Collaborative Proposal: Postseismic deformation of the Izmit-Duzce, Turkey earthquake sequence: implications for the mechanics of the earthquake cycle and rheology of the continent

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The Izmit-Duzce earthquake sequence (M=7.4, 17/08/1999; M=7.2, 12/11/1999) offers a uniqueopportunity to answer long-standing, fundamental questions about the nature of the earthquake cycle(mechanics of strain accumulation and release), and the rheology of the crust and upper mantle. Thegeodetic data set we are developing for these earthquakes includes both a well-determined preearthquakevelocity field around the earthquake fault, and a network of GPS stations within the coseismicdeformation zone (near and far field) that captured the initial, rapid, and ongoing longer-termpostseismic deformation. This is one of the most complete geodetic records of deformation for any majorcontinental earthquake anywhere in the world.Interpretation of the geodetic record is facilitated by detailed seismic observations before, during,and following the earthquake sequence, field mapping of fault offsets, satellite image (SPOT) andgeodetic (InSAR) studies, and geologic studies of the 20th Century sequence of earthquakes thatpropagated along the North Anatolian Fault (NAF) from E to W fracturing almost the full 1200 km lengthof the fault (excluding the Marmara segment). Furthermore, the NAF has a long and well recordedhistorical seismic record extending back almost 2000 years that, along with the well-constrainedpaleoseismic record and recent geodetic observations, provides an extensive data set for testingearthquake models of continental faulting.In collaboration with our Turkish partners, we propose to use an extensive catalogue of availableGPS and InSAR data to constrain continuing deformation following the Izmit-Duzce earthquakesequence, and to extend our modeling effort to produce a quantitative description of the dynamics of theNAF system seismic cycle. The proposed research builds on our prior efforts (Ergintav et al., 2009; Hearnet al., 2009) that included analysis of 6.5 years of postseismic GPS observations (both continuous [CGPS]and survey [SGPS]) to characterize the temporal and spatial behavior of initial, and early postseismicmotions, and dynamic modeling for the initial 2.5-year period following the earthquake sequence. Inaddition, an important new constraint on postseismic deformation is provided by recent InSAR analysis(Cakir et al., 2012) that requires a re-evaluation of the role of afterslip along a substantial segment of thecoseismic fault late in the postseismic period, potentially with major implications for seismic hazards.The proposed research will provide an important set of observations on the natureof the earthquake cycle for a major continental strike-slip fault with direct implications for earthquakemechanics, estimating earthquake repeat times, crust and upper mantle rheology as a function of the stateof stress, and interaction between earthquake processes and regional tectonics. This case study provides information on the mechanics of continental strike-slip faults in general, including the San Andreas Fault, earthquake and tsunami hazards in the greater Istanbul area, and opportunities for international scientific collaboration.