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Seaf loor Geodesy by the Year 2 0 0 0
A. N. Spiess
Scripps Institution of Oceanography
University of California, San Diego
LaJolla, California 92093
INTRODUCTION
Other papers in this group make it clear that high technology
geodesy, with particular relevance to geodynamic problems, is a well-
advanced maturing 'field of endeavor as applied to terrestrial
situations. Lasers,::satellites, high precision clocks,-advanced signal
processing and data reduction capabilities are moving us into second and
third generation versions of'~'systems brought to operation initially in
the 1970s. Unlike the~terrestrial situation, however, 'seafloor geodesy
in the geodynamic context still only consists of paper analyses,
'workshop reports, and the beginnings of testing of a few potential
system elements at sea. Nevertheless, the principal message of this
paper is that by the year 2000 we will be discussing at least a few real
multi-year data sets and using them to constrain our models of the
structure and dynamics of the crust beneath the sea - its genesis, its
evolution as it moves away from the mid-ocean ridges, its destruction in
the trenches, and the effects of its interaction with continents and
islands.
things:
If this prediction is to be realized, we need to achieve three
Development of some new elements of undersea technology.
2. Application of a variety of systems at a few interesting
initial sites.
3. Programmatic support frameworks for subsequent long periods
of observation.
This paper will discuss each of these three topics briefly in the order
listed.
TECHNOLOGY
A discussion of technology must start with some measurement goals.
Seafloor geodynamic problems are such that first generation systems
would be useful if they could produce accuracies of a few centimeters
for measurements of horizontal or vertical position change, strain
measurements of a few parts in a million, and tilt determinations in the
100
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101
range-of a few microradians. Beyond that, whatever means are used to
make these measurements must be compatible with the seafloor environment
and capable to being used to monitor changes over periods of many years.
An encouraging aspect of the technological problem is that a large
number of options are potentially available. Some of these involve the
possibility of fairly direct transfer of well-established land
techniques, while others are derived from undersea developments related
to other goals.
At least five differences between subaerial and subsea circumstances
drive the design and development of seafloor geodetic systems (NAS,
1983~:
Electromagnetic radiation at frequencies high enough to be
"useful is highly absorbed in the sea because of the
electrical conductivity of seawater. The only useful range
is the optical one, but even there, one's capabilities are
limited to tens, or perhaps a few hundred meters.
2. Acoustic energy of appropriate wavelength can be
transmitted effectively over distances of many kilometers.
3. Ambient pressure at the seafloor is not only large, it is
relatively free of large amplitude short wavelength or
short time scale irregularities.
4. The seafloor environment is quite stable in terms of
temperature and sediment water content.
5. Access to the seafloor is much more difficult than for most
terrestrial sites.
These considerations lead to some immediate conclusions about the
most fruitful directions that system developments are likely to take.
First, acoustic systems will dominate for measurement of horizontal or
slanting distance measurements involving distances of more than about
100 m. At the same time, shorter range systems now in use on land, but
that suffer from environmentally induced monument motion problems should
behave better in the deep sea. Finally, one must strive for simplicity
in system installation and maintenance.
The techniques that should be most readily transferred from the land
are those that operate effectively over rather short distances.
Mechanical or laser strain measuring systems, as well as both short and
long baseline tiltmeters (Agnew, 1987) also fall in this category. They
will benefit from having substantially reduced "noise" due to monument
instabilities. Some of them, however, introduce collateral requirements
for substantial power and for continuity of operation. They also
introduce challenging installation problems, as will be discussed below.
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Laser ranging through seawater (as opposed to systems in which the
path is contained in a pipe or optical transmission fiber) would be
limited to ranges of at most a few hundred meters by the attenuation of
light in seawater - about 200 decibels per kilometer in clear water.
Speed of propagation of light in seawater is only known to about a part
in 104. The change of speed with temperature and salinity (Stanley,
1971) is small, however; thus, as long as the laser power levels are
modest enough that they do not create appreciable localized temperature
increases, they can be useful in detecting path length changes with
time. The localized heating problem prevents one from overpowering the
high attentuation by brute force introduction of massive transmitted
power.
Borehole oriented approaches using strain or tilt measuring devices
installed in deep-sea drilling program holes should have no problem.
Similarly, well-logging methods used to detect changes in the cross-
sectional shapes of holes or to document orientation of breakouts in
order to infer the nature of stresses in the uppermost parts of the
crust should operate as well at sea as on land once there are
established systems for doing wireline re-entry into deep-sea drill
holes (Langseth & Spiess, 1987~.
One new class of systems would involve the use of pressure
measurements to determine the distance of the seafloor below the sea
surface. With present state of the art in measurement of temperature
and salinity as a function of depth, and knowledge of how to convert
these measurements to water density (Saunders, 1981), one should be able
to convert pressure measurements to depths with accuracy of a part in
105 (Reid, 1984~. Quartz crystal pressure gauges offer the best
possibility as far as accuracy is concerned (Irish and Snodgrass, 1971),
although these come in a variety of configurations, some of which
actually utilize mechanical elements (e.g., Bourdon tubes and bellows)
as intermediate links and thus suffer from drift problems that degrade
their performance in this context (Watts and Kontoyiannis, 1986; Wearn &
Larson, 1984; Busse, 19879.
The major new class of systems entering geodesy are those utilizing
underwater sound transmission. They are based on over 50 years of ocean
acoustics research and development (primarily oriented toward submarine
detection) (Eckart, 1968; Urick, 1975) but with a long history of
application in marine geology and geophysics (Spiels, 1987~. Early
discussion of their usefulness in geodesy occurred at a symposium in
1966 (Speiss, 1966), although at that time the goals set were not as
stringent as those being discussed here.
The principal limitation on use of sound propagation through
seawater for distance measurement is our ability to know the velocity
with which to convert travel time to distance. In this, one has a
choice between using a direct measuring sound velocity meter or
measuring pressure, temperature and salinity and converting these, via
empirical relationships based on laboratory data into sound velocity.
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103
At the present time the latter approach is only good to a few parts in
105 (Lovett, 1978~. The direct measurement method relies on the fact
that, even for geodetic purposes, sound propagation in seawater is
essentially non-dispersive (Urick, 1975~. One can thus use a small,
dimensionally stable device, operating in the megahertz frequency range,
to measure travel times, calibrate it in pure water (for which the
relationship between pressure, temperature, and sound speed are known to
a part in 106 (Greenspan, 19721), and use the resulting velocity
determination for systems operating as low as 10 kHz. The best such
meter devised to date had its motivation in geodetic application and is
capable of a little better than a part in 105 (McIntyre and Boegeman,
1986). Clearly, there is room for technological improvement in this
area.
The limit on sound velocity measurement capability translates
directly into a distance measuring accuracy limit of the same amount, 1
in 105. This breaks down at the short range end at distances of only a
few meters, at which there is difficulty in determining the locations of
the acoustic centers of the transducers. At the long range end it
simply does not meet our goal of a maximum of a few centimeters
uncertainty beyond about 10 km. There is, however, a fundamental
environmental constraint. Since the sound velocity field must be
determined experimentally by moving one, or perhaps a few j point
measuring instruments through it, there can be dynamic situations in
which the spatial variations of water temperature and salinity can vary
rapidly enough with time that the sound velocity averaged over long
travel paths may not, in a practical sense, be knowable to the same
accuracy as the individual measurements. Particularly in shallow
coastal waters the effective accuracy may not be better than a part in
103, while in the open ocean, paths including near surface water may
only be good to a part in 104. Good understanding of the local physical
oceanography, leading to proper distribution of measurements and
averaging can probably make some improvement on these numbers. Near-
bottom deep water may often show microstructure at the level of a part
in 105 (Spiels, 19809. In any event, every site at which acoustic
measurements are made must include, at the same time, a determination of
the sound velocity structure, including some evaluation of the magnitude
and time scales of its variability.
One other aspect of the environment arises because water motion
velocities are not usually negligible compared with the velocity of
sound (1500 m/sec). For accuracies of a part in 105 one must know the
along track component of water velocity to 1.5 cm/see (0.03 knot). In
this case, it is thus preferable to measure round trip travel time by
using reflectors or echo repeaters, since, under those conditions, the
ratio of water velocity to propagation velocity only enters as its
square, and all realistic deep ocean currents become negligible (NAS,
1983).
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Acoustic systems take on three forms, depending on the path lengths
over which one works. For distances of a few hundred meters one should
be able to achieve a part in 105 (few mm) accuracy using direct two-way
transmission between fixed bottom units by operating in the 100 kHz (15
mm wavelength) regime. Over such short ranges it should be possible to
have very good knowledge of the sound velocity structure along the path
as well.
As path lengths approach a kilometer or more one is forced to
somewhat lower frequencies by the fact that attenuation is less (Fisher
and Simmons, 19779. One is also forced to abandon the direct path
approach because, in nearly isothermal water (typical of deeper
situations) the sound velocity increases with depth because of
increasing pressure. Under these circumstances sound rays curve upward
(Spiels, 1966) and, unless one places the acoustic elements on towers
(with the added complexity of having to account for tower tilt), no
direct path between transponders will exist. Under these circumstances
an intermediate, near-bottom towed vehicle can be used to range
simultaneously on three or more transponders from many different
locations in the area being surveyed. A large number of observations
are then used to determine the internal geometry of the transponder
array, with the advantage of averaging over acoustic paths traversing
differing portions of the area and thus averaging over the time-varying
aspects of the sound velocity field. Computer simulations of this type
of system, using sets of 300 observations distributed through a four
transponder array having a 2 km radius resulted in baseline length
errors of 1 to 2 cm-when errors having a Gaussian distribution with 10
cm standard deviation were inserted into the range data (Spiels, 1985a).
The third type of acoustic system under development is designed to
relate points on the seafloor to vehicles at the sea surface, with the
goal of tying from the surface vehicle to points on land using GPS
technology. Composite systems of this kind will support determination
of baselines of lengths of hundreds of km,;and first generation versions
are expected to have uncertainties of the order of a few cm (Spiels,
1985b).
The difficulty of making the surface-to-bottom tie is that it must
encompass the more rapidly changing complex uppermost layers of the
ocean. As pointed out initially by Bender (1982), this effect can be
mitigated if one uses a set of three seafloor transponders and operates
chose to the point for which all three travel times are equal. Under
these conditions the uncertainty due to lack of knowledge of the sound
velocity is proportional to the distance one is away from the central
point (Spiels, 1985b). For example? if one can operate within 100 m of
the center, one only needs the sound velocity to within a part in 104 to
achieve centimeter accuracy. This simple picture is degraded by the
existence of horizontal gradients of sound velocity across the region
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105
traversed by the sound paths. Fortunately, the only oceanographic
effects that can produce gradients large enough to create problems in
the open sea (away from major fronts) are those associated with the
higher frequency internal waves (periods of tens of minutes to a few
hours),-and these can be reduced by averaging over periods of a day or
so .
Conventional commercially available transponders capable of
operating over km ranges operate by having a circuit that recognizes an
incoming pulse and then transmits a pulse at some other frequency. This
process, for systems operating in the 5 to 20 kHz regime, introduces
timing uncertainties equivalent to a meter or more uncertainty in range
(NAS, 1983~. A method for overcoming this problem is to use some
version of a signal re-transmitting system such that the phase
relationships are maintained between the incoming and outgoing signals.
One method that has been developed to implement such a system has been
to build a transponder that contains a digital shift register delay line
having a number of microsecond steps capable of holding several
milliseconds of signal. A spread spectrum coded timing signal is then
transmitted with the transponder interrogation. The transponder
continuously digitizes the incoming acoustic energy and puts the samples
into the delay line. Upon recognition of the interrogation, the
transponder shifts from listening to transmitting and sends out the
contents of the delay line. The outgoing acoustic waveform thus is
delayed by an amount known to within a microsecond and the returning
signal retains its phase relationship with the original signal (Spiess
et al., 1980~. Transponders of this type have been built and tested at
sea in March of 1988, showing timing uncertainties having an individual
pulse standard deviation of 10 psec, corresponding to ranging
uncertainties of less than 1 cm.
All of the various systems described or implied above have a common
need with respect to capabilities of installing, tending, and removing
complex equipment in the deep ocean. Such capabilities start with
requirements on ships that must support any on-site activity, as well as
transporting the necessary people and equipment to the area. These
functions have been recognized and included among the ship performance
requirements developed by the ocean science community through studies
and committees, particularly those sponsored through UNOLS (University
National Ocean Laboratory System)(UNOLS, 1986~. Characteristics of
particular importance in this context include good seakeeping, transfer
of cumbersome heavy loads from the ship to the seafloor, adequate on-
board storage space, and dynamic positioning. No individual ships in
our present academic ocean research fleet meet all of these
requirements, although two of them (Knorr and Melville) are scheduled
for major upgrading during the coming year that will put them close to
being adequate for these purposes. Beyond that, one new ship is
programmed for construction starting this year with Navy funding and a
second is in the preliminary design phase with NSF support.
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Four types of systems are in various stages of development relative
to performing the kinds of tasks involved in setting up and maintaining
seafloor geodetic devices on the deep seafloor: manned submersibles,
tethered neutrally buoyant swimming vehicles (conventional Remote
Operated Vehicles - ROV's), cable supported dynamically positioned
devices, and seafloor supported manipulative systems (tractors, etc.~.
The only one of the four for which there is substantial deep-sea
operating experience is the manned submersible category. Alvin,
operated for the research community by Woods Hole Oceanographic
Institution (WHOI) has been used for many years to carry out
manipulative tasks, primarily in the contexts of marine geology and
benthic biology (particularly hydrothermal vent-related experiments).
The French submersible Nautile has recently been used to position a
nearly neutrally buoyant winch assembly in a deep-sea drilling program
borehole re-entry cone (Langseth and Spiess, 1987~. These craft have
the advantage of a man actually on the site, although that often is a
disadvantage in that safety consideration places substantial limits on
the kinds of objects one is willing to handle. Since these craft
operate at close to neutral buoyancy, they have limited load handling
capabilities. Overall, they can carry out some of the necessary tasks,
but their deployment and safety considerations limit their usefulness.
ROY's have been in use in shallow water for many years, particularly
as complements to diving operations in offshore oil and gas field
development. These systems rely primarily on small, nearly neutrally
buoyant vehicles positioned in the water by vertical and horizontal
thrust propeller systems (Wernli, 1984~. They have proven quite useful
for both observation and manipulation. Since the actual work vehicle is
coupled by a neutrally buoyant wire to the ship or to an intermediate,
cable supported "garage", these units are fairly effectively decoupled
from the heaving motions of their surface support ship. Thus, they
trade stability for load handling capability. Two such systems are
emerging for deep water use by the ocean science community. One of
these is the Argo-Jason system, (Ballard, 1982; Yoerger and Harris,
1986) under development at WHOI, with the- other built by ISE (Langseth
and Spiess, 1987) to support Canadian research efforts. Both of these
are pushing a major technological advance - the use of fiber optic
information transmission links built into the long main strain cables
that support the ''garage" unit from which the neutrally buoyant work
vehicle operates. The high data rates expected from these telemetry
systems will allow operation of full bandwidth television systems for
viewing the vehicle's surroundings and the tasks they are carrying out.
Cable supported dynamically positioned systems have the capability
of working with heavier loads albeit without as effective decoupling
from the motion of the surface suspension point as the conventional
ROV's. One system of this type has moved into operating condition for
ocean research in the past year, developed with NSF support at Scripps
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Institution of Oceanography (SIO). Its primary function is to place
instruments accurately on the seafloor (including into drill holes) and
either monitor their outputs (providing a telemetry link to the
supporting surface ship) or release then for later recall or recovery.
This device, being directly cable supported, can carry loads in excess
of 1000 kg negative buoyancy (Spiess et al., 1987~.
The fourth category - bottom-supported manipulative devices - seem best
adapted to many of the tasks envisioned in the implementation of
seafloor geodetic observations. Resting on the seafloor, such devices,
although cable connected to a surface ship for power and control, can be
almost completely decoupled from ship motion. At the same time they are
able to manipulate heavy objects or carry out fine scale assembly
operations using their reaction against the (relatively) solid seafloor.
One device of this type is emerging from the development stage at SIO-
RUM III (Anderson and Horn, 1984) is scheduled to carry out its first
deep-sea tasks this summer, installing precision transponder mounts and
seafloor hydrophore assemblies in basins off southern California.
Summarizing the technological situation, it appears that both a wide
range of instruments, and the capabilities for installing and monitoring
them, could be available for conduct of deep seafloor geodetic
observations within the next year or two.
INITIAL OPERATIONS
Initial use of systems of these kinds present two requirements.
They should address interesting geodynamic problems, and they should be
at sites conveniently located relative to operating bases so that it is
easy to make frequent visits to carry out developmental, as well as
routine observational functions. As new terrestrial geodetic systems
evolved, the tectonically active southern and central California areas
provided an appropriate laboratory region meeting these requirements.
Our present understanding (Minster and Jordan, 1984) implies that the
offshore regions adjacent to the southern California coast are equally
interesting and appropriate. It is clear that there are localized areas
of tectonic activity in the Continental Borderland, and that, in order
to understand fully the present day dynamics of the North
American/Pacific Plate boundary, we must have deep ocean reference
points beyond the Channel Islands.
Localized networks utilizing seafloor strain measurements and short
range direct path acoustic systems could have their initial trials
within the borderland itself. Some sites should be shallow enough that
decreasing temperature with depth would counter increasing pressure to
produce sound velocity gradients leading to downward, rather than
upward, refraction. This would in turn allow fairly useful ranges for
direct linkages between near-bottom points. In these regions, however,
there would have to be intensive measurement of sound velocity to cope
with changing oceanographic conditions.
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Composite GPS/acoustic systems would play a most significant role by
establishing reference points in the deep ocean, not only off the
southern California borderland, but off the central California coast as
well. Ties between these points and the well-established VLBI sites in
northeastern California (e.g., Owens Valley) and in Arizona (Yuma) would
provide the necessary constraints on the contemporary total motion
between the Pacific and North American plates, as well as satisfying the
requirements of being available for re-occupation with minimal ship
operating cost.
For many of the approaches mentioned in the previous section, the
most exciting and fruitful zones for initial application would be at the
crests of the mid-ocean ridges and rises (NRC, 19889. Geodetic
measurements of all kinds would provide very useful constraints on
models of lithosphere formation, volcanic activity and hydrothermal
circulation. The most logistically convenient, well-studied site for
initial implementation of such studies would be on the East Pacific Rise
at 21° north latitude (Normark, 1980; RISE Group, 1980~. That location
is, however, within waters controlled by Mexico and there have
occasionally been delays in obtaining clearances to re-occupy the site.
it may be possible to generate a continuous program there, similar to
those set up on land by the seismologists, by helping develop Mexican
scientific community interest in seafloor geodesy. The other two
immediate choices are the Juan de Fuca spreading axis off the Canadian
and northwestern U.S. coast and the East Pacific Rise at 13° N. If it
were not for a restrictive weather window, the Juan de Fuca site would
be a very desirable one; however, operations there with our normal
research ships in support of development of new approaches would be
limited to the summer months with resulting constraints on coordinating
ship schedules with other research activities. The 13° N site's
disadvantage is its distance (about 1500 miles) from the nearest major
oceanographic research ship operating base. Other than that, it is an
attractive location since it has a stretch of well-developed simple
structure including hydrothermal activity, but with examples of
overlapping rift zone features (Sempere, 1986) nearby. The pros and
cons of these locations will be debated over the coming year and,
hopefully, the beginnings of geodetic site occupations will take place
early in the 1990s.
PROGRAMMATIC CONSIDERATIONS
Successful geodetic programs have one essential requirement - a
long-term commitment by the participants - both individual leaders and,
even more important, sponsoring agencies. In the U.S. the two groups
that have maintained -the necessary commitment over the years on land
have been the U.S. Geological Survey and the National Geodetic Survey
(surviving the multi-step transformation into a NOAA element from the
Coast and Geodetic Survey). Neither of these groups has been
particularly aggressive in attempting to develop an oceanic capability.
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This lack of push probably arises because applications of marine geodesy
do not fit logically into their missions as developed in the terrestrial
environment. The one exception is in the USGS mission of understanding
earthquake phenomena. Here, there would be clear gains in having
reference points on the oceanic side of the San Andreas complex, but
even more exciting is the prospect of being able to measure convergence
across the Aleutian Trench or uplift along the Vancouver
Island/Washington continental slopes.
The only agency that has shown consistent support for development of
oceanic capabilities has been the NASA Geodynamics program. It
recognized a number of years ago (Walter, 1983) that space-based
techniques (particularly GPS) could have a more nearly global capability
if it were possible to make ties from continental sites into ocean
areas. This extension has largely taken place by occupation of island
locations. While these are particularly convenient for VLBI and
satellite laser ranging operations, the program also recognized the
desirability of being able to establish reference points in important
places where no islands were available, most obviously on the seaward
flanks of the major trenches on the ocean margins. It is hoped that
this program will continue, at least to a point at which USGS and/or
NOAA will pick up the challenge.
The other logical agency that might support oceanic geodetic
activity is the National Science Foundation. Geodesy in general has had
scant support from that quarter, in part because geodetic impacts on
basic earth sciences have not been well established until rather
recently. The gradual development of our awareness of the many facets
of plate tectonics, and the fact that nearly all plate boundaries lie in
the ocean, give considerable emphasis to the desirability of including
research in ocean floor geodesy within the NSF Ocean Sciences purview.
A problem in this is that, while de facto NSF provides continuous
support for various aspects of ocean science, the general pattern for
administering its ocean floor research grants (except deep-sea drilling)
has been based on short-term commitments. This pattern is, however,
being somewhat altered and some portion of its new initiatives are
targeted for coordinated research activities focused on longer term
goals. Within this context, the RIDGE initiative (NRC, 1988) does
provide a logical context for ocean geodesy as a part of ocean science
research.
CONCLUS ION AND ACKNOWLEDGEMENTS
Although there are many steps yet to be taken along the way, it
appears that, by the year 2000, there may very well be the technology
and the programmatic commitment for significant seafloor geodetic
activities. The research and application opportunities are there both
in relation to our basic understanding of the crust of the earth beneath
the sea, and the context of related impact on man's activities.
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llQ
The technology discussed in Section II is quite diverse and its
development has been carried out by a larger number of contributors than
even the list of references implies. Ihe authors geodedy-oriented
activities have been supported primarily by NASA, but with small inputs
from the Office of Naval Research, NQAA, and NSF.
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REFERENCES
Agnew, D. C., Continuous Measurement of Crustal Deformation, in Methods
of Experimental Physics, edited by C. G. Sammis and T. L. Henyey,
Vol. 24, Part B. Geophysics: Field Measurements, pp. 409-435,
Academic Press, 1987.
Anderson, V. C., and R. C. Horn, Remote Underwater Manipulator: RUM
III, Trans. Soc. Automotive Engineers, San Diego, 1984.
Ballard, R. D., Argo and Jason, Oceanus, 25, 30-35, 1982.
Bender, P. L., National Bureau of Standards, University of Colorado,
Boulder, personal communication, 1982.
Busse D. W. Quartz Transducers for Precision Under Pressure
, , ,
Mechanical Engineering, 109, No. 5, 1987.
Eckart C. Principles and Applications of Underwater Sound Reprinted
, , ,
by Dept. of the Navy, Headquarters Naval Materiel Command,
Washington, D. C., 1968.
Fisher, F. H., and V. F. Simmons, Sound Absorption in Sea Water, Acoust.
Soc. Am. 62(3), 558-564, 1977.
Greenspan, M., Acoustic Properties of Liquids, in American Institute of
Physics Handbook, McGraw-Hill, New York, 1972.
Irish, J. D., and F. E. Snodgrass, Instruments and Methods - Quartz
Crystals as Multipurpose Oceanographic Sensors - I Pressure Deep
Sea Research, 165-169, 1971.
Langseth, M. G., and F. N. Spiess, Science Opportunities Created by
Wireline Re-Entry of Deep-Sea Boreholes, Workshop held at Scripps
Institution of Oceanography, 23-24 February 1987, Joint
Oceanographic Institutions as part of the U.S. Science Support
Program for the Ocean Drilling Program, 1987.
Lovett, J. R., Merged Seawater Sound-Speed Equations, J. Acoust. Soc.
Amer., 63, 1713, 1978.
McIntyre M. and D. E. Boegeman A New Sound Velocity Measurement
, , ,
System, Proceedings of Intl. Symposium on Marine Positioning,
Reston, Virginia, 1986.
Minster, J. B., and T. H. Jordan, Vector Constraints on Quaternary
Deformation of the Western United States East and West of the San
Andreas Fault in Tectonics and Sedimentation Along the California
Margin edited by J. K. Crouch and S. B. Bachman, p. 187, Pacific
Section of Soc. of Economic Paleontology and Mineralogy, 1984.
OCR for page 112
112
NAS Committee on Geodesy, Seafloor Referenced Positioning: Needs and
Opportunities, Panel on Ocean Bottom Positioning of the National
Research Council's Committee on Geodesy, National Academy Press,
Washington, D. C., 1983.
NRC, The Mid-Ocean Ridge: A Dynamic Global System, p. 352, National
Academic Press, Washington, D. C., 1988.
Normark, W. R., Definition of the Plate Boundary Along the East Pacific
Rise Off Mexico Marine Geodesy 4 29-43 1980.
- ? ? ? ~
Reid, J. L., personal communication, 1984.
RISE Group, East Pacific Rise: Hot Springs and Geophysical Experiments,
Science, 207, 1421-1433, 1980.
Saunders P M Practical Conversion of Pressure to Depth Amer.
, · · . .
Meteorological Soc., 11, 573-574, 1981.
Sempere, J., Occurrence and Evolution of Overlapping Spreading Centers,
Ph.D. Thesis, University of California, Santa Barbara, CA, p. 227,
1986.
Spiess, F. N. Underwater Acoustic Positioning: Applications,
Proceedings of the 1st Marine Geodesy Symposium, 93-101, 1966.
Spiess, F. N., Acoustic Techniques for Marine Geodesy, Marine Geodesy,
3~1), 13-27, Crane, Russak & Co., Inc., New York, 1980.
Spiess, F. N., C. D. Lowenstein, D. E. Boegeman, and F. V. Pavlicek,
Precision Transponder and Method for Communication Therewith, U.S.
Patent 4,214,314, 1980.
Spiess, F. N., Analysis of a Possible Sea Floor Strain Measurement
System, Marine Geodesy, 9~4), 385-398, 1985a.
Spiess, F. N., Suboceanic Geodetic Measurements, IEEE Trans. on
Geoscience and Remote Sensing, GE-234, 502-510, 1985b.
Spiess, F. N., J. A. Hildebrand,
Seafloor Studies, EOS, 1335, 1987.
and D. E. Boegeman, ~_~ Ss~s ~=s Or
Stanley, E. M., The Refraction Index of Seawater as a Function of
Temperature Pressure and Two Wavelengths, Deep-Sea Research, 1848),
833-840, 1971.
UNOLS Fleet Replacement Committee, Science Mission Requirements for New
Oceanographic Research Ships, 1986.
Urick, R. J., Principles of Underwater Sound, McGraw Hill, New York,
N. Y., 1975.
OCR for page 113
113
Walter. L. S
.,
Geodynamics, NASA Conference Publication 2325
,
1983
Watts, D. R., and H. Kontoyiannis, Deep-Ocean Bottom Pressure and
Temperature Sensors Report: Methods and Data, University
Island, Graduate School of Oceanography,
Technical Report Number 86-8, 1986.
of Rhode
Narragansett, R. I., GSO
Wearn, Jr., R. B., and N. G. Larson, Measurements of the_Sensitivities
and Drift of Digiquartz Pressure Sensors, Deep-Sea Research, 29,
No. 1, 111-134, 1984.
Wernli, R. L., Operational Guidelines for Remotely Operated Vehicles,
p. 200, Marine Tech. Soc., 1984.
Yoerger, D., and S. E. Harris, Argo Jason:
Exploration of_the Sea Floor, AWES, 1986
-
Integrated Capabilities for
.
Representative terms from entire chapter:
marine geodesy
