Earlier I posted an info bulletin about this morning’s Banda Aceh earthquake. Rather than muddle it with more and more stuff, I thought it might be better to include this update as a separate post, as it is more of a discussion than a news piece in any case.
The truth is that this earthquake is properly strange.
The part of the Indian Ocean in which this earthquake occurred has two very different types of geologic structure very close to each other; there is the Ninetyeast ridge – a volcanically produced range, and a destructive margin subducting the Indian plate eastwards under the Pacific margin. It is important to note (in the context of this earthquake at least) that the sea floor under the Ninetyeast ridge was originally produced by standard constructive margin seafloor spreading.
These two structures are shown quite nicely in this image taken from GeoMapApp, with…