Neotectonics, geodesy, and seismic hazard in the Northern Walker Lane of Western North America: Thirty kilometers of crustal shear and no strike-slip?

Roughly 30 km of cumulative right-lateral crustal displacement and 5–6 mm/yr of the ongoing relative right-lateral motion between the Pacific and North American plates are observed in the northern Walker Lane. The right-lateral shear has been accommodated in large part by the development of a set of discontinuous, en echelon, normal fault-bounded basins and perhaps significant vertical axis rotations of the intervening crust. The observations provide an illustrative example of how large amounts of crustal shear may be accommodated in the absence of strike-slip faults and point to difficulties attendant to melding geologic and geodetic observations in the analysis of seismic hazard. In this particular case, the assumption that all geodetically observed shear across the area will be recorded by earthquake displacements may be flawed.

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► Thirty kilometers of crustal shear occurs in absence of strike-slip faults.
► Strike-slip accommodated by en echelon, normal fault-bounded basins.
► Vertical axis rotations accommodate significant portion of strike-slip.
► Geologic slip rates insufficient to account for geodetic deformation field.
► Assumption that all geodetic strain occurs by fault slip may be flawed.