Представлено членом редакційної колегії д-ром фіз.-мат. наук, проф. Б.П. Масловим) A method is presented for moment tensor inversion of only direct P-waveforms registered at only one station and a limited number of stations. The method is based on an inversion approach described in where a version of the matrix method has been developed for calculation of direct P-waves in horizontally layered half-space from a point source represented by its moment tensor. We describe a procedure for retrieving the source mechanism of small earthquakes based on interactive inversion of seismograms and demonstrate its application to two local earthquakes in the Boise region. The moment tensor inversion of seismogram data in this study is based on a point source model. The process includes generation of synthetic seismograms using the matrix method for an elastic, horizontallylayered, medium. In the paper, a method is presented for moment tensor inversion of only direct P-waves, which are less sensitive to path effects than reflected and converted waves. This approach significantly improves the inversion method accuracy and reliability. A pointsource approximation is considered, with known location and origin time. Based on forward modeling, a numerical technique is developed for the inversion of observed waveforms for time history of the components of moment tensor M(t), obtained by generalized inversion.
Surface and body waves inherently coexist in seismic records. Usually, we are interested in the one, while the other is considered unwanted. To complicate things, body and surface waves often overlap in time and space. Hence, separation of these different wave modes is complicated, and remains an active topic of research. Here we use estimates of the Green tensor obtained via seismic interferometry to provide waveforms with isolated body and surface waves, allowing us to focus our further studies on one or the other. These ideas are illustrated with laboratory and numerical examples.
Surface-wave tomography from the correlations of ambient noise records has provided a powerful tool to investigate the Earth's subsurface with new surface-wave information. Exploration surveys can benefit from inversion of these virtual surface waves, as well. Most commonly, correlations are performed on the vertical components of the wavefields, but here we use the crossterms of multicomponent data and show virtual surface wave recordings are less sensitive to artifacts from signal not in-line with the two stations. We illustrate this with a subsection of the Coronation data set and the Batholiths temporary seismic deployment, showing estimates of the Rayleigh wave and the consequent phase-velocity dispersion curve.
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