The fault has distinct segments that act independently, each with its own history of earthquakes. Over the last 17 million years, the fault has experienced almost seven miles of slip, raising the mountains above the adjacent valley floor. "That's basically the process that formed the Wasatch Range," said geologist Chris DuRoss of the Utah Geological Survey. During prehistoric times, the fault slipped as much as 10 feet during a single quake.
It is one of the world's longest "normal" faults, where the land on one side of the fault drops down relative to the other side during an earthquake. Though the Wasatch Fault has not delivered a major quake since the Mormon settlers arrived in 1847, geologists have found evidence that it is capable of unleashing jolts as big as magnitude 7.5. Image: 1904 photo of trees bent during the 1811/1812 New Madrid earthquakes / USGS There are schools and police stations built like that." "It's just bricks sitting on top of bricks. "We have buildings that have been sitting around for 200 years," Schweig said. And most buildings in the area haven't been retrofitted. But 1812 was a long time ago, so earthquakes aren't anywhere near the top of most people's concerns in New Madrid. Small quakes remind residents of that every few months or weeks. It is nearly impossible to live in the San Francisco or Los Angeles areas without knowing there is an earthquake hazard. While the probability of a major quake on any given day in the New Madrid region is far less than that of the Bay Area in California, the potential for disaster if a quake does strike is greater due to the size of the area that could be violently shaken.Īnother factor is the lack of awareness and preparedness in the area. The USGS's best estimate is that there is a seven to 10 percent chance of a major earthquake between magnitude 7.5 and 8 in the next 50 years. But earthquakes are impossible to predict, and because scientists aren't even sure why major quakes occur away from plate boundaries, it is even more difficult to estimate a probability for New Madrid. The quake was felt over an area of two million square miles - nearly two-thirds of the country.īy analyzing deposits of sand that squirted out of the ground during past major quakes, Schweig and others estimate an average time between earthquakes of 500 years. In 18, a swarm of at least three massive earthquakes struck near New Madrid, the largest of which exceeded a magnitude 8 and caused violent, damaging shaking in an area 10 times larger than did the 1906 earthquake. "New Madrid is about as far from a plate boundary as you can get." Geological Survey, who has studied the area for 23 years.
"It's a big mystery," said geologist Eugene Schweig of the U.S. But in the middle of the country lurks a geological enigma near New Madrid, Missouri, that has produced some of the largest quakes on record for the United States but has yet to be fully explained by scientists. Most of the major earthquakes in the world occur at tectonic plate boundaries where land masses are colliding or pushing past one another. "Portland has lots of unreinforced masonry buildings" that are likely to collapse in a major quake, Goldfinger said. Making matters worse, the region isn't prepared. In fact, is new research on landslides puts the probability of a magnitude 8 or greater quake as high as 75 percent in the next 50 years. "It's been 308 since the last one so the probability is much higher," Goldfinger said. It created a tsunami that crossed the entire Pacific Ocean and caused damage along parts of the Japanese coast. The last monster quake that ruptured the entire length of the Cascadia fault occurred in 1700 and was around a magnitude 9. Unfortunately, the fault may be due for another big one any day now. Cascadia is the same type of fault that caused the 2004 Sumatra quake and tsunami.įortunately, these mega quakes only come around once every few hundred years. On top of the danger from shaking, within minutes, a tsunami would likely inundate the low-lying coastal areas.
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The shaking could last a full four minutes, which would damage or bring down structures that could have survived a shorter duration. There could be thousands of deaths and unprecedented damage for a quake in this country. "There are lots of other earthquakes that may happen first, but they won't be as big," said marine geologist Chris Goldfinger of Oregon State University in Corvallis.Īn earthquake of this size would completely devastate the region, which includes Portland, Seattle and Vancouver.
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