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Western USA USGS GPS Transects. • Dense spacing to detect offsets across faults. • Surveyed every 4 years since 1999-2003. • ± 1 mm/yr precision after ~8 years. Highway 50 Transect GPS Velocities (1992-2002). NWL !. Sierra Nevada. Colorado Plateau. WEST. EAST.
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Western USAUSGS GPS Transects • Dense spacing to detect offsets across faults • Surveyed every 4 years since 1999-2003 • ± 1 mm/yr precision after ~8 years
Highway 50 Transect GPS Velocities (1992-2002) NWL ! Sierra Nevada Colorado Plateau WEST EAST Hammond & Thatcher (2004)
Western USAUSGS GPS Transects • Dense spacing to detect offsets across faults • Surveyed every 4 years since 1999-2003 • ± 1 mm/yr precision after ~8 years
Strike-Slip to Normal Fault Transition in Northern California
Plate Boundary Forces Determine Faulting Style in Continental Plate
Northward Migration of MTJ Causes Normal Faults to Evolve into Strike-Slip Faults
TAKE HOME POINTS • Strike-slip to normal faulting transition near Lassen, at latitude of Mendocino triple junction (see Faulds & Henry 2008) • Transition clearly reflected in GPS velocity field • ~4 mm/yr extension N of Lassen • ~2 + 2 mm/yr strike-slip S of Lassen • MAGNET GPS will provide better constraints for strike-slip rates across Honey Lake & Mohawk Valley faults