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ABSTRACTTo investigate the relationship between seismicity and slow slip events (SSEs) in the Hikurangi margin we calculate seismicity rates during SSEs using the raw GeoNet earthquake catalogue and a derived sequence catalogue from 2002 through 2011. Most regions have more seismicity during SSEs times; the increase is significant for six out of nine regions. Seismicity regionally accompanying SSEs in the Manawatu and Kapiti regions is part of a cluster of normal faulting earthquakes correlated to a convergence-parallel SHmaxstress direction. Seismicity accompanies the smallest published SSE in 2009, which suggests that the occurrence of seismicity is independent of the total slip. The Manawatu–Kapiti and East Coast regions have, respectively, 1.3 and 1.5 times the average rate of sequences during SSEs. The link between the rate of earthquakes and the timing of SSEs indicates that understanding the connection between the two is important for future hazard analysis and earthquake forecasts.

AbstractThe first four months of aftershocks of the Darfield earthquake have been studied using data from temporary and permanent seismic stations to investigate the fault geometry, stress field and evolution of seismicity and seismic properties. Earthquake relocations illuminate fault segments and show that the majority of aftershocks occurred beyond the areas of highest slip during the Darfield earthquake. Seismic anisotropy shows a mixture of fast directions parallel to the maximum horizontal stress and fault-parallel fast directions. This, combined with the lack of observable growth of seismicity along fault segments, suggests that the Greendale Fault broke a pre-existing fault plane.