lardycake wrote:
I can't remember if it was this forum or somewhere else, but somebody posted a link about scientists that have predicted a 50% chance that within the next 4 years an earthquake will hit Tokyo killing 9,000 and injuring 100k.
That appears to be mixing reports. Recently, studies have been published about the probability and effects of an earthquake centred under Tokyo bay. This event would cause 9,000 or more deaths in Tokyo and is likely to happen in the next 30 years.
I have also seen reports about more imminent quakes (next 3 to 4 years) which would be powerful but with a more distant epicentre (from Tokyo's point of view) and these would be disruptive rather than deadly.
dizmox wrote:
Touhoku was a 9 and the buildings seemed completely fine, but it was 70km from the epicentre right? Is that "9" a measurement of the entire energy released in the earthquake, or local intensity measurement? I think it's the former, in which case I can't imagine what being at the epicentre would be like.
Earthquake strength numbers in Japan give a figure for the epicentre and also local ("shindo") numbers. The local number shows the strength in various locations on a scale from 1 (barely noticeable) to 7 (most buildings are damaged) details.
You can use the following rough rule of thumb to estimate the shindo in various locations:
Local strength = Epicentre strength minus distance from epicentre in kilometers divided by a hundred
E.g. Kobe earthquake strength in Tokyo: 7 – 500/100 = 2
Tohoku earthquake strength in Tokyo: 9 – 400/100 = 5
(actual measurements were 1 and 5 respectively)
(Note, when calculating distance take both horizontal and vertical into account)
kitakitsune wrote:
You're much more likely to be killed by a fire post quake than by anything falling on your head. This is what happened in Kobe and the last big Tokyo quake.
Post-quake fires are a significant hazard, but the great majority of victims in Kobe were crushed to death. Details (Japanese Wikipedia). There was a major fire in 長田区, but others were smaller scale.
In the 1923 Kanto quake the proportion of fire deaths was much higher, but lessons were learned and buildings and evacuation procedures have been greatly improved.
activeaero wrote:
...something like 90% of the buildings destroyed in Kobe were traditional wood frame homes with heavy tile roofing which is pretty much the worst structural design on earth for surviving an earthquake.
The heavy tiles are to protect against typhoons, but clearly not so good in quakes. Brick buildings would be worst of all as they tend to disintegrate with violent shaking. Hence brick is hardly used in Japan (buildings that appear to be brick are usually tiled to give that appearance).
