M7.0 earthquake 114 km WSW of Adak, Alaska

Friday, July 5, 1929, 14:19:09 UTC · 51.459°N, 178.153°W

A magnitude 7.0 earthquake struck 114 km WSW of Adak, Alaska on Friday, July 5, 1929, 14:19:09 UTC, at a depth of 35.0 km (shallow). It is the strongest earthquake within 300 km since an M7.0 on February 6, 1916.

Magnitude: 7.0; Major · 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: 200 km aftershock search area

In context

How big was it, and why here?

Energy released

494 kilotons of TNT

That is about 33 times the Hiroshima bomb. It released about 1,035 times the energy of a magnitude 5.0.

Tectonic setting

108 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

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 10 M2.5+ earthquakes within 200 km in the following 30 days; the largest was M7.3 on July 7, 1929. 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 48 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 2 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700. The most severe:

1906M8.3
Aleutian Islands: Rat Islands
17 Aug 1906 · 257 km away
1905M7.9
Andreanof Islands
14 Feb 1905 · 86 km away

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

Nearby trackers