EARTHSCOPE FACILITIES FOR INVESTIGATIONS OF CASCADIA SEISMICITY

Over the next five years, EarthScope will bring a variety of new observational resources to Cascadia. Both the Plate Boundary Observatory (PBO) and USArray will provide nested sets of instrumentation for regional- and local-scale studies of crustal structure and deformation. Temporary installations (1-2 years) of broadband seismometers in the "Bigfoot" transportable array will augment the existing regional networks for investigations of regional crustal and lithospheric structure. A "Flexible Array" of short-period seismometers will be available for use in controlled source and passive experiments. As part of PBO, a backbone network of fixed Global Positioning System (GPS) instruments, supplemented with a pool of portable GPS instruments, will improve the broad picture of the deformation across the entire region. Clusters of fixed GPS instruments will be deployed to investigate deformation of the crust above the subduction zone. The Puget Sound Region and some volcanic centers (e.g. Mt Saint Helens) will be instrumented with dense instrument clusters including GPS, strainmeters and seismometers.

Installation of EarthScope facilities in Cascadia will start within the next two years and instrumentation for targeted experiments will become available over the next five years. Some parts of the EarthScope facility (e.g. permanent and transportable seismic stations, backbone PBO instruments, and the PBO clusters) will be operated as a community resource for synoptic observations. Other parts of EarthScope (eg the flexible seismic array and the portable GPS instruments) will be targeted at specific structures and the deployment strategy will rely heavily on the input from scientists and organizations with regional interests. With advance planning, EarthScope facilities have the potential to make major contributions to topics of current and evolving interest in Cascadia, such as characterization of the subduction process; identification of earthquake source zones; the origin of silent slip and deep tremor; and the role of basin response in earthquake hazard assessment.