Ruth Neilan and Zheng-Kang Shen Working Group IV Report: GPS Services, Observations, and Interpretations Ruth Neilan and Zheng-Kang Shen

Objectives Advancing application of space geodesy (such as GPS and InSAR) and terresteral geodesy (such as leveling) techniques for the understanding of physical processes associated with continental tectonics and earthquakes.

Monitoring deformation processes associated with the Wenchuan earthquake For understanding coseismic deformation process, considering: Conducting additional surveys such as resurveying of leveling lines improving solutions of GPS vertical components conducting nonlinear inversion of the slip distribution/rupture processes incorporating multiple datasets taking into account of fault geometry and media property variations.

For understanding postseimic deformation process, considering: Increasing spatio-tmporal coverage of the postseismic deformation field using GPS and InSAR, improving the monitoring quality and precision of the deformation process, finding innovative ways to determine the deformation source and reveal its physical mechanism.

Interseismic Deformation Monitoring Enhancing the ability to monitor interseismic deformation processes, particularly along faults and at the eastern margin of the Tibetan plateau, to improve the spatio-temporal resolution (particularly on vertical), capture possible episodic events, and provide constraints for geodynamic model constraints. Developing high-rate GPS network and increasing the frequency range of GPS measurements to monitor multiple deformation processes in a wide range of time scales.

Improving skills on GPS and InSAR data processing and analysis Improving the ability to identify and remove non-tectonic deformation signals and analyze error sources, to reduce data uncertainties for tectonic deformation studies Conducting summer schools/workshops to train young scientists about GPS and InSAR data processing and analysis techniques

Developing new geodetic collaborations Discovering new innovative ways to develop collaboration, such as for US participants providing teaching/training services to young Chinese students, in exchange for Chinese participants providing research equipments such as GPS units to share with in a joint program, exchanging students/young scientists between Sino/US research groups, etc.