Abstract:In the region where weathered layer varies terribly in lateral direction so that two adjacent receiver points show very big static moveout,appropriate datum static-correetien values can not be calcu-fated using conventional elevation correction and the linear interpola-tion whose control boint data are taken from short-refraction survey and microlog,in such a case,even automatic residual static correction can not be used to bring satisfactory result because residual static correction value is above half period of reflection waveform. People have put forward various first-arrival refraction methods for calcula-ring datum static correction values with the use of first-arrival times in raw seismic data,These methods can be called absolute refraction method,These methods need to determine real first-arrival times and to track the same refraction wave,otherwise statics errors and mis-tie will appear,Relative refraction statics(RRS)includes the essentials:(1)to take the arrival times of high-velocity refraction from far traces of common-shot records,(2)to make interpolation with reference to the control-point data of short-refraction survey or microlog so as to calcu-late datum static-correction values at shotpoints and receiver points,The total refraction moveout between two adjacent traces of a common-shot record consists of(1)the moveout due to weathered layer variation and(2)the moveout between the travel times of refraction waves which go along refractor and then travel from the refractor to the bottom of the weathered layer respectively,It is clear that the second moveout is linear with offset while the first moveout is a random high-frequency component,which can be separated out using linear correction, Errors in refraction arrival times likely appear because of the influ-once of environmental noise,Hence,RRS method requires to calculate the refraction moveouts of 5~10 common-shot records between two adja-cent control points,then computes datum static correction values of each receiver point by making linear correction of each record in light of control point data.Thus,there are more than 5 datum static-correction values for each receiver point,and the resultant correction value at each receiver point can be obtained by taking an average over all datum static-correction values at the point,Furthermore,the mean square error of static correction value at this point can be calculated,The theoretical result of syntl}ietic records show that the error of datum static correction value calculated using RRS is usually less than±3ms,seldom less than ±5ms,The processing results of seismic data collected from two areas where surface condition varies greatly shovr that the difference between datum static correction values calculated using RRS and the linear it tergolation respectively may be above 100 ms at most,and that the seismic sections obtained using RRS is much better than the seismic sections obtained using the linear interpolation,This method is applicable to some complicated areas,such as mountainous district and so on,Its originality is nether calculating real initial time nor tracking same refra-ctor,It is easy and controls quality very well,RRS program for IBM personal computer is widely used in field exploration.