Torsional pendulums and earthquakes

The shaking here in Hamilton is hardly on the scale of Seddon and Wellington, but it does mean my students aren’t going to get anything meaningful out of their measurement of the gravitational constant this afternoon. The Cavendish experiment uses a sensitive torsional pendulum, whose motion is currently more dominated by ground movement than by gravitational attraction. I can’t feel anything, but we can clearly see the effect on the equipment. Hope everyone is safe further south.