The February 20, 1988 earthquake
M5.1near Tres Pinos, California
A magnitude 5.1 earthquake 5.7 miles deep, centred in San Benito County. The 382nd strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 5.5 on January 26, 1986. 3 aftershocks of magnitude 2.5 or more followed within 30 days.
The earthquake
- Magnitude
- 5.1
- local magnitude (ml)
- Depth
- 5.7 mi
- 9.2 km below the surface
- Local time
- Saturday, February 20, 1988
- 00:39 PST; 08:39 UTC
- In California’s record
- 382nd
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event nc10086194 (“1 km NE of Tres Pinos, 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.
3
Aftershocks in 30 days
3.2
Largest aftershock, Mar 16, 1988
0
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.
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
- Monterey CountyCA · 9.1 mi
- Merced CountyCA · 9.3 mi
- Santa Clara CountyCA · 12.6 mi
- Santa Cruz CountyCA · 16.6 mi
- Fresno CountyCA · 22.1 mi
- Stanislaus CountyCA · 23.9 mi
- Madera CountyCA · 45.2 mi
- San Joaquin CountyCA · 48.2 mi
- Alameda CountyCA · 48.3 mi
Cities, largest first
- San JoseCA · 44.3 mi
- SalinasCA · 19.3 mi
- Santa CruzCA · 41.9 mi
- GilroyCA · 21.0 mi
- WatsonvilleCA · 27.0 mi
- Los BanosCA · 31.9 mi
- HollisterCA · 6.4 mi
- Morgan HillCA · 29.6 mi
- CampbellCA · 48.7 mi
- Los GatosCA · 46.6 mi
- SeasideCA · 30.4 mi
- MontereyCA · 34.4 mi
Earthquakes around the epicentre
2,830 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
- August 2, 1903M6.2
- April 24, 1984M6.2
- May 25, 1905M6.1
- June 11, 1903M6.1
- April 8, 1961M5.9
- July 25, 1926M5.8
- August 6, 1979M5.8
- August 6, 1916M5.8
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.