MONTHLY DINNER MEETING
Date: Tuesday, March 11, 2003
Location: Steven's Steak House,
5332 Stevens Place, Commerce, CA
Time: 5:30 p.m. - Social Hour;
7:00 p.m. – Dinner;
8:00 p.m. – Presentation
Cost: $20 per person with reservations, $25 at the door.
Reservations: Call (949) 253-5924 ext. 564, or email Brian Villalobos,
12:00 p.m., March 7, 2003
SPEAKER: Dr. Jeffrey (Jeff) Keaton
TITLE: Earthquake Ground Motion for Design of the Hoover Dam
Bypass Bridge (US Highway 93)
The Hoover Dam Bypass Project is a 3.5-mile corridor on U.S. Highway 93 in Clark County,
Nevada, and Mohave County, Arizona, crossing the Colorado River approximately 1,500 feet
downstream of Hoover Dam. The proposed bridge will be 1,896 feet long and 88 feet wide.
The main span will be a Composite Concrete Deck Arch Bridge with an overall length of 1,090 feet.
Five approach spans on the Nevada side and two on the Arizona side range in length from 100 to 120
feet. Seventeen faults within 100 miles of the site were considered to be active. Maximum earthquake
magnitudes were determined for each active fault, and peak horizontal accelerations were estimated
using three ground-motion attenuation relationships. The results of a probabilistic seismic hazard
assessment published by the US Geological Survey in 1996 were used, in part, to select earthquake
magnitudes and distances, and target ground motions for use in design of the main Colorado River
bridge and the approach bridges. The Colorado River bridge was designed on the basis of a nonlinear
dynamic analysis using three-component seismograms at each abutment. The approach bridges were
designed on the basis of a response spectrum analysis. The river bridge will be a flexible structure
with a fundamental period longer than 1 s. A 1-s spectral acceleration of 0.139 g was selected as
the target ground motion on which to anchor design earthquakes and response spectra. The target 1-s
spectral acceleration would be produced by a moment magnitude earthquake of 6.2 at a hypocentral
distance of 16 km, or by a moment magnitude earthquake of 7.0 at a hypocentral distance of 36 km.
The magnitude 6.2 earthquake would likely occur on the Mead Slope fault, whereas the magnitude 7.0
earthquake would occur on the California Wash fault.
Jeffrey R. Keaton is a Principal Engineering Geologist and Vice President in the Anaheim office of AMEC
Earth & Environmental, Inc. His education consists of a BS degree in Geological Engineering from the
University of Arizona (1971), a MS degree in Engineering (Geotechnical) from the University of California,
Los Angeles (1972), and a PhD degree in Geology from Texas A&M University (1988). He is registered as a
Professional Engineer in California, Utah, Alaska, and Arizona. He is also registered as a Professional
Geologist in California and Arizona, and certified as an Engineering Geologist in California and Washington.
Dr. Keaton was employed by Dames & Moore in Los Angeles (1970-1979) and Salt Lake City (1979-1988).
He was employed by Sergent, Hauskins & Beckwith (which became AGRA Earth & Environmental, and then AMEC
Earth & Environmental) in Salt Lake City (1988-1996), Phoenix (1996-2001), and currently in Anaheim.
He served as Chairman of the Utah Section of the Association of Engineering Geologists in 1980-1982 and
was the President of AEG in 1992-1993. He served as Chairman of the Engineering Geology Division of the
Geological Society of America in 1989-1990. He served as Chairman of the Transportation Research Board
Committee on Engineering Geology (A2L05) from 1991 to 1997, and as Chairman of TRB Committee on Exploration
and Classification of Earth Materials (A2L01) from 1997 to 2002. He also served as the Chairman of TRB
Subcommittee on Scour Research (A2L05-2). In 2002, he became the Chairman of TRB Section L, housing the
six committees that deal with Geology and Properties of Earth Materials. Dr. Keaton also is a member of
American Geophysical Union, American Society of Civil Engineers, Earthquake Engineering Research Institute,
and Seismological Society of America. Dr. Keaton specializes in quantification of hazardous natural
processes for use in design and risk analysis. He has written numerous articles regarding engineering
geology mapping, debris flows, landslides, collapsible soils, subsidence, fault rupture, earthquake induced
liquefaction, earthquake ground motion, and case histories.