Takuto Maeda , Kiwamu Nishida, Ryota Takagi and Kazushige Obara<\/p>\n
Progress in Earth and Planetary Science, DOI:10.1186\/s40645-016-0107-4, 2016<\/p>\n
Abstract<\/strong>
\nWe reconstructed a 2D seismic wavefield and obtained its propagation properties by using the seismic gradiometry\u00a0method together with dense observations of the Hi-net seismograph network in Japan. The seismic gradiometry\u00a0method estimates the wave amplitude and its spatial derivative coefficients at any location from a discrete station\u00a0record by using a Taylor series approximation. From the spatial derivatives in horizontal directions, the properties of\u00a0a propagating wave packet, including the arrival direction, slowness, geometrical spreading, and radiation pattern\u00a0can be obtained. In addition, by using spatial derivatives together with free-surface boundary conditions, the 2D\u00a0vector elastic wavefield can be decomposed into divergence and rotation components. First, as a feasibility test, we\u00a0performed an analysis with a synthetic seismogram dataset computed by a numerical simulation for a realistic 3D\u00a0medium and the actual Hi-net station layout. We confirmed that the wave amplitude and its spatial derivatives were\u00a0very well-reproduced for period bands longer than 25 s. Applications to a real large earthquake showed that the\u00a0amplitude and phase of the wavefield were well reconstructed, along with slowness vector. The slowness of the\u00a0reconstructed wavefield showed a clear contrast between body and surface waves and regional non-great-circle-path\u00a0wave propagation, possibly owing to scattering. Slowness vectors together with divergence and rotation decomposition\u00a0are expected to be useful for determining constituents of observed wavefields in inhomogeneous media.<\/p>\n