Electronic system for drift clock calculation and synchronization for seafloor observatory

The paper describes a new electronic device that allows an easily measurement of the drift between a reference time source (usually GPS) and an atomic rubidium clock which is normally used in seafloor observatories. The Rubidium clock is used in autonomous seafloor observatories to supply reference time for data acquisition with the precision of milliseconds. During the deployment of seafloor observatory the clock is synchronized with GPS. It is critical to evaluate the time drift between the clock and the GPS, when the observatory is recovered. In fact, thanks to an accurate drift measurement it’s possible to have a correct timestamp for data series collected by seafloor observatory’s instruments. The device described in this paper is composed by an Arduino mega shield integrated with other electronic circuits. The device is easily customizable for different clocks in fact Arduino IDE allows development of the desired features for the rubidium clock used in the specific application.Peer Reviewe

Magnetic, electrical, and GPR waterborne surveys of moraine deposits beneath a lake: A case history from Turin, Italy

Bathymetry and bottom sediment types of inland water basins provide meaningful information to estimate water reserves and possible connections between surface and groundwater. Waterborne geophysical surveys can be used to obtain several independent physical parameters to study the sediments. We explored the possibilities of retrieving information on both shallow and deep geological structures beneath a morainic lake by means of waterborne nonseismic methods. In this respect, we discuss simultaneous magnetic, electrical, and groundpenetrating radar (GPR) waterborne surveys on the Candia morainic lake in northerly Turin (Italy).We used waterborne GPR to obtain information on the bottom sediment and the bathymetry needed to constrain the magnetic and electrical inversions. We obtained a map of the total magnetic field (TMF) over the lake from which we computed a 2D constrained compact magnetic inversion for selected profiles, along with a laterally constrained inversion for one electrical profile. The magnetic survey detected some deep anomalous bodies within the subbottom moraine. The electrical profiles gave information on the more superficial layer of bottom sediments. We identify where the coarse morainic material outcrops from the bottom finer sediments from a correspondence between high GPR reflectivity, resistivity, and magnetic anomalie

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

On the parametrization of lateral dose profiles in proton radiation therapy.

Abstract Purpose The accurate evaluation of the lateral dose profile is an important issue in the field of proton radiation therapy. The beam spread, due to Multiple Coulomb Scattering (MCS), is described by the Moliere's theory. To take into account also the contribution of nuclear interactions, modern Treatment Planning Systems (TPSs) generally approximate the dose profiles by a sum of Gaussian functions. In this paper we have compared different parametrizations for the lateral dose profile of protons in water for therapeutical energies: the goal is to improve the performances of the actual treatment planning. Methods We have simulated typical dose profiles at the CNAO (Centro Nazionale di Adroterapia Oncologica) beamline with the FLUKA code and validated them with data taken at CNAO considering different energies and depths. We then performed best fits of the lateral dose profiles for different functions using ROOT and MINUIT. Results The accuracy of the best fits was analyzed by evaluating the reduced χ2, the number of free parameters of the functions and the calculation time. The best results were obtained with the triple Gaussian and double Gaussian Lorentz–Cauchy functions which have 6 parameters, but good results were also obtained with the so called Gauss–Rutherford function which has only 4 parameters. Conclusions The comparison of the studied functions with accurate and validated Monte Carlo calculations and with experimental data from CNAO lead us to propose an original parametrization, the Gauss–Rutherford function, to describe the lateral dose profiles of proton beams

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

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