Nonlinear strain buildup and the earthquake cycle on the San Andreas Fault

Journal Article · Sun Jul 10 04:00:00 EDT 1983 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB088iB07p05893· OSTI ID:5669209

Thatcher, W

Two contrasting models of the earthquake deformation cycle on strike slip faults predict significant temporal declines in shear strain rate near the fault, accompanied by a progressive broadening of the zone of deformation adjacent to it. In the thin lithosphere model, transient deformation results from flow in the asthenosphere due to stress relaxation following faulting through most or all of the lithosphere. For an earth model with a thick elastic lithosphere (plate thickness >> depth of seismic slip), transient motions are due to postearthquake aseismic slip below the coseismic fault plane. Data from the San Andreas fault indicate a long-term temporal decrease in strain rate that persists for at least 30 years and may extend through the entire earthquake cycle. Observations support a cycle-long rate decrease and a temporal spreading of the deformation profile only if movement cycles on the northern and southern locked sections of the fault are basically similar. If so, the usually lower strain rates and broader deformation zone currently observed on the sourthern San Andreas represent a later evolutionary stage of the northern locked section, where a great earthquake is a more recent occurrence. Although the data allow some extreme models to be discarded, no sufficiently strong constraints exist to decide between the thin and thick lithosphere models. Regardless of the appropriate model the geodetic observations themselves indicate that strain buildup is sufficiently nonlinear to cause signficant departures fromm recurrence estimates based on linear strain accumulation and the time-predictable model.

• Research Organization: U. S. Geological Survey, Menlo Park, California 94025
• OSTI ID: 5669209
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 88:B7; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
DEFORMATION
EARTHQUAKES
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
NONLINEAR PROBLEMS
SEISMIC EVENTS
SEISMICITY
STRAINS