When it Happens
There does seem to be a rough pattern to when the vibrations happen. I’ve made the following observations:
More frequent and lasts longer during the day than the night
Morning and evenings are generally worse
The daytime pattern stops anywhere between 7 PM and 11 PM and starts back up anywhere between 4:30 AM to 7 AM.
There are periods when it is particularly bad (higher amplitude and more often). Bad and good (not-as-bad) periods can last for a few days to a few weeks. If the previous nights were bad, there is a greater likelihood that the following night will be bad.
Weekdays are worse than weekends (At night anyways)
There doesn't seem to be any seasonality or weather correlation
Some nights there is an on/off cycle at regular intervals, that can last for several hours
The Best Nights
There are nights when it doesn’t happen very much. On these nights the last time it might occur is 9 PM and it doesn’t start again until early the following morning. That might be anywhere between 4:30 a.m. to 7:00 a.m.
Not great, but at least tolerable.
The Worst Nights
On the worst nights, the disturbance occurs almost continuously after dinner time until 10 - 11 p.m. On these nights, the baby might wake up 10 times or more before we go to bed. The toddler has a very hard time falling asleep while the house vibrates.
Then sometime between midnight and 2 a.m. the vibrations starts. We have noticed periods that are really bad, then periods where we are able to sleep a little. The cycle continues all night.
On these nights we get almost no sleep at all and are exhausted in the AM.