Michael said these forecasts, or hazard assessments, are broken into three time scaleslong, intermediate, and short term. Long- and intermediate-term forecasts are useful for government decisions, such as where to spend money retrofitting buildings to make them secure during an earthquake. Short-term forecasts help with decisions about where to position emergency supplies.
According to Michael, although people tend to want short-term earthquake forecasts, the long-term forecast is actually more important. "It does things like set building codes, so you don't care when it's happening because you're going to be safe anyway," he said.
Wyss said that people need to understand the probability component of earthquake forecasts. He likens an earthquake to a powder keg that is likely to go off soon, but what the exact spark will be that sets it off is unknown.
"Please accept as useful something that states a year and a large area, perhaps. Please accept from us a probability. There really is no statement we can make about the future that doesn't have a probability associated with it," he said.
In addition to earthquake forecasts such as hazard assessments, scientists also attempt earthquake predictions based on their understanding and analysis of the physics that govern earthquakes.
A "prediction is a statement that a single earthquake will take place, with a very high probability, in a specified region, time frame, and magnitude range," said David Jackson, director of the Southern California Earthquake Center at the University of California, Los Angeles.
For today, at least, Jackson said long-term forecasts are more useful than short-term predictions as long-term forecasts can be tested against the earthquake record. Predictions need a long string of success and failure to evaluate, which at this point does not exist.
But scientists are working on new prediction models. Michael is interested in the concept of predicting a major earthquake based on a pattern of increasing small earthquakes prior to the main event. "It's controversial, but with further investigation it may prove correct," he said.
Even more controversial is the concept of predicting earthquakes based on the strange behavior of animals such as dogs and cats. The animal method is largely dismissed by earthquake researchers as having no scientific basis. "Animal behavior is generally considered not worthy of study," Raymond said.
According to Wyss, since prediction is it based on physics telling scientists something is about to happen, their prediction can only be as good as their grasp on the physics. "We have a problem not knowing the Earth so well," he said.
Scientists hope that, as they develop and deploy new technologies to study the Earth, they will begin to understand the physics better.
Raymond is involved in the study of one such possible new technologyusing satellites to study the deformation of the Earth's crust as a possible precursor to earthquakes. We'll learn more about this technology in a future story.
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