The long-term slip rates of most major faults in North America are either unknown or, at best, constrained by geologic measurements at only one or two sites. Geologic field work, combined with precise accelerator mass spectrometer dating using 14C and cosmogenic isotopes (36Cl, 10Be, 26Al), is necessary to quantify late-Pleistocene and Holocene slip rates on major faults. Similarly, deformation rates at longer (Quaternary to Tertiary) time scales, as delineated by 40Ar/39Ar, fission-track, and uranium-thorium-helium dating, are required to resolve the evolution of slip and rock-uplift rates. The geologic mapping of faults and the measurement of fault slip rates and prehistoric events is coordinated by the USGS, state geological surveys, and multi-institutional research organizations, such as the Southern California Earthquake Center (SCEC). However, additional programmatic resources will be needed to characterize the active faulting at the comprehensive level envisaged in this report.
Slip-rate data are especially lacking in contractional provinces, where many questions still remain about how strain is partitioned among the major faults and between seismogenic faults and aseismic folding. New techniques in tectonic geomorphology could play a major role in addressing these issues. The evolving geomorphic character of former depositional surfaces inferred by combining detailed field mapping and geochronology with precise digital elevation models is particularly powerful in assessing the patterns of deformation associated with blind thrust faults, where the absence of surface ruptures confounds the traditional paleoseismic approaches. Laser altimetry from aircraft using light detection and ranging (LIDAR) systems can be used to investigate faulting and the surface deformations caused by buried faults. Shaded-relief maps generated from the Shuttle Radar Topography Mission’s 30-meter data could be the basis for mapping Earth’s active faults, folds, and seismically induced landforms between 60 degrees north and 60 degrees south. These data could be the topographic component of global seismic slope stability maps, created at scales that would be useful for long-term regional land-use planning. Significant impediments to the use of these new technologies for earthquake science include the cost of data, national security restrictions on availability, inadequate training, and the lack of cooperative programs.
Topographic data and analyses are necessary but not sufficient to understand the actively deforming lithosphere. In many cases, seismic reflection, deep and shallow boring, and other technologies are required to investigate the subsurface. Remote-sensing geophysical techniques, such as active source seismic reflection and refraction and gravity maps, are valuable for understanding how surface maps of the strain field from GPS, geologic mapping, and geomorphology continue into the subsurface. Heretofore, subsurface data for regional neotectonic studies