Tectonic setting of the Mendocino triple junction region

Conference · Thu Apr 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5291068

Clarke, Jr, S H; McLaughlin, R J ^[1]; Carver, G A; Burke, R M; McPherson, R C ^[2]

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1. Geological Survey, Menlo Park, CA (United States)
2. Humboldt State Univ., Arcata, CA (United States)

Onshore and offshore geologic mapping coupled with topical investigations constrain the tectonic relations and geometry of active plate boundaries in the Mendocino triple junction region. Along the northern California coast and offshore, Gorda-North American plate convergence is reflected by youthful west- to northwest-verging thrust fault systems that extend to or near the plate interface at depth. Interplate coupling across a minimum breadth of 70--80 km is indicated by late Quaternary uplift and shortening rates, the nature and distribution of upper and lower plate seismicity, divergent trends in upper plate structures, and a history of large late Holocene earthquakes. Offshore seismic-reflection and seismicity data from the vicinity of the Mendocino fault (MF) show that the fault dips steeply to the north, and that the older, relatively rigid Pacific plate acts as a buttress against which the southern Gorda plate is being deformed. Onshore investigations show that the San Andreas fault zone (SAF) extends on land southeast of Point Delgada (at Whale Gulch), and is manifested along the north and northeast side of the King Range (KR) by north-northeast-vergent thrust faults. This thrust fault system may root into the steeply dipping offshore San Andreas fault. Faults of this system may include active, blind northeast-vergent thrusts that extend from a root zone beneath the King Range northward and upward into Franciscan Complex (Coastal belt) rocks along the north flank of the range. The southern Cascadia subduction zone megathrust intersects the Mendocino and San Andreas transform faults in the Mendocino triple junction. The upper crustal location of this intersection lies nearshore and/or landward along the north flank of the King Range. An area of focused rapid uplift and repeated coseismic growth (Mendocino Uplift) straddles the triple junction.

• OSTI ID: 5291068
• Report Number(s): CONF-9305259--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:5
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
CALIFORNIA
DEVELOPED COUNTRIES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
GEOMETRY
GEOPHYSICAL SURVEYS
MAPPING
MARINE SURVEYS
MATHEMATICS
NORTH AMERICA
OFFSHORE SITES
PLATE TECTONICS
SEISMIC SURVEYS
SEISMICITY
SUBDUCTION ZONES
SURVEYS
TECTONICS
USA