Automatic Estimation of the Seafloor Geomorphology of the Santos Basin, Brazil

The bathymetry and acoustic backscatter of Santos Basin, Brazil were mapped using a SeaBeam 2112 (12 kHz, 151 beam) Multibeam Echosounder (MBES) aboard the R/V Falcon Explorer. This MBES data was acquired from January-November, 2000, during a high-resolution multi-channel 3D seismic survey, resulting in 380 parallel lines of 90 km length, spaced 250 m apart. The final survey mapped an area of 5,000 km${}^2$ in water depths of 900--2000 m. These closely spaced multibeam tracks resulted in an average overlap between swaths of 1000%, thereby ensonifying most areas of the seafloor at least ten times. Traditional (hand) processing of a dataset this dense is time-consuming and tedious, and is prone to subjective decisions and operator fatigue. However, the density of the survey makes it ideal for automatic processing methods. Recently, we have developed an algorithm called CUBE that addresses the twin concerns of robustness and reliability that are often raised about automatic processing methods. Based on a very robust multiple hypothesis Bayesian estimator, CUBE processes MBES bathymetry directly into a set of gridded products representing the best estimate of probable depth, and a measure of the uncertainty associated with this estimate. We apply CUBE to the Santos Basin data, illustrating in terms of processing time and human effort the advantages of processing such data automatically. We compare the automatically generated data with a hand-processed set, showing that the results agree to within the estimated experimental uncertainty. We next illustrate the use of CUBE as a data quality measure, indicating areas of concern in the data. Finally, we utilize the bathymetric grid resulting from CUBE to investigate the seafloor morphology, which includes a set of linear depressions parallel and perpendicular to the Shelf break. These linear depressions are the surface expression of fault planes related to subsurface salt walls. In the shallowest part, the detailed bathymetry also shows various pockmarks (350 m wide) possibly associated with fluid expulsion, while in the deeper portion we observe a small number of larger ones (2500 m wide), which are clearly inactive as they are partially filled with recent sediments. Some pockmarks are aligned with fault planes, suggesting a preferential pathway for fluid expulsion. The acquisition geometry for this survey allowed us to analyze the behavior of the backscatter response as a function of grazing angle for any given piece of seafloor, thus eliminating the need to assume a homogeneous seafloor across the swath. Although the backscatter is not calibrated, the variation in response can be used to investigate the effects of gas in shallow sediments of the survey area

Bibliography on the Scyphozoa with selected references on Hydrozoa and Anthozoa

Our goal in assembling this bibliography has been to bring together literature references on all aspects of scyphozoan research. Compilation was begun in 1967 as a card file of references to publications on the Scyphozoa; selected references to hydrozoan and anthozoan studies that were considered relevant to the study of scyphozoans were included. In 1968, a major research program on the jellyfish of Chesapeake Bay was initiated at the Virginia Institute of Marine Science (VIMS) under Dr. E. B. Joseph, and work on the bibliography became an integral part of the program. In 1969 we began converting the bibliography into a form suitable for wider distribution, and in February 1970 a preliminary draft was completed. The present bibliography is an expanded and revised version of the preliminary draft

The Athol Syncline: tectonic evolution of a Westphalian A-B depocentre in the Maritimes Basin, Nova Scotia

In the western Cumberland Basin, Nova Scotia, significant thickening of Westphalian A-B strata towards the axis of the Athol Syncline suggests that development of the syncline coincided with that of the depocentre. This contrasts with stratigraphic relations typical of the Late Paleozoic Maritimes Basin where thinning of Westphalian B strata indicates regional, Late Carboniferous erosion or non-deposition. Post-depositional structural complications within the Athol Syncline include truncation of its southern limb by a near-vertical, east-west zone of strike-slip faulting. This zone, the Athol-Sand Cove Fault Zone (ASCFZ), has been correlated to the west with a complex zone of faulting exposed on the coast of Chignecto Bay where numerous normal, reverse and oblique-slip displacements suggest predominantly brittle deformation and changes in the sense of strike slip. To the east, the ASCFZ splays north into the Springhill coalfield where it is responsible for complex patterns of normal, reverse and strike-slip faulting within Westphalian A-B coal measures. Major Late Carboniferous strike-slip faults adjacent to the Athol Syncline record dextral motion south of the Cumberland Basin (on the east-west Cobequid Fault) and possible sinistral motion along the basin's northwestern margin (on the northeast-southwest Harvey-Hopewell Fault). These faults are respectively interpreted to be synthetic and antithetic structures related to a regional dextral shear regime in which the east-northeast-west-southwest Athol Syncline and its associated depocentre formed in response to the direction of local compression during basin development. However, kinematic analyses indicate that post-depositional motion on the ASCFZ was predominantly sinistral. Development of the Athol Syncline is therefore interpreted to have been controlled by dextral, syndepositional transpression during the Late Carboniferous, whereas later, post-depositional displacement across the ASCFZ reflects predominantly sinistral transtension and may be related to the opening of the Fundy Basin which reversed the sense of regional shear during the Middle Triassic. RÉSUMÉ Dans la partie ouest du bassin de Cumberland en Nouvelle Écosse, un épaississement important des strates du Westphalien A-B vers Paxe du synclinal d'Athol suggère que le développement du synclinal à coincide avec celui du centre de déposition. Ceci contraste avec les relations stratigraphiques typiques du bassin des Maritimes du Paléozoique tardif où L’amincissement des strates du Westphalien B indique une erosion régionale ou une absence de déposition au Carbonifere tardif. Les complications strucrurales après déposition à l'intérieur du synclinal d'Athol comprennent la troncature de son flanc sud par une zone de faille de décrochement est-ouest quasi-verticale. Cette zone, la zone de faille d'Athol-Sand Cove (ZFASC), à été correlée vers l'ouest avec une zone de faille complexe éxposée sur la côte de la baie de Chignecto où de nombreux déplacements normaux, inverses et obliques suggerent une déformation principalement cassante et des variations du sens de décrochement. Vers Test, la ZFASC se divise vers le nord dans le bassin houiller de Springhill où elle est responsable d'un reseau complexe de failles normales, inverses et de décrochement dans les séquences houilleres du Westphalien A-B. Les failles majeures de décrochement du Carbonifère tardif adjacentes au synclinal d'Athol montrent un mouvement dextre au sud du bassin de Cumberland (le long de la faille de Cobequid d'orientation est-ouest) et peut-être un mouvement senestre le long de la bordure nord-ouest du bassin (le long de la faille d'Harvey-Hopewell, d'orientation nord-est - sud-ouest). Ces failles sont interpréters comme des structures synthétiques et antithétiques liées a un régime régional de décrochement dextre responsable de la formation du synclinal d'Athol d'orientation est-nord-est - ouest-sud-ouest et du centre de dépôt associé en réponse à la direction de compression locale durant le développement du bassin. Cependant, des analyses cinematiques indiquent que le mouvement postérieur au dépôt le long de la ZFASC était principalement senestre. Le développement du synclinal d'Athol est done interpréte comme ayant été controle par une transpression dextre contemporaine au dépôt durant le Carbonifère tardif, tandis que le emplacement plus tardif, posterieur au dépôt, de la ZFASC reflete principalement une transtension senestre et pourrait être liée à L’ouverture du bassin de Fundy qui a inversé le sens du cisaillement régional pendant le Trias moyen [Traduit par la rédaction

High-Precision, High-Accuracy Timekeeping in Distributed Survey Systems

Accurate and precise timekeeping between computers in a distributed survey system is essential to ensure adequate data quality, especially with Multibeam Echosounders (MBES) which can otherwise suffer from significant motion artefacts. We show that clock synchronisation on the order of 100-150ns (rms) is readily achievable in a modern MBES-based survey system utilising an Ethernet-based time synchronisation mechanism and some custom timekeeping software. We also show that improving the timekeeping eliminates motion artefacts in the observed bathymetry, and simplifies the patch-test procedure.Para asegurar una calidad adecuada de los datos es esencial una exacta y precisa mantencion de la hora entre ordenadores en un sistema de levantamiento distribuido, especialmente con Sondadores Acusticos Multihaz (MBES), que sino pueden experimentar las consecuencias de un significativo movimiento de sus artefactos. Mostramos que la sincronizaci6n de un reloj en el orden de 100-150ns (rms) puede llevarse a cabo facilmente en un sistema moderno de levantamientos efectuados mediante MBES, utilizando un mecanismo Ethernet basado en la sincronizacion del tiempo y en algun programa de mantencion de la hora adaptado. Tambien mostramos que mejorando la mantencion de la hora se elimina el movimiento de los artefactos en la batimetria observada, y simplifica el procedimiento de pruebas en parches.Il est essentiel d'avoir un chronometrage exact et precis entre ordinateurs dans un systeme integre pour les leves hydrographiques afin d'assurer une qualite des donnees appropriee notamment pour les sondeurs multifaisceaux (MBES) qui, dans le cas contraire, peuvent patir de perturbations significatives liees au mouvement. Nous montrons qu'une synchronisation des horloges de l'ordre de 100 a 150ns (valeur quadratique moyenne) est facilement obtenue dans un systeme de leves moderne reposant sur les MBES et utilisant un mecanisme de synchronisation du temps dans un reseau Ethernet et un logiciel specifique de chronometrage. Nous demontrons egalement que l'amelioration du chronometrage permet de supprimer certaines perturbations liees au mouvement dans la bathymetrie observee et de simplifier la procedure d'essai par plage

High-Precision, High-Accuracy Timekeeping in Distributed Survey Systems

Accurate and precise timekeeping between computers in a distributed survey system is essential to ensure adequate data quality, especially with Multibeam Echosounders (MBES) which can otherwise suffer from significant motion artefacts. We show that clock synchronisation on the order of 100-150ns (rms) is readily achievable in a modern MBES-based survey system utilising an Ethernet-based time synchronisation mechanism and some custom timekeeping software. We also show that improving the timekeeping eliminates motion artefacts in the observed bathymetry, and simplifies the patch-test procedure.Para asegurar una calidad adecuada de los datos es esencial una exacta y precisa mantencion de la hora entre ordenadores en un sistema de levantamiento distribuido, especialmente con Sondadores Acusticos Multihaz (MBES), que sino pueden experimentar las consecuencias de un significativo movimiento de sus artefactos. Mostramos que la sincronizaci6n de un reloj en el orden de 100-150ns (rms) puede llevarse a cabo facilmente en un sistema moderno de levantamientos efectuados mediante MBES, utilizando un mecanismo Ethernet basado en la sincronizacion del tiempo y en algun programa de mantencion de la hora adaptado. Tambien mostramos que mejorando la mantencion de la hora se elimina el movimiento de los artefactos en la batimetria observada, y simplifica el procedimiento de pruebas en parches.Il est essentiel d'avoir un chronometrage exact et precis entre ordinateurs dans un systeme integre pour les leves hydrographiques afin d'assurer une qualite des donnees appropriee notamment pour les sondeurs multifaisceaux (MBES) qui, dans le cas contraire, peuvent patir de perturbations significatives liees au mouvement. Nous montrons qu'une synchronisation des horloges de l'ordre de 100 a 150ns (valeur quadratique moyenne) est facilement obtenue dans un systeme de leves moderne reposant sur les MBES et utilisant un mecanisme de synchronisation du temps dans un reseau Ethernet et un logiciel specifique de chronometrage. Nous demontrons egalement que l'amelioration du chronometrage permet de supprimer certaines perturbations liees au mouvement dans la bathymetrie observee et de simplifier la procedure d'essai par plage

Power laws of complex systems from Extreme physical information

Many complex systems obey allometric, or power, laws y=Yx^{a}. Here y is the measured value of some system attribute a, Y is a constant, and x is a stochastic variable. Remarkably, for many living systems the exponent a is limited to values +or- n/4, n=0,1,2... Here x is the mass of a randomly selected creature in the population. These quarter-power laws hold for many attributes, such as pulse rate (n=-1). Allometry has, in the past, been theoretically justified on a case-by-case basis. An ultimate goal is to find a common cause for allometry of all types and for both living and nonliving systems. The principle I - J = extrem. of Extreme physical information (EPI) is found to provide such a cause. It describes the flow of Fisher information J => I from an attribute value a on the cell level to its exterior observation y. Data y are formed via a system channel function y = f(x,a), with f(x,a) to be found. Extremizing the difference I - J through variation of f(x,a) results in a general allometric law f(x,a)= y = Yx^{a}. Darwinian evolution is presumed to cause a second extremization of I - J, now with respect to the choice of a. The solution is a=+or-n/4, n=0,1,2..., defining the particular powers of biological allometry. Under special circumstances, the model predicts that such biological systems are controlled by but two distinct intracellular information sources. These sources are conjectured to be cellular DNA and cellular transmembrane ion gradient

Simulations of Astrophysical Fluid Instabilities

We present direct numerical simulations of mixing at Rayleigh-Taylor unstable interfaces performed with the FLASH code, developed at the ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago. We present initial results of single-mode studies in two and three dimensions. Our results indicate that three-dimensional instabilities grow significantly faster than two-dimensional instabilities and that grid resolution can have a significant effect on instability growth rates. We also find that unphysical diffusive mixing occurs at the fluid interface, particularly in poorly resolved simulations.Comment: 3 pages, 1 figure. To appear in the proceedings of the 20th Texas Symposium on Relativistic Astrophysic