A zone of diffuse deformation -600 km-wide extending from northern California to Washington has developed resulting from the oblique subduction of the Juan de Fuca plate beneath North America, and the northwestward migration of the Pacific plate. This zone is marked by a change in structural style from transtension in...
The Corvallis fault is a 50 km long northeast-trending structure, part of which defines the boundary between the central Willamette Valley and the east-central Coast Range of Oregon. Previously the fault had been mapped as either a high-angle reverse or normal fault, with the east block down. New gravity data...
Surface geology, seismic data, petroleum exploratory well data, and water well data
have been used to analyze the structural and tectonic history of the southern Willamette
Valley. Tertiary strata beneath the southern Willamette Valley appear to have had an early
Cascade or Clarno volcanic source to the east by the...
Elliptical borehole enlargements or "breakouts" caused by systematic spalling of a
borehole wall due to regional maximum horizontal stresses were identified in 18 wells
drilled in the Coast Range and Willamette Valley of western Oregon. The breakouts
generally indicate a NNW to NNE orientation of maximum horizontal compression
(oH[subscript max])...