The magnitude 6.2 earthquake that struck Amatrice last night (01.36 GMT) was similar to the m6.3 quake that hit L'Aquila in April 2009. Both occurred at a shallow depth (which exacerbates the shaking at the surface) and resulted from local extensional faulting in this tectonically complicated region.
However unlike the L'Aquila quake, which was preceded by swarms of smaller quakes and led to claims (unjustified in my view) that the eventual big quake should have been predicted, this one appears to have struck out of the blue as is more usually the case.
It is too early to asses the full nature of the damage. I would expect older buildings and bridges to have suffered worse than modern structures, which should have been constructed according to well-known seismic resilience codes.
Update at 10am
Aftershocks are continuing.
Journalists might like to visit http://www.centrometeoitaliano.it/terremoti-in-tempo-reale-italia-mondo-ingv/
I captured the screen grabs below from there at 0935 BST:
The biggest aftershocks have been magnitude 4. These were in the two hours immediately after the initial earthquake. Currently aftershock sat in the M2-M3 range.
They can be expected to generally become weaker, but the occasional stronger aftershock cannot be ruled out. People close to the epicentre of a weak aftershock may feel it more strongly than the original earthquake, thigh the shaking will not last for so long.
Aftershocks can bring down buildings already weakened, and put at risk those trying to rescue people tapped in rubble.
The Guardian's Wire Service has published some video of the rescue efforts: