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Pacific Northwest Geologic Mapping and Urban Hazards

Northwest Oregon fault zones and basins

Large, northwest-trending faults underlie northwest Oregon and the cities of the greater Portland metropolitan area. These faults (see figure below) include the Portland Hills fault zone beneath Portland, the Gales Creek fault along the east flank of the Coast Range, and the Mount Angel fault zone in the northern Willamette Valley. Scattered earthquakes occur in the region, and the Mount Angel fault was the likely source of the damaging M 5.6 Scott's Mills earthquake in 1993.

The USGS and Oregon Department of Mineral Industries are using geologic mapping, aeromagnetic and ground magnetic surveys, and subsurface studies to locate the major fault systems and determine their slip sense and history. Our knowledge of Tertiary basin strata is guiding groundwater and soil surveys in the northern Willamette Valley.

Northern Oregon fault zones

Strike slip faults in the North Willamette Valley

Portland Hills Fault zone

Frontal fault zone

Gales Creek fault zone

Mt. Angel fault zone

Canby-Molalla fault zone

This site is maintained by the Pacific Northwest Urban Corridor Geologic Mapping Project, part of the Geology, Minerals, Energy and Geophysics Science Center

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