还原