Reviewed by USGSIndia89y ago
M6.1 earthquake 258 km SSE of Port Blair, India
Friday, October 7, 1938, 16:23:48 UTC · 9.544°N, 93.732°E
A magnitude 6.1 earthquake struck 258 km SSE of Port Blair, India on Friday, October 7, 1938, 16:23:48 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M6.5 on April 19, 1936.
- Magnitude
- 6.1
- Strong · 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: 100 km aftershock search area
In context
How big was it, and why here?
Energy released
20 kilotons of TNT
That is about the energy of the Hiroshima bomb. It released about 42 times the energy of a magnitude 5.0.
Tectonic setting
29 km
from the nearest mapped plate boundary, between the Cocos and Panama 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 100 km
USGS lists 1 M2.5+ earthquake within 100 km in the following 30 days; the largest was M5.6 on October 9, 1938. 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 18 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 6.8238 km WNW of Sabang, IndonesiaJanuary 20, 1917 · 282 km S of this epicenter
- 6.6249 km NW of Sabang, IndonesiaMarch 5, 1921 · 239 km S of this epicenter
- 6.5171 km S of Port Blair, IndiaApril 19, 1936 · 126 km NW of this epicenter
- 6.3273 km SSE of Port Blair, IndiaOctober 21, 1916 · 26 km SW of this epicenter
- 6.1211 km S of Port Blair, IndiaAugust 1, 1929 · 97 km W of this epicenter
- 6.0119 km SW of Port Blair, IndiaMay 13, 1925 · 222 km NW of this epicenter
- 6.097 km ESE of Port Blair, IndiaOctober 11, 1914 · 210 km N of this epicenter
- 6.0Nicobar Islands, India regionDecember 11, 1932 · 104 km S of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 2 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:
- 1881M7.9
Andaman I,Nicobar I
31 Dec 1881 · 183 km away
Severe damage ($5–24M)tsunami
- 1847
Little Nicobar Island
31 Oct 1847 · 246 km away · intensity X
Limited damage (under $1M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.