Several volcanoes along the Aleutian-Alaskan volcanic arc have been imaged using ground vibrations caused by local earthquakes, yet these images of the subsurface can only be constructed for depths above these earthquakes. There is growing interest to image the subsurface of these volcanoes using receiver functions, which capture changes in seismic waves that travel through the entire globe and pass through layers directly under a seismic station. Our previous study used receiver functions to image Akutan volcano, identifying faults and dike fabric that form a concentric pattern around the center of the caldera.

We examine other volcanoes in the same volcanic arc with receiver functions and identify two patterns of their subsurfaces: concentric fabric patterns centered at the caldera of volcanic systems and fabric strikes that are parallel to the arc and subduction zone. Using methods similar to those applied at Akutan volcano, we image the subsurface beneath Okmok and Spurr volcanoes, both of which show signs of concentric magmatic structures.

Okmok is classified as a “high threat” volcano, and Spurr, the closest volcano to Anchorage, Alaska, experienced heightened volcanic unrest earlier this year. Detailed overviews of their subsurfaces may aid volcano monitoring and eruption forecasting at these locations.