Quantifying three-dimensional deformation and its temporal variability across the active boundary zone between the Pacific and North American plates is one of the core scientific objectives of EarthScope, with far reaching implications to the dynamics of plate-boundary-zone deformation, earthquakes, and volcanic processes. In the last decade, declining cost of instrumentation and data communications, improved accuracy of instrumentation and data processing, increased data availability, enhanced computing power, and corresponding advances in model sophistication have allowed the scientific community to better address an array of critical scientific and societal problems thanks to geodetic data—in geographically disctributed areas using space geodesy.
The core of PBO is a permanent geodetic observatory that consists of an integrated network of GPS stations and borehole and long baseline strainmeters constructed as part of the EarthScope MREFC project. Borehole seismic and strain instruments are well suited for capturing short-term transient deformation (from seconds to a month) and, consequently, play a central role in observing phenomena that occur in the seconds before, during, and after earthquakes, as well as slow fault-slip events and volcanic eruptions. GPS is particularly well suited for time scales greater than a month, thus covering long-period transients, such as those associated with viscoelastic relaxation following earthquakes, and decadal estimates of strain accumulation and plate motion and their spatial variations. By using this suite of complementary techniques, PBO provides unprecedented spatial and temporal coverage of time-dependent deformation signals essential to understanding the fundamental physics that govern deformation, faulting, and fluid transport in Earth’s lithosphere.
PBO and other GPS site velocities used in block modeling by Puskas and Smith, 2009. Tectonic provinces are marked with dashed lines and block boundaries with heavy, black lines. GPS-derived velocities were corrected for postseismic deformation and transformed into the model reference frame prior to plotting. From Puskas and Smith, JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 114, B04410, doi:10.1029/2008JB005940, 2009.