用CT技术反演面波Q值空间分布及其研究前景(英文)

Inversion of Spatial Distribution of Surface-wave's Q-Value in Earth-crust by Using CT Technology and its Prospect

本文运用CT技术反演地壳面波品质因数Q值空间分布,采用在医学上X—CT技术中的卷积反投影方法,引用 Radon 变换反演和图像重建方法来拟合地壳面波 Q 值的空间分布。由600次地震实际的2200条地震波射线的面波振幅、周期资料,进行实际地壳 Q 值反演,首先获得四川盆地附近:北纬26°—34°,东经103°—112°范围的面波 Q 值分布,作出该区 Q=210-255的等值线图,其平均 Q 值为225,在四川盆地中部面波 Q 值偏高,这可能与该盆地中部沉积物介质比较均匀,非弹性成分较少有关。然后以上述经纬度范围的四川盆地为基地,将面波扫描的方框分别向北、向南、向西、向东移动各2度,再做四次 Q 值成像,取其中间重迭部位,计算 Q 值的平均值及其残差,得每经纬度为半度的像素中观测误差的空间分布图。求得该范围的平均误差为8%。进一步将平面范围地震面波 Q 值成象扩大成球面上的投影成像:系将上述单框 Q 值图像沿经纬度方向各移动2度进行叠加,使若干个平面小单框复盖在预想的球面上的大区域上,除去边缘部分之外,在该范围的经纬度网上都叠加有一个以上的 Q 值数据,通过计算每个网点上的平均 Q 值及其标准误差的等值线,可获得球面上大范围的 Q 值成象图。得到了7×7框范围内的面波 Q 值分布图。本文探讨了 Q值成像在改进面波震级标度和解释地震震级的路径校正值以及为地震监测预报服务的研究前景。

In this paper,the technology of seismic tomography on the inversion of seismic wave's Q-value in the earth crusthas been studied.We get the spatial distribution of quality factor Q-value in the carth-crust.The convolution back projection method of imaging reconstruction in X—CT technology is used to inverse thetwo dimensional distribution of the surface wave quality factor in earth crust.The real seismic data is used to inversethe Q-values of the earth crust.For the area within the range of 26°—34°N and 103—112°E,the surface wave am-plitude and period data of 2200 seismic wave rays corresponding to 600 events are exploited to produce Q contourranged from 210 to 255,the averaged Q is 225.The Q value is more high in the middle of Sichuan basin.It is possi-ble that the sedimentary medium is rather homogeneous and elastic in the area.We get some rescarch about the relatedaccuracy estimation problems.The quality factor Q-value's spatial distribution in the crust may be used to improvemagrnitude scale and serve to earthquake monitoring,measurement and prediction.