The Northern California Chapter starts 2010 with mixed feelings. The overwhelming tragedy in Haiti is cause for us to recognize how fortunate we are to have a culture that respects earthquake hazards and uses codes on virtually every new building. But, just as we expect future tragedies as a result of earthquakes in other vulnerable cities worldwide, we also believe smaller-scale tragedies are waiting to happen in California because of existing buildings with dangerous flaws. There has never been a greater need for using our knowledge and expertise.
 
  The New Year promises to be exciting for the Northern California Chapter. We are embarking on an ambitious schedule to offer you opportunities to meet other earthquake professionals, expand your networks, exchange ideas, hear interesting speakers, and serve our community. We have two outstanding community service efforts:
 
  This spring we will release our update of the 1996 Hayward Scenario document and begin an effort to present the scenario and ways to address the risk to local government and private-sector decision makers. We seek volunteers to help out-this is an opportunity to serve your community by meeting with groups such as city councils, chambers of commerce, emergency management committees and others. Although the scenario will be powerful, presenting and discussing the message requires personal contact. Our Chapter efforts will be headed by Janiele Maffei, our Chapter president-elect. Please contact her to express your interest.
 
  Our second community service effort will be to help schools address seismic risk issues-they simply don't know where to start. Many school districts lack the capacity to understand the list of school buildings released by the Division of the State Architect that should be evaluated. Your influence could mean safer children. Send me an email if you're interested in getting involved.
 
  Please remember to renew you membership to EERI National and the Northern California Chapter. The latter is easy to do. Just check the box for the Northern California Chapter on the renewal form that you should have received in the mail and add $25 for the dues. You can also do this by going to www.eeri.org.
 
  Finally, I'd like to thank our outgoing Chapter directors, Yousef Bozorgnia, Joan MacQuarrie, Chris Rojahn and Kate Stillwell, for their time and effort, and I'd like to welcome our new directors Chris Barkley, Ayse Hortacsu, Justin Moresco and Marko Schotanus.  

Tom Tobin
President, EERI Nor-Cal Chapter
415-380-9142

By Lori Dengler, Geology Department, Humboldt State University
 
  On Jan. 9 at 4:27 PM PST a Mw 6.5 earthquake occurred 30 km off the coast of Humboldt County in Northern California. Left-lateral strike-slip movement ruptured a ~N50E-trending, 25 km-long unnamed fault within the Gorda plate, the deformation zone in the southernmost portion of the Juan de Fuca plate. The UC Berkeley Seismological Laboratory estimated a fault rupture of about 25 km that proceeded unilaterally to the southwest. The peak estimated slip between the two sides of the fault was 2.4 meters. The earthquake did not cause a tsunami, and the NOAA National Weather Service West Coast/Alaska Tsunami Warning Center issued a Tsunami Information Statement 4 minutes after the earthquake stating that one was not expected.
 
 

Eureka house off its foundation (photo Mark Hemphill-Haley)

  The earthquake produced strong ground shaking in much of coastal Humboldt County. Peak ground accelerations of 44% of gravity were recorded in Ferndale and 33% in Eureka, the largest population center (~26,000) in the region. About 20% of the vertical monuments at the Ferndale cemetery were translated, rotated, or toppled. Cemetery monuments in Eureka, Loleta and Table Bluff show similar, but smaller amounts, of movement. Liquefaction features that were observed included spread failures with as much as 40 cm of offset on the spit north of the Eel River mouth and sand boils at Centerville Beach and along the Eel River.
 
  Damage, concentrated near the coast from Ferndale to Eureka, appears to be the result of both distance from the hypocenter and guided energy along the strike of the fault. Eureka, the most heavily impacted city by the earthquake, reported over 600 structures affected and nine with major damage. The majority of damaged structures were single-family homes, and several dozen chimneys were severely damaged or knocked down. Eureka's Bayshore Mall (completed in 1987), the largest commercial property in Humboldt County, had damage to the suspended ceiling and was closed for four days. Earthquake losses for the county (as of Jan. 14) were estimated at over $40 million. None of the unreinforced masonry buildings retrofitted after Eureka's 1989 URM ordinance suffered anything more than cosmetic damage.
 
  Security camera films showed that few people followed "Drop, Cover, Hold On", and the majority of people responded to the shaking by walking or running out of buildings. Many people recognized ground shaking as a natural tsunami warning sign and evacuated, but few went by foot and most attempted to drive to higher areas, creating traffic jams.
 
  Thirty-nine aftershocks were detected in the first four days after the earthquake. Most were located along the trend of the fault rupture, but some were located in the SE Gorda plate south of the rupture and along the Mendocino fault. The largest was a magnitude 4.4 that occurred about 90 minutes  after the mainshock. It was widely felt in the Humboldt Bay and Cape Mendocino areas. The "Did-You-Feel-It" reports indicate that aftershocks larger than M3 were felt by nearby residents. None of the aftershocks to date have caused damage. For more information and photos, see the Earthquake Clearing House at EERI National's web site.  
 
  EERI members Bret Lizunda, and David Bonowitz also contributed to this report. 

 

By Ayse Hortacsu, Applied Technology Council

  In December, the Applied Technology Council (ATC) and the Structural Engineering Institute of the American Society of Civil Engineering (SEI/ASCE) hosted their inaugural Conference on Improving the Seismic Performance of Existing Buildings and Other Structures. More than 500 participants from 23 countries attended the event, which was held in San Francisco.  

  Each day of the three-day event started with a plenary session featuring two presentations addressing key topics by an impressive list of speakers such as Lucile Jones and Ron Hamburger. The presentations included Mary Lou Zoback on National Seismic Hazard and Risk, William Holmes on the Report Card on Seismic Rehabilitation Progress, and Maryann Phipps on a 2020 Vision for Seismic Anchorage and Bracing of Nonstructural Components. On the last day of the conference, Chris Poland presented a call to action at the professional and political level. Conference luncheon speakers included Thomas Tobin, who spoke on San Francisco's Community Action Plan for Seismic Safety. 
 
  The Conference offered a strong program on state-of-the-art seismic evaluation and rehabilitation of existing buildings in four concurrent tracks of technical sessions including papers and presentations on:
 
·Improvements to Guidelines, Standards and Analysis Procedures, 
·Seismic Performance and Rehabilitation of Non-Building Structures,
·Seismic Performance of Nonstructural Components,
·New Materials and Innovative Approaches for Seismic Rehabilitation,
·Innovative Approaches to Rehabilitation,
·Mitigation Policy Issues, Strategies and Ongoing Programs, and
·Case Studies on Analysis and Rehabilitation.

  A highlight among the technical sessions was the hands-on demonstration in the hotel lobby on the use of garage doors to resist lateral forces with a full-scale model. In addition to the technical sessions, there were more than 25 poster displays and 20 exhibitors in the exhibit hall.

  Additionally, ATC and SEI awarded seven projects for their innovative seismic strengthening solutions in the past decade. A list of the winners and their projects can be found here.

 

 

  The EERI Nor-Cal Chapter presented its 2009 "Innovation and Exemplary Practice in Earthquake Risk Reduction" Awards during its Dec. 2 Holiday Party. This year's award recipients came in two sets of two: City of Oakland Councilwoman Jean Quan and Policy Analyst Susan Piper and San Francisco Planning + Urban Research Association (SPUR) Deputy Director Sarah Karlinsky and Board Member Chris Poland. The winners embody the spirit of our chapter and its mission to use the science and engineering of earthquakes to reduce risk in our communities.

  Under the respective leadership of these four individuals, the City of Oakland has repeatedly demonstrated exemplary practices that improve earthquake safety, and SPUR has focused much of its energy on disaster planning through the concept of a "resilient city." More information on this year's award winners is available on the chapter's web site.