Backazimuth map showing infrasound directions that converge on Giant Geyser, Yellowstone National Park, when it erupted on September 10, 2026

Acoustic signals recorded at infrasound arrays (red inverted triangles) YBB (in Biscuit Basin) and YGH (near Geyser Hill), in Upper Geyser Basin, can be used to determine the direction from which low-frequency acoustic signals originated, also called the backazimuth.  This example is from 9:14 p.m. MDT on September 10, 2026, when both arrays recorded a strong signal.  The backazimuths converged on Giant Geyser (yellow star), which started erupting at that time and was the source of the infrasound signal.