High-resolution seismic reflection profiles in the Sevier Desert basin in western Utah help clarify the relationship between some late Quaternary fault scarps and subjacent faults. A profile crossing the Clear Lake fault confirms that Holocene(?) displacement has occurred on a high-angle normal fault that is directly connected to the Sevier Desert detachment. If detachment faults can act as seismogenic source zones, then the young movement on the normal fault suggests that the Sevier Desert detachment may be unstable and perhaps the source of future earthquakes. A swarm of late Quaternary scarps near the Drum Mountains overlies a network of steep faults in competent rock that have had recurrent movement. Many subsurface faults are not associated with scarps, suggesting that selected faults ruptured during the last episode of surface faulting.