The July 20, 2012 earthquake
M5.2near Ferndale, California
A magnitude 5.2 earthquake 3.6 miles deep, 48.6 miles off Humboldt County. The 354th strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 5.9 on February 4, 2010. 3 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.2
- moment magnitude (mw)
- Depth
- 3.6 mi
- 5.9 km below the surface
- Local time
- Friday, July 20, 2012
- 23:04 PDT; 06:04 UTC on Jul 21, 2012
- In California’s record
- 354th
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event nc71819471 (“92 km WSW of Ferndale, California”). 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.
3
Aftershocks in 30 days
3.5
Largest aftershock, Jul 23, 2012
2
On the first day
1
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
- Humboldt CountyCA · 48.6 mi
Earthquakes around the epicentre
1,864 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
- January 22, 1923M7.1
- February 9, 1941M6.8
- April 26, 1992M6.6
- January 9, 2010M6.5
- October 3, 1941M6.5
- April 26, 1992M6.5
- November 26, 1976M6.3
- October 7, 1951M6.0
- June 5, 1960M6.0
- March 18, 1910M6.0
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.