chicxulub revealed with new seismic and gravity data jo morgan, anneka smith, elinor styles,...
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![Page 1: Chicxulub revealed with new seismic and gravity data Jo Morgan, Anneka Smith, Elinor Styles, Imperial College London, UK Anusha Surendra, Penny Barton,](https://reader036.vdocuments.site/reader036/viewer/2022062409/56649cc05503460f94986e80/html5/thumbnails/1.jpg)
Chicxulub revealed with new seismic and gravity data
Jo Morgan, Anneka Smith, Elinor Styles, Imperial College London, UKAnusha Surendra, Penny Barton, University of Cambridge, UK
![Page 2: Chicxulub revealed with new seismic and gravity data Jo Morgan, Anneka Smith, Elinor Styles, Imperial College London, UK Anusha Surendra, Penny Barton,](https://reader036.vdocuments.site/reader036/viewer/2022062409/56649cc05503460f94986e80/html5/thumbnails/2.jpg)
Some observationsPreliminary travel-time inversionCorrelation between reflection, velocity, gravity and magnetic data
Model assessmentPurpose: to examine model reliability
Details 2005 seismic and gravity experiment
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New seismic data
New gravity data
Funded by NERC and NSF
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Data examples
Clear arrivals – small uncertainty
Refraction data3,800,000 travel-times
first-arrivals for 1/3 of data picked to-date
Reflection dataProcessing complete
Re
duc
ed
tra
vel-
time
(se
cs)
TW
TT
(se
cs)
0
2
0
2
Horizontal distance (~10 km)Tertiary
Peak ring
Dipping reflectors
![Page 5: Chicxulub revealed with new seismic and gravity data Jo Morgan, Anneka Smith, Elinor Styles, Imperial College London, UK Anusha Surendra, Penny Barton,](https://reader036.vdocuments.site/reader036/viewer/2022062409/56649cc05503460f94986e80/html5/thumbnails/5.jpg)
Seismic inversion Determine a velocity model
that “best-fits” the travel-times
Blue dots: land stationsRed are ray paths (looking from above)
80 k
m
65 km
Anneka Smith
Subset of rays into western land stations
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Anusha Surendra
ExamplePart of inverted velocity model from marine seismometers
Green surface is 6 kms-1 velocity boundary
Peak ring is visible on marine reflection profiles
Topographic peak ring is directly above a low-velocity-zone at depth
![Page 7: Chicxulub revealed with new seismic and gravity data Jo Morgan, Anneka Smith, Elinor Styles, Imperial College London, UK Anusha Surendra, Penny Barton,](https://reader036.vdocuments.site/reader036/viewer/2022062409/56649cc05503460f94986e80/html5/thumbnails/7.jpg)
Structures visible on marine reflection profiles showrelationship to velocitygravity and magnetic data
Bouguer gravity Horizontal gradient gravity Magnetic data
E. Styles E. Styles M. Pilkington
innermost slumped block peak ring
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Problem: Non-uniquenessA range of models will fit the data equally as well
Solution: Model assessmentIn final model, need to distinguish between structure that is required by the data and structure that is consistent with the data
Model assessment
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“Basic” model assessmentUse ray coverage to indicate areas in the model that are well constrained (dark shading)
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“Better” model assessment: Checkerboard TestingAdd checkerboard of high and low velocity anomalies to final velocity model Determine travel-times through this “checkerboard” modelUse inversion to recover the checkerboard
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Determine how well checkerboard is
recovered (semblance)
Identify areas of good recovery (dark)
Gradually decrease size of checkerboard until it
is too small to recover
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More model assessmentTest effect of starting model starting model, inversion parameters etcTest for uncertainties in parametersRun synthetics tests to investigate resolution – example below
Finally get “reliable” velocity modelCan identify parts of model required by data
Peggy Vermeesch
synthetic model central uplift inverted model (1996 data)
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Use drill core, reliable velocity model, and other geophysical data to:Obtain well-constrained structural/lithological modelMelt volume, sample stratigraphic uplift, determine nature of peak ring…
ICDP/IODP workshop – future drilling of ChicxulubPostdam 11-12 September 2006 Call for participants