title: Western US intermountain seismicity caused by changes in upper mantle flow.
abstract: Understanding the causes of intraplate earthquakes is challenging, as it requires extending plate tectonic theory to the dynamics of continental deformation. Seismicity in the western United States away from the plate boundary is clustered along a meandering, north-south trending 'intermountain' belt. This zone coincides with a transition from thin, actively deforming to thicker, less tectonically active crust and lithosphere. Although such structural gradients have been invoked to explain seismicity localization, the underlying cause of seismicity remains unclear. Here we show results from improved mantle flow models that reveal a relationship between seismicity and the rate change of 'dynamic topography' (that is, vertical normal stress from mantle flow). The associated predictive skill is greater than that of any of the other forcings we examined. We suggest that active mantle flow is a major contributor to seismogenic intraplate deformation, while gravitational potential energy variations have a minor role. Seismicity localization should occur where convective changes in vertical normal stress are modulated by lithospheric strength heterogeneities. Our results on deformation processes appear consistent with findings from other mobile belts, and imply that mantle flow plays a significant and quantifiable part in shaping topography, tectonics, and seismic hazard within intraplate settings.
authors: Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA.
authors: Thorsten W
authors: TW
authors: Becker
authors: Department of Geology, Utah State University, Logan, Utah 84322-4505, USA.
authors: Anthony R
authors: AR
authors: Lowry
authors: Department of Sciences, Università Roma Tre, 00146 Roma, Italy.
authors: Claudio
authors: C
authors: Faccenna
authors: Department of Earth and Planetary Sciences, The University of New Mexico, Albuquerque, New Mexico 87131, USA.
authors: Brandon
authors: B
authors: Schmandt
authors: Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0225, USA.
authors: Adrian
authors: A
authors: Borsa
authors: Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors: Chunquan
authors: C
authors: Yu