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首页> 外文会议>Conference on mathematical methods in geophysical imaging >Fast 3D two-point ray tracing for travel-time tomography
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Fast 3D two-point ray tracing for travel-time tomography

机译：快速3D两点射线追踪，用于旅行时间断层扫描

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Abstract: The determination of a correct subsurface velocity model is of strategic importance for seismic imaging of complex geologies by use of 3D prestack depth migration. To accomplish this task we have developed a 3D reflection tomography software (called jerry) that is designed to handle methods of realistic complexity and that is fast enough to allow practical 3D applications. We use a blocky representation of the subsurface with a B-Spline parametrization for interface geometries and for velocity distributions within layers. The forward problem of reflection tomography is formulated as a two-point ray tracing problem and is solved by a bending method based on Fermat's principle with an approximation of the actual ray geometry within a layer by a straight line. The C$+2$/ property of the model parametrization allows to calculate exact derivatives of the traveltime function with respect to the model and thus to calculate rays (trajectories that satisfy Fermat's principle) from initial trial trajectories. The trajectory initialization is based on Snell's law for transmission/reflection at interfaces and uses an iterative method to calculate the intersection point between straight rays and interfaces. The introduction of non-physical ghost interfaces allows to improve the ray path approximation and thus the accuracy of the calculated traveltimes.!9
机译：摘要：通过使用3D叠前深度偏移，确定正确的地下速度模型对于复杂地质地震成像具有战略意义。为了完成此任务，我们开发了3D反射层析成像软件（称为jerry），该软件旨在处理现实复杂的方法，并且速度足够快，可以用于实际的3D应用程序。我们使用B样条参数化对地下进行块状表示，以实现界面几何形状和层内速度分布。反射层析成像的前向问题被公式化为两点射线追踪问题，并通过基于费马原理的弯曲方法解决，并通过直线近似一层内的实际射线几何形状。通过模型参数化的C $ + 2 $ /属性，可以计算出旅行时函数相对于模型的精确导数，从而可以从初始试验轨迹计算出射线（满足费马原理的轨迹）。轨迹初始化基于斯涅尔定律进行界面的透射/反射，并使用迭代方法来计算直线与界面之间的交点。引入非物理重影接口可以改善射线路径逼近度，从而提高计算出的行程时间的准确性！9

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