Here's the reply from NSIDC:
Hello Mr. Garrett;
Living in California, I'm sure you know that a 4.5 M earthquake is rather
small; also, strike-slip quakes don't usually form tsunamis, because that
requires some large component of vertical motion.
But the notion in general is a good one, and we looked carefully for
evidence of an effect from the massive 2004 Sumatra tsunami (Dec 26,
2004), orders of magnitude larger than the event you've found; very little
if any effect could be detected on the Amery Ice Shelf or other shelves
along the Indian Ocean coast of Antarctica.
Still, long-period waves, from winds, may have an effect on pushing an ice
shelf that is already unstable 'over the edge'. The current model is that
ice shelves begin to accumulate more and more surface melt, until free
water (melt lakes or soaked snow) cover the surface in late summer; then,
some event, perhaps a train of long-period waves, triggers a break-up.
In the case of the Wilkins bridge, my colleagues and I currently think
that stresses from the large shelf area to the south of the bridge
gradually pushed the bridge until it cracked; water in the snow layers
beneath the surface accentruated fracturing, and the bridge disintegrated.
We know that the shelf had thinned by several 10s of meters in the past
few decades, as well.
best regards,
Ted Scambos.
See on the web:
Scambos et al., 2009, Earth and Planetary Science Letters;
Braun et al., 2008, The Cryosphere Discussions and The Cryosphere
MacAyeal et al., 2003, Journal of Glaciology
see also
www.lajollasurf.org/gblpac.htmlremember, shelves and icebergs survive normal waves, even storm waves, all
the time: a warming climte is required to make them susceptible.