Statistical analysis of seismicity in a wide region around the 1998 Mw 8.1 Balleny Islands earthquake in the Antarctic Plate

A large earthquake (Mw 8.1) that occurred off the North Coast of the Antarctic continent near the Balleny Islands on 25 March 1998 was the largest intra-plate earthquake ever recorded in the Antarctic Plate. The earthquake hypocenter catalog for this area shows a marked change in seismicity following the main shock in a large area around the Balleny aftershock region. However, the earthquake catalog includes many aftershocks and is affected by a variable detection rate. To overcome these limitations, we applied statistical models and methods, including Gutenberg-Richter’s magnitude frequency distribution, the Epidemic-Type Aftershock Sequences (ETAS) model, and the space-time ETAS model, thereby enabling calculation of the change in detection rate. The results show a change in the spatial pattern of background seismicity over a large region after the 1998 event.