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Mantle control of plate boundary deformation
Author(s) -
Melbourne Tim,
Helmberger Don
Publication year - 2001
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 - 10.1029/2001gl013167
Subject(s) - geology , mantle (geology) , seismology , lithosphere , plate tectonics , north american plate , pacific plate , basin and range province , geodynamics , continental margin , geophysics , subduction , tectonics
The seismic wavefield propagating along the recently instrumented Pacific‐North American plate boundary (California) displays remarkable variation, with regional shear waves arriving at coastal stations up to 20 seconds earlier than equidistant stations in eastern California. Broadband modeling of this data reveals that coastal paths sample fast upper mantle typical of Miocene‐aged ocean plate (>50 Km thickness). Inland paths sample slower uppermost mantle, with the seismic lithosphere, or lid, measuring less than 5 Km thick, characteristic of the Basin and Range extensional province. The boundary in the uppermost mantle between these provinces is sharp, expressing the juxtaposition of the stronger Pacific plate with weaker continental North America. The lid step coincides with regionally maximum dextral strain rates measured with GPS, suggesting the uppermost mantle modulates long term, regional‐scale continental margin deformation and evolution.