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Earthquakes and Geology
The Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics Scientists in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics
(Green IGPP) at Scripps conduct numerous studies of Earth, including
its oceans, as well as other planets. Green IGPP researchers operate
the global IDA Seismic Network and a geophysical observatory near Palm
Springs. Green IGPP studies include using Global Positioning System
(GPS) receiving stations to monitor the Dead Sea fault in Israel and
devising strategies to protect Venice, Italy, from encroaching seawater.
Earthquake Forecasting and Response
Scripps has a network of GPS receiving stations placed throughout southern
California to study movements of the earth's crust down to less than
1/20 of an inch. Using continuous measurements of the positions of the
stations, Scripps researchers can rapidly determine which parts of
southern California are actively changing. These data help scientists
understand why earthquakes occur and where they are most likely to
strike. Immediately following an earthquake, they can use these data to
pinpoint the most devastated areas, thus aiding emergency management
and repair teams.
Faults Discovered Underneath Metropolitan Los Angeles
Scripps researchers and their colleagues conducted extensive seismological
research that recently led to the discovery of blind thrust faults
underneath downtown Los Angeles. These faults, capable of producing a
devastating earthquake, pose a more serious threat to Los Angeles than
the more famous and much larger San Andreas Fault. Although scientists
have long thought the faults existed, the researchers provided the
first solid proof by analyzing new seismic maps.
Mapping the Seafloor with Satellites
Scientists at Scripps and the National Oceanic and Atmospheric Administration (NOAA) have developed the first digital map of the global seafloor.
Before its release, scientists had better maps of the surface of Venus
and Mars than of Earth's ocean bottom. Conventional seafloor mapping,
using echo-sounding data from ships, has been difficult because of the
large gaps between surveys in remote areas. By combining depth
soundings from ships and gravity data from satellites, the new map is
creating opportunities in underwater exploration, including searching
for untapped petroleum reserves, identifying previously unknown
volcanoes, and studying the tectonic history of the oceans. The map
also is used in a three-dimensional video display at the Rose Center
Planetarium of the American Museum of Natural History in New York City.
New Earthquake Mapping
Using satellite technology and radar images, scientists at Scripps produced near real-time images
of a magnitude 7.1 earthquake near Twentynine Palms, California.
Scientists used maps of ground displacement to measure the offset along
the main rupture and to monitor the continued slow sliding of the fault
after the earthquake. Field geologists used the deformation maps to
search for minor slippage on nearby faults. While such maps typically
take weeks or months to compile following a quake, the Scripps data
were collected directly from a satellite as it passed over southern
California about three days after the Hector Mine earthquake in 1999.
Immediate field mapping is important because tiny surface fractures
will degrade after just one rainstorm. With practice, the turnaround
time could come down to about four hours, even closer to real-time
capability.
Peering into the Volcano
Scientists at Scripps have for the first time produced a direct three-dimensional
image of a volcanic system. Previous textbook depictions of the fiery
magma chambers that reside beneath volcanoes were based on projected
measurements, some guesswork, and an artist's creative imagination. An
international research team that included Scripps scientists used a
two-mile-long array of hydrophones instruments used for listening to
sound transmitted through water to record sound signals reflected from
a magma chamber residing one mile beneath the East Pacific Rise, a
linear volcanic system some 600 miles southwest of Acapulco, Mexico.
Such images should provide new insights into the geological processes
of volcanic systems worldwide and the composition of erupted lava
flows.
Project IDA: Monitoring Earthquakes and Nuclear Weapons TestsProject IDA,
managed by Scripps researchers, consists of 40 seismic stations around
the globe. Scripps seismologists study how and why earthquakes occur
and how they relate to the formation of continents and ocean floors,
volcanic eruptions, and tsunamis, the "tidal waves" caused by undersea
seismic disturbances. Scientists at the Green IGPP depend on
information systems such as Project IDA, a global seismographic network
begun in the mid-1970s, to monitor seismic activity produced by
earthquakes and underground nuclear tests. A Project IDA station was
close to the recent Indian nuclear test and provided the strongest and
clearest data.
Plate Tectonics Puzzle Solved
A scientific team led by Scripps researchers has located the missing
geological piece in the puzzle of plate tectonics in the southwest
Pacific Ocean. The team found that east and west Antarctica started to
spread apart about 43 million years ago and then abruptly stopped 17
million years later, after the rift between them had opened about 180
kilometers (about 112 miles). Plate movements in the region of the Ross
Sea and the west Antarctic rift system had remained a mystery for more
than a quarter century. The inclusion of this east west Antarctic
motion explains a gap between the Pacific and Australian plates.
Seafloor Observatories
Scientists at Scripps, Woods Hole Oceanographic Institution, and the University of
Washington are designing a global network of fixed ocean observatories
for measurements of the solid earth, the oceans, and atmosphere.
Scripps and Woods Hole scientists have designed buoys for very remote,
unattended operation, while an observatory envisioned off Washington
and Oregon will be connected to land through seafloor fiber optic
cables. The DEOS (Dynamics of Earth and Ocean Systems) program will be
funded by a $125 million program within the National Science Foundation.
Earth Movements Studied in Minute Detail
A team at Scripps has developed the capability to measure distances
between points on land and on the deep seafloor to within a centimeter.
The first application of this new method has produced direct
measurements of convergence of the floor of the Pacific Ocean with
North America at a rate of about 4.5 centimeters per year off British
Columbia and Washington. This capability is being extended to studies
of the formation of new crust in the Pacific, and of the nature of
large-scale seafloor sliding on the submerged flank of the Kilauea
volcano. In connection with studies of potential major earthquakes,
scientists are using the method to study the subduction of the ocean
floor beneath seacoasts as far apart as Oregon and Peru.
Tracking Changes in Earth's Crust
Scripps operates the Cecil H. and Ida M. Green Pi on Flat Observatory,
the world's most advanced facility for monitoring changes in the shape
of Earth's crust. The observatory, near Palm Desert, California,
between the San Jacinto and San Andreas faults, enables scientists to
monitor two of the most active faults in California. Because of its
remote location and excellent infrastructure, the observatory is
internationally known as a proving ground for new kinds of geophysical
instruments, such as magnetometers and seismometers for Mars research.
A second observatory is located at Durmid Hill near the Salton Sea. The
new facility features laser strainmeters, instruments that precisely
monitor how the ground is moving. Scientists will soon install new
facilities in Los Angeles and at the future Yucca Mountain nuclear
waste repository.
Southern California Earthquake Center
The Green IGPP is a major partner in the Southern California Earthquake Center,
a collaboration of several research universities for earthquake
studies. Scripps scientists gather data from the center's continuously
monitored seismic networks, the Southern California Integrated GPS
Network, and the many advanced instruments at the Green Pi on Flat
Observatory. Scripps receives seismic data in real time from around the
globe.
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