Japan earthquake triggers tsunami warning: What is a tsunami, why does it keep forming in the island country?
- January 2, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Japan earthquake triggers tsunami warning: What is a tsunami, why does it keep forming in the island country?
Subject: Geography
Section: Physical geography
Context:
- Tsunami waves hit several parts of Japan’s coastal areas and urgent evacuation warnings were issued after a 7.6-magnitude earthquake shook the country’s north-central region.
Tsunami:
- Tsunami (a Japanese word that means “harbour wave”) is a series of giant ocean waves caused by earthquakes or volcanic eruptions under the ocean.
- When an earthquake occurs under the ocean, a large chunk of the ocean floor can suddenly move upward or downward, leading to a sudden displacement of a large volume of water, thereby causing tsunami waves.
- Similarly, the lava flowing out of the volcano displaces the water around it and that water can become a large wave.
- Other factors that can cause tsunamis are- landslides, meteorites and asteroid impacts.
- Characteristics:
- The formation of a tsunami can depend on a host of factors, including the shape of the ocean floor, and the earthquake’s distance and direction.
- Tsunami waves can be hundreds of feet tall and can travel as fast as jet planes over deep waters while slowing down when reaching shallow waters.
- Not all earthquakes or volcanic eruptions lead to tsunamis.
- Tsunamis generated in the open ocean appear to be only small waves.
- Tsunami waves become dangerous only when they get close to the coast.
- An increase in wave amplitude results in “shoaling” when waves, including tsunamis, run from deep to shallow water. This is significant in coastal regions. This phenomenon occurs because of the force from the seabed as it becomes shallower. This slows down the wave: the shallower the water, the slower the wave.
Why is Japan prone to earthquakes and tsunamis?
- Japan is situated along the ‘Pacific Ring of Fire’, which is the most active earthquake tectonic belt in the world.
- The ‘ring’ refers to “an imaginary horseshoe-shaped zone that follows the rim of the Pacific Ocean”, where many of the world’s earthquakes and volcanic eruptions occur.
- Within the Ring of Fire, there are different tectonic belts, including the Pacific Plate, Eurasian Plate, and Indo-Australian Plate, which keep meshing and colliding with each other, causing earthquakes, volcanic eruptions and tsunamis.
- The 2011 tsunami waves in Japan led to a nuclear meltdown at the Fukushima power plant, causing the most severe nuclear accident since the 1986 Chornobyl disaster in the Soviet Union.
Tsunami early warning system:
- The tsunami early warning system is crucial in mitigating the devastating impact of these powerful waves that can reach heights of 66ft (20m) and travel at speeds exceeding 400 miles per hour (644 km/hr).
- It consists of two key components: a sensor network to detect tsunamis and a communication infrastructure for timely alarms and coastal evacuation.
- This system relies on seismic-monitoring stations and sea-level gauges to detect earthquakes and abnormal sea-level changes, helping scientists confirm a tsunami’s occurrence.
- Despite its effectiveness, the system has limitations as it depends on physical measurements from buoys, and it can’t prevent sudden tsunamis that occur very close to the epicentre.
- Efforts to enhance warning procedures include assessing t-wave energy as an indicator of earthquake-induced tsunami potential, but current systems still face challenges in providing instantaneous protection against rapidly approaching tsunamis.
Meteotsunami:
- Meteotsunamis are large waves and unlike tsunamis triggered by seismic activity, meteotsunamis are driven by air-pressure disturbances often associated with fast-moving weather events, such as severe thunderstorms, squalls, and other storm fronts.
- The storm generates a wave that moves towards the shore and is amplified by a shallow continental shelf and inlet, bay, or other coastal features.
- Meteotsunamis have been observed to reach heights of 6 feet or more.
- They occur in many places around the world, including the Great Lakes, the Gulf of Mexico, the Atlantic Coast, and the Mediterranean and Adriatic Seas.
Source: Indian Express