Source model of the 2018 MW7.5 Papua New Guinea earthquake constrained by InSAR measurements: Insight into a blind rupture beneath the New Guinea Highlands

Abstract

The Southern Highland Fold and Thrust Belt (SHFTB), the boundary of the Australian plate and the New Guinea Highland block, significantly contributes to the convergent deformation along the plate boundary. However, due to the lack of observation data, the detailed slip pattern of the SHFTB and the orogenic mechanism beneath the New Guinea Highlands remains controversial. On 25 February 2018, the MW7.5 Papua New Guinea (PNG) earthquake struck the southeastern segment of the SHFTB. The detailed rupture characteristics of this event is significant for further clarifying the inter-seismic slip pattern along the SHFTB. Here, the coseismic deformation field of this earthquake was obtained using high-resolution ALOS-2 satellite images. We find that the 2018 MW7.5 PNG earthquake ruptured a large-scaled fault (SHFTB) extending to the lower crust (deeper than 20 km) beneath the New Guinea Highlands, with a dip angle of 24°. The slips on the fault plane are equivalent to moment magnitudes of MW7.51. Three major asperities with thrust-dominated slip of up to 3.94 m are detected on the fault plane. This finding implies that the slip pattern on the eastern segment of the SHFTB is dominated by thrust, rather than with significant sinistral movement, as previously reported. The tectonic deformation across the New Guinea Highlands is possibly concentrated on the large-scale fault SHFTB and primarily controls the intra-continental orogeny in the central Papua New Guinea.

Keywords

• 2018 MW7.5 Papua New Guinea earthquake
• The Southern Highlands Fold-and-Thrust Belt
• InSAR
• Slip distribution
• Seismic risk