Archive for Christchurch Earthquake

Rolling Boulders…

Posted in Bad Statistics, The Universe and Stuff with tags , , , , , , , , on October 13, 2012 by telescoper

I’m a bit slow to get started this morning, since I didn’t get home until the wee small hours after a trip to the Royal Astronomical Society yesterday, followed by a pleasantly tipsy dinner at the Athenaeum with the RAS Club. Anyhow, one of the highlights of the meeting was a presentation by Prof. Gerald Roberts from Birkbeck on Marsquakes: evidence from rolled boulder populations, Cerberus Fossae, Mars.  The talk was based on a recent paper of his (unfortunately behind a paywall), which is about trying to reconstruct the origin and behaviour of “Marsquakes” using evidence from the trails made by rolling boulders, dislodged by seismic activity or vulcanism.  Here is a sample picture showing the kind of trails he’s using – the resolution is such that one pixel is only 20cm!

There are enough trails to allow a statistical analysis of their distribution in space and in terms of size (which can be inferred from the width of the trail). I had some questions about the analysis, but I haven’t been able to read the paper in detail yet so I won’t comment on that until I’ve done so, but the thing I remember most from the talk were these remarkable pictures of what a rolling boulder can do on Earth. They were taken after the earthquake in Christchurch, New Zealand, in 2011.

A large boulder was dislodged from the top of the hill behind the house in the second picture. It didn’t just roll, but bounced down the slope (see the large furrow in the first picture; similar bouncing trajectories can be seen in the picture from Mars), smashed straight through the house, exited the other side and came to rest on a road. Yikes.