Volcano Watch: Separating signals — what matters to seismologists?

The seismogram tracks 24 hours of signals at station WRM, just west of Halemaʻumaʻu crater at the summit of Kilauea. Examples of spectrographic helicopter noise, a small VT event and a larger VT event are given below the seismogram. (Courtesy photo/ HVNP)

Whether they originate above or below the Earth’s surface, a wide array of signals appear on the USGS Hawaiian Volcano Observatory’s earthquake-detecting (seismic) data streams. Part of a seismic analyst’s duty is identifying normal versus irregular seismic activity.