Researchers use GPS data to speed up tsunami warnings
U.S. seismologists currently testing new warning system
Scientists in the United States have been testing an advanced tsunami warning system using GPS data, combined with traditional seismology networks, to attempt to detect the magnitude of an earthquake faster so warnings of potential tsunamis can get out to potentially affected areas sooner.
The prototype is called California Integrated Seismic Network (CISN), and is a collaboration between the United States Geological Survey (USGS) and The Gordon and Betty Moore Foundation, whose focus is on environmental conservation.
The foundation has given a grant of $6 million (US) to seismologists at the University of California, Berkeley, California Institute of Technology (Caltech), and University of Washington, Seattle, in order to find the most efficient way to capture and analyze seismic data to ensure adequate warning can be given to people on the ground.
"Our research is focused on trying to get data from closer to the earthquake itself in order to determine more rapidly the magnitude," said Yehuda Bock, Research Geodesist and Senior Lecturer from Scripps Institution of Oceanography.
Bock moderated a panel at the annual meeting of American seismologists on April 17, which included 6 members who are collaborating on the new system.
Bock said after the magnitude nine earthquake and tsunami that struck Japan in March 2011, the team "saw the limitations," in the current system.
"It took about 20 minutes or so to estimate magnitudes and it required getting seismic data far from the earthquake source, and the tsunami hit after 30 minutes," Bock said.
Traditionally seismologists have used Seismometers located close to an earthquake to pick up the energy expelled by it and transmit that information around the world, which would provide warnings to highly populated areas before the ground starts shaking.
Where the Seismometers fail is in accurately predicting the severity of the earthquake, when it is approaching or larger than a magnitude seven.
Richard Allen, director of the seismological laboratory at the University of California, Berkeley, is also involved in the CISN development, and says the problem that existed in the past was a saturation effect in the data; essentially meaning the scale would show similar magnitude estimates for seismic events that are clearly of different sizes.
That’s where the team is hoping the GPS will help.
Although it does take a little longer to arrive, GPS is very good at presenting magnitude, because it accurately shows how much the ground is physically moving. "We're talking about real-time accuracy within centimeters," Allen said.
Allen says the system is still currently in test mode but is working well, and had an opportunity to be used after a minor earthquake in California in early March.
"At my desktop in Berkeley I got 25 seconds warning for that event," Allen said, attributing the success to recent upgrades in both hardware and software.
Allen say the system needs more equipment to become public, and hopes, if funding goes as planned, the system will be ready for 2015, and it’s current price tag is estimated at $150 million.
Detecting Tsunamis Using Global Positioning System (GPS)
There are two ways GPS can be used to detect an earthquake and possible Tsunami.
The first is in the atmosphere.
When an earthquake occurs within the ocean floor, the displacement of the ocean surface in turn displaces the atmosphere within about 15 minutes, and eventually reaches the upper part of the atmosphere, known as the ionosphere.
The changes that take place to the electron density in the ionosphere are called ‘tsunami signature’, and can be identified by the available GPS data.
The second way the technology is used in detecting tsunamis is through the GPS satellite radio signals, which are picked up by ground stations located in the oceans, around the world. Using these signals a scientist can then measure how far GPS ground stations are displaced during an earthquake, allows them to calculate the magnitude of the earthquake, as well as how large a tsunami wave might be if produced.
Tsunami warnings in North America
Keeping a close eye on the research as it develops is Paul Whitmore, director of the West Coast and Alaska Warning Center, which is headquartered in Palmer, Alaska.
The Centre has the responsibility of monitoring seismic events that affect continental North America, including the coast of British Columbia, as well as Puerto Rico and the Virgin Islands.
"At this point, use of GPS is still in the research stage," Whitmore said, but added "it has great potential for the Tsunami Warning System, but is not presently used in operations."
Whitmore says his own team has made big changes since the 2004 tsunami that all but destroyed the Indonesian coast. One area involves making the data and forecasts generated by the center more understandable.
"Our centre itself have almost tripled our staff," Whitmore said, from six to 17, so the centre could have 2 scientists analyzing seismic events all the time to help respond faster to potential earthquakes.
The amount of data coming in to centre has also increased almost threefold, Whitmore says, and there has been a great improvement in the availability of sea level observation networks.
He explains when the centre detects a seismic event there are two stages of response.
The first is gathering the earthquake information, evaluating it and sending out an early alert out based on the earthquake. Whitmore says they don’t wait to confirm a tsunami has actually been generated by the quake because, "that’s too late for those first impacted," in terms of giving them enough time to get safety.
The second stage is analyzing sea level data, leaving the centre to determine whether a tsunami was triggered, how big it is, and who’s at risk based on the epicenter.
"Based on these analysis we can extend warnings or cancel warnings or downgrade them to advisories," Whitmore said.
One of the challenges, Whitmore explains, is that it’s hard to tell quickly how powerful a really big earthquake is. A magnitude 8.5 or more quake may continue to ‘rupture’ for more than five minutes, so when the centre attempts to get out a very quick alert within 3 or 4 minutes, it’s tough to know how big it is.
If there’s a quake off the coast of B.C., if it’s over magnitude 7.1 or 7.5, the centre sends out a warning for areas within 250 km of the epicenter. If it’s a bigger earthquake than that, the warning area is extended and an advisory is posted.
The messages are then, as fast as possible, sent out to weather forecast offices, state and province emergency services, the coast guard, and the military. Each of those agencies has their own responsibilities— for example, the weather forecast offices in the United States will activate the emergency alert system.
He laments no system is perfect and there are still challenges, mostly around forecasting and getting the important message out to people on the ground quickly. But Whitmore says a lot of effort is being invested in improving forecast methods even more, and that’s where the GPS research is expected to help.