Seismic survey in the region of recent earthquake activity near Denver, Colorado

A seismic-reflection survey was carried out near Denver, Colorado, for the U. S. Geological Survey, to determine if structures exist in the 12,000-ft sedimentary section or in the Precambrian basement that might explain the recent earthquake activity. No major faults were revealed in the sedimentary section. Reflections from a steeply dipping horizon believed to be in the basement complex may be indicative of faulting; however, the magnitude cannot be ascertained, as reflection events cannot be correlated at these depths. The results of the survey suggest the possibility of monitoring and studying subsurface structural conditions and related parameters in regions of seismic activity and/or suspected zones of tectonic instability.