Seismicity of colorado: consistency of recent earthquakes with those of historical record.

Earthquakes instrumentally recorded from 1966 to 1968 have occurred in the same regions of western Colorado, the Arkansas and Platte river valleys, as those felt back to 1870 (from newspaper reports), despite the increasing cultural effects of mining, highway construction, reservoir building, and loading. Thus it appears unnecessary to explain the Denver earthquakes in terms of pressure induced by the introduction of waste fluid. However, the assumption of preexistent tectonic strains in the area of the Rocky Mountain Arsenal seems to be confirmed.