Premium
Large scale three dimensional P velocity structure beneath the western U.S. and the lost Farallon Plate
Author(s) -
Romanowicz Barbara A.
Publication year - 1980
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl007i005p00345
Subject(s) - geology , trench , mantle (geology) , triple junction , seismology , north american plate , pacific plate , transform fault , plate tectonics , geodesy , paleontology , subduction , geophysics , tectonics , chemistry , organic chemistry , layer (electronics)
The results of a recent large scale three‐dimensional study of P velocity beneath North America are analyzed from the point of view of the search for the fossil Farallon plate in the mantle beneath the western edge of the North American continent. The large scale velocity structure obtained in the western U.S. is compatible with independent finer scale seismic studies and suggests that the Farallon plate can be traced to depths of 300 to 450 km along the entire North‐South extent of the area. At greater depth, no clear evidence is found for its presence: it has either not reached it or is no longer distinguishable from the surrounding mantle. On the basis of the 3‐D velocity study we also venture to predict that, whereas in the central and southern part of the western U.S. the top of the plate seems to have sunk to depths in excess of 200 km, it should still be present at shallower depths beneath the Northwestern region. This is in agreement with the progressive migration to the North of the Mendocino transform‐transform‐trench triple junction and its present day position.