Constraints on the causes of mid-Miocene volcanism in the Pacific Northwest US from ambient noise tomography

We use data from the 118-station High Lava Plains (HLP) seismic experiment together with other regional broadband seismic data to image the 3D shear wave velocity structure in the Pacific Northwest using ambient noise tomography. This extensive data set allows us to resolve fine-scale crustal structures throughout the HLP area in greater detail than previous studies. Our results show 1) a high velocity cylinder in the crust and average velocities in the upper mantle beneath the Owyhee Plateau; 2) a mid-crustal high velocity anomaly along the Snake River Plain that also extends south into Nevada and Utah; 3) a low velocity anomaly directly beneath Yellowstone throughout the crust; and 4) low velocities beneath the HLP both in the crust and uppermost mantle, possibly indicating very thin or absent mantle lithosphere in the area. These features provide important constraints on possible models for Miocene to recent volcanism in the Pacific Northwest. Citation: Hanson-Hedgecock, S., L. S. Wagner, M. J. Fouch, and D. E. James (2012), Constraints on the causes of mid-Miocene volcanism in the Pacific Northwest US from ambient noise tomography, Geophys. Res. Lett., 39, L05301, doi:10.1029/2012GL051108.