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How Long After Japan Earthquake Was Tsunami (And Why)?

Exact Answer: After 5 to 6 minutes

Although earthquake magnitude is one of the factors that affect tsunami generation, there are also other important factors to consider. The earthquake should be a superficial marine event that displaces or makes a massive movement on the seafloor or the earthen plates. The thrust earthquakes are way more capable of generating tsunamis, but small tsunamis have occurred in a few cases from large that are of the lesser magnitude of less than 8 strike-slip earthquakes.

So taking back to the date of March 11, 2011, when an earthquake of magnitude 9 hit Japan. It shook the entire north-eastern part of Japan. It even led to a destructive and perilous tsunami. The effects of the earthquake were deadly. All the different corners of the world felt it. Even people from Norway’s fjords and ice glaciers of Antarctica felt the disaster. The tsunamis detritus continued to wash up on North American beaches even after years of that destructive havoc on Japan.

How Long After Japan Earthquake Was Tsunami?

EarthquakeThis earthquake hit Japan at 14:46 JST. It caused devastation for about 6 minutes.
TsunamiThe tsunami was triggered by an earthquake that reached heights within 30 minutes. This led to the melting down of three nuclear reactors thereby triggering a nuclear disaster.

Firstly, talking about the facts that on 11th March of 2011, Japan, a small yet much-advanced country, witnessed the ultimate face of destruction. It got hit by a massive earthquake which was terrible to encounter. As Japan is a water-bound country by its coastal sea, the earthquake took place nearby, making it more menacing. This is because earthquakes usually take place due to the movement in the tectonic plates.

But as it was a sea-bound country, the displacement in those tectonic plates took place more under the sea bed. The Earthquake recorded a maximum magnitude of point 9 which is enough for mass destruction. And as it was surrounded by sea and when the Earthquake itself took place under the sea bed, it resulted in a tsunami. Tsunami means massive tidal waves crushing and swallowing everything in its giant tides coming by its way.

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So when the earthquake took place it brought a Tsunami as bonus destruction. This is because the movement of tectonic plates under the sea bed resulted in an aggressive massive tidal movement later taking the form of dangerous waves which was the Tsunami of destruction for the people of Japan. And it took a mere 5 to 6minutes for the earthquake to bring the tsunami into action.

And as the Tohoku region is too near to the sea which consists of the pacific ocean the tectonic movements took very little time to change their form of destruction from earthquake to tsunami.

Why Was Tsunami So Long After Japan Earthquake?

So here it needs to be clarified that these results are all based on various research and the reading of the Richter scale on which the magnitude of the earthquake was recorded. There are various reasons associated with this very question such as why it took this long for the earthquake as many questions would why it(earthquake) didn’t turn into a tsunami at the same time or why not earlier or later.

But foremost comes the basic and most important reason that the earthquake took place on a massive scale which caused numerous destruction. It was recorded on the Richter scale that the earthquake that took place on that particular date varied from Magnitude 9 to 9.1. And when the magnitude is on a larger scale of the earthquake then the tsunami wouldn’t take much time to reach its destination of destruction. But then comes another reason that relates it to the geographical condition of that region.

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So basically it took place in the pacific ocean 75 kilometers east of the Oshika peninsula of the Tohoku region so being so close to the ocean makes it too easy for the earthquake to bring the tsunami on. As the megathrusts created by the earthquake were of magnitude 9 to 9.1 and looking at such a mere distance, it wouldn’t have been difficult for the Earthquake to bring a Tsunami in 5 to 6minutes.

So basically it’s not a single thing that made an earthquake this longer to make a tsunami happen. And it’s a well-known thing that at this point of magnitude on the Richter scale the tsunami wouldn’t be able to make a way out either earlier or later apart from the time it took.


So from the above explanations, it was very clear how and why it took this long for the earthquake to become a tsunami. But it’s never a rigid concept that it will take this amount of time to turn an earthquake into a tsunami. As it was said earlier, it depends on the various aspects and conditions under which the tsunami took place.

It may be the magnitude, geographical condition, or other aspect but the impact varies. If the earthquake would have been of lesser magnitude then the level of destruction would have been minimized. As may be the tsunami wouldn’t have taken place which would have resulted in fewer lost lives. Hence the amount of time taken by the earthquake in the Tohoku region of Japan to turn into a Tsunami was for these various reasons and possibilities.