Assessment of site-effects using acceleration time series. Application to São Sebastião volcanic crater     

Jaime A. Santos  Pedro Chitas  Isabel Lopes  Carlos Sousa Oliveira  Isabel Moitinho de Almeida  João Carlos Nunes 《Soil Dynamics and Earthquake Engineering》2011

The Azores archipelago is located at the North America, Eurasia and Africa triple junction and shows seismicity and volcanism typical of an active plate boundary. Terceira Island has been affected by several damaging earthquakes being the 1980 January 1st event (M=7.2) the strongest in Azores during the last century.  相似文献   

An approach to handling non-Gaussianity of parameters and state variables in ensemble Kalman filtering   总被引：4，自引：0，他引：4  

Haiyan Zhou  J. Jaime Gómez-Hernández 《Advances in water resources》2011,34(7):844-864

The ensemble Kalman filter (EnKF) is a commonly used real-time data assimilation algorithm in various disciplines. Here, the EnKF is applied, in a hydrogeological context, to condition log-conductivity realizations on log-conductivity and transient piezometric head data. In this case, the state vector is made up of log-conductivities and piezometric heads over a discretized aquifer domain, the forecast model is a groundwater flow numerical model, and the transient piezometric head data are sequentially assimilated to update the state vector. It is well known that all Kalman filters perform optimally for linear forecast models and a multiGaussian-distributed state vector. Of the different Kalman filters, the EnKF provides a robust solution to address non-linearities; however, it does not handle well non-Gaussian state-vector distributions. In the standard EnKF, as time passes and more state observations are assimilated, the distributions become closer to Gaussian, even if the initial ones are clearly non-Gaussian. A new method is proposed that transforms the original state vector into a new vector that is univariate Gaussian at all times. Back transforming the vector after the filtering ensures that the initial non-Gaussian univariate distributions of the state-vector components are preserved throughout. The proposed method is based in normal-score transforming each variable for all locations and all time steps. This new method, termed the normal-score ensemble Kalman filter (NS-EnKF), is demonstrated in a synthetic bimodal aquifer resembling a fluvial deposit, and it is compared to the standard EnKF. The proposed method performs better than the standard EnKF in all aspects analyzed (log-conductivity characterization and flow and transport predictions).  相似文献   

Alkenones are common in prairie lakes of interior Canada     

Jaime L. Toney  Peter R. Leavitt 《Organic Geochemistry》2011,42(7):707-712

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Mathematical modeling of the aquatic macrophyte inputs of mid-chain n-alkyl lipids to lake sediments: Implications for interpreting compound specific hydrogen isotopic records   总被引：1，自引：0，他引：1  

Li Gao  Jaime Toney  Yongsong Huang 《Geochimica et cosmochimica acta》2011,75(13):3781-122

We present a systematic study of chain-length distributions and D/H ratios of n-alkyl lipids (both n-alkanes and n-alkanoic acids) in a wide range of terrestrial and aquatic plants around and in Blood Pond, Massachusetts, USA. The primary goal is to establish a model to quantitatively assess the aquatic plant inputs of the mid-chain length n-alkyl lipids to lake sediments and to determine the average hydrogen isotopic ratios of these lipids in different plants. Our results show that middle-chain n-alkyl lipids (C₂₁-C₂₃n-alkanes and C₂₀-C₂₄n-alkanoic acids) are exceptionally abundant in floating and submerged aquatic plants, in contrast to the dominance of long-chain n-alkyl lipids (C₂₇-C₃₁n-alkanes and C₂₆-C₃₂n-alkanoic acids) in other plant types, which are consistent with previously published data from Mountain Kenya and the Tibetan Plateau. Combining available data in different environmental settings allows us to establish statistically robust model distributions of n-alkyl lipids in floating/submerged macrophytes relative to other plant types. Based on the model distributions, we established a multi-source mixing model using a linear algebra approach, in order to quantify the aquatic inputs of mid-chain n-alkyl lipids in lake sediments. The results show that ∼97% of the mid-chain n-alkyl lipids (C₂₃n-alkane and C₂₂n-acid (behenic acid)) in Blood Pond sediments are derived from floating and submerged macrophytes. In addition, D/H ratios of C₂₂n-acid and C₂₃n-alkane in the floating and submerged plants from Blood Pond display relatively narrow ranges of variation (−161 ± 16‰ and −183 ± 18‰, respectively). Our study demonstrates that mid-chain n-alkyl lipids such as C₂₃n-alkane and C₂₂n-acid could be excellent recorders of past lake water isotopic ratios in lakes with abundant floating and submerged macrophyte inputs.  相似文献   

Serphitid wasps in Early Cretaceous amber from Spain (Hymenoptera: Serphitidae)     

Jaime Ortega-Blanco  Xavier Delclòs 《Cretaceous Research》2011,32(2):143-154

The diversity of serphitid wasps (Proctotrupomorpha: Serphitoidea) in Early Cretaceous (Albian) amber from Spain is described. Four new species have been found representing the genera Serphites Brues 1937, Aposerphites Kozlov and Rasnitsyn 1979, and Microserphites Kozlov and Rasnitsyn 1979. From the Peñacerrada I (Moraza) outcrop two species are described as Aposerphites angustus Ortega-Blanco, Delclòs, Peñalver and Engel, new species and Serphites lamiak, new species. A single species was found at the San Just (Teruel) outcrop and is described as S. silban, new species. Another single specimen was found in El Soplao (Cantabria) outcrop, described as Microserphites soplaensis, new species. This last specimen is especially interesting in sharing typical serphitid and mymarommatoid characters, giving additional support to the apparent close relationship of both groups.  相似文献   

Contaminant Spill in a Sandbox with Non-Gaussian Conductivities: Simultaneous Identification by the Restart Normal-Score Ensemble Kalman Filter     

Chen  Zi  Xu  Teng  Gómez-Hernández  J. Jaime  Zanini  Andrea 《Mathematical Geosciences》2021,53(7):1587-1615

Mathematical Geosciences - The joint identification of the parameters defining a contaminant source and the heterogeneous distribution of the hydraulic conductivities of the aquifer where the...  相似文献   

Reconstructing Aragonite Saturation State Based on an Empirical Relationship for Northern California     

Catherine V. Davis  Tessa M. Hill  John L. Largier  Brian Gaylord  Jaime Jahncke 《Estuaries and Coasts》2018,41(7):2056-2069

Ocean acidification is a global phenomenon with highly regional spatial and temporal patterns. In order to address the challenges of future ocean acidification at a regional scale, it is necessary to increase the resolution of spatial and temporal monitoring of the inorganic carbon system beyond what is currently available. One approach is to develop empirical regional models that enable aragonite saturation state to be estimated from existing hydrographic measurements, for which greater spatial coverage and longer time series exist in addition to higher spatial and temporal resolution. We present such a relationship for aragonite saturation state for waters off Northern California based on in situ bottle sampling and instrumental measurements of temperature, salinity, and dissolved oxygen. Application of this relationship to existing datasets (5 to 200 m depth) demonstrates both seasonal and interannual variability in aragonite saturation state. We document a deeper aragonite saturation horizon and higher near surface aragonite saturation state in the summers of 2014 and 2015 (compared with 2010–2013), associated with anomalous warm conditions and decadal scale oscillations. Application of this model to time series data reiterates the direct association between low aragonite saturation state and upwelled waters and highlights the extent to which benthic communities on the Northern California shelf are already exposed to aragonite undersaturated waters.  相似文献   

Oxygen isotope zoning in garnets from Franciscan eclogite blocks: evidence for rock–buffered fluid interaction in the mantle wedge     

Jessica C. Errico  Jaime D. Barnes  Ariel Strickland  John W. Valley 《Contributions to Mineralogy and Petrology》2013,166(4):1161-1176

The oxygen isotope compositions of eclogite and amphibolite garnets from Franciscan Complex high-grade blocks and actinolite rinds encasing the blocks were determined to place constraints on their fluid histories. SIMS oxygen isotope analysis of single garnets from five eclogite blocks from three localities (Ring Mountain, Mount Hamilton, and Jenner Beach) shows an abrupt decrease in the δ¹⁸O value by ~1–3 ‰ from core to rim at a distance of ~120 ± 50 μm from the rim in nine out of the 12 garnets analyzed. In contrast, amphibolite garnets from one block (Ring Mountain) analyzed show a gradual increase in δ¹⁸O value from core to rim, implying a different history from that of the eclogite blocks. Values of δ¹⁸O in eclogite garnet cores range from 5.7 to 11.6 ‰, preserving the composition of the eclogite protolith. The abrupt decrease in the δ¹⁸O values of the garnet rims to values ranging from 3.2 to 11.2 ‰ suggests interaction with a lower δ¹⁸O fluid during the final stages of growth during eclogite facies metamorphism (450–600 °C). We hypothesize that this fluid is sourced from the serpentinized mantle wedge. High Mg, Ni, and Cr contents of actinolite rinds encasing the blocks also support interaction with ultramafic rock. Oxygen isotope thermometry using chlorite and phengite versus actinolite of rinds suggests temperatures of 185–240 °C at Ring Mountain and Mount Hamilton. Rind formation temperatures together with the lower δ¹⁸O garnet rims suggest that the blocks were in contact with ultramafic rock from the end of garnet growth through low-temperature retrogression. We suggest a tectonic model in which oceanic crust is subducted at the initiation of subduction and becomes embedded in the overlying mantle wedge. As subduction continues, metasomatic exchange between high-grade blocks and surrounding ultramafic rock is recorded in low δ¹⁸O garnet rims, and later as temperatures decrease, with rind formation.  相似文献   

Relationship between solar radiation and dimethylsulfide concentrations using in situ data for the pristine region of the southern hemisphere     

Jaime Osorio  Blanca Mendoza  Jorge Zavala-Hidalgo 《Geofísica Internacional》2013,52(4):343-354

The biological processes have been proposed as climate variability contributors. Dimethylsulfide (DMS) is the main biogenic sulfur compound in the atmosphere; it is mainly produced by the marine biosphere and plays an important role in the atmospheric sulfur cycle. Currently it is accepted that terrestrial biota not only adapts to environmental conditions but also influences them through regulations of the chemical composition of the atmosphere. In the present study we used a wavelet method to investigate the relationship between DMS, Low cloud cover (LCC), Ultraviolet Radiation A (UVA), Total Solar Irradiance (TSI) and Sea Surface Temperature (SST) in the so called pristine zone of the Southern Hemisphere. We found that the series analyzed have different periodicities which can be associated with large scale climatic phenomena such as El Niño (ENSO) or the Quasi-Biennial Oscillation (QBO), and/or to solar activity. Our results show an intermittent but sustained DMS-SST correlation and a DMSUVA anti correlation; but DMS-TSI and DMS-LCC show nonlinear relationships. The time-span of the series allow us to study only periodicities shorter than 11 years, then we limit our analysis to the possibility that solar radiation influences the Earth climate in periods shorter than the 11-year solar cycle. Our results also suggest a positive feedback interaction between DMS and solar radiation.  相似文献   

Díaz Viera,M.A., Sahay,N., Coronado,M. and Ortiz Tapia,A. (eds.): Mathematical and Numerical Modeling in Porous Media: Applications in Geosciences     

J. Jaime Gómez-Hernández 《Mathematical Geosciences》2014,46(3):377-380

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