![]() ![]() ![]() "It makes me feel somewhat useless as a scientist" said Atwater.įor example, scientists' understanding of recurrence intervals, the time between major earthquakes on a particular fault, is advancing steadily. "It's a pretty murky science, predicting when the next one's going to occur," Shennan, of Durham University, said. Seismologists know as well as anyone that more answers often lead to more questions, and most are loathe to pin down specific dates and locales of future quakes. "If you include both of those effects, essentially you see a very nice pattern of a buildup in probability prior to the earthquake, and then a sudden fall after the earthquake."Ī major benefit of automated models like this, Rundle explained, is that they can be back-tested against existing earthquake data to determine how accurate the forecasts are. ![]() "Our new forecast still uses the rate of small earthquake activity, but it also uses the time since the last earthquake," Rundle said. At the moment, they're updating their current worldwide forecasts to account for the time that has elapsed since a region's last major earthquake. Rundle's group designs models that attempt to forecast major earthquakes - magnitude-6.0 and above in the United States, and magnitude-7.0 and above in Japan and other places in the world. "Most models now use the rates of small earthquake activity to try to forecast whether there will be a major earthquake or not," said John Rundle, an earthquake dynamics expert at the University of California, Davis. Though far from the world of historical documents and Native American legends, forecast models are another type of tool that has helped scientists calculate earthquake risks. "All that stuff came together to paint a picture of a hazard that would otherwise take this region by surprise someday." "It's an example of geophysical intuition followed by geological mucking around in estuaries, dovetailing with a long tradition of historical research looking at Native American traditions and old documents in Japan to figure out earthquake and tsunami history," Atwater said. "Understanding the Cascadia earthquake of 1700 is one of the success stories," Atwater told OurAmazingPlanet. Historical documents describing a massive tsunami in Japan in 1700 - called "the orphan tsunami" because Japan's residents felt no accompanying earthquake - also helped scientists recognize the potential for a major earthquake along the northwestern coast of North America, near current-day British Columbia, Washington, Oregon and California, because that is where the earthquake that triggered the tsunami actually occurred. ![]() Geophysicists recently used documents from historical settlements in Haiti and reports from the Spanish government to tease out a centuries-long cycle of earthquakes on the island of Hispaniola. Native traditions and historical documents can also provide important clues about the size and locations of past earthquakes. This zone produced a magnitude-9.2 earthquake in 1964 - the largest earthquake in North American history. Much of Shennan's research has focused on sea level changes associated with the Aleutian Megathrust, a subduction zone (where one tectonic plate is being shoved beneath another) off the coast of Alaska. "Layers of mud and peat can help us reconstruct the timing between earthquakes and their spatial extent, and from that you can begin to deduce the dynamics of the earthquake cycle." "Sediment cores can typically take you back about 5,000 years," said Ian Shennan, a geography professor at Durham University in England. Scientists also know that many of the planet's tectonic boundaries seem to generate earthquakes on pronounced - but varying - seismic schedules.īut geoscientists still face the challenge of using the tools at their disposal to interpret earthquake risks without inciting widespread panic or false senses of security.Īncient sediments can tell very detailed stories about past earthquakes and tsunamis, and sediment analysis is one of the most basic tools geologists use in interpreting these historical earthquakes and the seismic patterns in a particular region. Geophysicists and seismologists worldwide recognize that certain areas of the globe are more prone to seismic activity than others (the infamous " Ring of Fire" around the Pacific Ocean, for example). "Essentially we don't know where or when the next major earthquake will hit, and one just has to live with that uncertainty," said Brian Atwater, a geologist with the U.S. ![]()
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