鄂尔多斯及邻区基于程函方程的面波层析成像

Surface wave tomography based on Eikonal tomography in Ordos and adjacent areas

利用鄂尔多斯及邻区的固定台站和流动台站记录到的面波资料,使用基于程函方程的面波层析成像的新方法,得到了鄂尔多斯及邻区12~150 s周期的瑞利波相速度的分布图.短周期的相速度很好的揭示出鄂尔多斯及邻区的山脉隆起和拉张盆地等引起的高低速异常的分布特征.中等周期的相速度显示鄂尔多斯盆地内部为显著的高速异常,而它的四周逐渐地被低速异常所包围.大同火山区的低速异常在垂向上进行不断的延伸和扩展,推测是由于其下方的岩浆上涌引起地壳和上地幔顶部升温造成的.长周期的相速度显示鄂尔多斯盆地下方在岩石圈深度范围内,以北纬38°为界南北部岩石圈的差异比较明显,呈现南部厚北部薄的特点.研究发现研究区从西到东岩石圈逐渐减薄,这可能是由于受到太平洋板块俯冲引起的地幔热物质上涌和运移的影响.

Based on the surface wave data recorded by the temporary seismic stations and the permanent seismic stations in Ordos and adjacent areas,and the new method of surface wave tomography based on Eikonal equation,the distribution images of Rayleigh wave phase velocity at the periods of 12~150 s in Ordos and adjacent areas were obtained.At short periods,phase velocity images well reveal the distribution characteristics of high and low velocity anomalies caused by mountain uplift and extensional basin in Ordos and adjacent areas.At medium periods,phase velocity images show that the Ordos basin is surrounded by high velocity anomalies and its surrounding areas are gradually surrounded by low velocity anomalies.The low velocity anomalies in the Datong volcanic area extend and expand continuously in depth,which is speculated to be caused by the heating of the crust and the top of the upper mantle caused by the upwelling of magma below.At long periods,phase velocity images show that the lithosphere depth in the lower part of the Ordos basin,bounded by 38°N,has obvious differences in the lithosphere between the south and the north,which is thick in the south and thin in the north.The study found that the lithosphere in the study area gradually thinned from the west to the east,which may result from the upwelling and migration of mantle hot materials caused by the subduction of the Pacific plate.