The September 14, 1963 earthquake
M5.4near Aromas, California
A magnitude 5.4 earthquake 1.9 miles deep, centred in San Benito County. The 229th strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 5.5 on April 8, 1961. 1 aftershock of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.4
- body-wave magnitude (mb)
- Depth
- 1.9 mi
- 3.0 km below the surface
- Local time
- Saturday, September 14, 1963
- 12:46 PDT; 19:46 UTC
- In California’s record
- 229th
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event ushis2622 (“4 km E of Aromas, 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.
1
Aftershocks in 30 days
4.3
Largest aftershock, Sep 14, 1963
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.
- Before the modern seismic networks of the 1970s many small aftershocks went unrecorded, so early sequences read short.
Counties and cities within 50 miles
Distance from the epicentre to each county boundary (zero when inside) and to each city centre.
Counties
- San Benito CountyCA · inside
- Santa Cruz CountyCA · 1.1 mi
- Santa Clara CountyCA · 1.2 mi
- Monterey CountyCA · 3.3 mi
- Merced CountyCA · 20.2 mi
- Stanislaus CountyCA · 21.2 mi
- San Mateo CountyCA · 38.0 mi
- Fresno CountyCA · 38.9 mi
- San Joaquin CountyCA · 41.5 mi
- Alameda CountyCA · 41.6 mi
Cities, largest first
- San JoseCA · 30.5 mi
- FremontCA · 45.9 mi
- SalinasCA · 14.0 mi
- SunnyvaleCA · 41.6 mi
- Santa ClaraCA · 38.6 mi
- Mountain ViewCA · 44.1 mi
- MilpitasCA · 40.9 mi
- Palo AltoCA · 46.1 mi
- Santa CruzCA · 24.9 mi
- GilroyCA · 8.1 mi
- CupertinoCA · 38.6 mi
- WatsonvilleCA · 10.0 mi
Earthquakes around the epicentre
2,771 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
- July 1, 1911M6.5
- October 22, 1926M6.3
- October 22, 1926M6.3
- August 2, 1903M6.2
- June 11, 1903M6.1
- April 8, 1961M5.9
- September 4, 1955M5.8
- August 6, 1916M5.8
- March 10, 1910M5.8
- December 31, 1910M5.7
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.