The Mantle ELectromagnetic and Tomography (MELT) Experiment is designed to
provide direct observational constraints on the distribution of melt and the
pattern of upwelling beneath a mid-ocean ridge.  Seismic velocity and
attenuation and electrical conductivity are sensitive to temperature, the
presence of melt, and the orientation of crystal fabric within the upwelling
system.  Studies of electromagnetic and seismic wave propagation in the
mantle with arrays of ocean-bottom instruments will furnish measurements that
can be inverted to find horizontal and vertical variations in velocity and
conductivity structure, which can be used to test models of flow.  The needed
measurements cannot be gathered with remote methods or with adequate
resolution using only a small number of instruments.  We propose to deploy a
large array of 47 ocean- bottom seismometers (OBS), for a six month period on
the East Pacific Rise at about 17#251#S to record teleseismic and and
regional earthquake data.  A major experiment with this large number of
instruments recording simultaneously for 6 months is required to obtain the
needed data.