Constraining the source location of the 30 May 2015 ( M w 7.9) Bonin deep‐focus earthquake using seismogram envelopes of high‐frequency P waveforms: Occurrence of deep‐focus earthquake at the bottom of a subducting slab

In this study, the source location of the 30 May 2015 ( M w 7.9) deep‐focus Bonin earthquake was constrained using P wave seismograms recorded across Japan. We focus on propagation characteristics of high‐frequency P wave. Deep‐focus intraslab earthquakes typically show spindle‐shaped seismogram envelopes with peak delays of several seconds and subsequent long‐duration coda waves; however, both the main shock and aftershock of the 2015 Bonin event exhibited pulse‐like P wave propagations with high apparent velocities (~12.2 km/s). Such P wave propagation features were reproduced by finite‐difference method simulations of seismic wave propagation in the case of slab‐bottom source. The pulse‐like P wave seismogram envelopes observed from the 2015 Bonin earthquake show that its source was located at the bottom of the Pacific slab at a depth of ~680 km, rather than within its middle or upper regions.