Increase In Wave Speed Research Articles

Study tsunamis through approximate solution of damped geophysical Korteweg-de Vries equation

<abstract><p>The article studied tsunami waves with consideration of important wave properties such as velocity, width, and collision through finding an approximate solution to the damped geophysical Korteweg-de Vries (dGKdV). The addition of the damping term in the GKdV is a result of studying the nonlinear waves in bounded nonplanar geometry. The properties of the wave in bounded nonplanar geometry are different than the unbounded planar geometry, as many experiments approved. Thus, this work reported for the first time the analytical solution for the dGKdV equation using the Ansatz method. The used method assumed a suitable hypothesis and the initial condition of the GKdV. The GKdV is an integrable equation and the solution can be found by several known methods either analytically or numerically. On the other hand, the dGKdV is a nonintegrable equation and does not have an initial exact solution, and this is the challenge. In this work, the novel Ansatz method proved its ability to reach the approximate solution of dGKdV and presented the effect of the damping term as well as the Coriolis effect term in the amplitude of the wave. The advantage of the Ansatz method was that the obtained solution was in a general solution form depending on the exact solution of GKdV. This means the variety of nonlinear wave structures like solitons, lumps, or cnoidal can be easily investigated by the obtained solution. We realized that the amplitude of a tsunami wave decreases if the Coriolis term or damping term increases, while it increases if wave speed increases.</p></abstract>

Analysis of the Differences in Internal Solitary Wave Characteristics Retrieved from Synthetic Aperture Radar Images under Different Background Environments in the Northern South China Sea

Two internal solitary waves (ISWs) with very long fronts observed by synthetic aperture radar (SAR) images in the northern South China Sea (NSCS) are comparatively analyzed based on oceanic reanalysis data and the Korteweg–de Vries (KdV) theory. The differences in the environmental parameters, wave half-width, and amplitude of the two ISW fronts in the two distinct oceanic environments are studied. In the presence of a weak westward surface current of approximately 0.05 m/s, the values of the linear wave speed increase by up to 0.056 m/s, and the retrieved ISW amplitudes decrease by up to 14 m. On the contrary, for another background oceanic environment considering a relatively strong eastward surface current of approximately 0.2 m/s, there are decreases of up to 0.17 m/s in the linear wave speed and increases of up to 32 m in the retrieved amplitudes. However, the results retrieved from both the SAR observations commonly show that the ISW amplitudes along the fronts reach their maximums at roughly 21°N and decrease toward the southern and northern sides, in spite of their distinct background environments.

Constraining the 410-km discontinuity and slab structure in the Kuril subduction zone with triplication waveforms

SUMMARYThe detailed structure near the 410-km discontinuity provides key constraints of the dynamic interactions between the upper mantle and the lower mantle through the mantle transition zone (MTZ) via mass and heat exchange. Meanwhile, the temperature of the subducting slab, which can be derived from its fast wave speed perturbation, is critical for understanding the mantle dynamics in subduction zones where the slab enters the MTZ. Multipathing, i.e. triplicated, body waves that bottom near the MTZ carry rich information of the 410-km discontinuity structure and can be used to constrain the discontinuity depth and radial variations of wave speeds across it. In this study, we systematically analysed the trade-off between model parameters in triplication studies using synthetic examples. Specifically, we illustrated the necessity of using array-normalized amplitude. Two 1-D depth profiles of the wave speed below the Tatar Strait of Russia in the Kuril subduction zone are obtained. We have observed triplications due to both the 410-km discontinuity and the slab upper surface. And, seismic structures for these two interfaces are simultaneously inverted. Our derived 410-km discontinuity depths for the northern and southern regions are at 420$\pm $15 and 425$\pm $15 km, respectively, with no observable uplift. The slab upper surface is inverted to be located about 50–70 km below the 410-km discontinuity. This location is between the depths of the 1 and 2 per cent P-wave speed perturbation contours of a regional 3-D full-waveform inversion (FWI) model, but we found twice the wave speed perturbation amplitude. A wave speed increase of 3.9–4.6 per cent within the slab, compared to 2.0–2.4 per cent from the 3-D FWI model, is necessary to fit the waveforms with the shortest period of 2 s, indicating that high-frequency waves are required to accurately resolve the detailed structures near the MTZ.

Time Dependent Mechanical Crack Closure as a Potential Rapid Source of Post‐Seismic Wave Speed Recovery: Insights From Experiments in Carrara Marble

AbstractSeismological observations indicate strong variations in wave velocities around faults both co‐seismically during earthquakes, and post‐seismically. Recovery is commonly associated with a reduction in crack damage. Here, we explore the recovery associated with time‐dependent mechanical closure of cracks. We report results from laboratory experiments conducted on dry cores of Carrara marble at room temperature. We deformed cylindrical samples in the semi‐brittle regime to induce crack damage before subjecting them to hydrostatic and triaxial stress conditions for extended periods of time while recording dilatancy and wave speeds repeatedly. We report wave speed increases of up to 40% of the damage‐induced wave speed drop in samples subject to hydrostatic loading. Moreover, we report the occurrence of significant wave speed increases contemporaneously with time‐dependent creep in triaxially loaded samples. Wave speed recovery during creep is only observed below a threshold creep strain rate, a result we interpret as a transition from brittle to plastic creep with decreasing strain rate. We interpret the wave speed increase in terms of reduced crack density and increased contact area within the crack array, and show that around 40% of the total crack surface has to be closed to justify the observed wave speed recoveries. We propose that mechanical crack closure is driven by the viscous relaxation of the bulk rock under the influence of locked‐in stresses at low confining pressure, and of the external stresses at higher confining pressure. Our study shows that mechanical crack closure is a significant source of time‐dependent wave speed recovery.

Speed Switch in Glioblastoma Growth Rate due to Enhanced Hypoxia-Induced Migration.

We analyze the wave speed of the Proliferation Invasion Hypoxia Necrosis Angiogenesis (PIHNA) model that was previously created and applied to simulate the growth and spread of glioblastoma (GBM), a particularly aggressive primary brain tumor. We extend the PIHNA model by allowing for different hypoxic and normoxic cell migration rates and study the impact of these differences on the wave-speed dynamics. Through this analysis, we find key variables that drive the outward growth of the simulated GBM. We find a minimum tumor wave-speed for the model; this depends on the migration and proliferation rates of the normoxic cells and is achieved under certain conditions on the migration rates of the normoxic and hypoxic cells. If the hypoxic cell migration rate is greater than the normoxic cell migration rate above a threshold, the wave speed increases above the predicted minimum. This increase in wave speed is explored through an eigenvalue and eigenvector analysis of the linearized PIHNA model, which yields an expression for this threshold. The PIHNA model suggests that an inherently faster-diffusing hypoxic cell population can drive the outward growth of a GBM as a whole, and that this effect is more prominent for faster-proliferating tumors that recover relatively slowly from a hypoxic phenotype. The findings presented here act as a first step in enabling patient-specific calibration of the PIHNA model.

Liver Shear Wave Speed and Other Quantitative Ultrasound Measures of Liver Parenchyma: Prospective Evaluation in Healthy Children and Adults.

OBJECTIVE. The purpose of this study was to use 2D ultrasound shear wave elastography (SWE) to define expected ranges for liver shear wave speed and shear wave dispersion in children and adults without a known history of liver disease. The study also sought to define liver attenuation in adults. SUBJECTS AND METHODS. This was an institutional review board-approved prospective study of 128 children (younger than 18 years old) and 32 adults without liver disease who underwent 2D SWE of the liver with a Canon Aplio i800 ultrasound system (i8CX1 transducer). Ten shear wave speed and shear wave dispersion measurements were obtained. In adults, five attenuation measurements were also obtained. Pearson correlation and t tests were used to define relationships between shear wave speed and dispersion values and predictor variables. Multivariable logistic regression with forward selection was used to generate models. RESULTS. Median age was 5.04 years old for the pediatric participants and 48.92 years old for the adult participants. Mean median shear wave speed and shear wave dispersion were 1.29 ± 0.13 m/s and 11.43 ± 1.75 (m/s)/kHz, respectively, for the pediatric participants and 1.32 ± 0.13 m/s and 10.24 ± 1.65 (m/s)/kHz, respectively, for the adults. Mean median attenuation in adults was 0.52 ± 0.11 dB/cm/MHz. On multivariable modeling, height was the only significant predictor of shear wave speed in children (0.0012 m/s per cm, p < 0.0001) and abdominal wall thickness was the only predictor of shear wave speed in adults (0.12 m/s per cm, p = 0.0008). CONCLUSION. Liver shear wave speed and shear wave dispersion data for children and adults without liver disease provides data against which results from patients with liver disease can be compared. Liver shear wave speed increases during childhood associated with increases in height and shear wave speed increases in adulthood with increasing abdominal wall thickness.

Longitudinal wave speed in rectangular slabs with mixed restraints in lateral directions

Practical problems in structural elements are not confined to simple boundary conditions; often the boundary conditions are mixed. The question of longitudinal wave speed through a rectangular slab is solved herein for the case where the top and bottom surfaces are elastically restrained in the thickness direction while the side surfaces are fully constrained from motion in the width direction. Unlike the classical approach, the current analysis permits changes to the cross-sectional area and density of the considered elemental volume to be accounted for. While it is well established that the wave speed increases and decreases with Young's modulus and density, respectively, the present results additionally show that the wave speed increases with Poisson's ratio magnitude and stiffness of the elastic restraint acting in the thickness direction. Results also indicate that tensile and compressive strains tend to increase and decrease, respectively, the wave speed. The availability of more influencing parameters, arising from the removal of simplifying assumptions, paves a way to greater design options for the practising engineer.

3D computational models explain muscle activation patterns and energetic functions of internal structures in fish swimming

How muscles are used is a key to understanding the internal driving of fish swimming. However, the underlying mechanisms of some features of the muscle activation patterns and their differential appearance in different species are still obscure. In this study, we explain the muscle activation patterns by using 3D computational fluid dynamics models coupled to the motion of fish with prescribed deformation and examining the torque and power required along the fish body with two primary swimming modes. We find that the torque required by the hydrodynamic forces and body inertia exhibits a wave pattern that travels faster than the curvature wave in both anguilliform and carangiform swimmers, which can explain the traveling wave speeds of the muscle activations. Notably, intermittent negative power (i.e., power delivered by the fluid to the body) on the posterior part, along with a timely transfer of torque and energy by tendons, explains the decrease in the duration of muscle activation towards the tail. The torque contribution from the body elasticity further clarifies the wave speed increase or the reverse of the wave direction of the muscle activation on the posterior part of a carangiform swimmer. For anguilliform swimmers, the absence of the aforementioned changes in the muscle activation on the posterior part is consistent with our torque prediction and the absence of long tendons from experimental observations. These results provide novel insights into the functions of muscles and tendons as an integral part of the internal driving system, especially from an energy perspective, and they highlight the differences in the internal driving systems between the two primary swimming modes.

Numerical Research on Initiation of PBXC03 Explosives under Quasi‐Isentropic Loadings

AbstractTo study the influence of different quasi‐isentropic loading modes on the ignition and the detonation growth processes of PBXs, a one‐dimensional numerical model based on the DZK reaction rate model is presented, and then the parameters of DZK reaction rate model of PBXC03 can be experimental calibrated under the quasi‐isentropic loadings. Moreover, the ignition and detonation growth processes of PBXC03 under different quasi‐isentropic loading modes are simulated by using DYNA2D. It is found from the numerical results that both the increase of the peak pressure of shock front and the shock wave speed increase but the time to detonation decreases with the peak loading pressure, loading slope and curvature. It is also found that the explosive initiation process under the quasi‐isentropic loadings can be divided into two stages: one is the initial stage that manifests mainly as the catch‐up and convergence of the quasi‐isentropic waves and the formation of shock waves; the other is the stage of shock initiation, in which a shock wave with a certain intensity is formed and grows gradually into a stable detonation wave. In addition, a necessary condition is proposed to discriminate the feasibility of an quasi‐isentropic loading experimental calibration of the EOS parameters of a unreacted explosive, i. e., the sample's thickness must be smaller than the thickness of initial reaction.

Acoustic wave propagation in disordered microscale granular media under compression

We investigate the effect of dynamic and uniaxial static loading on the wave speeds and rise times of laser generated acoustic waves traveling through a disordered, multilayer aggregate of 2 $$\mu {\mathrm {m}}$$ diameter silica microspheres, where the excited dynamic amplitudes are estimated to approach the level of the static overlap between the particles caused by adhesion and externally applied loads. Two cases are studied: a case where the as-fabricated particle network is retained, and a case where the static load has been increased to the point where the aggregate collapses and a rearrangement of the particle network occurs. We observe increases in wave speeds with static loading significantly lower than, and in approximate agreement with, predictions from models based on Hertzian contact mechanics for the pre- and post-collapse states, respectively. The measured rise time of the leading pulse is found to decrease with increasing static load in both cases, which we attribute to decreased scattering and stiffening of the contact network. Finally, we observe an increase in wave speed with increased excitation amplitude that depends on static loading, and whether the system is in the pre- or post-collapse state. The wave speed dependence on amplitude and static load is found to be in qualitative agreement with a one-dimensional discrete model of adhesive spheres, although the observed difference between pre- and post-collapse states is not captured. This investigation, and the approach presented herein, may find use in future studies of the contact mechanics and dynamics of adhesive microgranular systems.

Continuous Shear Wave Elastography: A New Method to Measure Viscoelastic Properties of Tendons in Vivo

Viscoelastic mechanical properties are frequently altered after tendon injuries and during recovery. Therefore, non-invasive measurements of shear viscoelastic properties may help evaluate tendon recovery and compare the effectiveness of different therapies. The objectives of this study were to describe an elastography method for measuring localized viscoelastic properties of tendons and to discuss the initial results in healthy and injured human Achilles and semitendinosus tendons. The technique used an external actuator to generate the shear waves in the tendon at different frequencies and plane wave imaging to measure shear wave displacements. For each of the excitation frequencies, maps of direction-specific wave speeds were calculated using local frequency estimation. Maps of viscoelastic properties were obtained using a pixel-wise curve fit of wave speed and frequency. The method was validated by comparing measurements of wave speed in agarose gels with those obtained using magnetic resonance elastography. Measurements in human healthy Achilles tendons revealed a pronounced increase in wave speed as a function of frequency, which highlights the importance of tendon viscoelasticity. Additionally, the viscoelastic properties of the Achilles tendon were larger than those reported for other tissues. Measurements in a tendinopathic Achilles tendon indicated that it is feasible to quantify local viscoelastic properties. Similarly, measurement in the semitendinosus tendon revealed substantial differences in viscoelastic properties between the healthy and contralateral tendons. Consequently, this technique has the potential to evaluate localized changes in tendon viscoelastic properties caused by injury and during recovery in a clinical setting.

Scanning acoustic microscopy of biological cryosections: the effect of local thickness on apparent acoustic wave speed

ABSTRACTScanning acoustic microscopy (SAM), when applied to biological samples has the potential to resolve the longitudinal acoustic wave speed and hence stiffness of discrete tissue components. The heterogeneity of biological materials combined with the action of cryosectioning and rehydrating can, however, create variations in section topography. Here, we set out to determine how variations in specimen thickness influence apparent acoustic wave speed measurementsCryosections (5μm nominal thickness) of human skin biopsies were adhered to glass slides before washing and rehydrating in water. Multiple regions (200x200 μm; n = 3) were imaged by SAM to generate acoustic wave speed maps. Subsequently co-localised 30x30 μm sub-regions were imaged by atomic force microscopy (AFM) in fluid. The images were then registered using Image J. Each pixel was allocated both a height and wave speed value before their relationship was then plotted on a scattergram. The mean section thickness measured by AFM was 3.48 ± 1.12 (SD) μm. Regional height variations influenced apparent wave speed measurements. A 3.5 μm height difference was associated with a 400 ms-1 increase in wave speed. In the present study we show that local variations in specimen thickness influence apparent wave speed. We also show that a true measure of wave speed can be calculated if the thickness of the specimen is known at each sampling point.

Effective Temperature of Ions in Traveling Wave Ion Mobility Spectrometry

Traveling wave ion mobility spectrometers (TW IMS) operate at significantly higher fields than drift tube ion mobility spectrometers. Here we measured the fragmentation of the fragile p-methoxybenzylpyridinium ion inside the TW ion mobility cell of the first-generation SYNAPT HDMS spectrometer. The ion's vibrational internal energy was quantified by a vibrational effective temperature T(eff,vib), which is the mean temperature of the ions inside the cell that would result in the same fragmentation yield as observed experimentally. Significant fragmentation of the probe ion inside the TW IMS cell was detected, indicating that field heating of the ions takes place in TW IMS. For typical small molecule IMS conditions, T(eff,vib) = 555 ± 2 K. The variations of the effective temperature were studied as a function of the IMS parameters, and we found that T(eff,vib) decreases when the wave height decreases, when the pressure increases, or when the wave speed increases. The energy transfer efficiency of argon is higher than for He, N(2), or CO(2). With T(eff,vib) being directly related to the ion speed inside the TW IMS, our results also provide new insight on the ion movement in TW IMS. We also discuss the influence of field heating of ions for calibration and structural studies in TW IMS.

Mapping Micro-Mechanical and Micro-Structural Changes in the Ageing Aorta

In healthy individuals, arterial function is critically dependent on the biomechanical properties of stiff fibrillar collagens, resilient elastic fibre proteins and contractile smooth muscle cells. Although age-related reductions in arterial compliance (arteriosclerosis) are associated with chronic hypertension and hence with the development of aortic aneurysms, heart failure and stroke, the differential role played by each of these vascular components in the progression of disease remains unclear.The scanning acoustic microscope (SAM), when operated at frequencies close to 1GHz, is capable of measuring acoustic wave speeds (which are related to tissue stiffness) with a spatial resolution of ∼1 micrometer. Using unfixed tissue cryo-sections, we mapped variations in wavespeed from the intimal surface of young (less than 1.75years) and old (more than 8.00years) sheep aortas. Whilst there was a significant age-related increase in mean wavespeed, across the tissue (young: 1.847km/s, SEM 0.004km/s; old: 1.882km/s, SEM 0.003km/s; Mann Whitney U test, p<0.001) the increase was most pronounced in the inter-lamellar (IL) regions located between large elastic lamellae (EL) (wavespeed increase; IL: 0.047km/s, EL: 0.021km/s). Atomic force microscopy of ovine aorta cryo-sections identified both fine elastic fibres and collagen fibril bundles within this IL space. Collagen and elastin contents of young and old aortas were determined (as a percentage of tissue section area) using light microscopy of picrosirious red and Miller's stained sections respectively. Although collagen content increased significantly in old compared with young sheep (young: 30.97%, SD 2.63%; old: 44.86%, SEM 5.00%; Student's t-test p<0.05) there was no significant change in elastin content (young: 49.75%, SD 4.86%; old: 49.98%, SEM 4.27%; Student's t-test p=0.97).These observations suggest, therefore, that gross mechanical stiffening of the ageing aorta, may occur primarily as a result of localised collagen remodelling in the space between elastic lamellae.

Suppression wave dynamics: Visual field anisotropies and inducer strength

We used binocular rivalry and generalized flash suppression to identify several new shared properties of traveling suppression waves. A strong relationship was found between suppression wave speed and induction pulse strength: increasing the contrast or dot density of the induction pulse led to an increase in wave speed. Evidence of visual field anisotropies in wave propagation speeds were also seen, with suppression waves decelerating as they travel towards the fovea. This deceleration could not be accounted for by cortical magnification in lower level brain areas, suggesting an important role for other, yet to be identified, factors.

Elastic wave speeds and moduli in polycrystalline ice Ih, sI methane hydrate, and sII methane‐ethane hydrate

We used ultrasonic pulse transmission to measure compressional, P, and shear, S, wave speeds in laboratory‐formed polycrystalline ice Ih, sI methane hydrate, and sII methane‐ethane hydrate. From the wave speed's linear dependence on temperature and pressure and from the sample's calculated density, we derived expressions for bulk, shear, and compressional wave moduli and Poisson's ratio from −20 to −5°C and 22.4 to 32.8 MPa for ice Ih, −20 to 15°C and 30.5 to 97.7 MPa for sI methane hydrate, and −20 to 10°C and 30.5 to 91.6 MPa for sII methane‐ethane hydrate. All three materials had comparable P and S wave speeds and decreasing shear wave speeds with increasing applied pressure. Each material also showed evidence of rapid intergranular bonding, with a corresponding increase in wave speed, in response to pauses in sample deformation. There were also key differences. Resistance to uniaxial compaction, indicated by the pressure required to compact initially porous samples, was significantly lower for ice Ih than for either hydrate. The ice Ih shear modulus decreased with increasing pressure, in contrast to the increase measured in both hydrates.

Switching of the transmitters that mediate the depolarization wave in the embryonic chick CNS

We used binocular rivalry and generalized flash suppression to identify several new shared properties of traveling suppression waves. A strong relationship was found between suppression wave speed and induction pulse strength: increasing the contrast or dot density of the induction pulse led to an increase in wave speed. Evidence of visual field anisotropies in wave propagation speeds were also seen, with suppression waves decelerating as they travel towards the fovea. This deceleration could not be accounted for by cortical magnification in lower level brain areas, suggesting an important role for other, yet to be identified, factors.

Seismic tomographic cross-sections of the Bowser Basin in northwest British Columbia, Canada

Abstract First-break travel time picks along about 250 km of the Lithoprobe SNORCLE deep reflection profile were inverted using a 2-D crossing-ray tomographic method to estimate bulk P-wave speed within the uppermost 2 km of crust beneath the Bowser Basin in northwest British Columbia. The purpose was to assess the usefulness of resulting wave-speed models in defining local stratigraphy and structure and in petroleum exploration more generally. Two areas were investigated in detail. Near the Oweegee Dome, deeper levels of exposure at the surface and stratigraphic correlations with a nearby drill hole suggest that a marked regional increase in wave speed occurs at the contact between the lowermost Bowser Lake Group strata and lava flows of the underlying Hazelton Group. Near the northwest corner of the Bowser Basin, a triangle zone inferred from surface structure does not show clearly in the seismic wave-speed model but does contain distinctive horizontal layers of higher wave speed that represent thrust duplexes, igneous intrusions, or mineralization.

CYCLIC-AMP INCREASES THE SPEED OF CARBACHOL-INDUCED APICAL TO BASAL CALCIUM WAVES IN PANCREATIC ACINAR CELLS

Intra-acinar zymogen activation is an early and critical feature of acute pancreatitis. High sustained calcium elevations within the pancreatic acinar cell precede pathologic zymogen activation. However, the determinants of the calcium signal are not clear. We have previously shown that cAMP sensitizes the pancreatic acinar cell to zymogen activation. In this study, we examined the role of cAMP in shaping the dynamics of the calcium signal. We hypothesized that cAMP regulates intra-acinar calcium channel opening in response to calcium-evoking agonists. In these experiments, isolated acinar cells were loaded with the calcium dye fluo4 and imaged using a confocal laser scanning microscope. They were stimulated with the calcium-evoking agonist carbachol (1 uM) in the absence or presence of the cAMP analog 8-Br-cAMP (100 uM). We noted that the rise time after carbachol stimulation was reduced by 55% (p < 0.005) in the basal region of the cell and to a lesser degree in the apical region. In addition, the slope of the calcium rise was increased 2.8 and 1.9 fold in the basal and apical regions, respectively, with cAMP pretreatment (p < 0.01). Furthermore, the speed of the apical-to-basolateral calcium wave increased from 8 to 21 um/sec (p < 0.05). Neither the baseline calcium wave speed nor the cAMP-mediated increase was affected by calcium-free media with EGTA (2 mM). However, dantrolene (100 uM), an inhibitor of the intra-cellular calcium channel the ryanodine receptor, abrogated the cAMP-mediated increase in wave speed (p < 0.05). No differences were noted in the peak calcium response in the apical or basal regions. These data suggest that cAMP affects the speed of the apical to basal calcium wave. Further, the effects of cAMP on the acinar cell calcium wave appear to be dependent on ryanodine receptor opening. We conclude that cAMP appears to regulate ryanodine receptor calcium opening in pancreatic acinar cells.

Dispersive Nonlinear Waves in Two‐Layer Flows with Free Surface Part II. Large Amplitude Solitary Waves Embedded into the Continuous Spectrum

In this paper we study the dispersive model derived in Part I, for the description of long wave propagation in two‐layer flows with free surface. As in the case of the full water–wave problem, this model reproduces the resonance between short waves and long waves. The resulting wave is a generalized solitary wave, characterized by ripples in the far field in addition to the solitary pulse. In this work we focus on particular members of this family resulting from vanishing ripples. These are called embedded solitary waves and they correspond to true homoclinic orbits. Two wave regimes, characterized by elevation or depression of the interface between the layers, are presented. A critical depth ratio separates these two regimes. It is shown how this relates to a change of the global properties for the potential of the Hamiltonian system derived for traveling waves. In oceanic conditions, solitary waves are presented and their broadening is observed as the wave speed increases. We have observed that, for such waves to exist, their speed cannot exceed a certain limit value depending on the density ratio and thickness of each fluid. Finally, other sets of parameters were considered for which multihumped solitons exist, showing the richness and complexity of the Hamiltonian system considered here.