The Yakutat microplate has emerged as a significant component of the geologically complex southern Alaska region. This microplate has been moved northward via margin-parallel transform faults, such as the Queen Charlotte and Fairweather faults. Upon reaching the southern Alaskan continental margin, it has initiated ongoing collisions, resulting in intricate seismotectonic interactions that contribute to one of the most seismically active areas in the United States.
Historically, this region has experienced several major seismic events. In 1899, two major earthquakes registered at magnitudes of 8.1 and 8.2, leading to substantial alterations in landforms around Yakutat Bay. These earthquakes were responsible for uplift of nearly 40 feet and subsidence of 6 feet in certain areas. Another significant seismic occurrence was the 1958 Lituya Bay Earthquake, which measured M7.7 and ruptured along the Fairweather Fault. This event triggered a massive landslide into Lituya Bay, resulting in an extraordinary tsunami wave that reached an astonishing height of 1,720 feet.
Further adding to this tectonic history, the Saint Elias Earthquake of 1972, which reached a magnitude of 7.4, marked another crucial event in the region’s seismic narrative. In terms of offshore geology, the Transition Fault, which delineates the boundary between the Yakutat microplate and the Pacific Plate, features prominently alongside the northern Gulf of Alaska fault zone. The Gulf of Alaska itself has been the site of significant seismic activity, including strong earthquakes in 1987 and 1988, which registered magnitudes of 7.7 and 7.8, respectively. These events generated widespread ground motions that were felt throughout the southeastern and southern coast of Alaska.
Overall, while the Transition Fault has seen relatively minor activity, including a notable M6.7 earthquake in 1973, the region is characterized by high seismicity. Hundreds of earthquakes occur annually, most of which are shallow and concentrated within the 50-mile-wide coastal zone, indicating an ongoing geological dynamism. The presence of such geological activity serves as a reminder of the Earth’s power and the importance of continued monitoring and research in understanding these complex interactions.