Numerical simulations of impact crater formation with dilatancy
File(s)
Published version
Author(s)
Collins, GS
Type
Journal Article
Abstract
Impact‐induced fracturing creates porosity that is responsible for many aspects of the geophysical signature of an impact crater. This paper describes a simple model of dilatancy—the creation of porosity in a shearing geological material—and its implementation in the iSALE shock physics code. The model is used to investigate impact‐induced dilatancy during simple and complex crater formation on Earth. Simulations of simple crater formation produce porosity distributions consistent with observations. Dilatancy model parameters appropriate for low‐quality rock masses give the best agreement with observation; more strongly dilatant behavior would require substantial postimpact porosity reduction. The tendency for rock to dilate less when shearing under high pressure is an important property of the model. Pressure suppresses impact‐induced dilatancy: in the shock wave, at depth beneath the crater floor, and in the convergent subcrater flow that forms the central uplift. Consequently, subsurface porosity distribution is a strong function of crater size, which is reflected in the inferred gravity anomaly. The Bouguer gravity anomaly for simulated craters smaller than 25 km is a broad low with a magnitude proportional to the crater radius; larger craters exhibit a central gravity high within a suppressed gravity low. Lower crustal pressures on the Moon relative to Earth imply that impact‐induced dilatancy is more effective on the Moon than Earth for the same size impact in an initially nonporous target. This difference may be mitigated by the presence of porosity in the lunar crust.
Date Issued
2014-12-01
Date Acceptance
2014-11-11
Citation
Journal of Geophysical Research: Planets, 2014, 119 (12), pp.2600-2619
ISSN
2169-9097
Publisher
American Geophysical Union
Start Page
2600
End Page
2619
Journal / Book Title
Journal of Geophysical Research: Planets
Volume
119
Issue
12
Copyright Statement
© 2014. The Authors.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000348453000011&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Geochemistry & Geophysics
impact cratering
dilatancy
numerical modeling
gravity anomaly
HYDROCODE SIMULATIONS
CHICXULUB CRATER
POISSONS RATIO
STRENGTH
ROCK
COLLAPSE
TARGETS
DAMAGE
MODEL
Publication Status
Published
Date Publish Online
2014-11-15