------------------------------------------------------ WESTERN GEOPHYSICAL COMPANY OFFSHORE ALASKA AREA: SHELIKOF STRAIT SHOT BT WESTERN PARTY 6O R/V ANNE BROVO OCTOBER, 1979 PROCESSED BT WESTERN'S DENVER CENTER MARCH, 198O USGS OCS PERMIT NO. 79-33 (sic - data were acquired under 79-31) ------------------------------------------------------ RECORDING DATA ------------------------------------------------------ SOURCE ------------------------------------------------------ ENERCT SOURCE AIRGUNS NUNBER OF GUNS - 16 GUN OEPTH - 20 FEET FIRING INTERVAL - 82 FEET SHOT PO INT INTERVAL - 82 FEET DISTANCE OF SOURCE TO ANTENNA - 19 FEET NORMAL GUN ARRAY SIZE - 600 CU. IN. 4600 PSI INSTRUMENTS ------------------------------------------------------ SYSTEM - DFS-S AMPLIFIER - INST. FLOATING POINT FILTER - 5.3-128 SANPLING INTERVAL - 2 MS RECORD LENGTH - 6 SECONDS FIELD FORMAT - 100 CHPNNELS SEG-B GAPPED CABLE ------------------------------------------------------ TYPE CABLE - STREAMER CABLE LENGTH - 7790 FEET CABLE DEPTH - 35 FEET LEAD IN - 794 FEET GROUP INTERVAL - 82 FEET NUMBER OF GEOPHONES PER GROUP - 20 NUMBER OF GROUPS RECORDED - 96 ------------------------------------------------------ PROCESSING SEQUENCE AND PARAMETERS ------------------------------------------------------ PROCESSING SAMPLlNG INTERVAL - 4 MS 1. EDIT 2. DECONVOLVED BEFORE STACK TYPE - MINIMUN PHASE INVERSE FILTER WINDOW LENGTH - 3 EQUAL ZONES OVERLAP - 20% OF ZONE LENGTH OPERATOR - 140 MS PREDICTION DISTANCE - 4 MS 3. NMO STACK 4800% 4. COHERENT NOISE FILTER 5. MIGRATION 6. RMS GAIN 6. TIME VARIANT FILTER TIME ZONE - L.C.(HZ) - H.C. 0.00-1.00SEC - 10 - 50 1.00-1.6OSEC - 8 - 40 1.60-2.20SEC - 7 - 35 2.20-3.00SEC - 6 - 30 3.00-6.00SEC - 5 - 25 ------------------------------------------------------ POLARITY CONVENTION ------------------------------------------------------ RECORDING : COMPRESSION PULSE POSITIVE NUMBER PROCESSING : COMPRESSION PULSE POSITIVE NUMBER DISPLAY : COMPRESSION PULSE PEAK (INCREASING BLACK) NOTATIONS ------------------------------------------------------ SP LOCATION AT ANTENA PLAYBACK GAIN 13 dB DATA CORRECTED TO SEA LEVEL