HR: 13:40h
DE: 5420 Impact phenomena (includes cratering)
AN: P72C-01
TI: Deep Three-Dimensional Structure of Chicxulub Impact Crater From Wide-Angle Seismic Data
AU: * Christeson, G L
EM: gail@utig.ig.utexas.edu
AF: Univ. TX Institute for Geophysics, 4412 Spicewood Springs Rd, Bldg 600, Austin, TX 78759 United States
AU: Morgan, J V
AF: T.H. Huxley School, Imperial College, Prince Consort Rd., London, SW7 2BP United Kingdom
AU: Warner, M R
AF: T.H. Huxley School, Imperial College, Prince Consort Rd., London, SW7 2BP United Kingdom
AU: Zelt, C A
AF: Dept of Geology and Geophysics, Rice University, MS-126, 6100 Main St, Houston, TX 77005 United States
AB: We present the results of a wide-angle seismic survey conducted over the Chicxulub impact crater in 1996. 33 ocean bottom and 90 onshore seismograph receivers successfully recorded air gun shots along four deep-reflection profiles over the offshore half of the crater. We have included approximately 29,000 first-arrival crustal refractions and 31,000 PmP reflections into tomographic inversions for three-dimensional crustal and Moho structure of the Chicxulub impact region. There is a good correlation between observed gravity anomalies and many of the features in our modeled velocity structure of the crater. The crustal model includes high velocities near the center of the crater which we interpret as central basement uplift. The width of the uplift in our velocity model, when measured on a profile through the center of the crater parallel to the coastline, is approximately 35 km. The vertical extent of the uplift on this profile is approximately 9-14 km. Three localized peaks in the basement uplift are correlated with either prominent gravity highs or disruptions in the gravity field. Substantial variation in basement depth is also observed outside of the central uplift region. Shallow basement is observed in the northwest region of our study area corresponding to a prominent gravity high. In contrast, deep basement is observed in the northeast region corresponding to a prominent gravity low. Examination of the coincident deep reflection profiles suggests that the regional basement topography is not related to the impact. The primary feature in the Moho structure is a regional deepening in depth to Moho from 33 km in the western region to 35.5 km in the eastern region. Superimposed on the regional trend is Moho uplift of 1-2 km at the center of the crater, with adjacent Moho deepening of the same magnitude. The Moho topography may be related to deformation processes associated with the formation of the outer ring.
SC: P
MN: Fall Meeting 2000