I’ve felt three earthquakes over the last few days, as shown on the alerts on my phone. They were minor occurrences for Japan, but even though I know how common quakes are here, my heart always starts pounding like crazy and my only thought is instinctive panic when I feel a tremor.
But for those who are interested in earthquakes more objectively and scientifically, you might be interested to know about the Japan Meteorological Agency seismic intensity scale, which uses a unit called shindo to measure the intensity of an earthquake. It’s different from the Richter scale, because it represents what an earthquake feels like to people on the ground, which, let’s be honest, is what we really care about.
A table from the meteorological agency explains the experience of an earthquake with examples from a human perspective as well as for structures (and I admit that it’s pretty scary). The shindo 4 earthquakes this week (which fortunately were not that close to me and therefore felt less intense) had the following effect indoors: “Hanging objects such as lamps swing significantly, and dishes in cupboards rattle. Unstable ornaments may fall.”
The screenshot below shows alerts I received after the terrifying succession of earthquakes in Kumamoto a few months back. From bottom to top, my phone shows an alert for a low shindo 6, a tsunami warning, two high shindo 5s, a high shindo 6, and then a low shindo 5. To paraphrase, people have trouble standing during a high shindo 6, buildings can collapse, and everything falls over. The Great East Japan earthquake in 2011 was a shindo 7 at the epicentre. Um, in case you were wondering.