This is similar to the observation that all of a sudden there are more and more tornadoes in the US and this is proof of "global warming" or
something.
But in fact most if not all meteorologists say this is a result of more people living in areas that were sparsely populated. In other words, the
tornadoes were always there, its just people weren't seeing as many because they weren't out there to see it!
I believe its the same situation here. More accurate instruments, more people, larger populations, better ways of recording the seismic jolts and
making the measurements more precise all add up.
My two cents!