Postseismic Deformation near the İzmit Earthquake (17 August 1999, M 7.5) Rupture Zone
by S. Ergintav, R. Bürgmann, S. McClusky, R. Çakmak, R. E. Reilinger, O. Lenk, A. Barka, and H. Özener
We present and interpret the results of postseismic, Global Positioning System monitoring of the first 298 days following the 17 August 1999 İzmit earthquake. Whereas the data suggest some spatial and temporal complexity in the postseismic motions, the overall pattern can be characterized by time-dependent relaxation functions and suggests exponential decay with an estimated 57-day relaxation time. The very rapid deformation during the first few weeks following the mainshock suggests rapid afterslip on and below the coseismic rupture segments. The exponential decay of the postseismic deformations through the end of the observation period suggests contributions from the lower crustal viscoelastic relaxation.