Faults of Los Angeles Field Trip

The Faults of Los Angeles: The Danger Beneath Our Feet

In the past, the Southern California Earthquake Center (SCEC) interns have been led on a field trip through Los Angeles by Dr. James Dolan, a professor of Earth Sciences at the University of Southern California (USC). The city of Los Angeles was built atop an intricate network of faults, many of which are capable of producing large earthquakes. These faults, therefore, pose a threat to the millions of people that live in Los Angeles and the surrounding region. As the interns travel around the Los Angeles area, Dr. Dolan shows them evidence of these potentially dangerous faults and some of the measures being taken to prevent widespread damage in the event of an earthquake.

The first stop of the trip is the Griffith Observatory that gives the interns a great view of the Los Angeles Basin and its topography. This backdrop provides Dr. Dolan with a concrete example to help the interns understand the various fault types in the basin. Here, Dr. Dolan describes the sedimentary basin of LA as a bowl of Jell-O that when disturbed will continue shaking, much like LA during an earthquake. Los Angeles is home to every type of fault possible: both left and right strike slip, normal, reverse, and oblique faulting.

The second stop of the trip is located in downtown Hollywood at the corner of Hollywood and Vine. Looking north from the corner of the two streets, the interns can see the fault scarp created by the Hollywood fault that lies just below the Capitol Records Building. The hill here was created by past earthquakes that caused the northern side of the fault to push upward over the southern side.

After traveling along Hollywood Boulevard, the next stop is Runyon Canyon Park. This location is ideal for Professor Dolan to continue his lecture on the effects of the Hollywood fault. Surrounded by the uplifted Hollywood hills, Professor Dolan explains that they were formed because of a left step in the Hollywood Fault. This feature of the left lateral fault caused pressure to focus on a single area, which pushed the earth up, creating the hills that the interns stood on.

The next stop is Lacy Park, located in San Marino, California. Lacy Park is 1.5 miles east of Raymond Hill and sits on top of the Raymond Fault. Dr. Dolan explains that there is a bend in the Raymond Fault which creates a depression in the center of Lacy Park. This bend causes the strike slip fault to separate and form a pull-apart basin. In the late 1800s, Lacy Park was known for Wilson Lake, but since then the lake has been drained.

The final stop is near NASA's Jet Propulsion Lab and the San Gabriel Mountains.  These mountains were created by the Sierra Madre Fault. Professor Dolan explains that the fault has an average 45 degree dip that can be seen in an exposure on the surface creating about 1 millimeter of slip per year. According to Professor Dolan, the fault has ruptured twice in the past 20,000 years with a minimum of 11 meters of slip in the first rupture and a minimum of 4 meters in the second.

The interns will learn about crucial information that they can use for their projects. Thank you to Professor Dolan for his wisdom and guidance; this field trip is always a great success.  It is indeed a long and tiring trip, but the interns always leave with a broader awareness of their surroundings and the groud underneath their feet.

Written by: Hannah Potter, Elena Soto, Bryce Walters, JaKayla Walker, Aurelio Valencia, Kelsey Brunner, and Samuel Lauda

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