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Current Research Projects: 2002
New Community Infrasound Website
The new inframatics organization provides information about the use of
sub audible sound waves in the atmosphere for studying natural atmospheric
phenomena and monitoring anthropogenic sound sources including clandestine
nuclear tests. The main product of this organization's website is a
quarterly newsletter that includes articles summarizing ground breaking
research in low-frequency atmospheric acoustics.
IDA Global Seismographic Network
During the past year we have undertaken a major upgrading of the IDA stations at
the Cecil and Ida Green Pinon Flat Observatory and on Easter Island
with the latest instrumentation and real-time telemetry. Maintenance
expeditions to the IDA stations in Sri Lanka, Suleweisi, Indonesia,
South Georgia Island, Falklands, Fiji and Kwajelein kept the network
in top working order.
Recent upgrades of the telemetry links to some of the remotest stations
in the IDA network now brings continuous streams of IDA data to
IGPP from the stations in the Falkland Islands; Warramunga, Australia;
Borovoye, Kazakhstan; and Kurchatov, Kazakhstan. Of the 38 IDA stations, all
but four return a substantial portion of the data collected over
the Internet to computers at SIO. In addition to their scientific
value, telemetered data are used to monitor for clandestine nuclear
tests and for earthquakes that generate tsunamis. The IDA network
is the oldest, continuously operating seismic network in the world
- the first station was established in Canberra in 1974.
Anisotropy and Physics of the Pacific Lithosphere Experiment (APPLE)
Scripps scientists concluded data collection on a project to study the electrical conductivity
of the Pacific lithosphere from the uppermost crust to the lower
mantle. Carried out in collaboration with Southampton Oceanography
Centre, Flinders University, and the University of Adelaide, this
experiment involved the deployment and recovery of over 24 seafloor
electric and magnetic field recorders offshore San Diego from the
coast to 400 km into the ocean basin. Study of electrical anisotropy
will provide insight into the dynamics of crustal accretion at mid-ocean
ridges and the deformation associated with current motion of the
Pacific tectonic plate across the ductile mantle.
World's most extensive marine magnetotelluric survey carried out in the North Atlantic
As part of Scripps' industry/University collaboration in marine electrical methods,
in July/August 2001 a total of 119 deployments and recoveries of
SIO's marine magnetotelluric (MT) instruments were carried out in
the Faroes/Shetland basin, with an instrument recovery rate of 100%
and a data recovery rate of over 99%. The target of this survey
was the extent of potentially petroleum-bearing sediments beneath
the volcanic layers of the Faroes platform, difficult to image using
traditional seismic techniques because of the high acoustic contrast
between sediments and basalt. Although targeted primarily over two
recently released exploration blocks, a significant part of this
data set is being made available for a student's masters thesis
being carried out in collaboration with San Diego State University.
Marine electromagnetic methods developed by SIO map hydrocarbon deposits
After industry/SIO collaborative surveys carried out during November 2000, November
2001, and January 2002, it was announced in the March 2002 issue
of First Break, the monthly journal of the European Association
of Geophysicists and Engineers, that electromagnetic methods developed
at SIO can help discriminate between hydrocarbon bearing strata
and barren prospects. The controlled-source electromagnetic sounding
method, pioneered by Charles Cox in the 1980's, is particularly
sensitive to thin resistive layers buried beneath the ocean sediments.
This method is now being applied to determine if 'direct hydrocarbon
indicators' discovered using seismic methods are resistive, and
thus potentially hydrocarbon-bearing, or merely conductive acoustic
impedance contrasts devoid of economic value. With the cost of deepwater
exploration wells reaching $40M, electrical methods provide an economic
alternative to drilling.
Scripps' seafloor electromagnetic instrument fleet reaches 40 instruments
A tangible product of an aggressive collaboration between SIO and the offshore petroleum
industry is the expansion of Scripps' seafloor EM instrument fleet
from 9 veteran instruments to 40 devices by early 2002. The 31 new
instruments are state-of-the-art 24-bit data loggers capable of
recording up to four channels of electric and magnetic fields, with
over 600 deployments and recoveries logged to date. These instruments
are in service about half the time, carrying out a combination of
academic and industry projects.
Global Sea level
SIO scientist Walter Munk has re-examined the global sea level rise during the
20th century. Recent global compilation of temperature in the global
ocean is consistent with models of greenhouse atmospheric warming
and yields 5 cm in the second half century. Melting of the polar
ice sheets and glaciers is now estimated to yield 6 cm for the century.
Together these estimates accounts for only one half of the traditional
estimates of roughly 18 cm rise during the century. This leaves
an enigma.
Infrasound Arrays
SIO scientists have completed an infrasound array, consisting of 8 microbarometers
deployed in an area 2 km across, in the desert at IGPP's Cecil and
Ida Green Pinon Flat Observatory. The array passively records minor,
long-period variations in air-pressure that are caused by a wide
variety of sources including major storm activity over land or at
sea, large meteors, landslides, earthquakes, explosions, volcanic
eruptions, supersonic aircraft and rocket launches. The team is
completing a similar array in eastern Washington State. The arrays
are to be part of a global network of 60 arrays that is being constructed
to monitor for clandestine nuclear tests. The array at Pinon recently
made highly coherent recordings of an explosion which occurred ~1800
km to the southwest of the array. Infrasound and satellite data
indicate the yield of the explosion was ~8 kt (or equivalent to
16 million pounds of TNT). The source is believed to be a meteor
~4 m in diameter. Several stations in the international network,
including a station in Germany at a range of 11,000 km, recorded
the event. Infrasonic energy in the atmosphere will allow us to
study in more detail the many sources that give rise to the energy
and the manner in which the energy propagates through the turbulent
atmosphere.
Infrasound Noise Filters
A significant source of noise that complicates recordings of acoustic signals
from remote locations in the atmosphere is produced by atmospheric
turbulence near the recording array. SIO scientists have made significant
progress in their search for spatial filters that can be deployed
at the array sites to reduce unwanted noise while preserving the
signals of interest. One line of research has been directed at improving
existing filters currently in use in the global infrasound network.
Resonance inside filters currently in use has been found to severely
limit their effectiveness. The research conducted at SIO has produced
an inexpensive way modify the filters to remove this problem. SIO
scientists have developed an entirely new infrasound filter based
on fiber optics. Fiber optic cables are sensitive to pressure variations.
An array of cables distributed at ground level integrates pressure
variations at light-speed. Variations in pressure due to turbulence
occur at length scales less than the fiber-optic cables and are
averaged out of the data while long-period variations from remote
sources are retained.
New Visualization Center at Scripps
On March 4, 2002 the visualization center at Scripps Institution of Oceanography
(SIO) (http://siovizcenter.ucsd.edu)
opened its doors to a packed audience of media, industry and university
representatives to unveil the world's first visualization complex
dedicated to Earth and ocean sciences. This center immerses users
into a virtual world by projecting three-dimensional images onto
a curved, floor-to-ceiling screen (9x29) featuring 3.2 megapixel
resolution. Groups of up to sixty people can view these large-format
images at the same time. The workhorse of the system is a single
graphics pipe SGI Onyx 3400 that has a system bandwidth of 44 GBps
and is powered by 16 MIPS R12K processors and 16 GB of addressable
memory. This system can display multiple video input sources simultaneously.
The system is also equipped with technology that permits stereographic
3-D viewing of high-resolution images. Networking between the visualization
centers at SIO and San Diego State University (SDSU) allows groups
of researchers at both institutions to send and receive data and
images simultaneously and to collaborate on analyzing a multitude
of different data sets. Presently the network communicates at nearly
2.4 Gbps and by this summer the speed will increase to 10 Gbps allowing
full screen visualization communications including stereo visualization.
These systems allow users to combine and explore data and images
in innovative ways and are greatly enhancing scientists' ability
to visualize, understand, and collaborate on complex datasets. As
IGPP director John Orcutt states, "the Center takes our ability
to visualize and understand huge environmental and other datasets,
including large-scale computations to a new level."
ROADNet: Real-Time Observatories, Applications and Data management Network
The ROADNet
team's mission is "Bringing the Information Superhighway to
the Dirt Road and the High Seas. We have created new middleware
based on existing Object Ring Buffer and Storage Resource Broker
software at the Cecil & Ida Green Institute of Geophysics &
Planetary Physics (IGPP) and the San
Diego Supercomputer Center (SDSC) to provide end-to-end, real-time,
wireless network connectivity for arbitrary environmental data.
In addition, we are extending existing scientific wireless networks
through Orange County to Santa Barbara, to the Sierras, offshore
to moorings and over the high seas to ships operated by the Scripps
Institution of Oceanography. Finally, data delivered in real time
are being integrated in the new Visualization Center at Scripps
for scientific research, disaster mitigation and reaction, and education.
ROADNet is
sponsored by the NSF and supported by partnerships with the Scripps
Institution of Oceanography, IGPP, SDSC, the High Performance Wireless
Research and Education Network (HPWREN),
San Diego State University (SDSU),
the California Spatial Reference Center (CSRC),
and the California Institute for Telecommunications and Information
Technology [Cal-(IT)2]
at UCSD and UCI.
Ocean Bottom Seismograph Instrumentation Center (OBSIP)
The Scripps Institutional Instrument Center (IIC) at IGPP completed
60 new seafloor instruments this year and supported three major
field programs as part of OBSIP.
Other IIC's exist at Woods Hole and Lamont. The instruments are very
modern and include 24-bit analog to digital computers and record
hydrophones and 2-Hz vertical geophones. 24 instruments were used in
a cruise in the Atlantic in June to map upper mantle discontinuities,
5 instruments were recovered in the same month from Vailulu'u, the most
recent addition in the Samoan hotspot chain following a year's deployment,
43 were launched and recovered in the Indian Ocean in a study of the
structure of the continental margin of Australia in October/November,
and 53 were launched and recovered in the Marianas in March and April
of this year. The latter experiment set a record for number of ocean
bottom seismographs deployed and recovered on any cruise and completed a
circumnavigation of the globe in less than a year of use. We are testing
a new wideband seismometer to convert 25 of the existing instruments for
long-term recording of distant earthquakes. We will have a total of 80
instruments available by September when 75 ocean bottom seismographs will
go to sea for a study of the Gulf of California in Sept/Oct. Presently,
Scripps has the only center operating active instruments of this
description - the other instrument centers are nearly a year behind.
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