The October 18, 1984 earthquake
M5.3near Esterbrook, Wyoming
A magnitude 5.3 earthquake 20.5 miles deep, centred in Albany County. The 7th strongest in Wyoming’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900. 7 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.3
- moment magnitude (mw)
- Depth
- 20.5 mi
- 33.0 km below the surface
- Local time
- Thursday, October 18, 1984
- 09:30 MDT; 15:30 UTC
- In Wyoming’s record
- 7th
- strongest of 1,557 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event usp0002899 (“29 km W of Esterbrook, Wyoming”). 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.
7
Aftershocks in 30 days
4.5
Largest aftershock, Oct 18, 1984
2
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
- Albany CountyWY · inside
- Converse CountyWY · 5.4 mi
- Carbon CountyWY · 18.5 mi
- Natrona CountyWY · 18.6 mi
- Platte CountyWY · 27.2 mi
- Niobrara CountyWY · 45.2 mi
Cities, largest first
- CasperWY · 44.5 mi
Earthquakes around the epicentre
24 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
No earlier earthquake of magnitude 5 or more within 50 miles in the catalogue since 1900.
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.