Modelling of the hydro-acoustic signal as a Tsunami Precursor

In the frame of a 2-D compressible tsunami generation model with flat porous seabed, we show that acoustic waves are generated and travel outside the source area at sound speed. These waves carry information as to sea floor motion. The acoustic wave period depends on water height at the source area and is given by four times the travel time the sound takes to reach the sea surface from the sea bottom. The fundamental frequency ranges from 1 to 0.05 Hz, at 400 m and 8000 m water depth, respectively. The sound waves produced by seafloor motion can propagate far from the source, with a small attenuation in amplitude. Moreover, the typical wavelengths of the acoustic waves produced by the water layer oscillation allows the waves to overcome most of the seafloor reliefs. The semi-analytical solution of the 2-D compressible water layer model overlying a porous seabed is presente

A new real time tsunami detection algorithm for bottom pressure measurements in open ocean: characterization and benchmarks

In the last decades the use of the Bottom Pressure Recorder (BPR) in a deep ocean environment for tsunami detection has had a relevant development. A key role for an early warning system based on BPRs is played by the tsunami detection algorithms running in real time on the BPR itself or at installation site. We present a new algorithm for tsunami detection that is based on real time pressure data analysis, consisting in tide removing, spike removing, low pass filtering and linear prediction: the output is then matched against a given pressure threshold allowing the detection of anomalous events. Different configurations of the algorithm, consisting for instance in a real time band pass filtering of the pressure signal in place of linear prediction, are also tested for comparison. The algorithm is designed to be used in an autonomous early warning system, with a finite set of input parameters that can be reconfigured in real time. A realistic benchmark scheme is developed in order to characterize the algorithm features with particular regards to false alarm probability, sensitivity to the amplitude and wavelength of the tsunami and detection earliness. The algorithm behaviour in real operation is numerically estimated performing statistical simulations where a large number of synthetic tsunami waves with various amplitude, period, shape and phase is generated and superimposed to time series of real pressure data recorded in different environmental conditions and locations

Modelling of the hydro-acoustic signal and tsunami wave generated by sea floor motion including a porous seabed

Within the framework of a 2-D compressible tsunami generation model with a flat porous seabed, acoustic waves are generated and travel outwards from the source area. The effects of the porous seabed during tsunami generation and propagation processes include wave amplitude attenuation and low pass filtering of both the hydro-acoustic signal and tsunami wave. The period of the acoustic wave generated by the seafloor motion depends on water depth over the source area and is given by four times the period of time required for sound to travel from the sea bed to the surface: these waves carry information about seafloor motion. The semi-analytical solution of the 2-D compressible water layer model overlying a porous seabed is presented and discussed. Furthermore, to include the effects generated by the coupling between compressible porous sedimentary and water layers, a simplified two layer model with the sediment modelled as a compressible viscous fluid is presented

The cone of curves of Fano varieties of coindex four

We classify the cones of curves of Fano varieties of dimension greater or equal than five and (pseudo)index dim X -3, describing the number and type of their extremal rays.Comment: 27 pages; changed the numbering of Theorems, Definitions, Propositions, etc. in accordance with the published version to avoid incorrect reference

New study of the 1755 earthquake source based on multi-channel seismic survey data and tsunami modeling

International audienceIn the last years, large effort has been done to carry out multi-channel seismic reflection surveys (MCS) in SW Iberia to locate the active tectonic structures that could be related to the generation of the 1755 Lisbon earthquake and the tsunami. The outcome of these researches led to the identification of a large, compressive tectonic structure, named Marques de Pombal thrust that, alone can account for only half the seismic energy released by the 1755 event. However, these investigations have shown the presence of additional tectonic structures active along the continental margin of SW Iberia that are here evaluated to model the tsunami waves observed along the coasts of Iberia, Morocco and Central Atlantic. In this paper we present a new reappraisal of the 1755 source, proposing a possible composite source, including the Marques de Pombal thrust fault and the Guadalquivir Bank. The test of the source is achieved through numerical modelling of the tsunami all over the North Atlantic area. The results presented now incorporate data from the geophysical cruises and the historical observation along the European coasts and also from the Western Indies. The results of this study will, hopefully, improve the seismic risk assessment and evaluation in the Portuguese territory, Spain, Morocco and Central/North Atlantic

The tsumani detector prototype deployed in the Gulf of Cadiz: data collection and functionality evaluation

A new tsunami detector prototype designed to operate in tsunami generation areas has been tested offshore SW Iberia, in the Gulf of Cadiz. The prototype, hosted on board of GEOSTAR has been deployed, at to 3200 meters depth, in August 2007 and recovered one year later by R/V Urania. After refurbishment and a partial upgrade, the tsunameter has been re-deployed in the same location on November 2009 by R/V Sarmiento de Gamboa.We report samples of the data collected by the pressure sensors and the critical analysis of the achievements and problems faced during these test periods

The tsumani detector prototype installed on board of SN1-cabled abyssal station.

The new stand-alone tsunami detector prototype designed to operate in tsunami generation areas, already tested in the Gulf of Cadiz (SW Iberia) on board of GEOSTAR abyssal station, has been re-designed to be hosted on the cabled SN1 abyssal station. A new control software has been implemented to manage, in real time, from the land-based control room the basic component of the tsunameter. The tsunami detection software which perform the real time analysis of the parent tsunami signals, differently form the Gulf of Cadiz stand-alone prototype, runs on a land-based PC. Moreover, the cabled tsunameter is equipped with a new low-frequency hydrophone to detect the hydro-acoustic noise and signals that may be related to tsunami generation

Respicelltm: An innovative dissolution apparatus for inhaled products

To overcome some of the shortfalls of the types of dissolution testing currently used for pulmonary products, a new custom-built dissolution apparatus has been developed. For inhalation products, the main in vitro characterisation required by pharmacopoeias is the deposition of the active pharmaceutical ingredient in an impactor to estimate the dose delivered to the target site, i.e., the lung. Hence, the collection of the respirable dose (<5 µm) also appears to be an essential requirement for the study of the dissolution rate of particles, because it results as being a relevant parameter for the pharmacological action of the powder. In this sense, dissolution studies could become a complementary test to the routine testing of inhaled formulation delivered dose and aerodynamic performance, providing a set of data significant for product quality, efficacy and/or equivalence. In order to achieve the above-mentioned objectives, an innovative dissolution apparatus (RespiCell™) suitable for the dissolution of the respirable fraction of API deposited on the filter of a fast screening impactor (FSI) (but also of the entire formulation if desirable) was designed at the University of Parma and tested. The purpose of the present work was to use the RespiCell dissolution apparatus to compare and discriminate the dissolution behaviour after aerosolisation of various APIs characterised by different physico-chemical properties (hydrophilic/lipophilic) and formulation strategies (excipients, mixing technology)