11. data report: high-resolution site survey seismic reflection data

Bralower, T.J., Premoli Silva, I., Malone, M.J., et al., 2002Proceedings of the Ocean Drilling Program, Initial Reports Volume 198

11. DATA REPORT: HIGH-RESOLUTION SITE SURVEY SEISMIC REFLECTION DATA FOR ODP LEG 198 DRILLING ON SHATSKY RISE, NORTHWEST PACIFIC1

Adam Klaus2,3 and William W. Sager3,4

ABSTRACT

In 1994, we conducted a marine geophysical and geological survey ofShatsky Rise in the northwest Pacific. The primary objective of thiscruise was to investigate the formation and evolution of the rise as wellas to collect site survey data required for ocean drilling. During thiscruise, we collected >3200 km of seismic reflection data, which formsthe primary seismic data set on which Leg 198 drill sites are located.This paper presents the seismic reflection data collected during this sur-vey.

INTRODUCTION

Ocean Drilling Program (ODP) Leg 198 returned to Shatsky Rise inthe northwest Pacific, revisiting the South High drilled during Deep SeaDrilling Project (DSDP) Legs 6, 32, and 86, as well as ODP Leg 132 (Figs.F1, F2; Fischer, Heezen, et al., 1971; Larson, Moberly, et al., 1975;Heath, Burkle, et al., 1985; Storms, Natland, et al., 1991). In addition,Leg 198 also occupied one site each on the Central and North Highs(Figs. F1, F3, F4). A high-resolution seismic reflection survey was carriedout in 1994 to determine the origin and evolution of the rise and to ob-tain site survey data required for ocean drilling. The purpose of this pa-per is to present these seismic reflection data as a first step toward inte-

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Seismic reflection data collected during cruise TN037 of the Thomas Thompson

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Location of South High, Central High, North High and Thompson Trough survey areas shown in Figures F2, F3, F4, and F5

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F1. Bathymetric map of Shatsky Rise, p. 7.

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1Examples of how to reference the whole or part of this volume.2Ocean Drilling Program, 1000 Discovery Drive, College Station TX 77845-9547, USA. [email protected] of Oceanography, Texas A&M University, College Station TX 77843-3146, USA.4Department of Geology and Geophysics, Texas A&M University, College Station TX 77843-3115, USA.

Ms 198IR-111

mailto:[email protected]

A. KLAUS AND W.W. SAGERCHAPTER 11, DATA REPORT: HIGH-RESOLUTION SEISMIC REFLECTION DATA 2

grating the regional seismic reflection data set with the Leg 198 coringand logging data.

REGIONAL GEOLOGIC SETTING

Shatsky Rise is a large (450 km long, 1650 km wide) oceanic plateaulocated in the northwestern Pacific 1600 km east of Japan (Fig. F1).Magnetic lineations (Fig. F1 inset) show that the Pacific Plate nearShatsky Rise was formed during the Jurassic and Early Cretaceous at twospreading ridges that met at a triple junction (Larson and Chase, 1972;Hilde et al., 1976; Handschumacher et al., 1988; Sager et al., 1988;Nakanishi et al., 1989, 1999). The northeast-trending Japanese linea-tion set formed at the spreading ridge separating the Pacific from theIzanagi plate to the northwest. The southeast-trending Hawaiian linea-tions formed at the ridge separating the Pacific from the Farallon plateto the northeast (Woods and Davies, 1982). Tectonic reconstructions in-dicate that this part of the Pacific Plate formed near the equator (e.g.,Larson and Chase, 1972).

The regional seafloor surrounding Shatsky Rise is deep (5.5–6.0 km)and sediment cover is thin, typically a few hundred meters (Houtz andLudwig, 1979; Ludwig and Houtz, 1979). Sediments on the top ofShatsky Rise are much thicker, up to 1.2 km (Ewing et al., 1966; Zdoro-venin et al., 1972; Neprohnov et al., 1984; Karp and Prokudin, 1985;Khankishieva, 1989; Sliter and Brown, 1993; Klaus et al., 1995) and arecomposed of Cretaceous pelagic carbonates deposited above the calcitecompensation depth when the rise was younger and nearer the equator(e.g., Sliter and Brown, 1993).

Shatsky Rise is a thick igneous construct with a seismic velocity struc-ture similar to oceanic crust, but thickened by several times under thehighest parts (Den et al., 1969; Gettrust et al., 1980; Kogan, 1981). Thissuggests that the rise has a composition similar to oceanic crust andthat dredges have recovered basalts from basement outcrops on the rise(Kashintsev and Suzymov, 1981; Sager et al., 1999). The huge size of theigneous pile, however, indicates that it was not formed by typical sea-floor spreading.

A relationship between Shatsky Rise and the Pacific-Izanagi-Farallontriple junction has long been suspected because the Japanese andHawaiian magnetic lineations converge at the rise axis (Larson andChase, 1972; Hilde et al., 1976). Magnetic bights occur in many placeswithin the lower parts of the rise, implying that the triple junction wascomposed of spreading ridges (Fig. F1) (Nakanishi et al., 1999). Becauseits size implies a large amount of volcanism, several authors have sug-gested that the rise formed as the result of a mantle plume (Sager et al.,1988; Nakanishi et al., 1989; Sager and Han, 1993; Sager et al., 1999). Apredominantly reversed magnetic polarity over the southwestern partof the South High suggests a short formation period and an extremelyhigh magma eruption rate similar to those of flood basalts and postu-lated for plume heads (Sager and Han, 1993).

There are few age dates for Shatsky Rise because basalts dredged fromit are typically too altered for radiometric dating. Despite severalattempts at drilling basement prior to Leg 198, no borehole has pene-trated basement to obtain fresher rocks. The oldest well-dated sedi-ments recovered from drilling the rise, which are at DSDP Site 306 onthe southwest side of the South High (Fig. F2), are Berriasian (earliestCretaceous; 137–144 Ma [timescale of Gradstein et al., 1994]) and were

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recovered ~80 m above a reflector thought to represent basement (Lar-son, Moberly, et al., 1975). Late Jurassic magnetic lineations M21 (148Ma) to M19 (145 Ma) bracket the South High, so this massif must haveformed near the end of the Jurassic or beginning of the Cretaceous. TheCentral High, North High, and Papanin Ridge must be younger becausethe magnetic lineations indicate that the lithosphere beneath isyounger than early Berriasian (Fig. F1 inset). Shatsky Rise gravity dataindicate Airy-type isostatic compensation typical for features emplacednear spreading ridges (Watts et al., 1980; Sandwell and MacKenzie,1989), suggesting an age for the rise near that of the underlying litho-sphere. These observations imply that the age of the rise becomesyounger to the northeast (Sager and Han, 1993).

Volcanism occurred on Shatsky Rise after the main shield-buildingvolcanic phases. Both the South and Central Highs have late-stage vol-canic ridges on their top; the one on the South High rises ~1 km abovethe level at which shallow-water fossils were dredged. Assuming thatthis ridge formed below sea level (it shows no obvious subaerial ero-sion), the high subsided as normal lithosphere (Johnson and Carlson,1992), and the fossils are autochthonous, the depth difference implies atime gap of ~8 to 9 m.y. In addition, basalts dredged from TorontoRidge on top of the South High are trachytes and trachyandesites (Te-jada et al., 1995), which are typical of fractionated, late-stage eruptions(Macdonald and Abbott, 1970).

TECTONIC EVOLUTION

Sager et al. (1999) inferred that Shatsky Rise was formed by plume-related volcanism near a triple junction from about M21 to M1 (147 to124 Ma). The three large highs and the normal lithosphere betweenthem imply that volcanism was episodic, with separate pulses buildingeach of the highs. The volume trend implies that the first eruption wasextraordinarily large and that subsequent eruptions were of diminish-ing size.

As indicated by the narrow time gap between the age of the underly-ing lithosphere and oldest sediments drilled at Site 306, Shatsky Rise ev-idently began forming near the Jurassic–Cretaceous boundary withrapid, massive eruptions that formed the South High (Sager and Han,1993). This nearly coincided with an 800-km eastward jump of thePacific-Izanagi-Farallon triple junction and a reorientation of thePacific-Izanagi Ridge between M21 and M19 (148-145 Ma) (Sager et al.,1988). Whether this large jump was caused by the eruption of theSouth High is unclear, but morphology and anomaly positions implythat the volcanic edifice formed slightly off-ridge and affected the ridgepositions (Sager et al., 1999). Ridge jumps also occurred at about thetime of formation of the Central and North Highs (M16-MI5 and M14,138 and 136 Ma, respectively), moving the triple junction farthernortheast (Nakanishi et al., 1999). The shape of the rise implies that theplates were moving rapidly southwest relative to the mantle plume(~1400 km in the 22 m.y. between M20 and M1), so the ridge jumpsmay have occurred to keep the spreading ridges located atop or near theplume (Sager et al., 1999).


DATA ACQUISITION AND PROCESSING

In 1994, we conducted a geophysical and geological survey ofShatsky Rise (cruise TN037 of Thomas G. Thompson). We collected seis-mic reflection, swath bathymetric (Hydrosweep), and potential field(magnetic, gravity) data, as well as a number of dredges and cores. Thebathymetric and magnetic data and their interpretations have beenpublished elsewhere (Nakanishi et al., 1999; Sager et al., 1999). In thispaper, we present the results of seismic reflection data acquisition.

A total of 3213 km of seismic reflection data were collected overShatsky Rise using a six-channel streamer and air gun sources (Figs. F1,F2, F3, F4, F5). The acquisition geometry, recording parameters, andprocessing sequence are summarized in Figure F6 and Table T1. The 6-channel Teledyne streamer consisted of a 70-m tow leader, a 5-mweighted section, a 25-m stretch section, six 25-m active sections, andtwo additional spare active sections (Fig. F6). Two different air gunsources were used. A single generator-injector (45/105 in3) air gun wasused primarily when conducting long profiles between survey areasover the highs. This source could be towed at relatively high speeds (~7nmi/hr) and produced two-fold data. The second source, an array offour air guns (80, 108, 150, 200 in3), was used to conduct most of thedetailed surveys over the South, Central, and North Highs. Profiles col-lected with this array were run at ~5 nmi/hr, resulting in three-fold cov-erage. We recorded the seismic reflection data at 1 ms in SEGY formaton 4-mm (DAT) and 8-mm (Exabyte) tapes using “a2d” seismic acquisi-tion software on a Sun workstation. Following the cruise, the data werecompletely processed through migration using the steps shown in TableT1. The entire seismic reflection data set collected over Shatsky Rise ispresented in Figures F7, F8, F9, F10, F11, F12, F13, and F14.

ACKNOWLEDGMENTS

We thank the captain, crew, and technical staff of the ThomasThompson. Perry Crampton and Seth Mogk from Scripps Institution ofOceanography (University of California, San Diego) provided seismicdata acquisition services. A number of scientists (Masao Nakanishi ofthe Ocean Research Institute, University of Tokyo, in particular), stu-dent watch standers, and Earthwatch volunteers contributed to theshipboard data collection. Michael Holzrichter provided invaluable ex-pertise and attention to detail while processing seismic data. MauricioCanon assisted with seismic figure preparation. Adam Klaus acknowl-edges the Ocean Drilling Program (ODP) for supporting his involve-ment throughout the project. We used GMT software (Wessel andSmith, 1995) to produce the maps. This work funded by National Sci-ence Foundation (ODP) grant OCE93-14229.

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T1. Field acquisition, recording, and processing parameters, p. 21.

F7. Seismic lines 5A, 5C, and 11B, p. 13.

F8. Seismic lines 14A, 14C, 17A, and 17B, p. 14.

F9. Seismic lines 3 and 4, p. 15.

F10. Seismic lines 5B, 6, and 7, p. 16.

F11. Seismic line 9, p. 17.

F12. Seismic lines 10, 11A, and 11C, p. 18.

F13. Seismic lines 12, 13, 14B, and 14C, p. 19.

F14. Seismic lines 15, 16, 17C, and 17D, p. 20.


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Ewing, M., Saito, T., Ewing, J.I., and Burckle, L.M., 1966. Lower Cretaceous sedimentsfrom the Northwestern Pacific. Science, 152:751–755.

Fischer, A.G., Heezen, B.C., et al., 1971. Init. Repts. DSDP, 6: Washington (U.S. Govt.Printing Office).

Gettrust, J.F., Furukawa, K., and Kroenke, L.W., 1980. Crustal structure of the ShatskyRise from seismic refraction measurements. J. Geophys. Res., 85:5411–5415.

Gradstein, F.M., Agterberg, F.P., Ogg, J.G., Hardenbol, J., van Veen, P., Thierry, J., andHuang, Z., 1994. A Mesozoic time scale. J. Geophys. Res., 99:24051–24074.

Handschumacher, D.W., Sager, W.W., Hilde, T.W.C., and Bracey, D.R., 1988. Pre-Cretaceous tectonic evolution of the Pacific Plate and extension of the geomag-netic polarity reversal time scale with implications for the origin of the Jurassic“Quiet Zone.” Tectonophysics, 155:365–380.

Heath, G.R., Burckle, L.H., et al., 1985. Init. Repts. DSDP, 86: Washington (U.S. Govt.Printing Office).

Hilde, T.W.C., Isezaki, N., and Wageman, J.M., 1976. Mesozoic sea-floor spreading inthe North Pacific. In Woolard, G.P., Sutton, G.H., Manghnani, M.H., and Moberly,R. (Eds.), The Geophysics of the Pacific Ocean Basin and its Margins. Geophys.Monogr., Am. Geophys. Union, 19:205–226.

Houtz, R.E., and Ludwig, W.J., 1979. Distribution of reverberant subbottom layers inthe southwest Pacific Basin. J. Geophys. Res., 84:3497–3504.

Johnson, H.P., and Carlson, R.L., 1992. Variation of sea floor depth with age: a test ofmodels based on drilling results. Geophys. Res. Lett., 19:1971–1974.

Karp, B.Y., and Prokudin, V.G., 1985. The structure of the sedimentary layer on theShatsky Rise according to seismic data. Tikhookkean. Geol., 3:26–33.

Kashintsev, G.L., and Suzymov, A.Y., 1981. Basalts of the Shatsky Rise. Dokl. AkadNauk SSSR, 258:86-90.

Khankishieva, L.M., 1989. The structure and seismostratigraphy of the sedimentarycover on the Shatsky Rise (Pacific Ocean). Okeanologiya, 29:178–183.

Klaus, A., Khankishieva, L., Brown, G.R., Sager, W.W., Kim, J., Nakanishi, M., 1995.Preliminary seismic reflection results from Shatsky Rise, western Pacific Ocean. Eos,Trans. Am. Geophys. Union, 76:611. (Abstract).

Kogan, L.L., 1981. Crustal structure of the Shatsky Rise of the northwestern Pacific,from deep seismic reflection profiling. Dokl. Akad. Nauk SSSR, 258:25–30.

Larson, R.L., and Chase, C.G., 1972. Late Mesozoic evolution of the western PacificOcean. Geol. Soc. Am. Bull., 83:3627–3644.

Larson, R.L., Moberly, R., et al., 1975. Init. Repts. DSDP, 32: Washington (U.S. Govt.Printing Office).

Ludwig, W.J., and Houtz, R.E., 1979. Isopach Map of Sediments in the Pacific OceanBasin and Marginal Sea Basins. AAPG Map Ser., 647.

Macdonald, G.A., and Abbott, A.T., 1970. Volcanoes in the Sea: Honolulu (Univ. ofHawaii Press).

Nakanishi, M., Tamaki, K., and Kobayashi, K., 1989. Mesozoic magnetic anomaly lin-eations and seafloor spreading history of the northwestern Pacific. J. Geophys. Res.,94:15,437–15,462.

Nakanishi, M., Sager, W.W., and Klaus, A. 1999. Magnetic Lineations within ShatskyRise, Northwest Pacific Ocean: Implications for Hot Spot-Triple Junction Interac-tion and Oceanic Plateau Formation. J. Geophys. Res., 104:7539–7556.

Neprochnov, Y.P., Merklin, L.R., and Khankishiyeva, L.M., 1984. Distribution map ofthe sedimentary cover on the Shatsky Rise. Dokl. Akad. Nauk SSSR, 277:1204–1207.


Sager, W.W., and Han, H.-C., 1993. Rapid formation of the Shatsky Rise oceanic pla-teau inferred from its magnetic anomaly. Nature, 364:610–613.

Sager, W.W., Handschumacher, D.W., Hilde, T.W.C., and Bracey, D.R., 1988. Tectonicevolution of the northern Pacific Plate and Pacific-Farallon-Izanagi triple junctionin the Late Jurassic and Early Cretaceous (M21-M10). Tectonophysics, 155:345–364.

Sager, W.W., Kim, J., Klaus, A., Nakanishi, M., Khankishieva, L.M. 1999. Bathymetryof Shatsky Rise, Northwest Pacific Ocean: Implications for oceanic plateau devel-opment at a triple junction. J. Geophys. Res., 104:7557–7576.

Sandwell, D.T., and MacKenzie, K.R., 1989. Geoid height versus topography for oce-anic plateaus and swells. J. Geophys. Res., 94:7403–7418.

Sliter, W.V., and Brown, G.R., 1993. Shatsky Rise: Seismic stratigraphy and sedimen-tary record of Pacific paleoceanography since the Early Cretaceous. Natland, J.H.,Storms, M.A. (Eds.). Proc. ODP, Sci. Results, 132: College Station, TX (Ocean DrillingProgram), 3-13.

Storms, M.A., Natlund, J.H., et al., 1991. Proc. ODP, Init. Repts., 132. College Station,TX (Ocean Drilling Program).

Tejada, M.L.G., Mahoney, J.J., Sager, W.W., and Shipboard Scientific Party, 1995. Iso-topic study of basement rocks from Shatsky Rise, northwestern Pacific Ocean. Eos,Trans. Am. Geophys. Union, 76:699. (Abstract).

Watts, A.B., Bodine, J.H., and Ribe, N.M., 1980. Observations of flexure and the geo-logical evolution of the Pacific Ocean Basin. Nature, 283:532–537.

Wessel, P., and Smith, W.H.F., 1995. New version of the Generic Mapping Toolsreleased. Eos, Trans. Am. Geophys. Union, 76:329.

Woods, M.T., and Davies, G.F., 1982. Late Cretaceous genesis of the Kula Plate. EarthPlanet Sci. Lett., 58:161–166.

Zdorovenin, V.V., Shekhvatov, B.V., Kuzmin, V.A., Suzyumov, A.Y., Filatyev, V.P., andSheina, L.P., 1972. Origin of the sedimentary cover of the Shatsky Rise. Dokl. Akad.Nauk SSSR, 202:243-245.


Figure F1. Bathymetric map of Shatsky Rise showing the locations of seismic reflection profiles collectedfor this study (solid lines). Gray rectangles show the outline of study areas shown in Figures F2, p. 8, F3,p. 9, F4, p. 10, and F5, p. 11. Bathymetric map is from Sager et al. (1999). L4, L7, L12, and L13 show thelocations of seismic profiles not shown in Figures F2, p. 8, F3, p. 9, F4, p. 10, and F5, p. 11. ODP Leg 198drill sites (1207–1214) are shown in red. Inset: Location of Shatsky Rise in the northwest Pacific showing asimplified magnetic lineation interpretation of Nakanishi et al. (1999). Numbers in parentheses below “M”anomaly labels indicate age in Ma (based on the timescale of Gradstein et al., 1994).

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Figure F2. The South High (TAMU massif of Sager et al., 1999) survey area showing the locations of seismicreflection profiles collected for this study and ODP Leg 198 drill sites (1209–1214). Numbers in boxes indi-cate seismic line numbers. Bold white lines show seismic profiles that are shown in Figure F8, p. 14. Theremaining seismic profiles are shown in Figures F13, p. 19, and F14, p. 20. Bathymetric data are from Sageret al. (1999), and depth units are meters × 102. The location of the South High survey area is shown in FigureF1, p. 7.

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Figure F3. The Central High (ORI massif of Sager et al., 1999) survey area showing the locations of seismicreflection profiles collected for this study and ODP Leg 198, Site 1208. Numbers in boxes indicate seismicline numbers. Bold white lines show seismic profiles that are shown in Figure F7, p. 13. The remaining seis-mic profiles are shown in Figures F11, p. 17, F12, p. 18, and F13, p. 19. Bathymetric data are from Sager etal. (1999), and depth units are meters × 102. The location of the survey area is shown in Figure F1, p. 7.

157°E 158° 159°

36°

37° N

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(

15 A

ug)

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Figure F4. The North High (Shirshov massif of Sager et al., 1999) survey area showing the locations of seis-mic reflection profiles collected for this study and ODP Leg 198, Site 1207. Numbers in boxes indicate seis-mic line numbers. Bold white lines show seismic profiles that are shown in Figure F7, p. 13. The remainingseismic profiles are shown in Figure F10, p. 16. Bathymetric data are from Sager et al. (1999), and depthunits are meters × 102. The location of the survey area is shown in Figure F1, p. 7.

0 20

km

162°30'E 163°00'

37°30'

38°00'N

(12 Aug) 0000

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Figure F5. The Thompson Trough survey area on Papanin Ridge showing the locations of seismic reflectionprofiles collected for this study. Numbers in boxes indicate seismic line numbers. Seismic profiles areshown in Figure F9, p. 15. Bathymetric data is from Sager et al. (1999), and depth units are meters × 102.The location of the survey area is shown in Figure F1, p. 7.

163°30'E 164°00'39°30'

40°00' N

52

50

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21002200

2300

0000(8 Aug)

1800 0100

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Figure F6. Seismic data acquisition geometry, sources, and receivers used on the Thomas Thompson cruiseTN037 over Shatsky Rise. GI = generator injector, GPS = Global Positioning System.

sea level

air gun9 m

GPSantenna

1 2 3 4 5 6

80 in3

200 in3

150 in3

108 in3

Air gun array configuration

GI-gun array configuration

45/105 in3

streamer

magnetometer

streamer

magnetometer

178 m70 m

18 m

83.5 m

37.2 m

stretch

70 m

25 m

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magnetometer

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13

Figure ric map displays the locationof all N not shown in this figure (5B,6, and ng the location of Site 1208.Bathy s of seismic lines 8 and 11B.Seismi p. 19. This figure is availablein an

SE

E

N

157° E

36°

37° N

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(

15 A

ug)

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52

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end of ove)

100 E

0km

162

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3638

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line 5C

li

F7. Top: Seismic lines (5A and 5C) collected over the North High showing the location of Site 1207. Bathymetorth High seismic lines collected; bold white lines show the location of seismic lines 5A and 5C. Seismic lines

7) are shown in Figure F10, p. 16. Bottom: Seismic lines (8 and 11B) collected over the Central High showimetric map displays the locations of all Central High seismic lines collected; bold white lines show locationc profiles not shown in this figure (10, 11A, 11C, and 12) are shown in Figures F11, p. 17, F12, p. 18, and F13,oversized format.

070006000500040003000200010000002300220021002000190010 Aug 949 Aug 94

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Line 8, part 1

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Figure , 1210, 1211, 1213, and 1214(Site 1 ismic lines collected. Seismiclines n This figure is available in anoversi

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F8. Seismic lines (14A, 14C, 17A, and 17B) collected over the South High showing the locations of Sites 1209212 is not located on one of our seismic lines). Bathymetric map shows the locations of all the South High seot displayed in this figure (14B, 14D, 15, 16, 17C, and 17D) are shown in Figures F13, p. 19, and F14, p. 20. zed format.

22 Aug

Site 1209Cross line 14C

0200010000002300220021002000190018001700160015001400 23Aug

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110010000900080007000600 13001200

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s from end of line 17A (above)

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156° E 157° 158°

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Figure ation of the seismic line is shown in Figure F5, p. 11.Bottom igh survey area. The location of the seismic profileis show sized format.

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F9. Top: Seismic line 3 collected over the Thompson Trough on the Papanin Ridge. Loc: Seismic line 4 collected during the transit from the Thompson Trough to the North Hn in Figure F1, p. 7. C/C = change in ship’s heading. This figure is available in an over

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0600070008000900100011001200130014001500

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Figure f seismic profiles are shown in Figure F4, p. 10. Middle andbottom High. The location of the seismic profile is shown in FigureF1, p. at.

S

Line 6

21002200230000004

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e 7 (above)

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F10. Top: Seismic lines 5B and 6 collected over the North High. The locations o: Seismic line 7 collected during the transit from the North High to the Central

7. C/C = change in ship’s heading. This figure is available in an oversized form

19001800170016001500140013001200110010000900C/C

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2300000001000200030004000500060007000800Aug 14 Aug 13

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11001200130014001500160017001800190020002100 E

Continues from end of lin

nues from end of line 7 (below)

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Figur Figure F3, p. 9. C/C = change in ship’sheadi

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Contin

e F11. Seismic line 9 collected over the Central High. The location of the seismic profile is shown inng. This figure is available in an oversized format.

0900 04000500060007000800 0300C/CC/C

WENSWAug 16

17001800 1400150016002000210022002300 1900

ues from end of line 9 (below)

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Figure he Central High. The location of the seismic profile is shownin Figu sized format.

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E 17001800 12001300140015001600 1100 N

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F12. Top, middle, and bottom: Seismic lines 10, 11A, and 11C collected over tre F3, p. 9. C/C = change in ship’s heading. This figure is available in an over

22002300000001000200030004000 190020002100

Aug 20 Aug 19

W N

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1500160017001800190020002100200 120013001400SEC/C

14001500160017001800190020002100 NAug 17C/C

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Figure South High. The locations of seismic lines areshown High. The locations of seismic lines are shownin Figu

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W 0500 12001300140015001600 1100

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2300000001000200 21002200Aug. 22 Aug. 21

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F13. Top: Seismic lines 12 and 13 collected during the transit from the Central High to the in Figure F1, p. 7. Middle and bottom: Seismic lines 14B and 14C collected over the South re F2, p. 8. C/C = change in ship’s heading. This figure is available in an oversized format.

2200230000000100020003000400 17001800190020002100Aug 25 Aug 24C/C

E SWC/C

NE SE

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0300040005000600

Line 13

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1100120013001400 06000700080009001000 0500C/C

ESW WC/C

NES

0100020003000400050006000700 SENC/C

NWAug 21

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Figure ocations of seismic lines are shown in Figure F2, p. 8.Bottom m. The locations of seismic lines are shown in FiguresF1, p. ed format.

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Line 15

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18001900200021002200 1700 1600 NE

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0

F14. Top and middle: Seismic lines 15 and 16 collected over the South High. The l: Seismic lines 17C and 17D collected during the transit from the South High to Gua

7, and F2, p. 8. C/C = change in ship’s heading. This figure is available in an oversiz

1600170018001900200021002200300 130014001500NE NWC/C

SE N SC/C Aug 25

0900100011001200130014001500160017001800 NW SC/C

N NWC/C

SEAug 27

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23000000Aug 29

SWAug 28

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0400050006000700080009001000 0300 0200Aug 29

NE

km

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km

0 10

km

0 10


Table T1. Acquisition and processing parameters forTN037 seismic reflection data collected for thisstudy.

Notes: Data were processed at the Ocean Drilling Program, TexasA&M University. Processing software: SIOSEIS and PROMAX.Data were processed by Michael Holzrichter and Adam Klaus.NMO = normal moveout. AGC = automatic gain control.

Field acquisition:Vessel: Thomas ThompsonCruise: TN037Start date: 23 Jul 1994End date: 4 Sep 1994Source:

1. Air gun array: 200, 150, 108, and 80 in3

2. GI air gun: 45/105 in3

Pressure: 2000 psiShot interval:

Maximum: 37 mMinimum: 25 m

Streamer:Active group length: 25 mNumber of groups: 6

Recording:Acquisition hardware: Sun SPARC10Acquisition software: “a2d”Data format: SEGYData length: 6–7 sDelay: 2–3 sShot interval: 10 sSample interval: 1 msFilters:

Low: 15 hz (24 dB/oct)High: 3khz (24 dB/oct)

Processing sequence:Pick water bottom time (WBT)DespikeBandpass filter 5–200 HzGeometry definition, insert WBT in headerMute to water bottomSpherical divergence correctionResample (2 ms)Notch filter (60 Hz)DeconvolutionVelocity analysisNMO correctionStackPick and apply static correctionFinite difference migrationTime-varying filter:

Seafloor to 0.25 s: 30–150 Hz0.25 to 1.0 s: 20–150 Hz1.0 s to end of record: 6–70 Hz

Gain (500 ms AGC)Mute to water bottom

11. data report: high-resolution site survey seismic reflection data

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