LAUSR

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 situ Vp/Vs ratios corresponding to the eruption, with increases in the summit and decreases in the East Rift Zone. The sustained low Vp/Vs ratios below 4 km depth under the summit caldera may suggest persistent ascent of volatiles from the mantle. The low Vp/Vs values in the East Rift Zone are probably associated with increased degassing.