Ultra efficient methods for modelling waveforms in seismic surveys

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In this study we developed efficient numerical methods for modeling seismic waveforms in seismic exploration.In the first year we developed a very efficient procedure to calculate plane-wave responses of arbitrary 1-D media, such as gradient velocity or randomly heterogeneous structures, using the finite-difference method in the time domain (FDTD). This may be useful for analysis of reflection survey or seismic logging data.In the second year we developed an ultra efficient method for modeling seismic waveforms in refraction or wide-angle reflection surveys. The most common form of seismic exploration remains a nearly linear survey with data acquisition lines including the source and receivers. For this situation we developed a 2.5-D modeling method for the simulation of 3-D seismic wavefields in media varying in two dimensions. The computer memory requirements and computation time are only slightly larger than those for 2D computations. We demonstrated the validity and efficiency of the technique with numerical examples, including a profile across a realistic model of subduction zone structure.