The earth is still rumbling in Kumamoto, where last week, Saturday the 16th, a large earthquake with a magnitude of 7.1 has taken place. Already on Thursday, there was a foreshock of 6.4 magnitude, and until now, there were 15 earthquakes altogether with a magnitude of more than 5. These numbers are always a bit hard to grasp – what does “magnitude 6.4” mean in reality? Obviously, it is strong, but how strong?
In 1884, the Japanese Meteorological Agency has introduced the Shindo scale of earthquakes, which since 1908 includes descriptions of the effect an earthquake of a given magnitude has on people; and since the Kobe earthquake in 1995, there are 10 distinct levels on the Shindo scale.
So, for the Kumamoto foreshock we have Shindo scale 7, meaning for example:
Effects on people: Thrown by the shaking and impossible to move at will.
Effects on buildings: Most or all buildings (even earthquake-resistant ones) suffer severe damage.
Ground and slopes: The ground is considerably distorted by large cracks and fissures, and slope failures and landslides take place, which can change topographic features; ground acceleration of more than 4 m/s².
The main shock, Shindo scale 6+, had only marginally less severe consequences; theoretically, that is, remember that there was not much left after the first earthquake.
In the first two earthquakes, 44 people lost their lives, so far 8 are missing, and more than 3000 injured. If you live in Japan, the thought that this can happen to you, that you might be killed in the next earthquake which might just happen at your place, is always present in the back of your head. And still, it’s something you just deal with. Just like stepping on a plane and knowing that it may crash, you rely on the fact that airplane travel is the safest means of transport. Just like Japan, where centuries of dealing with 400 earthquakes a day have made it probably the safest place to be when you’re caught in the middle.