This afternoon while teaching class I was explaining one of the parts of the instrument when I started feeling a bit shaky. Then there was a sharp jolt that felt like something hit the building.

I was sitting down on a small stool, or I may not have felt much movement. Most of my students felt it, but one was walking across the room and didn’t.

Of course, I had to check with USGS and see how big the earthquake was and how far away it was.

In the map above it is the orange dots near the center.

The epicenter was about 12-15 miles from our office. The quake is on the Greenville fault which is the least understood fault in the Bay Area. The fault has not had significant activity since 1980 when there were a 5.8 and 5.4 earthquake that January.

This quake was a 4.3, which is technically not significant as the threshold for a significant quake according to the USGS is 4.5.

There were a few aftershocks, but all within an hour of the initial quake. Since it has been some time since there was quake this large on the fault, there is potential for more aftershocks in the next few days.

I also looked at the shake map, and the quake was felt over the entire Bay Area and up and down the Central Valley.

It will be interesting to see how many aftershocks there will be, and if there will be other activity in the Bay Area. We have fortunately not had much activity in the past years.

There was a lot of discussion in the office as everyone talked about whether they felt it or not and what they were doing. One of the other trainers was reminded that it has been several years since he updated his emergency pack.

I was thinking about how many quakes I have felt since I moved to California almost 20 years ago. I can only remember about half a dozen here, but remember more from trips to Japan and Taiwan.

Steven