Example of Yellowstone seismic data showing sequence of small earthquakes for which a magnitude could not be determined

Example of a Yellowstone seismic waveform recorded at station YMC (at Maple Creek in the northeast part of Yellowstone National Park) with earthquakes for which a magnitude could not be determined. The magnitude was therefore set at -9.99 in the University of Utah Seismograph Stations catalog. The gold area highlights one event, but there are several others close by. The entire window is ~1 minute long. The close occurrence of several earthquakes in such a short time window and their small magnitude values make it a challenge to calculate an earthquake magnitude for any of these events.