HR: 1340h
AN: T33C-1396    [Abstracts]
TI: Using Receiver Functions to Analyze Rapid Transitions in Crustal Structure and Deformation in Northern California
AU: * Hayes, G P
EM: ghayes@geosc.psu.edu
AF: Department of Geosciences, Penn State University, 542 Deike Building, University Park, PA 16802 United States
AU: Furlong, K P
EM: kevin@geodyn.psu.edu
AF: Department of Geosciences, Penn State University, 542 Deike Building, University Park, PA 16802 United States
AU: Schwartz, S Y
EM: sschwartz@es.ucsc.edu
AF: Earth Sciences Department, University of California Santa Cruz, Santa Cruz, CA 95064 United States
AB: The Coast Ranges of Northern California have formed in association with the passage of the Mendocino triple junction through the region over the past 10-15 million years. Present day crustal structure reflects the way triple junction processes have driven crustal evolution in this area. Receiver function analyses at a suite of broadband stations in the Coast Ranges allow us to map a rapid change in crustal thickness over a relatively short distance: a decrease from 35+km to $<$25km thick over a distance of only 50km. This rapid transition coincides with a sharp variation in topography, and is also near an area of proposed lower crustal melts (Levander et. al, Geology, 1998). One of our broadband stations (FREY) is located in the vicinity of this sharp transition. Station FREY has been in operation since October 1999, and has produced receiver functions for approximately 20 events with good azimuthal coverage from the NW, W, SW, S and SE and reasonable ray parameter variation. Although there may be complications from dipping layers in this area, a careful analysis can help constrain this rapid change in crustal structure. Initial results at FREY suggest a distinct difference in crustal thickness imaged from the southeast ($\sim$22km) compared to that from the northwest to southwest ($\sim$25km) associated with this transition, and potentially constraining where the crustal thinning takes place. Crustal structure characteristics (such as Poisson's Ratio) for these directions also differs, a phenomenon that may be associated with the presence (or lack of) melt in the lower crust.
DE: 8015 Local crustal structure
DE: 8150 Plate boundary--general (3040)
DE: 7205 Continental crust (1242)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting