The October 1, 1969 earthquake
M5.3near Bloomfield, California
A magnitude 5.3 earthquake 9.3 miles deep, centred in Sonoma County. The 298th strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 5.3 on March 22, 1957. 1 aftershock of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.3
- moment magnitude (mw)
- Depth
- 9.3 mi
- 15.0 km below the surface
- Local time
- Wednesday, October 1, 1969
- 21:56 PDT; 04:56 UTC on Oct 2, 1969
- In California’s record
- 298th
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event iscgem803001 (“3 km E of Bloomfield, 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
5.3
Largest aftershock, Oct 2, 1969 · its page
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
- Sonoma CountyCA · inside
- Marin CountyCA · 5.5 mi
- Napa CountyCA · 18.4 mi
- Solano CountyCA · 24.5 mi
- Lake CountyCA · 26.4 mi
- Contra Costa CountyCA · 31.7 mi
- Mendocino CountyCA · 37.0 mi
- San Francisco CountyCA · 37.6 mi
- Alameda CountyCA · 39.2 mi
- Yolo CountyCA · 40.4 mi
- San Mateo CountyCA · 45.1 mi
- Colusa CountyCA · 49.1 mi
Earthquakes around the epicentre
1,232 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
- April 18, 1906M7.9
- May 19, 1902M5.4
- March 22, 1957M5.3
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.