Geology, Seismotectonics and Surface Deformation of the 25 February 2018 (UTC) M7.5 Earthquake (EQ) in the Papua New Guinea (PNG) Highlands

Session: Cryptic Faults: Assessing Seismic Hazard on Slow Slipping, Blind or Distributed Fault Systems [Poster]
Type: Poster
Date: 4/28/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The 2018 Mw 7.5 EQ struck the remote PNG Highlands and was centered directly under the Highlands portion of the PNG Liquefied Natural Gas (PNG LNG) pipeline. The PNG LNG project is a joint venture between ExxonMobil, Oil Search Limited, Kumul Petroleum, Santos, JX Nippon Oil and Gas Exploration and Mineral Resources Development Company. ExxonMobil Papua New Guinea Ltd. is the operator and began production in 2014. The EQ and its ~300 aftershocks (five Mw 6.0 to 6.7) caused widespread community impact, landsliding and damage over 1000s of km². However, the pipeline did not lose containment or pressure. Following inspections and repairs to the gas conditioning plant, production was restored in within seven weeks of the EQ.

The 150-km long Highlands portion of the PNG LNG pipeline route crosses a Quaternary fold and thrust (F&T) belt. Geohazards of the route were assessed from an initial 2005 investigation through the 2013 construction. Field recon and LiDAR interpretation identified five Holocene reverse faults crossing the route. Field data informed the input parameters used for fault specific crossing designs. The EQ provided a unique opportunity to assess how the routing, design and construction of the pipeline in the rugged terrain performed with respect to earthquake-induced geohazards and strong ground motions. Ground observations by operating personnel, comparison of post-construction/pre-EQ and post-EQ LiDAR and published INSAR data were used to assess whether primary fault rupture occurred along the route, areas of other ground failures and regional tectonic uplift. The recorded seismicity data compiled by the USGS and their subsequent finite fault analysis were evaluated in conjunction with geologic maps and cross-sections to infer the likely EQ source fault as the basal thrust underlying the F&T belt. While the characteristics of this event were captured within the seismic hazard model used to guide the design, they sampled the margin of the parameter distributions. The pre and post-EQ data were used to inform an updated PSHA model to guide future developments.

Presenting Author: Mark P. Molinari

Authors