【摘要】 根据欧亚大陆及西太平洋地区102个数字化台站记录的近万次地震事件的长周期垂直向瑞雷波资料,利用时频分析方法测量并筛选后共得到11213条质量较高的基阶瑞雷波群速度频散资料.纯路径频散的反演中同时计算方位各向异性,反演获得了欧亚大陆及西太平洋边缘海地区(10°E—150°E,10°S—80°N)8—200s共28个周期的瑞雷波群速度及各向异性空间分布图象.瑞雷波高分辨率层析成像表明,30—60s周期,以青藏高原为中心呈极低速分布;100—120s周期,速度差异幅度较大,在东亚东部及西太平洋边缘海,自北向南显示出一条宽2500—4000km,长约8000km的巨型低速异常带.相对海洋来说,欧亚大陆各向异性强度较弱且快波方向较复杂.由于受到印度板块与欧亚板块的碰撞,中国大陆西部的各向异性强度明显大于东部.更多还原

【Abstract】 Using an frequency-time analysis method and vertical component Rayleigh wave records at 102 seismograph stations from nearly ten thousands earthquakes in the Eurasia and western Pacific marginal sea region,we measured fundamental mode Rayleigh wave group velocity dispersion curves in a period range from 8 s to 200 s for 11213 paths. We took azimuthal anisotropy into consideration when we performed pure-path dispersion inversion. Through the inversion we obtained 28 maps on spatial variation of group velocity and its azimuthal anisotropy for the periods from 8 s to 200 s in the Eurasia and western Pacific marginal sea region(10°E—150°E,10°S—80°N). The high-resolution Rayleigh wave tomographic images indicate that: for a period range from 30s to 60s,velocities are very low in and around the Qinghai-Xizang Plateau region;for a period range from 100 s to 120 s,a giant low-velocity anomaly belt,2500 to 4000 km wide and 8000 km long,is seen in eastern part of the East Asia and Western Pacific marginal sea region. Compared with the sea region,a relatively weak anisotropy and complex azimuthal variation of the fast velocity direction is observed in the Eurasia continental region. As a result of the collision between the Indian and the Eurasian plate,the anisotropy in western part of China mainland is obviously more remarkable than that in its eastern part.更多还原