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Surface motion of a fluid planet induced by impacts

Ni, Sidao and Ahrens, Thomas J. (2006) Surface motion of a fluid planet induced by impacts. Geophysical Journal International, 167 (1). pp. 445-452. ISSN 0956-540X. doi:10.1111/j.1365-246X.2006.03072.x.

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In order to approximate the free-surface motion of an Earth-sized planet subjected to a giant impact, we have described the excitation of body and surface waves in a spherical compressible fluid planet without gravity or intrinsic material attenuation for a buried explosion source. Using the mode summation method, we obtained an analytical solution for the surface motion of the fluid planet in terms of an infinite series involving the products of spherical Bessel functions and Legendre polynomials. We established a closed form expression for the mode summation excitation coefficient for a spherical buried explosion source, and then calculated the surface motion for different spherical explosion source radii a (for cases of a/R= 0.001 to 0.035, R is the radius of the Earth) We also studied the effect of placing the explosion source at different radii r_0 (for cases of r_0/R= 0.90 to 0.96) from the centre of the planet. The amplitude of the quasi-surface waves depends substantially on a/R, and slightly on r_0/R. For example, in our base-line case, a/R= 0.03, r_0/R= 0.96, the free-surface velocity above the source is 0.26c, whereas antipodal to the source, the peak free surface velocity is 0.19c. Here c is the acoustic velocity of the fluid planet. These results can then be applied to studies of atmosphere erosion via blow-off caused by asteroid impacts.

Item Type:Article
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Ni, Sidao0000-0003-2988-4850
Additional Information:© 2006 The Authors. Journal compilation © 2006 RAS. Accepted 2006 May 15. Received 2006 May 15; in original form 2006 April 21. We thank two anonymous reviewers and editor Bruce Buffett whose comments greatly improve the manuscript. Research supported by NASA grant NNG04GI07G, and supported by NSFC grant 40425005. Contribution # 8957, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125.
Funding AgencyGrant Number
National Natural Science Foundation of China40425005
Subject Keywords:atmosphere; blow-off; giant impact; surface waves
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Caltech Division of Geological and Planetary Sciences8957
Issue or Number:1
Record Number:CaltechAUTHORS:20100319-092501259
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Official Citation:Ni, S. and T. J. Ahrens (2006). "Surface motion of a fluid planet induced by impacts." Geophysical Journal International 167(1): 445-452. DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17777
Deposited By: Tony Diaz
Deposited On:22 Mar 2010 17:34
Last Modified:08 Nov 2021 23:38

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