WESTERN GEOPHYSICAL COMPANY
OFFSHORE ALASKA
AREA: SHELIKOF STRAIT
SHOT BY WESTERN PARTY 60 R/V ANNE BRAVO OCTOBER, 1979
PROCESSED BY WESTERN'S DENVER CENTER MARCH, 1980
USGS OCS PERMIT NO. 79-31

----RECORDING DATA----
--SOURCE--
ENERGY SOURCE			AIRGUNS
NUMBER OF GUNS			16
GUN DEPTH			20 FEET
FIRING INTERVAL			82 FEET
SHOT POINT INTERVAL		82 FEET
DISTANCE OF SOURCE TO ANTENNA	119 FEET
NORMAL GUN ARRAY SIZE		600 CU. IN. 4600 PSI

--INSTRUMENTS--
SYSTEM				DFS-5
AMPLIFIER			INST. FLOATING POINT
FILTER				5.3-128
SAMPLING INTERVAL		2 MS
RECORD LENGTH			6 SECONDS
FIELD FORMAT			100 CHANNELS 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----

PROCESS ING SAMPLING INTERVAL 4 MS

1. EDIT
2. DECONVOLVED BEFORE STACK
	TYPE - 			MINIMUM 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
7. TIME VARIANT FILTER
TIME ZONE		L.C. (HZ)	H.C.
0.00 - 1. 00 SEC	10		50
1.00- 1. 60 SEC		8		40
l.60 - 2. 20 SEC	7		35
2.20- 3. 00 SEC		6		30
3.00-6.00 SEC		5		25

VEL. ANALYSIS EVERY 5901/ FEET

----POLARITY CONVENTION----
RECORDING  : COMPRESSION PULSE POSITIVE NUMBER
PROCESSING : COMPRESSION PULSE POSITIVE NUMBER
DISPLAY    : COMPRESSION PULSE PEAK

----NOTATIONS----
SP LOCATION AT ANTENNA
PLAYBACK GAIN 13 DB
DATA CORRECTED TO SEA LEVEL

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