ABSTRACT

Two earthquakes, Mw 8.1 in 2007 and Mw 7.1 in 2010, hit the western province of the Solomon Islands and caused extensive damage, which motivated us to establish a temporary seismic network around the rupture zones of these earthquakes. With the available continuous seismic data recorded from eight seismic stations, we cross correlate the vertical component of ambient‐noise records and calculate Rayleigh‐wave group velocity dispersion curves for interstation pairs. A genetic algorithm is adopted to fit the averaged dispersion curve and invert a 1D crustal velocity model, which constitutes two layers (upper and lower crust) and a half‐space (uppermost mantle). The resulting thickness values for the upper and lower crust are 6.9 and 13.5 km, respectively. The shear‐wave velocities (VS) of the upper crust, lower crust, and uppermost mantle are 2.62, 3.54, and 4.10  km/s with VP/VS ratios of 1.745, 1.749, and 1.766, respectively. The differences between the predicted and observed travel times show that our 1D model (WSOLOCrust) has average 0.85‐ and 0.16‐s improvements in travel‐time residuals compared with the global iasp91 and local CRUST 1.0 models, respectively. This layered crustal velocity model for the western Solomon Islands can be further used as a referenced velocity model to locate earthquake and tremor sources as well as to perform 3D seismic tomography in this region.

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