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

G E O L O G I C A L S E T T I N G Lae City is located at the site of a modern arc- continent collisionbetween theWest Bismarck volcanic arc (SouthBismarck Plate) and the Australian continental margin, along the Ramu- Markham Fault Zone (RMFZ; Abbott, Silver, & Galewsky, 1994; Holm et al., 2016; Fig. 1 - inset). Fluvial, lacustrine, and marginal-marine deposits (Leron Formation) accumulated in a terrane foreland basin (Markham Basin) that developed south of the collision zone during the Pleistocene (Abbott, Silver, Thompson, et al., 1994). Further propagation of the thrust front toward the foreland incorporated the Leron Formation into the fold-and-thrust belt. Rapid uplift and voluminous volcano-lithic sedimentation (Markham Formation) continues to the present (Liu, 1993), responding to a contemporary convergence rate of 50 mm/yr (Stanaway et al., 2009). Understanding deformation within the Leron and Markham formations is key to evaluating the contemporary earthquake hazard. A frontal Markham basin-wide (hanging-wall) anticline is associated with the frontal thrust of the RMFZ (Crook, 1989b; Liu, 1993). Twenty kilometres northwest of Lae, the basin-wide anticline splays with one arm trending in an easterly direction and the other to the southeast (Fig. 1). The southeast splay of the anticline is expressed topographically as the Atzera Range. In the Lae urban area, alluvium belonging to the Leron and Markham formations is uplifted across the Aztera Range anticline axis (Buleka et al., 1999). The underlying fault continues offshore at the MarkhamRiver mouth, to join the MarkhamTrench (Abbott, Silver, & Galewsky, 1994). The RMFZ in the Markham Trench, offshore of Lae, has also been called the Wongat Thrust South (Abbott, Silver, &Galewsky, 1994; Koulali et al., 2015), and we apply this terminology to the southern splay running through Lae City.