Taiwan earthquake: Countries which are tsunami-prone must innovate on measures to combat large, violent waves

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New Delhi: On Wednesday a magnitude 7.4 earthquake struck just before 8:00 am local time south of Taiwan’s Hualien City. The United States Geological Survey (USGS) put the epicentre 18 kilometres south of Taiwan at a depth of 34.8 kilometres.

According to the latest reports, at least seven people were killed and nearly 730 injured by the earthquake that also caused significant infrastructure damage. It is said to be the strongest earthquake to hit Taiwan in decades and also prompted tsunami warnings that, before being lifted, extended to Japan and the Philippines.

“The earthquake is close to land and it’s shallow. It’s felt all over Taiwan and offshore islands,” said Wu Chien-fu, director of Taipei’s Central Weather Administration’s Seismology Center. Aftershocks can still be felt in Taipei with more than 50 aftershocks registered till now, according to Taiwan’s central weather administration.

Tsunamis; occurrence, predictions and precautions

In Taiwan, Japan and the Philippines, subsequent to the earthquake, authorities issued a tsunami warning but later the Pacific Tsunami Warning Center said the threat had “largely passed”.

While the threat is said to have been “largely passed” for now, earthquakes in this region often trigger tsunamis which can turn deadly and cause massive damage. They have the potential to cause damage even in areas far from an earthquake’s epicentre. Despite recent strides in geosciences it is still not possible to predict earthquakes and tsunamis. What nonetheless remains problematic is that even if some predestination was made possible, the erratic and violent nature of tsunamis would still make it difficult to take ample measures against them.

Tsunamis are in essence ocean waves, but much larger and more intense. They, unlike normal waves, are not a product of the gravitational pull of the Sun and the Moon. They are generated by a large displacement of water in the ocean, often triggered by a single, major event. Events as varying as volcanic eruptions, landslides and meteorite impacts can be events which trigger tsunamis. The major initiator for most recorded tsunamis though are earthquakes.

Japan, for example, has the highest recorded history of tsunamis because of its geological positioning in the Pacific ring of fire, with earthquakes of varying magnitudes regularly occurring off the coast of the island nation and accompanying areas in the region. This is because of the presence of many tectonic plate boundaries in the region, including the Pacific, Juan de Fuca, Cocos, Indian-Australian, Nazca, North American and Philippine Plates.

Most of these plates overlap each other in the region, converging in what are known as ‘subduction zones’, where one tectonic plate moves against the other and in the process subsides and subsequently melts under it. This movement of one plate against the other causes earthquakes and the melting part causes volcanism.

Thus, 75 per cent of Earth’s volcanoes and 90 per cent of Earth’s earthquakes occur along this path. Most major tsunamis too see their origin here.Tsunamis generate when disturbances on the sea floor from earthquakes cause a sudden vertical displacement of the overlying water. This causes a movement in the stationary water mass, which becomes highly energised and possesses large prospects of causing damages offshore.

The energy that results from the movement of colliding oceanic tectonic plates finds a way out when an earthquake occurs. This process though is slow and sudden which makes it difficult to predict. These movements do not take place in human timescales and their high uncertainty has made earthquake prediction still not possible till the present day.

Tsunamis, which occur due to an earthquake, then become even more hard to predict. The fact that not every major oceanic earthquake is sure to trigger a tsunami makes the problem even more compounded.

Still there are some recent methods of tsunami predictions which have been employed in different parts of the world. Chief among them are automated systems to provide warnings immediately after an earthquake in time to save lives.

Using bottom pressure sensors, to detect changes in water densities and pressures of overlying water columns, have often been seen as useful.

These measures are still not absolute. To then combat tsunamis, some tsunami resistant measures have also been implemented in areas that frequently suffer from them. These might include tsunami walls and floodgates, but the heights of tsunamis are often such that these measures often are of not much help.

Going forward, for the time being it is clear that prediction of earthquakes and tsunamis will not be possible. Then the next likely step, for countries which are more tsunami-prone, is to innovate on measures to combat large, violent tsunami waves. Especially in the regions affected by the Pacific ring of fire. Just because tsunamis are sporadic in nature does not mean that the damages they can cause should be ignored, it is not every time that an earthquake will not result in a tsunami.

(Disclaimer: The views expressed in this article are those of the author alone. The opinions and facts in this article do not represent the stand of News9.)

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