Preliminary Tsunami Simulation of M7.5 – 45km NE of Kokopo, Papua New Guinea

We have simulated the tsunami generated from the M 7.5 – 45km NE of Kokopo, Paapua New Guinea (4.081°S 152.569°E, depth=10.0 km, M = 7.5 at 2019-05-14 12:58:26 (UTC) according to USGS. The assumed tsunami sources cover the aftershock area for 2 hours after the mainshock (Fig. 1). The fault size and average slip are 140 km × 15 km and 3.5 m. The focal mechanism is strike=317º, dip=49º, and slip=-26º from the USGS’s W-phase moment tensor solution. The top depth of the fault was assumed to 5 km. The seismic moment is 2.16 x 10²⁰Nm (Mw = 7.5) assuming the rigidity of 5 x 10¹⁰N/m².

Figure 1. Tsunami source model, the red lines indicate uplift with interval of 0.15 m, while the dashed blue contours indicate subsidence with interval of 0.30 m. The epicenter is shown by the blue star. The focal mechanism defined by USGS is also shown.

As the initial condition for tsunami, static deformation of the seafloor is calculated for a rectangular fault model [Okada, 1985] using the source model. The used bathymetry data is the 12 arc-second grid data from GEBCO. To calculate tsunami propagation, the linear shallow-water, or long-wave, equations were numerically solved by using a finite-difference method [Adriano et al., 2018].

Figure 2. Maximum Height of Simulated Tsunami. The epicenter is shown by the red star. The exposed population is from LandScan 2014 Global dataset. The maximum wave height at the coastline is also shown.

Disclaimer
The information contained in the map is for general information purposes only. The accuracy of the analysis is not assessed yet. We endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability concerning the mapping results or the information, products, services, or related graphics contained on it for any purpose. Any reliance you place on such information is therefore strictly at your own risk.

by Bruno Adriano (RIKEN AIP) and Shunichi Koshimura (IRIDeS, Tohoku University)

References
Okada, Y. (1985), Surface Deformation Due to Shear and Tensile Faults in a Half-Space, Bulletin of the Seismological Society of America, 75(4), 1135-1154. (link)

Adriano, B., Fujii, Y., Koshimura, S. et al. (2018), Tsunami Source Inversion Using Tide Gauge and DART Tsunami Waveforms of the 2017 Mw8.2 Mexico Earthquake, Pure and Applied Geophysics, 175, 35-48. doi: 10.1007/s00024-017-1760-2