Friday, November 21, 2008

Passive Continental Margins

This is a new book that sounds interesting. I can't afford to buy it, because my ad money is dedicated to wine, and I'm soooo close to my first 100 bucks, I can taste it!

A passive continental margin seems to be a more remote source of giant earthquakes, but nevertheless, it happens.

Does this resemble some place you know? That's right, it's Hawaii! The margin is always accumulating sediment from the rivers, minus all the overfishing. This slowly makes it a lot heavier. At the same time, the oceanic crust is cooling, making it slowly sink.

Once in a while it decides to rip! For something like Lisbon, it probably ripped for over a thousand klicks, while activating a ton of underwater sediment 'landslides'. This made for some huge tsunamis!

I find this fascinating with regard to the source mechanics. There aren't a lot of minor earthquakes dotted along the edge. This probably means that the fault is as smooth as a bathtub, and only tends to rupture in large bursts. Most faults are 'fractal rough', and have a lot of smaller earthquakes setting things up.

This type of earthquake is a threat to all the coastal cities, such as New York, but I think they are a very slow rate phenomenon. In other words, New York will get hit by local large quakes, before something like this happens.


hypocentre said...

Ah, but is it a passive margin 'quake?

Or was it due to the subduction of the Alboran plate beneath southern Spain???

Harold Asmis said...

Yes, my head hurts at the thought!