An Applied Study On Statics Method In Comlicated Near Surface Area

Corrections applied to seismic data to compensate for the effects of variations inelevation, weathering thickness, weathering velocity, or reference to a datum. Theobjective is to determine the reflection arrival times which would have been observedif all measurements had been made on a (usually) flat plane with no weathering orlow-velocity material present. The static corrections are essential to data acquisition,data processing and interpretation for complex near-surface areas in western China. Inthese areas, undulating ground and lateral variation in surface structure can distort thepropagation path of reflection, cause the distortion of time-distance curve and hencelead to poor image. The processing results with serious long and short wavelengthstatic problems will lead to wrong structural interpretations directly or failing drill.Solving the static correction problems under complex near-surface conditions is asystematic engineering and has the important theory significance and the actual value.To solve serious static correction problems in complex near-surface areas ofwestern China, different refraction statics methods and softwares are studied in thisthesis. The main study contents are as follows:(1) Study the features of several comlicated near surface areas and the display inseismic.(2) Research the main refraction statics methods include two-dimension interactiveiteration static correction, extended generalized reciprocal method (EGRM) staticcorrection, three-dimension fitting static correction of control point constraints,three-dimension interactive interation static correction, tomographic static correction,wave-field downward continuation static correction. The first four methods areconventional static correction methods. These methods are applied in solving staticcorrection and have obtained the good effect. As a result of these methods limitations,they have been restricted by many factors in the practical application. Tomographicstatic correction is high resolution inversion using traveltime and path of seismic rayfor inverting the velocity structure of medium. Compared with those conventionalstatic correction methods, the applicable scope of tomographic static correction ismore widespread. Wave-field downward continuation static correction has not beenapplied to seismic data processing.(3) Many refraction static correction softwares, for instance CGG, GreenMountain,Omega, have respective merits and disadvantages.(4) Many seismic data processing in complex near-surface areas are carried out bythe above mothods and softwares. These processing examples show the mostappropriate mothod and software that can solve the problem of static correction incomplex near-surface areas.