The effects of out-of-plane seismic energy caused by three dimensional shear zone morphology on the nature of reflections in two dimensional crustal seismic sections  

Authors / CoAuthors

Drummond, B.J. | Hobbs, R.W. | Goleby, B.R.

Abstract

Shear zones often appear in seismic images of the deep crust as laterally continuous zones of discontinuous reflections with individual reflections often having high amplitudes. Although shear zones are usually modelled in one or two dimensions, they are more likely to be multiple layers that anastomose in three dimensions. Most crustal-scale seismic reflection surveys use single or at the most only a few profiles, and therefore create two dimensional images of three dimensional structures. Multifold common-mid-point data are stacked and migrated assuming that the seismic energy comes entirely from within the plane of the section. However, three dimensional topography on the reflecting surface results in out-of-plane reflected energy coming into the plane of the section, and energy from the plane of the section being lost from the plane of the section. In this paper, we use synthetic data to consider the effects that topography on a reflector surface has on reflection character. For an out-of-plane diffractor in a homogeneous and isotropic medium, the out-of-plane energy will migrate as if it comes from within the plane of the section, but it will appear to come from a greater depth than that of the true diffractor. Therefore, for a sub-horizontal surface with little topographic relief, out-of-plane energy will fall in the plane of the section below the in-plane reflections from the surface. The result will be a zone of reflections in which the top of the zone reproduces the shape of the reflector within the plane of the reflector fairly accurately, and reflections lower within the zone of reflections will be from out of the plane. ...................................

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nonGeographicDataset

eCat Id

42536

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Keywords

• External PublicationScientific Journal Paper

( Theme )

• seismics

( Theme )

• seismic sections

• AU-WA

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2003-01-01T00:00:00

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Australian Government Security ClassificationSystem    

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Creative Commons Attribution 4.0 International Licence    

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geoscientificInformation

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[-31.0, -30.0, 120.0, 123.0]

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Spatial Resolution

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