Development of the data processing of seismic reflection survey for shallow layers

Abstract

4 computer program modules had been developed on 16-bit microcomputer for proessing data obtained from seismic reflection survey for shallow layers (=<150 m). The first module is used for static correction. The second module is used to sort the common mid point data. The third module is used to apply normal moveout correction. And the fourth module is used to make velocity analysis. The testing of these programs was done on model data and field data. The program function as expected in both cases. In comparing on the method of data collection between common mid point method and common offset method, the survey area is Ban Rong Wua and Ban Huai Kieng, north of Chiengmai. Ban Rong Wau lines on flood plain ; Sediments compose of sand and silt. Ban Huai Kieng is river terrace where gravel and were deposited. From this geological conditions, it is concluded that the survey area have some reflectors. The comparison on time spent on data collection, using 3 labours and 1 operator shows that for 200 line-meter the average time is 4 Hours for common mid point data collection and 3 Hours for common offset data collection. The time spent on data processing are : 2 minutes for static correction of 12 traces/record, 1 minute for common mid point sorting for 6 traces/record, 1 minute 45 seconds for normal moveout correction of common mid point data, 50 seconds for normal moveout correction of common offset data, and greater than 15 minutes for velocity analysis of 6 traces/record. The data quality which are shown as seismic section tend to be better for common mid point method at Ban Rong Wua and to be the same at Ban Huai Kieng. It is concluded that seismic reflection method can be used for shallow investigations.