36th DPS Meeting, 8-12 November 2004
Session 16 Jovian System
Poster I, Tuesday, November 9, 2004, 4:15-7:00pm, Exhibition Hall 1A

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[16.11] Mountain Strike Orientations on Io: Evidence for a Global Stress Pattern.

M. Kirchoff, W. B. McKinnon (Washington Univ., Saint Louis), P. M. Schenk (LPI, Houston)

The majority of Io's mountains are isolated, tectonic thrust blocks, and are concentrated in two broad regions ~antipodal to each other and anticorrelated at low spherical harmonic degree to the distribution of volcanic centers (Kirchoff et al. 2003, EOS 46, F962, and submitted). Dominant horizontal directions (presumably, strikes of thrust hinges) have been determined for these mountains from Voyager and Galileo images. In a coordinate system whose axis is centered on the regions of mountain concentration, the strikes of the mountains within the regions of concentration show a preferential orientation perpendicular or subperpendicular to lines of ``longitude" (see fig.). The distribution of strikes outside the regions of concentration is consistent with being random. It is interesting to note that axially symmetric, in-plane compression of an elastic spherical cap gives meridional (colatitudinal) principal compressive stresses greater than circumferential (longitudinal) principal compressive stresses, broadly consistent with the distribution of observed fault strikes within the regions of mountain concentration. Possible explanations for such in-plane compression are 1) basal drag due to an asthensopheric ``magma wind" from regions of maximum tidal heating (and volcanic activity) and 2) enhanced lithospheric compression due to greater crustal burial and subsidence in regions of greater volcanism.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.