Crustal Architecture and Images

Updated: Jun 02, 2016

IGCP Project 559 - Seismic Images

Definitions

Definition of a "Classic" Transect

The work of IGCP Project 474 is largely based on compiling and distributing "classic" deep seismic profiling transects from a number of tectonic terranes that have nfluenced global thinking on geological processes. The word "classic" is used in the context of IGCP 474 as being regarded as one of the best examples of its type in the world, a leading or ideal example.

To be classic, a transect should have made a major, global impact on geological thinking in terms of:

1. making a major contribution to our understanding of geological processes
2. changing in a significant way our understanding of a region, area or province
3. making a major contribution to the science of imaging the Earth's crust and deep interior.

Material to be included in IGCP 474 Transects

The compilation for each transect should preferably have as a minimum the following mandatory information:

1. A front page containing the IGCP logo and information on the name of the transect, its geographic location, its global significance and a regional map.
2. The names and affiliations of transect compilation leader and team members, data source organisations and people, acknowledgements.
3. Topographic and tectonic maps showing the position of the transect.
4. The seismic section, uninterpreted and interpreted*. Re-processing of the data for the transect to an agreed format is highly desireable; others will use what is available. Web delivery allows for updates and the addition of reprocessed data when resources permit.
5. Documented key features on the seismic sections.
6. Up to 1,000 words documenting the impacts* that the work has had.
7. A list of key references to published material relevant to the transect.
8. Related web sites for further information.
9. Meta data describing the acquisition and processing details
10. Whether the data are available in digital or hard copy
11. Contact person(s) details for enquiries, preferably the author(s) of the transect report.

Other non-mandatory information can also be included, for example, images of the gravity and magnetic fields, modelled potential field data along cross sections, etc.

* Where alternative interpretations are available, these should be included, as well as a discussion of the significance of any areas of disagreement and steps that could be taken to address the disagreement, because these may become the focus of future research work.

Other seismic images

Seismic images of the Earth's interior have also been produced using "passive" seismic sources, namely, earthquakes. These investigations commonly produce three-dimensional "tomographic" wave-speed images of the Earth's crust and upper mantle for both P and S waves. These three-dimensional images can be "sliced" both vertically and horizontally to illustrate geological structures along transects or at a particular depth.

Seismic profiling using "active" seismic sources at very long offsets between the seismic source and the receiver array are commonly called "wide-angle" seismic profiles. Such profiles have been recorded for many years and have used explosive, vibroseis and marine airgun seismic sources. The seismic source to receiver offsets can vary from less than a kilometer for near-surface geological investigations to over a 1000 km for studies of the deep crust and upper mantle.