Interplay Between Slow-Slip Events and Seismicity in the Hikurangi Subduction Zone Revealed by a New High-Resolution Catalog

Abstract Geodetic observations are uncovering increasing numbers of slow-slip events (SSEs), prompting research into the relationships between slow slip and varying forms of seismicity. Such studies are often limited to retrospectively searching for seismicity near to individual SSEs in time and space, disregarding similar activity without SSEs occurring nearby. We perform a systematic examination of the relationship between seismicity and slow slip at the Hikurangi subduction zone (Aotearoa New Zealand) using new and more complete catalogs of earthquakes and SSEs spanning a period of 14 yr. A novel clustering algorithm utilizing a spatiotemporally varying magnitude threshold is proposed to detect diverse seismic sequences. Subsequent k-means clustering in high dimensions classifies each identified sequence as seismic swarm or mainshocks–aftershocks type. We then assess the mutual information between slow slip and seismicity in spatially defined macroclusters (clusters of clusters), revealing significant temporal correlations that vary in nature by spatial region and type of seismic sequence. The diversity in spatial and temporal correlations highlights a complex relationship between slow slip and seismicity, which is likely related to heterogeneity in slow-slip occurrence and geological conditions, and possibly to variations in the driving forces behind slow slip along the Hikurangi.