Intra-community implications of implementing multiple tsunami-evacuation zones in Alameda,California     

Jeff Peters  Nathan Wood  Rick Wilson  Kevin Miller 《Natural Hazards》2016,80(2):975-995

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Stock-Specific Movement and Distribution of Juvenile Chinook Salmon, <Emphasis Type="Italic">Oncorhynchus tshawytscha</Emphasis>, in Sandy Beach Surf Zones of Oregon and Washington,USA     

J. R. Marin Jarrin  D. J. Teel  J. A. Miller 《Estuaries and Coasts》2016,39(3):759-766

Sandy beach surf zones serve as alternative nursery habitats for juvenile Chinook salmon (0 age) during their early marine residency, a period considered critical due to high and variable mortality rates. Despite the importance of early marine residence, the extent of juvenile salmon surf zone use and movement along sandy beaches is not well understood. Juvenile Chinook salmon distribution and movement were studied in shallow surf zone habitats by sampling from 2006 to 2010 with a beach seine 11 beaches adjacent and distant to four estuary mouths in Oregon and Washington, USA. The estuary of origin of each juvenile was determined using genetic stock identification methods and coded wire tags. Surf zones sampled were within littoral cells, which are stretches of the coastline bordered by rocky headlands, and included estuaries with and without Chinook salmon populations. Juvenile salmonids were only collected at littoral cells with Chinook-inhabited watersheds. Most juveniles (95 %) were present at sandy beaches adjacent (<500 m from estuary mouth) to their estuary of origin. Few Chinook salmon (5 %) were collected at littoral cells that contained non-natal estuaries. These results indicate that juvenile Chinook salmon inhabiting surf zones mostly use beaches adjacent to their estuaries of origin, but some juveniles may reside in beaches distant from their point of ocean entry.  相似文献   

Long-Term Trends of Nutrients and Phytoplankton in Chesapeake Bay     

L. W. HardingJr.  C. L. Gallegos  E. S. Perry  W. D. Miller  J. E. Adolf  M. E. Mallonee  H. W. Paerl 《Estuaries and Coasts》2016,39(3):664-681

Climate effects on hydrology impart high variability to water-quality properties, including nutrient loadings, concentrations, and phytoplankton biomass as chlorophyll-a (chl-a), in estuarine and coastal ecosystems. Resolving long-term trends of these properties requires that we distinguish climate effects from secular changes reflecting anthropogenic eutrophication. Here, we test the hypothesis that strong climatic contrasts leading to irregular dry and wet periods contribute significantly to interannual variability of mean annual values of water-quality properties using in situ data for Chesapeake Bay. Climate effects are quantified using annual freshwater discharge from the Susquehanna River together with a synoptic climatology for the Chesapeake Bay region based on predominant sea-level pressure patterns. Time series of water-quality properties are analyzed using historical (1945–1983) and recent (1984–2012) data for the bay adjusted for climate effects on hydrology. Contemporary monitoring by the Chesapeake Bay Program (CBP) provides data for a period since mid-1984 that is significantly impacted by anthropogenic eutrophication, while historical data back to 1945 serve as historical context for a period prior to severe impairments. The generalized additive model (GAM) and the generalized additive mixed model (GAMM) are developed for nutrient loadings and concentrations (total nitrogen—TN, nitrate?+?nitrate—NO₂?+?NO₃) at the Susquehanna River and water-quality properties in the bay proper, including dissolved nutrients (NO₂?+?NO₃, orthophosphate—PO₄), chl-a, diffuse light attenuation coefficient (K _D (PAR)), and chl-a/TN. Each statistical model consists of a sum of nonlinear functions to generate flow-adjusted time series and compute long-term trends accounting for climate effects on hydrology. We present results identifying successive periods of (1) eutrophication ca. 1945–1980 characterized by approximately doubled TN and NO₂?+?NO₃ loadings, leading to increased chl-a and associated ecosystem impairments, and (2) modest decreases of TN and NO₂?+?NO₃ loadings from 1981 to 2012, signaling a partial reversal of nutrient over-enrichment. Comparison of our findings with long-term trends of water-quality properties for a variety of estuarine and coastal ecosystems around the world reveals that trends for Chesapeake Bay are weaker than for other systems subject to strenuous management efforts, suggesting that more aggressive actions than those undertaken to date will be required to counter anthropogenic eutrophication of this valuable resource.  相似文献   

A Comparative Analysis of Weights of Evidence,Evidential Belief Functions,and Fuzzy Logic for Mineral Potential Mapping Using Incomplete Data at the Scale of Investigation     

Arianne Ford  John M. Miller  Augusto G. Mol 《Natural Resources Research》2016,25(1):19-33

Large amounts of digital data must be analyzed and integrated to generate mineral potential maps, which can be used for exploration targeting. The quality of the mineral potential maps is dependent on the quality of the data used as inputs, with higher quality inputs producing higher quality outputs. In mineral exploration, particularly in regions with little to no exploration history, datasets are often incomplete at the scale of investigation with data missing due to incomplete mapping or the unavailability of data over certain areas. It is not always clear that datasets are incomplete, and this study examines how mineral potential mapping results may differ in this context. Different methods of mineral potential mapping provide different ways of dealing with analyzing and integrating incomplete data. This study examines the weights of evidence (WofE), evidential belief function and fuzzy logic methods of mineral potential mapping using incomplete data from the Carajás mineral province, Brazil to target for orogenic gold mineralization. Results demonstrate that WofE is the best one able to predict the location of known mineralization within the study area when either complete or unacknowledged incomplete data are used. It is suggested that this is due to the use of Bayes’ rule, which can account for “missing data.” The results indicate the effectiveness of WofE for mineral potential mapping with incomplete data.  相似文献   

Modeling the Population Effects of Hypoxia on Atlantic Croaker (<Emphasis Type="Italic">Micropogonias undulatus</Emphasis>) in the Northwestern Gulf of Mexico: Part 1—Model Description and Idealized Hypoxia     

Kenneth A. Rose  Sean Creekmore  Peter Thomas  J. Kevin Craig  Md Saydur Rahman  Rachael Miller Neilan 《Estuaries and Coasts》2018,41(1):233-254

We developed a spatially explicit, individual-based model to analyze how hypoxia effects on reproduction, growth, and mortality of Atlantic croaker in the northwestern Gulf of Mexico lead to population-level responses. The model follows the hourly growth, mortality, reproduction, and movement of individuals on a 300 × 800 spatial grid of 1-km² cells for 140 years. Chlorophyll-a concentration, water temperature, and dissolved oxygen (DO) were specified daily for each grid cell and repeated for each year of the simulation. A bioenergetics model was used to represent growth, mortality was assumed stage- and age-dependent, and the movement behavior of juveniles and adults was modeled based on temperature and avoidance of low DO. Hypoxia effects were imposed using exposure effect submodels that converted time-varying exposures to low DO to reduced hourly growth, increased hourly mortality, and reduced annual fecundity. Results showed that 100 years of either mild or intermediate hypoxia produced small reductions in population abundance, while repeated severe hypoxia caused a 19% reduction in long-term population abundance. Relatively few individuals were exposed to low DO each hour, but many individuals experienced some exposure. The response was dominated by a 5% average reduction in annual fecundity of individuals. Under conditions of random sequences of mild, intermediate, and severe hypoxia years occurring in proportion to their historical frequency, the model predicted a 10% decrease in the long-term population abundance of croaker. A companion paper substitutes hourly DO values from a three-dimensional water quality model for the idealized hypoxia and results in a more realistic population reduction of about 25%.  相似文献   

Palynology of Triassic–Jurassic boundary sections in northern Switzerland     

Elke Schneebeli-Hermann  Nathan Looser  Peter A. Hochuli  Heinz Furrer  Achim G. Reisdorf  Andreas Wetzel  Stefano M. Bernasconi 《Swiss Journal of Geoscience》2018,111(1-2):99-115

A first palynostratigraphic scheme of Upper Triassic deposits in northern Switzerland was established based on spore-pollen associations and dinoflagellate cyst records from the upper part of the Upper Triassic Klettgau Formation and the lower part of the Lower Jurassic Staffelegg Formation. Drill cores from the Adlerberg region (Basel Tabular Jura) and from Weiach (northern part of Canton Zurich) as well as from an outcrop at the Chilchzimmersattel (Basel Folded Jura) were studied and five informal palynological associations are distinguished. These palynological associations correlate with palynological association of the Central European Epicontinental Basin and the Tethyan realm and provide a stratigraphic framework for the uppermost Triassic sediments in northern Switzerland. Throughout the uppermost Triassic to Jurassic palynological succession a remarkable prominence of Classopollis spp. is observed. Besides Classopollis spp. the three Rhaetian palynological associations A to C from the Upper Triassic Belchen Member include typical Rhaetian spore-pollen and dinoflagellate taxa (e.g., Rhaetipollis germanicus, Geopollis zwolinskae, Rhaetogonyaulax rhaetica, and Dapcodinium priscum). Association B differs from association A in a higher relative abundance of the sporomorph taxa Perinopollenites spp. and the consistent occurrence of Granuloperculatipollis rudis and Ricciisporites tuberculatus. Spore diversity is highest in the late Rhaetian palynological association C and includes Polypodiisporites polymicroforatus. A Rhaetian age for the Belchen Member is confirmed by palynological associations A–C, but there is no record of the latest Rhaetian and the earliest Jurassic. In contrast to the Rhaetian palynological associations the Early Jurassic associations W and D include Pinuspollenites spp., Trachysporites fuscus (in association W), and Ischyosporites variegatus. In the view of the end-Triassic mass extinction and contemporaneous environmental changes the described palynofloral succession represents the pre-extinction phase (associations A and B) including a distinct transgression, the extinction phase (association C) associated with a regression, and the post-extinction phase (association W).  相似文献   

Numerical simulation of lifetime and time-dependent damage for granite by continuous and discontinuous approaches     

Wei Chen  Xiang Li  Heinz Konietzky 《Environmental Earth Sciences》2018,77(16):594

In this study, the time-dependent damage process of granite is investigated utilizing two numerical simulation schemes based on continuous method and discontinuous method. Numerical creep tests are carried out with both simulation schemes and mechanical responses and fracture patterns of rock specimens are analyzed. The calibrated numerical models can successfully reflect the typical creep stages observed in the laboratory. The predicted lifetime is in accordance with the laboratory test data. Comparisons are made between the two simulation schemes. It is found that both schemes have unique features that can promote a genuine reflection of the time-dependent damage process of the brittle rocks.  相似文献   

Composition,Age, and Origin of Cretaceous Granitic Magmatism on the Eastern Chukchi Peninsula     

M.?V.?LuchitskayaEmail author  S.?D.?Sokolov  V.?Pease  E.?Miller  B.?V.?Belyatsky 《Geotectonics》2018,52(3):312-330

New geochronological and isotopic geochemical data are given, which make it possible to recognize two types of granitic rocks on the eastern Chukchi Peninsula. Early Cretaceous Tkachen and Dolina granitic plutons with zircon ages (U–Pb SIMS) of 119–122 and 131–136 Ma are related to the first type. They cut through Devonian–Lower Carboniferous basement rocks and are overlain by the Aptian–Albian Etelkuyum Formation. Basal units of the latter contain fragments of granitic rocks. Late Cretaceous Provideniya and Rumilet granitic plutons, which contain zircons with ages of 94 and 85 Ma (U–Pb SIMS), respectively, belong to the second type. They cut through volcanic–sedimentary rocks of the Etelkuyum and Leurvaam formations pertaining to the Okhotsk–Chukotka Volcanic Belt. In petrographic and geochemical features, the Early Cretaceous granitic rocks of the Tkachen Pluton are commensurable with I-type granites, while Late Cretaceous granite of the Rumilet Pluton is comparable to A₂-type granite. The Sr–Nd isotopic data provide evidence that from the Early Cretaceous Tkachen and Dolina plutons to the Late Cretaceous Provideniya and Rumilet plutons, the degree of crustal assimilation of suprasubduction mantle-derived melts increases up to partial melting of heterogeneous continental crust enriched in rubidium. An unconformity and various degrees of secondary alteration of volcanic–sedimentary rocks have been established in the Okhotsk–Chukotka Volcanic Belt, and this was apparently caused by transition of the tectonic setting from suprasubduction to a transform margin with local extension.  相似文献   

Built environment and agricultural value at risk from Hurricane Irma flooding in Florida (USA)     

Miller  Alexander J.  Arias  Mauricio E.  Alvarez  Sergio 《Natural Hazards》2021,109(2):1327-1348

Natural Hazards - Flooding is the most costly type of natural disaster, as well as the most frequent. To provide risk-based flood insurance, providers must be able to accurately determine an...  相似文献   

Variable hangingwall palaeotransport during Silurian and Devonian thrusting in the western Lachlan Fold Belt: Missing gold lodes,synchronous Melbourne Trough sedimentation and Grampians Group fold interference     

J. McL. Miller  L. J. Dugdale  C. J. L. Wilson 《Australian Journal of Earth Sciences》2013,60(6):901-909

The western margin of the Lachlan Fold Belt contains early ductile and brittle structures that formed during northeast‐southwest and east‐west compression, followed by reactivation related to sinistral wrenching. At Stawell all of these structural features (and the associated gold lodes) are dismembered by a complex array of later northwest‐, north‐ and northeast‐dipping faults. Detailed underground structural analysis has identified northwest‐trending mid‐Devonian thrusts (Tabberabberan) that post‐date Early Devonian plutonism and have a top‐to‐the‐southwest transport. Deformation associated with the initial stages of dismemberment occurred along an earlier array of faults that trend southwest‐northeast (or east‐west) and dip to the northwest (or north). The initial transport of the units in the hangingwall of these fault structures was top‐to‐the‐southeast. ‘Missing’ gold lodes were discovered beneath the Magdala orebody by reconstructing a displacement history that involved a combination of transport vectors (top‐to‐the‐southeast and top‐to‐the‐southwest). Fold interference structures in the adjacent Silurian Grampians Group provide further evidence for at least two almost orthogonal shortening regimes, post the mid‐Silurian. Overprinting relationships, and correlation with synchronous sedimentation in the Melbourne Trough, indicates that the early fault structures are mid‐ to late‐Silurian in age (Ludlow: ca 420–414 Ma). These atypical southeast‐vergent structures have regional extent and separate significant northeast‐southwest shortening that occurred in the mid‐Devonian (‘Tabberabberan orogeny’) and Late Ordovician (‘Benambran orogeny’).  相似文献