M5.9 earthquake 68 km SE of Sand Point, Alaska

Tuesday, October 6, 2020, 05:54:50 UTC · 54.851°N, 159.851°W

A magnitude 5.9 earthquake struck 68 km SE of Sand Point, Alaska on Tuesday, October 6, 2020, 05:54:50 UTC, at a depth of 31.0 km (shallow). USGS received 13 “Did You Feel It?” reports, with a maximum reported intensity of V (moderate). The USGS PAGER alert is green: low likelihood of casualties and damage. It is the strongest earthquake within 300 km since an M6.1 on July 28, 2020.

Magnitude: 5.9; Moderate · mww
Depth: 31 km; Shallow
Felt reports: 13; Max intensity V
Est. shaking: V; Moderate (ShakeMap)
PAGER alert: Green; Impact estimate
Tsunami: No flag; USGS feed

Outlined circle: this earthquakeDashed circle: 75 km aftershock search areaColoured lines: estimated shaking intensity (USGS ShakeMap)

In context

How big was it, and why here?

Energy released

11 kilotons of TNT

That is about the energy of the Hiroshima bomb. It released about 22 times the energy of a magnitude 5.0.

Tectonic setting

114 km

from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes this far from a boundary happen on faults inside a plate, often less frequently but sometimes strongly.

Depth: shallow

31 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

Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.

Place	Intensity	Reports	Distance
99661<br>0.285	III · Weak	6	75 km
99612<br>0.311	III · Weak	3	147 km
99571<br>0.330	V · Moderate	1	131 km
99507<br>0.330	III · Weak	1	921 km
99515<br>0.330	III · Weak	1	914 km
99508<br>0.330	III · Weak	1	924 km

I felt it — report to USGS ↗

USGS PAGER estimate

Who was exposed to shaking

Modelled from the ShakeMap and population data. Alert level green: low likelihood of casualties and damage.

III · Weak shaking: 1,700 people

Estimated shaking in nearby towns

Sand PointPopulation 976IV · Light

After the main event

Aftershocks within 75 km

USGS lists 905 M2.5+ earthquakes within 75 km in the following 30 days; the largest was M5.1 on October 30, 2020. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.

Time after the mainshock on a logarithmic scale (first hours stretched), magnitude on the vertical axis. M2.5+ events from USGS.

Regional history

Past M5+ earthquakes within 300 km

USGS lists 341 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:

History · NOAA

Deadliest earthquakes in this area

NOAA’s significant-earthquake database lists 9 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 168 recorded deaths. The most severe:

1946M8.6
Unimak Island
1 Apr 1946 · 246 km away · intensity VI
168 deaths$26 million damagetsunami
2020M7.8
Alaska
22 Jul 2020 · 84 km away · intensity VII
Limited damage (under $1M)tsunami
1938M8.2
Alaska
10 Nov 1938 · 117 km away · intensity VI
tsunami
1788M8.0
Alaska Peninsula
6 Aug 1788 · 75 km away
tsunami
2020M7.6
Alaska
19 Oct 2020 · 31 km away · intensity IX
tsunami
1948M7.5
Alaska Peninsula
14 May 1948 · 84 km away

NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.

Nearby trackers