New Document Published To Aid California Cities and Counties In Taking Protective Measures Against Soil Liquefaction

NR #99001
19 April, 1999

New Document Published To Aid California Cities and Counties In Taking
Protective Measures Against Soil Liquefaction

News Conference: A news conference will be hosted by the Southern
California Earthquake Center.

When: Friday, April 23rd, 10 am

Where: University of Southern California
Science Building (SCI)
Room 123
3651 Trousdale Parkway
Los Angeles

Call 213 / 740-0323 for directions and a map.

Who: Report co-authors, selected committee members, and selected local
and state government representatives will make brief statements (2-3
minutes each) and will then answer questions about the report.

LOS ANGELES -- A new document produced by a committee of engineers and
geologists with academic, practicing, and regulatory backgrounds has been
published by the Southern California Earthquake Center (SCEC). "Recommended
Procedures for Implementation of DMG Special Publication 117 - Guidelines
for Analyzing and Mitigating Liquefaction Hazards in California" is
intended to help engineers, geologists and building officials competently
evaluate and take protective measures against the potential liquefaction
hazard in many areas of southern California. Liquefaction is a process
where loose sandy soils below the ground water lose strength due to strong
ground shaking. This liquefaction could result in settlement and ground
movements leading to damage to buildings founded in such soils.

Why was the report written? This report summarizes 18 months of study and
deliberation in response to the California Department of Conservation's
Division of Mines and Geology (CDMG) Special Publication 117 (SP 117),
which presents general guidelines for evaluation and mitigation of
seismically-induced soil liquefaction and landslides. The Seismic Hazards
Mapping Act (SHMA) in California requires that seismic hazards, including
liquefaction, must be evaluated and mitigated, if needed, for all new
construction in the state. The State is also in the process of publishing
maps delineating areas that are believed to be susceptible to both
liquefaction and landslide hazard.

What new information does it contain? The report shows that liquefaction is
sufficiently understood, soil behavior can be predicted in earthquakes, and
the consequences of liquefaction can be predicted. The report has
recommendations for what is an adequate scope of investigation for
evaluating soil liquefaction potential, and the different hazards or
consequences that arise from liquefaction, including settlement, lateral
spreading, flow slides, and loss of bearing capacity. An overview of the
recommended methods of analysis is presented. The report also addresses
the common technologies available to mitigate the effects of liquefaction.
The merits of soil improvement are discussed as well as structural design
for the effects of liquefaction and the inherent risks associated with such
decisions.

How will the report be used? A workshop on use of the report will be
conducted by its authors for city and county officials and consulting
engineers on June 17, 1999. The full-day workshop will include an overview
of the material, a question and answer session, and afternoon sessions for
discussion and feedback. To obtain more information on the workshop, visit
the SCEC Web site at www.scec.org.

More About the report and its authors: With the implementation of the
Seismic Hazards Mapping Act in California, guidelines for evaluating and
mitigating seismic hazards in California were published by the California
Department of Conservation, Division of Mines and Geology in 1997 as
Special Publication 117. Building Officials in the Department of Building
and Safety of the City of Los Angeles and the Department of Public Works of
the County of Los Angeles requested assistance in the development of
standard procedures to implement the requirements of the DMG SP 117
Guidelines and the Seismic Hazards Mapping Act for projects requiring their
review. Cooperation was sought from other agencies in southern California
and officials from the Counties of Riverside, San Bernardino, San Diego,
Orange, and Ventura agreed to participate. In addition, the Division of
Mines and Geology and the Federal Emergency Management Agency lent support
to this effort.

The request was made through the Geotechnical Engineering Group of the Los
Angeles Section of the American Society of Civil Engineers (ASCE) in the
latter part of 1997. A group of practicing geotechnical engineers and
engineering geologists was assembled to form a committee to develop
implementation procedures. It was decided to deal with liquefaction and
landslide hazards separately. The liquefaction implementation committee
was organized through the auspices of the Southern California Earthquake
Center headquartered at the University of Southern California in Los
Angeles.

The committee set out with the task to aid the several counties and many
cities in southern California with the administrative implementation of
SHMA for the evaluation and mitigation of liquefaction hazard and to
provide an overview of analysis techniques and methods of mitigation for
liquefaction hazard. The committee was convened at SCEC, a National Science
Foundation Science and Technology Center in partnership with the US
Geological Survey.

The report is available as of Monday, April 19th through the Southern
California Earthquake Center Outreach office for $10 per copy.

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Liquefaction implementation committee members:

Geoffrey R. Martin (co-chair) Department of Civil Engineering, University
of Southern California, Los Angeles, CA
Marshall Lew (co-chair) Law/Crandall, a Division of Law Engineering and
Environmental Services, Los Angeles, CA
K. Arulmoli Earth Mechanics, Inc., Fountain Valley, CA
Juan I. Baez Hayward Baker, Santa Paula, CA
Thomas F. Blake Fugro West, Inc., Ventura, CA
Ebrahim Simantob R.T. Frankian & Associates, Burbank, CA
T. Leslie Youd Department of Civil and Environmental Engineering, Brigham
Young University, Provo, UT

Local and State Government Liaisons to the committee:

Johnnie Earnest County of Orange, Santa Ana, CA
Fred Gharib County of Los Angeles, Alhambra, CA
J. Goldhammer County of San Diego, San Diego, CA
David Hsu City of Los Angeles, Los Angeles, CA
Steve Kupferman County of Riverside, Riverside, CA
Jim O'Tousa County of Ventura, Ventura, CA
Charles R. Real Division of Mines and Geology, Sacramento, CA
Wes Reeder County of San Bernardino, San Bernardino, CA