The 2009-10 SAHKE Experiment: Acquisition and Preliminary Results Across the Interseismically Locked Southern Hikurangi Margin, New Zealand

The passive and controlled source Seismic Array HiKurangi Experiment (SAHKE) project is designed to investigate the structure of the forearc and the physical parameters controlling locking at the Australian-Pacific subduction plate boundary beneath the southern North Island. SAHKE data were acquired between November 2009 and April 2010, in conjunction with a government funded marine seismic survey, and encompassed the full extent of the geodetically determined locked portion of the plate interface beneath Wellington. 480 km of marine multichannel seismic data were acquired on three SAHKE profiles across the convergent margin and recorded by 50 IRIS/PASSCAL short period sensors along one main onshore-offshore (two-sided) and three secondary (one-sided) transects. In addition, over 69000 offshore airgun sources were recorded by the 50 seismograph distributed SAHKE array and 20 permanent national network (GeoNet) stations during the MCS survey. The distributed and transect arrays also recorded a rich data set of more than 100 local earthquakes and 72 teleseismic events (> 6.0 Mw) over a 5 month period, including the 27 Feb 8.8 Mw Chile earthquake and aftershocks. Preliminary analysis shows strong arrivals interpreted as wide-angle reflections and converted waves from the subducting interface.