Ring of Fire Earthquakes Form Lesson for Pacific Northwest


     (CN) — Along the Ring of Fire earthquake zone that borders the Pacific Ocean, the earthquakes that recently struck Japan and Ecuador may show what can happen in the Pacific Northwest with similar fault-line dynamics and geography.
     Ecuador’s magnitude 7.8 earthquake on April 16 has killed at least 550 people and caused billions of dollars in damage. The same day, a magnitude 7.0 earthquake in Japan killed at least 41 people and injured over 1,000.
     The occurrence of earthquakes is random, and geologists say the two quakes are not related. But they serve as an example of what could happen to areas with similar fault-line dynamics and geography.
     The earthquake in Ecuador was a subduction zone earthquake — the same type of quake that scientists expect will someday hit the Pacific Northwest.
     Landslides, massive avalanches and a tsunami are some of the side effects that such an earthquake could produce, potentially leading to more deaths than any previous natural disaster in American history.
     “A large subduction zone earthquake in the Pacific Northwest will likely have widespread, devastating consequences on the population and infrastructure,” Randall Jibson, a research geologist with the United States Geological Association, said in an email to Courthouse News. “Strong shaking, capable of major damage, will likely extend over a large region.”
     Jibson said that a subduction zone earthquake occurs when one tectonic plate is pushed underneath another during a rupture, and the magnitude is based on the length of the rupture.
     The Cascadia Subduction Zone extends from Vancouver Island in Canada to Northern California, separating the North America and Juan de Fuca plates. Due to its length, the Cascadia fault can produce large earthquakes and tsunamis.
     The geographic conditions and plate boundaries of the Pacific Northwest resemble Ecuador, which suggests that a subduction zone earthquake around Washington and Western Canada could resemble the effects of the April 16 temblor.
     While the United States has greater financial resources at its disposal, more money will not help the region avoid the destruction and injuries that Ecuador faces.
     “The earthquake doesn’t care about the GDP of the country,” said Ben Mason, an assistant professor of geotechnical engineering at Oregon State.
     Researchers believe that a subduction zone earthquake in the Pacific Northwest could resemble the 2011 Tohoku earthquake in Japan — which led to the Fukushima disaster — and the 2010 earthquake in Chile. Those earthquakes measured at magnitudes of 9.0 and 8.8, respectively.
     Some experts believe that a subduction zone earthquake in the Pacific Northwest could measure between magnitude 8.0 and 9.0. A 9.0 produces 32 times more energy than an 8.0 quake generates.
     “The ground shakes can cause buildings to be damaged, weak soils can fail, utilities that are in the soil can stretch and break,” said Youssef Hashash, a fellow of the American Society of Civil Engineers. “If you have very interconnected infrastructure, we don’t know how they’d work. Sometimes that interdependence can be really problematic.”
     Mason said many cities and states in the Pacific Northwest are not prepared for the effects of a subduction zone earthquake, since the region has not experienced one since the Cascadia earthquake in January 1700.
     “The difference is that Japan has been prepared for earthquakes for a long time; they have a lot more policies set up,” Mason said. “Here in Oregon, before the 1990s we didn’t consider seismic damage before building the buildings.”
     Robert Moss, an associate professor at Cal Poly San Luis Obispo and a member of the American Society of Civil Engineers, said the Pacific Northwest could learn from safety efforts in Chile and Japan.
     “The Japanese have a long history of preparing for tsunamis, and Chile is a good analogy for modern tsunami-hazard mitigation,” Moss said. “They have relocated cities such as Concepcion, and armored ports to address frequent earthquakes that cause tsunamis.”
     Mason said there have been legislative efforts to prepare states in the region, including a seismic safety commission in Oregon that studied what the state needed to do to prepare for an earthquake.
     These actions are a good start, but additional planning and strategies are needed to minimize the damage that could result from a subduction zone earthquake, Mason said.
     “I’m very optimistic about the plan; it’s a step in the right direction,” Mason said. “There’s a lot of work to be done for us to be confident that we’re going to respond well to this earthquake.”
     Additional efforts to minimize the impact of a subduction zone earthquake will be expensive and time-consuming, which presents a challenge to emergency management agencies and scientists.
     Jibson said that effective prevention plans require thorough mapping of hazards from earthquake-triggered landslides, and other issues.
     “Such an effort would help identify areas of concern, which could, in turn, lead to thoughtful advanced planning for zoning, emergency response, and disaster preparedness,” Jibson said. “But applying them over a large region is very challenging and would entail considerable time and expense.”
     The impact of such an earthquake would partially depend on how residents of the affected states respond.
     “I’m an optimist. When people are faced with that scenario, I think that survival mode will kick in and they’ll be able to help their neighbors,” Mason said.
     Japan’s earthquake on April 16 was centered on a slip-strike fault, a vertical fracture where blocks mostly move horizontally. Less powerful than subduction zone earthquakes, slip-strike quakes often occur in urban areas with dense populations.
     Such an earthquake could occur on the San Andreas Fault, which is a slip-strike fault.
     “It’s very much an active threat,” Mason said.
     The San Andreas Fault is 810 miles long, extending from the Mendocino coast 170 miles northwest of San Francisco to the San Bernardino mountains, about 90 miles east of downtown Los Angeles.
     “The last very significant earthquake that struck the San Andreas was an 8.1 in 1906, centered right on the city of San Francisco,” Mason said. “Seismologists are very cognizant of the fact that another earthquake, perhaps around the same magnitude, could strike that area of the San Andreas Fault again.”

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