Estimated Seismic Source Parameters for 2019 Magnitude 7.6 Papua New Guinea Earthquake

Abstract

On 14 May 2019, a major (Mw 7.6) earthquake struck eastern Papua New Guinea, causing a tsunami warning that was later canceled. The last major rupture in the region was a 2000 Mw 8.0 event, which resulted in massive horizontal land movements of up to several meters and a series of aftershocks with primarily thrust mechanisms, and caused a damaging tsunami. Seismic methods for characterizing the source process were applied. Vertical components of the long-period P-waves from 35 stations of the Global Seismic Network with even azimuthal coverage were adopted in the inversions. First, the focal mechanism solution was retrieved after the earthquake. From the inverted results as well as aftershock distribution, the causative fault of the great PNG earthquake was confirmed to be a fault of strike = 316°, dip = 84°, and rake = 0°, indicating that the earthquake was a left-lateral strike-slip event. Then, to clearly understand the spatiotemporal evolutionary process of the source rupture of the earthquake, far-field body wave data were collected, and the source rupture process of this earthquake was studied using the finite fault inversion method. A finite-fault model was estabished with length and width of 152 and 32 km, respectively, and we set the initial seismic source parameters referring to the center of the focal mechanism solution. This was estimated by the focal mechanism solutions of defferent studies referring to different focal mechanism solutions. We found that the focal mechanism solution determined by Global Centroid Moment Tensor Catalog was not appropriate. Inversion results indicated that the seismic moment was 3.63 × 1020 Nm (Mw 7.6), and the source duration was ~ 40 s. The rupture propagated mainly toward the northwest in an asymmetrical bilateral mode, with a maximum slip of ~ 13.2 m, and a large-scale slip patch strongly ruptured to the surface. The study of Coulomb stress changes suggested that the PNG earthquake may trigger a thrust-type rupture in the New Britain Trench, which has the potential to trigger a tsunami.