Volcano Watch: Seismic halfalogues — Earthquakes are only part of the conversation

  • Ninety seconds of raw seismic data from four seismic stations around Kilauea summit. Dates and times, at the bottom of the graph, are in Coordinated Universal Time (UTC). The stations captured two types of seismic signals we typically observe in volcanic settings: (left) a typical tectonic earthquake signal, which results from rocks breaking free and sliding against each other; and (right) a magma-related earthquake signal, which typically results from reverberation of magma. The difference in the frequency of the vibration is starkly noticeable as the magma-related signals (right) have wider-spaced peaks and troughs when compared to the tectonic earthquake signals (left). (USGS/Special to West Hawaii Today)

Earthquakes are a volcano observatory’s early warning system; the first page of action in our page turning story. It’s very difficult to move molten magma through solid rock without making some sort of “noise” or vibration that isn’t picked up by seismometers. So we often “hear” magma coming before it erupts as lava at the surface.