Japan’s megaquake risk: What you need to know and should you still travel there? | CNA Explains

Japan’s megaquake risk: What you need to know and should you still travel there? | CNA Explains

Many have been wondering
if they should cancel their trips to Japan because of a high risk
that a mega earthquake might occur there. Let’s break down what’s going on,
and if there is cause for concern, Japan is bracing for
what could be one of the deadliest natural disasters in its history. A mega earthquake in the Nankai Trough,
which is just off the Pacific Coast. And experts say there is now an 80% chance
it’ll hit within the next 30 years. But first, what is a megaquake
and how is it different from an earthquake? Megaquake (are) generally defined as an earthquake of magnitude
8.5 or higher. Megaquakes mainly depend
upon the geological conditions of the area and also on the historical recurrence
interval. Megaquakes are rare,
but not unprecedented. Globally, they occur roughly once every 10 to 20 years. If that happens, up to 300,000 people in Japan could die. And we’re not just talking about
the ground shaking. This quake could trigger tsunamis
as high as 34m. That’s like a 10-storey building
coming at you. And the economic hit an estimated 1.81
trillion U.S. dollars in losses. But what exactly is the Nankai Trough? It’s a 900km-long trench under the Pacific Ocean, where the Philippine Sea plate
is sliding under the Eurasian Plate. That constant pressure means the Nankai
Trough is seismically highly active, and it’s known for producing mega
earthquakes roughly once in 100 to 150 years. A massive quake at this subduction zone is known as a megathrust earthquake,
and it can result in tsunamis. And Japan, one of the most earthquake
prone places on Earth, sees about 80% of magnitude-8 and -9
earthquakes along this zone. Remember the 2011 disaster? A magnitude-9 quake off Japan’s
northeast coast triggered a devastating tsunami and triple reactor meltdowns
at a nuclear power plant, killing over 15,000 people. If a megathrust earthquake happens,
major cities like Osaka, Kyoto and Hiroshima
could be in the tsunami’s path. Over 1.23 million people,
which is roughly 1% of Japan’s total population, may need to evacuate. The Japanese government
is taking this seriously. Japan’s Earthquake Research
Committee monitors the area constantly, and just last year issued
its first ever advisory for a possible magnitude-9 quake after a 7.1
tremor hit the trough on Aug 8. Is it possible to prepare
for an incident of this scale, and will there be obvious signs
leading up to the megaquake? There are no consistently reliable warning signs in the lead
up to a major earthquake. While scientists study potential precursors, earthquake
cannot concurrently be predicted with the precision they’re always
predicted with certain uncertainty in terms of exact
time, location, and magnitude. There are 3 important points
regarding warning signs. Number one, foreshocks. They are small quakes. Sometimes precede a larger one. As happened in the 2011 Tokyo earthquake. However, most small earthquakes
do not lead to a large one. So foreshocks are only identifiable in hindsight. And there’s a lot of uncertainty
there as well. There’s anecdotal reports out there. There are evidences of animals
acting strangely and changes in ground
water has been noted. They are also precursors,
but they are not scientifically reliable and are highly inconsistent. Third warning sign changes in crustal stress. Crust is the upper part of Earth
or ground deformation, (as) you call it. So scientists use GPS satellite data to monitor strain that builds up in the fault zones, like we have Nankai Trough in Japan. While there are no clear
precursor signs to look for, you can be prepared by number one, paying attention to official alerts, especially if you are in Japan, it’s the Japan Meteorological Agency, JMA. Knowing evacuation rules. Emergency shelter locations. Keep emergency kit with you ready. Should have some water, food,
flashlight and medical supplies there. So if you are near the coast,
then be aware of the tsunami risk as well, given the estimated scale
of the megaquake. How will other countries be affected? Could tsunamis reach as far as Singapore? Direct impact on Singapore
would be minimal. Tsunamis generated by a megaquake
in Japan would primarily affect Pacific Ocean basin. Especially Japan’s coastline,
parts of Russia’s far east, maybe Taiwan, the Philippines, and possibly Hawaii and US west coast. However, indirect effect might be felt in Singapore,
maybe such as supply chain. Disrupted imports from Japan are affected. Maybe economic impacts on
like all other global markets. Singapore have that. Possible travel delays, flight
rescheduling, especially the routes
transporting Japanese airspace. etc. So with all that in mind, is it safe to go
on a trip to Japan in the near future? While we can’t predict
exactly when a megaquake will strike, scientists can identify where and how likely they are over time. But uncertainty is very high. In Japan, the risk is high over the next
few decades, but not so immediate. Japan has invested
heavily in early warning systems. They have invested heavily
in infrastructure resilience, and they have heavily invested
in public education, significantly mitigating risk to life and property. While we can’t predict
exactly when a megaquake will strike, scientists can identify where
and how likely they are over time.

Japan issued an unprecedented warning in August 2024: a “megaquake” could strike near the Nankai Trough. Triggered by a 7.1-magnitude quake off Kyushu that month, this advisory marked the first time the government formally alerted the public to the risk of a major seismic event that could see around 300,000 people dying and tsunamis as high as 34m.

What is the Nankai Trough? Will there be signs leading up to the megaquake? What about travelling to Japan in the near future? Here’s what you need to know.

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