Development of large‐scale seismites in Upper Cretaceous fluvial sandstones in a fault‐proximal setting          下载免费PDF全文

Michael C. Wizevich  Edward L. Simpson  Hannah L. Hilbert‐Wolf  Sarah E. Tindall 《Sedimentology》2016,63(6):1719-1738

Large‐scale soft‐sediment deformation structures occur within fluvial sandstone bodies of the Upper Cretaceous Wahweap Formation in the Kaiparowits basin, southern Utah, USA. These structures represent an exceptional example of metre‐scale fault‐proximal, seismogenic load structures in nearly homogenous sandstones. The load structures consist of two types: large‐scale load casts and wedge‐shaped load structures. Large‐scale load casts penetrate up to 4·5 m into the underlying sandstone bed. Wedge‐shaped load structures include metre‐scale, parallel, sub‐vertical features and decimetre‐scale features along the periphery of the large‐scale load casts or other wedge‐shaped load structures. Wedge‐shaped load structures contain well‐developed, medial cataclastic shear deformation bands. All load structures contain pervasive well‐defined millimetre‐thick to centimetre‐thick internal laminae, oriented parallel to the outside form of the load structures and asymptotic to deformation bands. Both types of load structures formed because of an inverted density profile, earthquake‐triggered liquefaction and growth of irregularities (a Rayleigh–Taylor instability) on the sandstone–sandstone erosional contact. The internal laminae and deformation bands formed during deformation and clearly demonstrate polyphase deformation, recording a transition from liquefied to hydroplastic to brittle modes of deformation. Decimetre‐scale wedge‐shaped load structures on the edge of the large‐scale load casts probably formed towards the end of a seismic event after the sediment dewatered and increased the frictional contact of grains enough to impart strength to the sands. Metre‐scale wedge‐shaped load structures were created as the tips of downward foundering sediments were driven into fractures, which widened incrementally with seismic pulsation. With each widening of the fracture, gravity and a suction effect would draw additional sediment into the fracture. Superimposed laminae indicate a secondary syndeformational origin for internal laminae, probably by flow‐generated shearing and vibrofluidization mechanisms. Large‐scale and wedge‐shaped load structures, polyphase deformation and secondary laminae may characterize soft‐sediment deformation in certain fault‐proximal settings.  相似文献   

Searching for Added Value in Simulating Climate Extremes with a High-Resolution Regional Climate Model over Western Canada     

Charles L. Curry  Bárbara Tencer  Kirien Whan  Andrew J. Weaver  Michel Giguère  Edward Wiebe 《大气与海洋》2016,54(4):364-384

We evaluate the capacity of a regional climate model to represent observed extreme temperature and precipitation events and also examine the impact of increased resolution, in an effort to identify added value in this respect. Two climate simulations of western Canada (WCan) were conducted with the Canadian Regional Climate Model (version 4) at 15 (CRCM15) and 45?km (CRCM45) horizontal resolution driven at the lateral boundaries by data from the European Centre for Medium-range Weather Forecasts (ECMWF) 40-year Reanalysis (ERA-40) for the period 1973–1995. The simulations were evaluated using the spline-interpolated dataset ANUSPLIN, a daily observational gridded surface temperature and precipitation product with a nominal resolution of approximately 10?km. We examine a range of climate extremes, comprising the 10th and 90th percentiles of daily maximum (TX) and minimum (TN) temperatures, the 90th percentile of daily precipitation (PR90), and the 27 core Climate Daily Extremes (CLIMDEX) indices.

Both simulations exhibit cold biases compared with observations over WCan, with the bias exacerbated at higher resolution, suggesting little added value for temperature overall. There are instances, however, of regional improvement in the spatial pattern of temperature extremes at the higher resolution of CRCM15 (e.g., the CLIMDEX index for the annual number of days when TX?>?25°C). The high-resolution simulations also reveal similarly localized features in precipitation (e.g., rain shadows) that are not resolved at the 45?km resolution. With regard to precipitation extremes, although both simulations generally display wet biases, CRCM15 features a reduced bias in PR90 in all seasons except winter. This improvement occurs despite the fact that spatial and interannual variability of PR90 in CRCM15 is significantly overestimated relative to both CRCM45 and ANUSPLIN. We posit that these characteristics are the result of demonstrable differences between corresponding topographical datasets used in the gridded observations and CRCM, the resulting errors propagated to physical variables tied to elevation and the beneficial effect of subsequent spatial averaging. Because topographical input is often discordant between simulations and gridded observations, it is argued that a limited form of spatial averaging may contribute added value beyond that which has already been noted in previous studies with respect to small-scale climate variability.  相似文献   

Magma mixing induced by particle settling     

Christian J. Renggli  Sebastian Wiesmaier  Cristina P. De Campos  Kai-Uwe Hess  Donald B. Dingwell 《Contributions to Mineralogy and Petrology》2016,171(11):96

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Seismic hazard mapping and mitigation policy development in the central USA and western China     

Zhenming Wang  Alice M. Orton  Lanmin Wang  Edward W. Woolery 《Natural Hazards》2016,81(1):387-404

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Shrinking of Vann Island,Gulf of Mannar,SE coast of India: assessing the impacts     

M. Jayaprakash  K. Sivakumar  S. Muthusamy  R. R. Krishnamurthy  J. K. Edward Patterson 《Natural Hazards》2016,84(3):1529-1538

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New Joint Editors‐in‐Chief          下载免费PDF全文

Edward A. Williams 《Geostandards and Geoanalytical Research》2016,40(3):309-310

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Converting heterogeneous complex geological models to consistent finite element models: methods,development, and application to deep geothermal reservoir operation     

Bo Wang  Sebastian Bauer 《Environmental Earth Sciences》2016,75(20):1349

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Upward brine migration resulting from pressure increases in a layered subsurface system     

Jens-Olaf Delfs  Johannes Nordbeck  Sebastian Bauer 《Environmental Earth Sciences》2016,75(22):1441

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Quantitative 3D imaging of partially saturated granular materials under uniaxial compression     

Milatz  Marius  Hüsener  Nicole  Andò  Edward  Viggiani  Gioacchino  Grabe  Jürgen 《Acta Geotechnica》2021,16(11):3573-3600

Acta Geotechnica - Gauging the mechanical effect of partial saturation in granular materials is experimentally challenging due to the very low suctions resulting from large pores. To this end, a...  相似文献   

Revised recommended methods for analyzing crater size-frequency distributions          下载免费PDF全文

Stuart J. Robbins  Jamie D. Riggs  Brian P. Weaver  Edward B. Bierhaus  Clark R. Chapman  Michelle R. Kirchoff  Kelsi N. Singer  Lisa R. Gaddis 《Meteoritics & planetary science》2018,53(4):891-931

Impact crater populations help us to understand solar system dynamics, planetary surface histories, and surface modification processes. A single previous effort to standardize how crater data are displayed in graphs, tables, and archives was in a 1978 NASA report by the Crater Analysis Techniques Working Group, published in 1979 in Icarus. The report had a significant lasting effect, but later decades brought major advances in statistical and computer sciences while the crater field has remained fairly stagnant. In this new work, we revisit the fundamental techniques for displaying and analyzing crater population data and demonstrate better statistical methods that can be used. Specifically, we address (1) how crater size-frequency distributions (SFDs) are constructed, (2) how error bars are assigned to SFDs, and (3) how SFDs are fit to power-laws and other models. We show how the new methods yield results similar to those of previous techniques in that the SFDs have familiar shapes but better account for multiple sources of uncertainty. We also recommend graphic, display, and archiving methods that reflect computers’ capabilities and fulfill NASA's current requirements for Data Management Plans.  相似文献