Transverse structural trends along the Oregon convergent margin: Implications for Cascadia earthquake potential and crustal rotations

Journal Article · Sat Feb 01 04:00:00 EST 1992 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1992)020<0141:TSTATO>2.3.CO;2· OSTI ID:6951849

Goldfinger, C; Kulm, L D; Yeats, R S ^[1]; Applegate, B; MacKay, M E; Moore, G F ^[2]

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1. Oregon State Univ., Corvallis (United States)
2. Univ. of Hawaii, Honolulu (United States)

A remarkable set of west-northwest-trending left-lateral strike-slip faults intersects the Cascadia subduction zone. Three of these faults have been mapped off northern and central Oregon by using seismic reflection, SeaMARC-1A sidescan sonar, and SeaBeam bathymetry. These faults are highly oblique to the north-south structural grain of the active accretionary wedge. One of them has 6 km of horizontal slip; the average slip rate is 7-10 mm/yr. The faults cut the subducting Juan de Fuca plate, and can be traced into the North American plate. Folds that deform late Pleistocene and Holocene sediments on the upper continental slope and shelf strike north-northwest to west-northwest. Some of the west-northwest-trending folds are associated with the throughgoing strike-slip faults, whereas other northwest-trending folds are approximately normal to the plate convergence direction. Many of these folds are mapped across the shelf, and several active shelf synclines project toward Oregon's coastal bays, where marsh subsidence events are inferred to be the result of great subduction-zone earthquakes. These subsidence events may actually record the growth of local synclines, possibly as secondary effects of slip on the megathrusts. The authors postulate that shortening of the forearc region by clockwise tectonic rotation, associated with movement of the left-lateral faults and folding of the upper plate, may accommodate a significant amount of plate convergence.

• OSTI ID: 6951849
• Journal Information: Geology; (United States), Journal Name: Geology; (United States) Vol. 20:2; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
BATHYMETRY
CONTINENTAL MARGIN
DEVELOPED COUNTRIES
DISPLACEMENT RATES
EARTHQUAKES
FEDERAL REGION X
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
INCLINATION
MAPPING
MEASURING INSTRUMENTS
NORTH AMERICA
OREGON
RANGE FINDERS
RISK ASSESSMENT
SEISMIC EVENTS
SEISMIC SURVEYS
SEISMICITY
SEISMOLOGY
SONAR
SUBDUCTION ZONES
SURVEYS
USA