Reviewed by USGSJapan100y ago
M7.0 earthquake 125 km ESE of Katsuura, Japan
Thursday, August 18, 1927, 19:27:55 UTC · 34.552°N, 141.489°E
A magnitude 7.0 earthquake struck 125 km ESE of Katsuura, Japan on Thursday, August 18, 1927, 19:27:55 UTC, at a depth of 20.0 km (shallow). It is the strongest earthquake within 300 km since an M7.1 on August 14, 1924.
- Magnitude
- 7.0
- Major · mw
- Depth
- 20 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- IV
- Light (ShakeMap)
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 200 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
494 kilotons of TNT
That is about 33 times the Hiroshima bomb. It released about 1,035 times the energy of a magnitude 5.0.
Tectonic setting
22 km
from the nearest mapped plate boundary, between the Okhotsk and Philippine Sea 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 200 km
USGS lists 5 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.5 on August 23, 1927. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
- 5.6157 km SE of Katsuura, Japan100y ago · 59 km S of this epicenter
- 5.7212 km SE of Ōhara, Japan100y ago · 87 km SE of this epicenter
- 6.5171 km SE of Hasaki, Japan100y ago · 58 km E of this epicenter
- 6.2154 km ESE of Ōhara, Japan100y ago · 39 km E of this epicenter
- 5.9142 km SE of Ōhara, Japan100y ago · 17 km E of this epicenter
Regional history
Past M5+ earthquakes within 300 km
USGS lists 56 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.05 km SSE of Ōiso, JapanSeptember 1, 1923 · 211 km NW of this epicenter
- 7.85 km E of Tateyama, JapanSeptember 2, 1923 · 150 km W of this epicenter
- 7.3190 km SE of Hasaki, JapanSeptember 7, 1906 · 99 km E of this epicenter
- 7.264 km ENE of Hasaki, JapanJune 1, 1923 · 154 km N of this epicenter
- 7.238 km SSW of Shimoda, JapanOctober 24, 1905 · 244 km W of this epicenter
- 7.167 km ENE of Kashima-shi, JapanAugust 14, 1924 · 184 km N of this epicenter
- 7.1150 km ESE of Hasaki, JapanMarch 13, 1909 · 114 km NE of this epicenter
- 7.082 km ENE of Hasaki, JapanMarch 12, 1909 · 151 km N of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 18 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 117,492 recorded deaths. The most severe:
- 1923M7.9
Tokyo, Yokohama
1 Sep 1923 · 192 km away
105,385 deaths$600 million damagetsunami
- 1855M7.0
Tokyo
11 Nov 1855 · 196 km away
6,757 deathsExtreme damage ($25M+)tsunami
- 1703M8.2
Off Sw Boso Peninsula
30 Dec 1703 · 145 km away
5,233 deathsExtreme damage ($25M+)tsunami
- 1853
Odawara
11 Mar 1853 · 210 km away
79 deathsSevere damage ($5–24M)
- 1894M7.5
Tokyo
20 Jun 1894 · 193 km away
24 deathsLimited damage (under $1M)
- 1924
Sagami
15 Jan 1924 · 210 km away
14 deathsSevere damage ($5–24M)
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.