Existing GPS technologies
have been enhanced by scientists at NASA’s Jet Propulsion Laboratory (JPL) and
Scripps Institution of Oceanography at UC San Diego to develop new systems for
California and elsewhere to provide warning of hazards such as earthquakes,
tsunamis and extreme weather events.
Forecasters at NOAA National Weather Service offices in Oxnard and
San Diego, California demonstrated the new technology in July, using it to
track a summer monsoon rain affecting Southern California and issue more
accurate and timely flash flood warnings. The new technology uses real-time
information from GPS stations that have been upgraded with small, inexpensive
seismic and meteorological sensors.
Other real-world systems are integrating the new technology as well.
For example, it is being used to make damage assessments for hospitals, bridges
and other critical infrastructure that can be used in real time by emergency
personnel, decision makers and first responders to help mitigate threats to
public safety.
The primary goal for hospitals is to shut down elevators
automatically and send alerts to operating room personnel in the event of, for
example, an earthquake early warning. The earthquake early warning system is
particularly effective during large events. The system could be used to detect
changes in the structure of bridges due to earthquakes, wind shear and traffic
loads, as well.
The implications and possible applications of the new technology
were discussed by scientists from JPL and Scripps at the American Geophysical
Union meeting this past week.
“These advancements in monitoring are being applied to public
safety threats, from tall buildings and bridges to hospitals in regions of risk
for natural hazards,” said Yehuda Bock of Scripps Institution of Oceanography.
“Meaningful warnings can save lives when issued within one to two minutes of a
destructive earthquake, several tens of minutes for tsunamis, possibly an hour
or more for flash floods, and several days or more for extreme winter storms.”
An optimal combination of GPS, accelerometer, pressure and
temperature data is the basis for the new technology. This data is collected in
real time at many locations throughout Southern California and on large
engineered structures—like tall buildings, hospitals and bridges—for focused
studies of health and damage. The technology returns data products such as
accurate measurements of permanent motions (displacements) of ground stations
and instruments deployed on structures, which form the basis for early detection
of sustained damage; and measurements of precipitable water in the lower
atmosphere, a determining factor in short-term weather forecasting. The
combination of sensors significantly improves current seismic and
meteorological practices.
NOAA’s Earth System Research Laboratory used a regional
collaborative network of GPS stations—newly expanded to provide dense coverage
in Southern California—to provide atmospheric moisture measurements to
forecasters in the case of the first successful Southern California monsoon
forecast and more accurate flash flood warnings in July.
Hundreds of scientific-grade GPS stations throughout Southern
California are constantly receiving signals from GPS satellites to determine
their precise positions. GPS ground stations are simultaneously measuring water
vapor as well as position because water vapor in the atmosphere distorts GPS
satellite signals.
“These water vapor measurements are currently being used to help
forecasters better monitor developing weather during periods between satellite
overpasses and weather balloon launches,” said research scientist Angelyn Moore
of JPL. “Our project is upgrading GPS ground stations to get these data to
forecasters in minutes to seconds to help them better understand whether summer
monsoonal moisture is likely to cause harmful flash flooding.”
“This GPS network provides forecasters with timely and critical
information on the availability of atmospheric moisture, allowing us to more
accurately forecast and warn for potentially deadly flash flooding and
wintertime heavy precipitation events in Southern California,” said Mark
Jackson, meteorologist in charge at NOAA’s National Weather Service office in
Oxnard.
“Having such detailed and timely information on how much moisture
is available helps us better understand and forecast our extreme winter storms
fueled by what are known as atmospheric rivers. It can also help us better
pinpoint and anticipate thunderstorms capable of producing flash flooding.”
Weather forecasters in Southern California are moving from periodic updates of
moisture content once every 30 minutes to continuous updates. Balloon launches,
from four locations, occur only twice a day.
According to Bock, the technology improves earthquake early
warning by analyzing the very first moments of an earthquake in real time to
characterize the more violent shaking that will follow. It is possible to
predict the arrival of slower-traveling seismic “S” (secondary) waves that
cause the most intense shaking by detecting the initial arrival of seismic ‘P’
(primary) waves, which travel through Earth the fastest, at the upgraded GPS
stations.
Depending on distance from the earthquake’s epicenter, the warning
time can range between several seconds to as long as two minutes. Critical
fault parameters, such as earthquake magnitude, can be rapidly and accurately
determined to generate ground intensity maps throughout the affected region,
and form the basis of tsunami warnings.
The scientists are planning to integrate the technology into earthquake
and tsunami early warnings and structural monitoring for the San Diego County
Office of Emergency Service. Other institutions are examining the applications
of the technology as well, such as hospital monitoring and early warnings for
UC San Diego Medical Center in Hillcrest; monitoring of the Vincent Thomas
Bridge in Long Beach for Caltrans; and forecasts of storms and flooding for
NOAA’s weather forecasting offices in San Diego and Los Angeles.
