![]() The advantage of using such a scheme is that at high temperatures, the algorithm allows for searches far beyond the current position, while at low temperatures, it looks for improvement in the close vicinity of the current model. Unlike Metropolis simulated annealing (SA) in which each new model is drawn from a uniform distribution, VFSA draws a model from a Cauchy-like distribution, which is also a function of a control parameter called temperature. ![]() In the present study, we have applied a nonlinear optimization scheme called very fast simulated annealing (VFSA) in the inversion of 2-D dipole-dipole resistivity data to image the subsurface. Unlike linear and iterative linear methods, most nonlinear inversion schemes do not depend strongly on the starting solution, but prior information helps to reduce the computational cost and to obtain geologically meaningful results. The linear and iterative linear methods are limited because of the requirement of good prior knowledge of the subsurface. Traditionally, 2-D resistivity inversion has been performed by trial and error methods and with linear and iterative linear methods. ![]() Inversion of resistivity data has long been recognized as a nonlinear or quasi-linear problem. Successful inversion of geophysical data depends on prior information, proper choice of inversion scheme, and on effective parameterization of the model space such that the model representation is appropriate and efficient. Moreover, the proposed joint inversion method performs better than the conventional prestack inversion in both resolution and accuracy, especially for the S-wave velocity. The numerical examples demonstrate that the DTW algorithm can obtain better registered results than the conventional method. Norm-based penalty, which can significantly improve the vertical resolution and stability of inversion results. Then, a new method has been developed for the joint inversion method by combining the logarithmic absolute-criterion-based misfit function with First, to overcome the weaknesses of artificial strenching and the local cross correlation-based method, a nonstrenching and globally optimal registration algorithm, i.e., dynamic time warping (DTW), is exploited to match the P-P and P-SV waves. Therefore, an improved strategy of prestack seismic joint inversion is proposed for accurately transforming the recorded data to elastic-parameter-based interpretive information. However, registering the travel-time of P-P and P-SV waves on the identical coordinate is a significant but knotty problem for the joint inversion. P-P and P-SV waves joint inversion has been verified as an effective tool to accurately extract such fluid related parameters. S-wave velocity and mass density, which are two essential parameters in distinguishing lithology and hydrocarbon detection, are very difficult to retrieve even when long-offset gather data are used.
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