Causes and consequences of the great strength variability among soft Nankai accretionary prism sediments from offshore SW-Japan

Geophysical Research AbstractsVol. 16, EGU2014-10666, 2014EGU General Assembly 2014© Author(s) 2014. CC Attribution 3.0 License.Causes and consequences of the great strength variability among softNankai accretionary prism sediments from offshore SW-JapanMichael Stipp (1), Kai Schumann (1), Bernd Leiss (2), and Klaus Ullemeyer (3)(1) GEOMAR, Marine Geodynamics, Kiel, Germany ([email protected], [email protected]), (2)Geowissenschaftliches Zentrum, Universität Göttingen, Germany ([email protected]), (3) Institut für Geowissenschaften,Universität Kiel, Germany ([email protected])The Nankai Trough Seismogenic Zone Experiment of the International Ocean Discovery Program (IODP) isthe very first attempt to drill into the seismogenic part of a subduction zone. Offshore SW-Japan the oceanicPhilippine sea plate is subducted beneath the continental Eurasian plate causing earthquakes of magnitude 8.0 to8.5 and related tsunamis with a recurrence rate of 80-100 years. For the tsunamigenic potential of the forearc slopeand accreted sediments their mechanical strength, composition and fabrics have been investigated. 19 drill coresamples of IODP Expeditions 315, 316 and 333 were experimentally deformed in a triaxial cell under consolidatedand undrained conditions at confining pressures of 400-1000 kPa, room temperature, axial shortening rates of0.01-9.0 mm/min, and up to an axial strain of64% (Stipp et al., 2013). With respect to the mechanical behavior,two distinct sample groups could be distinguished. Weak samples from the upper and middle forearc slope ofthe accretionary prism show a deviatoric peak stress after only a few percent strain (< 10%) and a continuousstress decrease after a maximum combined with a continuous increase in pore pressure. Strong samples fromthe accretionary prism toe display a constant residual stress at maximum level or even a continuous stressincrease together with a decrease in pore pressure towards high strain (Stipp et al., 2013). Synchrotron textureand composition analysis of the experimentally deformed and undeformed samples using the Rietveld refinementprogram MAUD indicates an increasing strength of the illite and kaolinite textures with increasing depth downto 523 m below sea floor corresponding to a preferred mineral alignment due to compaction. Experimentallydeformed samples have generally stronger textures than related undeformed core samples and they show alsoincreasing strength of the illite and kaolinite textures with increasing axial strain. Mechanically weak samples havea bulk clay plus calcite content of 31-65 vol.-% and most of their illite, kaolinite, smectite and calcite [001]-polefigures have maxima >1.5 mrd. Strong samples which were deformed to approximately the same amount of strain(up to 40%) have no calcite and a bulk clay content of 24-36 vol.-%. Illite, kaolinite and smectite [001]-pole figuremaxima are mostly <1.5 mrd, except for one sample which was deformed to a considerably higher strain (64%).The higher clay and calcite content and the stronger textures of the mechanically weak samples can be related toa collapsing pore space of the originally flocculated clay aggregates. This process is insignificant in the strongsamples from the prism toe, for which deformation would tend to involve large rock volumes and lead to straindissipation. The weak samples from the forearc slope which become even weaker with increasing strain mayprovoke mechanical runaway situations allowing for earthquake rupture, surface breakage and tsunami generation.Stipp, M., Rolfs, M., Kitamura, Y., Behrmann, J.H., Schumann, K., Schulte-Kortnack, D. and Feeser, V.2013. G-Cubed 14/11, doi: 10.1002/ggge.20290

On the fluid-mobility of molybdenum, tungsten, and antimony in subduction systems

Molybdenum (Mo) and tungsten (W) have long been regarded as being more or less immobile during slab fluid-induced arc magma generation. Here we characterize about 180 samples of young, predominantly mafic to intermediate tephras and lavas for their Mo, W, and antimony (Sb) concentrations, to examine the fluid-mobility of these elements in subduction systems. Samples were taken along the active arcs of the Chilean Southern Volcanic Zone (SVZ) and the Central American Volcanic Arc (CAVA). When relating Mo, W, and Sb to trace element ratios typically used to constrain the involvement of subduction fluids in magma formation, such as Ba/La or U/Th, Mo, W, and Sb are enriched in the most fluid-influenced, highest-degree melts. W/Mo ratios correlate positively with Pb/Ce, which is established to reflect a recent subduction signal or assimilation of crustal material with an ancient subduction signature, suggesting that subduction processes promote enrichment of W over Mo. This is well expressed at the SVZ and most of the CAVA; while few OIB-type rocks from Central Costa Rica form an opposite trend. Moreover, Mo/W ratios co-vary with Cl contents derived from melt inclusions, indicating that the relative degree of mobilization responds to the composition of the subduction fluid. To evaluate the mobility of Mo, W, and Sb during metamorphism in the slab, eclogites with no or minor metasomatic overprint and a fluid-induced overprint in an eclogite-blueschist sequence were investigated. None of the three elements shows a systematic variability related to metasomatism and the minor variations are interpreted to reflect protolith heterogeneity. This suggests that Mo, W and Sb remain relatively immobile up to depths of 70 km in the subduction zone

Genetic variation of TLR4 influences immunoendocrine stress response: an observational study in cardiac surgical patients

Introduction: Systemic inflammation (e.g. following surgery) involves Toll-like receptor (TLR) signaling and leads to an endocrine stress response. This study aims to investigate a possible influence of TLR2 and TLR4 single nucleotide polymorphisms (SNPs) on perioperative adrenocorticotropic hormone (ACTH) and cortisol regulation in serum of cardiac surgical patients. To investigate the link to systemic inflammation in this context, we additionally measured 10 different cytokines in the serum. Methods: 338 patients admitted for elective cardiac surgery were included in this prospective observational clinical cohort study. Genomic DNA of patients was screened for TLR2 and TLR4 SNPs. Serum concentrations of ACTH, cortisol, interferon (IFN)-, interleukin (IL)-1, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, tumor necrosis factor (TNF)- and granulocyte macro-phage-colony stimulating factor (GM-CSF) were determined before surgery, immediately post surgery and on the first postoperative day. Results: 13 patients were identified as TLR2 SNP carrier, 51 as TLR4 SNP carrier and 274 pa-tients as non-carrier. Basal levels of ACTH, cortisol and cytokines did not differ between groups. In all three groups a significant, transient perioperative rise of cortisol could be ob-served. However, only in the non-carrier group this was accompanied by a significant ACTH rise, TLR4 SNP carriers had significant lower ACTH levels compared to non-carriers ((mean[95% confidence intervals]) non-carriers: 201.9[187.7 to 216.1]pg/ml; TLR4 SNP car-riers: 149.9[118.4 to 181.5]pg/ml; TLR2 SNP carriers: 176.4[110.5 to 242.3]pg/ml). Compared to non-carriers, TLR4 SNP carriers showed significant lower serum IL-8, IL-10 and GM-CSF peaks ((mean[95% confidence intervals]): IL-8: non-carriers: 42.6[36.7 to 48.5]pg/ml, TLR4 SNP carriers: 23.7[10.7 to 36.8]pg/ml; IL-10: non-carriers: 83.8[70.3 to 97.4]pg/ml, TLR4 SNP carriers: 54.2[24.1 to 84.2]pg/ml; GM-CSF: non-carriers: 33.0[27.8 to 38.3]pg/ml, TLR4 SNP carriers: 20.2[8.6 to 31.8]pg/ml). No significant changes over time or between the groups were found for the other cytokines. Conclusions: Regulation of the immunoendocrine stress response during systemic inflamma-tion is influenced by the presence of a TLR4 SNP. Cardiac surgical patients carrying this ge-notype showed decreased serum concentrations of ACTH, IL-8, IL-10 and GM-CSF. This finding might have impact on interpreting previous and designing future trials on diagnosing and modulating immunoendocrine dysregulation (e.g. adrenal insufficiency) during systemic inflammation and sepsis

P and S wave velocity measurements of water-rich sediments from the Nankai Trough, Japan

Acoustic velocities were measured during triaxial deformation tests of silty clay and clayey silt core samples from the Nankai subduction zone (Integrated Ocean Drilling Program Expeditions 315, 316, and 333). We provide a new data set, continuously measured during pressure increase and subsequent axial deformation. A new data processing method was developed using seismic time series analysis. Compressional wave velocities (V-p) range between about 1450 and 2200 m/s, and shear wave velocities (V-s) range between about 150 and 800 m/s. V-p slightly increases with rising effective confining pressure and effective axial stress. Samples from the accretionary prism toe show the highest Vp, while fore-arc slope sediments show lower Vp. Samples from the incoming plate, slightly richer in clay minerals, have the lowest values for V-p. V-s increases with higher effective confining pressures and effective axial stress, irrespective of composition and tectonic setting. Shear and bulk moduli are between 0.2 and 1.3 GPa, and 3.85 and 8.41 GPa, respectively. Elastic moduli of samples from the accretionary prism toe and the footwall of the megasplay fault (1.50 and 3.98 GPa) are higher than those from the hanging wall and incoming plate (0.59 and 0.88 GPa). This allows differentiation between normal and overconsolidated sediments. The data show that in a tectonosedimentary environment of only subtle compositional differences, acoustic properties can be used to differentiate between stronger (accretionary prism toe) and weaker (fore-arc slope, incoming plate) sediments. Especially V-p/V-s ratios may be instrumental in detecting zones of low effective stress and thus high pore fluid pressur

Geotechnical behavior of mudstones from the Shimanto and Boso accretionary complexes, and implications for the Nankai accretionary prism

Triaxial shear tests on mudstone samples from the Shimanto Belt and the Boso accretionary complexes (SW Japan and central Japan) were carried out. Pre-exhumation burial depths in the two paleo-accretionary prisms were up to 9,000 m and about 1,000 m for the Shimanto and the Boso samples, respectively. Three methods were applied: (1) pressure stepping tests at increasing confining pressures between 25 and 65 MPa and pore pressures between 20 and 52 MPa; (2) constant confining pressure tests at 55 and 65 MPa, with stepwise pore pressure decrease from 80% to 50% and 25%, and from 90% to 60% and 30% of the confining pressure; and (3) a cyclic loading test on one sample from Boso (19 cycles to 70-MPa differential stress). After some contraction due to pressurization in the first cycles, the sample showed tendencies to creep rather than to fracture. Effective shear parameters show that angles of internal friction between 30° and 50° are in part quite high in both sample subsets, and ranges of cohesion are between about 2 and 6 MPa (Boso) and 13 and >30 MPa (Shimanto). The mechanical results from these paleo-accretionary prisms are taken to constrain the shear parameters of rocks in the deeper parts of the present Nankai accretionary wedge and forearc. Static friction resembles results from experiments on a wide range of phyllosilicate-quartz-feldspar gouges and shows that the forearc is composed of relatively strong rock. Cohesion increase due to diagenesis and/or very low grade metamorphism is of overriding importance and probably permits stresses of up to 18 MPa to be transmitted to the updip end of the seismogenic zone at depth and 5 to 13 MPa to the backstop of the actively deforming frontal prism

The resonance triplet at E_alpha = 4.5 MeV in the 40Ca(alpha,gamma)44Ti reaction

The 40Ca(alpha,gamma)44Ti reaction is believed to be the main production channel for the radioactive nuclide 44Ti in core-collapse supernovae. Radiation from decaying 44Ti has been observed so far for two supernova remnants, and a precise knowledge of the 44Ti production rate may help improve supernova models. The 40Ca(alpha,gamma)44Ti astrophysical reaction rate is determined by a number of narrow resonances. Here, the resonance triplet at E_alpha = 4497, 4510, and 4523 keV is studied both by activation, using an underground laboratory for the gamma counting, and by in-beam gamma spectrometry. The target properties are determined by elastic recoil detection analysis and by nuclear reactions. The strengths of the three resonances are determined to omega gamma = (0.92+-0.20), (6.2+-0.5), and (1.32+-0.24) eV, respectively, a factor of two more precise than before. The strengths of this resonance triplet may be used in future works as a point of reference. In addition, the present new data directly affect the astrophysical reaction rate at relatively high temperatures, above 3.5 GK.Comment: 12 pages, 11 figures; submitted to Phys. Rev.

Influence of genetic variations in TLR4 and TIRAP/Mal on the course of sepsis and pneumonia and cytokine release: an observational study in three cohorts

Introduction: It has been proposed that individual genetic variation contributes to the course of severe infections and sepsis. Recent studies of single nucleotide polymorphisms (SNPs) within the endotoxin receptor and its signaling system showed an association with the risk of disease development. This study aims to examine the response associated with genetic variations of TLR4, the receptor for bacterial LPS, and a central intracellular signal transducer (TIRAP/Mal) on cytokine release and for susceptibility and course of severe hospital acquired infections in distinct patient populations. Methods: Three intensive care units in tertiary care university hospitals in Greece and Germany participated. 375 and 415 postoperative patients and 159 patients with ventilator associated pneumonia (VAP) were included. TLR4 and TIRAP/Mal polymorphisms in 375 general surgical patients were associated with risk of infection, clinical course and outcome. In two prospective studies, 415 patients following cardiac surgery and 159 patients with newly diagnosed VAP predominantly caused by Gram-negative bacteria were studied for cytokine levels in-vivo and after ex-vivo monocyte stimulation and clinical course. Results: Patients simultaneously carrying polymorphisms in TIRAP/Mal and TLR4 and patients homozygous for the TIRAP/Mal SNP had a significantly higher risk of severe infections after surgery (odds ratio (OR) 5.5; confidence interval (CI): 1.34 - 22.64; P = 0.02 and OR: 7.3; CI: 1.89 - 28.50; P < 0.01 respectively). Additionally we found significantly lower circulating cytokine levels in double-mutant individuals with ventilator associated pneumonia and reduced cytokine production in an ex-vivo monocyte stimulation assay, but this difference was not apparent in TIRAP/Mal-homozygous patients. In cardiac surgery patients without infection, the cytokine release profiles were not changed when comparing different genotypes. Conclusions: Carriers of mutations in sequential components of the TLR signaling system may have an increased risk for severe infections. Patients with this genotype showed a decrease in cytokine release when infected which was not apparent in patients with sterile inflammation following cardiac surgery