Seafloor Roughness Research Articles

Numerical simulation of bottom reverberation in the time domain

A model that simulates a mid-frequency (1–4 kHz) direct-path reverberation field in shallow water is presented. This frequency range is important in the applications of detection sonar systems in shallow water. The model assumes that the scattering is caused by seafloor roughness and sub-bottom diffused heterogeneity. A Monte Carlo simulation of the reverberant field in the time domain based on the first-order perturbation approximation is developed. The roughness and sub-bottom heterogeneity are generated based on their power spectra. The computation is handled efficiently by taking advantage of the symmetry of backscattering geometry. The developed code can help to (1) investigate the relative importance of different scattering mechanisms, (2) predict spatial coherence of the scattered field, and (3) simulate and design field experiments. [Work supported by ONR.]

Centimeter scale seafloor relief measurement using an ROV

For high-frequency acoustic backscatter modeling, in the band 1 to 100 kHz, centimeter scale seafloor roughness is an important parameter. A measurement method was devised for deployment aboard a remotely operated vehicle (ROV) consisting of lasers and a video camera. It was designed to measure small-scale roughness in the range of spatial wavelengths from 0.01 to 1 m. The ROV is well suited to this application because it can hover above the seabed, and it can cover a relatively large area. A cylindrical lens was used to spread the laser beam from a low-power laser into a fan, and direct it downward to produce a stripe on the sediment. Viewing from an oblique angle with a video camera, the profile of the sediment directly under the stripe was obtained. The most difficult problem was precisely determining and tracking the position of the ROV. In the SAX99 experiment, positioning was achieved by using small shells and other objects on the seafloor as landmarks. [Work supported by ONR, Ocean Acoustics.]

Variations in axial morphology, segmentation, and seafloor roughness along the Pacific‐Antarctic Ridge between 56°S and 66°S

The spreading rate at the Pacific‐Antarctic Ridge (PAR) increases rapidly from 54 mm/yr near Pitman Fracture Zone (FZ) up to 76 mm/yr near Udintsev FZ, resulting in three domains of axial morphology: an axial valley south of Pitman FZ, an axial high north of Saint Exupéry FZ, and in between, the transitional domain extends over 650 km. It comprises sections of ridge with an axial valley or an axial high and generally displays a very low cross‐sectional relief. It is also characterized by two propagating rifts. Two domains of different seafloor roughness appear south of Udintsev FZ: east of 157°W these two domains are separated by a 1000‐km V‐shaped boundary. West of 157°W, the boundary approximately coincides with Chron 3a or Chron 4. The southward migration of the transitional area during the last 35 Myr explains the V‐shaped boundary: (1) increases in spreading rate above a threshold value produced changes in axial morphology; and (2) in the transition zone, rotations of the spreading direction were accommodated by the plate boundary, either by rift propagation or by transitions from fracture zones to non transform discontinuities, leaving trails on the seafloor that presently delineate the V. Seafloor roughness variations are not controlled by exactly the same spreading rate dependence as changes in axial morphology. The transition from rough to smooth seems to have occurred everywhere for spreading rates greater than 50 mm/yr, except in a domain presently centered on Saint‐Exupéry FZ, where it occurred for spreading rates >60 to 65 mm/yr. Independent results from melting model calculations of major elements [Vlastelic et al., 2000] indicate that the upper mantle temperature is likely to be cooler between Antipodes and La Rose FZs. The combination of these two results reveals the existence of a 700‐km‐long segmentation of the upper mantle, with a “cool” area centered on Saint‐Exupéry FZ.

Effect of bottom ripple on detection of a buried object using shallow-grazing-angle underwater sonar

Sound penetration into the seafloor at shallow (subcritical) sonar grazing angles has been a topic of much discussion lately because measured levels can be much higher than expected based on simple propagation models assuming a flat seafloor. A popular mechanism for explaining this penetration is based on diffraction of energy into the bottom by seafloor roughness. For objects buried in the bottom, this holds the promise for enhanced long range detection with sonar as long as the backscatter by the roughness itself does not overpower the echo from the object. Here the detectability of a sphere buried under roughness in the form of anisotropic wave-induced ripple is investigated by modifying a scattering solution that combines a stochastic perturbative description of the roughness with a deterministic description of the sphere response. [See Lim et al., J. Acoust. Soc. Am. 107, 1246–1262 (2000).] Comparison with predictions for an isotropic, power-law seafloor roughness at a given rms amplitude demonstrates greater high frequency detection capability with rippled seafloors over a wide range of illumination angles relative to the ripple direction. Comparisons with experimental data are also discussed. [Work supported by ONR.]

Biological and hydrodynamic control of seafloor roughness: Implications to high-frequency acoustic scattering

Biological and hydrodynamic processes can both create and destroy seafloor microtopography. As part of the SAX99 experiments, natural and artificial temporal changes in seafloor roughness were monitored acoustically and quantified using bottom stereo photographs. Feeding activities of benthic megafauna and fish destroyed large-scale roughness features generated by ocean surface gravity waves within a period of weeks to months; whereas, fine-scale roughness created by raking the seafloor decayed to background levels within 24 h. The effects of fine-scale roughness increased acoustic scattering centered at one-half the acoustic wavelength (a Bragg wavelength of 2 cm) by 12–18 dB in artificial manipulations of the bottom. These changes were restricted to roughness that was oriented predominantly orthogonal to the incident acoustic waves. Alternatively, seafloor roughness generated by ocean surface gravity waves had wavelengths of 50–100 cm and wave heights of 10–15 cm. These predictable large-scale roughness features should, by analogy, dramatically increase scattering at lower acoustic frequencies (near 1–2 kHz) and decay within weeks to months after storm events. [Work supported by ONR.]

Spatial and temporal variation of large- and small-scale seafloor roughness

Seafloor microtopography, measured at subcentimeter resolution over scales up to a meter or more by underwater stereo photogrammetry, was periodically characterized during the SAX99 high-frequency acoustic backscattering experiment. Analog 35-mm stereo photographs of seafloor roughness were digitized at 2- to 5-mm intervals from film transparencies with a stereo comparator capable of 1-mm-scale lateral precision and submillimeter-scale vertical accuracy. Relative seafloor height profiles were used to estimate roughness power spectra, which are parametrized as slopes and intercepts of regressions fit to the roughness power spectra. The composite roughness model developed by Applied Physics Laboratory–University of Washington requires these two spectral parameters to determine the contribution of the seafloor roughness to the overall backscattering strength. Data from two locations over 31 days in the experimental area off Ft. Walton Beach, FL in 19-m water depth are presented in order to demonstrate the relationship between seafloor roughness morphology at subcentimeter to meter scales and model parameters predicting high-frequency acoustic scattering. Model predictions are generated from the measured geoacoustic properties of the rippled, medium sand seafloor and the range of roughness parameters that varied temporally and spatially during the experiment. [Work supported by ONR.]

Low-grazing-angle monostatic acoustic reverberation from rough and heterogeneous seafloors

Numerical wavefield modeling, based on time domain finite difference solutions to the full elastic wave equation, is used to quantitatively predict the sensitivity of monostatic backscatter to variations in geological properties of the seabed. This article addresses the hypothesis that observed backscatter signals from the seafloor are produced by a combination of seafloor (interface) and subseafloor (volume) scattering from structures having variations at scale lengths comparable to the wavelength of the insonifying acoustic field. Wavelength-scale seafloor roughness and subseafloor volume heterogeneity parameters are defined using stochastic spatial probability functions having Gaussian autocorrelations. The range of the variations in these parameters is constrained to realistic values based on estimates derived from seafloor bathymetry and other geologic data. Modeling results show that backscattering from rough, basaltic (hard) bottoms, in the absence of large-scale seafloor slope, is dominated by rough surface scattering with little contribution from volume scattering. Contrary to this, sediment (soft) bottoms with subseafloor volume heterogeneity, with or without seafloor roughness, produce significant backscattering signals compared to a homogeneous sediment bottom.

Global correlation of mesoscale ocean variability with seafloor roughness from satellite altimetry

Both seafloor bathymetry and eddy kinetic energy at the ocean surface can be estimated by making use of satellite altimeters. Comparing the two quantities shows that in regions of the ocean deeper than about 4800m, surface eddy kinetic energy is greater over smooth abyssal plains than over rough bathymetry, while the opposite is true in shallower waters. Thus in the deep ocean, bottom roughness may dissipate eddy kinetic energy. A simple model indicates that the dissipation rate increases as root‐mean‐squared bottom roughness increases from 0 to 250 m and decreases to negative values (implying eddy generation) for higher roughness.

High-resolution seafloor mapping using the DSL-120 sonar system: Quantitative assessment of sidescan and phase-bathymetry data from the Lucky Strike segment of the Mid-Atlantic Ridge

High-resolution, side-looking sonar data collected near the seafloor (∼100 m altitude) provide important structural and topographic information for defining the geological history and current tectonic framework of seafloor terrains. DSL-120 kHz sonar data collected in the rift valley of the Lucky Strike segment of the Mid-Atlantic Ridge near 37° N provide the ability to quantitatively assess the effective resolution limits of both the sidescan imagery and the computed phase-bathymetry of this sonar system. While the theoretical, vertical and horizontal pixel resolutions of the DSL-120 system are <1 m, statistical analysis of DSL-120 sonar data collected from the Lucky Strike segment indicates that the effective spatial resolution of features is 1–2 m for sidescan imagery and 4 m for phase-bathymetry in the seafloor terrain of the Mid-Atlantic Ridge rift valley. Comparison of multibeam bathymetry data collected at the sea-surface with deep-tow DSL-120 bathymetry indicates that depth differences are on the order of the resolution of the multibeam system (10–30 m). Much of this residual can be accounted for by navigational mismatches and the higher resolving ability of the DSL-120 data, which has a bathymetric footprint on the seafloor that is ∼20 times smaller than that of hull-mounted multibeam at these seafloor depths (∼2000 m). Comparison of DSL-120 bathymetry with itself on crossing lines indicates that residual depth values are ±20 m, with much of that variation being accounted for by navigational errors. A DSL-120 survey conducted in 1998 on the Juan de Fuca Ridge with better navigation and less complex seafloor terrain had residual depth values half those of the Lucky Strike survey. The quality of the bathymetry data varies as a function of position within the swath, with poorer data directly beneath the tow vehicle and also towards the swath edges. Variations in sidescan amplitude observed across the rift valley and on Lucky Strike Seamount correlate well with changes in seafloor roughness caused by transitions from sedimented seafloor to bare rock outcrops. Distinct changes in sonar backscatter amplitude were also observed between areas covered with hydrothermal pavement that grade into lava flows and the collapsed surface of the lava lake in the summit depression of Lucky Strike Seamount. Small features on the seafloor, including volcanic constructional features (e.g., small cones, haystacks, fissures and collapse features) and hydrothermal vent chimneys or mounds taller than ∼2 m and greater than ∼9 m2 in surface area, can easily be resolved and mapped using this system. These features at Lucky Strike have been confirmed visually using the submersible Alvin, the remotely operated vehicle Jason, and the towed optical/acoustic mapping system Argo II.

Premières observations sur la morphologie et les processus sédimentaires récents de l’Éventail celtique

First observations on the morphology and recent sedimentary processes of the Celtic Deep Sea Fan. During the SEDIFAN 1 cruise we surveyed the bathymetry and the acoustic properties of the surface sediment of the Celtic Deep Sea Fan. We also collected Küllenberg cores in order to study recent sedimentary processes. From the bathymetry survey it is relatively easy to recognize the main areas of modern fan. The upper fan included a large sedimentary ridge which constitutes the right levee of the prominent meandering Whittard valley. After its confluence with the Shamrock valley the course of the Whittard valley is abruptly deflected to the south. At a short distance to the south the valley divides into two upper-fan channels, the Celtic channel to the west being the deeper one. This point constitutes the centre of a radiating pattern which is developed on a 150° quadrant and a radius of about 100 km. The acoustic imagery displays contrasted features, related to change in lithology within the first metre beneath the sea bottom and to the sea floor roughness. The Austell ridge exhibits a contrasted pattern of elongated areas with high and low acoustic backscattering levels. This pattern is related to the development of abyssal dunes, the amplitude of which is of metric order. Particularly remarkable is a lobe-shaped low back-scattering area in the western part of the middle fan, also noteworthy are a lineated facies to the west and a braided facies to the east of the fan. The laminated silty-clayey sequences deposited on the Whittard ridge and on the Trevelyan levee were deposited during the deglaciation. We interpret these as turbidity currents overflow deposits from the Whittard valley. At the end of isotopic stage 3 and during stage 2, the English Channel was a large plain flooded by the Channel River. During this period a broad delta developed at 100 m below the present-day depth and a wide spectrum of material was bound to be supplied to the deep sea and contributed particularly to the deposition of the Whittard ridge silty-clayey sequences. The stage 2 deposits are characterized by rhythmic levels enriched in monosulfides. These types of deposits are common in areas affected by fluvial discharges. Excluding the sedimentary ridge and the channel levees the surface deposits sampled with the Küllenberg corer are sandy. These sands are deposited in various contexts on the interfluve between the western and eastern channels and at channel mouths. They were emplaced during high sea level stands as a result of high energy gravity processes. The precise sources of these sands have not yet been identified, however benthic foraminifers from included ooze pebbles have living depths of between 500 and 1 000 m. The gravity processes which eroded this marly ooze may have been triggered on the upper slope. The Celtic shelf is presently a high energy platform where the conjunction of storms and spring tides can lead to enhanced sediment transport from near-shore to the deep sea. The relict or palimpsest deposits of the glacial delta also constitute a large reservoir of sandy material which can also be subject to reworking. © 2000 Ifremer/CNRS/IRD/Éditions scientifiques et médicales Elsevier SAS deep-sea fan / Quaternary / sediment / turbidity / palaeoclimate

Constraints on the proposed Marie Byrd Land‐Bellingshausen Plate Boundary from seismic reflection data

Single‐channel and multichannel marine seismic data off the coast of West Antarctica collected during two Nathaniel B. Palmer cruises (NP92‐8 and NP96‐2) in the vicinity of 65°S to 71°S, 220°E to 250°E, reveal a NNW trending graben. We interpret this graben to be part of the paleodivergent plate boundary between the Marie Byrd Land and Bellingshausen plates. This graben coincides with a −520 nT magnetic anomaly to the NNW and a −720 nT anomaly to the SSE, as well as a 20 mGal negative gravity anomaly. Seismic profiles subparallel to the graben (22 km/Ma half‐spreading rate) reveal greater seafloor roughness to the NE, where seafloor spreading was slower, than to the SW (27 km/Ma half‐spreading rate). These data allow the position of the Marie Byrd Land‐Bellingshausen plate boundary to be constrained more precisely than has previously been possible, with a trend of N17°W from 68.52°S, 233.65°E to 68.41°S, 233.56°E. The sediment‐filled graben has normal separation of sedimentary layers varying from 740±30 m to 580±20 m imaged in seafloor of age A33y (74 Ma).

The influence of millimeter-scale seafloor roughness on measured and predicted high-frequency acoustic backscattering strength

Seafloor microtopography, as measured by underwater stereo photogrammetry, is systematically characterized concurrently with other sediment properties as model parameters to be used for predicting high-frequency acoustic backscattering from the seafloor as part of field experiments. Typically, seafloor roughness is digitized at 2–5 mm intervals from 35- or 70-mm film transparencies with a stereocomparator capable of 1-mm-scale lateral precision and sub-millimeter-scale vertical accuracy. Relative seafloor height profiles are used to estimate roughness power spectra, which are parameterized as slopes and intercepts of the line fit to the roughness variance regressed on the spatial frequency. According to the composite roughness model developed by APL-UW, the decay of the roughness spectra with increasing spatial frequency (slope) and the spectral strength (intercept) can be used to determine the contribution of the seafloor roughness to the overall backscattering strength. Data from field experiments are presented in order to demonstrate the relationship between seafloor roughness at sub-centimeter scales and high-frequency acoustic scattering. Experimental acoustic data and model predictions are presented from a coarse, shelly sea floor off Jacksonville, Florida, a rippled fine sand in the Quinault Range off Washington, and a very fine sand with subtle seafloor roughness off Tirrenia, Italy. [Work supported by ONR.]

Stochastic models for scattering by seafloor roughness

Models for acoustic scattering by seafloor roughness can be divided into numerical models that treat individual realizations of the random seafloor and stochastic models that provide statistical moments representing the scattered field. Such stochastic models require statistical submodels for seafloor roughness and incorporate acoustic submodels that connect statistics of the scattered field with statistics of the random interface. Thus, one must consider the compatibility of the interface and acoustic submodels. Recent work by various investigators has resulted in a number of improvements over classical perturbation and Kirchhoff results. A variety of seafloor types (e.g., fluid, elastic, layered) can now be treated, and improved acoustic approximations permit application over a wider range of roughness parameters. Questions remain, however, as to the accuracy of the newer models. [Work supported by ONR.]

Wave scattering in underwater acoustics

In underwater acoustics it is necessary to take into account the wave scattering by the seafloor. For example, on sonar pictures the speckle noise proceeds from the constructive and destructive interferences between al-lthe waves reflected by the elementary scatterers. The origins of this phenomenon are seafloor roughness and its acoustic properties, wave incidence, frequency, multiples reflections, the dimensions of the insonified surface, etc. The aim of this study is to characterize the scattering of waves exclusively from the roughness. Thus a hypothesis of perfectly reflecting surface is taken. Moreover, specific-geometry periodic surfaces are considered to take into account the multiple reflections and the shadow area easily. Finally it is supposed that the roughness and the wavelength are of the same size. The models to describe the scattered field are based on Kirchhoff’s theory and on Fraunhoffer’s diffraction theory. Some experiences in the acoustic tank yield good agreement between theoretical and experimental results. They show that the orientation and the area of the insonified and observed surfaces are parameters for the scattering angles and for the relative scattered amplitudes.

Acoustic remote sensing of seafloor roughness: Resolving ambiguous estimates of roughness spectrum parameters

To predict or model how sound waves interact with the seafloor some parametrization of the roughness of the sediment–water interface is required. Conversely, bottom backscattered echoes contain information about the roughness of the interface, relative to the acoustic wavelength, often mixed with contributions from inhomogeneities in the sediment volume. However, inversions of seafloor roughness parameters from high-frequency (10–100 kHz) acoustic backscatter measurements often produce ambiguous results with numerous plausible parameter combinations fitting a given acoustic backscatter angular dependence curve or an echo envelope shape. Based on the data and on direct or inferred seafloor roughness measurements reported in the literature, and assuming that the relief spectrum of seafloor topography obeys a power law, it is shown that a level of inversion ambiguity can be lifted by setting the roughness spectral exponent to a value appropriate for the sediment type and by iterating on the spectral strength and the allowable amount of sediment volume backscatter. This is illustrated with examples drawn from comparisons between seafloor echo envelope models and measured acoustic backscatter data yielding interface roughness spectral parameters and rms bottom curvatures consistent with the lithology of the areas investigated. [Work supported by ONR N00014-94-1-0121.]

Recent advances in acoustic sediment classification

Most acoustic techniques used to classify seafloor sediments rely on operator experience and require extensive ground-truth data to calibrate system predictions. Recent developments in transducer design, inversion and deconvolution techniques, and sensor motion composition should improve the reliability and accuracy of normal-incidence, seafloor classification techniques. This presentation provides an introduction to papers that describe the application of these techniques to normal-incidence acoustic returns collected from a variety of siliciclastic and carbonate sediments in coastal waters surrounding Florida and the Bahamas. Site locations and descriptions, sediment characteristics based on in situ and laboratory measurements, and a description of the acoustic measurement techniques are given. In addition, 3-D visualization techniques that provide near real-time presentation of results are described. Profiles of sediment acoustic impedance, compressional wave attenuation, seafloor roughness, and volume heterogeneity are directly determined from acoustic returns and physical constraints. Other properties such as sediment type, grain size, porosity, and shear strength are predicted on the basis of empirical relationships relating acoustic impedance and/or attenuation to sediment physical properties. Comparisons of predicted and measured sediment properties are given and the ping-to-ping variability inherent in acoustic returns is discussed. [Work supported by ONR.]

Characterization of small-scale seafloor roughness using close-range digital photogrammetry

Surface roughness is a fundamental property affecting a variety of physical phenomena including sediment transport and the interaction of acoustic energy with the seafloor. Characterization of bottom roughness and its dynamics is therefore essential for understanding and quantifying the influence of the sediment microtopography. Extensive field measurements of bottom roughness have been taken recently with an end-to-end digital photogrammetry system providing quantitative, two-dimensional surface roughness measurements on spatial scales of approximately a millimeter to a meter. Results of these measurements have shown that sediment surfaces in shallow water are often anisotropic and/or exhibit non-Gaussian height distributions, both of which have the potential to strongly affect seafloor acoustic scatter. For these kinds of surfaces, simple roughness parameters such as rms height or the slope and offset of a power-law representation of the power spectra will not give a sufficiently complete description. Two-dimensional statistical models are needed to capture the anisotropic nature of sediments with oriented features, while for seafloors with peaked forms, it is the phase information in the frequency domain that is required, as this controls the shape characteristics of a surface. Characterization of seafloor roughness based on these ideas will be presented using results from the digital photogrammetry system.

Low-grazing-angle monostatic acoustic reverberation from rough seafloors

The objective of this research is to interpret matched-filtered, beamformed monostatic acoustic reverberation data acquired when the seafloor is insonified by a bandlimited, low-grazing-angle acoustic pulse. This paper addresses the hypothesis that observed backscatter signals are produced by a combination of seafloor (interface) and subseafloor (volume) scattering from structure having variations at scale lengths comparable to the wavelength of the insonifying acoustic field. Numerical modeling, using a finite-difference solution to the elastic wave equation, is performed to quantitatively predict the monostatic acoustic reverberation signals from rough seafloor, with and without subseafloor volume heterogeneity. Wavelength-scale seafloor roughness and subseafloor volume heterogeneity are defined using stochastic distributions with Gaussian autocorrelations. Modeling results show that scattering from rough, basaltic bottoms is dominated by interface scattering. Subseafloor volume heterogeneity is shown to be capable of producing scattered signals comparable to rough seafloor scattering when the bottom is smooth and/or has a low velocity.

The impact of anisotropic roughness on acoustic interaction with the seafloor

Accurate description of small scale sediment roughness and its dynamics plays an essential role in the understanding of high-frequency acoustic interaction with the seafloor. The influence of surface waves can be very strong in shallow water, commonly producing relatively large, oriented, and quasi-periodic sediment features, i.e., ripple fields. One-dimensional analysis, which can be limiting in the study of anisotropic seafloors, has traditionally been used to describe sediment roughness spectra. Due to the windowing and averaging operations used to reduce bias at higher spatial frequencies, these studies have usually missed the small bandwidth components that exist. This talk will focus on seafloor roughness and acoustic measurements taken recently on rippled seafloors near Elba Island, Italy. Results of high-resolution two-dimensional roughness measurements obtained with a fully digital close-range photogrammetry system will be presented and compared with previous descriptions of roughness spectra. Acoustic backscatter and penetration measurements, which show a definite sensitivity to the anisotropic nature of the seafloor, will be compared to models that incorporate the measured ripple structure.

Effect of subducting sea-floor roughness on fore-arc kinematics, Pacific coast, Costa Rica

Research Article| May 01, 1998 Effect of subducting sea-floor roughness on fore-arc kinematics, Pacific coast, Costa Rica Donald M. Fisher; Donald M. Fisher 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar Thomas W. Gardner; Thomas W. Gardner 2Department of Geosciences, Trinity University, San Antonio, Texas 78212 Search for other works by this author on: GSW Google Scholar Jeffrey S. Marshall; Jeffrey S. Marshall 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar Peter B. Sak; Peter B. Sak 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Search for other works by this author on: GSW Google Scholar Marino Protti Marino Protti 3Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Apartado 86-3000, Heredia, Costa Rica Search for other works by this author on: GSW Google Scholar Author and Article Information Donald M. Fisher 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Thomas W. Gardner 2Department of Geosciences, Trinity University, San Antonio, Texas 78212 Jeffrey S. Marshall 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Peter B. Sak 1Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania 16802 Marino Protti 3Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Apartado 86-3000, Heredia, Costa Rica Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1998) 26 (5): 467–470. https://doi.org/10.1130/0091-7613(1998)026<0467:EOSSFR>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Donald M. Fisher, Thomas W. Gardner, Jeffrey S. Marshall, Peter B. Sak, Marino Protti; Effect of subducting sea-floor roughness on fore-arc kinematics, Pacific coast, Costa Rica. Geology 1998;; 26 (5): 467–470. doi: https://doi.org/10.1130/0091-7613(1998)026<0467:EOSSFR>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Fault kinematics and uplift in the Costa Rican fore arc of the Middle America convergent margin are controlled to a large extent by roughness on the subducting Cocos plate. Along the northwest flank of the incoming Cocos Ridge, seafloor is characterized by short wavelength roughness related to northeast-trending seamount chains. Onland projection of the rough subducting crust coincides with a system of active faults oriented at high angles to the margin that segment the fore-arc thrust belt and separate blocks with contrasting uplift rates. Trunk segments of Pacific slope fluvial systems typically follow these margin-perpendicular faults. Regionally developed marine and fluvial terraces are correlated between drainages and across faults along the Costa Rican Pacific coast. Terrace separations across block-bounding faults reveal a pattern of fore-arc uplift that coincides roughly with the distribution of incoming seamounts. Magnitude and distribution of Quaternary uplift along the Costa Rican Pacific coast suggests that, despite a thin incoming sediment pile, the inner fore arc shows an accumulation of mass—a characteristic that may be due to underplating of seamounts beneath the fore-arc high. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.