Seismic characterization of an active metamorphic massif, Nanga Parbat, Pakistan Himalaya

Earthquakes recorded by a dense seismic array at Nanga Parbat, Pakistan, pr ovide new insight into synorogenic metamorphism and mass flow during mounta in building, Microseismicity beneath the massif drops off sharply with dept h and defines a shallow transition between brittle failure and ductile flow . The base of seismicity bows upward, mapping a thermal boundary with 3 km of structural relief over a lateral distance of 12 km, Anomalously low seis mic velocities are observed at the core of the massif and extend to depth t hrough the crust, The main locus of seismicity and low velocities correlate s with a region of high topography, rapid exhumation, high geothermal gradi ents, young metamorphic and igneous ages, and crustal fluid flow, We sugges t a genetic link between these phenomena in which hot reeks, rapidly advect ed from depth, are pervasively modified at relatively shallow levels in the crust,