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With the support of this grant, we have completed the following tasks:

1. Obtained a 3-year matching fund totaling of $143k for three years from the Tectonics Program, U.S. National Science Foundation to support this project.
2. Established a theoretical framework for how V-shaped conjugate strike-slip faults may have formed in collisional orogens via a detailed analysis of spatial correlations between the Tibetan GPS field and the active conjugate strike-slip faults.
3. Performed preliminary analogue modeling under two end-member conditions: (1) gravitational spreading and (2) basal shearing in driving the formation of conjugate strike-slip faults.
4. Submitted a paper to Geological Society of America Bulletin (now in press) that reports the preliminary results of our findings, with the acknowledgments for the support from the Petroleum Research Fund administered by the American Chemical Society (see the attached file).
5. Set up a new analogue experiment apparatus that is capable of simulating fault initiations under more realistic geologic situations. This analogue experimental set-up allows a deformed region to be affected by three step-motor controlled boundary conditions, thus allowing the variation of side boundary conditions with different combination of velocity histories and basal shearing. In addition, thermal couples were placed at the base of the deforming box in the apparatus. This novel feature introduces temperature-controlled rheology and allows us to test the effect of thermal events in the lithosphere in the formation of conjugate strike-slip faults. Constructing this apparatus took much longer time (nearly two years) than we anticipated. The electric are hooked up and we currently calibrating and programming the motors and thermal couples so that all the components of the experiments can be operated in a synchronous fashion. Due to the late delivery of this machine and my recent trip to Tibet for detailed field mapping, we have not been able to perform any of the proposed experimental tests of competing mechanisms for the generation of V-shaped conjugate faults. However, we have already made plan during the Fall Quarter over the next three months to complete a series of experiments.
6. During the two field seasons, we have collected a suite of samples for paleomagnetic analysis. Preliminary analysis has been conducted at the Paleomagnetic Laboratory, University of California, Santa Cruz under the supervision of Dr. Xixi Zhao. The results show that Cretaceous to Neogene sedimentary strata next to the most prominent pair of conjugate faults in central Tibet, the Gyaring Co conjugate system, have not been rotated about vertical axes and thus support our originally proposed model that they were generated by paired simple-shear-zone deformation.
7. We have also conducted detailed geologic mapping at several sites of paleomagnetic samples. These results help test diverse vertical-axis rotation models for possible development of the central Tibet conjugate fault system.      

Although we are quite satisfied with the above progresses, several aspects of the research project remain unfinished. These include:

(1)     Performing experiments using our newly constructed analogue-model apparatus.

(2)     Completing analysis of the remaining paleomagnetic samples at the University of California, Santa Cruz.

We expect these tasks to be completed by the end of this year and start preparing the two final manuscripts: one on the combined results of surface mapping and paleomagnetic analysis and one on the analogue experiments that simulate various mechanical conditions to generate V-shaped conjugate strike-slip faults.