Post-Seismic Deformation for the 1999 IZMIT/DUZCE Turkey Earthquake Sequence

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Robert E. ReilingerEAR-0001095The Investigators propose to monitor and analyze postseismic deformation for the 17 August 1999, Izmit (M=7.4) and the 12 November 1999, Duzce (M=7.1), Turkey earthquakes. Together, these earthquakes resulted in a continuous surface break along a 150-km segment of the western North Anatolian fault, with right-lateral surface offsets reaching 5 m. The tight constraints on secular strain and co-seismic fault slip for these events and the detailed monitoring of the early phase of post-seismic motions, provide an important opportunity to develop the observations needed to constrain models of after-slip and viscoelastic relaxation. Distinguishing the possible contributions of these mechanisms has implications for the rheology of the continental lithoshere and localized rheology in the fault zone - rheological properties that are currently poorly constrained by observations and that are critically important for modeling dynamic processes associated with plate interactions. In addition, it is anticipated that the results of this study will enhance our understanding of the mechanics of the earthquake cycle in this and similar tectonic regions (such as the San Andreas fault). While this work is not meant to be a comprehensive study of earthquake hazards in this area, the results will be directly relevant to estimating the partitioning of slip on the various branches of the NAF in the Marmara region. Furthermore, the co-seismic and post-seismic fault parameters resulting from the proposed research are needed to constrain models for stress transfer to adjacent fault segments, providing an improved physical basis for estimating earthquake hazards.