What is shindo converted to Richter scale?

Answer 1

There is no conversion possible because shindo and magnitude are two different things. Shindo is more precise and is dependant on several parameters not taken into account by the magnitude, including the depth of the epicentre, the distance from it and the ground composition to name a few.

Magnitude is a global and theoretical value and measures the total amount of energy released by an earthquake. The shindo scale gives a local measure at a given place and shows the effective effect of the earthquake at this point.

Magnitude is much less used than shindo in Japan because it doesn't show directly the violence of an earthquake. An earthquake can be quite powerful (eg M6.0) but yet stay unnoticed by people in the area because it occurred too far from any inhabited place (eg in the middle of the ocean, 400 km from the land). By using the shindo measure ("An earthquake has occurred this morning with a maximum observed shindo of 5- in Miyagi and Fukushima prefectures, and shindo 2 in Tokyo"), you have a better idea of how severe it is, and which area are the most concerned.

The only time where magnitude can be more useful than shindo is to estimate the risks of tsunami when the epicentre is in the ocean. With a magnitude of M6 or lower, the risks of tsunami are low, while they become very significant when M>7.

Now to give two examples, we had 2 noticeable earthquake (= shindo>1) in the Tokyo region during the last 15 hours. This is quite usual in the area since the big earthquake in march 2011.

The first one yesterday evening was M5.8, max shindo=4 (observed at only one point, 4 is quite scary but furniture shouldn't fall too much) and the shindo observed in Tokyo was 2. The epicentre was more than 100km from the coast, and almost 200km from Tokyo. Its depth was 20km which is shallow.

The second one this morning was M5.4, max shindo=5- (observed at several points, 5- means it's pretty scary if you're in the area because big things are falling around). It occurred in the ocean but very close from the coast (maybe <10km) so that the places where the maximum shindo value of 5- was observed are near the coast, very close to the epicentre. The depth is 60km which is quite the average (a bit shallow). While Tokyo is located 110km from the epicentre, the maximum shindo measure in a few Tokyo wards was 3, 2 in most of the city though.

The big earthquake in march 2011 was M9.0, max observed shindo of 7 (7 being the maximum on the scale), depth = 10km (if I remember well) and a distance from the coast of about 70km. The shindo in Tokyo was 5+.

I've been living in Japan for 7 years and I really don't understand why we don't use the shindo scale (or something similar) in Europe or the US. It is much more practical and meaningful.