| Popis: |
Following the 9.2 magnitude earthquake offshore Sumatra and the devastating associated Tsunami of 26th December 2004, the SAGER research consortium was formed. As part of a series of planned geophysical experiments, 950 kilometres of 2D deep crustal seismic reflection data was acquired in July 2006 by the vessel M/V Geco Searcher in the vicinity of the earthquake epicentre. The survey design, data acquisition, processing and resultant images of this survey are discussed. The data were recorded with a reconfigured, modern commercial seismic recording system. Several modifications were made to the overall data acquisition system in contrast to its normal use for oil and gas seismic exploration. Pre-survey modeling and design studies led to a final acquisition configuration including very large volume, deep towed sources, deep towed single sensor cables, with up to twelve kilometres offset and twenty second recording time. Separation and preservation of very low frequency signal from noise was critical to the success of creating the deep structural image. Multiple reflections and velocity determination also proved to be challenges in this data. The processed images show that the subduction zone can be observed to a depth of over 40 kilometres, along with the associated shallower faults. The interpretation of these data and integration with other geophysical measurements is continuing. This is a rare example of a reconfigured, modern, large scale, commercial seismic reflection system being employed for successful academic deep crustal research. |
