Wave equation travel time tomography based on the adjoint method

Wave equation travel time Tomography based on the adjoint method is an advanced and useful theory to simulate the wave propagation and inversion. More practices and applications need to be implemented widely. A real seismic survey project is been done as an example in this paper with the above theory implementation. Also the comparison results can be funded in this paper.;Wave equation travel time Tomography based on the adjoint method is also a complex, long running, and repeated process. A desire to free hand from the inversion process needs to be met. Windows Workflow Foundation in .net 4.0 provides the feasibility to implement the inversion process automatically. The visual studio 2010 provides friendly platform for users to simply drag the function activity to design all kinds of workflow which also allowed both forward and backward workflow design. The benefits of the automatic implement the wave equation travel time inversion workflow is not limited to save the operating time, but also improves the inversion efficiency by reducing the un-continued running gap between each step. Furthermore, the automatic process provides the feasibility to implement other inversion process and reduce the seismic imaging period.;Wave Equation travel time tomography based on the adjoint method simulates the wave propagation path exactly in three-dimensional media which provides more accurate velocity model and much higher resolution image than the ray tracing theory which tracks the wave propagation path in two-dimensional media. That is also a big reason why the wave equation tomography is more accurate than the conventional tomography. Wave equation travel time Tomography based on adjoint method is not a new theory which was developed in 1980s but it was been limited by the requirements of large computing source which is used to calculate three-dimensional wave equations and to construct three-dimensional Fréchet kernel. Until recent years, following by the barge computing technology development, applying wave equation travel time tomography to large scale of earthquake and exploration become implementable.;In the practice of wave equation travel time tomography based on the adjoint method, forward wave-field and adjoint wave-field are been calculated by using source time function instead of storing green function. For adjoint wave-field, the wave field source is been derived by using reversed time signal at receiver as simultaneous source which is based on reciprocity of the green function property. And also all the synthetic seismogram relative to one shot can be simulated simultaneously for each wave-field calculation. Three-dementional Fréchet derivative is constructed by using both forward and adjoint wave-fields. Without storing green function, large disk space could be saved. In the meanwhile the simulation of two wave-fields will double the memory required. Since Hessian is also not available in the calculation, inversion process needs to be solved iteratively.