Earthquake science is poised to capitalize on a revolutionary capability for observing global crustal deformation. The concurrent improvements in seismic monitoring networks, high-performance computing, and geodetic measurement of crustal deformation have yielded significant advances in knowledge of fault behavior and crustal stress during the past decades.

A major leap forward will be enabled with the ability to monitor crustal deformation with high temporal and spatial resolution. That capability will extend the observational spectrum into the realm of transient and aseismic deformation. These fast but seismically quiet deformation processes, which are at present poorly understood components of the strain budget, are key to developing a complete understanding of earthquake physics. Community models of earthquake physics and seismic hazards, developed in a data-rich environment will rapidly evolve in response to the data. These new models are expected to yield future earthquake forecasts of useful dimensions that will feed decision support tools to mitigate losses from future large earthquakes.

The Global Earthquake Satellite System (GESS) study responds to the clearly articulated need within the solid-Earth science community for dense surface deformation data. It is a detailed implementation plan in alignment with the recommendations of the Solid Earth Science Working Group (SESWG), and charts the course for NASA to make major contributions to the interagency EarthScope program, while broadening those goals to a global scope. In the GESS study, we explored the requirements space for various components of an integrated system, but focused our mission architecture studies on systems that deliver high-accuracy, high-resolution surface deformation using InSAR. Detailed science requirements were gathered from the wider community to guide the studies.

The major conclusion of the architecture studies is that a constellation of InSAR satellites is needed to address the requirements for monitoring a spectrum of steady and transient deformation processes. To ensure the ability to access any area on the surface of the Earth within 24 hours would require two LEO satellites in orbits above 1000 km. A few MEO or GEO satellites would be equivalent to many spacecraft in LEO and would fully characterize the known transient processes such as postseismic relaxation, slow earthquakes, creep events, and accelerated slip, with full global coverage.