It's because of the intensity, primarily. There are small quakes all the time, most not even felt. The one last week was the largest in a while.And are these quakes just being mentioned because of the number or is this a cluster that's larger than usual?
It's common with a significant quake to have aftershocks, and sometimes the first quake or first several are actually foreshocks. In June of '89, we had a decent little shaker in the Santa Cruz area (I was living in Santa Cruz then), and it was not until after the big Loma Prieta quake in October of that year that it was recognized as being a foreshock.