Magnitude 4.2 near West Hollywood, CA
Sunday, September 9, 2001 at 4:59:17 PM (PDT)
Special Earthquake Report
Egill Hauksson and Kate Hutton, Caltech, Lucy Jones, USGS. See
also TriNet.
A M4.2 earthquake occurred in West Hollywood
California at 4:59 pm (local time) September 9, 2001. This earthquake was
widely felt throughout the Los Angeles Basin and in parts of San Fernando
Valley and was well recorded by the Caltech-USGS TriNet. The focal depth of
this earthquake was about 4 km, making the shaking most severe in the Hollywood
basin. No significant damage has been reported. This is the largest earthquake
to occur in the Los Angeles basin since the 1994 Mw6.7 Northridge earthquake
and its aftershocks.
During the last two weeks a north-northwest trending cluster
of seismicity preceded the M4.2 earthquake. This cluster crossed the epicentral
area of the M4.2 extended from Inglewood in the south, to Northridge in the
north. These quakes had magnitudes in the range from M1.3 to M2.0. This earthquake
is located near the intersection of the Newport-Inglewood and Hollywood faults.
The focal mechanism showed horizontal strike-slip motion on a north-northwest
striking plane, suggesting that this event may be associated with the north
end of the Newport-Inglewood fault. The Los Angles basin has north-northwest
trending strike-slip faults at shallow depth and east-west trending thrust
faults at depths greater than 6 to 8 miles. This earthquake differs from of
the deep thrust faulting earthquake sequences recorded over the last two decades
in the Los Angeles area such as 1987 M5.9 Whittier Narrows and 1994 M6.7 Northridge.
The occurrence of this earthquake cluster suggest activation of the more shallow
strike-slip regime of fault s in the Los Angeles basin, which has mostly remained
dormant over the last decade.
The M4.2 has so far been followed by the following aftershocks:
| MAG |
DATE
y/m/d |
LOCAL-TIME
h:m:s |
LAT LON
deg deg
|
DEPTH
km |
LOCATION |
| 1.8 |
2001/09/09 |
17:25:27 |
34.047N 118.391W |
11.5 |
3 km (2 mi) ESE of Century City, CA |
| 2.0 |
2001/09/09 |
17:06:22 |
34.084N 118.390W |
6.3 |
1 km (1 mi) E of West Hollywood, CA |
| 2.8 |
2001/09/09 |
17:01:01 |
34.078N 118.396W |
3.1 |
1 km (1 mi) SSE of West Hollywood, CA |
| 4.2 |
2001/09/09 |
16:59:17 |
34.075N 118.379W |
3.7 |
2 km (1 mi) ESE of West Hollywood |
Information about the earthquake and its location
Map showing location of the earthquake and nearby earthquakes
Updated hourly for six days after the earthquake. Includes this event and (up
to) the first 6 days of aftershocks, if any
Shake Map
Preliminary map of shaking intensity based on measurements by seismic networks.
Usually available within 5 minutes after the earthquake.
Did
You Feel It?
Report shaking and damage at your location. You can also view a map displaying
accumulated data from your report and others.
Waveforms
Waveform for
this Event
Topographic Map for this Area
There will be a red X at the earthquake epicenter.
(Note: Takes you off this site.) California
Office of Emergency Services
(Note: Takes you off this site.)
As additional information becomes available, it will be posted here.
Version #1: This report supersedes any earlier reports of this event.
Southern California Seismic Network: a cooperative project of
U.S. Geological Survey, Pasadena California
Caltech Seismological Laboratory, Pasadena, California
| 
