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本文根据102个数字化台站记录的长周期垂直向面波资料,利用双台互相关方法测量了538条独立路径的基阶Rayleigh面波相速度频散资料,反演获得了中国大陆及边邻地区(70°E~140°E,18°N~55°N)20~120s(周期间隔为5s)共21个周期的Rayleigh波相速度空间分布图像.检测板测试结果显示中国大陆中东部地区横向分辨率可达3°,而西部及边邻地区大约5°.研究表明,中国大陆地区的Rayleigh波相速度分布横向差异显著,大致以104°E为界,可分成具有不同速度结构特征的东、西两部分.一般较短周期(20~35s)的相速度分布受地形和地壳厚度的影响较大,总体表现为东部速度高,西部速度低;塔里木盆地、青藏地块及其东缘的松潘-甘孜地块形成整个研究区内最为突出的低速异常体,蒙古西部低速特征也较清晰;东部的四川盆地、扬子地块、华南地块、松辽盆地、日本海及蒙古东部高速特征明显.随着周期的增大,青藏地块中部的低速异常体横向尺度逐渐缩小,而喜马拉雅冲断带、塔里木盆地相速度不断升高,意味着青藏低速区受到南、西北、东三个方向的高速区夹击,可能导致高原中部软弱的低速物质向东南方向迁移;同时,东部地区由高速逐渐转变为大面积的低速分布,反映东部地区岩石圈较薄而软流圈发育.随着青藏地块低速特征的减弱,印支地块北部及相邻海域、东海、东北吉林深震区、日本海、中-朝地块至蒙古东部成为120s周期上突出的低速异常体,而上扬子地块包括四川盆地高速特征依然明显,显示出稳定的古板块特征.南北地震带始终呈现出相对较低的速度特征,并成为划分中国大陆具有不同岩石圈相速度特征的东部与西部的天然分界.
Based on the long-period vertical surface wave data recorded by 102 digital stations, this paper measured the dispersion of the fundamental-order Rayleigh surface wave velocity of 538 independent paths using the dual-station cross-correlation method. The spatial distribution of Rayleigh wave velocities in 21 cycles of 20 ~ 120s (interval 5s) from 70 ° E to 140 ° E and 18 ° N to 55 ° N was obtained.The test results show that the middle and eastern regions of China Lateral resolution of up to 3 °, while the western and adjacent areas of about 5 ° .Research shows that the Chinese mainland Rayleigh phase velocity distribution of lateral significant differences, roughly 104 ° E as a boundary can be divided into structural features with different velocities East and West.The general phase velocity distribution of short period (20 ~ 35s) is greatly affected by the topography and crustal thickness, showing the high velocity in the east and the low velocity in the west. The Tarim Basin, the Qinghai-Tibet block and the eastern margin Songpan-Ganzi block formed the most prominent low-speed anomalous body in the whole study area. The low-speed features of western Mongolia are also clear. In the eastern Sichuan Basin, the Yangtze block, the South China block, the Songliao Basin, the Sea of Japan and the eastern part of Mongolia Obvious As the period increases, the lateral scale of low-velocity anomalies in the central part of the Qinghai-Tibet block shrinks gradually. However, the phase velocities of the Himalaya thrust belt and Tarim basin increase continuously, which means that the low velocity region of Qinghai-Tibet Plate is attacked by high-velocity zones in the south, northwest and east directions , Which may lead to the migration of weak low-velocity material to the southeast direction in the middle part of the plateau. At the same time, the eastern part is gradually transformed from high velocity to large-area low velocity distribution, reflecting the thin lithosphere and asthenosphere development in the eastern part. Weakening. The northern part of the Indosinian massif and the adjacent sea area, the East China Sea, the deep earthquakes in the northeastern Jilin, the Japan Sea, the mid-dynasty massif and the eastern part of Mongolia have become the low-velocity anomalous bodies that are prominent in the 120s cycle. The upper Yangtze block includes the Sichuan Basin High Speed The features are still obvious and show a stable paleo-plate feature.The North-South Seismic Belt consistently exhibits a relatively low velocity feature and becomes the natural boundary dividing the eastern and western China with different lithospheric phase velocities.