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Media Advisory — USGS Highlights at 1906 Earthquake Conference
Released: 4/17/2006 3:50:17 PM

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U.S. Department of the Interior, U.S. Geological Survey
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Lynn Scarlett, Acting Secretary of the Department of the Interior, will join U.S. Geological Survey (USGS) leadership and scientists giving speeches, presenting new research and analyzing new products during the upcoming 100th Anniversary Earthquake Conference in San Francisco. The conference will be held at the Moscone Center North, 747 Howard Street, April 18-22.

Commemoration Day Luncheon speech: Acting Secretary of the Interior Lynn Scarlett will be a featured speaker at the Commemoration Day luncheon, to be held April 18 in the Esplanade Ballroom, beginning at noon. She will join other federal and state policy makers including U.S. Department of Transportation Secretary Norman Mineta and Congresswoman Nancy Pelosi.

Acting Secretary Scarlett will speak about significant progress in earthquake science that has been made by the U.S. Geological Survey, particularly in the field of real-time notification to first responders, decision makers and concerned members of the public about the magnitude and the location of greatest shaking intensity of earthquake events within the first few minutes of their occurrence.

Following the luncheon, Acting Secretary Scarlett will be available to answer questions from the news media.

Seismological Society of America Annual Luncheon speech: Acting USGS Director Patrick Leahy will speak on Wednesday, April 19, at the Seismological Society of America luncheon, to be held at 12:45 p.m. at the Moscone Center.

Acting Director Leahy will discuss the potential risk of earthquakes in the United States that extend to 75 million people in 39 states and the importance of the many cooperative partnerships that contribute to USGS earthquake networks and research. He will outline new research and initiatives and the importance of making USGS information available and relevant to assist the public in understanding hazards in their communities and to help save lives and mitigate property losses and damage when natural disasters occur.

Other important highlights of USGS participation in the conference include:

TUESDAY, April 18

Opening Plenary Session address: Dr Mary Lou Zoback, senior USGS researcher and Chair of the 1906 Centennial Alliance will speak on the topic: Lessons Learned, Lessons Forgotten and Looking Forward in Earthquake Science at 10:00 a.m. in Moscone Hall E.

Dr Zoback will focus on the important scientific "firsts" that were included in the 1908 Lawson Report. Dr Zoback will summarize the evolution of understanding about the 1906 earthquake and describe how insights from the study of this earthquake form the foundation for the way scientists presently assess seismic hazard The 1906 earthquake was the first to be systematically documented and analyzed in terms of both the cause and the effects of earthquakes. The San Andreas Fault was identified as a major active structure extending nearly the length of the state and the concept of an earthquake cycle, a cycle of slow strain accumulation and rapid release, was established.

The Impact of the Lawson Report: USGS geophysicist John Boatwright reports on the shaking intensity - ShakeMap - created for the 1906 earthquake, based on the Lawson Report and his own exhaustive research. He will preside over this session as well as present his finding at 2:15 p.m.

Since there were few seismic monitoring instruments in the region in 1906, USGS scientists used a variety of both old and innovative techniques to create a detailed ShakeMap. The Rossi-Forel Intensity Map made by Lawson in 1908 and the MMI (Modified Mercalli Intensity) Maps made in 1982 and 1993 from historical accounts have been updated by locating many new sites where shaking was described in Lawson (1908) and by conducting new on-the-ground investigations at many other sites.

New research has enhanced ShakeMap since its introduction in 2005, providing more detailed information on critical areas on the north coast from Point Reyes toward Sonoma, in the Santa Clara Valley, and at the southern end of the 1906 rupture. New investigations find increased intensities near Watsonville and southeast of Santa Cruz than were recorded in the Lawson Report.

The 1906 ShakeMap has provided significant information used to produce simulations of earthquake motion during the 1906 earthquake.

100 Years of Study on the Northern San Andreas Fault: USGS seismologist Carol Prentice will preside over this session and discuss her work along the northern San Andreas Fault at 4:00 p.m. Prentice will relate the important contributions of the Lawson Report to her research findings. She will discuss new studies in five areas along the fault and detailed analysis of the origin of the 1989 Loma Prieta earthquake.


Beyond the San Andreas: The Earthquake Cycle on Plate Boundary Faults: Do Cycles of Stronger Earthquakes on Bay Area Faults Pre-date Written Records?

USGS geologists David Schwartz and Jim Lienkaemper, who will preside over this session, will discuss their research at 10:00 a.m. on Wednesday, April 19. Along with colleagues, they present information on the timing of large earthquakes in the Bay Area between 1600 AD and 2000 AD. Particular interest is focused on the interval period between 1600 and the San Andreas Fault earthquake in 1838. Their research indicates a period between 1670 and 1776 (a maximum interval that could be significantly shorter) during which all three major faults in the Bay Area had large earthquakes. This period of high activity was followed by a period of relative quiescence similar to the quiet period following 1906. It can be inferred that another period of strong earthquake activity will occur again in the Bay Area´s future.

THURSDAY April 20:

Ground Motion Simulations of 1906 Earthquake: Geophysicist Brad Aagaard will show and discuss his research and simulations of earthquake motion and intensity during the 1906 earthquake.

Over a two-year period, scientists from the USGS, Stanford University, Lawrence Livermore National Laboratory, URS Corporation, and University of California at Berkeley simulated how hard and how long the ground shook as a result of the 1906 earthquake using a new USGS three-dimensional geologic and seismic velocity model of the San Francisco Bay area. The simulations have great potential for research, hazard loss estimation, and public education. The 1906 simulations show how the earthquake spread from its epicenter, about two miles west of the San Francisco Zoo, and grew to cause strong shaking and damage along more than 300 miles of the San Andreas Fault. The huge geographic extent of the earthquake´s impact is important for the Bay area´s citizens and decision-makers to understand.

Liquefaction: East Bay Filled Lands Pose Threat: From the study of reports and photographs after the 1906 earthquake, it is known that some of the greatest damage occurred as a result of "liquefaction" of large, sandy artificial man-made landfills along the San Francisco Bay waterfront.

Liquefaction occurs when soils lose their strength during shaking from a strong earthquake. Some fill soils actually amplify the severity of earthquake shaking that is transmitted through the deposits.

A new study by USGS scientists Thomas Holzer, Luke Blair and Thomas Noce and Michael Bennett predicts the likelihood of liquefaction in the East Bay in the event of a large earthquake on the San Andreas or Hayward Faults. Their report is printed in a 1906 Centennial edition of Earthquake Spectra and will be presented at an oral session on Thursday, April 20, at 3:00 p.m.

Their report analyzes large, sandy man-made fills along the Alameda, Berkeley, Emeryville and Oakland waterfronts. Most of the fills were placed in San Francisco Bay after the 1906 earthquake. These filled areas have never been subjected to strong ground shaking. However, liquefaction damage from the 1989 Loma Prieta earthquake due to liquefaction is estimated to have cost over $80 million in economic losses.

The highest hazard areas shown by the liquefaction hazard maps are concentrated in regions of man-made landfill, especially fill that was placed many decades ago in areas that were once tidal flats and submerged bay floor. Such areas along the Bay margins are found in San Francisco, Oakland and Alameda Island, as well as other places around the Bay.

When the ground liquefies, it loses its ability to support buildings and other structures. Liquefaction during large earthquakes commonly disrupts pipelines and road networks and also can cause buildings to settle or move down minor slopes or toward stream banks. The breakage of water mains and distribution pipes and downed electrical lines due to liquefaction contributed significantly to the fires that consumed San Francisco following the 1906 earthquake.

The USGS serves the nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.

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