Inescapable slow slip on the Altyn Tagh fault

GPS surveys conducted in 1994, 1998, and 2002 on the central portion of the Altyn Tagh fault confirm left-lateral slip rates of 9 +/- 4 mm/yr, significantly slower than geological estimates of slip rate for the past several thousand years. The measurements were obtained on a 300-km-long profile between 88degrees and 91degreesE within one fault dimension of the Mw = 7.6 and Mw = 7.8 Kunlun earthquakes of 1997 and 2001. The inferred elastic displacements from these events are incorporated into the interpreted 1994-2002 velocity field. The recent serendipitous occurrence of these two large earthquakes on a sub-parallel fault system suggests that slip on the Kunlun fault may have recently accelerated, thereby reducing the slip rate on the Altyn Tagh fault. However, geodetic data from northern Tibet prior to the 2001 earthquake indicate present-day rates similar to long term rates. This suggests that systematic errors may be present in published geologic slip rate estimates for the Altyn Tagh fault.