Seismic ground velocity signals

The top plot shows a 2013 seismic recording of a normal shallow magnitude-2 earthquake that occurred a few miles south of the summit of Kīlauea Volcano. The bottom plot shows a 2013 seismic recording of magma resonance after a large rock broke off the Halema‘uma‘u crater walls at the summit of Kīlauea Volcano and then impacted the lava lake surface. Note the different timescales; the normal earthquake only lasted for about 20 seconds in total, whereas each magma oscillation cycle lasted for 40 seconds and the vibrations continued for over 20 minutes in total.