| Abstract: | Highly precise (σ ∼1 mm) temporal deformation measurements are taken across the Xianshuihe fault from two pairs of continuous GPS stations
straddling the fault. Baseline vector changes of the two pairs of stations show clearly the difference in deformation behavior
between the Qianning and Daofu segments of the fault: the former deforms steadily, and the latter deforms with a strong transient
component. The transient deformation across the Daofu segment is possibly related to its irregular geometry, where the fault
splits into two branches, that is, the east and west branches. An attempt is made to interpret the baseline vector changes
using a kinematic fault model composed of a brittle layer in the upper crust, a ductile layer in the lower crust, and a transition
zone in between. The slip in the transition zone of the south segment of the Xianshuihe fault is steady. The slips in the
transition zones of the north and Daofu segments of the Xianshuihe fault, however, are not steady, and the average slip rates
there are higher than that of the south segment. The difference in deformation behavior is probably associated with the rheological
properties of the fault interface, suggesting that the overall fault strength of the south segment is greater than those of
the north and Daofu segments, corresponding to longer earthquake recurrence time.
Supported by the National Basic Research Program of China (Grant No. 2004CB418403) |
