About 90% of the world’s earthquakes take place in the Ring of Fire, an area surrounding the Pacific Ocean laced with volcanoes. Though the name might conjure images of earthquakes spouting fire through cracks in the ground (or of Johnny Cash), this area is also prone to water damage in the form of tsunamis: 4 out of 5 tsunamis occur around the Ring of Fire. The 2004 Indonesia tsunami and the 2011 Japan tsunami have been perhaps the most notable of the 21st century.
Last Sunday’s magnitude 8.2 earthquake near Fiji raised fears of an impending tsunami, but not all coastal or under-water earthquakes create waves 100 feet in height. Tsunamis are usually triggered by earthquakes in tectonic plate boundaries. These plates are pushing past each other, creating pressure and sometimes getting stuck. When this happens, the plates don’t stop moving. Instead, the plate sliding underneath will cause the stuck upper plate to bend. Eventually, the upper plate will snap back into its previous position, causing an earthquake. If this snap happens underwater, waves will be displaced in all directions from the snap.
Tsunamis can travel at up to 500 miles per hour, but out in the deep sea these waves are only a few feet high and barely felt. As the waves approach land and shallower depths, the land slows the waves but, given that there is less space, the waves become larger and taller. If the earthquake is close to the shore, the waves will likely be tall and very strong. If the quake is far from the shore, only a temporary high tide may be experienced. If you’ve been in a small boat, think about how choppy the water feels near the shore even if the lake (or sea or body of water) is calm. The stronger the earthquake, the stronger and more far-reaching the tsunami can be. Fiji’s most recent earthquake and subsequent aftershocks caused small tidal waves, but not a tsunami per se.
While today’s technology allows us to pinpoint the source of tsunamis, that was not always the case. For centuries, scientists studied a January 1700 event they termed the “orphan tsunami.” No earthquake or origin-event could be pinpointed; that is, until the 1990s. Kathryn Schultz describes how seismologists and specialists Brian Atwater, David Yamaguchi, and their colleagues found the orphan’s parent—5,000 miles east, in the Pacific Northwest, on the opposite side of the Pacific Ocean.
We’ve written before about the so-called “Mega Earthquake” event that some predict will strike the Pacific Northwest in the Cascadia Subduction Zone. For years, scientists wondered whether this zone would even be able to produce a major earthquake. Seismologists now know an earthquake will indeed strike this zone, but are still uncertain about exactly when or how strongly it will strike. Chris Goldfinger and his team of researchers at Oregon State University concluded there is a 40% chance of a major earthquake in southwest Oregon during the next 50 years which could reach the intensity of the 2011 Japan earthquake. The Cascadia Subduction Zone, where the small Juan de Fuca tectonic plate is being subducted (i.e., sliding underneath) the large North American Plate along the Pacific Northwest and northern California, was thought to be a relatively dormant seismological area. Goldfinger’s research disproved that notion.
The potential 9.0-magnitude earthquake in the Cascadia Subduction Zone and the tsunami that may follow have been termed one of the most “terrifying disasters waiting to happen.” After the several-minutes-long quake, people in the area will have 20 to 30 minutes to reach high ground as the water from the shore recedes. Then, the tsunami will come. Several waves over several hours will inundate coastal communities, some of which will remain flooded throughout the event.
Ready.gov offers tips on what to do if you are under a tsunami warning or are in the midst of a tsunami. These may help you survive and keep safe in case of such a catastrophic event.
Unfortunately, some predict that the damage to the affected area’s infrastructure, homes, and businesses will be widespread, potentially exceeding $80 billion in losses. If you live in or near the Cascadia Subduction Zone, it may be a good idea to acquire insurance to mitigate potential losses. Make sure you read your insurance policy, as most homeowners’ insurance policies limit or preclude coverage for damage caused by flooding or a tsunami. These exclusions or limits typically apply to earthquake insurance policies as well. Nonetheless, flood insurance—which provides coverage for tsunamis—is available through the National Flood Insurance Program (NFIP) and through some private insurers which partner with NFIP.
Insurance industry practitioners, on the other hand, should be prepared to be inundated by a variety of claims arising out of tsunamis. Rebekah Paci-Green, director of the Resilience Institute and a professor at Western Washington University, noted the engineering community doesn’t have data on how the infrastructure in the Pacific Northwest responds to long periods of shaking. Information on how it responds to tsunamis is even more scarce. In Paci-Green’s words, “we’re only recently understanding the significance and the potential for a major Cascadia event.”
Posted by Akira Céspedes Pérez