Elastic strain accumulation in the Earth's crust is the primary driver of continental earthquakes and can pose significant seismic hazards. Regional studies of seismic hazard in the southern Basin and Range Province (SBR) and Colorado Plateau Province (CP) include assessments of risk to transportation (Euge et al., 1992), buildings (Ghanat et al., 2015, hydro-electric power, and water resources (Lockridge, Fouch, Arrowsmith, & Linkimer, 2012) and the Palo Verde nuclear power plant (U.S. Nuclear Regulatory Commission, 2016). Strain rates can be used with seismicity, fault location, and slip rate data to characterize areas of deformation and enhance regional assessments of potential seismic hazard.The crustal strain-rate field in diffuse plate boundary zones can be affected by both long-term and shortterm processes. Improved understanding of the long-term deformation patterns can be incorporated into models of plate boundary zone hazards (e.g., Petersen et al., 2014) and provide constraints for studies of the forces that act on the lithosphere (e.g., Flesch & Kreemer, 2010). Strain rates along the Wasatch fault zone of the northwestern margin of the CP have been the focus of numerous studies (e.g., Bennett et al., 2003;Niemi et al., 2004) and are better constrained than along the southern and southwestern margin. The poor constraints in the latter areas are due to the low levels of deformation and, until recently, the sparseness of data in southern Utah, southern Nevada, Arizona, and New Mexico.In this study, we analyze crustal motions in the SBR and southern portion of the CP (Figure 1) using two regional densifications of the EarthScope Plate Boundary Observatory (PBO) (Herring et al., 2016) network established with funding from the National Science Foundation (NSF) EarthScope Science Program (Berglund et al., 2012;Kreemer et al., 2015). GPS sites installed by us in 2010 in the SBR and on the CP are referred to in the text and figures as EarthScope (ES) sites (Figure 2a). The expanded network is used in conjunction with the existing EarthScope PBO, MAGNET network (Blewitt et al., 2009) and Rio Grande Rift stations

Bromide and boron were used as tracers during an injection experiment conducted at an artificial recharge facility near Stanton, Texas. The Ogallala aquifer at the Stanton site represents a heterogeneous alluvial environment and provides the opportunity to report scale dependent dispersivities at observation distances of 2 to 15 m in this setting. Values of longitudinal dispersivities are compared with other published values. Water samples were collected at selected depths both from piezometers and from fully screened observation wells at radii of 2, 5, 10 and 15 m. An exact analytical solution is used to simulate the concentration breakthrough curves and estimate longitudinal dispersivities and velocity parameters. Greater confidence can be placed on these data because the estimated parameters are error bounded using the bootstrap method. The non‐conservative behavior of boron transport in clay rich sections of the aquifer were quantified with distribution coefficients by using bromide as a conservative reference tracer.