Spatial Variations In Thickness Research Articles

Change in subfoveal choroidal thickness in central serous chorioretinopathy

Sir, In an article regarding changes in subfoveal choroidal thickness (SFCT) in patients with central serous chorioretinopathy,1 Drs Kang and Kim described decreases in SFCT of 39.9 and 66.9 μm respectively, following observation and treatment with reduced-fluence photodynamic therapy. We would like to highlight some aspects of the study design that may have bearings on the interpretation of these results. Although the authors mentioned diurnal variation in the discussion,1 it does not appear from the description of the methods that this was accounted for in the study design. Earlier studies2, 3 have demonstrated significant diurnal variation of SFCT measured using spectral-domain optical coherence tomography. In these papers, the amplitude (difference between the maximum and minimum choroidal thickness) exceeded 30 μm,2, 3 which is similar in magnitude to the change reported in the observation group in the current paper. Furthermore, when subjects with thicker choroids (defined as ≥400 μm) were sub-analyzed in one paper,2 the mean amplitude was even larger (43.1 μm) with a maximum of 59 μm. In addition to within-subject diurnal variation between the initial and follow-up reviews, it is also important in this study to consider the effects of potentially different measurement times between the two groups of patients (ie, within-group variation), which might have had an effect on the mean choroidal thickness of each group. Another point of interest is whether the authors utilized the eye-tracking feature of the Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) in performing the successive OCT scans between visits. As the choroid is known to exhibit spatial variation in thickness throughout the macula,4, 5 a minor change in the OCT scan position may result in differences in choroidal thickness measurements, which are sufficient to influence the comparison of SFCT. These concerns could have been mitigated by the use of the eye-tracking function that is also available on the Spectralis OCT, which we believe is an important methodological consideration in longitudinal measurements of choroidal thickness. In conclusion, we congratulate the authors on an interesting paper, and urge investigators to consider the impact of diurnal variation of choroidal thickness on the results of such studies.

Nonlinear sediment thickness increase on the western East Pacific Rise flank, 45°S

Sediment thickness was evaluated on the western flank of the East Pacific Rise (EPR) at 45°S, based on high-resolution seismic data gathered during cruise 213/2 of R/V Sonne in 2011. Two zones with distinctly different sediment thickness were identified, separated by a transitional zone bordering a pseudo-fault. Sediment in the more distal zone 2 is almost twice as thick (~120 m) as in zone 1 close to the EPR. This is in contrast to the expected progressive sedimentary column thickening with seafloor age and distance from the spreading axis. The younger of two seismic units detected within the sedimentary column (EPR-2) occurs mainly in the distal zone on crust older than 9 Ma, whereas on younger crust it is present only in small isolated bodies. Both sedimentary units drape the basement. The drape is interpreted to represent particle settling from suspension and a generally low regional primary productivity. The spatial variation in sediment thickness cannot be explained by existing models, and other processes considered in the present case are (1) higher productivity in the western sector of the survey area, where thicker sediments were observed (zone 2), (2) the formation of sediment drifts near basement highs (‘seamount effect’), due to flow of Lower Circumpolar Deep Water affecting sediment deposition, and (3) erosion and/or non-deposition of the younger EPR-2 unit, due to elevated bed shear stresses associated with eddies transferring kinetic energy to the seafloor

Evaluation of critical process parameters for intra-tablet coating uniformity using terahertz pulsed imaging

The purpose of this study was to evaluate the intra-tablet coating uniformity and the identification of critical process parameters in an active pan coating process using terahertz pulsed imaging (TPI). A design of experiments (DoE) was performed with drum load, drum speed, spray rate, run duration and spray pressure as factors. Different measures of intra-tablet uniformity were investigated: the average thickness on the individual tablet faces, spatial variation in layer thickness over the tablet surface, and the coefficient of variation (CVintra). Data analysis revealed that the process parameters in the investigated parameter space had hardly any influence on the difference in layer thickness of the tablet faces and centre band. No increase or decrease in layer thickness – as described in the literature – was found towards the edges of the tablet face. In overwetted process conditions a higher layer thickness at the centre band edges could be observed. Still, the highest variability in coating thickness was found along the circumference of the centre band rather than the height. In general, higher CVintra of layer thickness were found on the centre bands in comparison with the tablet faces. The analysis of the DoE model revealed that the run duration had the highest influence on the CVintra on the tablet faces. TPI showed high potential in the assessment of intra-tablet uniformity and layer thickness distributions over the whole tablet surface. It was successfully used to identify critical process parameters regarding intra-tablet coating uniformity.

Elastic thickness structure of the Andaman subduction zone: Implications for convergence of the Ninetyeast Ridge

We use the Bouguer coherence (Morlet isostatic response function) technique to compute the spatial variation of effective elastic thickness (Te) of the Andaman subduction zone. The recovered Te map resolves regional-scale features that correlate well with known surface structures of the subducting Indian plate and the overriding Burma plate. The major structure on the India plate, the Ninetyeast Ridge (NER), exhibits a weak mechanical strength, which is consistent with the expected signature of an oceanic ridge of hotspot origin. However, a markedly low strength (0<Te<3km) in that region, where the NER is close to the Andaman trench (north of 10°N), receives our main attention in this study. The subduction geometry derived from the Bouguer gravity forward modeling suggests that the NER has indented beneath the Andaman arc. We infer that the bending stresses of the viscous plate, which were reinforced within the subducting oceanic plate as a result of the partial subduction of the NER buoyant load, have reduced the lithospheric strength. The correlation, Te<Ts (seismogenic thickness) reveals that the upper crust is actively deforming beneath the frontal arc Andaman region. The occurrence of normal-fault earthquakes in the frontal arc, low Te zone, is indicative of structural heterogeneities within the subducting plate. The fact that the NER along with its buoyant root is subducting under the Andaman region is inhibiting the subduction processes, as suggested by the changes in trench line, interrupted back-arc volcanism, variation in seismicity mechanism, slow subduction, etc. The low Te and thinned crustal structure of the Andaman back-arc basin are attributed to a thermomechanically weakened lithosphere. The present study reveals that the ongoing back-arc spreading and strike-slip motion along the West Andaman Fault coupled with the ridge subduction exerts an important control on the frequency and magnitude of seismicity in the Andaman region.

Channel belt architecture formed by a meandering river

AbstractStratification in channel belts is the key to reconstructing formative channel dimensions and palaeoflow conditions; this requires an understanding of the relation between river morphodynamics and set thickness. So far, theories for reconstruction of the original morphology from preserved stratification have not been tested for meandering river channels due to the lack of detailed bathymetry. This paper reports the results of an experiment that reproduced a dynamic meandering gravel‐bed river with the objectives to: (i) test the prediction of set thickness as a function of the morphology formed by a meandering river channel; and (ii) explore and explain spatial and temporal set thickness variations in the resulting channel belt. High‐resolution measurements of time‐dependent surface elevation were used to quantitatively relate the preserved stratification to the meandering river morphology. Mean set thickness agrees well with the theoretical prediction from channel morphology. The mean preserved set thickness was 30% of the mean channel depth. Due to the absence of aggradation during the experiment, this provides a lower limit for the preserved mean set thickness which is also to be expected for aggrading systems, because reworking is some orders of magnitude faster than aggradation. Furthermore, the time required to mature a channel belt and its set thickness distribution was about the same as the time required to develop and propagate bends that fill the channel belt surface. Finally, there was much systematic spatial variation in set thickness related to repetitive point bar growth and chute cut‐off. Undisturbed and thick sets occurred close to channel belt margins and more irregular stratification with stacked thinner sets was observed in the centre of the channel belt.

Predicting the thickness and aeolian fraction of soils in upland watersheds of the Mojave Desert

Soil thickness and soil texture, and their spatial variability at hillslope scales, are important inputs for hydrologic models. Recent studies have demonstrated that mechanistic models can accurately predict the spatial distribution of soil thickness in areas where soil thickness varies gradually along hillslope profiles. To date, however, these models have not been tested in arid regions, where soils are often thin and highly variable at small scales (i.e., 1–10m) and where the influence of aeolian accretion on soil thickness and soil texture may be significant. In addition, most of the data available for the fraction of the soil derived from aeolian deposition (which can serve as a proxy for soil texture) originate from soils developed on stable depositional landforms; data for aeolian fractions from upland soils are scarce. In this study, we developed and tested a numerical model for the prediction of thickness and aeolian fraction of soils in arid upland areas. The model assumes a long-term balance between the rates of soil production from bedrock, aeolian accretion, and soil erosion. Rates of soil production are quantified in the model using the exponential and humped soil production functions, and soil erosion rates are quantified using the nonlinear depth- and slope-dependent transport functions, assuming that only the upper soil horizons (A+B) are capable of transport. The rate of aeolian deposition is assumed to be spatially uniform. We calibrated the three free parameters of the model at a site in the Mojave Desert with a granite lithology using a combination of 1) field-measured data for soil thickness and 2) estimation of the aeolian fraction in the soil using laboratory analysis of immobile element concentrations. We validated the model results in three nearby sites using a combination of measured soil thickness in soil pits and the presence/absence of soil, and laboratory analysis of the aeolian fraction of soil. The study area is characterized by generally thin soils (<1m) and extreme variability in soil thickness at small scales. The model does a relatively poor job of predicting the soil thickness on a point-by-point basis due to the extreme small-scale variability, but the model does a much better job at predicting the average soil thickness at the scale of tens of meters and greater. The model predicts soil thickness with a root-mean-square error of 15–32cm in regions characterized by poorly- to moderately-developed calcic soils, but fails to accurately predict soil thickness at a site characterized by well-developed soils (carbonate stages II–IV) and low-relief topography. The model predicts the aeolian fraction and content in soil with root-mean-square errors of 10–13% and 8cm, respectively. The prediction of aeolian content captures the overall pattern of increasing trend in aeolian content towards the lower portions of slopes. Our results show that the model can simultaneously predict the spatial variation of thickness and aeolian fraction/content of soils even in arid, dust-rich environments where soils are thin and spatial variability is extreme.

A modeling perspective on spatial and temporal variations in Messinian evaporite deposits

Abstract During the Messinian Salinity Crisis (MSC), evaporite-dominated sequences formed in marginal and deep basins of the Mediterranean Sea. In the marginal basins, the onset of the MSC is synchronous and a single depositional framework fits all sequences. In contrast, MSC sequences of the western and eastern deep basins appear to comprise a different number of units and differ greatly in thickness. Even though there exist numerous scenarios for deposition in the marginal and deep basins, the link between the two settings is difficult and scenarios are rarely quantitatively supported. We employ a simple box model for the Messinian Mediterranean to examine the causes of (1) spatial variation in thickness and (2) differences in the time of onset of deposition. Model results are compared with actual observations on the MSC sequences. The results show that a large connection between the western and eastern basin is necessary for, and some degree of water column stratification is conducive to, synchronous onset of the MSC in the marginal basins. Moreover, halite deposits in the deep basins are likely to be coeval and have formed in ≈ 60 ka after a (further) restriction of the Atlantic–Mediterranean connection during the MSC, but without a significant sea level drop. A difference in the net salt gain per unit volume caused the different halite deposition rates in the two basins. A scenario with only a simple restriction of the Atlantic–Mediterranean connection during the Late Miocene – without significant changes in the Mediterranean sea level, the fresh water budget, or the size of the Strait of Sicily – is able to explain the synchronous onset of the MSC, the synchronous marginal evaporite formation and the differences in the deep basinal sequences.

Spatial and temporal patterns in erosion and deposition in the York River, Chesapeake Bay, VA

Seasonal patterns of seabed erosion and deposition in a dynamic estuarine environment, the York River (USA), are examined through acoustic studies and seabed sampling to identify the dominant environmental controls on sediment mobility. Areas near Clay Bank in the York River were surveyed monthly using a dual-frequency sonar for a 12 month period. In addition, six stations within these areas were sampled during the surveys. Strong spatial and temporal variations of a soft mud layer were identified, providing new insight to recurring seasonal and spatial patterns in deposition and erosion in the middle reaches of the York River estuary. Sub-bottom data indicated maximum thickness (5–22 cm ± 4 cm) of the soft mud layer during spring and winter from April 2008 through March 2009. Minimum thicknesses (1–12 cm ± 4 cm) of the soft mud layer were observed during summer and fall. Maximum thickness coincided with the occurrence of the secondary turbidity maximum near Clay Bank in the York River. Spatial variations in the soft-mud layer thickness were also identified between and within the York River secondary channel, the inactive oyster reef area, the south west flank of the main channel, and the main channel. The upriver secondary channel, the south west channel flank, and the main channel areas were physically dominated. The downriver secondary channel area was biologically dominated and the inactive oyster reef area reflected both physical and biological processes. Water content trends showed no correlation with seabed stability in this area. Observed changes in soft mud thicknesses are interpreted to result from both biological and physical factors, which vary markedly between winter/spring and summer/fall seasons, and among the different environments of the estuary's channel.

Individual subject classification for Alzheimer's disease based on incremental learning using a spatial frequency representation of cortical thickness data.

Patterns of brain atrophy measured by magnetic resonance structural imaging have been utilized as significant biomarkers for diagnosis of Alzheimer's disease (AD). However, brain atrophy is variable across patients and is non-specific for AD in general. Thus, automatic methods for AD classification require a large number of structural data due to complex and variable patterns of brain atrophy. In this paper, we propose an incremental method for AD classification using cortical thickness data. We represent the cortical thickness data of a subject in terms of their spatial frequency components, employing the manifold harmonic transform. The basis functions for this transform are obtained from the eigenfunctions of the Laplace-Beltrami operator, which are dependent only on the geometry of a cortical surface but not on the cortical thickness defined on it. This facilitates individual subject classification based on incremental learning. In general, methods based on region-wise features poorly reflect the detailed spatial variation of cortical thickness, and those based on vertex-wise features are sensitive to noise. Adopting a vertex-wise cortical thickness representation, our method can still achieve robustness to noise by filtering out high frequency components of the cortical thickness data while reflecting their spatial variation. This compromise leads to high accuracy in AD classification. We utilized MR volumes provided by Alzheimer's Disease Neuroimaging Initiative (ADNI) to validate the performance of the method. Our method discriminated AD patients from Healthy Control (HC) subjects with 82% sensitivity and 93% specificity. It also discriminated Mild Cognitive Impairment (MCI) patients, who converted to AD within 18 months, from non-converted MCI subjects with 63% sensitivity and 76% specificity. Moreover, it showed that the entorhinal cortex was the most discriminative region for classification, which is consistent with previous pathological findings. In comparison with other classification methods, our method demonstrated high classification performance in both categories, which supports the discriminative power of our method in both AD diagnosis and AD prediction.

Regolith modeling and its relation to earthquake induced building damage: A remote sensing approach

Regolith thickness is known as a major factor in influencing the intensity of earthquake induced ground shaking and consequently building damages. It is, however, often simplified or ignored due to its variable and complex nature. To evaluate the role of regolith thickness on earthquake induced building damage, a remote sensing based methodology is developed to model the spatial variation of regolith thickness, based on DEM derived topographic attributes and geology. Regolith thickness samples were evenly collected in geological formations at representative sites of topographic attributes. Topographic attributes (elevation, slope, TWI, distance from stream) computed from the ASTER derived DEM and a geology map were used to explore their role in spatial variation of regolith thickness. Stepwise regression was used to model the spatial variation of regolith thickness in erosional landscape of the study area. Topographic attributes and geology, explain 60% of regolith thickness variation in the study area. To test, if the modeled regolith can be used for prediction of seismic induced building damages, it is compared with the 2005 Kashmir earthquake induced building damages derived from high resolution remote sensing images and field data. The comparison shows that the structural damages increase with increasing regolith thickness. The predicted regolith thickness can be used for demarcating site prone to amplified seismic response.

Analysis and Design of Flexible Pavements by Empirical Tools

This paper falls into two parts. In the first part, the widely used analytical-empirical method of pavement design and evaluation is discussed and in the second part two simulation models are presented to predict the design of flexible pavement. Analytical results are compared with simulation models. There are differences between the assumptions on which the theoretical models are based, and the reality of pavement materials and structures, and these differences are important both for the determination of input values (elastic parameters) and for the calculation of pavement response. Linear elastic theory often results incorrect moduli, when used for back calculation of layer moduli from deflection testing, and in questionable stresses and strains, when used for forward calculation. Including non-linear materials characteristics may improve the theoretical model, but no theoretical model has yet been conclusively verified with experimental data. In the second part of the paper two theoretical models are presented. The first model is stochastic and considers the spatial variation of pavement materials, layer thickness and traffic loads as well as seasonal variations. The second model deals with the forces and displacements the individual grains in a particulate medium. The input to this model includes the grain size distribution, the shape of the grains and the degree of

Deposition and sputtering yields on EUV collector mirror from Laser Plasma Extreme Ultraviolet Sources

Based on the self-similar solution of gas dynamic equations, spherical expansion of the highly ionized plasma with limited mass into a vacuum is investigated for the droplet target laser-produced plasma extreme ultraviolet (LPP-EUV) sources. Using partially numerical and partially analytical technology, the velocity, the temperature and the density profiles in the plume versus ionization degree, adiabatic index and initial conditions are presented. Furthermore, the spatial thickness variations of the deposited substrate witness and ion sputtering yields for Ru, Mo, and Si under Sn ion bombardment are theoretically calculated, which can be useful to enable LPP-EUV sources suppliers to estimate collector lifetime and improve debris mitigation systems.

砂質干潟におけるｆｌｕｉｄ ｍｕｄ堆積物の時空分布：東京湾小櫃川河口盤州干潟

Fluid mud is hig-concentrated near bed suspension, and form relatively thick muddy deposits with rapid sedimentation rate even in coastal and shallow-marine environments that are influenced by wave and/or tidal currents. However, the development of fluid-mud deposits in sandy coastal and shallow-marine environments have not yet clearly been understood, compared with that in muddy coastal and shallow-marine environments. This study investigated lithofacies and distribution patterns of possible fluid-mud deposits in the Banzu sandy flat, Tokyo Bay, central Japan. About 1-m-thick subsurface sandy deposits in the Banzu sandy flat locally contain muddy deposits of 0.5-7 cm thick, and these muddy deposits are interpreted to be fluid-mud deposits on the basis of their distinctive lithofacies and clay fabric. Furthermore, wood and plant fragments and freshwater diatoms in the muddy deposits suggest that these deposits formed from flood-discharge-induced suspensions from an adjacent river called the Obitsu River. Random occurrence and lenticular geometry of the muddy deposits within about 1-m-thick subsurface sandy deposits are also interpreted to indicate that the muddy deposits formed by episodic depositional processes and were preserved as drapes over topographic lows of sandy bars. Furthermore, the maximum thickness of the muddy deposits is documented in a location about 920 m north from the main channel of the Obitsu River. This spatial variation in thickness of the muddy deposits is interpreted that fluid mud, which had once formed at the river mouth during flood discharges, was subsequently transported along the coast. Thus, these spatial and temporal distribution patterns of the muddy deposits are interpreted to be one of the distinctive features of possible fluid-mud deposits, and can be used for the identification of fluid-mud deposits in ancient sandy coastal and shallow-marine successions in conjunction with distinctive features of lithofacies and clay fabric.

Spatial patterns of surface hoar properties and incoming radiation on an inclined forest opening

AbstractAvalanche hazard evaluation relies in part on representative snowpack stability observations. Thus, understanding the spatial patterns of snowpack instabilities and their environmental determinants is crucial. This case study integrates intensive field observations with spatial modeling to identify associations between incoming radiation, surface hoar development and its subsequent shear strength across an inclined forest opening. We examined a buried surface hoar layer in southwest Montana, USA, over five sampling days, collecting 824 SnowMicroPen resistance profiles and performing 352 shear frame tests. Spatial models of incoming long- and shortwave radiation were generated for the surface hoar formation period using modeled hemispheric sky visibility, physically based parameters and the Bird Clear Sky Radiation Model in a Geographic Information System. Before burial, the surface hoar persisted despite moderate winds and relatively high air temperatures. The buried surface hoar layer thickness varied between 3 and 21 mm within a distance of 30 m. Modeled incoming radiation explained spatial variations in layer thickness and shear strength. In areas exposed to large amounts of radiation, the surface hoar layer was strong and thin, while areas with limited incoming radiation (due to high sky visibility and shading) possessed a thicker surface hoar layer that sheared more easily. This demonstrates the usefulness of microclimate modeling for slope-scale avalanche hazard evaluation. We also identify that over the 3 week sample period, strengthening occurred without thinning of the surface hoar layer.

Large-scale spatial variability of dried soil layers and related factors across the entire Loess Plateau of China

A dried soil layer (DSL) is generally formed in the soil profile at a particular depth owing to serious soil desiccation in water-limited ecosystems. The occurrence of DSLs potentially limits the development and sustainability of the ecological environment on the Loess Plateau of China. There is a need to address the spatial variations in DSL thickness (DSLT) and the DSL depth of formation (DSLFD) in this region. We pre-selected 382 sampling sites across the entire Loess Plateau region (620 000 km 2) based on mapped information using an intensive sampling design. A total of 17 906 disturbed soil samples from various soil depths were collected. Using classical statistics, principal component analysis, residual maximum likelihood (REML), and geostatistical methods, we investigated and characterized DSLs and their spatial distribution. There was strong spatial variation in DSLs, which had a mean thickness of 160 cm occurring at a mean soil depth of 270 cm. DSLT was highly correlated with a topographical factor (i.e., slope gradient) that dominated the first principal component (PC), which explained 39% of the variance. Geographical position (i.e., longitude) was important in the second PC. REML analysis demonstrated that land use, rainfall, soil type and slope gradient had a significant impact on DSLT, while only land use, rainfall, and soil type influenced DSLFD significantly. Semivariograms of DSLT indicated weak spatial dependence while DSLFD had moderate spatial dependence. The DSL was generally thicker (> 170 cm) in the western Loess Plateau region and in a central area (170 to 220 cm). Where irrigation was used along parts of the Yellow River and near rivers in the interior, DSLT was considerably thinner or non-existent due to the higher water inputs. Management practices utilizing knowledge of the spatial distribution of DSLs and the factors influencing them can improve land use management to improve the efficiency of vegetation restoration, water management, and to control or reclaim DSLs.

Virtual biopsy of rat tympanic membrane using higher harmonic generation microscopy

Multiharmonic optical microscopy has been widely applied in biomedical research due to its unique capability to perform noninvasive studies of biomaterials. In this study, virtual biopsy based on back-propagating multiple optical harmonics, combining second and third harmonics, is applied in unfixed rat tympanic membrane. We show that third harmonic generation can provide morphologic information on the epithelial layers of rat tympanic membrane as well as radial collagen fibers in middle fibrous layers, and that second harmonic generation can provide information on both radial and circular collagen fibers in middle fibrous layers. Through third harmonic generation, the capillary and red blood cells in the middle fibrous layer are also noted. Additionally, the 3-D relationship to adjacent bony structures and spatial variations in thickness and curvature are obtained. Our study demonstrates the feasibility of using a noninvasive optical imaging system for comprehensive evaluation of the tympanic membrane.

Natural versus anthropogenic aerosols in the eastern Mediterranean basin derived from multiyear TOMS and MODIS satellite data

In the present study we investigate the spatial and temporal variation of aerosol optical thickness (AOT) in the eastern Mediterranean basin, and more specifically in the area extending from 28.5°N to 42.5°N and from 18.5°E to 35.5°E, which includes large urban areas and megacities such as Cairo, Istanbul, Athens, Izmir, Ankara, and Thessaloniki. For this purpose we use long‐term AOT data from the Total Ozone Mapping Spectrometer (TOMS) version2 converted to 500 nm (AOT500) for the period 1980–2001 and Collection 005 AOT data atλ= 550 nm (AOT550) from Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites for the periods 2000–2005 and 2002–2005, respectively. The spatial and temporal variation of AOT shows a good agreement between TOMS and MODIS, in terms of geographical patterns, which maximizes the usefulness of TOMS AOT product given its long temporal coverage (climatological). According to MODIS‐Terra, the annual mean AOT550over the studied region equals 0.22 ± 0.05 (monthly values ranging from 0.14 to 0.32) and shows strong spatial inhomogeneities. The smallest values (down to 0.1) occur over the western, and especially in the northwestern, part of Greece, over the northern part of Anatolian peninsula and also over the sea of east Mediterranean. The largest AOT values (up to about 1.0) occur over northern Africa, Middle East, and the adjacent coasts, and over the Anatolian plateau. These high aerosol loadings are of natural origin, mainly desert dust. However, very large values (up to 0.8) are also found over large urban areas surrounding megacities, associated with anthropogenic, apart from natural desert, aerosols. By using TOMS AOT data as proxy for the dust source, and the difference of MODIS‐TOMS AOT as an indicator of the anthropogenic aerosol component, the relative contribution of natural versus anthropogenic sources of aerosols has been derived for the eastern Mediterranean area. Limitations of this approach are discussed and the associated uncertainties are also evaluated and discussed.

Spatial variations in effective elastic thickness in the Western Pacific Ocean and their implications for Mesozoic volcanism

We have used free-air gravity anomaly and bathymetric data, together with a moving window admittance technique, to determine the spatial variation in oceanic elastic thickness, T e , in the Western Pacific ocean. Synthetic tests using representative seamounts show that T e can be recovered to an accuracy of ± 5 km for plates up to 30 km thick, with increased accuracy of ± 3 km for T e ≤ 20 km. The Western Pacific has a T e range of 0–50 km, with a mean of 9.4 km and a standard deviation of 6.8 km. The T e structure of the region is dominated by relatively high T e over the Hawaiian-Emperor Seamount Chain, intermediate values over the Marshall Islands, Gilbert Ridge, and Marcus-Wake Guyots, and low values over the Line Islands, Mid-Pacific Mountains, Caroline Islands, Shatsky Rise, Hess Rise, and Musician Seamounts. Plots of T e at sites with radiometric ages suggest that T e is to first order controlled by the age of the lithosphere at the time of loading. In areas that backtrack into the South Pacific Isotopic and Thermal Anomaly (SOPITA), T e may be as low as the depth to the 180 ± 120 °C isotherm at least locally. In the northern part of the study area including the Hawaiian-Emperor Seamount Chain, T e correlates with the depth to 310 ± 120 °C. These best-fitting isotherms imply peak rates of volcanism during 100–120 Ma (Early Cretaceous) and 140–150 Ma (Late Jurassic). The corresponding addition of 8 × 10 6 km 3 and 4 × 10 6 km 3 of volcanic material to the surface of the oceanic crust would result in long-term sea-level rises of 20 m and 10 m respectively. The Late Jurassic volcanic event, like the later Early Cretaceous event, appears to have influenced the tectonic evolution of the Pacific plate convergent boundaries, resulting in increased volcanism and orogenesis.

地震および微動観測による石川県鳳珠郡穴水町における地盤震動特性

During the 2007 Noto Hanto earthquake, a K-NET station ISK005, which is located in Anamizu town and approximately 19 km far from the epicenter, recorded the ground velocity larger than 100 cm/s. A set of observational study is carried out to investigate spatial variation of ground motion amplification characteristics in Anamizu town. Firstly, the spatial variation of the amplification was observed by aftershock observations along a temporary linear seismic array across Anamizu town. In the center of the town, the spectral amplification factor is 10 to 20 between 1 Hz and 2 Hz with respect to the rock site. Then, dense single-station microtremor observations were carried out at 147 sites with average spacing of 100 m in Anamizu town to see the spatial variation in thickness of low-velocity layers. The peak frequency of the microtremor H/V spectral ratio varies from 0.8 to 2.0 Hz in the town. The velocity structure model of shallow portion in Anamizu town is estimated from the mircrotremor H/V spectral ratios. The thickness of low-velocity layers (VS =70 to 100 m/s) changes along the Omata and the Manai rivers. Finally, a three-dimensional ground motion simulation is conducted using the obtained velocity structure model in order to see relationship between shallow sedimentary layers and ground motion amplification in Anamizu town. The peak velocity in the frequency range below 2.5 Hz is three or four times larger in the area around ISK005, where the thickness of low-velocity layers is approximately 10 to 25 m, than that in the rock side. It could be concluded that the ground motion amplification characteristics in the frequency range between 1 Hz and 2 Hz is mainly controlled by the existence of such low-velocity sedimentary layers.

Analyzing Variations in Cephalopod Abundances in Shell Concentrations: The Combined Effects of Production and Density-Dependent Cementation Rates

Upper Jurassic ammonoid shell concentrations on pelagic carbonate platforms formed by the mixture of well-preserved and moldic shells provide a unique opportunity to evaluate the effects of average shell durability and productivity on variations in shell abundance preserved in the fossil record. High abundance of primary cement has significantly negative statistical effects on taphonomic alteration, reducing the proportion of ammonoid shells affected by Fe-staining and syndepositional dissolution. High proportions of internal borings indicate that shell concentrations were not rapidly buried. Significantly negative effects of taphonomic alteration on ammonoid shell-packing density and spatial variations in shell-bed thickness show that variations in ammonoid abundance are related to variations in production and destruction rates rather than to variations in sediment dilution. The close spatial association of dissolved aragonite shells and precipitated calcite in shell-rich deposits and the higher proportion of dissolved molds in shell-poor beds demonstrate the simultaneous action of dissolution and cementation in the semiconsolidated mixed layer. These relationships imply positive feedback between the high abundance of ammonoid shells and the low rate of shell destruction, with dissolved carbonate ions from high aragonite input reducing the rate of ammonoid dissolution and providing a local source for carbonate cement. Cementation has the strongest positive relationship with shell-packing density in rank correlations and generalized linear models. Proportions of ammonoid embryonic stages and early juveniles have smaller but significantly positive statistical effects on shell-packing density in simple regressions. We hypothesize that (1) ammonoid shell concentrations correspond to long-term peaks in ammonoid production, with aragonite dissolution buffering the pore-water chemistry, and (2) the increase in ammonoid production rates was related to intervals with average high fecundity coupled with high juvenile mortality.