Physicists who have developed a new method of forecasting large earthquakes didn't have to wait long for validation of their technique.
One Southern California earthquake occurred, as they'd forecast, while their research paper was awaiting publication, and another came just three days after the paper was published in the Feb. 19 issue of the Proceedings of the National Academy of Sciences.
But John Rundle of the University of Colorado, lead author of the study, isn't exactly jumping up and down with joy. He says the earthquakes gave him and his colleagues some measure of "professional satisfaction," especially since nobody was hurt, but it will be a long time before he or anyone else knows whether he is really on to something.
Rundle and Kristy Tiampo of the university's Cooperative Institute for Research in Environmental Sciences, along with colleagues at NASA's Jet Propulsion Laboratory in Southern California and the Los Alamos National Laboratory in New Mexico say they have come up with a new way of forecasting large earthquakes, and they have laid it all out there for the rest of us to see if they are right.
Looking at the Big Picture
If they are, California is in for a lot of shaking before this decade ends, and Rundle thinks — although he quickly admits he doesn't know for sure — that he knows where those quakes are most likely to occur.
He doesn't know exactly when they will hit, and a forecast that calls for them to strike sometime in this decade is of limited use to urban planners, but Rundle says at this point it's just "a real time experiment to see if this works."
A forecast is different from a prediction in that it offers a probability of a quake occurring within a designated time frame as opposed to a far more precise prediction calling for an earthquake of a certain magnitude on a certain fault on a certain date. Seismologists would like to be more precise, but so far, no one has figured out how to predict just when and where the next quake is going to hit.
So most forecasts are based on evidence that any particular fault is likely to rupture sometime in the next few years.
Rundle and his colleagues have taken a different approach. They have compiled a 70-year history of smaller earthquakes (magnitude 3 and above) throughout Southern and Central California in an effort to determine changes in seismic patterns since 1932. It is those changes, rather than the potential of any particular fault, that rule the seismic roost in any earthquake zone, according to the researchers.
The scientists divided the region into about 3,000 "boxes" measuring about seven miles on each side, resulting in a grid-like map of Central and Southern California. (Seven miles is roughly the length of the rupture along a fault required to produce an earthquake of magnitude 6.)
All earthquakes of magnitude 3 or greater were plotted on the map, along with the time they occurred. That gave the scientists a way to determine how seismic patterns had changed over time.
The result: "complicated mixtures of seismic quiescence and seismic activation," Rundle says.
Most Quakes Mapped in Empty Regions