Abstract Creating accurate soil maps at large scales using traditional methods is a timeconsuming and expensive process. However, remote-sensing techniques can provide spatially and spectrally contiguous data in a timely manner. For this study, 20 root zone soil moisture maps derived from Landsat images during the growing season were used for the detection of soil boundaries. A split moving-window analysis along two demonstration transects in, respectively, a semi-arid desert and riparian area located in the Middle Rio Grande Valley of New Mexico showed that remotely sensed root zone soil moisture can reveal subsurface trends that can be used to identify soil boundaries that do not have a strong surface expression. Overall, the use of multiple remotely sensed root zone soil moisture and Landsat images for soil boundary delineation shows great promise of becoming a valuable tool in the field of digital soil mapping.

The Calabacillas fault is a 40-km-long, down-to-the-east normal fault that trends N-S on the western edge of the Llano de Albuquerque, in western Albuquerque, New Mexico. It is one of several east-dipping normal faults that define the western margin of the Rio Grande rift at the latitude of Albuquerque. In the past 0.5–1 m.y., since the abandonment of the Llano de Albuquerque surface by the Rio Puerco and Rio Grande, vertical displacement on the Calabacillas fault has created a 27-m-high, east-facing fault scarp on the western edge of the llano, equating to a long-term slip rate of 0.027–0.054 mm/yr. Our two trenches were located ~1 km from the south end of the fault, where a 1-km-wide graben has formed east of the main fault scarp. Trenching of the graben across the southern Calabacillas fault was 50% successful. The paleoearthquake event history on the 5.3-m-high antithetic scarp could not be reconstructed in detail because a strong carbonate soil profile had overprinted the entire 3-m-thick colluvial wedge deposit. It appears that numerous submeter displacements created this scarp, but the displacement was partitioned across several faults, so no single free face was higher than 10–20 cm. Free faces so small did not create colluvial wedges, and thus faulting did not trigger the pattern of footwall erosion and hanging-wall deposition needed to identify individual faulting events. On the 27-m-high main fault scarp, a 60-m-long trench straddled a minor slope break that overlies the main strand of the Calabacillas fault. The upper four soils exposed in the trench could be correlated across the main fault and indicated displacements of 10 cm, 30 cm, 55 cm, and 20 cm in the latest four paleoearthquakes. Six infrared-stimulated luminescence (IRSL) dates on eolian sands range from 14 ka at a depth of 0.5 m to 219 ka at a depth of 5 m. Secondary calcium carbonate has accumulated in soils here at a rate of 0.17–0.35 g/k.y. The latest four faulting events are dated at ca. 14 ka, 23 ka, 35 ka, and 55 ka. Thus, the displacement and recurrence times increase with increasing age, yielding relatively consistent slip rates of 0.011–0.028 mm/yr. There is evidence at this trench for a late Pleistocene (14 ka) small faulting/cracking event, similar in displacement and timing to the youngest warping event interpreted for the County Dump fault, which lies ~5 km to the east. The displacements measured in the main scarp trench are even smaller than those inferred on the County Dump fault, despite the length of the Calabacillas fault (40 km) being similar to that of the County Dump fault (35 km). If our trenches had been located farther north toward the center of the Calabacillas fault, the displacements may have been larger. The ages and recurrence intervals of the four events that occurred subsequent to 55 ka are similar to those seen at the County Dump site. The youngest event on the Calabacillas fault had only 5–10 cm of throw, which is considerably smaller than the 20–55 cm throws of the three previous events. This situation parallels the County Dump chronology, where the youngest warping event was abnormally small compared to earlier events.