scholarly journals Frictional stability of porous tuff breccia under subsurface pressure conditions and implications for shallow seismicity

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Kazuo Mizoguchi ◽  
Shin-ichi Uehara ◽  
Takehiro Hirose ◽  
Sachiko Iizuka
Keyword(s):  
Laboratory Data ◽  
Sediment Layer ◽  
Velocity Dependence ◽  
Coseismic Slip ◽  
Boundary Shear ◽  
Shallow Zone ◽  
Electron Microscopes ◽  
Major Surface ◽  
Sediment Layers ◽  
Tuff Breccia

AbstractThick sediment layers frequently cover the Japan islands’ surface, and their frictional properties significantly affect the shallow slip behavior that occurs during earthquakes. However, laboratory data on the properties of the shallow zone remain limited. We collected tuff breccia samples from deep borehole cores in the Miocene “Green Tuff” formation, a major surface cover, and performed velocity-stepping friction tests on these samples under in situ stresses of 2 to 20 MPa to assess the velocity dependence of their frictional strength. The samples exhibit predominantly frictionally stable, velocity-strengthening behavior over the range of normal stresses tested, which supports the hypothesis that shallow sediment layers are seismically quiescent. This result is consistent with the low seismicity and attenuation of coseismic slip occurring in the shallow zone that is observed during regional earthquakes. Microstructural observations of the postmortem samples using optical and scanning electron microscopes indicate a fabric transition from boundary shear localization to distributed cataclastic flow with increasing normal stress. Our laboratory investigation of the depth-variable distribution of the frictional velocity dependence of a shallow sediment layer would provide further insight into the mechanical role for earthquake rupture dynamics and shallow seismicity.

scholarly journals Frictional Stability of Porous Tuff Breccia Under Subsurface Pressure Conditions and Implications for Shallow Seismicity

2021 ◽  
Author(s):  
Kazuo Mizoguchi ◽  
Shin-ichi Uehara ◽  
Takehiro Hirose ◽  
Sachiko Iizuka
Keyword(s):  
Normal Stress ◽  
Laboratory Data ◽  
Unconsolidated Sediments ◽  
Sediment Layer ◽  
Velocity Dependence ◽  
Coseismic Slip ◽  
Electron Microscopies ◽  
Boundary Shear ◽  
Shallow Zone ◽  
Tuff Breccia

Abstract Thick layers of unconsolidated sediments are widespread in the Japan island’s surface, and their frictional properties significantly affect the shallow slip behavior during earthquakes. However, laboratory data on the properties of the shallow zone remain limited. We collected tuff breccia samples from deep borehole cores of the Miocene “Green Tuff” formation, a major surface cover, and performed velocity-stepping friction tests on them under in situ stresses of 2 to 20 MPa to assess the velocity-dependence of frictional strength. The samples exhibit predominantly frictionally stable, velocity-strengthening behavior over the range of normal stress tested, which supports the hypothesis that shallow sediment layers are seismically quiescent. The result is consistent with the low seismicity and attenuation of coseismic slip in the shallow zone observed for the regional earthquakes. Microstructural observations of the postmortem samples through optical and scanning electron microscopies indicate a fabric transition from boundary shear localization to distributed cataclastic flow with increasing normal stress. Our laboratory investigation on depth-variable distribution of friction velocity dependence of a shallow sediment layer would provide further insight into the mechanical role for earthquake rupture dynamics and shallow seismicity.

scholarly journals The δ13C, δ18O and Δ47 records in biogenic, pedogenic and geogenic carbonate types from paleosol-loess sequence and their paleoenvironmental meaning

2021 ◽  
pp. 1-17
Author(s):  
Kazem Zamanian ◽  
Alex R. Lechler ◽  
Andrew J. Schauer ◽  
Yakov Kuzyakov ◽  
Katharine W. Huntington
Keyword(s):  
Land Snail ◽  
Isotopic Signature ◽  
Sediment Layer ◽  
Isotopic Signatures ◽  
Pedogenic Carbonates ◽  
Rhine Valley ◽  
Clumped Isotope ◽  
Time Specific ◽  
Sediment Layers ◽  
Paleoenvironmental Reconstructions

Abstract Paleoenvironmental reconstructions are commonly based on isotopic signatures of a variety of carbonate types, including rhizoliths and land-snail shells, present in paleosol-loess sequences. However, various carbonate types are formed through distinct biotic and abiotic processes over various periods, and therefore may record diverging environmental information in the same sedimentological layer. Here, we investigate the effects of carbonate type on δ13C, δ18O, and clumped isotope-derived paleotemperature [T(Δ47)] from the Quaternary Nussloch paleosol-loess sequence (Rhine Valley, SW Germany). δ13C, δ18O, and T(Δ47) values of co-occurring rhizoliths (-8.2‰ to -5.8‰, -6.1‰ to -5.9‰, 12–32°C, respectively), loess dolls (-7.0‰, -5.6‰, 23°C), land-snail shells (-8.1‰ to -3.2‰, -4.0‰ to -2.2‰, 12–38°C), earthworm biospheroliths (-11‰, -4.7‰, 8°C), and “bulk” carbonates (-1.9‰ to -0.5‰, -5.6‰ to -5.3‰, 78–120°C) from three sediment layers depend systematically on the carbonate type, admixture from geogenic carbonate, and the duration of formation periods. Based on these findings, we provide a comprehensive summary for the application of the three isotopic proxies of δ13C, δ18O, and Δ47 in biogenic and pedogenic carbonates present in the same sediment layer to reconstruct paleoenvironments (e.g., local vegetation, evaporative conditions, and temperature). We conclude that bulk carbonates in Nussloch loess should be excluded from paleoenvironmental reconstructions. Instead, pedogenic and biogenic carbonates should be used to provide context for interpreting the isotopic signature for detailed site- and time-specific paleoenvironmental information.

scholarly journals Detection and Identification of Sediment Layer to Discover the Marine Mineral Resources Potential in Aruah Islands

2021 ◽  
Vol 9 (1) ◽  
pp. 70
Author(s):  
Pareng Rengi ◽  
Ulil Amri ◽  
Tomi Ramadona ◽  
Ediar Usman ◽  
Bustari Bustari
Keyword(s):  
Sediment Sample ◽  
Single Channel ◽  
Low Frequency ◽  
Mineral Resources ◽  
Coarse Sand ◽  
Sediment Layer ◽  
Sediment Thickness ◽  
Seismic Profiles ◽  
Detection And Identification ◽  
Sediment Layers

<p>Aruah Islands is located on an international shipping line adjacent to Malaysia. The important aspect in borderline management is the maritime resource potential, one of which is sea minerals. In order to dig the information about marine mineral resources in Aruah Islands, a high-resolution seismic reflection with low frequency was applied, which capable to detect the depth and identify the sedimentary layers clearly and accurately. The depth of water and sediment layers were detected using an echosounder, reason Navi sound type 210 with a tow fish 100 kHz and shallow seismic boomer with a single channel type and wave energy 200 Joules. Gravity core and grab sampler were used to collect the sediment sample. There were three stages on seismic interpretation: sequence analysis, facies analysis, and reflection character identification. Furthermore, sediments containing coarse sand-sized minerals were observed using a microscope. The measurement result of Aruah Islands water depth was ranging from 0-80 m, the deepest part is on the Northern of Batu Mandi island which was 80 m depth. Seismic profiles indicated that the upper layer of tertiary sedimentary as the youngest rocks. Based on sediment thickness, the thickest area was found on the Western (approx. 50 m) and the Northern (approx. 32 m). In line with the island’s Southern part condition, which was plain or shallow sea exposure, the Southeastern island sediment thickness ranged only about 10-18 m. Generally, based on the analyzed sediment sample, quartz was the main mineral found, which was 60-80% of the composition. Other minerals were zircon, tin, hematite, magnetite, limonite, biotite, and dolomite.</p>

How Does Sedimentary Layering Affect the Generation of Tsunamis?

2009 ◽  
Author(s):  
Denys Dutykh ◽  
Fre´de´ric Dias
Keyword(s):  
Half Space ◽  
Hard Rock ◽  
Test Case ◽  
Sediment Layer ◽  
Sedimentary Deposits ◽  
Vertical Displacements ◽  
Generation Region ◽  
Sediment Layers ◽  
Parameter Values ◽  
Future Work

This article presents preliminary results on the influence of sediment layers on the process of tsunami generation. The main scope here is to demonstrate and especially quantify the effect of sedimentation on vertical displacements of the seabed due to an underwater earthquake. The effects in the far field are left for future work. The elastodynamics equations are integrated with a finite element method and the fault is modelled as a dislocation in a half-space. A comparison between two cases is performed. The first one corresponds to the classical situation of an elastic homogeneous and isotropic half-space, which is traditionally used for the generation of tsunamis. The second test case takes into account the presence of a sediment layer separating the oceanic column from the hard rock. Some important differences are revealed. We conjecture that deformations in the generation region may be amplified by sedimentary deposits, at least for some parameter values. The mechanism of amplification is studied through careful numerical simulations.

Slip-dependent weakening revealed for a shallow megasplay fault in the Nankai subduction zone

2020 ◽  
Author(s):  
Alexander Roesner ◽  
Matt Ikari ◽  
Andre Huepers ◽  
Achim Kopf
Keyword(s):  
Normal Stress ◽  
Constant Velocity ◽  
Submarine Landslides ◽  
Normal Stresses ◽  
Velocity Dependence ◽  
Ocean Drilling Program ◽  
Coseismic Slip ◽  
Megathrust Earthquakes ◽  
Effective Normal Stress ◽  
Integrated Ocean Drilling Program

&lt;p&gt;The Nankai Trough megasplay fault likely hosts different modes of fault slip, from slow to megathrust earthquakes, and is responsible for related phenomena such as tsunamis and submarine landslides. All types of slip events require some kind of frictional weakening process (e.g. slip and/or velocity weakening) in order to nucleate and propagate. Most frictional earthquake studies analyze the velocity dependence of friction but disregard the slip dependence of friction observed in experimental friction studies.&lt;/p&gt;&lt;p&gt;We tested fluid-saturated powdered megasplay fault samples from Integrated Ocean Drilling Program Site C0004 in a direct shear apparatus under effective normal stresses from 2&amp;#160;&amp;#8211;&amp;#160;18&amp;#160;MPa to investigate the velocity- and slip-dependence of friction of the megasplay fault. For every tested effective normal stress, we performed one velocity-step experiment and two constant velocity experiments (no velocity step). In the velocity-step experiments the samples were sheared to a total displacement of 10&amp;#160;mm, with an initial sliding velocity V&lt;sub&gt;0&lt;/sub&gt;&amp;#160;=&amp;#160;0.1&amp;#160;&amp;#181;m/s for the first ~5&amp;#160;mm (run-in) followed by a velocity step increase to V&amp;#160;=&amp;#160;1.0&amp;#160;&amp;#181;m/s over the last 5 mm. During the constant velocity experiments, the shearing velocity (0.1 and 1.0&amp;#160;&amp;#181;m/s respectively) was held constant for 10&amp;#160;mm of displacement.&lt;/p&gt;&lt;p&gt;The velocity-stepping tests showed an evolution from velocity weakening at low effective normal stresses to velocity strengthening at high effective normal stresses. All experiments revealed strong slip-weakening behavior, with the slip dependence having a much larger effect on friction than the velocity dependence. The friction slip dependence is also controlled by the effective normal stress, showing large weakening rate at low effective normal stresses and smaller weakening rate at higher effective normal stresses. Therefore, both frictional weakening mechanisms on the megasplay fault become more effective at shallow depths. This may amplify seafloor deformation by shallow coseismic slip and could increase the tsunamigenic potential of the fault zone.&lt;/p&gt;

scholarly journals Community structure and microhabitat preferences of harpacticoid copepods in a tropical reef lagoon (Zanzibar Island, Tanzania)

2008 ◽  
Vol 88 (4) ◽  
pp. 747-758 ◽  
Author(s):  
H. Gheerardyn ◽  
M. De Troch ◽  
S.G.M. Ndaro ◽  
M. Raes ◽  
M. Vincx ◽  
...  
Keyword(s):  
Community Structure ◽  
Habitat Preferences ◽  
Harpacticoid Copepod ◽  
Sediment Layer ◽  
Coral Sand ◽  
Harpacticoid Copepods ◽  
Structural Differences ◽  
Tropical Reef ◽  
Microhabitat Preferences ◽  
Sediment Layers

Three microhabitat types (dead coral fragments, coral gravel and coral sand) were distinguished and sampled at two locations (Matemwe and Makunduchi) in a tropical lagoon (Zanzibar Island, Tanzania), and the community structure, habitat preferences and biodiversity of the associated harpacticoid copepod fauna was investigated. The harpacticoid fauna is affected by sediment granulometry and by the structural differences between coral and both gravel and sediment. The coral fragments contained a specific assemblage composed of typical ‘phytal’ taxa(Tisbe,ParadactylopodiaandDactylopusia)along with other eurytopic and sediment-dwelling forms (Ameira,EctinosomaandAmphiascus), which may be attracted by the sediment retained between the coral branches. The assemblages of coral gravel and upper sediment layer did not differ significantly from each other and had mostly the same dominant genera. The sediment from Matemwe was dominated by the interstitial Paramesochridae and the sediment from Makunduchi by Tetragonicipitidae. The coral fragments from Makunduchi sustained a more diverse assemblage than gravel and the different sediment layers. It was assumed that coral form and complexity, with implications for habitable space, nutritional resources and level of predation, are important in structuring diversity of the associated assemblage.

Diversity and habitat selectivity of harpacticoid copepods from sea grass beds in Pujada Bay, the Philippines

2008 ◽  
Vol 88 (3) ◽  
pp. 515-526 ◽  
Author(s):  
Marleen De Troch ◽  
Jenny Lynn Melgo-Ebarle ◽  
Lea Angsinco-Jimenez ◽  
Hendrik Gheerardyn ◽  
Magda Vincx
Keyword(s):  
Harpacticoid Copepod ◽  
Spatial Diversity ◽  
The Philippines ◽  
Grass Species ◽  
Sediment Layer ◽  
Harpacticoid Copepods ◽  
Sea Grass ◽  
Tidal Gradient ◽  
Sediment Layers ◽  
Total Diversity

The spatial diversity of meiofauna from sea grass beds of Pujada Bay (the Philippines), was studied with special emphasis on harpacticoid copepods. Sediment cores were obtained from areas adjacent to the different species of sea grasses. Meiofauna was enumerated at higher taxon level and harpacticoid copepods were identified to genus level. Diversity indices were calculated corresponding to the hierarchical levels of spatial biodiversity, i.e. alpha, beta and gamma. Nematodes were the most abundant meiofaunal group in all sediment layers and along the entire tidal gradient (37–92%); harpacticoids were second in abundance (3.0–40.6%) but highly diverse (N0: 9.33–15.5) at the uppermost sediment layer (0–1 cm) near all beds of sea grass species. There was a sharp turnover of harpacticoid genera along the tidal gradient, thus suggesting a relatively low proportion of shared genera among benthic communities in different sea grass zones. The families of Tetragonicipitidae and Miraciidae were the dominant harpacticoid groups occurring in all sediment layers of all sea grass species. The presence of the epiphytic genera of Metis at the deepest sediment layers in some sea grass species was striking. Overall, the major contributor to gamma (total) diversity of harpacticoid copepods in Pujada Bay is the high local (alpha) diversity (N0: 80.6%, H′: 94.7% of total diversity); hence, the habitat heterogeneity among sediment layers in sea grass beds is most relevant for the total diversity and richness of harpacticoid copepod genera in the area.

405. The composition of the soluble and insoluble portions of reconstituted milk powders

1949 ◽  
Vol 16 (3) ◽  
pp. 379-389 ◽  
Author(s):  
R. Waite ◽  
J. C. D. White
Keyword(s):  
Calcium Phosphate ◽  
Milk Powder ◽  
Manufacturing Processes ◽  
Sediment Layer ◽  
Considerable Similarity ◽  
Whole Milk ◽  
Calcium And Phosphorus ◽  
Sediment Layers ◽  
Reconstituted Milk ◽  
Whole Milk Powder

1. The mode of distribution of the constituents of centrifuged reconstituted whole-milk powder manufactured by different processes has been determined at 20 and 50° C.2. Where considerable ‘insolubility’ exists, protein is carried into the fat layer and fat into the sediment layer in quantities directly related to the degree of ‘insolubility’. The fat in the sediment of roller powders appears to be associated almost entirely with the protein which remains insoluble at 50° C.3. The sediments from reconstituted whole- and separated-milk powders made by different manufacturing processes have been obtained in bulk by vigorous centrifuging (14,500 × g). Analysis of these sediments reveals considerable similarity between them, and it is concluded that a well-washed sediment would consist mainly of denatured calcium caseinate together with calcium and phosphorus in the same proportions as in normal tricalcium phosphate, Ca3(PO4)2, the calcium caseinate and most of the calcium phosphate probably being in the form of a casein-phosphate complex.4. The accuracy of some published methods of measuring milk powder solubility has been considered, and the inaccuracies arising from the non-homogeneity of the fat and sediment layers are stressed.

scholarly journals CellTracker Green labelling vs. Rose Bengal staining: CTG wins by points in distinguishing living from dead anoxia-impacted copepods and nematodes

2013 ◽  
Vol 10 (2) ◽  
pp. 2857-2887 ◽  
Author(s):  
M. Grego ◽  
M. Stachowitsch ◽  
M. De Troch ◽  
B. Riedel
Keyword(s):  
Rose Bengal ◽  
Adriatic Sea ◽  
Staining Method ◽  
Tipping Points ◽  
Sediment Layer ◽  
Short Term ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
Harpacticoid Copepods ◽  
Sediment Layers

Abstract. Hypoxia and anoxia have become a key threat to shallow coastal seas. Much is known about their impact on macrofauna, less on meiofauna. In an attempt to shed more light on the latter group, in particular from a process-oriented view, we experimentally induced short-term anoxia (1 week) in the Northern Adriatic Sea, Mediterranean, and examined the two most abundant meiofauna taxa – harpacticoid copepods and nematodes. Both taxa also represent different ends of the tolerance spectrum, with copepods being the most sensitive and nematodes among the most tolerant. We compared two methods: CellTracker Green (CTG) – new labelling approach for meiofauna – with the traditional Rose Bengal (RB) staining method. CTG binds to active enzymes and therefore colours live organisms only. The two methods show considerable differences in the number of living and dead individuals of both meiofauna taxa. Generally, RB will stain dead but not yet decomposed copepods and nematodes equally as live ones. Specifically, RB significantly overestimated the number of living copepods in all sediment layers in anoxic samples, but not in any normoxic samples. In contrast, for nematodes, the methods did not show such a clear difference between anoxia and normoxia. Surprisingly, RB overestimated the number of living nematodes in the top sediment layer of normoxic samples, which implies an overestimation of the overall live nematofauna. For monitoring and biodiversity studies, the RB method might be sufficient, but for more fine-scaled (days, hours, tipping points) studies, especially on hypoxia and anoxia where it is necessary to resolve the course of events, CTG labelling is a better tool. Moreover, it clearly highlights the surviving species within the copepod or nematode community. As already accepted for foraminiferal research, we demonstrate that the CTG labelling is also valid for other meiofauna groups.

scholarly journals Image analysis for measuring the size stratification in sand–gravel laboratory experiments

2014 ◽  
Vol 2 (1) ◽  
pp. 217-232 ◽  
Author(s):  
C. Orrú ◽  
V. Chavarrías ◽  
W. S. J. Uijttewaal ◽  
A. Blom
Keyword(s):  
Grain Size ◽  
Image Analysis ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Measurement Method ◽  
Laboratory Experiments ◽  
Size Fraction ◽  
Sediment Layer ◽  
Areal Fraction ◽  
Sediment Layers

Abstract. Measurements of spatial and temporal changes in the grain-size distribution of the bed surface and substrate are crucial to improving the modelling of sediment transport and associated grain-size selective processes. We present three complementary techniques to determine such variations in the grain-size distribution of the bed surface in sand–gravel laboratory experiments, as well as the resulting size stratification: (1) particle colouring, (2) removal of sediment layers, and (3) image analysis. The resulting stratification measurement method was evaluated in two sets of experiments. In both sets three grain-size fractions within the range of coarse sand to fine gravel were painted in different colours. Sediment layers are removed using a wet vacuum cleaner. Subsequently areal images are taken of the surface of each layer. The areal fraction content, that is, the relative presence of each size fraction over the bed surface, is determined using a colour segmentation algorithm which provides the areal fraction content of a specific colour (i.e. grain size) covering the bed surface. Particle colouring is not only beneficial to this type of image analysis but also to the observation and understanding of grain-size selective processes. The size stratification based on areal fractions is measured with sufficient accuracy. Other advantages of the proposed size stratification measurement method are (a) rapid collection and processing of a large amount of data, (b) a very high spatial density of information on the grain-size distribution, (c) the lack of disturbances to the bed surface, (d) only minor disturbances to the substrate due to the removal of sediment layers, and (e) the possibility to return a sediment layer to its original elevation and continue the flume experiment. The areal fractions are converted into volumetric fractions using an existing conversion model.

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