2023 East Sepik earthquake
# 2023 East Sepik earthquake

A magnitude 7.1 earthquake struck 38.3 km (23.8 mi) east-southeast of Ambunti in East Sepik Province, Papua New Guinea on 3 April 2023.

## Tectonic setting

The island of New Guinea lies within the complex zone of collision between the Australian and Pacific Plates. 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 overall shortening is focused into two zones of thrust faulting, the Ramu–Markham fault zone, which forms the southwestern boundary of the Huon–Finisterre terrane, and the Highlands Thrust Belt, which lies further southwest and deforms the Australian margin. The hanging wall of the Ramu–Markham thrust system is broken up by multiple strike-slip faults. The orientation of these faults, parallel to the direction of thrusting, suggests that they accommodate distortion of the Huon–Finisterre block. Most of the seismicity in northern Papua New Guinea is associated with the Ramu–Markham fault system, with a smaller number of earthquakes occurring on the strike-slip faults and on the Highlands Thrust Belt.

## Earthquake

The earthquake had a focal mechanism corresponding to a dip-slip fault. The United States Geological Survey reported that the earthquake's magnitude was $M_{ww}$ 7.0 or $M_i$ 7.3, while GEOSCOPE reported the earthquake as $M_w$ 7.2 at a depth of 39 km (24 mi), while the GCMT reported the event as $M_w$ 7.1. According to PAGER, the earthquake caused damaging shaking of intensities V-VII (Moderate-Very Strong) in the towns of Ambunti, Angoram, Wewak, Aitape, Porgera and Wabag, combining to a total population of about 1.12 million residents. Mild tremors of the earthquake were also felt in neighboring Indonesia, mainly in the cities of Jayapura and Nabire.

## Damage and casualties

All six districts of East Sepik Province were affected. Over 300 homes collapsed in the earthquake, including seven in Ambunti alone, and damage occurred in 23 villages around the epicenter. There were at least seven deaths and seventeen injuries, including two fatalities due to a house collapse in Angoram and another death in Wewak. In the village of Korogu, three houses collapsed and many were injured. Landslides were also reported in the affected areas, and deep fissures were reported in Chambri Lake, where the epicenter was located.

