Embargoed: Contents not for release until 12:01 a.m. the day of session. All times Pacific Standard Time. All sessions will be held at the Marriott Downtown Waterfront Hotel in Portland, Ore. Press may receive complimentary registration at the Ballroom Lobby.
The Seismological Society of America (SSA) is an international scientific society devoted to the advancement of seismology and its applications in understanding and mitigating earthquake hazards and in imaging the structure of the Earth.
For a searchable database of abstracts and additional meeting information visit: http://www.seismosoc.org/meetings/2010/program.php
Wednesday, April 21
Characterizing the Next Cascadia Earthquake and Tsunami
8:30 a.m. – Noon, Salon F
The Pacific Northwest is vulnerable to extreme ground shaking and tsunamis generated from great earthquakes along the Cascadia subduction zone, which stretches from Northern California to Vancouver Island. This session reports the latest research on the seismic potential of the area and explores the idea of temporal clustering of earthquakes in the prehistorical record.
- Onshore and offshore paleoseismic data suggest a more frequent recurrence of rupture than previously thought for much of Cascadia. The next Cascadia event is most likely to be a segmented rupture along one or both of the faults southern segments. Time-dependent failure analysis suggests the likelihood of an event by 2060 of ~25 percent for the northern margin and ~80 percent for the southern margin. Conditional probabilities for the next 50 years are 10-15 percent, and 25-45 percent respectively. Chris Goldfinger, Oregon State University, gold@coas.oregonstate.edu
- Supercycles of earthquake clusters, some borrowing unreleased energy from previous cycles, may explain some enigmas about the history of major seismic activity in the Cascadia subduction zone. Chris Goldfinger, Oregon State University, gold@coas.oregonstate.edu
- A statistical analysis on the turbidite event record lends support to the idea that M 9 megathrust quakes along the Cascadia subduction zone occur in cycles of clusters, separated by unusually long time periods. The analyses suggest a median intracluster interval of 260 years and the intercluster interval of 1,759 years. Ivan Wong, URS Corporation, ivan_wong@urscorp.com.
- This talk explores the consequences of applying a clustering model to the earthquake record in the Pacific Northwest. Roland LaForge, Fugro William Lettis Associates, r.laforge@fugro.com
Monitoring for Nuclear Explosions
8:30 a.m. – 3:45 p.m., Salon E
Seismology has new visibility with policymakers and the general public in the context of current evaluations of the Comprehensive Nuclear Test Ban Treaty (CTBT). This robust session reports on developments in monitoring for compliance with nuclear treaties.
- Jofi Joseph, senior advisory to the Under Secretary of State for Arms Control and International Security, is invited to give a luncheon address on issues associated with the CTBT.
Evolution of Slow Slip and Tremor
2:15 – 5:45 p.m., Salon F
Not all natural deformation activity is sudden and violent, as in earthquakes. Episodic, slow, smooth movement of faults, accompanied by low-level seismic wave tremors, can now be detected with modern geodetic and seismic instruments. How these 'slow slip phenomena', which happen over days and weeks, are related to sudden, great earthquakes is the subject of much study and may lead to improved estimates of where and when the great earthquakes will occur.
- Episodic Tremor and Slip (ETS) has now been observed along the northern Cascadia Margin for more than 15 years. More recent densification of GPS coverage and the introduction of Gladwin borehole strainmeters (BSM) as part of the Plate Boundary Observatory have allowed more detailed monitoring of the evolution of the slip surface during prolonged ETS events. Herb Dragert, who first identified slow slip events in Cascadia, reports on a study that examines in detail the along-strike migration of the May 2008 ETS as determined from the GPS and BSM observations. GPS sites overlying the 30 km depth contour of the subducting plate interface show the slip to initiate west of northern Puget Sound and then propagate bi-directionally to the northwest and the south at ~8km per day. Shear strain time series at regional BSM sites confirm this steady expansion of the slip zone. Herb Dragert, Geological Survey of Canada, hdragert@nrcan.gc.ca.
- Seismic recordings combined with eyewitness reports and geotechnical studies of the Oct. 11, 2009, Nile Valley, Wash., landslide provide new clues as to what happens before, during and after a landslide of this type. Landslides may show precursory patterns that seismic monitoring can detect, potentially saving lives. Kate Allstadt, U. of Washington, Seattle, allstadt@uw.edu
- Water levels at Port Angeles, Wash., drop during slow slip events, according to a study of hourly water level records from NOAA tide gauges between 1997 and 2009. Researchers compared base line water levels at five sites in Washington and documented millimeters of relative displacement. The next step is to review 100 years of tidal records to extend the existing record of slow slip events back in time before GPS technology was available. Sequoia Alba, University of Oregon, salba@uoregon.edu
- Recent studies have established the influence of loading from ocean tides on the generation of low-frequency earthquakes in subduction zones. This poster looks at tidally-induced stresses on the San Andreas Fault near Parkfield, Calif. Amanda Thomas, University of California, Berkeley, amthomas@berkeley.edu
Engaging Students and Teachers in Seismology – Case Studies
4:15 – 5:45 p.m., Salon E
This session reports on unique and successful programs that engage K-12 and college students to learn about seismology.
- During a 2009 home football game at Boise State University's Bronco Stadium in Idaho, more than 30,000 fans unwittingly took part in an experiment to record seismicity resulting from the stomps, cheers and general movement during a game. The primary goal was to give the 20 students and faculty experience deploying equipment and an opportunity to work with a unique data set. The broadband instruments recorded microearthquakes following touchdowns, kickoffs and interceptions. Andrew Nies, Boise State University, andrewnies@us.boisestate.edu
- Citizen science: An innovative program, the Quake-Catcher Network (QCN), is developing the world's largest, low-cost strong-motion seismic network by utilizing sensors in and attached to volunteer internet-connected computers. A central mission of the Quake-Catcher Network is to provide scientific educational software and hardware so that K-12 teachers, students, and the general public can better understand and participate in the science of earthquakes and earthquake hazards. Jesse Lawrence, Stanford University, jflawrence@stanford.edu
Special Town Hall Meeting: Portland, Oregon
6:45 – 9 p.m.
To what extent can recent earthquakes in Haiti and Chile inform us of what to expect in the Pacific Northwest? Both earthquakes offer stark lessons in the survivability of earthquakes when societies prepare for these inevitable events but avoidable disasters. Is the Pacific Northwest prepared for the large Cascadia earthquake that will likely happen within our lifetimes? Top scientists and policymakers will provide analysis on the vulnerability of Oregon's schools, bridges, buildings and lifeline infrastructure to damage from severe ground motion and tsunamis.