Background: the Japan Meteorological Agency and its ten-degree seismic intensity scale
Background
Japan's new National Disaster Management Agency will depend on the warnings issued by the body that already watches the ground, so it is worth knowing that body.
The Japan Meteorological Agency monitors earthquakes, tsunamis and volcanic activity across a country that sits in one of the world's most active seismic and volcanic zones.
It runs an observation network of about 200 seismographs and 600 seismic intensity meters, and also takes data from more than 3,600 such meters run by local governments and by the National Research Institute for Earth Science and Disaster Resilience.
All of it feeds into the Earthquake Phenomena Observation System, known as EPOS, at the agency's headquarters in Tokyo and at the Osaka District Meteorological Observatory.
When an earthquake happens the agency announces its hypocentre, magnitude and observed seismic intensity.
If the intensity is 3 or more, a Seismic Intensity Information report goes out within a minute and a half.
The agency's own seismic intensity scale has ten degrees: 0, 1, 2, 3, 4, 5 lower, 5 upper, 6 lower, 6 upper and 7.
Intensity describes the shaking felt at a place, so it changes with distance from the epicentre and with the local geology.
In plain words
EPOS Earthquake Phenomena Observation System — The system into which JMA feeds all its real-time earthquake data.
NIED National Research Institute for Earth Science and Disaster Resilience — A Japanese research institute whose seismic meters also supply JMA.
seismic intensity seismic intensity — A measure of how strongly the ground shakes at a particular place, unlike magnitude which measures the quake itself.