An earthquake occurred at approximately 6 a.m. local time (4 p.m. Eastern U.S.), Nov. 22, offshore of the Fukushima Prefecture, the same site of the powerful 2011 earthquake. The initial magnitude of this most recent earthquake was upgraded to 7.3/7.4 from an initial 6.9 reading.
According to earthquake and tsunami expert Robert Weiss of Virginia Tech, the earthquake of Tuesday morning is marked by being the “first real test for the earthquake evaluation and tsunami forecast system in the region.
“It showed that it worked well. Even without official warnings, people responded appropriately by running for higher ground or into the vertical evacuation structures. Overall, the respond to the evacuation message was fantastic, and is proof, in my opinion, that proactive policy, not just on a state or county level, but on the country level, works and ensures a limited impact, even of a small event.”
Weiss, an associate professor of geosciences, added, “There is a fine line between under and overreacting to such an event, but the orderly, and data and model-informed evacuation certainly helped to minimize the economic impact today’s earthquake and tsunami will have. In the United States, we certainly have the same technical, engineering and scientific expertise, as well as the computational resources as Japan, yet our preparation for natural disasters, their estimate of physical infrastructure damage, socio-economic impact and cascading effects has not been leveraged to its full capacity. Decision and law makers have not consistently reserved a seat for science on table when policy is made.”
Additional quotes from Dr. Weiss
On the Tsunami
“Shortly after the earthquake, tsunami warning for the immediate area of Fukushima was issued and advisory for the area north and south of the Fukushima Prefecture. Tsunami predictions associated with the tsunami warning and advisory were between 1 meters and 3 meters, where the 3 meters where indicated possible in very localized areas. Measurements of the tsunami reach 90 centimeters which is very close to the predicted value. And it is reported that the waves reached 1 meter near the Fukushima nuclear power plant.”
On the differences in earthquake magnitude reports from today’s event
“The magnitude and location of the earthquake are determined with the help of the seismometer recordings at stations around the globe. Different waves are generated during an earthquake, and these different waves travel with different forces through Earth. The more data from seismometers around the globe are available, the more robust are the estimates of the magnitude. However, it takes time for seismic waves to arrive at seismometers to reliably estimate the magnitude. Also, different standards and methods are used to determine the magnitude.”
On the cause of tsunamis and the duration of their threat to coastal land
“Earthquakes cause deformations of the ocean floor, building a mountain. This mountain is built very fast, too fast for gravity to bring the surface of the ocean into equilibrium. Because of that inability to adjust, the ocean surface deforms as well mirroring the mountain at the ocean floor on top of the ocean surface. Finally, this mountain at the surface of the ocean collapses and generates the tsunami. The tsunami has more devastating impact at the coast, the larger the magnitude, shallower underneath the earth surface, and the closer the coast is form the epicenter.”
On Fukushima’s propensity for earthquakes
“Japan in general is very prone to large earthquake that in turn generate large tsunamis because it is located along the Ring of Fire and its subduction zones. In fact, Japan’s historical documents are full of descriptions of tsunami impacts. The most famous one occurred on 27 January 1700, which is dubbed the orphan tsunami because the tsunami waves arrived without the ‘usual” ‘warning signs of the earthquake --shaking. The tsunami of 1700 was caused by an earthquake in the Cascadia subduction zone, in the Pacific Northwest of the United States. The word tsunami comes from the Japanese word for harbor wave.”
About Robert Weiss
Robert Weiss is an associate professor with the Department of Geosciences, with the College of Science at Virginia Tech. His research focuses on sedimentology, coastal engineering, and oceanography, with a goal of understanding the response of the physical environment to tsunamis generated by earthquakes, slides, and oceanic meteorite impacts and the records that such processes produce.
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