Reviewed by USGSJapan104y ago
M7.0 earthquake 70 km WNW of Naha, Japan
Monday, April 23, 1923, 03:17:00 UTC · 26.401°N, 127.010°E
A magnitude 7.0 earthquake struck 70 km WNW of Naha, Japan on Monday, April 23, 1923, 03:17:00 UTC, at a depth of 20.0 km (shallow). It is the strongest earthquake within 300 km since an M7.3 on July 4, 1917.
- Magnitude
- 7.0
- Strong · mw
- Depth
- 20 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 earthquake
In context
How big was it, and why here?
Energy released
415 kilotons of TNT
That is about 28 times the Hiroshima bomb. It released about 871 times the energy of a magnitude 5.0.
Tectonic setting
46 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
20 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 100 km
USGS has not published any M2.5+ earthquake within 100 km in the 30 days after this event.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 12 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 · 274 km W of this epicenter
- 7.3120 km ENE of Hirara, JapanJuly 4, 1917 · 150 km SW of this epicenter
- 7.012 km SE of Ginowan, JapanFebruary 23, 1911 · 87 km E of this epicenter
- 6.892 km NNE of Hirara, JapanJuly 4, 1917 · 164 km SW of this epicenter
- 6.859 km NE of Hirara, JapanNovember 29, 1910 · 187 km SW of this epicenter
- 6.588 km NW of Hirara, JapanMay 2, 1906 · 260 km SW of this epicenter
- 6.421 km SSW of Hirara, JapanMarch 25, 1916 · 266 km SW of this epicenter
- 6.367 km WNW of Naze, JapanJuly 4, 1914 · 299 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 3 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1768M6.5
Ryukyu Islands
22 Jul 1768 · 54 km away
Limited damage (under $1M)tsunami
- 1853
Okinawa
3 Oct 1853 · 63 km away
tsunami
- 1858
Ryukyu Islands
Sep 1858 · 54 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.