Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

112 PATA Days 2024 R E S U LT S The geomorphology of the Lae City region relates to the interaction between riverine (and limited marine) deposition and erosion, and range-building over the Wongat South Thrust fault (Figure 1B). A flight of eight uplifted and gently folded fluvial surfaces, and two uplifted and foldedmarine terraces, were mapped using LiDAR digital elevation data (Fig. 2). A clear expression of the fault upon which the uplift occurred was mapped striking in a northwest direction between the Lae CBD and the Port Precinct. Fig. 1: A) The Lae Study area with anticlines developed in Leron and Markham formation sediments above faults of the Ramu- Markham Fault Zone shown (Abbott, Silver, & Galewsky, 1994; Crook, 1989b; Liu, 1993). Uplifted Late Pleistocene Markham Formation sediments adjacent to the southern margins of the folds developed in the Leron formation mark the positions of the most recently active thrusts. Inset shows tectonic setting (after Abers & McCaffrey, 1994). B) Hill-shaded LiDaR digital elevation data with color-drape rotated north to highlight the Busu River fan. It is clear that the Busu River has trimmed the Atzera Range. The scarp is 2.5 – 3.0 m high where it crosses Didiman Creek (Ch2, one deformation event), and up to 6.5 m high where it is developed in bracketing paired terrace surfaces (T2, two deformation events). Further west, the scarp rises to 13.5 m high (four deformation events?), and is associated with a higher set of paired terraces (T3). The Lae CBD is situated on a more elevated abandoned channel (Ch3), also fringed by two higher paired terrace levels. The Lae War Memorial occupies a yet higher terrace remnant (25 m above the lowmarine terrace sea level). Three terrace levels carved into the eastern side of the high ground occupied by the CBD are further testament to the long-lived impediment to drainage presented by the uplifting Atzera Range (and eastern extension below Lae City).