--> Abstract: The Spatial Pattern of Seismicity in Western Montana and Central Idaho: An Explanation Based on Seismic Tomography of the Upper Mantle, by Dice Kobayashi and Ken Sprenke; #90181 (2013)

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The Spatial Pattern of Seismicity in Western Montana and Central Idaho: An Explanation Based on Seismic Tomography of the Upper Mantle

Dice Kobayashi and Ken Sprenke
University of Idaho
[email protected]

In the recent years, resolution of seismic velocity perturbations in the upper mantle beneath the Idaho-Montana region has been significantly improved with the results from EarthScope's USArray Transportable Array. Tomographic models indicate a strong S-wave low velocity anomaly beneath the Snake River Plain (SRP) volcanic province likely resulting from mantle flow at the tip and around an edge of a fragmented Farallon slab at depth below the SRP. The elongated low-velocity zone coincides with the axis of the Yellowstone seismic parabola. Further north we have delineated a similar pattern of parabolic seismicity surrounding an elongate low-velocity zone cutting across central Idaho and western Montana subparallel to the SRP. This low-velocity strip may represent a tip-and-edge flow from another advancing remnant of the Farallon slab - this one lying below the Idaho batholith and culminating in a vertex near Bozeman. Based on a hypothesis that lateral thermal contrast is related to the seismicity, our result may lead to refinements in current seismic hazard maps of the region.

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013