The 1998 Papua New Guinea earthquake occurred on July 17 with a moment magnitude of 7.0 and a maximum Mercalli intensity of VIII (Severe).

Within this overall setting, the active tectonics of northern Papua New Guinea is dominated by the effects of continuing collision between the Huon–Finisterre island arc terrane with the edge of the Australian continental margin.

The tsunami was originally thought to have been caused by a 2 m (6 ft 7 in) vertical drop in the Pacific plate along a 25 mi (40 km) long fault.

The main shock caused some minor damage to the 62-year-old church at the Sissano Mission, and was strong enough that many people in Malol, Arop, and Warapu left their houses because the shaking lasted for so long.

The tsunami wave uprooted entire buildings and transported their foundations 50–60 metres (160–200 ft) from their original location[8] The village of Arop was situated on a narrow spit between the coast and Sissano Lagoon.

Immediately after the tsunami, the Royal Australian Air Force flew in three Lockheed C-130 Hercules transport planes with relief supplies.

[11] The amount of injury and illness due to the tsunami overwhelmed the makeshift hospitals, leaving many victims with wounds that were untreated for several days and led to gangrene.