The April 26, 1997 earthquake
M5.1near Piru, California
A magnitude 5.1 earthquake 9.9 miles deep, centred in Los Angeles County. The 421st strongest in California’s record since 1900, and the strongest within 50 miles since a magnitude 5.2 on March 20, 1994. 31 aftershocks of magnitude 2.5 or more followed within 30 days.
Watch the sequence unfoldMagnitude 5.1 · April 26, 1997
How the ground moved
Every recorded earthquake in the sequence, in order, from the foreshocks to a month after.
The earthquake
- Magnitude
- 5.1
- local magnitude (ml)
- Depth
- 9.9 mi
- 15.9 km below the surface
- Local time
- Saturday, April 26, 1997
- 03:37 PDT; 10:37 UTC
- In California’s record
- 421st
- strongest of 97,065 since 1900
USGS ANSS Comprehensive Earthquake Catalog, event ci9008753 (“12km ESE of Piru, 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.
31
Aftershocks in 30 days
4.9
Largest aftershock, Apr 27, 1997
12
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
- Los Angeles CountyCA · inside
- Ventura CountyCA · 5.7 mi
- Kern CountyCA · 31.4 mi
- Santa Barbara CountyCA · 44.3 mi
- Orange CountyCA · 49.3 mi
Cities, largest first
- Los AngelesCA · 28.3 mi
- Long BeachCA · 49.8 mi
- Santa ClaritaCA · 10.2 mi
- OxnardCA · 32.8 mi
- GlendaleCA · 27.5 mi
- LancasterCA · 36.0 mi
- PalmdaleCA · 35.6 mi
- TorranceCA · 41.3 mi
- PasadenaCA · 33.6 mi
- Simi ValleyCA · 8.4 mi
- Thousand OaksCA · 16.8 mi
- VenturaCA · 34.1 mi
Earthquakes around the epicentre
1,055 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 21, 1952M7.5
- January 17, 1994M6.7
- February 9, 1971M6.6
- October 22, 1916M6.0
- October 1, 1987M5.9
- January 17, 1994M5.9
- July 21, 1952M5.8
- February 9, 1971M5.8
- February 9, 1971M5.8
- June 28, 1991M5.8
USGS ANSS Comprehensive Earthquake Catalog. Local time is the time zone of the county nearest the epicentre. Magnitudes are as the catalogue reports them.