Reviewed by USGSChile40y ago
M4.2 earthquake 116 km NNE of San Pedro de Atacama, Chile
Saturday, April 18, 1987, 22:51:16 UTC · 21.896°S, 67.894°W
A magnitude 4.2 earthquake struck 116 km NNE of San Pedro de Atacama, Chile on Saturday, April 18, 1987, 22:51:16 UTC, at a depth of 300.8 km (deep).
- Magnitude
- 4.2
- Light · mb
- Depth
- 301 km
- Deep
- 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: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
30 tons of TNT
That is about 1/500 of the Hiroshima bomb. A magnitude 5.0 releases about 16 times more energy.
Tectonic setting
44 km
from the nearest mapped plate boundary, between the Altiplano and South American plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: deep
301 km
Deep earthquakes (over 300 km) happen deep inside subducting plates. They rarely cause damage, but can be felt faintly over very large distances.
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 50 km
USGS lists 1 M2.5+ earthquake within 50 km in the following 30 days; the largest was M5.4 on May 12, 1987. 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 315 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 8.2121 km SSE of San Pedro de Atacama, ChileDecember 9, 1950 · 231 km S of this epicenter
- 7.751 km W of Atocha, BoliviaNovember 29, 1957 · 161 km NE of this epicenter
- 7.3136 km WSW of Challapata, BoliviaJune 6, 1915 · 296 km N of this epicenter
- 7.334 km NE of Tocopilla, ChileDecember 21, 1967 · 213 km W of this epicenter
- 7.334 km S of Iquique, ChileFebruary 23, 1933 · 283 km NW of this epicenter
- 7.278 km SW of Colchani, BoliviaOctober 4, 1910 · 134 km N of this epicenter
- 7.1136 km E of Iquique, ChileJune 14, 1959 · 194 km NW of this epicenter
- 7.064 km NNE of Antofagasta, ChileNovember 20, 1928 · 263 km SW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 23 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 2,392 recorded deaths. The most severe:
- 1877M8.3
Off North Coast
10 May 1877 · 273 km away · intensity XI
2,385 deaths$2 million damagetsunami
- 1953M7.4
Northern
7 Dec 1953 · 86 km away
3 deaths$7 million damage
- 1967M7.5
Northern
21 Dec 1967 · 167 km away
1 deathModerate damage ($1–5M)tsunami
- 1976M7.3
Pozo Almonte, Oficina Victoria, Arica
30 Nov 1976 · 186 km away · intensity VIII
1 deathModerate damage ($1–5M)
- 1959M7.5
Bolivia-Northern Chile
14 Jun 1959 · 170 km away
1 deathLimited damage (under $1M)
- 1950M8.0
Chile-Argentina
9 Dec 1950 · 183 km away · intensity VII
1 death
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.