Comparing the resolution of Bartlett and MVDR estimators for bottom parameter estimation using pressure and vector sensor short array data

This work compares the resolution of a pressure and vector sensor based conventional Bartlett estimator, with their MVDR estimator counterparts, in the context of bottom characterization with a short vertical array. Santos et al. [1]demonstrated the gain of a vector sensor array (VSA) based linear estimator (Bartlett) for generic parameter estimation. Moreover, it was shown that for bottom characterization the highest resolution of the estimates were achieved with the vertical particle velocity measurements alone. The present work highlights the gain in parameter resolution of a VSA based MVDR estimator. It is shown, that also for a MVDR estimator, the vector sensor array data improves the resolution of parameter estimation. But, it is also shown, through simulations, that for bottom parameter estimation, the pressure based MVDR estimator has higher resolution and sidelobe attenuation than the VSA based Bartlett estimator. These results were verified for experimental data acquired by a four element, 30 cm long vertical VSA in the 8–14 kHz band, during the Makai Experiment 2005 sea trial, off Kauai I., Hawaii (USA)

Vector sensor geoacoustic estimation with standard arrays

Vector Sensor Arrays (hereafter VSAs) are progressively becoming more and more attractive among the underwater acoustics community due to the advantages of VSAs over standard arrays of acoustic hydrophones. While the later record only acoustic pressure, VSAs record also particle velocity; such technical feature increases by a factor of four the amount of information that can be used for the processing ofacoustic data, leading to a substantial increase in performance. Since VSA sensor technology is relatively recent, and thus not yet fully available, one can consider the usage of closely located pairs of standard hydrophones, which can be used to estimate the vertical component of particle velocity as a difference of acoustic pressure, measured at each pair of hydrophones. The present discussion introduces a theoretical review of particle velocity calculations using different acoustic models, and tests the performance of estimators for geoacoustic inversion using acoustic pressure, particle velocity components and direct and approximated values of the vertical component only.This work was funded by National Funds through FCT - Foundation for Science and Technology under project SENSOCEAN (PTDC/EEA-ELC/104561/2008)

Comparing the resolution of Bartlett and MVDR estimators for bottom parameter estimation using pressure and vector sensor short array data

Abstract-This work compares the resolution of a pressure and vector sensor based conventional Bartlett estimator, with their MVDR estimator counterparts, in the context of bottom characterization with a short vertical array. Santos et al. [1] demonstrated the gain of a vector sensor array (VSA) based linear estimator (Bartlett) for generic parameter estimation. Moreover, it was shown that for bottom characterization the highest resolution of the estimates were achieved with the vertical particle velocity measurements alone. The present work highlights the gain in parameter resolution of a VSA based MVDR estimator. It is shown, that also for a MVDR estimator, the vector sensor array data improves the resolution of parameter estimation. But, it is also shown, through simulations, that for bottom parameter estimation, the pressure based MVDR estimator has higher resolution and sidelobe attenuation than the VSA based Bartlett estimator. These results were verified for experimental data acquired by a four element, 30 cm long vertical VSA in the 8-14 kHz band, during the Makai Experiment 2005 sea trial, off Kauai I., Hawaii (USA)

Geometry of Holocene Tidal Notches - Sea Level Markers at Perachora Peninsula, Gulf of Corinth, Greece

Οι εγκοπές (notches) που δημιουργούνται από την παλίρροια σε βραχώδεις ακτές αποτελούν ένα βασικό και ευρύτατα διαδεδομένο δείκτη για την θαλάσσια στάθμη, οι οποίες όταν αποκλίνουν από την μέση στάθμη της θάλασσας, υποδηλώνουν τεκτονικές κινήσεις στην ευρύτερη περιοχή των ακτογραμμών. Εντούτοις τα συμπεράσματα που προκύπτουν από τη μελέτη αυτών των δεδομένων είναι συχνά αμφιλεγόμενα ιδιαίτερα σε εφελκυστικά τεκτονικά περιβάλλοντα, όπου η αναμενόμενη τεκτονική ανύψωση δεν αναμένεται να ξεπεράσει τα λίγες δεκάδες εκατοστά σε ένα σεισμικό γεγονός. Μέσω σάρωσης υψηλής ανάλυσης με Λέιζερ μας προσφέρεται η δυνατότητα λεπτομερούς μελέτης των γεωμορφών με σκοπό την ανίχνευση πολλαπλών εγκοπών που αντιπροσωπεύουν γραμμές παλαιοακτών κατά τη διάρκεια διαδοχικών τεκτονικών ανυψώσεων. Ένας αντιπροσωπευτικός αριθμός από προφίλ εγκοπών αναλύθηκαν με σκοπό τον εντοπισμό ήδη περιγραφέντων εγκοπών από την βιβλιογραφία καθώς και την ανάδειξη νέων παρόμοιων εγκοπών με σαφή γεωμετρία κατά μήκος της παράκτιας βραχώδους ζώνης στην χερσόνησο της Περαχώρας. Συνολικά μέσω της εξαγωγής ενός πυκνού τρισδιάστατου δικτύου από σημεία και της ανάλυσης των γεωμορφών παρατηρήθηκε μια αλληλουχία οκτώ εγκοπών οι οποίες διαχωρίζονται μεταξύ τους σε αποστάσεις περίπου 0.3±0.2 m.Tidal notches are a generally accepted sea level indicator that, when different from mean sea level, witness tectonic activity at or near coastlines. However, how to infer related information is controversial since tectonic uplift from a single seismic event is not likely to exceed several decimetres. High resolution laser scanning offers the availability of close-up views on exposures and to detect evidence for multiple sea level indicators in between major emergence. Statistically representative profiles along exposure were analysed in order to prove for already described tidal notches and to highlight similar shapes in consistent geometries along coastal cliffs of Perachora Peninsula