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Bearing in mind the destructive potential of tsunamis induced by volcanic landslides, the tsunamigenic event occurring at Stromboli volcano in Italy on 30 December 2002 has been re-examined here, by means of visible images and slope stability analysis. This was one of the few examples in the world of a flank collapse occurring at a volcano that was directly observed. We present the results of stability analyses, together with a sequence of photos collected from a helicopter a few minutes before the collapse. The result of this study is that the sequence of landslides triggering the 2002 Stromboli tsunami can be defined as the final stage of a lateral magma intrusion that exerted a high thrust at high altitude, destabilizing the entire slope. This study allows a more complete understanding of the event that took place on Stromboli on 30 December 2002. Furthermore, the approach used here, if appropriately modified, can be used in other contexts, contributing to the understanding of the condition that leads to tsunamigenic landslides.

Author(s): Capolino, F; Bussotti, P; Borselli, L; Albani, M; Maci, S | Abstract: The problem of edge diffraction close to a point caustic is analyzed in a typical dual-reflector Gregorian antenna in offset configuration. The diffraction phenomenon is produced by a perfectly conducting fin located between the feeder and the main reflector. This fin is sometimes used to reduce the coupling between the primary feed and the main reflector. For the sake of simplicity, the two-dimensional case is studied here, but the present technique can also be applied to practical three-dimensional configurations. © 1997 John Wiley a Sons, Inc.

A uniform high-frequency solution is presented for the diffraction of a horizontal electric dipole located upon a truncated, semi-infinite grounded dielectric slab. This solution is achieved by an asymptotic evaluation of a diffraction Sommerfeld-type integral, which is derived by using a physical optics formulation. The final uniform result is given in terms of a geometrical optics contribution and ray-diffracted contributions from space waves, surface waves, and leaky waves. Although this asymptotic expression is derived by assuming a large distance between the source and the edge, comparisons with a numerical integration have shown very good accuracy also for a distance about 0.2 wavelength. This solution provides physical insight into the diffraction phenomenon and an effective tool for predicting the effects of finite substrates in patch antennas. Indeed, within the expected limitations of the PO approximation, the present formulation is applicable to most of the substrate thicknesses and dielectric constants of practical interest in patch antennas.

In Italy, rainfall-induced slope failures occur every year, claiming lives and causing severe economic damage. We have designed and implemented a landslide warning system, named SANF (an acronym for national early warning system for rainfall-induced landslides), to forecast the possible occurrence of rainfall-induced landslides in Italy. The system is based on: (i) rainfall thresholds for pos- sible landslide occurrence, (ii) sub-hourly rainfall measurements obtained by a national network of 1950 rain gauges, and (iii) quantitative rainfall forecasts. Twice a day, the system compares the measured and the forecasted rainfall amounts against pre-defined ID thresholds, and assigns to each rain gauge a prob- ability of landslide occurrence. This information is used to prepare synoptic-scale maps showing where rainfall-induced landslides are expected in the next 24 hours.

A new configuration of patch antenna is introduced, which provides a dual-band operation. This structure consists of an S-band cross patch with four square patches printed in the empty spaces among the arms of the cross. These patches provide a subarray working at X-band. This structure is simple to design and offers the advantage that it can be printed on a single-layer. An array geometry designed by using the above structure, is suggested. This can be suitable for satisfying the requirements of a typical dual-frequency SAR antenna.

An efficient method is presented for prediction of the input impedance of integrated elliptical lens antennas, excited by a focal radiator which consists of either a resonant slot or a slot-coupled patch. Simple equivalent networks are derived from this method which accounts for effects of multiple reflections inside the lens, which is useful for CAD purposes. Numerical results are presented to validate the equivalent networks. Furthermore, it is shown that these internal reflections significantly affect the input impedance of the primary source.