Abstract

The Hikurangi Margin, east of the North Island of New Zealand, contains a significant gas hydrate province. However, the distribution, concentration and dynamics of hydrate accumulations in the southern portion of the margin (the Pegasus SubBasin) off the northeastern coast of the South Island are poorly constrained. In late 2009 and early 2010, a seismic dataset consisting of approximately 3000 km of 2D seismic data was collected in the Pegasus Sub-Basin. The Pegasus Sub-basin is located in the zone of transition between the tectonic regimes of North Island subduction and South Island transpression. The seismic data were acquired using a 12-km-long streamer, providing a grid of data over an area of ~35,000 km2, and providing acquisition geometries that facilitate studies based on amplitude variations with offset. BottomSimulating Reflections (BSRs) are abundant in the data, and they are supplemented by other features that may indicate the presence of free gas and gas hydrates in zones of high concentration. We present initial observations and results from the study, including the identification of specific features such as blanking, bright spots (high-amplitude anomalies) and flat spots (indicating potential fluid contacts).