Alaska Transportable Array Seismic Attenuation Tomography from Local Earthquake P- and S-Waves: Tracing Faults From Southeast to Interior Alaska

Session: Forthcoming Updates of the USGS NSHMs: Hawaii, Conterminous U.S. and Alaska [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Seismic attenuation is of considerable interest in Alaska, a complex region of accreted terranes. With the advent of the Transportable Array in Alaska, it is now possible to investigate broad-scale attenuation from a wealth of local earthquakes. For preliminary analysis in Southeast Alaska, near the Yakutat Block, we analyzed two groups of earthquakes near the Fairweather-Queen Charlotte fault and the Denali fault. We used 5 stations and ~30 earthquakes to determine 164 total t* (integrated path attenuation) measurements. We found high path-averaged Qp and Qs values (<500), but large variations in path-averaged Q at these and 13 more stations in southeast Alaska motivates resolution of Q with 3D tomographic methods. We plan to extend this work northwestward to incorporate TA stations and earthquakes from Interior Alaska and are especially interested in determining whether marked differences in Qp and Qs exist across other major faults such as the Kaltag-Tintina fault. We will compare attenuation results to those determined from the BEAAR experiment near Fairbanks, Alaska. We plan to address the impact earthquake depths have on t* measurements and Q tomography, given the depth uncertainties associated with TA station spacing. This work can help to determine whether or not a complex tectonic history is recorded in seismic properties of the crust and upper mantle.

Presenting Author: Jenny Nakai

Authors