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  1. Abstract

    We examine the spatiotemporal variations in seismic parameters corresponding to the 2018 Kīlauea eruption. We find that the summit area had mainly strike‐slip focal solutions prior to the eruption, whereas normal‐faulting was the predominant feature during the eruption, partially due to the collapse events. In contrast, the majority of the earthquakes in the central south flank had normal‐faulting solutions before December 2017, in agreement with the normal‐faulting of the Hilina Fault System, while there are more reverse solutions during the eruption. We also observe temporal variations in the estimated in situratios corresponding to the eruption, with increases in the summit and decreases in the East Rift Zone. The sustained lowratios below 4 km depth under the summit caldera may suggest persistent ascent of volatiles from the mantle. The lowvalues in the East Rift Zone are probably associated with increased degassing.

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  2. Abstract

    We investigate earthquake distribution and focal mechanisms associated with the 2018 Kīlauea volcano eruption in Hawaii. Our high‐precision earthquake relocations delineate an aseismic zone bounded by two subhorizontal bands of seismicity at 3.5 and 7 km depths beneath the eastern south flank, both of which are dominated by the shallow‐dipping reverse faulting during the 2018 activity. We interpret the deeper seismicity as related to the basal décollement that separates the volcanic edifice from the oceanic crust. The shallower seismicity is a feature exhibited in the recent activity and, which we propose, reveals a detachment that either represents the contact between Mauna Loa and Kīlauea volcanoes or coincides with the onland extension of the base of the Hilina slump. We suggest that large earthquakes, such as the 1975 Mw 7.7 and the 2018 Mw 6.9 mainshocks, are capable of triggering failures of both the basal décollement and the shallower surface.

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