I’ve been using an app called Sleep Time on my iPhone to track my sleep patterns. So far, it has revealed that my average bed time is waaaay too late (which I knew), that my average night’s sleep is shorter than it probably should be (which I knew), but that when I am asleep I sleep “efficiently” (i.e. lots of deep/REM sleep) (which I didn’t know). Monday night, I didn’t get a lot of sleep – couldn’t fall asleep until quite late and then I had to wake up earlier than usual and was zombie-like for most of the morning.
Looking at the graph for Monday night, it appears that just as I was getting into deep/REM sleep at 4am something disturbed my sleep and cut my deep sleep cycle short, which would correspond to when the magnitude 4.2 earthquake rattled the area in the wee hours of Tuesday morning.