Question: Hello :) How often does a tsunami occur???

I realise it is a long answer, but your question deserves a detailed response.

Tsunamis come in different sizes and do not happen at regular intervals.
This means that there is no simple answer to your question such as “Twice a year”,

Here is what the UNESCO Tsunami Information Centre says about them.

Tsunamis are disasters that can be generated in all of the world’s oceans, inland seas, and in any large body of water. Each region of the world appears to have its own cycle of frequency and pattern in generating tsunamis that range in size from small to the large and highly destructive events. Most tsunamis occur in the Pacific Ocean and its marginal seas. The reason is that the Pacific covers more than one-third of the earth’s surface and is surrounded by a series of mountain chains, deep-ocean trenches and island arcs called the “ring of fire” – where most earthquakes occur (off the coasts of Kamchatka, Japan, the Kuril Islands, Alaska and South America). Many tsunamis have also been generated in the seas which border the Pacific Ocean. Tsunamis are generated, by shallow earthquakes all around the Pacific, but those from earthquakes in the tropical Pacific tend to be modest in size. While such tsunamis in these areas may be devastating locally, their energy decays rapidly with distance. Usually, they are not destructive a few hundred kilometers away from their sources.

That is not the case with tsunamis generated by great earthquakes in the North Pacific or along the Pacific coast of South America. On the average of about half-a-dozen times per century, a tsunami from one of these regions sweeps across the entire Pacific, is reflected from distant shores, and sets the entire ocean in motion for days. For example, the 1960 Chilean tsunami caused death and destruction throughout the Pacific. Hawaii, Samoa, and Easter Island all recorded runups exceeding 4 m; 61 people were killed in Hawaii. In Japan 200 people died. A similar tsunami in 1868 from northern Chile caused extensive damage in the Austral Islands, Hawaii, Samoa and New Zealand.

Although not as frequent, destructive tsunamis have been also been generated in the Atlantic and the Indian Oceans, the Mediterranean Sea and even within smaller bodies of water, like the Sea of Marmara, in Turkey. In 1999, a large earthquake along the North Anatolian Fault zone, generated a local tsunami, which was particularly damaging in the Bay of Izmit.

In the last decade alone, deadly tsunamis have occurred in Chile (2007, 2010), Haiti (2010), Indonesia (2004, 2005, 2006, 2010), Japan (2011), Peru (2001), Samoa – American Samoa – Tonga (2009), Solomons (2007). Of these, only Indonesia (2004) and Japan (2011) caused deaths at distant shores.

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