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The size distributions of fragments ejected at a given velocity from impact cratersThe mass distribution of fragments that are ejected at a given velocity for impact craters is modeled to allow extrapolation of laboratory, field, and numerical results to large scale planetary events. The model is semi-empirical in nature and is derived from: (1) numerical calculations of cratering and the resultant mass versus ejection velocity, (2) observed ejecta blanket particle size distributions, (3) an empirical relationship between maximum ejecta fragment size and crater diameter, (4) measurements and theory of maximum ejecta size versus ejecta velocity, and (5) an assumption on the functional form for the distribution of fragments ejected at a given velocity. This model implies that for planetary impacts into competent rock, the distribution of fragments ejected at a given velocity is broad, e.g., 68 percent of the mass of the ejecta at a given velocity contains fragments having a mass less than 0.1 times a mass of the largest fragment moving at that velocity. The broad distribution suggests that in impact processes, additional comminution of ejecta occurs after the upward initial shock has passed in the process of the ejecta velocity vector rotating from an initially downward orientation. This additional comminution produces the broader size distribution in impact ejecta as compared to that obtained in simple brittle failure experiments.
Document ID
19880033068
Document Type
Reprint (Version printed in journal)
Authors
O'Keefe, John D. (California Inst. of Tech. Pasadena, CA, United States)
Ahrens, Thomas J. (California Institute of Technology Pasadena, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1987
Publication Information
Publication: International Journal of Impact Engineering
Volume: 5
ISSN: 0734-743X
Subject Category
GEOPHYSICS
Funding Number(s)
CONTRACT_GRANT: NSG-7129
Distribution Limits
Public
Copyright
Other