The June 24, 1939 earthquake
M5.2near Rosarito, B.C., MX, California
A magnitude 5.2 earthquake 3.7 miles deep, 39.9 miles off San Diego County. The 305th strongest in California’s record since 1900, and the strongest within 50 miles in the catalogue, which runs from 1900. 9 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.2
- local magnitude (ml)
- Depth
- 3.7 mi
- 6.0 km below the surface
- Local time
- Saturday, June 24, 1939
- 08:27 PST; 16:27 UTC
- In California’s record
- 305th
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event ci3365037 (“54km WSW of Rosarito, B.C., MX”). 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.
9
Aftershocks in 30 days
3.3
Largest aftershock, Jun 25, 1939
7
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.
- 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 Diego CountyCA · 39.9 mi
Cities, largest first
- Chula VistaCA · 48.8 mi
- National CityCA · 48.3 mi
- Imperial BeachCA · 41.9 mi
- CoronadoCA · 46.1 mi
Earthquakes around the epicentre
186 earthquakes of magnitude 3 or more within 50 miles of this epicentre since 1973.
No earlier earthquake of magnitude 5 or more within 50 miles in the catalogue since 1900.
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.