North-East Pacific Undersea Network Experiments (NEPTUNE) is a multi-node cabled ocean observatory linked by 818 kilometers of powered fiber optic cable off-shore from Vancouver Island across the northern Juan de Fuca tectonic plate. It includes a Data Management and Archive Station (DMAS) at the University of Victoria (UVic) and a shore station at Port Alberni, BC, Canada. The core of the network consists of 6 branching units, 6 node stations, 13 junction boxes and more than 130 instruments. In this paper, we explore the costs and benefits of constructing a simulator for NEPTUNE using the OMNeT++ simulation platform---a C++ based discrete-event simulator. In this context, we present the design and implementation of a simple simulator that can work with a variety of configurations of instruments, where the instruments are connected to DMAS via junction boxes and branching units, and generate TCP and UDP traffic following certain patterns. The simulator is designed for supporting \emph{what-if} scenario analysis, particularly with respect to system evaluation and discovery of limits associated with network traffic behaviors. Our study reveals that, although building the simulator in OMNeT++ has many advantages such as ease of tuning and calibration, capturing sufficient details regarding the working behavior of the actual NEPTUNE environment is still challenging. A survey of alternative tools, including NS-2/NS-3, OPNET, JiST/SWANS, J-Sim, SSFNet, and Qualnet reveals that these nuances would not be any less challenging within these simulation environments. / Graduate

Using the NEPTUNE-Canada cable-linked ocean-floor observatory we plan continuous, real-time monitoring of the gas hydrate-associated, “Bullseye” cold vent offshore Vancouver Island. Our group inferred the presence of a massive gas hydrate deposit there, based on the significant resistivity anomaly in our controlled-source electromagnetic (CSEM) dataset, as well as anomalously heightened shear moduli, from seafloor compliance data. This interpretation was confirmed by drilling by IODP expedition 311 (site U1328), which indicated a 40 m thick gas hydrate layer near the surface. Sporadic venting and variations in blanking in yearly single-channel seismic surveys suggest the system is evolving in time. We are preparing two stationary semi-permanent imaging experiments: a CSEM and a seafloor compliance installation. These are designed not only to assess the extent of the gas hydrate deposit, but also for long-term monitoring of the gas hydrate/free gas system. The principle of the CSEM experiment is to input a particular electromagnetic signal at a transmitter (TX) dipole on the seafloor, and to record the phase and amplitude of the response at several seafloor receiver (RX) dipoles, at various TX-RX separations. The data are sensitive to the underlying resistivity, which is increased when conductive pore water is displaced by electrically-insulating gas hydrate. The experiment is controlled onshore, and can be expanded to include a downhole TX. Repeated soundings at this site, over several years, will allow measurement of minute changes in resistivity as a function of depth, and by inference, changes in gas hydrate or underlying free gas distribution. Similarly, the displacement of pore fluids by solid gas hydrate will affect elastic parameters. Thus, seafloor compliance data, the transfer function between pressure and seafloor displacement time series, most sensitive to shear modulus as a function of depth, will be gathered continuously to monitor the evolution of the gas hydrate distribution.