Schematic model showing a cross section of Old Faithful's plumbing

Schematic model showing a cross section of Old Faithful's plumbing system as determined from seismic studies. The red circles (t0-t3) show the location of the tremor source over time, and how the tremor source migrates upward prior to an Old Faithful eruption. Times between red circles are based on a 93-minute eruption interval. Taken from an article by Wu et al., 2019, in Geophysical Research Letters, doi: 10.1029/2018GL081771.