QuakeFactsEvidence report · prepared 2 September 2026https://quakes99.com/entity/iscgem901923
USGS iscgem901923
1 May 1939, 17:05
18 km WNW of Tenn?, Japan
A magnitude 6.6 mw earthquake at 10 km depth.
Published location
Where is 18 km WNW of Tenn?, Japan?
This locator uses the coordinates in the approved source record. It shows geographic context, not a site boundary, safety zone or property-risk area.
39.978000, 139.771000
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What the numbers mean
Magnitude measures event size; depth locates the source below the surface. Neither value alone establishes local damage or personal risk.
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Catalog fields and provenance
Event ID
iscgem901923
Coordinates
39.978, 139.771
Network
iscgem
Significance
678