Why is my bed shaking?!?

I didn't think that I would be writing a sequel so soon, but yes we had another earthquake this morning at 5:07 A.M. After reading reports, it seems to have hit Tokyo and surrounding areas at a 6.4 magnitude. I'm not sure what number that translates to on the shindo scale (measures the degree of shaking) that would have been felt here in Yokosuka, but we are only about 2 hours south of Tokyo. Ryan was sleeping with Kaylee and I was with Abby in the other bed. There was quite a jolt which woke Ryan and I up immediately. We sat there looking at each other in opposite beds waiting for the shaking to stop. This earthquake felt much longer than the Sunday night quake, but Ryan disagrees. Eventually, the shaking slowed and then stopped. Fortunately, the girls slept through the whole thing. I thought I felt a few tremors afterwards, but now I think it was just my hurt beating so hard and fast from being nervous.
Ryan's co-workers, who have lived here longer than we have, said that in the past year and a half, the two latest earthquakes have been the worst. I'm not sure if that's a good thing or not...maybe the quakes are not so bad...or they are just going to get worse?
Japan averages about 1,500 earthquakes a year. The biggest earthquake in Japanese history occurred on September 1, 1923 at a magnitude of 8.3 killing 143,000 people and on January 16, 1995 in Kobe, Japan an 6.8 earthquake shook the city killing 5,530 people....Does this mean Japan is due for another big one? That's what many of the Japanese locals say, but I just hope it holds off for at least three more years!!!