A decade of short-period earthquake rupture histories from multi-array back-projection

<p><span>Teleseismic</span><span> back-projection has emerged as a widely-used tool for understanding the rupture histories of large earthquakes. However, its application often suffers from artifacts related to the receiver array geometry, notably the `swimming' artifact. We present a </span><span>teleseismic</span><span> back-projection method with multiple arrays and combined P and </span><span>pP</span><span> waveforms. The method is suitable for defining arrays ad-hoc in order to achieve a good azimuthal distribution for most earthquakes</span>.</p><p><span>We present a catalog of</span> <span>short-period</span> <span>rupture histories (0.5-2.0 Hz) </span><span>containing </span><span> 54 </span><span>events </span><span>from 2010 to 2021 </span><span>(</span><span>M</span><span>w</span><span> </span>≥<span> 7.5</span><span>)</span><span>, </span><span>including </span><span>recent </span><span>and significant</span> <span>earthquake ruptures</span><span>,</span><span> e.g., 2021 </span><span>Mw 8.3 </span><span>South of Sandwich Islands, 2021 </span><span>Mw 8.2 </span><span>Chignik, 2021 </span><span>Mw 8.1 </span><span>Kermadec Islands, </span><span>and 2020 </span><span>Mw 7.8 </span><span>Simeonof Island</span><span>.</span></p><p><span>The method provides semi-automatic estimates of rupture length, directivity, speed, and aspect ratio, which are related to the complexity of large ruptures. We determined short-period rupture length scaling relations that are in good agreement with previously published relations based on estimates of total slip. Rupture speeds were consistently in the sub-Rayleigh regime for thrust and normal earthquakes, whereas strike-slip events propagated in the unstable </span><span>supershear</span><span> range. Many of the rupture histories exhibited complex behaviors such as rupture on conjugate faults </span><span>(e.g., </span><span>2018 Mw 7.9 Gulf of Alaska</span><span>)</span><span>, bilateral ruptures </span><span>(e.g., 2017 Mw 7.8 Komandorsky Islands)</span><span>, and dynamic triggering by a P wave </span><span>(e.g., 2016 Mw 7.9 Solomon Islands)</span><span>. For </span><span>megathrust</span><span> earthquakes, ruptures encircling asperities were frequently observed, with down-dip </span><span>(e.g., 2021 </span><span>Mw 8.1 </span><span>Kermadec Islands)</span><span>, up-dip </span><span>(e.g., 2016 Mw 7.8 Pedernales)</span><span>, double encircling </span><span>(e.g., 2015 Mw 8.3 Illapel)</span><span>, and segmented </span><span>(e.g., 2020 Mw 7.8 Simeonof Island) </span><span>patterns. Although there is a preference for short-period emissions to emanate from central and down-dip parts of the </span><span>megathrust</span><span>, emissions up-dip of the main asperities are more frequent than suggested by earlier results.</span></p>