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
