Ec. Cannon et R. Burgmann, Prehistoric fault offsets of the Hilina fault system, south flank of Kilauea Volcano, Hawaii, J GEO R-SOL, 106(B3), 2001, pp. 4207-4219
dHistorical accounts of earthquakes on the Island of Hawaii date only to 18
23 bur lava flows as old as 1500-3000 years B.P. contain fault offsets from
prehistoric earthquakes. The M7.2 1975 Kalapana earthquake produced over 2
5 km of fault rupture along the Hilina fault system. We compare fault offse
ts in prehistoric lava flows with Kalapana earthquake fault offsets in neig
hboring 1969-1974 Mauna Ulu lava flows to estimate the frequency of prehist
oric major earthquakes on the Hilina fault system. Horizontal and vertical
fault offset rates across the Hilina fault system are 4.0 to 12.0 and -2.0
to -20.0 mm/yr, respectively, based on lava flows (750 years B.P. age. Assu
ming prehistoric earthquakes produced similar fault offsets compared to the
Kalapana earthquake, three to five events are recorded in 400-750 years B.
P. old lava flows yielding recurrence intervals of 260-80 years. Vertical f
ault offsets in prehistoric lava flows suggest that hanging wall rotation o
f the Hilina fault system contributes to fault offset. The assumption that
past faulting resulted from prehistoric earthquakes with similar magnitude
and fault offset to the Kalapana earthquake is an oversimplification. Large
south flank earthquakes most likely do not have uniform recurrence interva
ls.