Reviewed by USGSChile87y ago
M7.2 earthquake in Near the coast of Tarapaca, Chile
Friday, October 4, 1940, 07:55:00 UTC · 19.978°S, 70.425°W
A magnitude 7.2 earthquake struck in Near the coast of Tarapaca, Chile on Friday, October 4, 1940, 07:55:00 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M7.3 on February 23, 1933.
- Magnitude
- 7.2
- Major · mw
- Depth
- 35 km
- Shallow
- Felt reports
- 0
- Did You Feel It?
- Est. shaking
- VII
- Very strong (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
985 kilotons of TNT
That is about 65 times the Hiroshima bomb. It released about 2,065 times the energy of a magnitude 5.0.
Tectonic setting
102 km
from the nearest mapped plate boundary, between the Nazca and Altiplano 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 200 km
USGS lists 2 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M6.3 on October 6, 1940. 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 16 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.3136 km WSW of Challapata, BoliviaJune 6, 1915 · 266 km E of this epicenter
- 7.334 km S of Iquique, ChileFebruary 23, 1933 · 65 km S of this epicenter
- 6.9119 km W of Iquique, ChileSeptember 15, 1911 · 93 km W of this epicenter
- 6.925 km ENE of Arica, ChileAugust 30, 1906 · 183 km N of this epicenter
- 6.9181 km W of Iquique, ChileAugust 25, 1916 · 154 km W of this epicenter
- 6.987 km NNW of Iquique, ChileDecember 26, 1906 · 51 km N of this epicenter
- 6.6152 km WNW of Tocopilla, ChileOctober 22, 1920 · 217 km SW of this epicenter
- 6.5105 km SSE of Arica, ChileDecember 4, 1934 · 106 km NE of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 38 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 28,085 recorded deaths. The most severe:
- 1868M8.5
Arica
13 Aug 1868 · 165 km away · intensity XI
25,000 deaths$300 million damagetsunami
- 1877M8.3
Off North Coast
10 May 1877 · 169 km away · intensity XI
2,385 deaths$2 million damagetsunami
- 1833M7.7
Peru: Tacna; Chile: Arica
18 Sep 1833 · 202 km away · intensity VIII
700 deathsSevere damage ($5–24M)tsunami
- 1878M7.9
Tarapaca
23 Jan 1878 · 11 km away · intensity VIII
Severe damage ($5–24M)tsunami
- 1871M7.3
Chile
5 Oct 1871 · 34 km away · intensity X
Severe damage ($5–24M)tsunami
- 1934M6.9
Iquique, Pisagua, Sapiga, Negrero
4 Dec 1934 · 110 km away
Moderate damage ($1–5M)tsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.