Stresses released by coseismic faults during subduction toward
lawsonite-eclogite facies conditions in the Alpine subduction complex of
Corsica can be estimated based on the energy required to form
pseudotachylyte fault veins where shear strain can be measured.
Congruent peridotite melting at ambient conditions of 1.5 GPa and 470
degrees C requires a temperature increase of 1280 degrees C to 1750
degrees C. We assume that more than 95% of the work is converted to
heat during faulting, hence that the stress drop is nearly proportional
to the amount of melting and inversely proportional to shear strain.
Minimum estimates or released stress are typically greater than 220 MPa
and as high as 580 MPa. The abundance of pseudotachylyte on small faults
in the studied peridotite suggests that melting is very common on
intermediate and deep earthquakes and that shear beating is important
for seismic faulting at depth.