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| | Abstract | | We applied a multistage technique to a group marching method (GMM) in order to calculate traveltimes and ray paths for both refractions and reflections. The GMM is a numerical scheme solving an eikonal equation with unconditional stability and computational efficiency. In a conventional GMM, the first arrivals and the shortest ray paths from source to receivers are calculated naturally. In a multistage GMM, the traveltime field of the down-going wave from a source to a reflection boundary is calculated at the first stage, and then the traveltime field of the up-going wave from the boundary to receivers is calculated at the second stage. A ray path of the reflection is calculated by connecting a ray from a receiver to a reflection point based on a gradient of the second-stage up-going traveltime field, and a ray from the reflection points to a source based on a gradient of the first-stage down-going traveltime field. This method will be useful in a forward modeling for a structural interpretation or a traveltime tomography using both the refractions and the reflections, and in a simulating the reflections on an assumed subsurface model for an optimal survey design. |
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