The 2017–2018 Maple Creek Earthquake Sequence in Yellowstone National Park, USA

Abstract

AbstractWe explore the detailed spatiotemporal evolution of 3,345 earthquakes that occurred near Maple Creek, Yellowstone, for the time period of 12 June 2017 to 13 March 2018. We generate high‐accuracy relocations and near source VP/VS ratios using 4.4 million P wave and S wave differential travel times derived from waveform cross correlation. The hypocenters can be subdivided geographically into two major subpopulations: a northern cluster with planar structures striking mainly NW‐SE and a southern cluster with planar structures striking mainly E‐W. We observe VP/VS ratios of 1.39–1.66 in the northern cluster and a steady ratio of 1.50 in the southern cluster, suggesting the presence of CO2‐filled cracks. We interpret the northern earthquake cluster primarily as long‐lived aftershocks of the 1959 Mw 7.2 Hebgen Lake earthquake but with some influence of magmatic fluids. We interpret the southern earthquake cluster as a more classic, swarm‐like sequence induced primarily by the migration of magmatic fluids.