Faults of the Los Angeles Field Trip. Faults of the Los Angels Field trip. How were the San Gabriel Mountains uplifted? –Kim Gloersen How the Raymond, Hollywood, and Santa Monica faults are related? –Diego Furtado How are we “blind” to some of our faults? – Hannah Shamloo
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Faults of the Los Angeles Field Trip
How were the San Gabriel Mountains Uplifted?
One mountain said to the other across the rift "Hey, it's not my fault!"
The “big bend” of the San Andreas fault causes compression that pushes up the Transverse Ranges.
Perspective of Big Bend compressional areas, with the addition of thrust faulting from the Sierra Madre.
Compressional zones and thrust faulting.
North-south cross section of the San Gabriel Mountains
Relationship between the santamonica, hollywood, and raymond faults.
BY DIEGO FURTADO
TRANSVERSE RANGES FAULT SYSTEM
RAYMOND, SANTA MONICA, AND HOLLYWOOD FAULTS
SANTA MONICA HOLLYWOOD RAYMOND
▼ ▼ ▼
TYPE OF FAULT : Left-reverse Left-reverse Left-lateral (minor reverse)
~900 A.D ~800 A.D. ~1000 A.D
6.0 - 7.0 5.8 – 6.5 6.0 – 7.0
SLIP RATE (mm/yr):
0.27 – 0.39 0.33 – 0.75 0.10 - 0.22
40 km 15 km 26 km
HOW ARE we “BLIND” TO some of our faults?
Compared to Northridge…
Northridge’s E.Q. directed strongest shaking towards N to sparsely populated mountains
PHT fault focuses its shaking toward downtown LA
LA Basin amplifies shaking
15x stronger energy release
Viz Credits: AmitChourasia
How the 1971 San Fernando and the 1994 Northridge earthquakes compare
SAN FERNANDO 1971
Abridged from Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.r earthquake [updated]
Posted By: Scott Harrison Posted On: 12:25 a.m. | February 9, 2011, PHOTOGRAPH BY: BRUCE COX / LOS ANGELES TIMES.
U.S. Department of the Interior | U.S. Geological Survey URL: http://pubs.usgs.gov/of/1996/ofr-96-0263/execsum.htm
Bolt, Bruce A. (1971). The San Fernando Valley, California, Earthquake of February 9, 1971: Data on Seismic Hazards. Bulletin of the Seismological Society of America, Vol. 61, No. 2, pp. 501-510, Figure 2.
R. S. Stein, G. C. P. King and J. Lin, Stress triggering of the 1994 M 6.7 Northridge , California, Earthquake by its Predecessors.
How Fault Features are expressed in an urban Environment
Newton, Damien, “Rest In Peace: Santa Monica Blvd. Subway”. Wednesday, Oct 19,2011. Web
Braid, Barbara, “What are the three types of Earthquakes Faults?”, Jan23, 2010. Web
Los Angeles: A City of Faults
Los Angeles, A City of Faults
Faults in Los Angeles
Effect on Infrastructure
- Faults run throughout the LA basin
Blind thrust faults such as the PuenteHills fault are particularly dangerous
-Skyscrapers are not designed for all possible motions and still have the potential to collapse during specific (and uncommon) motions