According to the classical theory of plate tectonics, oceanic transform faults do not usually have “large” or “great” earthquakes. In this paper, we discuss several transform fault earthquakes, some now moved into unusual tectonic settings due to plate motion, which did have earthquakes lying in the magnitude range 7.8 ≤ Mw ≤ 8.1. The 2004 Mw8.1 earthquake occurred on a fossil fracture zone in the Tasman Sea. The 2000 Mw7.8 earthquake occurred in the Wharton Basin and ruptured two conjugate faults simultaneously. The largest known strike-slip earthquake in 2012 (Mw8.6) occurred off the coast of Sumatra and ruptured cross-cutting faults. An oceanic strike-slip earthquake in 1998 with Mw8.0 occurred on the Antarctic plate, but on a fault parallel to the ridge and nearly normal to the transform faults that is, it occurred on the ridge fabric! All these earthquakes together with the 2012 twin earthquakes (Mw8.6 and 8.2) in the Wharton Basin, the 1987–1992 (6.8 ≤ Mw ≤ 7.8) Gulf of Alaska sequence and the Mw7.9 2018 Gulf of Alaska earthquakes, show that the oceanic lithosphere is breaking up along the ridge-transform conjugate fault systems under tectonic stresses.
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