Well, what caused it is a matter of debate – if you go to Piers Corbyn's web site he predicts earthquakes from solar and lunar cycles, and sun spots. What caused the earthquake is therefore open to question but a whole lot of research articles have been published as the tsunami wave generated by the earthquake was so horrifying for the people of Japan in its path. At www.sciencedaily.com/releases/2013/05/130501101307.htm … the earthquake is in effect a landslip at a fault line – shifting by 50m or more. Pressure and temperature sensors were installed around the fault zone as well as a bore hole observatory. At www.sciencedaily.com/releases/2013/12/131205170103.htm … we have the results. A paper in Science journal (Dec 5th) determined the fault was more slippery than anyone expected. Friction generates heat but friction was very low. Friction is the point of resistance to movement at the fault – slowing it down. The friction was low and that explains why the slippage was so extensive. An abundance of clay material at the fault zone appears to be a major factor in the slippage – and how quickly it proceeded.
The fault is described as a subduction zone, mainly because it drops down into the Japan trench (which is assumed to be evidence of subduction, although that has not actually been observed). The fault is therefore considered to be a plate boundary – which is all part of consensus Plate Tectonics theory (which is a hypothesis in spite of being widely disseminated in science literature). However, the presence of so much clay at the fault boundary is only one part as the actual fault zone was less than 5m thick – which is very narrow for a plate boundary. Is it really a plate boundary?
At www.sciencedaily.com/releases/2013/12/131205141316.htm … there is more on what is described as an unusually thin slippery geological fault that caused a massive displacement of the sea floor. It is remarkable that the scientists have concentrated on the geology but western media, since March of 2011, have universally concentrated on the nuclear power stations that were flooded (where no people died) and have largely ignored the enormity of the tsunami wave (which killed thousands of people). One wonders if this might have left a sour taste in the mouth of many Japanese as the journalists appear almost totally to have sourced Green PR and Green doomsayings without looking at the human dimension – or the stoic behaviour of the Japanese survivors. I suppose if they had been bellyaching like the New Orleans Katrina survivors they would have had something to spread across their increasingly irrelevant pages but a stiff upper lip and the ability to survive with little complaint flummoxed the press and the TV media. All we got was the doomsaying about nuclear power – and the German government, harassed by the Greens, decided to phase out their nuclear power stations – and rely on wind. That quickly changed once it was realised how inefficient the wind mills were – and now the Germans are building coal fired power stations. Not a bad idea as coal is cheap in comparison with every other fuel – a foil to balance the enormous expense and dependence on wind in Germany (as a result once again of Green policies). This may account for the Japanese decision to ignore climate change and renewables, sort of sticking their fingers up at the Warsaw climate jamboree where rich kids and their sugar daddies get to shout and scream at politicos and the plebs that vote them in. We learn here that the fault zone is the thinnest, or most narrow, plate boundary so far measured.