Article,
A regionalized upper mantle (RUM) seismic model
Journal of Geophysical Research, 103 (B4): 7121--7136 (April 1998)
DOI: 10.1029/97JB02488
Abstract
Seismic velocity heterogeneity in the Earth's mantle is strongly concentrated
near its top. The shallow heterogeneity of the mantle correlates
strongly with surface tectonics. We use these observations as constraints
of a tomographic experiment aimed at building a regionalized upper
mantle (RUM) reference model. We use a select set of teleseismic
travel times to minimize the mapping of mislocation into structure.
The data selection emphasizes the robustness of individual picks.
The form of the RUM model is a set of velocity profiles as functions
of depth through the upper mantle for each of the different tectonic
provinces of Earth. Together the profiles constitute a three-dimensional
model which incorporates considerable structural detail but is described
by only 90 parameters and has only about 22 degrees of freedom. This
is achieved by irregularly sampling a detailed regionalization of
the globe, by detailed mapping of subducted lithosphere in the mantle
as defined by seismicity, and by combining these structures in an
irregular grid in which bookkeeping is efficiently handled. The resulting
RUM model includes subducting slabs as sharp fast features in the
upper mantle. Old continents are fast; young oceans are slow. Models
have been derived for both compressional and shear velocity. The
RUM model is designed to represent as much of upper mantle heterogeneity
as seen by body wave travel times as possible with a simple model.
It can be useful as a reference model for individual tectonic regions.
Travel times are efficiently generated for the RUM model. Mislocations
of explosions of known location are significantly reduced when corrections
for the RUM model are applied to travel time residuals for a spherically
symmetrical Earth model.
