Twenty million years of continuous deformation along theKarakorum fault, western Tibet: A thermochronological analysis.

The role of the Karakorum fault zone (KFZ) is debated. South of 33°N, ongoing dextral-oblique slip along the SW edge of the Gar basin exhumes metamorphic and magmatic rocks of the Ayilari range. Minerals have recorded a continuum of deformation from temperatures >600–400°C down to 20 Ma of deformation along the fault. Greenschist facies deformation superimposed upon the medium- to high-grade deformation marks a kinematic change from pure dextral to dextral-normal motion associated with the onset of rapid cooling. At the regional scale, the coexistence of transtension in the Gar basin with transpression documented along the Pangong range farther north suggests another example of the ‘‘zipper tectonics'' model developed along the Red River fault. The kinematic shift induced the rise of the Ayilari range starting at 16–12 Ma and the incision of major river courses. The Indus River might have become captive of the relief at this time. The river's 120 km of apparent offset implies dextral motion at a long-term rate of ca 8.5 ± 1.5 mm/yr

Triggered aseismic fault slip from nearby earthquakes, static or dynamic effect?

Observations show that an earthquake can affect aseismic slip behavior of nearby faults and produce “triggered aseismic fault slip.” Two types of stress changes are often examined by researchers as possible triggering sources. One is the static stress change associated with the faulting process and the other is the dynamic stress change or transient deformation generated by the passage of seismic waves. No consensus has been reached, however, regarding the mechanism(s) of triggered aseismic fault slip. We evaluate the possible triggering role of static stress changes by examining observations made after 10 large earthquakes in California. Most of the nearby fault segments that slipped aseismically were encouraged to move by the imposed positive changes in static Coulomb Failure Stress (CFS). Nonetheless, three discrepancies or failures with this model exist, which implies that static stress triggering either is or is not the sole mechanism causing the observed triggered slip. We then use a spring-slider system as a simplified fault model to study its slip behavior and the impact of transient (dynamic) loading on it. We show that a two-state-variable rate-dependent and state-dependent frictional law can generate creep events. Transient loads are then put into the system. Certain types of them can cause a large time advance of (or trigger) the next creep event. While our work examines triggered creep events near the surface, it may well have implications for the occurrence of similar events near the bottom of the seismogenic zone where a transition in frictional stability occurs