Evidence is presented for a special type of fault characterized by a very large displacement (≥100 m) occurring during a single-slip event at seismogenic velocity (>0.1 m ṁ s−1). I propose that faults formed by this type of behavior be referred to as superfaults. Such faults typically undergo unconstrained (free-surface) dip-slip or reverse-slip movement. Superfaults are associated with scenarios involving high and ultrahigh strain rates, notably (1) coherent rock slides due to slope instability, (2) transient-cavity collapse following hypervelocity impact, and (3) roof-pendant failure during caldera formation. Superfault displacements are estimated to range from 102 to 104 m per single-slip event, with the potential for massive energy release at the sliding interface. Field evidence and calculation indicate that the bulk of this energy is converted to heat through frictional melting.

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