My monitor is rattling

So it was yesterday. As we sat quietly typing in our office with the hum of the fluorescent lighting and A/C fans in the background on the 2nd floor of our 4 story office building, someone noticed that we seemed to be 'moving'. Kind of rolling a bit up, down, lateral...very minor but noticable.

We get tremors here, on rare occasions. You usually have to be really observant to pick them up. Maybe you'll move a bit, maybe a hanging light will slightly sway or you'll hear a rattle of something loose. This ain't the San Andreas fault we're on but this seemingly solid Earth we sit on isn't so solid. Stuff moves. Ground can push up at fault lines and create mountains (over really long periods of time, mind you!). In our case, it's a remanant of massive glaciers that sat over Ontario and Quebec 10,000 years ago. The weight pushed the ground downwards and after they've long since thawed and flowed away, it's been slowly rebounding ever since.

Yesterday's 5.0 quake was centered near the Quebec border, remarkably close to this 4.0 tremor from Feb. 24, 2006. I'm guessing that particular area had a pretty big pack of ice on it.

Apparently quakes and tremors in this area spread out over very long distances in their affected regions, probably something to do with the lack of distinctive fault lines that absorb a lot of the motion. This one was felt well down the eastern seaboard of the States, although almost not at all east of the epicenter. There is one large fault line that runs N/S in central Quebec that probably contributed to it's lack of effect to the east.

As the rolling sustained, gently, for several seconds, it quickly elevated to some pretty distinctive shaking, as my monitor, pictures and other items on my desk began shacking about, enough that I thought my monitor would topple over. This prompted a spontaneous evacuation of the building by it's residents and the same from most of the other nearby buildings as people quickly flooded the parking lots and sidewalks. I stayed back and checked USGS to see what was up and got a quick posting in on chrunners even as the shaking was happening, whiched recorded my post at 1:43:57, approximately 2 minutes after the epicenter event (about right for wave propogation effects outward from the source).

Pretty neat stuff. There's something fascinating about knowing the Earth isn't just a solid ball floating around in space.