基于Cesium的震源机制解三维可视化方法

The 3D Visualization Method of Focal Mechanism Solution Based on Cesium

以地质模型为基础的地学类数据正在向三维信息化发展,其中Cesium作为一款基于Web的开源三维GIS(Geographic Information Systems)引擎被广泛使用。而目前震源机制解作为地震领域的重要参数,其绘制结果是二维的沙滩球,在三维的可视化系统中无法达到形象直观的效果。针对这一问题,提出一种基于Cesium的震源机制解三维可视化方法,利用辐射花样计算公式对断层参数和矩张量两种形式的震源机制解分别计算出震源球上每一点的振幅,并在以方位角为横轴、离源角为纵轴的图中对负振幅的点填充白色,对正振幅的点按断层类型进行填色,得到震源球的二维辐射花样分布图,将此图以纹理的方式贴在基于Cesium框架绘制的震源球上,并将震源球绕其局部坐标系的Z轴逆时针旋转90°,实现了震源机制解的三维可视化。使用欧洲地中海地震中心提供的正断层、逆断层、走滑断层三种断层类型的震源机制解分别进行了计算和显示,并与使用GMT(Generic Mapping Tools)绘制的二维沙滩球进行对比,结果显示,两者基本一致,表明该方法是正确有效的,且显示效果更加形象、直观,可在三维地质建模、地震领域的三维信息化建设研究中发挥作用。

With the rapid development of geo-data based on geological model towards 3D information technology,Cesium as an open source web-based 3D GIS(geographic information systems)engine,is widely used.At present,focal mechanism solution as an important parameter in the seismic field,its drawing result is only restricted to two-dimensional beach ball,which cannot present the stereoscopic effect as in the three-dimensional visualization system.Therefore,a three-dimensional visualization method of focal mechanism solution based on Cesium is proposed in this paper.The amplitude of each point on the focal sphere is calculated by using the radiation pattern calculation formula for the two forms of fault parameters and moment tensor,and the negative amplitude is filled white as well as the positive amplitude is filled custom color accord to fault type in the figure with azimuth as the horizontal axis and off-source angle as the vertical axis to obtain the two-dimensional radiation pattern distribution map which is pasted on the focal sphere drawn based on Cesium framework in the form of texture,and rotate the focal sphere 90 degrees counter clock wise around the Z axis of its local coordinate system,then the three-dimensional visualization of focal mechanism solution is realized.When applying the 3D visualization model proposed in this paper,we use the focal mechanism solution of normal fault,reverse fault and strike slip fault provided by the European Mediterranean Seismological Center for calculation and display.It turns out that our results are basically consistent with the results from GMT(generic mapping tools),and the display is more visual and intuitive,indicating that the method is correct and effective.thus proving its effect in the 3D geological modeling and 3D information construction in seismic field.