The largest oceanic intraplate earthquake ever detected and the largest event worldwide since 1994 occurred in a remote oceanic region near the Balleny Islands on March 25, 1998 (03:12:26 UT; Mw 8.2). An intraplate earthquake of this magnitude is extremely rare, especially for the Antarctic plate, which shows low seismicity.

The earthquake occurred about 300 km west of the Balleny Transform between the Antarctic passive margin and the Australian-Antarctic spreading center (Figure 1). The best double-couple mechanism from the Harvard Centroid Moment Tensor (CMT) solution shows strike-slip faulting with nodal planes trending north-south and east-west (Figure 1). The CMT solution also shows a large, compensated linear vector dipole (CLVD) component that can be interpreted as indicating northwest-southeast extension.