1,721,191 research outputs found
Use of small earthquake records to determine the source time functions of larger earthquakes: an alternative method and an application
No full textSmall earthquake records are increasingly being used as empirical Green's functions to estimate the source time functions (STFs) of large earthquakes. This is generally accomplished in the frequency domain by computing the ratio of the large to the small event spectrum and then transforming it back to the time domain. This study proposes an alternative method in which a large-event STF is approximated by a series of pseudotriangular pulses whose parameters are determined by a nonlinear frequency-domain inversion, involving the spectrum of the large and the small events. The method allows a "positivity' constraint to be imposed on the STF. The misfit between the observed and computed large-event seismograms is measured in the frequency domain over the range of frequency in which the data are reliable. -from Author
Source characterisation of low frequency events at Stromboli and Vulcano Islands (Isole Eolie Italy)
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Structural model of the Northern Latium volcanic area constrained by MT, gravity and aeromagnetic data.
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The structural setting of the Ischia Island Caldera (Italy): first evidence from seismic and gravity data
No full textIschia Island is one of the active volcanoes of the Neapolitan area (Italy). Hazard assessment of active, densely populated volcano is primarily based on knowledge of the volcano’s past behaviour and of its present state. As a contribution to the definition of the present structural setting of Ischia Island, we constructed a new model of the shallow crust using geophysical data: seismic wave travel times and Bouguer anomaly data. We analysed these data sets through seismic tomography and gravity data inversion. The main results inferable from the 3D seismic and gravity images are the definition of the caldera rim along the perimeter of the island, as hypothesized by many authors, and the presence of a high velocity and density area inside the caldera consistent with extension of the resurgent block that characterizes the recent deformation of the island
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