SHALLOW SEISMIC REFRACTION SURVEY IN A PART OF CHOLISTAN DESERT, DISTRICT RAHIM YAR KHAN

Abstract

This research work pertaining to shallow seismi c refraction survey of 'MANTHAR' area in Rahim Yar Kh a n District was carried out during the months of January and February 1993. The objective of the present surve y was to delineate and determine thickness and velocities of near surface weathered and subweathered layers as well as to establish relationship between velocity variation and lithology in such zones. This project was carried o u t in collaboration with the Oil and Gas Development Corpor a tion of Pakistan . These informations obtained during f i eld work are of great use in exploration seismology to correct deep reflection data for low velocity effects of weathered layer. The project area is situated 60 Km SW of Rahim Yar Khan near Manthar vill age and lies between latitude s 28 0 15' N to 28 0 05' N, longitudes 700 20' E to 70 0 30' E. The measurements were taken over 31 refraction spreads adopting reverse shooting techniques with a total of 61 shot points along five profiles (3 parallel and two cross profiles) . Each refraction spread was 2 70 meter long and the spacing between two spreads was variable. In this way a total of 61 refraction seismograms were t ake n along 2 the five pro f iles. Thus h avin g co llected informations from these seismograms, depth to f i rst refracto r and velocities of we athered and subwe athe r e d l aye rs are cal c ulated .