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  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

HOW WERE THE SAN GABRIEL MOUNTAINS UPLIFTED? KIM GLOERSEN 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 Compressional zones and thrust faulting. North-south cross section of the San Gabriel Mountains

REFERENCES Atwater, Tanya. "Implications of Plate Tectonics for the Cenozoic Tectonic Evolution of Western North America." Geological Society of America Bulletin (1970): Print. "Geology of the San Gabriel Mountains, Transverse Ranges Province." Western Region Geology and Geophysics Science Center. Western Earth Surface Processes Team, 26 May Web. 15 June 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 Web. 15 June Phillips, Donna E. "Geology of the San Gabriel Mountains, Transverse Ranges Province." Western Region Geology and Geophysics Science Center. USGS, 1 Jan Web. 15 June 2013.

RELATIONSHIP BETWEEN THE SANTA MONICA, HOLLYWOOD, AND RAYMOND FAULTS. BY DIEGO FURTADO

 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

▼ ▼ ▼ ~900 A.D ~800 A.D. ~1000 A.D – – 7.0 Santa Monica fault connects with Hollywood fault at west Beverly Hills Lineament Hollywood fault likely connects to Raymond fault at Los Angeles River floodplain 0.27 – – km 15 km 26 km

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 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 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.

HOW ARE WE “BLIND” TO SOME OF OUR FAULTS? HANNAH SHAMLOO

BLIND THRUST FAULTS Some faults do not break through the surface anywhere along their length

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

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 Web. 18 June Maugh II, Thomas H. (May 26, 2005). "Big Fault Under L.A. Could Be Devastating". Los Angeles Times 26 May Web. 18 Jan. 2013"Big Fault Under L.A. Could Be Devastating" 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 Web. 18 Jan

HOW THE 1971 SAN FERNANDO AND THE 1994 NORTHRIDGE EARTHQUAKES COMPARE MIGUEL FRIAS-RODRIGUEZ

COMPARING TWO THE EARTHQUAKES SAN FERNANDO 1971NORTHRIDGE 1994

SAN FERNANDO EARTHQUAKE (1971)

NORTHRIDGE EARTHQUAKE (1994)

REFERENCES Abridged from Seismicity of the United States, (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.Scott Harrison U.S. Department of the InteriorU.S. Department of the Interior | U.S. Geological Survey URL: Geological Surveyhttp://pubs.usgs.gov/of/1996/ofr /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 , 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 MIGUEL VILLASANA

fault-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, Web

LOS ANGELES, A CITY OF FAULTS MATT RIEMAN Los Angeles: A City of Faults

Faults in Los Angeles

Freeways cross faults in many locations creating potential risk. Collapse of freeway bridges during the Northridge earthquake caused widespread recognition of the hazard. Effect on Infrastructure

- 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 MNG Interactive. Photograph. Web. 20 Jun Uuuuuuu iiiiiiiiiiiiiiiiiii. Elle, Alli. Texture 79. Photograph. Deviant Art. Web. 20 Jun La Brea Tar Pits March Photograph. Web. 20 Jun uuuuuuu. Los Angeles Skyline. Photograph. Web. 20 Jun Uuuuuuu. Northridge Earthquake. Photograph. Natural Disaster Atlas of the United States. Web. 20 u uuuuuuuJun Sheibley, Mari. LA at Night Photograph. Web. 20 Jun Weber, Betsy. La Brea Tar Pits Photograph. Flickr. Web. 20 Jun