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Effects of dopamine infusion on forearm blood flow in critical patients.
Full text linkPiazza O, Zito G, Valente A, Tufano R.
Effects of dopamine infusion on forearm blood flow in critical patients.
Med Sci Monit. 2006 Feb;12(2):CR90-3. Epub 2006 Jan 26
Source, attenuation and site parameters of the 1997 Umbria-Marche seismic sequence from the inversion of P wave spectra: a comparison between constant Q and frequency dependent Q models
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Interaction between shallow and subcrustal dislocations on a normal fault
No full textWe propose a model which may explain seismic sequences which are often observed in seismogenic regions, as for example in the Apenninic chain (Italy). In particular, we consider a normal fault and earthquakes taking place at different depths: a first shock in a shallower layer and a second in a deeper one. The normal fault is embedded in a viscoelastic half-space. As a consequence of the rheology, there are two different brittle layers, a shallower and a deeper one, where earthquakes can nucleate. Between these two layers, the rheological behavior is ductile. The thicknesses of the layers depend on the geothermal profile that is calculated taking into account the profile of the thermal and rheological parameters with depth. The fault plane, crossing layers with different rheological behavior, is heterogeneous in respect to the slip style: seismic in the brittle layers, aseismic in the ductile layer. Dislocations in the shallower layer are assumed to produce aseismic slip in the area of the fault belonging to the ductile layer. The stress concentrated, by the seismic and aseismic dislocations, on the fault plane section in the deeper brittle layer is evaluated. It is compared with the tectonic stress rate in order to calculate how much earlier the second earthquake would occur compared to if just the bare tectonic sstress was acting. It results that such an advance is comparable with typical recurrence times of earthquakes and so a mechanism of interaction between different seismic sources, mediated by aseismic slip, can be supposed. The strains and displacements at the Earth's surface due to seismic and aseismic slip are calculated. They are large enough to be detected by present geodetic techniques
Source, attenuation, and site parameters of the 1997 Umbria-Marche seismic sequence from the inversion of P wave spectra: A comparison between constant Q(P) and frequency-dependent Q(P) models RID C-3422-2011 RID B-5344-2010
No full textThe attenuation of P waves, the site responses, and the source parameters (seismic moment, corner frequency, source dimension) of 490 seismic events that occurred during the 1997 Colfiorito, Umbria-Marche seismic sequence have been inferred from the inversion of P wave velocity spectra. The Boatwright source model has been assumed to model the source spectra. A global nonlinear inversion scheme was developed to avoid any a priori selection of the initial Q(P) and the corner frequency. To establish if a frequency-dependent Q(P) model fits the data better than a constant Q(P) model, two inversion results have been compared. Application of the Akaike information criterion indicates that the constant Q(P) model represents the best compromise between model simplicity and data misfit. The station Q(P) values are small: in the range of 50 to 200. A one-dimensional Q(P) model is obtained by back projecting the inverted t*. Our results indicate both well-defined near-site attenuation effects at some sites and heterogeneity in the inelastic properties of the crust. With the exception of the amplification response at five seismic stations, most of the recording sites did not show amplification peaks at particular frequencies. The stress drop clearly increases as a function of the seismic moment, which indicates a deviation from self-similarity, whereas it does not show an increase with depth, probably owing to the effects of fluid pressurization in the crust. A stress drop of about 39 MPa is inferred. The relationship between the seismic moment and the local magnitude for P waves has been calibrated
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