Magnitude 4.4 - GREATER LOS ANGELES AREA, CALIFORNIA
2010 March 16 11:04:00 UTC
- This event has been reviewed by a seismologist.
|Depth||18.9 km (11.7 miles)|
|Region||GREATER LOS ANGELES AREA, CALIFORNIA|
|Distances||15 km (10 miles) ESE of Los Angeles, California|
20 km (10 miles) SSE of Pasadena, California
25 km (15 miles) NNE of Long Beach, California
595 km (370 miles) SSE of SACRAMENTO, California
|Location Uncertainty||horizontal +/- 0.3 km (0.2 miles); depth +/- 0.6 km (0.4 miles)|
|Parameters||Nph=177, Dmin=6 km, Rmss=0.39 sec, Gp= 22°,|
M-type=local magnitude (ML), Version=4
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This earthquake occurred in the fold and thrust belt located on the east side of the Los Angeles Basin. The preliminary focal depth was 19 km (~12 miles), which is deeper than most earthquakes in the region. The earthquake was located ~7 km south of the hypocenter of the 1 October 1987 ML5.9 Whittier Narrows earthquake.
Both today's earthquake and the 1987 Whittier mainshock exhibited thrust faulting. However, the strike of the nodal planes was east-west in 1987 but for today's earthquake the strike was rotated clockwise by ~30deg to N60degW, suggesting that a different thrust system was being activated. This earthquake may have been associated with the Puente Hills thrust.
The most recent significant earthquake sequence in the Los Angeles basin was the M4.7 Inglewood event on 18-May-2009, however a larger M5.4 Chino Hills earthquake occurred on 29-Jul-2008. The Chino Hills earthquake that was most likely caused by movement on the Whittier fault exhibited a mixture of strike-slip and thrust faulting.
The Pico Rivera earthquake is similar to the pair of earthquakes of M4.8 and M4.5 located near Montebello (10 km (6 miles) to the west) on June 12th 1989 at 15.5 km depth. Both exhibited thrust faulting.
Surface faulting has not been observed and is not expected for an earthquake of this magnitude.