[Baps] Sarah Stewart EPS 2010 Colloquium talk "Impact crater formation via dynamic fault weakening" on Monday, March 29th, please see enclosed abstract

[Sarah Stewart-Mukhopadhyay]

Harvard EPS Colloquium:

*Please join us for our next Spring 2010 Colloquium* on *Monday, March
29th@ 4pm:
*

*Sarah Stewart-Mukhopadhyay*

Harvard University

(http://www.fas.harvard.edu/~planets/stewart.html<http://www.fas.harvard.edu/%7Eplanets/stewart.html>
)**

"Impact crater formation via dynamic fault weakening"

*
*

*Colloquium will be held in Haller Hall*

* (Geo-Museum 102)
Please join us for a reception following the talk, in the 4th Fl. lounge of
Hoffman*



Abstract:

Impact craters are the most common landform on planetary surfaces; however,
the mechanics of the final stage of crater formation is still not fully
understood. The end stage of formation involves the collapse of a
hemispherical transient cavity. Around small craters, the limited amount of
collapse preserves a bowl-shaped cavity. In contrast, the observed shallow
depths and complex inner morphologies of large craters require very low
shear strength in the collapsing material. Because the observed amount of
collapse cannot be reproduced using quasi-static (laboratory) values for the
frictional strength of fractured rock, a temporary weakening mechanism is
necessary. Currently, most researchers assume that acoustic waves
transiently fluidize the rock. I will present simulations investigating an
alternative hypothesis that craters collapse along a network of
impact-generated faults that weaken during long displacements at high slip
velocities.  The model reproduces the simple to complex crater transition
and major geologic features observed around terrestrial craters. Finally, I
will discuss implications for the formation of multi-ring impact basins and
applications to planetary evolution.
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