Reviewed by USGSJapan110y ago
M7.3 earthquake 120 km ENE of Hirara, Japan
Wednesday, July 4, 1917, 00:38:27 UTC · 25.157°N, 126.432°E
A magnitude 7.3 earthquake struck 120 km ENE of Hirara, Japan on Wednesday, July 4, 1917, 00:38:27 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M8.1 on April 12, 1910.
- Magnitude
- 7.3
- Major · mw
- Depth
- 35 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 200 km aftershock search area
In context
How big was it, and why here?
Energy released
1.4 megatons of TNT
That is about 96 times the Hiroshima bomb. It released about 3,020 times the energy of a magnitude 5.0.
Tectonic setting
88 km
from the nearest mapped plate boundary, between the Yangtze and Okinawa plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
35 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
No “Did You Feel It?” reports have been published for this event yet. If you felt it, you can add your report on the USGS website.
I felt it — report to USGS ↗USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 200 km
USGS lists 1 M2.5+ earthquake within 200 km in the following 30 days; the largest was M6.8 on July 4, 1917. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 6 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.11910 Taiwan EarthquakeApril 12, 1910 · 232 km NW of this epicenter
- 7.012 km SE of Ginowan, JapanFebruary 23, 1911 · 183 km NE of this epicenter
- 6.859 km NE of Hirara, JapanNovember 29, 1910 · 76 km W of this epicenter
- 6.588 km NW of Hirara, JapanMay 2, 1906 · 178 km W of this epicenter
- 6.421 km SSW of Hirara, JapanMarch 25, 1916 · 134 km SW of this epicenter
- 6.219 km SE of Ginowan, JapanAugust 29, 1909 · 182 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 4 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 13,486 recorded deaths. The most severe:
- 1771M7.4
Ryukyu Islands
24 Apr 1771 · 251 km away
13,486 deathsExtreme damage ($25M+)tsunami
- 1768M6.5
Ryukyu Islands
22 Jul 1768 · 158 km away
Limited damage (under $1M)tsunami
- 1853
Okinawa
3 Oct 1853 · 165 km away
tsunami
- 1858
Ryukyu Islands
Sep 1858 · 158 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.