The December 3, 1938 earthquake
M5.5near Mammoth Lakes, CA
A magnitude 5.5 earthquake 3.7 miles deep, centred in Mono County. The 214th strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 5.5 on February 9, 1934. 5 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.5
- local magnitude (ml)
- Depth
- 3.7 mi
- 6.0 km below the surface
- Local time
- Saturday, December 3, 1938
- 09:42 PST; 17:42 UTC
- In California’s record
- 214th
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event ci3364810 (“32km E of Mammoth Lakes, CA”). 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.
5
Aftershocks in 30 days
4.7
Largest aftershock, Dec 3, 1938
4
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
- Mono CountyCA · inside
- Fresno CountyCA · 16.0 mi
- Inyo CountyCA · 16.8 mi
- Mineral CountyNV · 18.6 mi
- Esmeralda CountyNV · 18.9 mi
- Madera CountyCA · 23.0 mi
- Tuolumne CountyCA · 33.4 mi
- Mariposa CountyCA · 38.7 mi
Earthquakes around the epicentre
4,080 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 30, 1934M6.3
- November 21, 1910M6.1
- May 6, 1910M6.0
- September 17, 1927M5.9
- January 30, 1934M5.6
- January 4, 1912M5.5
- November 21, 1910M5.5
- February 9, 1934M5.5
- November 18, 1910M5.5
- February 1, 1934M5.4
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.