Reviewed by USGSIndonesia97y ago
M6.4 earthquake 145 km S of Pagar Alam, Indonesia
Thursday, February 12, 1931, 05:44:05 UTC · 5.318°S, 103.021°E
A magnitude 6.4 earthquake struck 145 km S of Pagar Alam, Indonesia on Thursday, February 12, 1931, 05:44:05 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M7.0 on February 10, 1931.
- Magnitude
- 6.4
- Strong · mw
- Depth
- 35 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: 100 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)
In context
How big was it, and why here?
Energy released
54 kilotons of TNT
That is about 4 times the Hiroshima bomb. It released about 114 times the energy of a magnitude 5.0.
Tectonic setting
187 km
from the nearest mapped plate boundary, between the Sunda and Australian plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.
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 100 km
USGS lists 2 M2.5+ earthquakes within 100 km in the following 30 days; the largest was M6.6 on February 14, 1931. 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 22 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.573 km WSW of Bengkulu, IndonesiaJune 25, 1914 · 211 km NW of this epicenter
- 7.0164 km SSW of Pagar Alam, IndonesiaFebruary 10, 1931 · 47 km W of this epicenter
- 6.769 km SSE of Bengkulu, IndonesiaApril 15, 1916 · 119 km NW of this epicenter
- 6.7177 km SSW of Pagar Alam, IndonesiaOctober 22, 1925 · 38 km SW of this epicenter
- 6.679 km WSW of Labuan, IndonesiaAugust 13, 1913 · 290 km SE of this epicenter
- 6.5104 km WSW of Bengkulu, IndonesiaOctober 12, 1919 · 206 km NW of this epicenter
- 6.5271 km S of Pagar Alam, IndonesiaMarch 3, 1921 · 127 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 6 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 20 recorded deaths. The most severe:
- 1914M7.6
Sumatera
25 Jun 1914 · 204 km away
20 deathsLimited damage (under $1M)tsunami
- 1770M7.0
Sumatra:
1770 · 118 km away
Severe damage ($5–24M)tsunami
- 1931M7.4
Sw. Sumatra
25 Sep 1931 · 46 km away · intensity VIII
Limited damage (under $1M)tsunami
- 1818M7.0
Sumatra: Bengkulu
18 Mar 1818 · 223 km away · intensity IX
Limited damage (under $1M)tsunami
- 1896M6.8
Sw. Sumatra, Java
10 Oct 1896 · 210 km away
Limited damage (under $1M)tsunami
- 1930M6.0
Java-S. Java Sea
19 Jun 1930 · 254 km away
tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.