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SURFACE OF THE EARTH: NORTH AMERICA 2006 IRIS 5-YEAR PROPOSAL A Multi-Institutional, Multi-Disciplinary, Multi-Facility Experiment in Garner Valley, CA Joan Gomberg • U.S. Geological Survey, Memphis Jamie Steidl • University of California, Santa Barbara David Simpson • IRIS Ken Stokoe • Network for Earthquake Engineering Simulation Paul Bodin • University of Memphis Frank Vernon • University of California, San Diego In April, 2004, IRIS, together with the US Geological Survey (USGS) and the Network for Earthquake Engineering Simulation (NEES), launched a new era in collaborative science and engineering. IRIS sponsored a workshop to explore ideas using resources from multiple earthquake science and engineering facilities to tackle challenging and even intractable problems. This led to a follow-up pilot field experiment, which in addition to IRIS, USGS, and NEES, included participants from the Los Alamos National Lab and other NSF-sponsored consortia; the MAEC, SCEC, CENS, and HPWREN. The experiment piggybacked on an earlier planned inaugural demonstration of NEES facilities, held at the NEES Garner Valley Digital Array (GVDA) site in southern California. We recorded ground motions generated by the ʻTRexʼ shaker truck at the GVDA and surrounding Garner Valley during August 18-22, 2004, and collected earthquake data. Our first study tests the potential for measuring nonlinear sediment response by recording TRex strong shaking on a temporary surface accelerometer micro-array and permanent GVDA down-hole accelerometers. Our second study focuses on ground motion site and basin effects by recording TRex and earthquake signals at 20 temporary real-time, telemetered seismic stations deployed throughout the basin. Our third study focuses on imaging, using basin array data to constrain broadscale tomographic images. To constrain a higher-resolution image along a profile across the basin, we collected reflection data generated by TRex recorded on densely spaced geophone strings, and conducted a sledge-hammer survey to confirm the location of a suspected buried fault. Finally, we assess the potential for shakers like TRex to do broad-scale, deep imaging as we stack TRex signals emitted repeatedly for nearly an hour, recorded on stations of the regional ANZA and statewide California Integrated Seismic Networks. Bodin, P., T. Brackman, Z. Lawrence, J. Gomberg, J. Steidl, F-Y. Meng, K. Stokoe, P. Johnson, and F. Pearce, Monitoring non-linear wave propagation in the 2004 Garner Valley Demonstration Project: EOS, Trans., Amer. Geophys. Union Ann. Mtg., 2004. Gomberg, J., and the Participants in the IRIS/NEES/USGS Workshop and Garner Valley Experiment, Multifacility, Multidisciplinary Earthquake Science and Engineering, EOS, Trans., Amer. Geophys. Union, 85, 404, 2004. Pearce, F., Bodin, P., T. Brackman, Z. Lawrence, P. Johnson, J. Gomberg, J. Steidl, F-Y. Meng, K. Stokoe, R. Guyer and F. Pearce, Non-linear soil response induced in situ by an active source at Garner Valley: EOS, Trans., Amer. Geophys. Union Ann. Mtg., 2004. The 2004 Garner Valley Experiment Working Group, A Pilot Experiment in Collaborative Science and Engineering: EOS, Trans., Amer. Geophys. Union Ann. Mtg., 2004. Pearce , F., P. Bodin, T. Brackman, Z. Lawrence, J. Gomberg, J. Steidl F-Y. Menq, R. Guyer, K. Stokoe and P. Johnson, Site-Specific, Nonlinear Soil Response using an Active Source: Eur. Geosci. Union Gen. Ass., Vienna Austria, 2005. 72
2006 IRIS 5-YEAR PROPOSAL SURFACE OF THE EARTH: NORTH AMERICA Brittle-Ductile Interactions in California K. Aki • La Plaine des Cafres, France A. Jin • National Research Institute for Earth Sciences and Disaster Prevention, Tsukuba, Ibaraki, Japan V. Keilis-Borok, Z. Liu, I. Zaliapin • University of California, Los Angeles This paper introduces a statistical technique, based on the recently developed Multiscale Trend Analysis (MTA), for quantifying correlations between non-stationary processes observed at irregular non-coincident time grids. We apply this technique to studying the temporal correlation between the dynamics of the ductile and brittle layers in the lithosphere using seismicity of California during 1940-2003. Our results confirm the previously reported strong positive correlation between the coda Q-1 and seismicity and its drop before major earthquakes observed in California. The proposed technique has significant advantages over the conventional correlation analysis: (1) MTA allows one to work directly with non-coincident time series without preliminary resampling the data; (2) The correlation is defined via the stable objects --- trends --- rather than noisy individual observations, hence it is highly robust; (3) The correlations are quantified at different time scales. The suggested technique seems promising for the wide range of applied problems dealing with coupled time series. The figure illustrates the brittle-ductile correlation analysis in California, 1940-2003. Horizontal axis represents time, vertical axis represents scale of correlation. Blue area depicts scale-time where the brittle and ductile layers were correlated; pink areas where they were uncorrelated. As suggested by Aki’s Brittle-Ductile Interaction Hypothesis, the correlation is destroyed at progressively larger scales as a large regional earthquake approaches. The destruction of correlation at scales larger than 6 years is only observed a couple of years prior to the Loma Prieta and San Simeon earthquakes. Jin A., Aki K., Liu Z., Keilis-Borok V. I., Seismological evidence for the brittle-ductile interaction hypothesis on earthquake loading, Earth Planets and Space, 56 (8), 823-830, 2004. Zaliapin, I., Jin, A., Liu, Z., Aki, K., and Keilis-Borok V., Temporal (un)correlations between coda Q-1 and seismicity – Multiscale Trend Analysis, Pure. Appl. Geophys., 162, 827-841, 2005. 73
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SCIENCE SUMMARIES 2006 IRIS 5-YEAR
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