A Hybrid Algorithm for Crustal Velocity Modeling
We present a hybrid method to produce a velocity model of the Earth’s crust using evolutionary and seismic tomography algorithms. This method takes advantage of the global search ability of an evolution strategy and the quick convergence of an iterative three-dimensional seismic tomography technique to generate a model of the Earth’s crustal structure from recorded arrival times of wave fronts produced by controlled sources. The evolution strategy finds a three-dimensional velocity model with constant lateral velocity layers that minimizes the root mean square residuals computed by the tomographic algorithm. The model found is provided as the initial search point to a first arrival traveltime seismic tomography algorithm, which then computes the final three-dimensional velocity model. The method was tested with a real-world data set from an active source experiment performed in the Potrillo Volcanic Field, in Southern New Mexico. Results show that our hybrid method obtains faster convergence and more accurate results than the conventional methods, and does not require an expert-supplied one-dimensional model for the seismic tomography procedure.