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Geophysics Department Seminar: David Sandwell: Origin of Transform Faults and Gravity Rolls
Speaker: David Sandwell
Thermal subsidence of the oceanic lithosphere is the dominant signature of the ocean basins. The lithosphere contracts by about 1% in all three dimensions as it cools. The lithosphere is free to contract in the vertical and spreading directions. However ridge-parallel contraction will produce large thermoelastic stress and strain. This talk will focus on two possible tectonic signatures of ridge-parallel contraction – transform faults and gravity rolls. Before jumping into this rather controversial subject, I’ll start the with a status report on achieving a 1-mGal accuracy, global marine gravity grid using the latest radar altimetry data from CryoSAT-2, AltiKa and Jason-2.
Vertical gravity gradient in the South Atlantic highlights the fracture zones, which record the past seafloor spreading. Green dots are locations of earthquakes, which mainly occur along the active spreading ridge.