【摘要】 本文用1980~2000年M≥1.5的2 032个天然地震事件的38 052个-P-、S、Pm、Sm、Pn和Sn震相到时及人工地震测深给出的Moho面形态资料,利用地震层析技术反演了32°~40°N,100°~108°E区域内地壳地震波速度结构.从层析成像图象中可以得到,本区的地壳可分成4个层位.第1层(埋深约在0~3 km)为沉积层,速度梯度约为0.2s-1;第2层(埋深约在3~17 km)为上地壳,其顶部速度梯度约为0.1 s-1,下部速度横向变化较大且存在低速块体;第3层(埋深约在17~36 km)为中地壳,速度梯度约为0.03 s-1;第4层(埋深约在36 km—Moho)为下地壳,是一个契形层,总的趋势是西厚东薄,青藏高原较厚逐渐向鄂尔多斯地块和扬子准地台方向变薄,各处的地震波速度梯度不尽相同.更多还原

【Abstract】 This paper presents the three-dimensional crustal seismic wave velocity structure in the region 32°⁴0°N,100°¹08°E reconstructed through seismic tomographic inversion.We use 38 052 arrival time data of,,P_m,S_m,P_n and S_n phases recorded from 2 032 earthquakes with M≥1.5 occurred from 1980 to 2000 and the Moho interface topography data from deep seismic sounding.The 3-D tomographic image clearly reveals that the crust structure of this region consists of four layers.The top layer（about 0³ km） has a velocity gradient about 0.2 s^-1 that corresponds to the sediments.The second layer（about 3¹7 km） is the upper crust with a velocity gradient about 0.1 s^-1 at top and relative large lateral velocity variation as well as lower velocity blocks at bottom.The third layer（about 17³6 km） is the middle crust with velocity gradient 0.03 s^-1.The lower crust forms the fourth layer（about 36 km-Moho）,which is thick in the west and thin in the east.The thickness of this layer gradually reduces from the Qinghai-Tibetan plateau to the Erdos platform and the Yangtze paraplatform with different velocity gradient at different location.更多还原