When the Cultural Heritage cannot be physically visited

il contributo esplora possibili soluzioni di turismo virtuale per accedere al patrimonio culturale che non può essere fisicamente visitato, con particolare attenzione all'immersività e al coinvolgimento fisico del visitatore. Viene presentato un progetto interdisciplinare elaborato nel corso di una recente collaborazione internazional

Further structural constraints and uncertainties of a thin laterally varying ultralow-velocity layer at the base of the mantle

Constraints and uncertainties are presented for modeling of an ultralow-velocity zone layer (ULVZ) at the base of Earth's mantle using an SKS wave with small segments of P wave diffraction at the SKS core entry and exit locations, called SP_dKS. Source or receiver effects are ruled out as causes for the SP_dKS anomalies used to map ULVZ structure, since systematic SP_dKS-SKS travel time moveout behavior is present in profiles of recordings of a given earthquake at many seismographic stations and also for many events recorded at one station. The southwest Pacific region produces strong variability in observed SP_dKS/SKS amplitude ratios (compared to synthetic seismograms), which geographically corresponds to an anomalous ULVZ region. Accurate determination of absolute ULVZ thicknesses requires knowledge of, in addition to magnitude of P wave velocity (V_p) reduction in the layer, the magnitude of S wave velocity (V_S) reduction and density (ρ) perturbation (if any). Synthetic seismogram experiments demonstrate several key points regarding uncertainties and constraints in modeling ULVZ structure: (1) thicker layers (up to 300 km thick) with mild reductions (e.g., −2.5 to −5.0%) cannot reproduce the anomalous SP_dKS behavior seen in the data; (2) for ULVZ layers less than 10 km thick, strong trade-offs exist between discontinuous velocity reductions and linear gradient reductions over a thicker zone; (3) uncertainties preclude precise determination of magnitude of δV_P and δV_S reductions, as well as the δV_S:δV_P ratio; (4) large density increases within the ULVZ (e.g., up to 60% and more) can efficiently broaden and delay the peak of the energy that we identify as SP_dKS for models with strong velocity reductions in the layer; (5) models with extreme Q reductions in the ULVZ can affect SP_dKS waveforms, and dampen spurious ringing energy present in Sd waveshapes due to the ULVZ; and (6) the minimum required V_p reduction for the most anomalous data (around −10%) trades off with thinner ULVZ structures containing larger velocity reductions (with possible density increases as well)

Seismic detection of a thin laterally varying boundary layer at the base of the mantle beneath the central-Pacific

We explore lowermost mantle structure beneath the Pacific with long‐period recordings of the seismic core phases SKS, SP_dKS, and SKKS from 25 deep earthquakes. SP_dKS and SKKS are anomalously delayed relative to SKS for lower mantle paths beneath the southwest Pacific. Late SP_dKS arrivals are explained by a laterally varying mantle‐side boundary layer at the CMB, having P‐velocity reductions of up to 10% and thickness up to 40 km. This layer is detected beneath a tomographically resolved large‐scale low velocity feature in the lower mantle beneath the central‐Pacific. SKS, SP_dKS, and SKKS data for the generally faster‐than‐average circum‐Pacific lower mantle are well‐fit by models lacking any such low‐velocity boundary layer. The slow boundary layer beneath the central Pacific may be a localized zone of partial melt, or perhaps a chemically distinct layer, with its location linked to overlying upwelling motions

Modeling two-dimensional structure at the core-mantle boundary

Recent studies of SKS waveform modeling emphasize the strong variation of seismic properties at the core-mantle boundary (CMB) and the need for two-dimensional and three-dimensional waveform modeling capabilities. In particular, the bifurcation of SKS into SP _dKS and SKP _dS near 110° shows strong regional variations. The first of these phases has a P wave diffraction along the bottom of the mantle near the source, while the latter phase occurs at the receiver end. Generalized ray theory proves effective in generating theoretical seismograms in this type of problem because each of these diffractions is associated with a particular transmission coefficient: T_(sp) which transmits shear waves into primary waves when crossing the CMB and T_(sp) which transmits the primary waves back into shear waves at the receiver end. Each region can then be isolated and have its separate fine structure, sharp or gradational. Two classes of boundaries are explored: the CMB as a simple, sharp interface and the CMB with a very low velocity transition layer (10% slower than reference models). The two diffractions produced by these structures have diagnostic arrival times and wave shapes and when combined with the geometric SKS produce distinct waveform characteristics not easily generated by other means. Since the ray paths associated with these three phases are virtually identical in the mantle and only differ along a short sample of CMB and in the one-dimensional fluid core, we can isolate the small localized CMB region sampled. Thus the waveform character of the extended SKS in the range of 105° to 120° becomes an excellent CMB probe which we demonstrate on a small sample of observations from the Fiji-Tonga region as recorded in North America

Preliminary observations from the use of US-Soviet Joint Seismic Program data to model upper mantle triplications beneath Asia

New short-period waveform data from the US-Soviet Joint Seismic Program (JSP) make possible investigations of Asian upper mantle structure. the goal of this paper is to explore the potential use of the newly available JSP data to gain a qualitative view of upper mantle structure beneath Asia, and to facilitate more detailed future detailed future upper mantle studies. In a reconnaissance approach, waveform upper mantle studies. In a reconnaissance approach, waveform predictions from upper mantle P-wave velocity models of previous studies are compared to the JSP data to investigate regional differences in the central Asian upper mantle. Data coverage brackets the upper mantle triplications with excellent multi-source-to-stations sections. the abundance of data for controlled source-receiver geometries and the impulsive nature of the arrivals enable us to stack seismograms to improve signal-to-noise ratio. Arrivals from the 400 and 670 km discontinuities are apparent in the data and are compared to predictions of the mantle models. the principal result is that, for the regions studied, paths through cratonic regions of Asia are compatible with shield-type models, while paths through highly deformed regions of Asia are compatible with models derived for tectonically active regions, suggesting large lateral variations beneath the Eurasian continent. Use of the JSP data in a comparative approach is fast and simple, and proves effective in obtaining a first-order understanding of the Asian upper mantle. This result also presents the potential for qualitative studies elsewhere with digital portable stations

The New Version of the Model MZE, Macroeconometric Model for the Eurozone

This paper presents the main improvements carried out to the macroeconometric model MZE since its creation in 2003. We have back-calculated the series over the period 1980-1995, in order to make the model more stable. To our knowledge, this paper is the first application of Kllians (1998) method to estimate coefficients and centered confidence intervals for an operational macroeconometric model. The new coefficients enable to get less inflationary responses to macroeconomic shocks than the previous version of MZE. The study is more nuanced and rigorous thanks to the confidence intervals around the main scenarios. It is thus possible to check the significance of the results at any horizon. At last, the new version of MZE enables to find conventional responses to international shocks, like the inflationary effect of a rise in oil prices or the delayed impact of a depreciation of the euro on the improvement of the trade balance.Macroeconometric modelling, Forecasting, Confidence interval, Bootstrap

Nuovi scenari di turismo virtuale con gli UAV

Un nuovo tipo di fruizione culturale dei beni architettonici e dei beni artistici che potrebbe risolvere molti problemi relativi all'accessibilità del patrimonio culturale. Applicazioni di turismo virtuale di terza generazione

Time Domain Regional Discriminants

The time and frequency domains are equivalent displays of seismic trace, information, though some qualities of the signal are more easily observed in one domain than the other. The relative frequency excitation of Lg, for instance, is most easily viewed in the frequency domain, but such waveform qualities as the sequence in which pulses arrive in the wave train or the sharpness of pulse onset are most easily studied in the time domain (Murphy and Bennett, 1982, Blandford, 1981). Because of the tremendous complexity of high frequency regional data, most attempts at using it for discrimination purposes have involved analysis of the frequency content of the various arrivals either through transforming selected windows or through multiple bandpass filtering. We report here on our initial attempts to explore the alternative and to discriminate events using those waveform characteristics most easily observed in the time domain. A second advantage of time domain analysis approaches is that they permit a deeper insight into the physical processes creating a seismic signal's character. For this reason, they can be more e3silv used to evaluate the transportabilty of a discriminant to varying geophysical and tectonic regimes. This is an especially important feature in the development of regional discriminants. The most prominent and successful spectral regional discriminants have been empirically developed. This means that they must be redeveloped and reverified in each new area. As we shall show in the following, through rigorous time domain analysis such features as regional depth phases can be identified and used to discriminate. Discriminants based on such simple physical features as source depth should be transportable anywhere. In work recently completed under the treaty verification program, we have proved that such time domain discriminants do exist. In analyzing a test discrimination data set from the western U. S., we have discovered that the onset of P_n is always very similar for explosions and that few earthquakes have this unique waveform character. This information can be constructed into a simple discrimination scheme by testing the correlation of observed P_n waveform onsets with average waveforms observed from explosions. High correlations indicate explosions and low correlations earthquakes. We have also discovered that the regional phase P_g is actually composed of a sequence of sub-arrivals which correspond to successively higher orders of reverberation in the crust. In realistic crust models, the depth phases play an important role in the waveshapes of these sub-arrivals. By selecting an appropriate frequency band to analyze, we have been able to accurately model this type of data from explosions in the western United States. Over the very relevant regional distance ranges of 200 to 600 km, it appears that a discrimination procedure very similar to the one which is known to work for P_n will also be effective for P_g. We are investigating whether similar discriminants can be constructed based on the phases S_n and S_g in areas where those phases are prominent arrivals

Time Domain Regional Discriminants

The time and frequency domains are equivalent displays of seismic trace, information, though some qualities of the signal are more easily observed in one domain than the other. The relative frequency excitation of Lg, for instance, is most easily viewed in the frequency domain, but such waveform qualities as the sequence in which pulses arrive in the wave train or the sharpness of pulse onset are most easily studied in the time domain (Murphy and Bennett, 1982, Blandford, 1981). Because of the tremendous complexity of high frequency regional data, most attempts at using it for discrimination purposes have involved analysis of the frequency content of the various arrivals either through transforming selected windows or through multiple bandpass filtering. We report here on our initial attempts to explore the alternative and to discriminate events using those waveform characteristics most easily observed in the time domain. A second advantage of time domain analysis approaches is that they permit a deeper insight into the physical processes creating a seismic signal's character. For this reason, they can be more e3silv used to evaluate the transportabilty of a discriminant to varying geophysical and tectonic regimes. This is an especially important feature in the development of regional discriminants. The most prominent and successful spectral regional discriminants have been empirically developed. This means that they must be redeveloped and reverified in each new area. As we shall show in the following, through rigorous time domain analysis such features as regional depth phases can be identified and used to discriminate. Discriminants based on such simple physical features as source depth should be transportable anywhere. In work recently completed under the treaty verification program, we have proved that such time domain discriminants do exist. In analyzing a test discrimination data set from the western U. S., we have discovered that the onset of P_n is always very similar for explosions and that few earthquakes have this unique waveform character. This information can be constructed into a simple discrimination scheme by testing the correlation of observed P_n waveform onsets with average waveforms observed from explosions. High correlations indicate explosions and low correlations earthquakes. We have also discovered that the regional phase P_g is actually composed of a sequence of sub-arrivals which correspond to successively higher orders of reverberation in the crust. In realistic crust models, the depth phases play an important role in the waveshapes of these sub-arrivals. By selecting an appropriate frequency band to analyze, we have been able to accurately model this type of data from explosions in the western United States. Over the very relevant regional distance ranges of 200 to 600 km, it appears that a discrimination procedure very similar to the one which is known to work for P_n will also be effective for P_g. We are investigating whether similar discriminants can be constructed based on the phases S_n and S_g in areas where those phases are prominent arrivals