Correlation is certainly not necessarily causation, and improved monitoring can certainly skew the data, but if you check the records on wiki or elsewhere, there have been about 150 earthquakes over 7 (the usual definition of 'major or great') since 2000 (the date where your graph stops, and only about 50 from 1970 to 2000. It is not my specialty, but I don't know of any major breakthrough in seismology technology that would have increased our ability to sense earthquakes by about ten times in 2000. So presumably there has been some significant level of increase in the last ten years over the long term average. I am inclined to assume that the fact that this coincides with the period when the effects of GW, especially of large ice bodies, really started to accelerate dramatically. But it does not strike me as on the face of it an utterly inane question whether ice cap melting and sea level rise has or could affect pressure points in plate tectonics, some of which are apparently on hair triggers, ready to go off explosively with the slightest forcing.
Worth reading the statement called earthquake myths at the USGS
http://earthquake.usgs.gov/learn/faq/?faqID=110
It is noted the frequency/energy release of earthquakes since 2000 though increasing on average over the past 10 years pales in comparison to where it was from 1900 through to 1930 when it was much higher and for which you could not possibly draw a correlation with melting ice caps or rising sea level.
http://www.johnstonsarchive.net/other/quake1.html
The number of rock mechanic principles you would have to completely ignore to suggest that crustal response to melting ice in the Artic has any influence on Japan trench tectonics boggles the mind.
As to correlation and causation Lubos Motl had an interesting tongue in cheek observation:
In particular, the Japanese earthquake was caused by iPad 2 which is being released exactly today while iPad 1 was released exactly one year ago, i.e. 2 weeks after the Chilean earthquake. At the time of the Indonesian tsunami, Apple changed its suppliers and opened its first store in Europe (London) and sold its 200-millionth song via iTunes.
Apparently it is all to do with the number of people storming to the apple stores and creating unequal loading in the continental crust!