Re: The Santa Monica Fault
Posted by Don in Hollister on April 04, 2001 at 00:03:41:

Hi Todd. I think this is what you’re looking for. Take Care…Don in creepy town.

The experts’ most compelling message was the likelihood and magnitude of an earthquake this area can expect. Both James Slosson and Tom Heaton noted that the Newport-Inglewood fault is more likely to affect Santa Monica than the San Andreas Fault, and is likely to produce a 6.5 to 7.5 magnitude earthquake.
They noted the Malibu-Santa Monica fault is capable of producing significant damage to Santa Monica much like the Whittier Narrows fault produced in Whittier.

Both scientists discussed ground acceleration and the fact that such measurements of energy released are not an accurate parameter upon which to base a prediction as to a building’s ability to withstand ground motion. Slosson noted that ground accelerations experienced at the epicenter of an earthquake remain fairly constant for a distance of 10 kilometers then drop off sharply as they get farther from the epicenter (see the Ground Acceleration Chart as Attachment G). Slosson pointed out that Santa Monica will experience ground accelerations of 40% of gravity when the northern sector of the Newport-Inglewood fault ruptures. Heaton thought the range would be in excess of 33% of gravity and probably it will be closer to 66% of gravity.

Robert Kovach discussed his belief that Santa Monica is not at risk from the San Andreas or the Malibu-Santa Monica faults but is from the Newport-Inglewood. He also noted that he disagrees with the State of California Division of Mines and Geology that the Newport-Inglewood is capable of a 7-magnitude earthquake but believes it could produce only a 6 "plus" magnitude. He stated Santa Monica has experienced ground accelerations of 5-13% of gravity and that because Santa Monica buildings have withstood those ground accelerations they are likely to withstand any ground accelerations in the future. He concluded that there is no need for a retrofitting program.


TYPE OF FAULT: left-reverse
LENGTH: 24 km

NEARBY COMMUNITIES: Pacific Palisades, Westwood, Beverly Hills, Santa Monica

MOST RECENT SURFACE RUPTURE: Late Quaternary

SLIP RATE: between 0.27 and 0.39 mm/yr

INTERVAL BETWEEN MAJOR RUPTURES: unknown

PROBABLE MAGNITUDES: MW6.0 - 7.0 (?)

OTHER NOTES: This is a north-dipping fault. Its slip rate may be greatest at its western end.