Behr has investigated a wide range of fields in structural geology, including the rheology of the upper crust and mantle. In a 2022 study, she substantiated the importance of plate interfaces in subduction dynamics, suggesting that the shear zone rheology of subduction interfaces is sensitive to the composition of subducting crustal material. Through the use of 2D numerical models of subducting plates Behr and co-author proposed that the viscosity and topography of the plate interface can influence the convergence speeds of the plates both prior to and after slab interaction. She also proposed that a stronger plate interface leads to steeper slab dips, more vertical sinking, and compressional deviatoric stresses in the overriding plate, while a weaker interface leads to neutral extensional stresses in the forearc. Behr's work has also been influential in earthquake hazard assessment . Through several studies of the Agua Blanca Fault (ABF) in Northern Baja California, she and co-authors mapped how strain is transferred along the southernmost part of the
San Andreas fault system by studying Late Quaternary slip histories. Using
GPS and
LiDAR, 10Be exposure, and optically stimulated luminescence geochronology techniques, she observed that the ABF has an along-strike slip rate of ~3mm per year, which has remained relatively constant over time. The ABF accommodates at least half of the total slip across the Peninsular Ranges of the San Andreas fault system. These studies have been influential for seismic hazard assessments which have previously lacked long-term slip rates along this portion of the San Andreas fault system. Behr has pioneered a new method for evaluating lithospheric strength profiles in the middle crust. By identifying preserved microstructures in exhumed mid-crustal rocks in the Whipple
Mountains of California as points in a temperature-depth-stress space, Behr completed a profile of the crust's stress to a depth of 20 km. Through this research, Behr and co-author estimated the ambient stresses in the middle crust in this region and confirmed that stress in the middle crust is consistent with
Byerlee's law during extension. Some of Behr's research investigates the strength of the crust with depth. By compiling shear stress magnitudes at major fault zones from across the globe, Behr and co-authors suggest that there is an abrupt downward temperature-controlled cutoff of the weakening processes that control fault behavior in the upper crust. Continental crust is stressed close to failure down to the brittle-ductile transition zone, after which the crust becomes load-bearing. == References ==