The original paper with abstract

[Gautam Majumdar <gmajumdar@freeuk.com>]

On Thursday 24 January 2008 00:32:21 Janet m vandenburgh wrote:
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>
> Seismic images show dinosaur-killing meteor made bigger splash The most
> detailed three-dimensional seismic images yet of the Chicxulub crater, a
> mostly submerged and buried impact crater on the Mexico coast, may modify a
> theory explaining the extinction of 70 percent of life on Earth 65 million
> years ago.
> ... According to Sean Gulick, a research scientist at the Institute for
> Geophysics at The University of Texas at Austin's Jackson School of
> Geosciences and principal investigator for the project,...
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http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo103.html

Nature Geoscience
Published online: 13 January 2008 | doi:10.1038/ngeo103

Importance of pre-impact crustal structure for the asymmetry of the Chicxulub 
impact crater

Sean P. S. Gulick1, Penny J. Barton2, Gail L. Christeson1, Joanna V. Morgan3, 
Matthew McDonald1,6, Keren Mendoza-Cervantes4, Zulmacristina F. Pearson5,7, 
Anusha Surendra2, Jaime Urrutia-Fucugauchi4, Peggy M. Vermeesch3,7 & Mike R. 
Warner3

Impact craters are observed on the surfaces of all rocky planets and 
satellites in our Solar System1; some impacts on Earth, such as the 
Cretaceous/Tertiary one that formed the Chicxulub impact crater2, 3, have 
been implicated in mass extinctions4, 5, 6, 7, 8, 9, 10, 11, 12. The 
direction and angle of the impactâor its trajectoryâis an important 
determinant of the severity of the consequent environmental damage, both in 
the downrange direction (direction bolide travels) and in the amount of 
material that enters the plume of material vaporized on impact2, 13, 14, 15. 
The trajectory of the Chicxulub impact has previously been inferred largely 
from asymmetries in the gravity anomalies over the crater2, 3. Here, we use 
seismic data to image the Chicxulub crater in three dimensions and 
demonstrate that the strong asymmetry of its subsurface correlates with 
significant pre-existing undulations on the end-Cretaceous continental shelf 
that was the site of this impact. These results suggest that for rocky 
planets, geological and geomorphological heterogeneities at the target site 
may play an important role in determining impact crater structure, in 
addition to impact trajectories. In those cases where heterogeneous targets 
are inferred, deciphering impact trajectories from final crater geometries 
alone may be difficult and require further data such as the distribution of 
ejecta.

-- 
gautam