MITSUKAIDŌ, September 21 — A magnitude 5.0 earthquake struck near Mitsukaidō in Ibaraki Prefecture, roughly 20 miles (32 kilometers) northeast of Tokyo, according to the United States Geological Survey. The agency classifies a 5.0 event as moderate, capable of causing light damage. The temblor occurred at 12:07 a.m. Japan time, USGS data shows, with its epicenter about 3 miles (5 kilometers) northeast of Mitsukaidō.
No casualties or damage have been reported in the source material. Japan sits on the Pacific Ring of Fire, an area with frequent seismic activity.
The quake’s location put it close to the Greater Tokyo area, one of the most densely populated metropolitan regions in the world — a reminder that seismic risk in this part of the archipelago is a permanent feature of doing business and living there, not an occasional disruption.
What the shake maps show
The USGS shake-severity map indicates that areas with a shake intensity of 3 or greater on the Modified Mercalli Intensity scale experienced “weak” shaking. The agency notes the earthquake may have been felt outside the areas shown on the map. The map, produced by The New York Times using USGS data, displays the area with a shake intensity of 3 or greater.
Population density data from LandScan via Oak Ridge National Laboratory was used to create it. All times on the map are Japan time.
Shake data is as of Wednesday, Sept. 16 at 11:23 a.m. Eastern. Aftershocks data is as of Wednesday, Sept. 16 at 11:38 a.m. Eastern. When aftershock data is available, the corresponding maps and charts include earthquakes within 100 miles and seven days of the initial quake.
Figures subject to revision
As seismologists review available data, they may revise the earthquake’s reported magnitude. Additional information collected about the earthquake may also prompt USGS scientists to update the shake-severity map. The USGS encourages residents in affected areas to monitor updates and follow local authorities’ guidance.
The New York Times map and accompanying article were produced by William B. Davis, Madison Dong, Judson Jones, John Keefe, Joey K.
Lee, and Bea Malsky. Watch for revised magnitude and shake-severity figures from USGS as seismologists work through the data, and for any aftershock mapping within the 100-mile, seven-day window the agency uses.
