The Technology Of Static Correction Using Ray Trace In Inhomogeneous Surface

The static corrections are essential to data acquisition, data processing and interpretation for complex near-surface areas in the western China. The processing results with serious long and short wavelength static problems will lead to wrong structural interpretations directly or failing dill. So how to solve the static correction problems caused by the changes of near surface factors with first-break information is a key problem for data processing in the complex near-surface conditions is a systematic engineering .First ,careful field weathering investigation must be done, then we have to take full advantages of first-break information and field weathering investigation information to compute field static correction and large residual static correction with various first-break static methods.To solve serious static correction problems in complex near-surface areas of western China, different first-break static methods are studied in this thesis. The major methods include raytracing algorithm, ray-base tomography, near-surface geological inversion methods. And we studied the problem of"static correction"is not"static".After an evaluation of existing raytracing techniques, we first focus on the shortest paths raytracing technique, implement the shortest paths raytracing on graph theory .It is more accurate and efficient than other methods. We then use it to simulate the first break propagations in several typical near-surface geological models. The results show clearly the features of wavefronts, raypaths, and time-distance curves.Sudden changes of surface in rugged areas disarrange travel time of seismic waves, and make if more difficult to explore in these areas .At present, all widely used static correction methods in industry are based on the Surface Consistency Hypothesis. The Surface Consistency Hypothesis supposed that the speed in low-speed layer is far less than in bedrock, and seismic rays travel in low-speed layer vertically. So, traces of all rays from or to the certain point are exactly the same. But in mountainous regions, the hypothesis quiet conflicts with actual geologic situation, While near surface velocity and float downward velocity discrepancy not too much, ray emergence surface is not vertical. The same receiver station pick up wave path of shallow refraction is not same. Therefore, difference is presented between statics with Surface Consistency Hypothesis and statics without it (call if surface inconsistency statics ).The reason and value of the difference are discussed We can get it ,static correction value is not only rest with datum plane's selection but also rest with offset and seismic wave propagation path. Static correction is not only with shots and receivers' location but also with seismic wave transit time change. It can say that static correction is not only space-varying quantity but also time-varying quantity.