Earthquake News

New earthquake study is concerning for the Pacific Northwest.

Scientists are still investigating the massive earthquake and tsunami that struck Japan last year, and part of what they are learning is concerning for the Pacific Northwest.

Researchers presented their findings at the annual meeting of the American Association for the Advancement of Science on Sunday. They found that detailed analyses of how the Earth warped along the Japanese coast indicate that shaking from a Cascadia megaquake may be stronger than anticipated along the coasts of Washington, Oregon, and British Columbia.

According to John Anderson of the University of Nevada, the Tohoku region and the Cascadia subduction zone are like mirror images of each other.

Anderson gathered ground motion information from the Japan earthquake and superimposed it on a map of the Pacific Northwest, which features an offshore fault comparable to that in Japan called a subduction zone.

The largest shocks in Japan happened undersea. The enormous tsunami was caused by the seafloor shifting by 150 feet or more in some locations. But in the Northwest, where the Pacific coast is so close to the subduction zone, the land will be the one that is shaken the hardest.

The ground vibrations from Tohoku may really be a sign of far more intense shaking along the coastal regions of British Columbia, Washington, and Oregon, according to Anderson.

Cities like Seattle, Portland, and Vancouver, British Columbia, are enough inland to avoid the most ferocious hammering. However, every urban center is situated on a geologic basin that has the ability to intensify ground motion like waves in a bathtub.

Anderson said that "basins tremble more than hard rock." Strong ground vibrations can be significantly influenced by local site circumstances.

When the Cascadia subduction zone next fully lets free, the U.S. Geological Survey (USGS) is already hard at work on a new analysis of how violently the ground will likely shake and how close the rupture zone might get to urban areas. The last time was in 1700, and the quake that followed was a magnitude-9 quake, precisely like the monstrous one that hit Japan on March 11, 2010.

Scientists continue to sift through the huge network of seismometers, satellites, strain meters, and GPS sensors in Japan to gain new insights.

It's the best megaquake ever recorded, and it has a lot to do with the danger in Cascadia, according to Anderson.

Why was the earthquake so powerful, for example, is a topic that Japanese experts are unable to fully resolve. How did the tsunami grow to such enormous size? And why was it such a shock to the country with the best seismic knowledge in the world?

According to Jim Mori, director of the Disaster Prevention Research Institute at Kyoto University, "it was highly demoralizing for anyone doing earthquake research and hazard mitigation in Japan."

According to Kenji Satake of the University of Tokyo, a series of tiny earthquakes that shook the region roughly every 35 years confounded seismologists.

They thought that every minor earthquake released pressure from the subduction zone, the location where two tectonic plates meet as the ocean floor pushes beneath the continent.

They now understand that stress increases over time, eventually leading to a large earthquake punctuating the series of smaller ones every 700 years. Similar quakes and tsunamis occurred in 869 and 1896, but Japanese scientists did not delve far enough into their own past, according to Satake. "Longer time records were required,"

The subduction zone with the longest record is in Cascadia, where scientists have connected submerged wetlands and undersea landslides with a string of around 22 megaquakes that have occurred over the past 10,000 years. With an average of roughly 500 years, the intervals between earthquakes range from 200 to 1,000 years.

As Satake notes, there is no evident "supercyle" of supergiant earthquakes in Japan. However, it is evident that the size of earthquakes in Cascadia has varied, according to USGS geologist Brian Atwater. Some geologists contend that the magnitude-9 earthquake that occurred 300 years ago was merely typical and that the Northwest had previously been devastated by earthquakes twice as large.

Scientists still don't know how much that has to be increased post-Tohoku, although the majority of earthquake scenarios for the Northwest coast estimate tsunamis of roughly 30 feet. On the Japanese coast, entire settlements were carried away by walls of water up to 120 feet high.

Mori questioned, "Is there a 40-meter tsunami coming ashore in Cascadia as well?"

He said that some of the criteria used to assess the risk associated with subduction zones had been shown to be suspect in Japan.

The measurement of strain accumulation, as shown by bulging and sinking land masses, is foremost among them. Scientists had anticipated to spot imminently rupturing fault segments, but according to Mori, the tension on the Japan subduction zone was not particularly noteworthy.

According to Kelin Wang of the Geological Survey of Canada, scientists are reconsidering which subduction zones are the most hazardous.

According to a new theory, the topography of the seafloor may be important. He said that as oceanic plates scrape beneath continental plates, they appear to hang up and slip more frequently.

When sections of the fault rupture, it is followed by a string of lesser tremors. Where the seafloor is smooth and devoid of features, such as along the Northwest coast, Wang added, large quakes appear to happen more regularly. The two plates may stick together over extremely large distances without being hindered by surface ridges and slopes, he claimed. When they fall, the entire fault immediately collapses.

Stuart Nishenko of Pacific Gas and Electric, which runs the Diablo Canyon nuclear facility on the California coast, said the nuclear-power industry is still struggling with the effects of the meltdowns at Japan's Fukushima nuclear complex.

Seven countries made the decision to either phase out nuclear energy or halt the construction of new reactors, including Switzerland, Germany, and Mexico. According to Nishenko, the U.S. Nuclear Regulatory Commission is getting ready to issue directives to all 104 of the country's nuclear reactors needing fresh seismic safety studies.

Additionally, operators will need to revise their contingency plans for dealing with a total loss of power, as occurred when the Japanese tsunami knocked, and walk through their facilities with inspectors to search for any parts or systems susceptible to earthquakes or floods.

The Columbia Generating Station, which is situated on the Hanford Nuclear Reservation, is the sole nuclear power facility in the Pacific Northwest. Geologists have found a number of new faults that run across the region and are capable of producing earthquakes with a magnitude of 7.5. A license extension to run the 28-year-old reactor till 2023 was recently requested by plant management.

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