Field Survey and Preliminary Modeling of the Wewak, Papua New Guinea Earthquake and Tsunami of 9 September 2002

Abstract

At 18:44 UTC on 8 September 2002 (04:44 on 9 September, local time), a strong earthquake ( mb 6.5 , MS 7.8; hereafter “PNG02”) occurred off the northern coast of the East Sepik Province of Papua New Guinea (“PNG”; see Figure 1) and triggered a moderate tsunami that was observed along 300 km of the northern PNG coast. This event is of particular interest since it occurred only 120 km east-southeast of the earthquake of 17 July 1998 ( mb 5.9, MS 7.0; hereafter “PNG98”), which triggered a devastating tsunami with a death toll exceeding 2,100 (Kawata et al ., 1999). The two earthquakes generated very different patterns of damage and destruction. PNG02 was strongly felt from Sissano Lagoon in the west to Murik Lakes in the east, a distance of 250 km (Figure 2); five people were killed, and several more injured, by the collapse of structures. On the other hand, its tsunami inundated several coastal villages but caused only a small amount of damage to beachfront structures. No one was killed by the tsunami, although four people nearly drowned. By contrast, PNG98 caused very little earthquake damage, mostly concentrated in the epicentral area near the Serai sawmill, where a few log stacks collapsed and rockslides were observed along strongly weathered cliffs. No one was killed by the earthquake. However, the tsunami triggered by PNG98 was exceptionally devastating, with waves reaching heights of 15 m, destroying three villages and severely damaging many others along a 40-km stretch of coast. Over the past 100 years, only the 1933 Sanriku, Japan tsunami had a higher death toll (estimated at 3,000). Successful modeling of the 1998 tsunami could be achieved only by hypothesizing that the earthquake triggered a 4 km3 landslide, an assumption corroborated by a number of …