OTC 14139
High-Resolution AUV Surveys of the Eastern Sigsbee Escarpment
Robert A. “Tony” George, C & C Technologies, Inc., Lindsay Gee, Interactive Visualization Systems, Inc., Andrew W. Hill,
James A. Thomson and Philippe Jeanjean Ph.D., BP Exploration and Production Inc.
Copyright 2002, Offshore Technology Conference
This paper was prepared for presentation at the 2002 Offshore Technology Conference held in
Houston, Texas U.S.A., 6–9 May 2002.
This paper was selected for presentation by the OTC Program Committee following review of
information contained in an abstract submitted by the author(s). Contents of the paper, as
presented, have not been reviewed by the Offshore Technology Conference and are subject to
correction by the author(s). The material, as presented, does not necessarily reflect any
position of the Offshore Technology Conference or its officers. Electronic reproduction,
distribution, or storage of any part of this paper for commercial purposes without the written
consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print
is restricted to an abstract of not more than 300 words; illustrations may not be copied. The
abstract must contain conspicuous acknowledgment of where and by whom the paper was
presented.
Abstract
Recent oil and gas exploration efforts have met with success
in the deepwater environment along the Sigsbee Escarpment
in the north-central Gulf of Mexico. The topography of the
Sigsbee is steep and irregular with numerous faults and slumps
occurring on the Escarpment face. The complex topography is
challenging for the collection of high-resolution geophysical
data. Engineering quality survey data for the installation of
export pipelines, infield flowlines and production facilities is
needed. BP Exploration and Production Inc. (BP) recognized
the limitations of the current survey technology and put forth a
push in the industry for the development of a deepwater,
Autonomous Underwater Vehicle (AUV) survey platform. A
commitment for state-of-the-art survey technology by BP
resulted in C & C Technologies, Inc. (C & C) teaming with
Kongsberg Simrad to develop an AUV platform for the
deployment of high-resolution survey instrumentation capable
of surveying to a maximum depth of 3,000 meters. An
overview of the system, data processing and data examples
from missions completed across the Sigsbee Escarpment are
presented in this paper.
The data from the AUV has provided a dramatic advance
in the ability to map the seafloor, but it produces a large and
diverse data set that can challenge our ability to process and
manage the data. The great density of these digital data,
however, offers the opportunity to take advantage of
interactive 3D visualization techniques that can improve the
efficiency and accuracy of processing, and provide an
unprecedented perspective of seafloor morphology and
processes. Fledermaus interactive 3D visualization software is
used to aid in the analysis of the data. This program allows
the interpreter to analyse in a single scene all the data from
AUV survey, including the seabed from the multibeam sonar,
draped side scan, subbottom profiles and the planned
pipe routes.
Introduction
The HUGIN 3000 Autonomous Underwater Vehicle (Figure
1), a third generation AUV from Kongsberg Simrad, resulted
from the engineering efforts of C & C and Kongsberg
Simrad1. The payload of the AUV consists of three major
remote-sensing systems2, 3 (Figure 2). A Kongsberg Simrad
EM2000 Multibeam collects high-density soundings in a
swath perpendicular to the direction of motion. The AUV
depth is recorded with a precision, survey quality depth
sensor. Sonar imagery is logged with an Edgetech dualfrequency side scan sonar and high-resolution seismic profiles
are obtained with an Edgetech 216 chirped subbottom sonar.
Inertial navigation is used for positioning of the AUV and a
battery supplies power for mission times approaching 45
continuous hours. Numerous ancillary sensors monitor the
AUV and feed information to the artificial intelligence
programs controlling the motion and health of the AUV.
The construction of the third-generation HUGIN AUV was
performed at Kongsberg Simrad's Norway facilities in late
1998. The vehicle was delivered to the United States in
August 1999 and sea trials began in the Gulf of Mexico. Sea
trials were conducted over the next several months and the
HUGIN was officially commissioned as a commercial survey
vehicle in January 2000. Since this time, the HUGIN has
completed more than 6,000 line miles of deepwater data
acquisition on the continental slope and upper continental rise
in the Gulf of Mexico.
Navigation Data Processing
The AUV positioning implements the same type of intertial
guidance technology developed for positioning precision
guided missiles. This technology is relatively new to the
survey industry and the results are much better than C & C
initially anticipated4. The error in georeferencing of the postprocessed data with system is ±5 meters. In the early stages of
the AUV development, some at C & C suggesting developing
swath-editing tools allowing the data processor to average or
adjust the navigation data based on the alignment of seafloor
2
R. A. GEORGE, L. GEE, A. W. HILL, J. A. THOMSON, P. JEANJEAN
features which overlapped between adjacent swaths. This
concern was based on the fact that the multibeam datasets
would be extremely high in relative vertical resolution and any
mismatches due to positioning would be very apparent.
Fortunately, the quality of the post-processed inertial
navigation data is extremely accurate for the water depth the
AUV is deployed and little or no editing of the navigation data
is required. This accuracy in positioning makes the acquired
deepwater geophysical data very easy to process and interpret.
Being able to log AUV positions kilometers below the sea
surface at resolutions approaching surface GPS accuracy is
truly remarkable. Any geoscientist who has been assigned the
task of mapping the seabed with conventional deep-tow data
appreciates this technological advancement.
The AUV navigation data are processed and then merged
into the output formats of the acquired geophysical data. This
requires all sensor data time synchronized for correct
georeferencing. The standard deviation of the real-time
navigation is on the order of ±15 meters. The Inertial
Navigation System (INS) uses accelerometers as the primary
positioning system on the AUV. Position fixes from a
Kongsberg Simrad short-baseline acoustic system deployed on
the mothership minimizes positioning drift. A fiber optic gyro
also monitors heading and an acoustic Doppler profiler
provides speed over ground input. The post-processed
positioning solution is obtained utilizing a Kalman filter and
differentially weighted inputs from all the applicable sensors.
Multibeam Data Processing
The multibeam bathymetry data collected with the AUV allow
pipeline and facility engineers the opportunity to view large
areas of the deepwater seafloor at a level of detail never before
possible. The Kongsberg Simrad EM2000 multibeam system
operates at 200 kHz and collects data in a swath width of
about 220 meters (Figure 3). There are 111 beams or
individual soundings collected on each ping of the system.
Salinity and temperature measurements are sampled
continuously at the transducer face for correct beam forming.
An Octans compensator utilizes precision accelerometers to
record the heave, pitch and roll values of the vehicle. These
values are applied to the soundings and added to the values
from a deepwater, survey precision pressure sensor.
Multibeam data processing is performed utilizing
proprietary software. The multibeam soundings are processed
using binning algorithms. A 3-meter bin size is the standard
used for the AUV soundings. Typically, six or seven raw
soundings are recorded in the 3-meter bin. The processing
begins by conducting statistical analysis of the raw soundings
within the bins. Any bins with high standard deviations are
examined for noisy soundings, or outliers, and these points are
eliminated from further processing. The soundings are then
reduced using a median filter. The median sounding within
each 3-meter bin is used to produce a gridded dataset. The
gridded dataset contains points that are equally spaced with
OTC 14139
the water depth value for the grid bin calculated using a nearneighbor statistically weighted subroutine.
The gridded dataset is then used for geotiff and contour
generation. Triangulation of the dataset can be performed if
needed. Slope-gradient maps or images are easily generated
and very subtle seafloor features are accentuated on these
displays. Fledermaus 3D visualization software can be used to
view the multibeam data. The software allows the user to
quickly cut profiles and output the profile points for span
analysis by pipeline route engineers.
Side Scan Sonar Data Processing
Side scan sonar data in the 120 kHz frequency band are
collected aboard the AUV in raw Edgetech format and are
converted to XTF file format for viewing and interpretation
using a computer workstation. The sonar data are sampled
more than 2,000 times over the duration of the receive time.
In normal operation, the side scan sonar transmits about 3
times a second resulting in recording a per channel range of
238 meters (Figure 3). The sonar range can be set to different
intervals while being operated in a stand-alone mode. The
side scan sonar can be operated in a high-resolution 420 kHz
mode. The same navigation dataset used for the multibeam is
used to process the side scan sonar data.
Triton-Elics software is used for the playback,
interpretation and hardcopy generation of the side scan sonar
data. The software allows the interpreter to output ASCII or
DXF files for import into CAD mapping software. Mosaics
can also be constructed utilizing the program and output of the
sonar data in graphics TIF file format is available.
Traditionally, one of the biggest problems with producing
side scan sonar mosaics is the editing of the navigation data.
The AUV navigation data is processed and edited on the front
end, prior to being merged with the sonar data. This results in
the production of mosaics quickly with little or no time spent
on the editing of the navigation data. Ocean Imaging
Consultant’s (OIC) software is generally used to produce
mosaics with proper georeferencing and filtering. The
mosaics can then be used to drape over the 3D model of the
multibeam dataset for analysis in the Fledermaus software.
Subbottom Data Processing
The Edgetech “chirped” subbottom data are collected aboard
the AUV utilizing a frequency modulated seismic source in
the 2 to 8 kHz frequency band. The record time is limited to
about 300 milliseconds with time zero occurring at the altitude
of the AUV. This results in the recorded raw data being nontopographically corrected. The HUGIN depth information
must be input into the final output files in order to produce a
topographically corrected record. The survey precision depth
sensor information must be incorporated on a ping-by-ping
basis as the AUV is constantly changing depth to follow the
seabed terrain.
OTC 14139
HIGH-RESOLUTION AUV SURVEYS OF THE EASTERN SIGSBEE ESCARPMENT
XTF and SEG-Y file formats are two outputs available in
the processing of the seismic data. Triton-Elics software is
used to read the XTF files. This format allows for proper
referencing of the seismic data in both the vertical and
horizontal plane. These files are also constructed after the
navigation data are processed. X and Y data, AUV depth and
event marks are incorporated into the final output by using
time tags for each seismic shot. The SEG-Y file format
requires an integer millisecond value for the static offset of
each ping. This integer value requirement is not resolute
enough to properly reference the seismic data in the vertical
plane and results in a blocky presentation of the seismic data
in SEG-Y trace viewers. Seismic Micro Technologies worked
with C & C on utilizing one of the unused records of the trace
header for storing a number value resolute enough for static
offset of each seismic trace.
AUV Maneuverability
The ability of the AUV to maneuver without a tether results in
a drastic reduction of survey time and significantly increases
the quality of the remote sensing data. Conventional deep-tow
survey systems are difficult to tow along a preplotted course
due the distance between the towfish and the survey ship.
This distance can be more than 4 kilometers in water depths
greater than 1,500 meters. Course deviations made by the
survey vessel to alter the towfish course are not immediate and
crosscurrents may result in gaps in the survey coverage. The
AUV continuously receives feedback from navigation sensors
and can adjust the stern and rudder planes to quickly adjust the
attitude and course of the AUV.
The ability of the AUV to navigate curved lines results in a
drastic reduction of survey time. This ability is demonstrated
in Figure 4 where the company logo was written on the
seafloor by the AUV during a sea trial. The letters are actual
multibeam data produced and presented as a geotiff image.
The minimum turning radius for the AUV is 15 meters. The
ability of the AUV to navigate curves along proposed routes
can save days in survey time over deep-tow systems due to a
reduction in the number of line turns needed. When line turns
are necessitated, they are typically made in about 5 minutes.
Deep-tow system line turns can take hours due to the amount
of cable that has to be spooled up before the turn can
begin and then let out once the vessel is lined up on the
next trackline.
3
the equipment. The response of the towfish through cable
winching is not immediate and can take several minutes before
a significant change in towfish altitude is observed. Figures 5
and 6 are dip and strike lines across the Sigsbee Escarpment
and show the ability of the AUV to navigate effectively steep
slopes and rugose topography. Stern plane adjustments are
made on feedback received by the acoustic Doppler profiler
and these changes are nearly instantaneous. The AUV
maintains a relatively constant altitude of 40 meters, which
results in high quality side scan data being collected across
significant seafloor slopes.
The AUV maintains a constant speed approaching 4 knots
and this results in a very consistent dispersal of the remote
sensing data within the swath of survey coverage. Deeptowed towfish are subject to increases and decreases in speed
whenever cable is spooled in or out, which results in irregular
data densities in the alongtrack direction.
Real-Time Data Transfer
One of the technical challenges of using AUV technology is
how to transfer the data to the survey ship in order to make
routing decisions regarding the remote sensing data stored on
the AUV without retrieving the system. An acoustic modem
is used to accomplish this task using two discrete transmit
frequencies. The high frequency band of the acoustic modem
transmits the collected data from the AUV to the mothership
for periods of 30 seconds. The low frequency band is then
used for the next 10 seconds to transmit information from the
mothership to the AUV.
These transmissions include
information for control and proper operation of the AUV.
New mission plans or waypoints for “on-the-fly” course
changes can also be sent, but the bandwidth allowed for these
alter survey course points is less than 40 characters per 10second transmission. This bottleneck has created the need for
a unique binary survey command set to control the AUV.
The lack of a tow cable attached to the AUV results in data
collection that is virtually void of interference by weather.
The wave action affecting the surface towed vessel in a deeptow configuration is transmitted through the tow cable and
reduces the data quality.
The acoustically transmitted, decimated datasets of side
scan, subbottom and multibeam data allow the shipboard
geoscientists and engineers to make decisions regarding
routing alignments (Figure 7). The transmitted soundings are
dense enough to produce 5-meter binned datasets. Figure 8 is
a seafloor profile drawn across a trough feature from the realtime (5-meter bins) and post-processed (3-meter bins)
multibeam data. There is virtually no shift in the vertical
plane of the profiles and the horizontal shift is attributed to
improvement of the post-processed navigation over the realtime data. A profile generated across the feature from NOAA
Seabeam data is also shown. This graph shows the vast
improvement of AUV multibeam data compared to surface
towed multibeam data.
The AUV is free from the effects of winching that is used
to control the altitude of the towfish in deep-tow operations.
Deep-tow system operators are always concerned about
topography and usually fly the towfish higher than normal
across significant topography due to concerns for the safety of
3D Visualization
The development of the deepwater AUV with its highresolution multi-sensor package, in concert with accurate
navigation, has fundamentally changed our ability to map the
seafloor. The high-resolution coverage in deepwater of
4
R. A. GEORGE, L. GEE, A. W. HILL, J. A. THOMSON, P. JEANJEAN
relatively large areas of the seabed provides a new perspective
that has the potential to revolutionize our understanding of
seafloor processes and demands improved methods of
presentation for interpretation and analysis. Such a revolution
does not come without a price, however, and in this case the
price is one of data density. The massive amounts of digital
data collected by the sensors present tremendous challenges;
firstly in the individual sensor acquisition and processing and
then in terms of interaction, integration and interpretation. If
properly handled, however, the inherent density of the data
available from these systems also presents tremendous
opportunities5.
The human visual system has an enormous capacity for
receiving and interpreting data quickly and efficiently and
therefore must be an integral part of any effort to understand
complex data. The key is to be able to present the data in as
intuitive a fashion as possible, and the more intuitive the
presentation, the more rapidly data is interpreted, and the more
new information can be extracted from that data6. These
elements are incorporated in the Fledermaus interactive 3D
software application, and allow the integration and analysis of
the multi-sensor data sets from the AUV. Importantly, the
accurate navigation of the AUV permits these complex data
sets to be properly georeferenced in the 3D scene and
presented in a natural and intuitive manner that allows the
simple integration of multiple components without
compromise to the quantitative aspects of the data.
The software directly uses the C & C gridded data set in
generating the seabed model that has a color map assigned. A
lighting model is chosen including artificial sun-illumination,
shading and true shadow, and the scene is then rendered to
form a 3D image that is a natural and detailed view of the
seafloor morphology. These scenes are easily interpretable,
yet fully georeferenced and quantitative. All points are
georeferenced and can be interrogated in the 3D scene for
position, depth and any other attribute. Measurements can
be made and data sets profiled for interactive analyses
(Figure 10).
Color, while used to represent depth in the images above
can also be mapped to other parameters such as the side scan
sonar mosaic, and draped over the digital terrain model. The
software also allows subbottom data to imported as a SEG-Y
or image file and be co-located in the 3D scene as a vertical
curtain that follows the track of the AUV. Each of these data
is loaded at the best resolution that suits the particular data and
there is no need to resample any of the individual data sets or
compromise their quantitative value.
Another significant advantage of the AUV side scan and
subbottom data that is not available from normal towed
operations is that the position and orientation of the sonar and
profiler is known as accurately as the multibeam sonar. This
provides a superior result and allows for the first time these
types of data to be successfully integrated in the 3D scene for
OTC 14139
an intuitive and “real” image of the seafloor processes. The
user can interactively "fly" around the data and view it from
all angles and with special LCD glasses; the scene can be
viewed in true stereo.
The Fledermaus software was used throughout the BP
Gulf of Mexico surveys on a variety of computer platforms
from PC Laptops and SUN workstations, through to the BP
Highly Immersive Visualization Environments (HIVE) in
Houston for group analysis and review. 3D visualization
provides the ideal complement to the AUV that is almost
unconstrained in its surveying capability. It is also a
significant element of meeting the challenge of ever increasing
digital data volumes, and when integrated in the overall
process can produce value in areas such as efficiency,
accuracy, completeness, integration, and communication.
Visualization provides the complete picture of all the data
gathered during the survey or available from other sources,
and allows the interpreter to gain maximum value from seeing
the complete picture.
Survey Results
The AUV surveys conducted across the Sigsbee Escarpment
(Figure 9) produced the most extensive and detailed highresolution survey data obtainable to date. The area of
investigation encompasses approximately 147 square miles in
the southeastern portion of the Green Canyon Area about 120
miles south of Port Fourchon, Louisiana. Primary lines were
run with 200-meter primary line spacing and the tie lines were
spaced at 500 meters. The surveys were conducted at varying
times in the summer and fall of 2001.
Figure 10 is a Fledermaus image of the multibeam
bathymetry data collected along the Sigsbee Escarpment. The
data presented consists of a 3-meter binned dataset. The total
number of gridded soundings used to produce the 3D model is
44,080,895. The total number of raw soundings used in the
processing sequence is conservatively, 5 times the number of
gridded data points, or roughly 220 million points.
The Sigsbee Escarpment represents the seaward limit of
the salt province of the Gulf of Mexico. The intrusion of a salt
tongue has resulted in numerous seafloor faults in some
localities along the intrusion area. The Escarpment face is
characterized by numerous gullies or slumps that have resulted
from past sediment instability (Figure 11). The slump
deposits at the base of the Escarpment form aprons of
sediment consisting of displaced and mixed sediments of,
primarily, clay.
Mega-furrows were recently identified on deep-tow and
3D seismic surveys along the base of the Sigsbee
Escarpment7. Figures 12-14 show the character of these
features on the seafloor. The features identified along this
portion of the Escarpment are generally 1 to 3 meters in depth
and range from 5 to 50 meters in width. The features extend
for miles in some locations and are probably formed by helical
OTC 14139
HIGH-RESOLUTION AUV SURVEYS OF THE EASTERN SIGSBEE ESCARPMENT
flow of bottom currents.
The features represent an
engineering challenge for the flowline and pipeline
alignments. The opportunity offered by full digital integration
of these data for improved interpretation has been a long held
desire of the industry and specifically BP.
Conclusions
AUV technology has progressed from a research interest to a
commercially viable alternative for the collection of remote
sensing data in deepwater environments. Inertial navigation
has been proven as a successful means of positioning an AUV
in deepwater to accuracies that have never before been
achievable. The ability of the AUV to navigate curves and the
lack of a tether results in a significant savings in survey time.
Maintaining a relatively constant altitude over rugged
topography allows for the collection of high quality survey
data. High-resolution multibeam data allows route engineers
and geoscientists to view the deep-sea bottom at resolutions
needed for detailed engineering. Three-dimensional imaging
of multibeam data integrated with co-referenced sonar and
subbottom imagery on computer workstations provides
interpreters the opportunity to view and manipulate datasets
represented by millions of data points.
This allows
interpreters to better understand the seafloor morphology,
processes and to identify subtle seafloor features that may
otherwise go undetected. The results will allow project
engineers to plan appropriate engineering solutions in difficult
terrain, which, in turn, will provide greater operational and
environmental integrity.
Acknowledgments
The authors would like to thank BP Exploration and
Production Inc. for providing permission for the data examples
used in this paper.
References
1.
Northcutt, Jay G., Kleiner, Arthur A. and Thomas S. Chance.
OTC 12004 “A High-Resolution Survey AUV”.
Offshore
Technology Conference Proceedings, May 1-4, 2000.
2.
Kongsberg Simrad. “HUGIN 3000 Topside System Operator
Manual”. Kongsberg, Simrad, Horten, Norway, 2000.
3.
Hill, A.W. “The Use of Exploration 3D Data in Geohazard
Assessment:
Where Does the Future Lie?”.
Offshore
Technology Conference Proceedings, May 6-9, 1996.
4.
Jalving, B. and K. Gade. “Positioning Accuracy for the HUGIN
Seabed Surveying Untethered Underwater Vehicle”. Presented
at Oceans 98, September 1998, Nice, France.
5.
Mayer, L.A., Gardner, J.V., Paton, M., Gee, L. and C. Ware.
"Interactive 3D Visualization: a tool for seafloor navigation,
exploration and engineering". Presented at Oceans 2000,
September 11 – 14, 2000.
5
6.
Reed, B., Depner, J., Van Norden, M., Paton, M., Gee, L.,
Byrne, S., Parker J. and B. Smith. "Innovative partnerships for
ocean mapping: dealing with increasing data volumes and
decreasing resources". US Hydro 2001, May 22 - 24, 2001.
7.
Bryant, W., Bean, D., Slowey, N., Dellapenna, T. and E. Scott.
“Deepwater currents form mega-furrows near US Gulf’s Sigsbee
Escarpment”. Offshore Magazine, July, 2001.
6
R. A. GEORGE, L. GEE, A. W. HILL, J. A. THOMSON, P. JEANJEAN
OTC 14139
Figure 1 - HUGIN AUV on the sled of the launch and recovery system. The sled slides into a van where technicians service the
batteries. A high-speed network connection allows the onboard computers to interface with the shipboard workstations in order to
download data and upload new mission plans.
Figure 2 – Schematic of the HUGIN showing the major systems and components. The spherical payload and control processor
containers house computers that collect the remote-sensing data and control the operation of the AUV.
OTC 14139
HIGH-RESOLUTION AUV SURVEYS OF THE EASTERN SIGSBEE ESCARPMENT
Figure 3 – Sketch of AUV multibeam and side scan sonar swath coverage utilizing a 150-meter line spacing interval. This
line spacing is often used for the wing lines immediately adjacent to the centerline of the route alignment and allows the
seafloor directly beneath the pipeline to be inspected 3 times with the side scan sonar.
Figure 4 - An example of HUGIN’s line turn capability is
characterized in the above logo, which was mapped upon
the ocean floor in 1,500 meters of water during recent sea
trials aboard the R/V Rig Supporter. Line turns, which
take hours using deep-tow systems, are now
accomplished in less than five minutes with the AUV.
The detailed view of the “&” symbol to the left reveals
the character’s actual size. The height is approximately
1,800 meters, created with one multibeam bathymetry
swath of 220 meters. The ability to navigate curves
effectively decreases survey time dramatically by
eliminating the need for line turns.
7
8
R. A. GEORGE, L. GEE, A. W. HILL, J. A. THOMSON, P. JEANJEAN
1500 m
OTC 14139
150 m
308 Slope
Figure 5 – AUV high-resolution seismic profile across Sigsbee Escarpment. Water depth ranges from 1,375 meters to 2,100
meters. Greatest slope measured is 30 degrees updip of the slump unit. Automatic terrain tracking for AUV is set at 40
meters and fish height is never less than 25 meters. Vertical exaggeration is ~ 3.5 : 1.
200 m
1500 m
Figure 6 – AUV high-resolution profile along strike of Sigsbee Escarpment depicting the ability of the AUV to navigate
irregular topography. Slopes are greater than 408 in some locations. Vertical exaggeration is ~ 6:1.
OTC 14139
HIGH-RESOLUTION AUV SURVEYS OF THE EASTERN SIGSBEE ESCARPMENT
Figure 7 – Subbottom data example of real-time data display transmitted via acoustic modem showing debris
flow deposits. Vertical scale is in meters and horizontal distance across record is about 1 kilometer.
ROUTE PROFILES
NOAA
AUV REAL-TIME AUV POST-PROCESSED
Figure 8 – Graph of seafloor profiles across a depression feature in Gulf of Mexico. Red line profile represents real-time
multibeam data transmitted over the acoustic modem and processed at a 5-meter bin size. Blue line represents post-processed
bathymetry at a 3-meter bin size. The majority of the difference in the curves is positioning. The pink profile is generated
with NOAA Seabeam multibeam bathymetry data.
9
10
R. A. GEORGE, L. GEE, A. W. HILL, J. A. THOMSON, P. JEANJEAN
OTC 14139
Figure 9 - Regional map showing location of Sigsbee Escarpment AUV surveys. Bathymetry
presented from NOAA Seabeam data.
Figure 10 – Fledermaus 3D digital terrain model of the AUV multibeam data collected on the Eastern Sigsbee Escarpment. The
water depths range from about 1,250 to 2,800 meters. The rugged topography is the result of slumping and faulting.
OTC 14139
HIGH-RESOLUTION AUV SURVEYS OF THE EASTERN SIGSBEE ESCARPMENT
Figure 11 – Seafloor rendering of two distinctly different slumps on the Sigsbee Escarpment. Mound features in the sediment
apron of the toe are displaced sediment blocks.
Figure 12 – AUV bathymetry data showing the mega-furrow features found along base of Escarpment. The features are oriented
parallel to the strike of the Escarpment and are formed by bottom currents. The slump deposits impede mega-furrow
development. The features range in height from 1 to 3 meters and are 5 to 50 meters in width.
11
12
R. A. GEORGE, L. GEE, A. W. HILL, J. A. THOMSON, P. JEANJEAN
OTC 14139
10 meters
150 meters
Figure 13 – AUV subbottom record showing mega-furrows and slump deposits along base of Sigsbee Escarpment.
Figure 14 – Sonar record of mega-furrows. Dark returns represent the actual furrow area. Fix marks (white vertical lines) are 150
meters apart and sonar range is 238 meters/channel.