Dispersion of regional body waves at 100-150 km depth beneath Alaska: In situ constraints on metamorphism of subducted crust

Publication Type  Journal Article
Year of Publication  1996
Authors  Abers, G. A.; Sarker, G.
Journal Title  Geophysical Research Letters
Volume  23
Issue  10
Pages  1171-1174
Journal Date  May 15
ISBN Number  0094-8276
Accession Number  ISI:A1996UM11300028
Key Words  mantle; plate; zone

Phase delays at high frequencies are observed in body waves that travel in the Alaska slab, along its strike at 100-150 km depth. The delays, between 2-6 Hz energy and the direct 0.5-1 Hz arrival, are 0.5-1.5 s for P waves and 1.5-4 s for S waves. Such dispersion suggests a waveguide structure that parallels the slub, perhaps near its top. A channel that is 2-6 km thick and 2.5-5% slower than surrounding mantle can explain the observations. The thickness of the layer is comparable to that of subducted oceanic crust or somewhat thinner. The layer may be crust that is slow at these depths. The required velocity anomaly is too small to be due to a continuous layer of metastable gabbro yet too large to represent an eclogite layer. It may indicate a mixture of the two, or persistence of hydrated mineral assemblages to depth.


Um113Times Cited:22Cited References Count:22

URL  <Go to ISI>://A1996UM11300028