From desert to Mediterranean rangelands: will increasing drought and inter-annual rainfall variability affect herbaceous annual primary productivity?     

Carly Golodets  Marcelo Sternberg  Jaime Kigel  Bertrand Boeken  Zalmen Henkin  No’am G. Seligman  Eugene David Ungar 《Climatic change》2013,119(3-4):785-798

Climate change is predicted to alter the rainfall regime in the Eastern Mediterranean Basin: total annual rainfall will decrease, while seasonal and inter-annual variation in rainfall will increase. Such changes in the rainfall regime could potentially lead to large-scale changes in aboveground net primary productivity (ANPP) in the region. We conducted a data-driven evaluation of herbaceous ANPP along an entire regional rainfall gradient, from desert (90 mm MAR [Mean Annual Rainfall]) to Mesic-Mediterranean (780 mm MAR) ecosystems, using the largest database ever collated for herbaceous ANPP in Israel, with the aim of predicting consequences of climate change for rangeland productivity. This research revealed that herbaceous ANPP increases with increasing rainfall along the gradient, but strong dependence on rainfall was only apparent within dry sites. Rain Use Efficiency peaks at mid-gradient in Mediterranean sites without woody vegetation (560 and 610 mm MAR). Inter-annual coefficients of variation in rainfall and herbaceous ANPP decrease along the rainfall gradient up to ca. 500 mm MAR. Climate change is more likely to affect herbaceous ANPP of rangelands in the arid end of the rainfall gradient, requiring adaptation of rangeland management, while ANPP of rangelands in more mesic ecosystems is less responsive to variation in rainfall. We conclude that herbaceous ANPP in most Mediterranean rangelands is less vulnerable to climate change than generally predicted.  相似文献   

The Chicxulub Scientific Drilling Project (CSDP)     

Jaime Urrutia‐Fucugauchi  Joanna Morgan  Dieter Stffler  Philippe Claeys 《Meteoritics & planetary science》2004,39(6):787-790

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Parametric analysis of gravity offshore structures: Part 2     

Jaime Dominguez  Enrique Alarcon 《Applied Ocean Research》1981,3(3):101-104

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Three-dimensional tomographic inversion of the seismic velocity structure of the crust and upper mantle of northwestern Nicaragua     

Domínguez  Jaime  Suárez  Gerardo  Gorbatov  Alexei  Segura  Fabio 《Journal of Seismology》2021,25(6):1427-1439

Journal of Seismology - A three-dimensional tomographic image of the seismic velocity structure in the crust and upper mantle of northwestern Nicaragua was performed using the back-projection...  相似文献   

Stable carbon isotopes (δ<Superscript>13</Superscript>C) of total organic carbon and long-chain <Emphasis Type="Italic">n</Emphasis>-alkanes as proxies for climate and environmental change in a sediment core from Lake Petén-Itzá, Guatemala     

Jennifer L. Mays  Mark Brenner  Jason H. Curtis  Kathryn V. Curtis  David A. Hodell  Alex Correa-Metrio  Jaime Escobar  Andrea L. Dutton  Andrew R. Zimmerman  Thomas P. Guilderson 《Journal of Paleolimnology》2017,57(4):307-319

Sediment core PI-6 from Lake Petén Itzá, Guatemala, possesses an ~85-ka record of climate and environmental change from lowland Central America. Variations in sediment lithology suggest large and abrupt changes in precipitation during the last glacial and deglacial periods, and into the early Holocene. We measured stable carbon isotope ratios of total organic carbon and long-chain n-alkanes from the core, the latter representing a largely allochthonous (terrestrial) source of organic matter, to reveal past shifts in the relative proportion of C₃–C₄ terrestrial biomass. We sought to test whether stable carbon isotope results were consistent with other paleoclimate proxies measured in the PI-6 core, and if extraction and isotope analysis of n-alkanes is warranted. The largest δ¹³C variations are associated with Heinrich Events. Carbon isotope values in sediments deposited during the last glacial maximum indicate moderate precipitation with little fluctuation. The deglacial was a period of pronounced climate variability, e.g. a relatively warm and moist Bølling–Allerød, but a cool and dry Younger Dryas. Arid periods of the deglacial were inferred from samples with high δ¹³C values in total organic carbon, which reflect times of greater proportions of C₄ plants. These inferences are supported by stable isotope measurements on ostracod shells and relative abundance of grass pollen from the same depths in core PI-6. Similar trends in carbon stable isotopes measured on bulk organic carbon and n-alkanes suggest that carbon isotope measures on bulk organic carbon in sediments from this lake are sufficient to infer past climate-driven shifts in local vegetation.  相似文献   

Tectonic implications of the earthquake swarm of 1997 in the Michoacan Triangle, Mexico     

Javier F. Pacheco  Carlos Valds-Gonzlez  Hugo Delgado  Shri K. Singh  F. Ramn Zuiga  Carlos A. Mortera-Gutirrez  Miguel A. Santoyo  Jaime Domínguez  Ricardo Barrn 《Journal of South American Earth Sciences》1999,12(6):73

An earthquake swarm occurred during February and March 1997 in the vicinity of the Tancitaro Volcano, in the southern part of the tectonically complex Michoacan Triangle. A study of these events provides an opportunity to map the active faults in the area and to learn if the orientation and the sense of motion on these faults are consistent with the mapped faults and the alignment of cinder cones in the region. The foci of 230 earthquakes, which could be located, are distributed between 10 and 18 km depth, and show an alignment in, roughly, a NE direction. The focal mechanisms and seismic moments of the 27 best-recorded events were determined by waveform modeling of P and S waves. These mechanisms show two distinct patterns. More than 50% of the solutions are left-lateral strike–slip mechanisms with a normal component. The preferred fault plane strikes NE. Another group of events, probably caused by triggered seismicity on the Chapala–Oaxaca fault zone, shows left-lateral strike–slip mechanisms with a large-thrust component on NW-trending faults. S wave splitting shows 1–2.5% crustal-anisotropy. The direction of the anisotropy coincides with the NE alignment of events, and the preferred nodal plane. This is also the alignment of cinder cones, suggesting that preexisting fractures and cracks are responsible for the seismicity and anisotropic behavior of the crust. The resulting stress orientation, NE compression, is the one expected for the fore-arc region. We conclude that although Michoacan Triangle lies in the Trans-Mexican Volcanic Belt, it does not form part of this stress province where the stress orientation is NS extension.  相似文献   

Formation events of shoreline sand waves on a gravel beach     

Jaime Arriaga  Albert Falqués  Francesca Ribas  Eddie Crews 《Ocean Dynamics》2018,68(6):735-748

Kilometric-scale shoreline sand waves (KSSW) have been observed in the north-east flank of the Dungeness Cuspate Foreland (southeastern coast of the UK). They consist of two bumps separated by embayments with a 350–450-m spacing. We have analysed 36 shoreline surveys of 2-km length using the Discrete Fourier Transformation (DFT), from 2005 to 2016, and seven topographic surveys encompassing the intertidal zone, from 2010 to 2016. The data set shows two clear formation events. In order to test the role of high-angle waves on the KSSW formation, the 10-year wave series is propagated from the wave buoy located at 43 m depth up to a location in front of the undulations at 4 m depth using the SWAN wave model. The dominating SW waves arrive with a very high incidence angle (～ 80°) while the NE waves arrive almost shore normal. The ratio R, which measures the degree of dominance of high-angle waves with respect to low-angle waves, correlates well with the shoreline DFT magnitude values of the observed wavelength undulations. In particular, the highest R values coincide with the formation events. Finally, a linear stability model based on the one-line approximation is applied to the Dungeness profile and the 10-year propagated wave series. It predicts accurately the formation moments, with positive growth rates in the correct order of magnitude for wavelengths similar to the observed ones. All these results confirm that the shoreline undulations in Dungeness are self-organized and that the underlying formation mechanism is the high-angle wave instability. The two detected formation events provide a unique opportunity to validate the existing morphodynamic models that include such instability.  相似文献   

Tsunami hydrodynamic force on a building using a SPH real-scale numerical simulation     

Klapp  Jaime  Areu-Rangel  Omar S.  Cruchaga  Marcela  Aránguiz  Rafael  Bonasia  Rosanna  Godoy  Mauricio J.  Silva-Casarín  Rodolfo 《Natural Hazards》2020,100(1):89-109

Natural Hazards - One of the most important aspects in tsunami studies is the behaviour of the wave when it approaches the coast. Information on physical parameters that characterize waves is often...  相似文献   

Source Characterization and Tsunami Modeling of Submarine Landslides Along the Yucatán Shelf/Campeche Escarpment,Southern Gulf of Mexico     

Jason D. Chaytor  Eric L. Geist  Charles K. Paull  David W. Caress  Roberto Gwiazda  Jaime Urrutia Fucugauchi  Mario Rebolledo Vieyra 《Pure and Applied Geophysics》2016,173(12):4101-4116

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Heating-induced changes in the anisotropy of magnetic susceptibility of impact breccias, Chicxulub Crater (Mexico)     

Jaime Urrutia-Fucugauchi  Margarita Delgadillo-Peralta  Ligia Pérez-Cruz  Miriam Velasco-Villarreal 《Studia Geophysica et Geodaetica》2012,56(3):769-787

Initial results of a thermal treatment study on the anisotropy of magnetic susceptibility (AMS) of impact breccias from Chicxulub crater are used to investigate the nature of the magnetic fabrics. Chicxulub impact breccias are heterogeneous materials, with carbonate, basement and melt clasts within carbonate-rich or melt-rich matrix. Samples studied come from the carbonate-rich basal unit Lower Suevite in the Yaxcopoil-1 borehole impactite sequence (core depth interval: 885?C895 m). The Lower Suevite is characterized by mixed prolate and oblate ellipsoids with shallow to steep principal susceptibility axes, which had been related to emplacement as an excavation flow with ground-surge components during the early cratering stages. Thermal treatment results in changes in the fabrics with a tendency to oblate fabrics. Stepwise thermal treatment up to 700°C reveals different behaviors for the oblate, neutral and prolate fabrics marked by changes in AMS parameters and principal susceptibility axis orientations. A sample with oblate fabrics and vertical minimum axes showed an increase of magnetic susceptibility at high temperatures, indicating formation of secondary magnetite and fabric enhancement. A sample with neutral ellipsoid showed heating-induced changes towards oblate fabrics and vertical minimum susceptibility axes. Samples characterized by prolate ellipsoids with horizontal maximum axes showed no directional changes. In a sample with apparent intermediate or inverse fabrics, vertical maximum axes showed changes to horizontal inclinations, with the intermediate and maximum axes switching positions. Changes induced by stepwise thermal treatment appear useful to characterize the fabrics of impact lithologies. Further investigation of heating-induced effects in mineralogy, grain size and textural changes is, however, required to relate the different behaviors observed after stepwise thermal treatment with the magnetic mineralogy and emplacement mode of the breccias.  相似文献