The December 15, 1988 earthquake
M5.0near Morongo Valley, CA
A magnitude 5.0 earthquake 4.3 miles deep, centred in Riverside County. The 439th strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 6.0 on July 8, 1986. 9 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.0
- local magnitude (ml)
- Depth
- 4.3 mi
- 6.9 km below the surface
- Local time
- Thursday, December 15, 1988
- 21:53 PST; 05:53 UTC on Dec 16, 1988
- In California’s record
- 439th
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event ci651401 (“12km SW of Morongo Valley, 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.
9
Aftershocks in 30 days
2.8
Largest aftershock, Dec 17, 1988
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
- Riverside CountyCA · inside
- San Bernardino CountyCA · 14.3 mi
- Orange CountyCA · 47.5 mi
- San Diego CountyCA · 48.8 mi
Cities, largest first
- RiversideCA · 40.9 mi
- San BernardinoCA · 36.9 mi
- FontanaCA · 45.7 mi
- Moreno ValleyCA · 30.3 mi
- MenifeeCA · 35.1 mi
- TemeculaCA · 42.4 mi
- MurrietaCA · 40.5 mi
- Jurupa ValleyCA · 45.1 mi
- RialtoCA · 41.7 mi
- HesperiaCA · 46.3 mi
- IndioCA · 30.7 mi
- HemetCA · 24.8 mi
Earthquakes around the epicentre
3,230 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 21, 1918M6.7
- July 22, 1923M6.2
- May 15, 1910M6.0
- December 4, 1948M6.0
- March 25, 1937M6.0
- July 8, 1986M6.0
- April 3, 1926M5.5
- February 25, 1980M5.3
- May 17, 1940M5.3
- September 19, 1907M5.3
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.