On Sunday night, a large earthquake struck underwater off the coast of Japan and gave the entire Tokyo area a good shake. Then, on Tuesday morning, the Tokai region was visited by a much closer earthquake which damaged the main expressway between Tokyo and Nagoya.
Both quakes were around 7 on the Richter scale, which sounded catastrophic to my friends in California, but they would not have been quite as panicked if they were using the Japanese scale. This is because the Richter scale measures the power of an earthquake at its source (magnitude), whereas the Japanese shindo scale measures its power at the surface (seismic intensity). The Japanese scale basically breaks down as follows:
- 1 = Barely noticeable
- 2 = Noticeable but not scary
- 3 = Rattles unsecured objects
- 4 = Knocks unsecured objects over
- 5 = Damages rickety buildings
- 6 = Damages earthquake-resistant buildings
- 7 = The Earth cracks open; demons emerge; everyone dies
Each location would therefore report a different number from the same earthquake, based on the effects on the ground there. The Japan Meteorological Agency publishes a map showing the seismic impact of each earthquake at various locations, as well as its epicenter. Around Tokyo, Sunday’s quake was around 3 or 4 on the Japanese scale, largely as a result of the quake being deeper underground and farther offshore; Monday’s quake was even weaker for us, but folks in the Izu Peninsula area got to experience seismic effects in the 5 to 6 range.
The foreign media, being sensationalists, still love to use the Richter scale for everything, despite the fact that it serves little practical purpose other than scaring my parents.