Potentially active faults are exposed in the steep glaciated topography
of the central Southern Alps, New Zealand, immediately adjacent to the
Alpine Fault plate boundary. Four major faults exposed along the flanks
of three of the highest mountain ranges strike 10-23 km (potentially 40
km) NNE oblique to the Alpine Fault, dipping 57 degrees +/- 12 degrees
NW in the opposite direction. Youngest discernable motions were reverse
dip-slip, accommodating both margin-perpendicular shortening and dextral
margin-parallel components of plate motion. Kinematic analysis yields a
compression axis (295/10 degrees +/- 9 degrees trend or plunge)
equivalent to the contemporary shortening determined from seismological
and geodetic studies, suggesting the faults may be active, although
definitive evidence for recent movement or single event displacements is
lacking. There are 106 other potentially active faults mapped in central
Southern Alps with strike lengths 4-73 km. Earthquake parameters were
assigned from fault trace lengths and historical earthquake statistics,
indicating potential for M-W 5.5-7.4 earthquakes at recurrence intervals
of 1000-10,000 years. Such long recurrence intervals are consistent with
the faults having little surface expression, with rapid erosion of these
seismically agitated mountains erasing any evidence of surface rupture
during periods between earthquakes. The central Southern Alps faults
exemplify the difficulty in fully deciphering long-term (e.g., Holocene
or Quaternary) records of seismicity in tectonically active regions with
rapidly evolving landscapes. Although there may be little evidence of
surface ruptures remaining in the landscape, the faults are still an
important potential source of earthquakes and seismic hazard.