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

How the 1971 San Fernando and the 1994 Northridge earthquakes compare? –Miguel
Frias-Rodriguez

How are fault features expressed in an urban environment? – Miguel Villasana

How is Los Angeles a city of faults? - Matt Rieman
One mountain said to the other across the
rift "Hey, it's not my fault!"
PLATE MOVEMENTS
 30 Ma. , subductive
tectonic movements
occurred between the
Farallon, North American,
and Pacific plates.
 20 Ma. the relative
movements of the North
American and the Pacific
Plate changed from a head
on head contact with the
Farallon Plate to a lateral
slipping against each other.
THE BIG BEND
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.
THRUST FAULTING
North-south cross section of the San
Gabriel Mountains
Compressional zones and thrust faulting.
REFERENCES
Atwater, Tanya. "Implications of Plate Tectonics for the Cenozoic Tectonic Evolution of
Western North America." Geological Society of America Bulletin 81.12 (1970): 3513536. Print.
"Geology of the San Gabriel Mountains, Transverse Ranges Province." Western Region
Geology and Geophysics Science Center. Western Earth Surface Processes Team, 26
May 2006. Web. 15 June 2013.
Masters, Nathan. "Rise of the Sierra Madre: A Brief History of the San Gabriel Mountains |
LA as Subject | SoCal Focus | KCET." KCET. KCET, 30 May 2012. Web. 15 June 2013.
Phillips, Donna E. "Geology of the San Gabriel Mountains, Transverse Ranges Province."
Western Region Geology and Geophysics Science Center. USGS, 1 Jan. 1990. Web. 15
June 2013.
 The “BIG BEND”: Cause of
Compression between the Pacific
Plate and North American Plate
 Mountains and faults are formed:
San Gabriel Mountains and
Santa Monica Mountains
 Transverse Range Southern
Boundary Fault System: Extends
from east to west unlike other
California mountains
 Base of San Gabriel and Santa Monica Mountains
 West- trending system of faults that extends for 200 km
 Oblique-slip, reverse-slip, and strike-slip
▼
▼
▼
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
0.27 – 0.39
0.33 – 0.75
40 km
15 km
0.10 - 0.22
26 km
• Santa Monica fault connects with Hollywood
fault at west Beverly Hills Lineament
• Hollywood fault likely connects to Raymond
fault at Los Angeles River floodplain
•
•
•
•
•
•
http://geomaps.wr.usgs.gov/archive/scamp/html/scg_flt.html
http://qcode.us/codes/malibu-general-plan/view.php?topic=ii-5_0-5_2-5_2_2&frames=on
http://www.data.scec.org
Kristin D. Weaver, Paleoseismology and Geomorphology of the Raymond Fault,
Los Angeles County, California, Bulletin of the Seismological Society of America
pp. 1409–1429, December 2000, P. 1410-1413.
James F. Dolan, Eldon M. Gath, Lisa B. Grant, Mark Legg, Scott Lindvall, Karl Mueller,
Michael Oskin, Daniel F. Ponti, Charles M. Rubin, Thomas K. Rockwell, John H, Shaw,
Jerome A.Treiman, Chris Walls, and Robert S. Yeats (compiler), P. 1-7.
James F. Dolan, David D. Bowman, and Charles G. Sammis, Data Repository for “Long
range and long term fault intersections in southern California”, Supporting data, references,
and notes for paleo-earthquakes in the Los Angeles region.
BLIND THRUST FAULTS
Some faults do not break through the surface anywhere along their length
http://earthsci.org/processes/struct/equake1/EQCaseHistories.html
PUENTE HILLS THRUST FAULT
Recently discovered, 1999
Los Angeles Basin
Runs about 40 km
Three segments
Slip rate 5mm/year
4 Major E.Q.’s last 11,000
years
http://www.scec.org/research/030404dolan.html
DANGER
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: Amit Chourasia
REFERENCES
Marquis, John. "New Study Reveals The Behavior Of The Puente Hills Thrust
Fault." New Study Reveals The Behavior Of The Puente Hills Thrust Fault.
Southern California Earthquake Center, 4 Apr. 2003. Web. 18 June 2013.
Maugh II, Thomas H. (May 26, 2005). "Big Fault Under L.A. Could Be
Devastating". Los Angeles Times 26 May 2005. Web. 18 Jan. 2013
Shaw, John H., Andreas Plesch, James F. Dolan, Thomas L. Pratt, and Patricia Fore.
"Puente Hills Blind-Thrust System, Los Angeles, California." Thesis. N.d. Bulletin of
the Seismological Society of America, 16 Nov. 2001. Web. 18 Jan. 2013.
COMPARING TWO THE EARTHQUAKES
S A N F E R N A N D O 1 971
NORTHRIDGE 1994
SAN FERNANDO EARTHQUAKE (1971)
NORTHRIDGE EARTHQUAKE (1994)
REFERENCES
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.
http://www.artinaid.com/wp-content/uploads/2013/04/Types-of-Faults.jpg
http://la.streetsblog.org/wp-content/uploads/2011/10/source-westsidefault-lines.jpg
REFERENCES
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
Faults in Los Angeles
Effect on Infrastructure
Freeways cross faults in many locations creating potential
risk.
Collapse of freeway bridges during the Northridge
earthquake caused widespread recognition of the hazard.
- Faults run throughout the LA basin
Blind thrust faults such as the Puente Hills fault are particularly
dangerous
-Skyscrapers are not designed for all possible motions and still have the
potential to collapse during specific (and uncommon) motions
ANOTHER RESULT OF FAULTING
Oil can become trapped along faults
Yet seepage can also occur along faults
Tar pits- Caused by oil seeping up along a fault and degrading to asphalt
Questions?
REFERENCES:
405 Traffic. 2012. MNG Interactive. Photograph. Web. 20 Jun 2013. Uuuuuuu
iiiiiiiiiiiiiiiiiii<http://extras.mnginteractive.com/live/media/site200/2012/0615/2012061
5__405_traffic_01.JPG>.
Elle, Alli. Texture 79. Photograph. Deviant Art. Web. 20 Jun 2013. <http://couch-anduuuuuuucanvas.deviantart.com/art/Texture-79-159359821>.
La Brea Tar Pits March 2010. Photograph. Web. 20 Jun 2013.
uuuuuuu<http://www.thegypsiestownsend.com/2011/03/la-brea-tar-pits-marchiiiiiiiiiiiiiiii2010.html>.
Los Angeles Skyline. Photograph. Web. 20 Jun 2013.
Uuuuuuu<http://www.thewallpapers.org/photo/17314/los_angeles_skyline-003.jpg>.
Northridge Earthquake. Photograph. Natural Disaster Atlas of the United States. Web. 20 u
uuuuuuuJun2013.<http://naturaldisasteratlas.weebly.com/uploads/5/1/2/3/5123992/
938 6727_orig.jpg>.
Sheibley, Mari. LA at Night. 2012. Photograph. Web. 20 Jun 2013.
<http://www.marisheibley.com/post/19185422109/3-11-12-la-at-night>.
Weber, Betsy. La Brea Tar Pits. 2010. Photograph. Flickr. Web. 20 Jun 2013.
<http://www.flickr.com/photos/betsyweber/5301040950/>.