Tiny earthquakes map hidden edge of Yakutat microplate in Alaska

A network of seven newly installed seismometers south of Alaska's Denali Fault has recorded roughly 3,000 previously undetected micro-earthquakes that line up in a straight, 155-mile (250-kilometre) pattern beneath the Alaska Range. The linear swarm marks the leading edge of the Yakutat microplate, an oceanic plateau that is thicker and more buoyant than the surrounding Pacific crust and is currently being subducted beneath the North American Plate.

The Yakutat block, formed by ancient volcanic activity, pushes up the Alaska Range, which includes North America’s highest peak, Denali. Researchers say the precise location of the subducted portion of the plate has been difficult to determine, but the newly identified seismic line aligns with a series of small volcanic cones and changes in rock type at depth.

"Being able to identify where the Yakutat microplate is in the subsurface has helped us understand the tectonics," said Meghan Miller, the study’s first author and a seismologist at the Australian National University.

The team suggests that the plate’s edge may focus seismic energy toward the surface, potentially influencing the development of small volcanoes and contributing to larger earthquakes, such as the 2002 magnitude-7.9 Denali event that originated on a nearby fault. Further computational modeling will be needed to explore this hypothesis.

The findings were published on June 4 in the journal The Seismic Record.