Seismologists have detected a hidden tectonic microplate called the Yakutat beneath Alaska, which had long remained invisible to researchers. The key to uncovering it was a chain of roughly three thousand microscopic earthquakes that formed a perfectly straight line stretching 250 kilometers.
A team of scientists from the Australian National University deployed a network of highly sensitive temporary seismic stations south of the Denali Fault to investigate the region’s abnormally high seismic activity. Instead of the expected major tremors, the instruments recorded about three thousand previously undetected microquakes. These tiny underground shocks created a remarkably clear linear structure running from northwest to southeast directly beneath the Alaska Range.
The discovered line of microearthquakes pinpointed the exact boundary of the hidden Yakutat tectonic plate. This block of Earth’s crust formed millions of years ago as a massive oceanic plateau but later became deeply buried through the process of subduction, where one plate shifts beneath another. Due to its unusual thickness and high buoyancy, the Yakutat plate does not sink into the mantle. Instead, it literally pushes the Earth’s crust upward, forming the Alaska Range. Scientists believe this extreme pressure shaped Mount McKinley, the highest peak in North America.
The chain of microearthquakes perfectly aligned with the positions of small ancient volcanic cones and a sharp change in rock types at great depth, confirming the hypothesis of the plate boundary. Of particular interest is the fact that the discovered line exactly crosses the epicenter and the initial rupture point of the devastating magnitude 7.9 earthquake that struck in 2002. At that time, the echoes of this catastrophe even reached as far as Seattle.
The results of this extensive work have been published in the journal The Seismic Record. According to the study’s authors, the rigid leading edge of the Yakutat plate absorbs the main tectonic pressure, accumulates stress, and channels seismic energy directly toward the surface. In the future, geologists plan to use this data for computer modeling of processes, which will allow more accurate predictions of strong earthquakes in the region.
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