Open AccessStrain accumulation across the Carrizo segment of the San Andreas Fault, California: Impact of laterally varying crustal properties
Author(s) -
Schmalzle Gina,
Dixon Timothy,
Malservisi Rocco,
Govers Rob
Publication year - 2006
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jb003843
Subject(s) - geology , seismology , geodetic datum , san andreas fault , terrane , crust , elastic rebound theory , terrain , slip (aerodynamics) , mantle (geology) , fault (geology) , geophysics , geodesy , tectonics , ecology , physics , biology , thermodynamics
Major strike slip faults juxtapose geologically dissimilar terrain which may vary in mechanical properties, leading to an asymmetric pattern of strain accumulation. We present new GPS data on the Carrizo segment of the San Andreas Fault, separating the Salinian block southwest of the fault from Franciscan terrane northeast of the fault, to better quantify asymmetric strain accumulation. We also present a series of finite element models to investigate the possible role of variable elastic layer thickness and material properties of the upper crust. The geodetic data are well fit with a simple model comprising a weak upper crustal zone 10–25 km wide northeast of the fault. This model is also consistent with geologic data on the distribution of major rock types and corresponding laboratory data on their material properties, as well as paleoseismic, seismic and magnetotelluric data. Using this model, we estimate a “long‐term” (average over several seismic cycles) slip rate for the San Andreas Fault of 36 −1.5 +2 mm/yr in agreement with the known Holocene rate within uncertainties, and a viscosity for the combined lower crust/upper mantle of 2–5 × 10 19 Pa s.