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UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
SEISMIC PROFILES OF THE OFFSHORE GULF OF ALASKA TERTIARY
PROVINCE, R/V THOMPSON, SEPT-OCT 1974
By
Roland von Huene, Bruce F. Molnia, Terry R, Bruns,
and Paul R. Carlson, U. S. Geological Survey
Open-file report
75-664
This report is preliminary and has not been edited or reviewed for conformity with Geological Survey standards
SEISMIC PROFILES OF THE OFFSHORE GULF OF ALASKA TERTIARY
PROVINCE, R/V THOMPSON, SEPT-OCT 1974
By: Roland von Huene, Bruce F. Molnia, Terry R. Bruns,
and Paul R. Carlson, U. S. Geological Survey
In September and October 1974, the U. S. Geological Survey, in
conjunction with the University of Washington, conducted a
geophysical cruise in the Gulf of Alaska (Fig. 1, Location map) to
obtain data for the appraisal of resources and environmental hazards
prior to oil and gas lease sales. Records were acquired along
approximately 6500 kilometres of track lines, as shown on Maps 1
and 2, and included seismic reflection, gravity, and magnetic data.
This report indicates the seismic reflection records that are publicly
available and it includes a text listing system specifications,
shipboard procedures and navigational accuracy, and maps of the
track lines (Maps 1 and 2). The microfilm prints of the seismic
reflection records and the shipboard logs are available from:
Alaska Technical Data Unit345 Middlefield RoadMenlo Park, CA 94025Phone: (415) 323-8111, Ext 2342
National Geophysical and Solar Terrestrial Data CenterEDS/NOAABoulder, Colorado 80302
Five reversed refraction lines were also shot; these have been
available in Open File Report 75-283 (Core and others, 1975), and
track lines for the five profiles are shown .on Map 1. The
gravity and magnetic data are still in preparation and will be
made available later.
The cruise consisted of four legs: Leg I was a transit from
Seattle, Washington, to Yakutat, Alaska, Leg II was between Yakutat
Bay and Kayak Island to collect data (Map 1), Leg III was between
Kayak Island and Montague Island to collect data (Map 2), and Leg
IV was a transit back to Seattle. The records in this open
file are from Legs II and III, with one additional line shot on
Leg IV between Kayak Island and Yakutat Bay (Line 24, Map 1). T
Table 1 shows the start and end times for the four legs and
major breaks within Legs II and III. (Note: Julian Day written
on all records is one day more than the actual Julian Day for
a particular date, due to an error at the beginning of the cruise.)
All the times on Maps 1 and 2 and written on the records are
local times.
Three separate seismic reflection systems were operated
simultaneously and provided high frequency and intermediate
frequency acoustic records. The specifications for each system
are shown in Table 2. Examples of records from each of the
systems showing annotation of the lines are shown in Figures 2-4.
Examples of the shipboard logs kept for each system are shown in
Figures 5-7.
The precision of navigation on Legs II and III was variable
because of bad weather and failure of the Decca Hi Fix system.
Navigational systems operated include not only Decca Hi Fix,
but also Satellite navigation, and Loran A. Table 3 lists
the navigation systems and shows the periods during which they
were used. The accuracy of navigation is determined by the
systems operating, and can be considered in three general
categories. Satellite navigation only (approximately 3400 km)
is probably on the order of less than 1 to 2 km. Decca
navigation (approximately 1550 km) is on the order of 250
metres or better. A third mode is with the Decca system
operating, but with obvious lane count inaccuracies as determined
by satellite, Loran, radar, bathymetry, or shoreline positions
with respect to the post-plotted lines (approximately 1550 km).
In these cases, satellite positions were used but are somewhat
more accurate due to the control of ships tracks by Decca;
position accuracies are probably on the order of 0.5 km.
Interpretation of the geophysical data has been underway
since the cruise. Preliminary reports have been released as
U. S. Geological Survey Open Files 75-283 (Core and others,
1975), 75-504 (Carlson and others, 1975), 75-505 (Molnia and
Carlson, 1975b), 75-506 (Molnia and Carlson, 1975a),
75-507 (Carlson and Molnia, 1975), and 75-508 (Bruns and
Plafker, 1975).
REFERENCES CITED
Bruns, Terry R0 and Plafker, George, 1975, Preliminary Structural Map of Part of the Offshore Gulf of Alaska Tertiary Province, U.S. Geol. Survey Open File Map 75-508.
Carlson, Paul R0 , Bruns, Terry R. and Molnia, Bruce F., 1975, Submarine slides and nearsurface faults, northern Gulf of Alaska, U.S 0 Geol. Survey Open File Map 75-504.
Carlson, Paul R0 and Molnia, Bruce F., 1975, Preliminary isopach mapof Holocene sediments, northern Gulf of Alaska, U.S. Geol. Survey Open File Map 75-507.
Core, Kenneth, Mattick, Robert, and Bayer, Kenneth, 1975, SeismicRefraction Records from a Survey in the Gulf of Alaska, U 0 S. Geol, Survey Open File Report 75-283.
Molnia, Bruce F. and Carlson, Paul R., 1975a, Base map of the northern Gulf of Alaska, U. S. Geol. Survey Open File Map 75-506.
Molnia, Bruce F. and Carlson, Paul R., 1975b, Surface sediment distribu tion map, northern Gulf of Alaska, U. S. Geol. Survey Open File Map 75-505.
TABLE iCRUISE SUMMARY Sept - Oct 1974 .
Leg
II
III
IV
Date JD Time Comments
3 Sep 249 0900 Leave Seattle 11 Sep 255 1230 Arrive Yakutat,
End Leg I
13 Sep 257 0130 Leave Yakutat14 Sep 258 0230 Anchor in Icy Bay,
weather 16 Sep 260 0100 Leave Icy Bay, resume
shooting 29 Sep 273 1030 Arrive Cordova,
End Leg II
3 Oct 277 0900 Leave Cordova278 1740 EOL, Head for PWS,
weather280 1500 Leave PWS, BOL 58 285 0230 EOL, Head for Shelter
at KI, weather 285 1000 Leave KI, resume
shooting -287 0500 Enter PWS, weather 289 1830 Leave PWS, resume
shooting295 0120 Anchor at KI, weather 295 1600 Leave KI, resume
shooting297 1200 Enter PWS, weather298 1300 Arrive Cordova,
End Leg III25 Oct 299 1000 Leave Cordova 1 Nov 306 0700 Arrive Seattle,
End of Cruise
Abbreviations used: BOL - Beginning of line EOW - End of line PWS - Prince William Sound KI - Kayak Island.
TABLE 2
SEISMIC REFLECTION SYSTEMS
Equipment
Deployed
Powe
rSe
nsor
Filters
Fire
and
Sweep
Rate
Signal
Processor'
Disp
lay
3.5
kHa
corr
elat
edTr
ansd
ucer
Hull
mounted
Hull
mounted
transceiver
1 Sec
Raytheon
PTR-105
Raytheon
UGR-196
Minisparker
Two
cages
towed
amid
Ship
vari
able
400-800
J,Single ch
anne
l Teledyne high
Reso
luti
on
Hydrophone
Stre
amer
variable
between
100r
-900
He;
gene
rall
y 250-590
He
1 Se
cTeledyne
Model
300
Amplifier
Raytheon
UGR-
196
Airg
un
Two
Bolt
40 cu
in
airg
uns
with wave
shap
e kits
Two
airguns
Towed
aste
rn2-40 cu in
200
ft si
ngle
40-80
Ha
with WSK
Chan
nel
Hydr
opho
ne
streamer
Offset approxi
mate
ly 200'
4 Se
cDe
l Norte
Mode
l 50
2 Analog
Signal
Processor
Raytheon
PER 196
TABLE 3
NAVIGATION CONTROL
StartJD
257269277278280281281285285287289290290292293294
Time
0130193021001500143003002040003010000230193001301845140007401615
EndJD Time
269272278280281281285285287289290290292293294298
1930204515001430030020400030100002301930013018451400074016151300
Nav Systems
S, L S, D DS, L DS, L S, D S, L DS, L DS, L DS, L D . S, L
Comment
Begin Leg III End Leg II Begin Leg III
End Leg III
"S, L - Stands for satellite and Loran A navigation
S, D *- Stands for Decca operating but not used for final map
D - Stands for Decca navigation.
Figu
re 1.
Index
show
ing
loca
tion
of ma
p areas
Hour m
ark:
Julian Day, Time,
Course an
d Sp
eed
Water
Depth.
Decca
shot
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t number
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ay,
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GULF OF ALASKA 1974
USGS GEOL.
SURVEY
SEISMIC LO
G:
DATE
LINE
SHIP
: T. G. THOMPSON
PAGE "49
OFy) I
TIME
COURSE &
SPEED
WATER DEPTH IN
METERS
SWEEP
SPEED
SECONDS
EDGE OR
CENTER KEY
FILTERS
HIGH/LOW
REMARKS:
GUNS,
HIGH RESOLUTION INSTRUMENTS
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