http://hdl.handle.net/2122/269 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/3999 Title: Solar panel simulator <br/> <br/>Authors: Romeo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Urbini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: This is a funny kind of power supply, not stable in voltage or in current: it simulates the comportment of a solar panel and can be very useful if you are playing around a solar powered device in a raining day. We designed it for internal use, but it may have a general value. Mon, 29 Oct 2007 22:58:59 GMT http://hdl.handle.net/2122/3990 Title: Solidification behaviour of natural silicate melts and volcanological implications <br/> <br/>Authors: Iezzi, G.; Universita' Chieti; Mollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia <br/> <br/>Editors: Columbus, F.; Nova Science Publishers <br/> <br/>Abstract: The thermodynamic and physical properties of magmas have been extensively investigated as a function of T, P, fO2 and composition allowing the development of accurate phase stability, viscosity, and diffusion models. However, how the silicate melt properties are influenced by kinetic effects is still an open question. The most important transformation of a magma is its solidification due to cooling, i.e. the transition from a silicate melt to a rock. Solidified magmas may be crystalline, vitreous, or a mixture of glass and crystals. If the cooling rate is larger enough to prevent crystallization, a magma can encompass the supercooling region without crystallisation. The smallest cooling rate that suppresses or strongly limited the nucleation of crystals is the critical cooling rate Rc. Melts with low Rc persist in a metastable liquid state and have a good glass forming ability (GFA). GFA and Rc of melts can be quantitatively estimated using (1) the reduced glass transition parameter Trg = Tg/Tm (Tg, temperature of glass transition; Tm, temperature of melting), and (2) the viscosity fragility concept. As stated by the theory, strong liquids with high Trg values have good GFA and low Rc, whereas fragile liquids with low Trg have a poor GFA and high Rc. Using available experimental data and theoretical models, we analyze the kinetic effects in dry magmas of different composition. The obtained results are relevant for the formation of lava flows and domes. In sub-alkaline magmas, Trg linearly increases and Rc decreases as the Si and Al content increases. Rc of basalts range between 101 and 103 K/s. In dacitic and rhyolitic melts, Rc is between 10-3 and 10-5 K/s. Alkaline melts have Trg values lower than those of sub-alkaline compositions. Results are consistent with the available experimental data. The sluggish kinetics of nucleation determined by using the relation Rc vs Trg is also in agreement with the experimental and theoretical data for synthetic silicate melts. The outlined solidification behaviour of magmatic melts has a profound influence on the viscosity paths of magmas. Depending on the Trg and Rc values, less evolved magmas may have a viscosity larger than that of more evolved magmas due to the rapid crystallization induced by the cooling during their flowing on the Earth. The glassy portion of poorly evolved magmas is indicative of rapid cooling, whereas the glassy fraction of evolved magmas is not unequivocally indicative of rapid cooling being their typical Rc values low. Basaltic lavas may flow on the Earth surface for long times only if they have a temperature close to Tm, whereas more evolved lavas can flow for longer periods with temperatures well below Tm. Fully glassy lavas like obsidians have invariably rhyolitic or trachytic compositions. Mon, 29 Oct 2007 22:58:59 GMT http://hdl.handle.net/2122/3989 Title: Remote sensing of volcanic terrains by terrestrial laser scanner: preliminary reflectance and RGB implications for studying Vesuvius crater (Italy) <br/> <br/>Authors: Pesci, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Teza, G.; Universita' Padova; Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia <br/> <br/>Abstract: This work focuses on the use of terrestrial laser scanner (TLS) in the characterization of volcanic environments. A TLS survey of the Vesuvius crater (Somma-Vesuvius volcano, Italy) allows the construction of an accurate, georeferenced digital model of different sectors of the crater. In each sector, the intensity is computed for each point as the ratio between the emitted amplitude and the received one, normalized to the maximum signal, providing the radiometric information. Moreover, the RGB colours of the observed surfaces can be captured by means of a calibrated camera mounted on the TLS instrument. In this way, multi-band information is given, since a long range TLS operates in the near infrared band. The reflectance and RGB data are compared in order to verify if they are independent enough to be complementary for model analysis and inspection. Results show that the integration of RGB and intensity data can fully characterize this volcanic environment. The collected data are able to discriminate different volcanic deposits and to detect their stratigraphic features. In addition, our results shed light on the spatial extension of landslides and on the dimensions of rock fall/flow deposits affecting the inner walls of the crater. The remotely acquired TLS information from the Vesuvius crater is compared with that from a sedimentary terrain (coal-shale quarry) to detect possible similarities/differences between these two geological environments. Mon, 29 Oct 2007 22:58:59 GMT http://hdl.handle.net/2122/3987 Title: Seismic activity in the transition zone between Southern and Central Apennines (Italy): Evidences of longitudinal extension inside the Ortona–Roccamonfina tectonic line <br/> <br/>Authors: Milano, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Di Giovambattista, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia <br/> <br/>Abstract: We analyze the 1997–2006 seismicity of the transition zone between Southern and Central Apennines, which is one of the most active seismic areas of Italy. Our aim is to add information on the seismotectonic picture of this area. Seismic activity is characterized by single events with Mb3.0 and low magnitude (Mb4.0) seismic sequences (1997–98 and 2005) and swarms (1999, 2000 and 2001). Hypocenters are within the upper 15 km of the crust. The epicentral distribution of the relocated seismicity shows that single events prevalently align NW–SE along the Apennine chain axis. This seismicity is related to the main, NE–SW extension affecting the chain. Single events concentrate also: at the south of the seismogenetic source responsible for the 1915 earthquake, where the 2000 swarm occurred; between the faults of the 1984 and 1805 events, where the 2001 sequence developed; between the faults of the 1805 and 1688 events, where the 1997–1998 seismic sequence concentrated. The seismic swarms occurred in 1999, 2000 and 2005 are located inside the Ortona– Roccamonfina structural line, which strikes NNE–SSW and separates the Central Apennines from the Southern ones. The epicentral distribution of these swarms and focal mechanisms suggest the presence of active NE–SW faults moving in response to a NW–SE extension. The results of the strain analysis on 52 wellconstrained focal mechanisms evidence a prevailing NE–SW extension, corresponding to the large scale stress field acting in the Apennine Chain, and a second-order NW–SE extension. This last direction of extension was already observed in the 1997–98 and 2001 seismic sequences. The location of the NE–SW striking faults responsible for the seismic swarms suggest that some segments of the Ortona–Roccamonfina line are still active and move in response to both the NE–SW regional extension of Southern Apennines, and to a NW–SE striking longitudinal extension. Mon, 29 Oct 2007 22:58:59 GMT