Thousands of small earthquakes, detected for the first time by a machine-learning process, reveal the distinct, razor-sharp edge of the Yakutat microplate as it subducts beneath the North American plate.
The Yakutat oceanic plateau is caught in the middle of a tectonic traffic jam with the Pacific plate as it subducts beneath the North American plate. The position and structure of the plates in this congested zone play a significant role in the earthquake and volcanic landscape of south-central Alaska.
The research published by Meghan Miller of Australian National University and her colleagues in The Seismic Record now shows the edge and extent of the Yakutat plate in astonishing detail.
Using data collected by permanent and temporary seismic stations, including a temporary array deployed by the researchers from 2018 to 2021, Miller and colleagues used a machine-learning workflow to develop an expanded earthquake catalog for the region.
Their analysis revealed a 250-kilometer-long linear cluster of about 1,750 earthquakes running northwest to southeast—a cluster that had never been identified in previous studies.
Using ambient seismic noise data to further map the region at depth, the researchers conclude the line of earthquakes marks the edge of the Yakutat microplate as it slips shallowly and directly under the North American plate, without an intervening mantle wedge, as often occurs in subduction zones.
The new extent of the Yakutat microplate places it directly below the apex of curvature of the Alaska Range and the Denali Fault, the major continental fault system in south-central Alaska.
The view north from Station 3 in the temporary deployment in south-central Alaska by Meghan Miller and colleagues. Credit: Sarah Roeske