Largest US quake in half-century causes Alaska little damage The magnitude 8.2 earthquake struck just south of the Alaska Peninsula. By MARK THIESSEN Associated Press July 29, 2021 — 8:10pm Text size Copy shortlink: ANCHORAGE, Alaska — The largest earthquake in the United States in the last half century produced a lot of shaking but spared Alaska any major damage in a sparsely populated region, officials said Thursday. The magnitude 8.2 earthquake was reported about 10:15 p.m. Wednesday, and it struck just south of the Alaska Peninsula, nearly 500 miles (804.67 kilometers) southwest of Anchorage. The quake was about 60 miles (96.56 kilometers) offshore and 29 miles (46 kilometers) below the surface of the North Pacific Ocean, according to the U.S. Geological Survey.