Physics of Traveling Waves in Shallow Water Environment

We present a study of the physical characteristics of traveling waves at shallow and intermediate water depths. The main subject of study is to the influence of nonlinearity on the dispersion properties of waves, their limiting heights and steepness, the shape of solitary waves, etc. A fully nonlinear Serre–Green–Naghdi-type model, a classical weakly nonlinear Boussinesq model and fifth-order Stokes wave solutions were chosen as models for comparison. The analysis showed significant, if not critical, differences in the effect of nonlinearity on the properties of traveling waves for these models. A comparison with experiments was carried out on the basis of the results of a joint Russian–Taiwanese experiment, which was carried out in 2015 at the Tainan Hydraulic Laboratory, and on available experimental data. A comparison with the experimental results confirms the applicability of a completely nonlinear model for calculating traveling waves over the entire range of applicability of the model in contrast to the Boussinesq model, which shows contradictory and unrealistic wave properties for moderate wavelengths.

Underwater Sound Propagation Modeling in a Complex Shallow Water Environment

Three-dimensional (3D) effects can profoundly influence underwater sound propagation in shallow-water environments, hence, affecting the underwater soundscape. Various geological features and coastal oceanographic processes can cause horizontal reflection, refraction, and diffraction of underwater sound. In this work, the ability of a parabolic equation (PE) model to simulate sound propagation in the extremely complicated shallow water environment of Long Island Sound (United States east coast) is investigated. First, the 2D and 3D versions of the PE model are compared with state-of-the-art normal mode and beam tracing models for two idealized cases representing the local environment in the Sound: (i) a 2D 50-m flat bottom and (ii) a 3D shallow water wedge. After that, the PE model is utilized to model sound propagation in three realistic local scenarios in the Sound. Frequencies of 500 and 1500 Hz are considered in all the simulations. In general, transmission loss (TL) results provided by the PE, normal mode and beam tracing models tend to agree with each other. Differences found emerge with (1) increasing the bathymetry complexity, (2) expanding the propagation range, and (3) approaching the limits of model applicability. The TL results from 3D PE simulations indicate that sound propagating along sand bars can experience significant 3D effects. Indeed, for the complex shallow bathymetry found in some areas of Long Island Sound, it is challenging for the models to track the interference effects in the sound pattern. Results emphasize that when choosing an underwater sound propagation model for practical applications in a complex shallow-water environment, a compromise will be made between the numerical model accuracy, computational time, and validity.

Geochemical and Volcanological Criteria in Assessing the Links between Volcanism and VMS Deposits: A Case on the Iberian Pyrite Belt, Spain

VMS deposits in the Iberian Pyrite Belt (IPB), Spain and Portugal, constitute the largest accumulation of these deposits on Earth. Although several factors account for their genetic interpretation, a link between volcanism and mineralization is generally accepted. In many VMS districts, research is focused on the geochemical discrimination between barren and fertile volcanic rocks, these latter being a proxy of VMS mineralization. Additionally, the volcanological study of igneous successions sheds light on the environment at which volcanic rocks were emplaced, showing an emplacement depth consistent with that required for VMS formation. We describe a case on the El Almendro–Villanueva de los Castillejos (EAVC) succession, Spanish IPB, where abundant felsic volcanic rocks occur. According to the available evidence, their geochemical features, εNd signature and U–Pb dates suggest a possible link to VMS deposits. However, (paleo)volcanological evidence here indicates pyroclastic emplacement in a shallow water environment. We infer that such a shallow environment precluded VMS generation, a conclusion that is consistent with the absence of massive deposits all along this area. We also show that this interpretation lends additional support to previous models of the whole IPB, suggesting that compartmentalization of the belt had a major role in determining the sites of VMS deposition.

Bioerosion traces and borings in the Upper Devonian vertebrate remains from the Holy Cross Mountains, Poland Bioerosion in fish remains

Among the hundreds of collected Devonian vertebrate macrofossils in the Holy Cross Mountains, placoderms dominate and provide data on their morphology, distribution and taphonomy. So far 17 out of more than 500 studied specimens have revealed bones with surfaces covered by sediment-filled trace fossils. The traces have been made on the vertebrate remains before their final burial. The borings, oval in cross-section, include dendroidal networks of shallow tunnels or short, straight or curved individual scratches and grooves, which frequently create groups on the both sides of the bones. ?Karethraichnus isp. from Kowala and ?Osteocallis isp. from Wietrznia are the oldest record of these ichnogenera. Sedimentological clues indicate a shallow water environment, probably from the slope below the storm wave base.

Closed-loop surface-related multiple estimation with full-wavefield migration-reconstructed near-offsets for shallow water

Reliably separating primary and multiple reflections in a shallow water environment (i.e., 50 m to 200 m water depth) still remains a challenge. The success of previously published closed-loop surface-related multiple estimation (CL-SRME) depends heavily on the data coverage, i.e., the near-offset reconstruction. Therefore, we propose the integrated framework of CL-SRME and full-wavefield migration (FWM). Multiples recorded in the data are capable of helping infill the acquisition imprint of the FWM image. With this image as a strong constraint, we are able to reconstruct the data at near-offsets, which is essential for better primary and multiple estimation during CL-SRME. FWM applied in a non-linear way can avoid the negative influences from the missing data, and at the same time bring in more physics between primaries and multiples. The FWM image of the top part of the subsurface is also used to back-project the information from multiples to primaries with the physical constraint of all this information belongs to the same earth model, provided that a good description of the source wavefield and a reasonable velocity model are available. The proposed integrated framework first reconstructs near-offsets via the closed-loop imaging process of FWM and then feeds the complete reconstructed data to CL-SRME for better primary and multiple estimation. A good performance is demonstrated on both 2D synthetic and field data examples in a challenging shallow water environment.