Characteristics of deep (≥13 km) Hawaiian earthquakes and Hawaiian earthquakes west of 155.55°W

Abstract

High precision relocation of earthquakes recorded by the Hawaiian Volcano Observatory (HVO) seismic network provides new information on the characteristics of seismic faulting at this oceanic hot spot. Using waveform cross correlation, we have measured correlation coefficients and travel time differences for a set of 14,605 deep (≥13 km) earthquakes recorded from 1988 to 1998. We find that about half of the analyzed earthquakes are in similar event clusters that delineate fault zones in the lower crust and upper mantle. We suggest that much of this deep seismicity reflects rupture in the brittle lithosphere away from the magma pathways, although at Kilauea the stresses from magma movement may additionally help trigger mantle earthquakes on preexisting faults in regions with high differential ambient stresses. Focal mechanisms of similar event clusters throughout Hawaii display characteristic patterns and appear consistent with the hypothesis that deep earthquakes on preexisting faults reflect the stresses due to volcano loading and flexure. We also present the results of applying cross correlation analyses and relocation to ∼7000 earthquakes at all depths located west of 155.55°W and recorded from 1988 to 1998. The pattern of relocated earthquakes at the Kealakekua fault zone is consistent with the presence of a low‐angle detachment on the west flank of Mauna Loa.