J. V. Morgan
Imperial College London
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Featured researches published by J. V. Morgan.
Earth and Planetary Science Letters | 2000
J. V. Morgan; Mike Warner; Gareth S. Collins; H. J. Melosh; Gail L. Christeson
A seismic reflection and three-dimensional wide-angle tomographic study of the buried, V200-km diameter, Chicxulub impact crater in Mexico reveals the kinematics of central structural uplift and peak-ring formation during large-crater collapse. The seismic data show downward and inward radial collapse of the transient cavity in the outer crater, and upward and outward collapse within the central structurally uplifted region. Peak rings are formed by the interference between these two flow regimes, and involve significant radial transport of material. Hydrocode modeling replicates the observed collapse features. Impact-generated melt rocks lie mostly inside the peak ring; the melt appears to be clast-rich and undifferentiated, with a maximum thickness of 3.5 km in the center. fl 2000 Elsevier Science B.V. All rights reserved.
Geology | 1999
J. V. Morgan; Mike Warner
The buried 65 Ma Chicxulub impact structure in Mexico is the largest well-preserved impact crater known on Earth. Seismic reflection data have revealed Chicxulub to be a multi-ring basin—it has the morphology of the largest impact craters in the solar system. We use these seismic data to relate surface morphology and near-surface structure to deeper deformation within the crust to provide the first high-resolution look into the third dimension of a multi-ring impact basin. We observe three distinct topographic ring types: crater rims, peak rings, and outer rings; each is associated with a different style of deep deformation. Crater rims are the head scarp of the terrace zone formed during the collapse of the transient cavity. The peak ring at Chicxulub appears to have formed when the central uplift collapsed, overthrusting and overriding the terrace zone. The impact has affected the whole crust; the outer rings at Chicxulub are linked to whole-crustal deformation in which the middle crust and lower crust have moved inward and downward. Strong reflections that dip craterward at ∼35° cut the entire crust and connect normal faulting in the sedimentary section with zones of downthrown Moho at a crater radius of ∼35–55 km. Weakly developed exterior rings appear as thrust faults with small offsets; these appear to be the progenitors of the more significant, normally faulted outer rings in multi-ring basins.
Journal of Geophysical Research | 2009
P. M. Vermeesch; J. V. Morgan; Gail L. Christeson; Penny J. Barton; A. T. Surendra
In 2005 an extensive new seismic refraction data set was acquired over the central part of the Chicxulub impact crater, allowing us to image its structure with much better resolution than before. However, models derived from traveltime data are limited by the available ray coverage and the nonuniqueness that is inherent to all geophysical methods. Therefore, many different models can fit the data equally well. To address these issues, we have developed a new method to simultaneously invert traveltime and gravity data to obtain an integrated model. To convert velocity to density, we use a linear relationship derived from measurements on core from the Chicxulub impact basin, thus providing a reliable conversion equation that is typical for lithologies of the central part of this crater. Prior to utilizing the inversion on the observed data, we have run a suite of tests to establish the optimum weighting between traveltime and gravity constraints, using a synthetic model of central crater structure and the real experimental geometry. These synthetic tests indicate which inversion parameters lead to the best recovery of subsurface structure, as well as which parts of the model are well resolved. We applied the method to all existing gravity data and to seismic refraction data acquired in 1996 and the new, higher-resolution seismic refraction data acquired in 2005. We favor the traveltime model wherever we have sufficient ray coverage and the joint model where we have no ray coverage.
Eos, Transactions American Geophysical Union | 2005
J. V. Morgan; Jaime Urrutia-Fucugauchi; Sean Paul Sandifer Gulick; Gail L. Christeson; Penny J. Barton; M. Rebolledo-Vieyra; Jay Melosh
Sixty-five million years ago, a large meteorite hit the Earth and formed the ∼200-km-wide Chicxulub crater in Yucatan, Mexico. The well-known, massive extinction event at the Cretaceous-Tertiary (K-T) boundary appears to have been caused, at least in part, by this impact. In the first few seconds after impact the surface of the Earth was pushed down to form a cavity ∼35 km deep, and in the next few hundred seconds this cavity collapsed to form a multi-ring basin with an inner peak ring. To examine the rings and subsurface structure of this superbly preserved impact crater, a seismic experiment was shot across the crater in January and February 2005 by a team of scientists from Mexico, the United States, and the United Kingdom (Figure 1).
Seg Technical Program Expanded Abstracts | 2012
L. Guasch; Mike Warner; Tenice Nangoo; J. V. Morgan; Adrian Umpleby; Ivan Stekl; Nikhil Shah
Seg Technical Program Expanded Abstracts | 2012
Nikhil Shah; Mike Warner; Tenice Nangoo; Adrian Umpleby; Ivan Stekl; J. V. Morgan; L. Guasch
Geophysical Research Letters | 2002
Michael Croskell; Mike Warner; J. V. Morgan
Archive | 2007
Veronica Bray; Gareth S. Collins; J. V. Morgan; Paul M. Schenk
Archive | 2009
J. V. Morgan; Gail L. Christeson; Mark R. E. Warner
Archive | 2009
Veronica Bray; Paul M. Schenk; H. Jay Melosh; Gareth S. Collins; J. V. Morgan