Detailed images of Alpine fault from ultrahigh 2D seismic and narrow-azimuth 3D seismic
Speaker: Jiun Yang
Abstract
A 360 m long ultrahigh-resolution 2D seismic reflection profile across the Alpine Fault had recorded in New Zealand. But 2D data may be contaminated by out-of-the-plane re?ections and diffractions that may be dif?cult to identify and eliminate. Full 3D seismic re?ection methods allow out-of-the-plane events to be recognized and provide superior resolution to 2D methods. A narrow-azimuth 3D acquisition and processing strategy is introduced to produce a high-resolution seismic re?ection volume centered on the Alpine Fault Zone New Zealand . The shallow 3D images reveal late Quaternary deformation structures associated with this major transpressional plate-boundary fault. The narrow-azimuth acquisition strategy was well suited for resolving complex structures within the fault zone. Challenges in processing the data were ampli?ed by the effects of strong velocity heterogeneity in the near surface and the presence of complex dipping, diffracted, and truncated events.
The 3D images reveal that the average apparent vertical displacement 20¡V30 m of the basement surface across the dominant fault strand at this location is somewhat less than that estimated from a pilot 2D seismic re?ection pro?le, suggesting that the provisional dip-slip rate based on the 2D data is a maximum.
Kaiser, A. E., A. G. Green, F. M. Campbell, H. Horstmeyer, E. Manukyan, R. M. Langridge, A. F. McClymont,N. Mancktelow, M. Finnemore, and D. C. Nobes (2009), Ultrahigh-resolution seismic reflection imaging of the Alpine Fault, New Zealand, J. Geophys. Res., 114, B11306, doi:10.1029/2009JB006338.
Kaiser, A. E., H. Horstmeyer, A. G. Green, F. M. Campbell, R. M. Langridge, and A. F. McClymont (2011), Detailed images of the shallow Alpine Fault Zone (New Zealand) determined from narrow azimuth 3D seismic reflection data, Geophysics, 76(1), B19¡VB32, doi:10.1190/1.3515920.