The November 3, 1977 earthquake
M6.7near Adak, Alaska
A magnitude 6.7 earthquake 20.5 miles deep, 10.2 miles off Aleutians West Census Area. The 126th strongest in Alaska’s record since 1900, and the strongest within 50 miles since a magnitude 6.9 on February 6, 1971. 1 aftershock of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 6.7
- surface-wave magnitude (ms)
- Depth
- 20.5 mi
- 33.0 km below the surface
- Local time
- Thursday, November 3, 1977
- 22:52 BST; 09:52 UTC on Nov 4, 1977
- In Alaska’s record
- 126th
- strongest of 124,625 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event usp0000rc6 (“52 km ESE of Adak, Alaska”). The USGS event page carries the ShakeMap, felt reports and the official summary.
Aftershocks
Earthquakes of magnitude 2.5 or more within 20 miles of the epicentre in the 30 days after.
1
Aftershocks in 30 days
5.6
Largest aftershock, Nov 5, 1977
0
On the first day
0
In the 7 days before
- The search radius is the surface rupture length expected for an earthquake of this magnitude (Wells and Coppersmith, 1994), at least 20 and at most 600 miles, so a great earthquake's sequence is counted along its whole fault.
Counties and cities within 50 miles
Distance from the epicentre to each county boundary (zero when inside) and to each city centre.
Counties
- Aleutians West Census AreaAK · 10.2 mi
Earthquakes around the epicentre
3,193 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
Earlier earthquakes of magnitude 5 or more within 50 miles, strongest first
- March 9, 1957M8.6
- February 13, 1905M7.6
- March 14, 1957M7.1
- October 13, 1926M6.9
- February 6, 1971M6.9
- June 12, 1957M6.8
- March 19, 1957M6.8
- December 10, 1905M6.7
- January 5, 1961M6.5
- July 16, 1914M6.5
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.