Seismic reflection data acquisition in the Taupo Volcanic Zone: Reprocessing of Broadlands Ohaaki 1984 seismic dat

Abstract

Reflection seismic data is used to provide a high-resolution image of the earth’s crust by recording the response of elastic waves reflected by subsurface structure. It is used widely in the oil and gas industry but rarely used in geothermal areas. The Broadlands-Ohaaki seismic survey, acquired in 1984 (Henrys and Hochstein, 1990), is one of only a few reflection seismic surveys to have been acquired in the Taup? Volcanic Zone (TVZ) and where field data are still available. The OHAAKI-84 data used dynamite sources detonated in shallow holes and recorded on a rolling 48 receiver array spaced 20 m apart.
In 2023 we reprocessed seismic data from the OHAAKI-84 survey using modern imaging technologies to determine if the original processing could be improved upon and to help inform any future seismic reflection surveys in the TVZ for geothermal energy exploration or understanding of exiting fields. We recreated the shot and receiver geometry and applied a contemporary processing sequence that has improved on the continuity of the reflectors and provided more detailed P-wave velocity information.
The near-surface volcanic deposits in the TVZ provide a challenging environment for seismic acquisition but our reprocessing has highlighted the value of seismic reflection and we make a number of recommendations for new seismic reflection acquisition including using a modern vibroseis source with longer source to receiver offsets.