Ambient noise tomography across the southern Alaskan Cordillera


Ward, Kevin M.

I present the results of an extensive data mining effort integrating 197 permanent and temporary seismic stations into a Rayleigh-wave ambient noise study across southern Alaska and westernmost Canada. Principal observations of my tomography model are largely consistent with mapped geology features and previous geophysical studies while providing previously unavailable, laterally continuous details of the southern Alaskan Cordillera lithosphere. At intermediate periods, a geophysically uniform crust is observed north of the Denali fault and is consistent with a sharp transition in crustal thickness. Under the Wrangell volcanic belt, a prominent low phase velocity anomaly correlates well with the lateral extent of a relative low gravity anomaly and Neogene surface volcanics. At longer periods, a low phase velocity anomaly bounds the inferred eastern extent of the subducted Yakutat microplate beneath the Wrangell volcanic belt.


Figure 1. Location map and seismic stations used in this study (circles). Black lines mark major faults and terranes boundaries, YCT; Yukon composite terrane, SZ; Alaska Range Suture zone, WT; Wrangellia terrane, PT; Peninsular terrane, AT; Alexander terrane, CT; Chugach terrane, PWT; Prince William terrane, YAK; Yakutat terrane, and PP; Pacific plate [Colpron et al., 2007]. Orange fill shows the surface volcanics of the Wrangell volcanic belt; WVB [Trop et al., 2012] and the dashed white line shows the projected track of the subducted Yakutat microplate [modified from Fuis et al., 2008].

Publication Listing

Ward, K. M. (2015), Ambient noise tomography across the southern Alaskan Cordillera, Geophys. Res. Lett., 42, doi:10.1002/2015GL063613.