S. Shariat-Panahi

Precision timing in ocean sensor systems

This paper discusses the use of the IEEE 1588 standard in ocean observatories. The performance result of prototype implementations of this standard in an Ethernet Marine Sensor Network (MSN) is presented. The performance tests emulate an underwater-cabled observatory with a Master Clock synchronized with GPS, located in an on-shore station, and with underwater instruments requiring high-precision PPS (pulse s−1) signals for synchronization purposes. These signals will be provided to the underwater station by an IEEE 1588 GPS Emulator connected to the observatorys Local Area Network (LAN). The experimental setup emulates the underwater-cabled observatory OBSEA where this technology will be installed due to synchronization requirements of marine instruments such as ocean bottom seismometers.

Design and test of a high-resolution acquisition system for marine seismology

Active and passive seismology require high-resolution, low-level signal acquisition. In both methods, the equipment most widely used to acquire seismic data in the marine environment is an ocean bottom seismometer (OBS). We designed and built a high-resolution acquisition system prototype for an OBS that is mainly used in active seismic experiments in which maps are generated of the width and material of ocean bottom sublayers. Other OBS system applications, in which the objective is to estimate the location and magnitude of an earthquake require higher autonomy. When an OBS is used in a permanent seafl oor observatory with no power supply limitation, it can generate tsunami alert signals to shore.

Design, Characterization and Calibration of a Short-Period Ocean Bottom Seismometer (OBS)

First part of this paper presents an ocean bottom seismometers (OBS) designed and constructed for mid-term deployments in order to study the earth dynamics and internal structure. Many marine research institutes have developed such equipment, however there is no standard method for their characterization and calibration. The second part discusses the characterization tests based on the international standards carried out to present the specifications of the equipment built. Calibration of the constructed OBS is carried out through an oceanographic cruise using a widely used reference OBS. Data quality of the instruments is evaluated by direct inspection of the corresponding seismic record sections.

Calibration and modelling of a bottom sea geophone based on Virtual Instrument

This development is a characterization of a geophone sensor with a calibrator and a shaker table in order to obtain the significant parameters and to test the proposed equivalent model. The method is based on a Virtual Instrument and allows to compare the results of the real and simulated measurements by modelling. This application is a geologic prospection to choose the best structures for the geophone. This equipment allows to record useful active and passive seismicity information, by means of acoustic wave front, with multiple applications to the marine environmental research.

Smart IEEE–1588 GPS Clock Emulator for Cabled Ocean Sensors

Today, cabled seafloor observatories are installed at many sites around the globe, gathering different types of sensors in the marine environment where a Global Positioning System (GPS) signal is not accessible. Accurate time marking of ocean sensor data is highly important in many marine applications. This paper presents a smart GPS emulator based on the IEEE-1588 Precision Time Protocol (PTP). The device was designed and implemented to be able to provide accurate timing data (trigger + time code) to any ocean sensor as a broadband seismometer. In this case, accurate location and magnitude of a detected earthquake are dependent on the accuracy of the data time marks. The performance of time synchronization is tested, using a commercial broadband seismometer, and the results are presented. These tests are based on a comparison of the synchronization trigger between master and slave clocks as well as the analysis of the data acquired by the seismometer. The work presented here leads to an improved performance of the ocean-bottom seismometers as well as tsunami warning systems.

Development of a “Synchronization Trigger” for the Spanish Oceanographic Ships Based on an Embedded Real-Time Java System

It is indispensable to have time synchronization and event/pulse generation systems on board oceanographic research vessels to control the data acquisition rate of sensors and equipment. This paper presents a pulse generation system based on the aJ-100 real-time Java embedded system with the capability of being integrated into a general-purpose acquisition system of the BIO Hesperides research vessel named LabVir. In the development of this system, a platform with reduced size and weight and networking technology for system control and data access was used, making its integration easy in any research vessel. Furthermore, a logic design for the event generation was implemented, making the overall system adaptable to any future needs.

A Technique for Detecting Materials Characteristics using Mechanical Impacts and a Multilayer Neural Network

In this paper, we propose a method for detecting the characteristics of different materials that have similar properties, by classifying their responses when impacted with small hard spheres. First, a signal conditioning and data compression stage are described. Then a multilayer neural network is used to detect the individual patterns of the samples, and classify the signal. The results of this study indicate that it is possible to identify different materials propertied when the signals are correctly acquired and preprocessed, and the network is adequately trained.

Design of a Geophone sensor for Marine Deep Seismology

We present the newest development of a geophone sensor. The equipment represents the achievement of a joint work from different scientific and technological disciplines as electronic, mechanics, marine geophysics, etc. This handle equipment allows to record useful active and passive seismicity information, as well as other wave front, with multiple applications to the marine environmental research. We are in the second series prototype hopping to improve many of the aspects that keep the equipment handle and useful to work at deep-water areas.