Imaging the transition from Aleutian subduction to Yakutat collision in central Alaska, with local earthquakes and active source data

Publication Type  Journal Article
Year of Publication  2006
Authors  Eberhart-Philips, D.; Christensen, D. H.; Brocher, T. M.; Hansen, R.; Ruppert, N. A.; Haeussler, P. J.; Abers, G. A.
Journal Title  Journal of Geophysical Research-Solid Earth
Volume  111
Issue  B11
Pages  -
Journal Date  Nov 8
ISBN Number  0148-0227
Accession Number  ISI:000241985700002
Key Words  prince-william-sound; south-central alaska; seismic-reflection refraction; north-american plate; copper river-basin; v-p/v-s; 3-dimensional crustal structure; wrangell volcanic field; denali fault earthquake; spurr magmatic system

In southern and central Alaska the subduction and active volcanism of the Aleutian subduction zone give way to a broad plate boundary zone with mountain building and strike-slip faulting, where the Yakutat terrane joins the subducting Pacific plate. The interplay of these tectonic elements can be best understood by considering the entire region in three dimensions. We image three-dimensional seismic velocity using abundant local earthquakes, supplemented by active source data. Crustal low-velocity correlates with basins. The Denali fault zone is a dominant feature with a change in crustal thickness across the fault. A relatively high-velocity subducted slab and a low-velocity mantle wedge are observed, and high V-p/V-s beneath the active volcanic systems, which indicates focusing of partial melt. North of Cook Inlet, the subducted Yakutat slab is characterized by a thick low-velocity, high-V-p/V-s crust. High-velocity material above the Yakutat slab may represent a residual older slab, which inhibits vertical flow of Yakutat subduction fluids. Alternate lateral flow allows Yakutat subduction fluids to contribute to Cook Inlet volcanism and the Wrangell volcanic field. The apparent northeast edge of the subducted Yakutat slab is southwest of the Wrangell volcanics, which have adakitic composition consistent with melting of this Yakutat slab edge. In the mantle, the Yakutat slab is subducting with the Pacific plate, while at shallower depths the Yakutat slab overthrusts the shallow Pacific plate along the Transition fault. This region of crustal doubling within the shallow slab is associated with extremely strong plate coupling and the primary asperity of the M-w 9.2 great 1964 earthquake.


104USTimes Cited:2Cited References Count:137

URL  <Go to ISI>://000241985700002
DOI  Doi 10.1029/2005jb004240