To support the development of a clear and accurate understanding of seismic activity, the Japan Meteorological Agency (JMA) conducts ongoing reanalysis of past tremors using the current hypocenter detemination method and occasionally reflects the results in its earthquake catalog.
The catalog previously contained no data on seismic activity from the period prior to 1923 due to loss of records in a fire at JMA Headquarters at the time of the Kanto Earthquake during that year. Against this background, JMA determined hypocenter locations from 1919 using local meteorological observatory records and released an earthquake catalog from 1919 to 1921 on 16 January 2020.
Numbers of earthquakes classified with reference to hypocenter deremination flags and an epicenter distribution map are shown below.
| ||||||||
Epicenter distribution map from 1919 to 1921 (K flags only) | ||||||||
 |