The orphan tsunami of The Pacific

Tsunami can cause devastation, taking the souls of entire towns and villages as they arrive with a single wave front, taller than many buildings and stretching as far as the eye can see. They're not like a beach wave, crashing and gone, tsunami keep going, some for minutes before they recede only to arrive again as the next front impacts the shore line. And they travel across seas and oceans at the speed of a jet liner.

An earthquake in Chile has set this process in motion. Usually an earthquake precedes a tsunami, providing a warning that it will arrive, the ground shakes and the seas rise. But orphan tsunami are not like this. The earthquake may have generated the wave nearly half a planet away, there's no feeling of shake or temblors, no sudden shock followed by a rolling sway as the ground moves under your feet. Today we receive warning via satellite and TV. But that was not always the case.

In 1700 a massive earthquake on the Cascadia fault line, offshore from Vancouver, sent a stealth wave directly at Japan. Unrecorded in North America, it's known from Japanese records kept at the time. Again in 1960, a M9+ quake in Chile sent waves across the ocean that arrived at over three meters high. Communications, having been substantially improved over the years, allowed for warning and evacuation. But that orphan wave still took over 100 lives, and that was after it had taken out Hilo. Today's wave was ok, 80cm at most when it reached Japan. Stay safe everyone.

Tsunami waves simply don't stop for anything

Orphan tsunami - an alert in Japan

The M8.2 earthquake experienced by Chile yesterday was massive. Few quakes in history have been larger and in fact there have been less than twenty of this scale anywhere in the world in the last 150 years. And earthquakes can produce tsunami. And these can be worse. Then following a M5.3 in Tohoku at 8.22 this morning a tsunami warning was briefly issued but quickly cancelled.

However, one characteristic of these huge waves is that they travel enormous distances relatively undiminished. The Chile quake created a two meter wall of water towards the immediate coastline but it also sent one in the opposite direction into the Pacific. These orphan tsunami are historically unpredictable but can be devastating when they come on shore as they arrive without tremor or warning. And now, after it has crossed the ocean, we're under tsunami warning again in Japan. Twice in one day.