Seismic and Thermal Structure of the Subducting
Yakutat Block
Microplate, Southeast Alaska
Mark A. Bauer, Gary L. Pavlis, and Michael Landes
Indiana University
1001 East 10th Street,
Bloomington, Indiana 47405
The convergent motion of the Pacific and North American Plates in Alaska
has produced geologic features associated with subduction zones such as
trench, Wadati-Benioff zone, and volcanic arc along the Aleutians and has
transported displaced terranes along the Queen Charlotte fault that forms the
northeastern boundary of the Pacific Plate. These subduction features stop
abruptly at the edge of the Yakutat Block
displaced terrane, approximately 300
km from the Queen Charlotte-Fairweather fault. The purpose of this study was to
determine the geometry of the Yakutat
Block
and North American boundary as
well as the cause of the offset volcanic arc and missing Wadati-Benioff zone.
We calculated P and S receiver functions for broadband seismic stations located in southeast Alaska. S-wave data was migrated using a Common Conversion Point procedure. P-wave data was imaged via a three-dimensional, pre-stack migration using plane-wave decomposition. We calculated the temperatures at the top of the Yakutat slab and mantle wedge using analytical models.
The 3-D images we produced show that the Yakutat and Pacific slabs are continuous and extend to the Queen Charlotte-Fairweather strike-slip fault systems. The subducting slab extends north at least to the Wrangell Volcanic Field with a dip than increases gradually from 10° near Prince William Sound to 15° near Yakutat Bay, stripping approximately 15 km of overlying sediments. The location of the Wrangell Volcanic Field and lack of Wadati-Benioff zone are consistent with the temperatures we calculated for the top of slab and mantle wedge after stripping 15 km of sediment.
AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013