LIGHT sleepers and nightowls may have felt a small earthquake in Niseko early this morning – shockwaves from a 6.8 magnitude quake in Honshu, Japan’s main island.
In Niseko it probably only registered about 1 on the Richter scale – cupboards rattled and houses creaked, but heavy sleepers would have missed it.
The quake’s epicentre was in Iwate Prefecture in Honshu’s north just below Hokkaido at 12.26am.
The quake registered as an upper 6 on the Japanese intensity scale of 7. The Japanese scale is called the Shindo Scale.
In Iwate, a mountainous region known for onsens (volcanic hot springs), more than 100 people have so far been reported injured, and there has been widespread damage.
One month ago a 7.2 quake struck the same region and killed 23 people.
While Japan is perched on the edge of the ‘Pacific Ring of Fire’, where 90% of the world’s earthquakes occur, Niseko is not very quake prone. The immediate Niseko region’s biggest earthquake appears to have been in 1940 when a magnitude 5 quake struck just north of Niseko at 44 degrees north latitude (Niseko is 42 degrees north).
There wasn’t much damage from that quake, but it triggered a 2m tsunami which struck the west coast of Hokkaido and killed 10 people.
The worst earthquake in Japanese history struck Tokyo and Yokohama in 1923, killing more than 100,000 people. Its magnitude was estimated to be somewhere between 7.9 and 8.4.
The most devastating recent quake hit the city of Kobe, near Osaka, in 1995. It measured 7.2 and killed more than 6000 people. 100,000 houses were destroyed and hundreds of thousands more damaged.
While the Richter scale measures the total magnitude of a quake, the Japanese Meteorological Agency (JMA) shindo scale describes the degree of shaking that occurs at a given point – apparently based purely on observation.
According to the JMA, a rating of less than 1 is ‘imperceptible to people’; 2 is ‘Felt by many people in the building. Some sleeping people awakened’; during a 4 ‘Many people are frightened. Some people try to escape from danger. Most sleeping people are awakened. Hanging objects swing considerably and dishes in a cupboard rattle. Unstable ornaments fall occasionally’; while all hell breaks loose at 7 – people are ‘thrown by the shaking and (it is) impossible to move at will’ and ‘Most furniture moves to a large extent and some jumps up’.