The September 17, 1991 earthquake
M5.2near San Simeon, California
A magnitude 5.2 earthquake 5.7 miles deep, centred in Monterey County. The 328th strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 5.2 on August 29, 1983. 3 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.2
- local magnitude (ml)
- Depth
- 5.7 mi
- 9.2 km below the surface
- Local time
- Tuesday, September 17, 1991
- 14:10 PDT; 21:10 UTC
- In California’s record
- 328th
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event nc231726 (“22 km NW of San Simeon, 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
3.3
Largest aftershock, Sep 19, 1991
1
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
- Monterey CountyCA · inside
- San Luis Obispo CountyCA · 1.2 mi
- San Benito CountyCA · 35.5 mi
- Fresno CountyCA · 43.5 mi
Cities, largest first
- Paso RoblesCA · 40.4 mi
- AtascaderoCA · 42.7 mi
- SoledadCA · 43.1 mi
- GreenfieldCA · 35.9 mi
- King CityCA · 30.3 mi
- Morro BayCA · 40.3 mi
Earthquakes around the epicentre
1,013 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 2, 1901M6.4
- November 21, 1952M6.2
- June 7, 1934M5.8
- July 25, 1926M5.8
- December 6, 1906M5.7
- August 29, 1983M5.2
- December 28, 1939M5.2
- June 7, 1934M5.1
- February 24, 1972M5.1
- February 26, 1932M5.0
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.