Tremor and spike

On Nov. 4, a tremor, possibly from a nearby quarry blast, propagated through the earth in the Chicagoland area. Some of Fermilab’s monitors were able to easily detect it. In the above plot, the blue trace is a tiltmeter in the Tevatron. These devices have always proven to be good earthquake detectors. The red and green traces are peak readings from some geophones on the detector in the MINOS hall, which respond to higher frequency vibrations. Image courtesy of Todd Johnson, AD