M6.8 earthquake 148 km SE of Katsuren-haebaru, Japan

Sunday, August 12, 1923, 10:06:07 UTC · 25.494°N, 129.031°E

A magnitude 6.8 earthquake struck 148 km SE of Katsuren-haebaru, Japan on Sunday, August 12, 1923, 10:06:07 UTC, at a depth of 15.0 km (shallow). It is the strongest earthquake within 300 km since an M7.0 on April 23, 1923.

Magnitude: 6.8; Strong · mw
Depth: 15 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

247 kilotons of TNT

That is about 16 times the Hiroshima bomb. It released about 519 times the energy of a magnitude 5.0.

Tectonic setting

34 km

from the nearest mapped plate boundary, between the Okinawa and Philippine Sea plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.

Depth: shallow

15 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 8 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 5 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 12 recorded deaths. The most severe:

1911M8.0
Ryukyu Islands
15 Jun 1911 · 295 km away
12 deathsSevere damage ($5–24M)tsunami
1901M7.9
Ryukyu Islands
24 Jun 1901 · 193 km away
Limited damage (under $1M)tsunami
1768M6.5
Ryukyu Islands
22 Jul 1768 · 172 km away
Limited damage (under $1M)tsunami
1853
Okinawa
3 Oct 1853 · 163 km away
tsunami
1858
Ryukyu Islands
Sep 1858 · 172 km away
tsunami

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers