Open Access

The March 25, 1998 Antarctic Earthquake: Great earthquake caused by postglacial rebound

  • Seiji Tsuboi1Email author,
  • Masayuki Kikuchi2,
  • Yoshiko Yamanaka2 and
  • Masaki Kanao3
Earth, Planets and Space201452:BF03351621

Received: 18 May 1999

Accepted: 10 December 1999

Published: 20 June 2014


A large Mw = 8.1 earthquake occurred off southeast coast of Antarctica near the Balleny Island region on March 25, 1998. We inverted teleseismic body-wave records to determine the rupture pattern using an iterative deconvolution method. The source parameters obtained are: the centroid depth=20km, (strike, dip, rake)= (282, 83, −1), the seismic moment M0 = 1.6 × 1021 Nm (Mw = 8.1), the length L = 200 km, and the average slip D = 4.4 m. This earthquake occurred in the mid-plate but there has been no reports of such large earthquakes in this region. Furthermore, the source mechanism cannot be related to the plate motion inferred from the nearby transform faults. Therefore this earthquake is not a usual tectonic event. Here we show that the compressional axis of our source mechanism coincides with the horizontal crustal motion predicted by the Earth’s response to present-day and past ice mass changes in Antarctica. Our result suggests that the 1998 Antarctica earthquake is caused by the postglacial rebound in the Antarctica.