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Investigations of surface strain, plate boundary motion, frictional properties of faults and mechanical properties of the Earth's crust are necessary to determine what controls the spatial and temporal patterns of earthquakes. Space-based observations allow us to measure the entire earthquake cycle including the aseismic or quiet accumulation of strain. These new measurements are providing insights into how stress is transferred between faults, how much strain is released seismically versus quietly, and potentially how faults fail.

Fully modeling the earthquake system requires knowledge of the current and past motions and interactions of faults. It is therefore necessary to measure the current ongoing deformation associated with plate tectonics and faults. It is also necessary to obtain detailed topographic and geomorphic characteristics of faults to better understand the past earthquake history. Targeted measurements along plate boundary zones can address how fault systems interact. Because we are discovering that fault systems can interact over hundreds of kilometers exploratory measurements are also required until we understand these systems better.

Earthquakes and SAR  

For example, by understanding the stress transients that occur after major earthquakes, it may be possible to determine more reliably the probability of future earthquakes occurring at other locations in the system. Analysis of temporal transients and the spatial complexity of deformation are likely to reveal properties of the faults and the Earth's crust. A complete program of study will cover areas from laboratory measurements, global scale measurements, and large scale computing to synthesize all aspects of the problem.

Varying time and space sampling requirements and accuracies dictate specific observational approaches: GPS networks and INSAR constellations will be needed to provide dense spatio-temporal sampling and high accuracy observations of the changes of the Earth's surface. Seismic networks, borehole arrays, low-frequency sounders, and highly accurate gravity measurements will enable characterization and change assessment of the subsurface structure and composition.

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