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Sample records for patagonian fjordland seismic

  1. Analysis of Tsunamigenic Coastal Rock Slope Failures Triggered by the 2007 Earthquake in the Chilean Fjordland

    NASA Astrophysics Data System (ADS)

    Sepulveda, S. A.; Serey, A.; Hermanns, R. L.; Redfield, T. F.; Oppikofer, T.; Duhart, P.

    2011-12-01

    The fjordland of the Chilean Patagonia is subject to active tectonics, with large magnitude subduction earthquakes, such as the M 9.5 1960 earthquake, and shallow crustal earthquakes along the regional Liquiñe-Ofqui Fault Zone (LOFZ). One of the latter (M 6.2) struck the Aysen Fjord region (45.5 S) on the 21st of April 2007, triggering dozens of landslides in the epicentral area along the fjord coast and surroundings. The largest rock slides and rock avalanches induced a local tsunami that together with debris flows caused ten fatalities and severely damaged several salmon farms, the most important economic activity of the area. Multi-scale studies of the landslides triggered during the Aysen earthquake have been carried out, including landslide mapping and classification, slope stability back-analyses and structural and geomorphological mapping of the largest failures from field surveys and high-resolution digital surface models created from terrestrial laser scanning. The failures included rock slides, rock avalanches, rock-soil slides, soil slides and debris flows. The largest rock avalanche had a volume of over 20 million cubic metres. The landslides affected steep slopes of intrusive rocks of the North Patagonian batholith covered by a thin layer of volcanic soils, which supports a high forest. The results of geotechnical analyses suggest a site effect due to topographic amplification on the generation of the landslides, with peak ground accelerations that may have reached between about 1.0 and 2.0 g for rock avalanches and between 0.6 and 1.0 g for shallow rock-soil slides, depending on the amount of assumed vertical acceleration and the applied method (limit equilibrium and Newmark). Attenuation relationships for shallow crustal seismicity indicate accelerations below 0.5 g for earthquakes of a similar magnitude and epicentral distances. Detailed field structural analyses of the largest rock avalanche in Punta Cola indicate a key role in the failure

  2. Mohorovicic discontinuity depth analysis beneath North Patagonian Massif

    NASA Astrophysics Data System (ADS)

    Gómez Dacal, M. L.; Tocho, C.; Aragón, E.

    2013-05-01

    The North Patagonian Massif is a 100000 km2, sub-rectangular plateau that stands out 500 to 700 m higher in altitude than the surrounding topography. The creation of this plateau took place during the Oligocene through a sudden uplift without noticeable internal deformation. This quite different mechanical response between the massif and the surrounding back arc, the short time in which this process took place and a regional negative Bouguer anomaly in the massif area, raise the question about the isostatic compensation state of the previously mentioned massif. In the present work, a comparison between different results about the depth of the Mohorovicic discontinuity beneath the North Patagonian Massif and a later analysis is made. It has the objective to analyze the crustal thickness in the area to contribute in the determination of the isostatic balance and the better understanding of the Cenozoic evolution of the mentioned area. The comparison is made between four models; two of these were created with seismic information (Feng et al., 2006 and Bassin et al., 2000), another model with gravity information (Barzaghi et al., 2011) and the last one with a combination of both techniques (Tassara y Etchaurren, 2011). The latter was the result of the adaptation to the work area of a three-dimensional density model made with some additional information, mainly seismic, that constrain the surfaces. The work of restriction and adaptation of this model, the later analysis and comparison with the other three models and the combination of both seismic models to cover the lack of resolution in some areas, is presented here. According the different models, the crustal thickness of the study zone would be between 36 and 45 Km. and thicker than the surrounding areas. These results talk us about a crust thicker than normal and that could behave as a rigid and independent block. Moreover, it can be observed that there are noticeable differences between gravimetric and seismic

  3. Hypoxia in Chilean Patagonian Fjords

    NASA Astrophysics Data System (ADS)

    Silva, Nelson; Vargas, Cristian A.

    2014-12-01

    Chilean Patagonia is one of the largest estuarine systems in the world. It is characterized by a complex geography of approximately 3300 islands, a total surface area of 240,000 km2, and 84,000 km of coast line, including islands, peninsulas, channels, fjords, and sounds. The Chilean Patagonia Interior Sea is filled with a mixture of sea, estuarine, and fresh waters, and is characterized by a two layer vertical general circulation. Dissolved oxygen (DO) conditions in these fjords were analyzed based on historic salinity, dissolved oxygen and nutrient data from 1200 oceanographic stations. Horizontal advection of adjacent well oxygenated Subantarctic Waters (5-6 mL L-1) was the mayor source of DO in the deep layers of the Interior Sea. Incoming DO was consumed by the respiration of autochthonous and allochthonous particulate organic matter, as ocean water flows towards the continental fjord heads, reaching near-hypoxic (2-3 mL L-1) or hypoxic levels (<2 mL L-1). As DO declined nutrient concentrations increased towards the fjord heads (from ∼1.6 μM PO4-3 and ∼16 μM NO3- to ∼2.4 μM PO4-3 and ∼24 μM NO3-). Overall, DO conditions in the Interior Sea were mostly the result of a combination of physical and biogeochemical processes. In all eastern channels and fjords, a low DO zone developed near the fjord heads (<4 mL L-1) as a result of larger allochthonous particulate organic matter inputs transported by local rivers. This enhanced organic matter input to the deep layer increased DO consumption due to respiration and overwhelmed the oxygen supplied by horizontal advection. Out of the 90 Chilean Patagonian gulfs, channels and fjords analyzed, 86 systems were oxic (>2 mL L-1) and four hypoxic (<2 mL L-1), but only at their heads. None were found to be anoxic (0 mL L-1). We found these DO conditions to be permanent features of the Chilean Patagonia Interior Sea.

  4. Cenozoic building and deformational processes in the North Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Orts, Darío L.; Folguera, Andrés; Giménez, Mario; Ruiz, Francisco; Rojas Vera, Emilio A.; Lince Klinger, Federico

    2015-05-01

    The Oligocene to present evolution of the North Patagonian Andes is analyzed linking geological and geophysical data in order to decipher the deformational processes that acted through time and relate them to basin formation processes. Seismic reflection profiles reveal the shallow structure of the retroarc area where contractional structures, associated with Oligocene to early Miocene inverted extensional depocenters, are partially onlapped by early to late Miocene synorogenic deposits. From the construction of five structural cross sections along the retroarc area between 40° and 43°30‧ S, constrained by surface, gravity and seismic data, a shortening gradient is observed along Andean strike. The highest shortening of 18.7 km (15.34%) is determined near 41°30‧ S coincidentally with maximum mean topographic values on the eastern Andean slope, where basement blocks were uplifted in the orogenic front area, and the deepest and broadest synorogenic depocenters were formed towards the foreland. Additionally, eastward shifting of Miocene calc-alkaline rocks occurred at these latitudes, which is interpreted as indicative of a change in the subduction parameters at this time. Deep crustal retroarc structure is evaluated through inversion of gravity models that made possible to infer Moho attenuated zones. These coincide with the occurrence of younger than 5 Ma within-plate volcanics as well as with crustal thermal anomalies suggested by shallowing of the Curie isotherm calculated from magnetic data. Younger volcanism and thermal anomalies are explained by slab steepening since early Pliocene, after a mild-shallow subduction setting in the middle to late Miocene, age of the main compressive event.

  5. The Patagonian toothfish: biology, ecology and fishery.

    PubMed

    Collins, Martin A; Brickle, Paul; Brown, Judith; Belchier, Mark

    2010-01-01

    Patagonian toothfish (Dissostichus eleginoides) is a large notothenioid fish that supports valuable fisheries throughout the Southern Ocean. D. eleginoides are found on the southern shelves and slopes of South America and around the sub-Antarctic islands of the Southern Ocean. Patagonian toothfish are a long-lived species (>50 years), which initially grow rapidly on the shallow shelf areas, before undertaking an ontogenetic migration into deeper water. Although they are active predators and scavengers, there is no evidence of large-scale geographic migrations, and studies using genetics, biochemistry, parasite fauna and tagging indicate a high degree of isolation between populations in the Indian Ocean, South Georgia and the Patagonian Shelf. Patagonian toothfish spawn in deep water (ca. 1000 m) during the austral winter, producing pelagic eggs and larvae. Larvae switch to a demersal habitat at around 100 mm (1-year-old) and inhabit relatively shallow water (<300 m) until 6-7 years of age, when they begin a gradual migration into deeper water. As juveniles in shallow water, toothfish are primarily piscivorous, consuming the most abundant suitably sized local prey. With increasing size and habitat depth, the diet diversifies and includes more scavenging. Toothfish have weakly mineralised skeletons and a high fat content in muscle, which helps neutral buoyancy, but limits swimming capacity. Toothfish generally swim with labriform motion, but are capable of more rapid sub-carangiform swimming when startled. Toothfish were first caught as a by-catch (as juveniles) in shallow trawl fisheries, but following the development of deep water longlining, fisheries rapidly developed throughout the Southern Ocean. The initial rapid expansion of the fishery, which led to a peak of over 40,000 tonnes in reported landings in 1995, was accompanied by problems of bird by-catch and overexploitation as a consequence of illegal, unreported and unregulated fishing (IUU). These problems

  6. Wind chill factor applied to Patagonian climatology

    NASA Astrophysics Data System (ADS)

    Coronato, Fernando R.

    1993-03-01

    The wind cooling effect determines wind chill equivalent-temperatures, which may be rather different to actual temperature. In a windy region such as Patagonia, this difference may reach a magnitude and persistence to become an important bioclimatic element. This paper quantifies the wind cooling effect in Patagonia by the presentation of equivalent isotherms as an adaptation of the usual isotherm maps to the regional bioclimatic environment. It is concluded that due to seasonal variations in wind speed, the annual equivalent temperature range is smaller than the actual temperature range, thus increasing oceanic features, from a thermal viewpoint, of the Patagonian climate.

  7. Deep ventilation process in Patagonian fjord, Chile

    NASA Astrophysics Data System (ADS)

    Pérez-Santos, Iván; Silvan, Nelson; Castillo, Manuel; Mayorga, Nicolas; Schneider, Wolfgang; Montero, Paulina; Daneri, Giovanni; Valle-Levinson, Arnoldo; Pizarro, Oscar; Ramirez, Nadín; Igor, Gabriela; Navarro, Eduardo

    2017-04-01

    The Puyuhuapi Fjord (44.6° S) has previously been reported as one of the hypoxic fjords in Chilean Patagonia (dissolved oxygen -DO below 2 mL L-1). Hydrographic sampling between 1995-2016 confirmed hypoxia below 100 m depth, down to the bottom (250 m). A line of sensors at an oceanographic mooring in Puyuhuapi were deployed to continuously record the temporal-vertical behaviour of water column temperature and salinity from the surface down to 120 m, from February to July 2015. A multi-Parameter water quality sonde was deployed at the bottom of the line, with a DO optical sensor. From February to mid-May, hypoxia was sustained (1.4-1.6 mL L-1). However, from May until the end of June, DO values increased (2.8 mL L-1), exceeding the hypoxia threshold. This was the first event of deep ventilation reported in a Chilean Patagonian Fjord. During this time period, deep water temperatures increased by 1.3 °C, coinciding with the decreased in salinity from 33.6 to 32.8. The main cause of this event was attributed to the arrival of a new volume of mixed oceanic water into the fjord, transported by Modified Subantartic Water, with warm temperatures, lower salinities and slightly higher DO values, given its origin in the surface layer of the outer oceanic region. A new experiment was carried out during January-November, 2016 in order to corroborate the ventilation process and its connection with the adjacent ocean. Temperature, salinity and DO sensors were deployed in the outside fjords region close to the ocean (Melinka Channel) and in Puyuhuapi Fjord, to record the data at very high temporal resolution. The distance between both stations was 150 km. In the oceanic mooring the DO time series collected at 150 m depth showed hypoxia in summer related to the position of the Equatorial Sub-surface water, but from fall DO started to increase registering high values in August and September (4-5 mL/L) when the Subantartic Water arrive. The DO records in Puyuhuapi at 120 m showed a

  8. Space Radar Image of Patagonian Ice Fields

    NASA Image and Video Library

    1999-04-15

    This pair of images illustrates the ability of multi-parameter radar imaging sensors such as the Spaceborne Imaging Radar-C/X-band Synthetic Aperture radar to detect climate-related changes on the Patagonian ice fields in the Andes Mountains of Chile and Argentina. The images show nearly the same area of the south Patagonian ice field as it was imaged during two space shuttle flights in 1994 that were conducted five-and-a-half months apart. The images, centered at 49.0 degrees south latitude and 73.5degrees west longitude, include several large outlet glaciers. The images were acquired by SIR-C/X-SAR on board the space shuttle Endeavour during April and October 1994. The top image was acquired on April 14, 1994, at 10:46 p.m. local time, while the bottom image was acquired on October 5,1994, at 10:57 p.m. local time. Both were acquired during the 77th orbit of the space shuttle. The area shown is approximately 100 kilometers by 58 kilometers (62 miles by 36 miles) with north toward the upper right. The colors in the images were obtained using the following radar channels: red represents the C-band (horizontally transmitted and received); green represents the L-band (horizontally transmitted and received); blue represents the L-band (horizontally transmitted and vertically received). The overall dark tone of the colors in the central portion of the April image indicates that the interior of the ice field is covered with thick wet snow. The outlet glaciers, consisting of rough bare ice, are the brightly colored yellow and purple lobes which terminate at calving fronts into the dark waters of lakes and fiords. During the second mission the temperatures were colder and the corresponding change in snow and ice conditions is readily apparent by comparing the images. The interior of the ice field is brighter because of increased radar return from the dryer snow. The distinct green/orange boundary on the ice field indicates an abrupt change in the structure of the snowcap

  9. The Patagonian icefields: A glaciological review

    SciTech Connect

    Warren, C.R.; Sugden, D.E. )

    1993-11-01

    The Patagonian icefields are the largest mid-latitude ice masses and yet few glaciological data exist for them. The presence of the Andes lying athwart the westerlies makes for a dynamic glacial system with steep balance gradients and west-east equilibrium-line altitude gradients. The overall trend during the 20th century has been glacier retreat. However, whereas most eastern outlets retreated consistently from the beginning of the century, recession on the west began later, has been interrupted by readvances, and most recently has accelerated markedly, reaching higher mean rates of retreat than those on the east. This contrast may result from a predominantly precipitation-controlled mass-balance regime in the west and a dominant temperature control in the east. Superimposed on these contrasts is the anomalous behavior of certain calving glaciers, the oscillations of which contrast in magnitude, timing and sign with each other and with noncalving glaciers, and which in many cases do not relate directly to climate change. Two large calving outlets are at or near their Neoglacial maxima. The tantalizing fragments of information that exist suggest that there is a rich glaciological source to be mined in Patagonia yielding insights into glacioclimatic interactions, calving dynamics, Holocene climate change and the role of topography in controlling glacier behavior. 118 refs., 13 figs., 2 tabs.

  10. Tertiary tectonics of the sub-Andean region of the North Patagonian Andes, southern central Andes of Argentina (41 42°30‧S)

    NASA Astrophysics Data System (ADS)

    Giacosa, Raúl E.; Afonso, Juan C.; Heredia C., Nemesio; Paredes, José

    2005-12-01

    The sub-Andean region of the North Patagonian Andes is located between the north Patagonian foreland and the highest elevations of the Andean Cordillera. Its Tertiary contractional structure, active since the upper Late Oligocene and through the upper Late Miocene, corresponds to the external sector of the North Patagonian Andes fold-and-thrust belt, which is characterized by east-vergent thrusts that affect stratified Cenozoic rocks. The units involved in the deformation correspond to El Maitén Oligocene volcanic belt, deformed between east-vergent thrusts and backthrusts, and Oligocene-Miocene sedimentary rocks of the Ñirihuau-Collón Curá Basin. The northern sector of the basin was structured as a thin-skinned fold belt that comprises the Ñirihuau fold belt and a frontal sedimentary wedge. To the south, sedimentary depocenters are confined between medium- to high-angle reverse faults with evidence of basement structural control. In both cases, the general tectonosedimentary framework shows the youngest units toward the east, in agreement with the advance of the orogenic wedge. Most of the Ñirihuau-Collón Curá Basin infill fits a foreland basin system model. Some sectors of the basin show evidence of structural control by normal faults in the initial sedimentation stages. This early extensional regime might be associated with late phases of Oligocene volcanism. Extensional structures probably were partially reactivated during the upper Late Oligocene, as suggested by seismic data.

  11. Proteolytic activity in some Patagonian plants from Argentina.

    PubMed

    Sequeiros, Cynthia; López, Laura M I; Caffini, Néstor O; Natalucci, Claudia L

    2003-09-01

    Six Patagonian plants were screened for proteolytic activity: Colliguaja integerrima, Euphorbia collina, E. peplus and Stillingia patagonica (Euphorbiaceae), Philibertia gilliesii (Asclepiadaceae) and Grindelia chiloensis (Asteraceae). P. gilliesii extracts showed the highest specific activity, followed by S. patagonica and E. collina. Proteolytic activity was unnoticeable in the other three species studied. Inhibition assays revealed that P. gilliesii and S. patagonica extracts contain cysteine-type peptidases and that in E. collina serine-type peptidases are present.

  12. Synoptic events force biological productivity in Patagonian fjord ecosystems

    NASA Astrophysics Data System (ADS)

    Daneri, Giovanni

    2016-04-01

    The annual cycle of primary productivity of the Patagonian fjords has, to date, been described as a two phase system consisting of a short non productive winter phase (during June and July) and a productive phase extending from late winter (August) to autumn (May). Low levels of primary production, phytoplankton biomass and high concentrations of surface nutrients have been described as characterizing winter conditions while pulsed productivity events typifies the productivity pattern during the extended productive season. Pulsed productivity events characterize coastal waters where inorganic nutrients in surface layers are replenished following periods of intensive utilization by autotrophs. Freshwater input in Patagonian fjords in southern Chile (41-55°S) results in one of the largest estuarine regions worldwide. Here strong haline water column stratification prevents nutrient mixing to the surface layers thus potentially shutting off algal production. Our working hypothesis considered that in order to reconcile the observed pulsed productivity pattern, periodic breaking (associated to surface nutrient replenishment) and re-establishment of estuarine conditions (associated to water column stratification) would be required. Up to now however our understanding of the physical processes that control water column conditions in the Patagonian fjord area has been extremely limited. Here we present evidence linking the passage of synoptic low pressure fronts to pulsed productivity events in the Patagonian fjord area. These front controls and influence local processes of interaction between the fjord and the atmosphere generating a rapid water column response. In the specific case of the Puyuhuapi fjord we have been able to show that such synoptic fronts induce surface flow reversal and water column mixing. Phytoplankton blooming occurs after the passage of the synoptic front once calmer conditions prevail and estuarine conditions are re established. The occurrence of

  13. Disentangling natural and anthropogenic influences on Patagonian pond water quality.

    PubMed

    Epele, Luis B; Manzo, Luz M; Grech, Marta G; Macchi, Pablo; Claverie, Alfredo Ñ; Lagomarsino, Leonardo; Miserendino, M Laura

    2017-09-20

    The water quality of wetlands is governed not only by natural variability in hydrology and other factors, but also by anthropogenic activities. Patagonia is a vast sparsely-populated in which ponds are a key component of rural and urban landscapes because they provide several ecosystem services such as habitat for wildlife and watering for livestock. Integrating field-based and geospatial data of 109 ponds sampled across the region, we identified spatial trends and assessed the effects of anthropogenic and natural factors in pond water quality. The studied ponds were generally shallow, well oxygenated, with maximum nutrient values reported in sites used for livestock breeding. TN:TP ratio values were lower than 14 in >90% of the ponds, indicating nitrogen limitation. Water conductivity decreased from de east to the west, meanwhile pH and dissolved oxygen varied associated with the latitude. To assess Patagonian ponds water status we recommend the measure of total suspended solids and total nitrogen in the water, and evaluate the mallín (wetland vegetation) coverage in a 100m radius from the pond, since those features were significantly influenced by livestock land use. To evaluate the relative importance of natural variability and anthropogenic influences as driving factors of water quality we performed three generalized linear models (GLM) that encompassed the hydrology, hydroperiod and biome (to represent natural influences), and land use (to represent anthropogenic influences) as fixed effects. Our results revealed that at the Patagonian scale, ponds water quality would be strongly dependent on natural gradients. We synthetized spatial patterns of Patagonian pond water quality, and disentangled natural and anthropic factors finding that the dominant environmental influence is rainfall gradient. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Zoonotic parasites associated with felines from the Patagonian Holocene.

    PubMed

    Fugassa, Martín Horacio; Beltrame, María Ornela; Bayer, María S; Sardella, Norma Haydée

    2009-12-01

    Feline coprolites were examined for parasites with the aim of studying ancient infections that occurred in the Patagonian region during the Holocene period. Eggs compatible to Trichuris sp., Calodium sp., Eucoleus sp., Nematodirus sp., Oesophagostomum sp. (Nematoda), Monoecocestus sp. (Cestoda) and Eimeria macusaniensis (Coccidia) were recovered from faecal samples. The results obtained from the analysis provide evidence of consumption by felids of the viscera of both rodents and camelids. This knowledge allows for improved explanations as to the distribution of parasitism and its significance to the health of humans and animals inhabiting the area under study during the Middle Holocene.

  15. Patagonian and southern South Atlantic view of Holocene climate

    NASA Astrophysics Data System (ADS)

    Kaplan, M. R.; Schaefer, J. M.; Strelin, J. A.; Denton, G. H.; Anderson, R. F.; Vandergoes, M. J.; Finkel, R. C.; Schwartz, R.; Travis, S. G.; Garcia, J. L.; Martini, M. A.; Nielsen, S. H. H.

    2016-06-01

    We present a comprehensive 10Be chronology for Holocene moraines in the Lago Argentino basin, on the east side of the South Patagonian Icefield. We focus on three different areas, where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change. The 10Be dated records are from the Lago Pearson, Herminita Península-Brazo Upsala, and Lago Frías areas, which span a distance of almost 100 km adjacent to the modern Icefield. New 10Be ages show that expanded glaciers and moraine building events occurred at least at 6120 ± 390 (n = 13), 4450 ± 220 (n = 7), 1450 or 1410 ± 110 (n = 18), 360 ± 30 (n = 5), and 240 ± 20 (n = 8) years ago. Furthermore, other less well-dated glacier expansions of the Upsala Glacier occurred between 1400 and ∼1000 and ∼2300 and ∼2000 years ago. The most extensive glaciers occurred over the interval from ∼6100 to ∼4500 years ago, and their margins over the last ∼600 years were well within and lower than those in the middle Holocene. The 10Be ages agree with 14C-limiting data for the glacier histories in this area. We then link southern South American, adjacent South Atlantic, and other Southern Hemisphere records to elucidate broader regional patterns of climate and their possible causes. In the early Holocene, a far southward position of the westerly winds fostered warmth, small Patagonian glaciers, and reduced sea ice coverage over the South Atlantic. Although we infer a pronounced southward displacement of the westerlies during the early Holocene, these conditions did not occur throughout the southern mid-high latitudes, an important exception being over the southwest Pacific sector. Subsequently, a northward locus and/or expansion of the winds over the Patagonia-South Atlantic sector promoted the largest glaciers between ∼6100 and ∼4500 years ago and greatest sea ice coverage. Over the last few millennia, the South Patagonian Icefield has experienced

  16. Pharmacokinetics after intravenous administration of flunixin meglumine in budgerigars (Melopsittacus undulatus) and Patagonian conures (Cyanoliseus patagonus).

    PubMed

    Musser, Jeffrey M B; Heatley, J Jill; Phalen, David N

    2013-01-15

    To investigate the disposition kinetics of flunixin meglumine when administered IV to budgerigars (Melopsittacus undulatus) and Patagonian conures (Cyanoliseus patagonus). Prospective cohort study. 8 adult Patagonian conures and 24 adult budgerigars. Injectable flunixin meglumine (50 mg/mL) was diluted to 10 and 1. 0 mg/mL and administered IV at a dose of 5.0 mg/kg (2.3 mg/lb) to Patagonian conures and budgerigars, respectively. In budgerigars, the elimination half-life was 0.72 hours and the mean residence time was 0.73 hours. In Patagonian conures, the elimination half-life was 0.91 hours and the mean residence time was 1.20 hours. The concentration of flunixin was below the assay's limit of quantification (0.5 μg/mL) at 3 and 6 hours in budgerigars and Patagonian conures, respectively. A single budgerigar developed adverse effects (lethargy and signs of depression) for approximately 15 minutes following drug administration. The half-life of flunixin in Patagonian conures and budgerigars was short following IV administration; however, results of this study suggested that IV administration of injectable flunixin meglumine at 5.0 mg/kg resulted in plasma concentrations that could potentially be anti-inflammatory and analgesic in budgerigars and Patagonian conures.

  17. Lithospheric 3D gravity modelling using upper-mantle density constraints: Towards a characterization of the crustal configuration in the North Patagonian Massif area, Argentina

    NASA Astrophysics Data System (ADS)

    Gómez Dacal, María Laura; Tocho, Claudia; Aragón, Eugenio; Sippel, Judith; Scheck-Wenderoth, Magdalena; Ponce, Alexis

    2017-03-01

    The North Patagonian Massif is an Argentinean plateau that has an average height of 1200 m and stands from 500 to 700 m above the neighboring areas. During Paleogene, it suffered a sudden uplift of more than 1200 m without noticeable internal deformation; thus, it could be related to isostatic disequilibrium. To shed light on the geodynamic development of the area it is necessary to characterize the present-day configuration of the crust. In this study, a lithospheric-scale 3D density model was developed by integrating all the available data of the area with the objective of assessing the depth of the crust-mantle discontinuity (Moho). During the construction of the initial density model, we tested different mantle density scenarios obtained using P- and S-wave velocities from tomographic models, converting them into densities and comparing the conversions with densities obtained from xenoliths. Below the North Patagonian Massif plateau, we have derived a Moho depth between 40 and 50 km which is from 2 to 7 km deeper than its surroundings. There is an evident correlation between high topography and deep Moho that would indicate isostatic equilibrium at present. The model results provide a new approach to the Moho depth in an area where there is no seismic constraining information about this discontinuity. In addition, we found a spatial correlation between the variation of the mean crustal density and the location of the Paleozoic terranes that were proposed to constitute the basement of Argentina.

  18. Patagonian Glacier Response During the Late Glacial Holocene Transition

    NASA Astrophysics Data System (ADS)

    Ackert, Robert P.; Becker, Richard A.; Singer, Brad S.; Kurz, Mark D.; Caffee, Marc W.; Mickelson, David M.

    2008-07-01

    Whether cooling occurred in the Southern Hemisphere during the Younger Dryas (YD) is key to understanding mechanisms of millennial climate change. Although Southern Hemisphere records do not reveal a distinct climate reversal during the late glacial period, many mountain glaciers readvanced. We show that the Puerto Bandera moraine (50°S), which records a readvance of the Southern Patagonian Icefield (SPI), formed at, or shortly after, the end of the YD. The exposure age (10.8 ± 0.5 thousand years ago) is contemporaneous with the highest shoreline of Lago Cardiel (49°S), which records peak precipitation east of the Andes since 13 thousand years ago. Absent similar moraines west of the Andes, these data indicate an SPI response to increased amounts of easterly-sourced precipitation—reflecting changes in the Southern Westerly circulation—rather than regional cooling.

  19. Patagonian wines: the selection of an indigenous yeast starter.

    PubMed

    Lopes, Christian A; Rodríguez, María E; Sangorrín, Marcela; Querol, Amparo; Caballero, Adriana C

    2007-08-01

    The use of selected yeasts for winemaking has clear advantages over the traditional spontaneous fermentation. The aim of this study was to select an indigenous Saccharomyces cerevisiae yeast isolate in order to develop a regional North Patagonian red wine starter culture. A two-step selection protocol developed according to physiological, technological and ecological criteria based on killer interactions was used. Following this methodology, S. cerevisiae isolate MMf9 was selected among 32 indigenous yeasts previously characterized as belonging to different strains according to molecular patterns and killer biotype. This isolate showed interesting technological and qualitative features including high fermentative power and low volatile acidity production, low foam and low sulphide production, as well as relevant ecological characteristics such as resistance to all indigenous and commercial S. cerevisiae killer strains assayed. Red wines with differential volatile profiles and interesting enological features were obtained at laboratory scale by using this selected indigenous strain.

  20. Patagonian glacier response during the late glacial-Holocene transition.

    PubMed

    Ackert, Robert P; Becker, Richard A; Singer, Brad S; Kurz, Mark D; Caffee, Marc W; Mickelson, David M

    2008-07-18

    Whether cooling occurred in the Southern Hemisphere during the Younger Dryas (YD) is key to understanding mechanisms of millennial climate change. Although Southern Hemisphere records do not reveal a distinct climate reversal during the late glacial period, many mountain glaciers readvanced. We show that the Puerto Bandera moraine (50 degrees S), which records a readvance of the Southern Patagonian Icefield (SPI), formed at, or shortly after, the end of the YD. The exposure age (10.8 +/- 0.5 thousand years ago) is contemporaneous with the highest shoreline of Lago Cardiel (49 degrees S), which records peak precipitation east of the Andes since 13 thousand years ago. Absent similar moraines west of the Andes, these data indicate an SPI response to increased amounts of easterly-sourced precipitation-reflecting changes in the Southern Westerly circulation-rather than regional cooling.

  1. Corynebacterium pseudotuberculosis Infection in Patagonian Huemul ( Hippocamelus bisulcus ).

    PubMed

    Morales, Nelly; Aldridge, Dennis; Bahamonde, Andrea; Cerda, Julio; Araya, Claudio; Muñoz, Rodrigo; Saldías, María Esther; Lecocq, Claudio; Fresno, Marcela; Abalos, Pedro; Retamal, Patricio

    2017-07-01

    Corynebacterium pseudotuberculosis is an intracellular bacteria and the etiologic agent of caseous lymphadenitis in domestic and wildlife species. We report C. pseudotuberculosis infection in Patagonian huemul ( Hippocamelus bisulcus ) from the Cerro Castillo National Reserve, Region of Aysen, Chile. Subcutaneous abscesses in the abdominal and pectoral regions from two animals were sampled and bacteriologic isolation was performed. In both cases, we isolated a C. pseudotuberculosis strain belonging to the ovine genotype. In addition, one isolate was resistant to ciprofloxacin and streptomycin. We report that H. bisulcus is a susceptible species to this bacterium, which is transmitted by direct or indirect contact with domestic sheep ( Ovis aries ) and which represents a potential conservation threat to populations of H. bisulcus . Additional research and prevention efforts should be addressed.

  2. Complex brittle deformation pattern along the Southern Patagonian Andes (Argentina)

    NASA Astrophysics Data System (ADS)

    Barberón, Vanesa; Sue, Christian; Ronda, Gonzalo; Ghiglione, Matías

    2016-04-01

    The Southern Patagonian Andes is located in the southern extreme of the Pacific subduction zone, where the Antartic oceanic plate sinks underneath South America. The history of the area begins with compression during Paleozoic, Jurassic extension associated to the rift and opening of the South Atlantic Ocean, then a sag stage in the Lower Cretaceous followed by a foreland phase as a result of plate tectonics (Ghiglione et al., 2016). The kinematic study is concentrated in the Argentinean foothills, between 46°40' and 48° SL. We measured around 800 fault planes and their striaes with the sense of movement in order to characterize the stress field. The software used to make the stress inversion were Tensor (Delvaux, 2011) and Multiple Inverse Method MIM (Yamaji et al., 2011). The stress field map was built with the results of the MIM. We present new data from 48 sites located in the northern sector of the Southern Patagonian Andes. The measurements were made in several rocks from Paleozoic to Lower Cretaceous, even though most were taken in pyroclastic jurassic rocks from El Quemado Complex. Paleostress tensors obtained are mostly strike-slip, although a 25% is normal and there are a few compresional. The pattern of faults found is complex. In some sites the tensor can be locally linked to satellite images and observations from the field or be related to a major thrust front. There is no clear correlation between the age and/or lithology with the tensor since the youngest rocks measured are Lower Cretaceous. Probably there are several generations of family faults connected to different and recent tectonic phases then the paleostress tensors might correspond to the latest tectonic events.

  3. Upper trophic structure in the Atlantic Patagonian shelf break as inferred from stable isotope analysis

    NASA Astrophysics Data System (ADS)

    Zhu, Guoping; Zhang, Haiting; Yang, Yang; Wang, Shaoqin; Wei, Lian; Yang, Qingyuan

    2017-09-01

    The Patagonian Shelf is a very productive region with different ecosystem structures. A long history of fishing in the Southwestern Atlantic Ocean combined with a complex hydrographic structure, with a permanent front over the shelf-break and different coastal frontal regions, and a wide non-frontal area in between have made the food web in this area more complex and have resulted in changes to the spatial-temporal scale. Stable isotopes of carbon and nitrogen were used to determine the trophic structure of the Patagonian shelf break which was previously poorly understood. The results indicated that the average δ15N value of pelagic guild (Illex argentinus) was remarkable lower than those of the other guilds. The δ13C values of almost all species ranged from -17‰ to -18‰, but Stromateus brasiliensis had a significant lower δ13C value. Compared with the southern Patagonian shelf, short food chain length also occurred. The impact of complex oceanographic structures has resulted in food web structure change to the temporal-spatial scale on the Patagonian shelf. The Patagonian shelf break can be considered as a separated ecosystem structure with lower δ15N values.

  4. Baroclinic annular variability of internal motions in a Patagonian fjord

    NASA Astrophysics Data System (ADS)

    Ross, Lauren; Valle-Levinson, Arnoldo; Pérez-Santos, Iván.; Tapia, Fabian J.; Schneider, Wolfgang

    2015-08-01

    Time series of horizontal velocities, echo intensity, wind velocity, and atmospheric pressure were collected for ˜200 days in a Patagonian fjord to explore pycnocline motions produced by the Southern Hemisphere's baroclinic annular mode (BAM). The BAM variability occurs between 20 and 30 days and is associated with fluctuations in atmospheric kinetic energy and in turbulent fluxes of heat. Spectra of horizontal velocities and normalized echo intensity in the fjord's water showed highest energy between 25 and 30 days. This was explained by sustained westerly winds associated with extreme low-pressure systems (˜900 hPa) that had periodicity related to the BAM. Wind forcing produced >40 cm s-1 along-channel and cross-channel currents in the surface layer, which in turn created a wind-induced setup toward the head of the fjord. The setup was accompanied by a deepening of the pycnocline (from 5 to 15 m depth) with ˜25 to 30 day periodicity, as derived from the normalized echo intensity. The dominant empirical orthogonal function mode of the normalized echo intensity profiles explained 70.8% of the variance and also exhibited a ˜25-30 day periodicity. Further, a wavelet and spectral analysis of 10 years of atmospheric pressure indicated peaks between 25 and 30 days each year, indicating that the BAM consistently influences weather patterns in Chilean Patagonia. This is the first documented case of baroclinic annular variability in a specific region of the Southern Hemisphere, and of its effects on fjord systems.

  5. Whole-Community Facilitation Regulates Biodiversity on Patagonian Rocky Shores

    PubMed Central

    Silliman, Brian R.; Bertness, Mark D.; Altieri, Andrew H.; Griffin, John N.; Bazterrica, M. Cielo; Hidalgo, Fernando J.; Crain, Caitlin M.; Reyna, Maria V.

    2011-01-01

    Background Understanding the factors that generate and maintain biodiversity is a central goal in ecology. While positive species interactions (i.e., facilitation) have historically been underemphasized in ecological research, they are increasingly recognized as playing important roles in the evolution and maintenance of biodiversity. Dominant habitat-forming species (foundation species) buffer environmental conditions and can therefore facilitate myriad associated species. Theory predicts that facilitation will be the dominant community-structuring force under harsh environmental conditions, where organisms depend on shelter for survival and predation is diminished. Wind-swept, arid Patagonian rocky shores are one of the most desiccating intertidal rocky shores ever studied, providing an opportunity to test this theory and elucidate the context-dependency of facilitation. Methodology/Principal Findings Surveys across 2100 km of southern Argentinean coastline and experimental manipulations both supported theoretical predictions, with 43 out of 46 species in the animal assemblage obligated to living within the matrices of mussels for protection from potentially lethal desiccation stress and predators having no detectable impact on diversity. Conclusions/Significance These results provide the first experimental support of long-standing theoretical predictions and reveal that in extreme climates, maintenance of whole-community diversity can be maintained by positive interactions that ameliorate physical stress. These findings have important conservation implications and emphasize that preserving foundation species should be a priority in remediating the biodiversity consequences of global climate change. PMID:22022356

  6. Infection of Myxobolus galaxii (Myxozoa) in Galaxias maculatus (Osmeriformes: Galaxiidae) from northwestern Patagonian Andean lakes (Argentina).

    PubMed

    Flores, Verónica; Viozzi, Gustavo

    2007-04-01

    The infection of Myxobolus galaxii Szidat, 1953, from the musculature and abdominal organs of northwestern Patagonian Galaxias maculatus is described. Plasmodia are histozoic and intercellular. Spores are pyriform in valvar view and biconvex in sutural view, with 4-9 edge notches in the sutural line, varying in shape within the same plasmodium. Myxobolus galaxii was detected in fish from 7 of 17 Andean Patagonian lakes, with prevalences ranging between 2 and 17%. A repeating pattern of summer increment in prevalence was observed, which could be explained by the ontogenetic migratory movements of the fish in Lake Gutiérrez. Also, accumulation of plasmodia through the life span of fish was detected.

  7. Tidal dynamics on the North Patagonian Argentinean Gulfs

    NASA Astrophysics Data System (ADS)

    Tonini, Mariano H.; Palma, Elbio D.

    2017-04-01

    Semidiurnal (M2, S2, N2 and K2), diurnal (K1,O1 and P1) and quarter-diurnal (M4, MN4 and MS4) barotropic tides over the North Patagonian Gulfs of Argentina: San Matías, (SMG), Nuevo (NG) and San José (SJG) are examined using a regional numerical model. Detailed comparison of computed elevations and currents with those obtained from harmonic analysis of few long-term observational records showed good agreement. A large amplification of all semidiurnal waves is recorded when they cross SMG mouth. Most of the tidal energy coming from the south at this frequency dissipates to the northeast of Valdés Península, where the largest tidal currents are located. While M2 currents (up to 2-2.5 m/s) are dominant, there are large S2 and N2 currents and locally intensified diurnal currents (5-10 cm/s) in some outer shelf locations. At difference with the semidiurnal and diurnal tides the higher harmonics M4, MS4 and MN4 develop a large amplification inside the NG. The model revealed a complex field of tidal residual currents. The intensity of such currents in some locations are of the same order of magnitude as those generated by winds or offshore forcing. We have identified three main patterns of residual circulation: regional coastal currents and gulf-wide gyres; inlet eddies and, topographic eddies. Vorticity balances and sensitivity experiments indicate that non-linear advection and bottom topography are the key mechanisms involved in the generation of these residual structures.

  8. Effects of recreational activities on Patagonian rocky shores.

    PubMed

    Mendez, María M; Livore, Juan P; Calcagno, Javier A; Bigatti, Gregorio

    2017-09-01

    Recreational activities can be an important source of anthropogenic disturbance in intertidal benthic assemblages. On rocky shores, activities such as trampling, snorkeling and the handling of organisms may have a negative effect on benthic communities by modifying the abundance and distribution of key species. Here, we describe and quantify impacts due to recreational activities on benthic communities on a Patagonian rocky shore by investigating their resilience to two types of human disturbance: vehicle traffic and human trampling. To evaluate the effects of these activities, we carried out an observational study and assessed post-disturbance assemblage recovery. The rocky shores is most intensively visited during summer, and marked differences in the distribution and abundance of benthic species among disturbed and control plots were found after this season. The benthic community on the high intertidal was weakly impacted by disturbance generated due to vehicle traffic in summer (one vehicle on a single occasion, pulse disturbance); which did not affect the cover of dominant species. This suggests that the high intertidal community would be resistant to the passage of one vehicle on a single occasion. The effects of continuous trampling (press disturbance) were drastic and the community of the mid intertidal level did not recover before the next recreational season. Mid intertidal communities exposed to press disturbances require more than one tourist season of human inactivity to recover from anthropogenic effects, suggesting that resilience mechanisms in this community operate at broad timescales. Our findings highlight the need to establish and implement management actions that contemplate the nature of the disturbance and intertidal level to minimize habitat degradation due to human recreational activities. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Seismic Methods

    EPA Pesticide Factsheets

    Seismic methods are the most commonly conducted geophysical surveys for engineering investigations. Seismic refraction provides engineers and geologists with the most basic of geologic data via simple procedures with common equipment.

  10. Lichenometric dating using Rhizocarpon subgenus Rhizocarpon in the Patagonian Andes, Argentina

    NASA Astrophysics Data System (ADS)

    Garibotti, Irene Adriana; Villalba, Ricardo

    2009-05-01

    This study represents the first attempt to develop and apply lichenometric dating curves of Rhizocarpon subgenus Rhizocarpon for dating glacier fluctuations in the Patagonian Andes. Six glaciers were studied along the Patagonian Andes. Surfaces of known ages (historical evidences and tree-ring analyses) were used as control sites to develop indirect lichenometric dating curves. Dating curves developed for the studied glaciers show the same general logarithmic form, indicating that growth rate of subgenus Rhizocarpon decreases over time. The strong west-east precipitation gradient across the Andean Cordillera introduces statistically significant differences in the growth curves, with faster growth rates in the moist west sites than the drier eastern sites. Latitudinal difference among the studied glaciers does not appear to be a major factor regulating lichen growth rates. Therefore, we developed two lichenometric curves for dating glacier fluctuations in wetter and drier sites in the Patagonian Andes during the past 450 yrs. Application of the developed curves to moraine dating allowed us to complement glacial chronologies previously obtained by tree-ring analyses. A first chronosequence for moraine formation in the Torrecillas Glacier (42°S) is presented. Our findings confirm the utility of lichenometry to date deglaciated surfaces in the Patagonian Andes.

  11. Genetic attributes of 15 autosomal STRs in the population of two patagonian provinces of Argentina.

    PubMed

    Marino, Miguel; Sala, Andrea; Corach, Daniel

    2006-06-27

    Allele frequencies of 15 short tandem repeats (STRs) loci included in the PowerPlex 16 kit (Promega Corp., Madison, WI, USA) were obtained from a sample set of unrelated individuals inhabiting Rio Negro (N=593) and Chubut (N=320) provinces of the Argentinean Patagonia. Comparative analyses between our population data and other Patagonian Province (Neuquen) are presented.

  12. Soil water availability and rooting depth as determinants of hydraulic architecture of Patagonian woody species

    Treesearch

    Sandra J. Bucci; Fabian G. Scholz; Guillermo Goldstein; Frederick C. Meinzer; Maria E. Arce

    2009-01-01

    We studied the water economy of nine woody species differing in rooting depth in a Patagonian shrub steppe from southern Argentina to understand how soil water availability and rooting depth determine their hydraulic architecture. Soil water content and potentials, leaf water potentials (Leaf) hydraulic conductivity, wood density (Pw), rooting depth, and specific leaf...

  13. Myocarditis as a component of psittacine proventricular dilatation syndrome in a Patagonian conure.

    PubMed

    Vice, C A

    1992-01-01

    Psittacine proventricular dilatation syndrome was diagnosed at necropsy in a Patagonian conure. Gross and histopathological lesions in the proventriculus, ventriculus, and brain were similar to those previously reported. In addition, severe myocarditis was a prominent feature of this case, a finding not previously defined as a significant component of the condition.

  14. Endemic epigean Tenebrionids (Coleoptera: Tenebrionidae) from the Andean Region: exploring the patagonian-diversification hypothesis.

    PubMed

    Carrara, Rodolfo; Flores, Gustavo E

    2015-08-26

    Tenebrionidae is a diverse insect family of Coleoptera that shows high levels of endemicity in epigean species. For the Andean region, which is divided into three subregions: Central Chilean, Subantarctic and Patagonian, it has been hypothesized that epigean tenebrionids have diversified in the Patagonian subregion and subsequently, they dispersed to Subantarctic and Central Chilean subregions. In this work, based on information obtained from museum collections and scientific studies, we presented the first list of endemic epigean tenebrionids from the Andean region with their taxonomic arrangement and geographic distribution. Moreover, we used these data to explore the veracity of the Patagonian-diversification hypothesis. A total of 416 species grouped into six subfamilies, 17 tribes and 41 genera were identified as endemic to the Andean region. Considering the spatial distribution it was observed that subfamilies, tribes, genera and species were unequally distributed across subregions. Results did not support the Patagonian-diversification hypothesis; to the contrary, they were more concordant with processes of isolation among subregions that have promoted speciation by interrupting gene flow among populations, resulting in endemism because species can not expand their range sizes. Finally, we discuss the implications of our findings to be considered in biodiversity conservation, because endemic species, by their high extinction risk, are primary targets in conservation strategies.

  15. Osseous Metaplasia in a Free-living Snake (Patagonian Green Racer; Philodryas patagoniensis) in Brazil, 2012.

    PubMed

    Nogueira, Carlos H O; Jerdy, Hassan L; Silveira, Leonardo S

    2016-04-28

    We describe an osseous metaplasia in a wild Patagonian green racer (Philodryas patagoniensis). The 5.5×1.5-cm lesion of irregular contour on the right dorsolateral surface proximal to the snake's cloaca was raised, hard, ulcerated centrally, and radiopaque and interfered with mobility. Microscopy revealed osseous metaplasia on skin and muscle.

  16. The North Patagonian orogenic front and related foreland evolution during the Miocene, analyzed from synorogenic sedimentation and U/Pb dating (˜42°S)

    NASA Astrophysics Data System (ADS)

    Ramos, Miguel E.; Tobal, Jonathan E.; Sagripanti, Lucía; Folguera, Andrés; Orts, Darío L.; Giménez, Mario; Ramos, Victor A.

    2015-12-01

    Miocene sedimentary successions of the Ñirihuau and Collón Cura formations east of the El Maitén Belt constitute a partial record of the Andean exhumation, defining a synorogenic infill of the Ñirihuau Basin in the foothills of the North Patagonian fold and thrust belt. Gravimetric and seismic data allow recognizing the internal arrangement and geometry of these depocenters that host both units, separating a synextensional section previous to the Andean development at these latitudes, from a series of syncontractional units above. A series of progressive unconformities in the upper terms shows the synorogenic character of these units corresponding to the different pulses of deformation that occurred during the middle Miocene. New U-Pb ages constrain these pulses to the ˜13.5-12.9 Ma interval and allow reconstructing the tectonic history of this region based on the detrital zircon source populations. The U-Pb maximum ages of sedimentation give to the Ñirihuau Formation in particular a younger age than previously assumed. Additionally, synsedimentary deformation in strata of the upper exposures of the Collón Cura Formation associated with contractional structures and U-Pb ages allow identifying a younger paleoseismogenic pulse in ˜11.3 Ma. Thus, based on these data and a compilation of previous datasets, a tectonic evolution is proposed characterized by a contractional episode that migrated eastwardly since ˜19 to 15 Ma producing the Gastre broken foreland and then retracted to the eastern North Patagonian Precordillera, where out-of-sequence thrusts cannibalized the wedge top zone in the El Maitén belt at ˜13.5-11.3 Ma.

  17. Martian seismicity

    NASA Technical Reports Server (NTRS)

    Phillips, Roger J.; Grimm, Robert E.

    1991-01-01

    The design and ultimate success of network seismology experiments on Mars depends on the present level of Martian seismicity. Volcanic and tectonic landforms observed from imaging experiments show that Mars must have been a seismically active planet in the past and there is no reason to discount the notion that Mars is seismically active today but at a lower level of activity. Models are explored for present day Mars seismicity. Depending on the sensitivity and geometry of a seismic network and the attenuation and scattering properties of the interior, it appears that a reasonable number of Martian seismic events would be detected over the period of a decade. The thermoelastic cooling mechanism as estimated is surely a lower bound, and a more refined estimate would take into account specifically the regional cooling of Tharsis and lead to a higher frequency of seismic events.

  18. Significant nonsymbiotic nitrogen fixation in Patagonian ombrotrophic bogs.

    PubMed

    Knorr, Klaus-Holger; Horn, Marcus A; Borken, Werner

    2015-06-01

    Nitrogen (N) nutrition in pristine peatlands relies on the natural input of inorganic N through atmospheric deposition or biological dinitrogen (N2 ) fixation. However, N2 fixation and its significance for N cycling, plant productivity, and peat buildup are mostly associated with the presence of Sphagnum mosses. Here, we report high nonsymbiotic N2 -fixation rates in two pristine Patagonian bogs with diversified vegetation and natural N deposition. Nonsymbiotic N2 fixation was measured in samples from 0 to 10, 10 to 20, and 40 to 50 cm depth using the (15) N2 assay as well as the acetylene reduction assay (ARA). The ARA considerably underestimated N2 fixation and can thus not be recommended for peatland studies. Based on the (15) N2 assay, high nonsymbiotic N2 -fixation rates of 0.3-1.4 μmol N2  g(-1)  day(-1) were found down to 50 cm under micro-oxic conditions (2 vol.%) in samples from plots covered by Sphagnum magellanicum or by vascular cushion plants, latter characterized by dense and deep aerenchyma roots. Peat N concentrations point to greater potential of nonsymbiotic N2 fixation under cushion plants, likely because of the availability of easily decomposable organic compounds and oxic conditions in the rhizosphere. In the Sphagnum plots, high N2 fixation below 10 cm depth rather reflects the potential during dry periods or low water level when oxygen penetrates the top peat layer and triggers peat mineralization. Natural abundance of the (15) N isotope of live Sphagnum (5.6 δ‰) from 0 to 10 cm points to solely N uptake from atmospheric deposition and nonsymbiotic N2 fixation. A mean (15) N signature of -0.7 δ‰ of peat from the cushion plant plots indicates additional N supply from N mineralization. Our findings suggest that nonsymbiotic N2 fixation overcomes N deficiency in different vegetation communities and has great significance for N cycling and peat accumulation in pristine peatlands. © 2014 John Wiley & Sons Ltd.

  19. Estimation of overland flow metrics at semiarid condition: Patagonian Monte

    NASA Astrophysics Data System (ADS)

    Rossi, M. J.; Ares, J. O.

    2012-05-01

    Water infiltration and overland flow (WIOF) processes are relevant in considering water partition among plant life forms, the sustainability of vegetation and the design of sustainable hydrological management. WIOF processes in arid and semiarid regions present regional characteristic trends imposed by the prevailing physical conditions of the upper soil as evolved under water-limited climate. A set of plot-scale field experiments at the semi-arid Patagonian Monte (Argentina) was performed in order to estimate infiltration-overland descriptive flow parameters. The micro-relief of undisturbed field plots at z-scale <1 mm was characterized through close-range stereo-photogrammetry and geo-statistical modelling. The overland flow areas produced by experimental runoff events were video-recorded and the runoff speed was measured with ortho-image processing software. Antecedent and post-inflow moisture were measured, and texture, bulk density and physical properties of the soil at the upper vadose zone were estimated. Field data were used to calibrate a physically-based, time explicit model of water balance in the upper soil and overland flows with a modified Green-Ampt (infiltration) and Chezy's (overland flow) algorithms. Modelling results satisfy validation criteria based on the observed overland flow areas, runoff-speed, water mass balance of the upper vadose zone, infiltration depth, slope along runoff-plume direction, and depression storage intensity. The experimental procedure presented supplies plot-scale estimates of overland flow and infiltration intensities at various intensities of water input which can be incorporated in larger-scale hydrological grid-models of arid regions. Findings were: (1) Overland flow velocities as well as infiltration-overland flow mass balances are consistently modelled by considering variable infiltration rates corresponding to depression storage and/or non-ponded areas. (2) The statistical relations presented allow the estimation

  20. Tectonic evolution of the North Patagonian Andes (41°-44° S) through recognition of syntectonic strata

    NASA Astrophysics Data System (ADS)

    Echaurren, A.; Folguera, A.; Gianni, G.; Orts, D.; Tassara, A.; Encinas, A.; Giménez, M.; Valencia, V.

    2016-05-01

    The North Patagonian fold-thrust belt (41°-44° S) is characterized by a low topography, reduced crustal thickness and a broad lateral development determined by a broken foreland system in the retroarc zone. This particular structural system has not been fully addressed in terms of the age and mechanisms that built this orogenic segment. Here, new field and seismic evidence of syntectonic strata constrain the timing of the main deformational stages, evaluating the prevailing crustal regime for the different mountain domains through time. Growth strata and progressive unconformities, controlled by extensional or compressive structures, were recognized in volcanic and sedimentary rocks from the cordilleran to the extra-Andean domain. These data were used to construct a balanced cross section, whose deep structure was investigated through a thermomechanical model that characterizes the upper plate rheology. Our results indicate two main compressive stages, interrupted by an extensional relaxation period. The first contractional stage in the mid-Cretaceous inverted Jurassic-Lower Cretaceous half graben systems, reactivating the western Cañadón Asfalto rift border ~ 500 km away from the trench, at a time of arc foreland expansion. For this stage, available thermochronological data reveal forearc cooling episodes, and global tectonic reconstructions indicate mid-ocean ridge collisions against the western edge of an upper plate with rapid trenchward displacement. Widespread synextensional volcanism is recognized throughout the Paleogene during plate reorganization; retroarc Paleocene--Eocene flare up activity is interpreted as product of a slab rollback, and fore-to-retroarc Oligocene slab/asthenospheric derived products as an expression of enhanced extension. The second stage of mountain growth occurred in Miocene time associated with Nazca Plate subduction, reaching nearly the same amplitude than the first compressive stage. Extensional weakening of the upper plate

  1. Plant species richness and shrub cover attenuate drought effects on ecosystem functioning across Patagonian rangelands.

    PubMed

    Gaitán, Juan J; Bran, Donaldo; Oliva, Gabriel; Maestre, Fernando T; Aguiar, Martín R; Jobbágy, Esteban; Buono, Gustavo; Ferrante, Daniela; Nakamatsu, Viviana; Ciari, Georgina; Salomone, Jorge; Massara, Virginia

    2014-10-01

    Drought is an increasingly common phenomenon in drylands as a consequence of climate change. We used 311 sites across a broad range of environmental conditions in Patagonian rangelands to evaluate how drought severity and temperature (abiotic factors) and vegetation structure (biotic factors) modulate the impact of a drought event on the annual integral of normalized difference vegetation index (NDVI-I), our surrogate of ecosystem functioning. We found that NDVI-I decreases were larger with both increasing drought severity and temperature. Plant species richness (SR) and shrub cover (SC) attenuated the effects of drought on NDVI-I. Grass cover did not affect the impacts of drought on NDVI-I. Our results suggest that warming and species loss, two important imprints of global environmental change, could increase the vulnerability of Patagonian ecosystems to drought. Therefore, maintaining SR through appropriate grazing management can attenuate the adverse effects of climate change on ecosystem functioning.

  2. Plant species richness and shrub cover attenuate drought effects on ecosystem functioning across Patagonian rangelands

    PubMed Central

    Gaitán, Juan J.; Bran, Donaldo; Oliva, Gabriel; Maestre, Fernando T.; Aguiar, Martín R.; Jobbágy, Esteban; Buono, Gustavo; Ferrante, Daniela; Nakamatsu, Viviana; Ciari, Georgina; Salomone, Jorge; Massara, Virginia

    2014-01-01

    Drought is an increasingly common phenomenon in drylands as a consequence of climate change. We used 311 sites across a broad range of environmental conditions in Patagonian rangelands to evaluate how drought severity and temperature (abiotic factors) and vegetation structure (biotic factors) modulate the impact of a drought event on the annual integral of normalized difference vegetation index (NDVI-I), our surrogate of ecosystem functioning. We found that NDVI-I decreases were larger with both increasing drought severity and temperature. Plant species richness (SR) and shrub cover (SC) attenuated the effects of drought on NDVI-I. Grass cover did not affect the impacts of drought on NDVI-I. Our results suggest that warming and species loss, two important imprints of global environmental change, could increase the vulnerability of Patagonian ecosystems to drought. Therefore, maintaining SR through appropriate grazing management can attenuate the adverse effects of climate change on ecosystem functioning. PMID:25339654

  3. Seafood substitutions obscure patterns of mercury contamination in Patagonian toothfish (Dissostichus eleginoides) or "Chilean sea bass".

    PubMed

    Marko, Peter B; Nance, Holly A; van den Hurk, Peter

    2014-01-01

    Seafood mislabeling distorts the true abundance of fish in the sea, defrauds consumers, and can also cause unwanted exposure to harmful pollutants. By combining genetic data with analyses of total mercury content, we have investigated how species substitutions and fishery-stock substitutions obscure mercury contamination in Patagonian toothfish (Dissostichus eleginoides), also known as "Chilean sea bass". Patagonian toothfish show wide variation in mercury concentrations such that consumers may be exposed to either acceptable or unacceptable levels of mercury depending on the geographic origins of the fish and the allowable limits of different countries. Most notably, stocks of Patagonian toothfish in Chile accumulate significantly more mercury than stocks closer to the South Pole, including the South Georgia/Shag Rocks stock, a fishery certified by the Marine Stewardship Council (MSC) as sustainably fished. Consistent with the documented geography of mercury contamination, our analysis showed that, on average, retail fish labeled as MSC-certified Patagonian toothfish had only half the mercury of uncertified fish. However, consideration of genetic data that were informative about seafood substitutions revealed a complex pattern of contamination hidden from consumers: species substitutions artificially inflated the expected difference in mercury levels between MSC-certified and uncertified fish whereas fishery stock substitutions artificially reduced the expected difference in mercury content between MSC-certified and uncertified fish that were actually D. eleginoides. Among MSC-certified fish that were actually D. eleginoides, several with exogenous mtDNA haplotypes (i.e., not known from the certified fishery) had mercury concentrations on par with uncertified fish from Chile. Overall, our analysis of mercury was consistent with inferences from the genetic data about the geographic origins of the fish, demonstrated the potential negative impact of seafood

  4. Oxygen and carbon stable isotopes in otoliths record spatial isolation of Patagonian toothfish ( Dissostichus eleginoides)

    NASA Astrophysics Data System (ADS)

    Ashford, Julian; Jones, Cynthia

    2007-01-01

    Strong contrasts in ambient isotope ratios and in diet suggest stable isotopes in the otoliths of oceanic fish can resolve water masses and geographic areas, promising a powerful multivariate approach for examining population structure and provenance. To test this, whole otoliths were taken from Patagonian toothfish ( Dissostichus eleginoides) sampled off the Patagonian Shelf and South Georgia, on either side of a population boundary, and otolith δ 18O and δ 13C values were measured to see if they could distinguish South American-caught fish from those taken in the Antarctic. Values of otolith δ 18O and δ 13C predicted capture area with 100% success, validating their use for distinguishing provenance and corroborating the prior evidence of population isolation. Values of δ 18O in the otoliths reflected ambient values as well as seawater temperature: low values in Patagonian Shelf fish were consistent with exposure to Antarctic Intermediate Water (AAIW), and high values in South Georgia fish were consistent with exposure to Circumpolar Deep Water (CDW). In contrast, differences in otolith δ 13C appeared to reflect diet: relative depletion of otolith δ 13C at South Georgia compared to the Patagonian Shelf were most likely linked to differences in sources of metabolic carbon, as well as δ 13C in dissolved inorganic carbon (DIC) of seawater. These contrasting properties strongly suggest that stable isotopes can resolve the provenance of toothfish from Antarctic sampling areas that hitherto have been difficult to separate. These results show that, by using the chemistry recorded in otoliths, researchers can exploit biogeochemical variation in fully marine environments to examine the spatial ecology of oceanic fish.

  5. Genetic footprints of late Quaternary climate change in the diversity of Patagonian-Fueguian rodents.

    PubMed

    Lessa, Enrique P; D'Elía, Guillermo; Pardiñas, Ulyses F J

    2010-08-01

    Species are impacted by climate change at both ecological and evolutionary time scales. Studies in northern continents have provided abundant evidence of dramatic shifts in distributions of species subsequent to the last glacial maximum (LGM), particularly at high latitudes. However, little is known about the history of southern continents, especially at high latitudes. South America is the only continent, other than Antarctica, that extends beyond 40 degrees S. Genetic studies of a few Patagonian species have provided seemingly conflicting results, indicating either postglacial colonization from restricted glacial refugia or persistence through glacial cycles and in situ differentiation. Using mitochondrial DNA sequences of 14 species of sigmodontine rodents, a major faunal ensemble of Patagonia and Tierra del Fuego, we show that at least nine of these species bear genetic footprints of demographic expansion from single restricted sources. However, timing of demographic expansion precedes the LGM in most of these species. Four species are fragmented phylogeographically within the region. Our results indicate that (i) demographic instability in response to historical climate change has been widespread in the Patagonian-Fueguian region, and is generally more pronounced at high latitudes in both southern and northern continents; (ii) colonization from lower latitudes is an important component of current Patagonian-Fueguian diversity; but (iii) in situ differentiation has also contributed to species diversity.

  6. Skate assemblage on the eastern Patagonian Shelf and Slope: structure, diversity and abundance.

    PubMed

    Arkhipkin, A; Brickle, P; Laptikhovsky, V; Pompert, J; Winter, A

    2012-04-01

    The eastern Patagonian Shelf and continental slope of the south-west Atlantic Ocean support a high biodiversity and abundance of skates. In this study, meso-scale differences in the assemblages, spatial and seasonal distributions of skates are revealed among six habitat zones of the eastern Patagonian Shelf characterized by distinctive oceanographic conditions. Most skates belonged to temperate fauna, and their abundance was much greater in habitats occupied by temperate waters (north-western outer shelf) or mixed waters (northern slope) than in habitats occupied by sub-Antarctic waters (SASW) (south-eastern outer shelf and southern slope). Sub-Antarctic skates were not abundant on the shelf even in habitats occupied by SASW, occurring mainly in deep areas of the lower continental slope. The majority of temperate skates migrated seasonally, shifting northward in winter and spreading southward with warming waters in summer. Most temperate species had two peaks in female maturity (mainly spring and autumn) and spawned in the same habitats where they fed. It is hypothesized that the high biodiversity and abundance of skates on the Patagonian Shelf and Slope are due to the practical absence of their natural competitors, flatfishes, which occupy similar eco-niches elsewhere.

  7. Fossil pollen records indicate that Patagonian desertification was not solely a consequence of Andean uplift.

    PubMed

    Palazzesi, L; Barreda, V D; Cuitiño, J I; Guler, M V; Tellería, M C; Ventura Santos, R

    2014-03-28

    The Patagonian steppe-a massive rain-shadow on the lee side of the southern Andes-is assumed to have evolved ~15-12 Myr as a consequence of the southern Andean uplift. However, fossil evidence supporting this assumption is limited. Here we quantitatively estimate climatic conditions and plant richness for the interval ~10-6 Myr based on the study and bioclimatic analysis of terrestrially derived spore-pollen assemblages preserved in well-constrained Patagonian marine deposits. Our analyses indicate a mesothermal climate, with mean temperatures of the coldest quarter between 11.4 °C and 16.9 °C (presently ~3.5 °C) and annual precipitation rarely below 661 mm (presently ~200 mm). Rarefied richness reveals a significantly more diverse flora during the late Miocene than today at the same latitude but comparable with that approximately 2,000 km further northeast at mid-latitudes on the Brazilian coast. We infer that the Patagonian desertification was not solely a consequence of the Andean uplift as previously insinuated.

  8. Seismic seiches

    USGS Publications Warehouse

    McGarr, Arthur; Gupta, Harsh K.

    2011-01-01

    Seismic seiche is a term first used by Kvale (1955) to discuss oscillations of lake levels in Norway and England caused by the Assam earthquake of August 15, 1950. This definition has since been generalized to apply to standing waves set up in closed, or partially closed, bodies of water including rivers, shipping channels, lakes, swimming pools and tanks due to the passage of seismic waves from an earthquake.

  9. Seismic Discrimination

    DTIC Science & Technology

    1981-03-31

    for second-order Sturm - Liouville boundary-value problems, such a count of eigenvalues may be established in terms of the number of zero crossings of...will be operational during the next six months. Section 11 describes a series of activities in the development and imple- mentation of the seismic...element of seismic research. with emphasis on those areas directly related to tho operations of the SDC. Substantial progress has been made in the

  10. Folding, thrusting and development of push-up structures during the Miocene tectonic inversion of the Austral Basin, Southern Patagonian Andes (50°S)

    NASA Astrophysics Data System (ADS)

    Zerfass, Henrique; Ramos, Victor A.; Ghiglione, Matias C.; Naipauer, Maximiliano; Belotti, Hugo J.; Carmo, Isabela O.

    2017-03-01

    Rift and post-rift sections of the Austral Basin in the Southern Patagonian fold and thrust belt were examined in outcrop and in 2D seismic reflection sections to evaluate geometric and kinematic aspects of the extension and subsequent inversion. The syn-rift section is composed of dacitic lava flows of the El Quemado Complex (Jurassic), the lowermost unit of the basin. The coastal sandstones of the Springhill Formation (Tithonian-Berriasian) and marine shales of the Río Mayer Formation (Berriasian-Albian) are thought to be sag units. However, field data suggest that these units are also part of the syn-rift successions, as evidenced by extensional growth strata in the lower levels of the Río Mayer Formation. A dacitic flow that is texturally and compositionally similar to those of the syn-rift phase and that is termed here the Río Guanaco dacite is interfingered with the basal strata of the Río Mayer Formation and has a U-Pb zircon crystallization age of c. 141 Ma (Berriasian). The outcropping section was inverted by compression in the early Miocene, according to structural and isotopic data of adjacent areas, producing a broad anticline with inverted and fossil extensional faults as well as newly generated thrusts. At the seismic scale, most of the extensional master faults present negligible reverse slip, and shortening was accommodated in hanging wall push-up structures. This situation is interpreted as a result of the competent metamorphic basement and volcanic syn-rift section, inducing frictional lock-up of the master faults.

  11. Seismic bearing

    NASA Astrophysics Data System (ADS)

    Power, Dennis

    2009-05-01

    Textron Systems (Textron) has been using geophones for target detection for many years. This sensing capability was utilized for detection and classification purposes only. Recently Textron has been evaluating multiaxis geophones to calculate bearings and track targets more specifically personnel. This capability will not only aid the system in locating personnel in bearing space or cartesian space but also enhance detection and reduce false alarms. Textron has been involved in the testing and evaluation of several sensors at multiple sites. One of the challenges of calculating seismic bearing is an adequate signal to noise ratio. The sensor signal to noise ratio is a function of sensor coupling to the ground, seismic propagation and range to target. The goals of testing at multiple sites are to gain a good understanding of the maximum and minimum ranges for bearing and detection and to exploit that information to tailor sensor system emplacement to achieve desired performance. Test sites include 10A Site Devens, MA, McKenna Airfield Ft. Benning, GA and Yuma Proving Ground Yuma, AZ. Geophone sensors evaluated include a 28 Hz triax spike, a 15 Hz triax spike and a hybrid triax spike consisting of a 10 Hz vertical geophone and two 28 Hz horizontal geophones. The algorithm uses raw seismic data to calculate the bearings. All evaluated sensors have triaxial geophone configuration mounted to a spike housing/fixture. The suite of sensors also compares various types of geophones to evaluate benefits in lower bandwidth. The data products of these tests include raw geophone signals, seismic features, seismic bearings, seismic detection and GPS position truth data. The analyses produce Probability of Detection vs range, bearing accuracy vs range, and seismic feature level vs range. These analysis products are compared across test sites and sensor types.

  12. Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield

    NASA Astrophysics Data System (ADS)

    Bertrand, S.; Hughen, K. A.; Lamy, F.; Stuut, J.-B. W.; Torrejón, F.; Lange, C. B.

    2012-03-01

    Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided into three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we suggest that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the North Patagonian Andes.

  13. Phylogeography and palaeodistribution modelling of Nassauvia subgenus Strongyloma (Asteraceae): exploring phylogeographical scenarios in the Patagonian steppe

    PubMed Central

    Nicola, Marcela V; Sede, Silvana M; Pozner, Raúl; Johnson, Leigh A

    2014-01-01

    The Patagonian steppe is an immense, cold, arid region, yet phylogeographically understudied. Nassauvia subgen. Strongyloma is a characteristic element of the steppe, exhibiting a continuum of morphological variation. This taxon provides a relevant phylogeographical model not only to understand how past environmental changes shaped the genetic structure of its populations, but also to explore phylogeographical scenarios at the large geographical scale of the Patagonian steppe. Here, we (1) assess demographic processes and historical events that shaped current geographic patterns of haplotypic diversity; (2) analyze hypotheses of isolation in refugia, fragmentation of populations, and/or colonization of available areas during Pleistocene glaciations; and (3) model extant and palaeoclimatic distributions to support inferred phylogeographical patterns. Chloroplast intergenic spacers, rpl32–trnL and trnQ–5′rps16, were sequenced for 372 individuals from 63 populations. Nested clade analysis, analyses of molecular variance, and neutrality tests were performed to assess genetic structure and range expansion. The present potential distribution was modelled and projected onto a last glacial maximum (LGM) model. Of 41 haplotypes observed, ten were shared among populations associated with different morphological variants. Populations with highest haplotype diversity and private haplotypes were found in central-western and south-eastern Patagonia, consistent with long-term persistence in refugia during Pleistocene. Palaeomodelling suggested a shift toward the palaeoseashore during LGM; new available areas over the exposed Atlantic submarine platform were colonized during glaciations with postglacial retraction of populations. A scenario of fragmentation and posterior range expansion may explain the observed patterns in the center of the steppe, which is supported by palaeomodelling. Northern Patagonian populations were isolated from southern populations by the Chubut and

  14. Detection of 18.6 year nodal induced drought in the Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Currie, Robert G.

    1983-11-01

    Analysis of tree-ring chronologies from the Patagonian Andes yields evidence for the 18.6 yr lunar nodal term in drought/flood. The mean discrepancy between epochs of drought/flood and the nodal tide since AD 1600 is 0.7 ± 2.2 yr, but the polarity of the signal is apparently bimodal. From nodal epoch 1750.0 through 1898.9 drought and tide were in phase, whereas prior to 1750.0 and subsequent to 1898.9 drought and tide were out of phase. There is evidence also for the solar cycle drought signal in the data.

  15. A CASE OF TRYCHOPHYTON RUBRUM DERMATOPHYTOSIS IN A PATAGONIAN SEA LION (OTARIA BYRONIA).

    PubMed

    Quintard, Benoît; Lohmann, Caroline; Lefaux, Brice

    2015-09-01

    A 23-yr old female Patagonian sea lion (Otaria byronia) presented multifocal to coalescing and ulcerative skin lesions on the lumbar region. Skin scrapings were collected and a microscopic examination was conducted followed by a fungal culture that revealed a Trychophyton rubrum infection, an anthropophilic dermatophytosis agent. Oral terbinafine and topical eniconazole were used as a treatment for a period of 75 days and complete recovery was achieved. Epidemiological analysis revealed a dermatophytosis case in one of the carnivore section keepers a few weeks before the lesions were diagnosed in the sea lion.

  16. Antarctic timing of surface water changes off Chile and Patagonian ice sheet response.

    PubMed

    Lamy, Frank; Kaiser, Jérôme; Ninnemann, Ulysses; Hebbeln, Dierk; Arz, Helge W; Stoner, Joseph

    2004-06-25

    Marine sediments from the Chilean continental margin are used to infer millennial-scale changes in southeast Pacific surface ocean water properties and Patagonian ice sheet extent since the last glacial period. Our data show a clear "Antarctic" timing of sea surface temperature changes, which appear systematically linked to meridional displacements in sea ice, westerly winds, and the circumpolar current system. Proxy data for ice sheet changes show a similar pattern as oceanographic variations offshore, but reveal a variable glacier-response time of up to approximately 1000 years, which may explain some of the current discrepancies among terrestrial records in southern South America.

  17. New cystidicolid species (Nematoda) from Galaxias platei (Osmeriformes: Galaxiidae) in Patagonian freshwater environments.

    PubMed

    Brugni, Norma L; Viozzi, Gustavo P

    2008-08-01

    During a parasitological survey of Galaxias platei Steindachner, 1898, from Patagonian Andean Lakes, a new species of Cystidicolidae was found in the stomach of fish. The new species was described using light and scanning electron microscopy; the species has characteristics of Ascarophis and is distinguishable from other species by a combination of the following features: well-developed pseudolabia with T-shaped inner extensions, bifurcate deirids, small ratio GE:ME, small left spicule, small ratio LS:RS, and larvigerous eggs with thick and fine filaments in both poles. Intraspecific variation in the morphology of larvigerous eggs was studied. This is the first species of Ascarophis described from freshwater fishes.

  18. Seismic Studies

    SciTech Connect

    R. Quittmeyer

    2006-09-25

    This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground motion at

  19. Seismic Discrimination

    DTIC Science & Technology

    1975-12-31

    dyn-cm. It can be seen that there is a wide range of the potential con- tribution of different seismic zones to excitation of the Chandler wobble ...Correction to the Excitation of the Chandler Wobble by Earthquakes," Geophys. J. R. Astron. Soc. 32, 203-217 (1973). 22. S. C. Solomon, N. H. Sleep

  20. Seismic Tomography.

    ERIC Educational Resources Information Center

    Anderson, Don L.; Dziewonski, Adam M.

    1984-01-01

    Describes how seismic tomography is used to analyze the waves produced by earthquakes. The information obtained from the procedure can then be used to map the earth's mantle in three dimensions. The resulting maps are then studied to determine such information as the convective flow that propels the crustal plates. (JN)

  1. Seismic Tomography.

    ERIC Educational Resources Information Center

    Anderson, Don L.; Dziewonski, Adam M.

    1984-01-01

    Describes how seismic tomography is used to analyze the waves produced by earthquakes. The information obtained from the procedure can then be used to map the earth's mantle in three dimensions. The resulting maps are then studied to determine such information as the convective flow that propels the crustal plates. (JN)

  2. Seismic Symphonies

    NASA Astrophysics Data System (ADS)

    Strinna, Elisa; Ferrari, Graziano

    2015-04-01

    The project started in 2008 as a sound installation, a collaboration between an artist, a barrel organ builder and a seismologist. The work differs from other attempts of sound transposition of seismic records. In this case seismic frequencies are not converted automatically into the "sound of the earthquake." However, it has been studied a musical translation system that, based on the organ tonal scale, generates a totally unexpected sequence of sounds which is intended to evoke the emotions aroused by the earthquake. The symphonies proposed in the project have somewhat peculiar origins: they in fact come to life from the translation of graphic tracks into a sound track. The graphic tracks in question are made up by copies of seismograms recorded during some earthquakes that have taken place around the world. Seismograms are translated into music by a sculpture-instrument, half a seismograph and half a barrel organ. The organ plays through holes practiced on paper. Adapting the documents to the instrument score, holes have been drilled on the waves' peaks. The organ covers about three tonal scales, starting from heavy and deep sounds it reaches up to high and jarring notes. The translation of the seismic records is based on a criterion that does match the highest sounds to larger amplitudes with lower ones to minors. Translating the seismogram in the organ score, the larger the amplitude of recorded waves, the more the seismogram covers the full tonal scale played by the barrel organ and the notes arouse an intense emotional response in the listener. Elisa Strinna's Seismic Symphonies installation becomes an unprecedented tool for emotional involvement, through which can be revived the memory of the greatest disasters of over a century of seismic history of the Earth. A bridge between art and science. Seismic Symphonies is also a symbolic inversion: the instrument of the organ is most commonly used in churches, and its sounds are derived from the heavens and

  3. Molecular Detection of Bioluminescent Dinoflagellates in Surface Waters of the Patagonian Shelf during Early Austral Summer 2008

    PubMed Central

    Valiadi, Martha; Painter, Stuart C.; Allen, John T.; Balch, William M.; Iglesias-Rodriguez, M. Debora

    2014-01-01

    We investigated the distribution of bioluminescent dinoflagellates in the Patagonian Shelf region using “universal” PCR primers for the dinoflagellate luciferase gene. Luciferase gene sequences and single cell PCR tests, in conjunction with taxonomic identification by microscopy, allowed us to identify and quantify bioluminescent dinoflagellates. We compared these data to coincidental discrete optical measurements of stimulable bioluminescence intensity. Molecular detection of the luciferase gene showed that bioluminescent dinoflagellates were widespread across the majority of the Patagonian Shelf region. Their presence was comparatively underestimated by optical bioluminescence measurements, whose magnitude was affected by interspecific differences in bioluminescence intensity and by the presence of other bioluminescent organisms. Molecular and microscopy data showed that the complex hydrography of the area played an important role in determining the distribution and composition of dinoflagellate populations. Dinoflagellates were absent south of the Falkland Islands where the cold, nutrient-rich, and well-mixed waters of the Falklands Current favoured diatoms instead. Diverse populations of dinoflagellates were present in the warmer, more stratified waters of the Patagonian Shelf and Falklands Current as it warmed northwards. Here, the dinoflagellate population composition could be related to distinct water masses. Our results provide new insight into the prevalence of bioluminescent dinoflagellates in Patagonian Shelf waters and demonstrate that a molecular approach to the detection of bioluminescent dinoflagellates in natural waters is a promising tool for ecological studies of these organisms. PMID:24918444

  4. Patagonian red wines: selection of Lactobacillus plantarum isolates as potential starter cultures for malolactic fermentation.

    PubMed

    Bravo-Ferrada, Bárbara Mercedes; Hollmann, Axel; Delfederico, Lucrecia; Valdés La Hens, Danay; Caballero, Adriana; Semorile, Liliana

    2013-09-01

    The aim of this study was to evaluate fifty-three Lactobacillus plantarum isolates obtained from a Patagonian red wine, molecularly identified and typified using RAPD analysis, in order to select starter cultures for malolactic fermentation (MLF). The results obtained suggest a considerable genetic diversity, taking into account that all L. plantarum isolates were obtained from one cellar and one vintage. Based on the capacity to tolerate a concentration of 14 % ethanol in MRS broth for 2 days, eight isolates were selected for the subsequent analysis. The incidence of various wine stress factors (ethanol, acid pH, lysozyme and sulfur dioxide) on isolates growth was studied. Besides, glucosidase and tannase activities were evaluated, and the presence of genes involved in the synthesis of biogenic amines was examined by PCR. A previously characterized indigenous Oenococcus oeni strain was included with comparative purposes. Differences in technologically relevant characteristics were observed among the eight L. plantarum selected isolates, revealing an isolate-dependent behavior. Detectable glucosidase and tannase activities were found in all isolates. The presence of genes encoding histidine and tyrosine descarboxylases and putrescine carbamoyltransferase was not detected. The ability of L. plantarum isolates to grow and consume L-malic acid in simulated laboratory-scale vinifications revealed that two of them could be considered as possible MLF starter cultures for Patagonian red wines. These isolates will be subjected to further analysis, for a final winery technological characterization.

  5. Numerical modelling of the M2 tide on the northern Patagonian Shelf

    NASA Astrophysics Data System (ADS)

    Glorioso, P. D.; Simpson, J. H.

    1994-02-01

    The previously reported occurrence of tidal fronts on the Patagonian Shelf ( CARRETOet al., 1986 , Journal of Plankton Research, 8, 15-28; GLORIOSO, 1987 , Continental Shelf Research, 7, 27-34), motivated the application of a numerical model to solve the shallow-water equations with external forcing by the principal-lunar semidiurnal tide (M2) prescribed along the open boundary. The mean width of the Patagonian Shelf is comparable with a quarter wavelength of the semidiurnal tide, giving the conditions for standing wave resonance at that frequency ( WEBB, 1975 , Deep-Sea Research, 23, 1-15). The region is well recognized by its large tidal elevations and by the speed of the tidal wave changing phase very rapidly. Some of the results obtained from the modelling exercise include the mapping of the M2 tidal constants, the Simpson-Hunter stratification parameter, the mean sea surface elevation, and the distribution of tidal energy dissipation by bottom friction. These results agree qualitatively with the ship data available and with satellite infrared imagery.

  6. Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation

    PubMed Central

    Metcalf, Jessica L.; Turney, Chris; Barnett, Ross; Martin, Fabiana; Bray, Sarah C.; Vilstrup, Julia T.; Orlando, Ludovic; Salas-Gismondi, Rodolfo; Loponte, Daniel; Medina, Matías; De Nigris, Mariana; Civalero, Teresa; Fernández, Pablo Marcelo; Gasco, Alejandra; Duran, Victor; Seymour, Kevin L.; Otaola, Clara; Gil, Adolfo; Paunero, Rafael; Prevosti, Francisco J.; Bradshaw, Corey J. A.; Wheeler, Jane C.; Borrero, Luis; Austin, Jeremy J.; Cooper, Alan

    2016-01-01

    The causes of Late Pleistocene megafaunal extinctions (60,000 to 11,650 years ago, hereafter 60 to 11.65 ka) remain contentious, with major phases coinciding with both human arrival and climate change around the world. The Americas provide a unique opportunity to disentangle these factors as human colonization took place over a narrow time frame (~15 to 14.6 ka) but during contrasting temperature trends across each continent. Unfortunately, limited data sets in South America have so far precluded detailed comparison. We analyze genetic and radiocarbon data from 89 and 71 Patagonian megafaunal bones, respectively, more than doubling the high-quality Pleistocene megafaunal radiocarbon data sets from the region. We identify a narrow megafaunal extinction phase 12,280 ± 110 years ago, some 1 to 3 thousand years after initial human presence in the area. Although humans arrived immediately prior to a cold phase, the Antarctic Cold Reversal stadial, megafaunal extinctions did not occur until the stadial finished and the subsequent warming phase commenced some 1 to 3 thousand years later. The increased resolution provided by the Patagonian material reveals that the sequence of climate and extinction events in North and South America were temporally inverted, but in both cases, megafaunal extinctions did not occur until human presence and climate warming coincided. Overall, metapopulation processes involving subpopulation connectivity on a continental scale appear to have been critical for megafaunal species survival of both climate change and human impacts. PMID:27386563

  7. Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation.

    PubMed

    Metcalf, Jessica L; Turney, Chris; Barnett, Ross; Martin, Fabiana; Bray, Sarah C; Vilstrup, Julia T; Orlando, Ludovic; Salas-Gismondi, Rodolfo; Loponte, Daniel; Medina, Matías; De Nigris, Mariana; Civalero, Teresa; Fernández, Pablo Marcelo; Gasco, Alejandra; Duran, Victor; Seymour, Kevin L; Otaola, Clara; Gil, Adolfo; Paunero, Rafael; Prevosti, Francisco J; Bradshaw, Corey J A; Wheeler, Jane C; Borrero, Luis; Austin, Jeremy J; Cooper, Alan

    2016-06-01

    The causes of Late Pleistocene megafaunal extinctions (60,000 to 11,650 years ago, hereafter 60 to 11.65 ka) remain contentious, with major phases coinciding with both human arrival and climate change around the world. The Americas provide a unique opportunity to disentangle these factors as human colonization took place over a narrow time frame (~15 to 14.6 ka) but during contrasting temperature trends across each continent. Unfortunately, limited data sets in South America have so far precluded detailed comparison. We analyze genetic and radiocarbon data from 89 and 71 Patagonian megafaunal bones, respectively, more than doubling the high-quality Pleistocene megafaunal radiocarbon data sets from the region. We identify a narrow megafaunal extinction phase 12,280 ± 110 years ago, some 1 to 3 thousand years after initial human presence in the area. Although humans arrived immediately prior to a cold phase, the Antarctic Cold Reversal stadial, megafaunal extinctions did not occur until the stadial finished and the subsequent warming phase commenced some 1 to 3 thousand years later. The increased resolution provided by the Patagonian material reveals that the sequence of climate and extinction events in North and South America were temporally inverted, but in both cases, megafaunal extinctions did not occur until human presence and climate warming coincided. Overall, metapopulation processes involving subpopulation connectivity on a continental scale appear to have been critical for megafaunal species survival of both climate change and human impacts.

  8. Postglacial history of the Patagonian forest/steppe ecotone (41-43°S)

    NASA Astrophysics Data System (ADS)

    Iglesias, Virginia; Whitlock, Cathy; Markgraf, Vera; Bianchi, María Martha

    2014-06-01

    Patagonian vegetation has dramatically changed in composition and distribution over the last 23,000 years. Although the vegetation history has been inferred from individual pollen records, the regional patterns and drivers of vegetation development are poorly understood. High resolution pollen and charcoal data from eleven sites located along the eastern flanks of the Patagonian Andes (41-43°S) were examined to reconstruct the Lateglacial and Holocene vegetation and fire history of steppe/forest ecotone and separate the relative influence of climatic versus non-climatic factors in shaping the patterns of ecological change. Pollen data indicate that, as the Lateglacial climate became progressively wetter, the initial steppe vegetation was replaced by open forest of Nothofagus in the Lateglacial and early Holocene periods, and by closed forest in the late Holocene. Fire activity was lowest during the Lateglacial/early-Holocene transition and gradually increased through the Holocene. Prior to ca 5000 cal yr BP, the conifer Austrocedrus chilensis possibly persisted in isolated populations along the eastern boundary of its modern distribution. Cooler/more humid conditions after ca 5000 cal yr BP allowed the development of the modern mixed Nothofagus-Austrocedrus forest. The paleoenvironmental record points to the sensitivity of the forest/steppe ecotone in the past, not only to climate but also to complex environmental feedbacks that amplified the effects of climate change.

  9. Microbial eukaryote communities exhibit robust biogeographical patterns along a gradient of Patagonian and Antarctic lakes.

    PubMed

    Schiaffino, M Romina; Lara, Enrique; Fernández, Leonardo D; Balagué, Vanessa; Singer, David; Seppey, Christophe C W; Massana, Ramon; Izaguirre, Irina

    2016-12-01

    Microbial eukaryotes play important roles in aquatic ecosystem functioning. Unravelling their distribution patterns and biogeography provides important baseline information to infer the underlying mechanisms that regulate the biodiversity and complexity of ecosystems. We studied the distribution patterns and factors driving diversity gradients in microeukaryote communities (total, abundant, uncommon and rare community composition) along a latitudinal gradient of lakes distributed from Argentinean Patagonia to Maritime Antarctica using both denaturing gradient gel electrophoresis (DGGE) and high-throughput sequencing (Illumina HiSeq). DGGE and abundant Illumina operational taxonomic units (OTUs) showed both decreasing richness with latitude and significant differences between Patagonian and Antarctic lakes communities. In contrast, total richness did not change significantly across the latitudinal gradient, although evenness and diversity indices were significantly higher in Patagonian lakes. Beta-diversity was characterized by a high species turnover, influenced by both environmental and geographical descriptors, although this pattern faded in the rare community. Our results suggest the co-existence of a 'core biosphere' containing reduced number of abundant/dominant OTUs on which classical ecological rules apply, together with a much larger seedbank of rare OTUs driven by stochastic and reduced dispersal processes. These findings shed new light on the biogeographical patterns and forces structuring inland microeukaryote composition across broad spatial scales. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  10. Glaciation and topographic evolution of the Central Patagonian Andes since 6 Ma

    NASA Astrophysics Data System (ADS)

    Christeleit, E. C.; Laemel, R.; De Wolf, W. E.; Shuster, D. L.; Brandon, M. T.

    2013-12-01

    New and existing thermochronological data are used to model glacial erosion and topographic evolution of the central Patagonian Andes (~47S) over the last 6 Ma. The modern Andes are cut by large valleys and fjords with local valley relief of at least 2.5 km. It is currently thought that a formerly uniformly high Andes was 'buzzed' down to the elevation of the equilibrium line altitude, presumably in the last 2 Ma concurrent with late Cenozoic global cooling. However, studies of glacial debris show that glaciers were present in Patagonia as early as 6 Ma. The extent of these early glaciations is unclear, but recent work suggests that glacial valleys in the central Patagonian Andes were carved at a steady rate beginning at 6 Ma, implying that valley incision may be an important process in the topographic evolution of glaciated mountain ranges, rather than cirque retreat. To understand how valley relief has formed in the Andes, we dated 30 samples from Steffen Fjord in Chile using apatite (U-Th)/He thermochronology. We use this new data and existing thermochronological data in the region to estimate the topographic form of the central Andes at 6 Ma and model how the valley relief has evolved since the initiation of glaciation using Pecube.

  11. Fire cue effects on seed germination of six species of northwestern Patagonian grasslands

    NASA Astrophysics Data System (ADS)

    Gonzalez, S. L.; Ghermandi, L.

    2012-09-01

    Postfire recruitment of seedlings has been attributed to a stimulation of germination by fire-related cues. The germination response to heat shock (80 °C - 5 min), smoke (60 min), the combination of both factors and no heat no smoke (control) was studied in six native species (two dominant grasses, two dominant shrubs and two annual fugitive herbs) of northwestern Patagonian grasslands. Seeds of the grasses Festuca pallescens and Stipa speciosa and the shrub Senecio bracteolatus (Asteraceae) germinated when they were exposed to heat shock, whereas seeds of the other shrub, Mulinum spinosum (Apiaceae), were killed by this fire cue. In grasses, probably the glume of caryopsis protected embryos from heat. Possibly, the seed size could explain the different responses of the two shrubs. Heat combined with smoke reduced seed germination for S. speciosa and S. bracteolatus. The heat could have scarified seeds and the longer exposure to smoke could have been toxic for embryos. The same treatment increased germination of the annual fugitive herb Boopis gracilis (Calyceraceae). We concluded that fire differentially affects the seedling recruitment of the studied species in the northwestern Patagonian grasslands.

  12. Physical processes controlling passive larval transport at the Patagonian Shelf Break Front

    NASA Astrophysics Data System (ADS)

    Franco, Bárbara C.; Palma, Elbio D.; Combes, Vincent; Lasta, Mario L.

    2017-06-01

    The largest beds of the Patagonian scallop (Zygochlamys patagonica) have been associated with high chlorophyll-a concentration observed along the Patagonian Shelf Break Front but there is no supported hypothesis about how this benthic-pelagic connection is maintained. In this work we address the main physical processes driving the benthic-pelagic linkages through oriented numerical experiments derived from a realistic, high-resolution numerical model, and Lagrangian stochastic simulations. The results support the hypothesis of an important dynamical control of the slope current on the fate of surface released passive particles and their subsequent bottom settlement. A high percentage of the particles released at the surface settled over the scallop beds. The particles remaining at the surface layer followed a prevailing NE flow direction with low cross-shelf dispersion. Additional experiments show that the secondary cross-shelf circulation forced by the slope current promotes downwelling and hence the settlement of particles on the westward side (onshore) of the shelf break. The percent of particles settling over the scallop beds exceeded 80% by the addition of vertical stochastic turbulence and tidal forcing. These results highlight the importance of including the vertical diffusivity in particle tracking experiments to better estimate benthic-pelagic interaction processes.

  13. Rapid thinning of the late Pleistocene Patagonian Ice Sheet followed migration of the Southern Westerlies

    PubMed Central

    Boex, J.; Fogwill, C.; Harrison, S.; Glasser, N. F.; Hein, A.; Schnabel, C.; Xu, S.

    2013-01-01

    Here we present the first reconstruction of vertical ice-sheet profile changes from any of the Southern Hemisphere's mid-latitude Pleistocene ice sheets. We use cosmogenic radio-nuclide (CRN) exposure analysis to record the decay of the former Patagonian Ice Sheet (PIS) from the Last Glacial Maximum (LGM) and into the late glacial. Our samples, from mountains along an east-west transect to the east of the present North Patagonian Icefield (NPI), serve as ‘dipsticks' that allow us to reconstruct past changes in ice-sheet thickness, and demonstrates that the former PIS remained extensive and close to its LGM extent in this region until ~19.0 ka. After this time rapid ice-sheet thinning, initiated at ~18.1 ka, saw ice at or near its present dimension by 15.5 ka. We argue this rapid thinning was triggered by a combination of the rapid southward migration of the precipitation bearing Southern Hemisphere (SH) westerlies and regional warming. PMID:23817136

  14. Rapid thinning of the Late Pleistocene Patagonian Ice Sheet followed migration of the Southern Westerlies.

    PubMed

    Boex, J; Fogwill, C; Harrison, S; Glasser, N F; Hein, A; Schnabel, C; Xu, S

    2013-01-01

    Here we present the first reconstruction of vertical ice-sheet profile changes from any of the Southern Hemisphere's mid-latitude Pleistocene ice sheets. We use cosmogenic radio-nuclide (CRN) exposure analysis to record the decay of the former Patagonian Ice Sheet (PIS) from the Last Glacial Maximum (LGM) and into the late glacial. Our samples, from mountains along an east-west transect to the east of the present North Patagonian Icefield (NPI), serve as 'dipsticks' that allow us to reconstruct past changes in ice-sheet thickness, and demonstrates that the former PIS remained extensive and close to its LGM extent in this region until ~19.0 ka. After this time rapid ice-sheet thinning, initiated at ~18.1 ka, saw ice at or near its present dimension by 15.5 ka. We argue this rapid thinning was triggered by a combination of the rapid southward migration of the precipitation bearing Southern Hemisphere (SH) westerlies and regional warming.

  15. Crustal segments in the North Patagonian Massif, Patagonia: An integrated perspective based on Sm-Nd isotope systematics

    NASA Astrophysics Data System (ADS)

    Martínez Dopico, Carmen I.; López de Luchi, Mónica G.; Rapalini, Augusto E.; Kleinhanns, Ilka C.

    2011-03-01

    New insights on the Paleozoic evolution of the continental crust in the North Patagonian Massif are presented based on the analysis of Sm-Nd systematics. New evidence is presented to constrain tectonic models for the origin of Patagonia and its relations with the South American crustal blocks. Geologic, isotopic and tectonic characterization of the North Patagonian Massif and comparison of the Nd parameters lead us to conclude that: (1) The North Patagonian Massif is a crustal block with bulk crustal average ages between 2.1 and 1.6 Ga TDM (Nd) and (2) At least three metamorphic episodes could be identified in the Paleozoic rocks of the North Patagonian Massif. In the northeastern corner, Famatinian metamorphism is widely identified. However field and petrographic evidence indicate a Middle to Late Cambrian metamorphism pre-dating the emplacement of the ca. 475 Ma granitoids. In the southwestern area, are apparent 425-420 Ma (?) and 380-360 Ma metamorphic peaks. The latter episode might have resulted from the collision of the Antonia terrane; and (3) Early Paleozoic magmatism in the northeastern area is coeval with the Famatinian arc. Nd isotopic compositions reveal that Ordovician magmatism was associated with attenuated crust. On the southwestern border, the first magmatic recycling record is Devonian. Nd data shows a step by step melting of different levels of the continental crust in the Late Palaeozoic. Between 330 and 295 Ma magmatism was likely the product of a crustal source with an average 1.5 Ga TDM (Nd). Widespread magmatism represented by the 295-260 Ma granitoids involved a lower crustal mafic source, and continued with massive shallower-acid plutono volcanic complexes which might have recycled an upper crustal segment of the Proterozoic continental basement, resulting in a more felsic crust until the Triassic. (4) Sm-Nd parameters and detrital zircon age patterns of Early Paleozoic (meta)-sedimentary rocks from the North Patagonian Massif and those

  16. Seismic Discrimination

    DTIC Science & Technology

    1977-03-31

    Determining Phase and Group Velocities of Surface Seismic Waves 21 B. Group-Velocity Measurements Across Eurasia from Mashad SRO 22 C. Group-Velocity...Albuquerque), MAIO ( Mashad ), GUMO (Guam), NWAO (Australia), SNZO (New Zealand), and TATO (Taiwan). Fairly extensive data are now a|ailable for the...include a new rapid algorithm for the determination of group and phase velocity, a series of observations of Rayleigh-wave dispersion at the Mashad

  17. Seismic testing

    SciTech Connect

    Knott, S.

    1981-10-01

    Electric Power Research Institute (EPRI) research programs in seismic testing to improve earthquake design guidelines lowers the safety-design costs of nuclear power plants. Explosive tests that simulate earthquakes help to determine how structures respond to ground motion and how these are related to soil and geologic conditions at a specific site. Explosive tests develop data for simulation using several computer codes. Photographs illustrate testing techniques. 6 references. (DCK)

  18. The last glacial termination on the eastern flank of the central Patagonian Andes (47 ° S)

    NASA Astrophysics Data System (ADS)

    Henríquez, William I.; Villa-Martínez, Rodrigo; Vilanova, Isabel; De Pol-Holz, Ricardo; Moreno, Patricio I.

    2017-07-01

    Few studies have examined in detail the sequence of events during the last glacial termination (T1) in the core sector of the Patagonian Ice Sheet (PIS), the largest ice mass in the Southern Hemisphere outside of Antarctica. Here we report results from Lago Edita (47°8' S, 72°25' W, 570 m a.s.l.), a small closed-basin lake located in a valley overridden by eastward-flowing Andean glaciers during the Last Glacial Maximum (LGM). The Lago Edita record shows glaciolacustrine sedimentation until 19 400 yr BP, followed by organic sedimentation in a closed-basin lake and a mosaic of cold-resistant hygrophilous conifers and rainforest trees, along with alpine herbs between 19 400 and 11 000 yr BP. Our data suggest that the PIS retreated at least ˜ 90 km from its LGM limit between ˜ 21 000 and 19 400 yr BP and that scattered, low-density populations of cold-resistant hygrophilous conifers, rainforest trees, high-Andean and steppe herbs thrived east of the Andes during the LGM and T1, implying high precipitation levels and southern westerly wind (SWW) influence at 47° S. The conifer Podocarpus nubigena increased between 14 500 and 13 000 yr BP, suggesting even stronger SWW influence during the Antarctic Cold Reversal, after which it declined and persisted until 11 000 yr BP. Large increases in arboreal pollen at ˜ 13 000 and ˜ 11 000 yr BP led to the establishment of forests near Lago Edita between 10 000 and 9000 yr BP, suggesting a rise in the regional tree line along the eastern Andean slopes driven by warming pulses at ˜ 13 000 and ˜ 11 000 yr BP and a subsequent decline in SWW influence at ˜ 11 000 yr BP. We propose that the PIS imposed a regional cooling signal along its eastern, downwind margin through T1 that lasted until the separation of the northern and southern Patagonian ice fields along the Andes during the Younger Dryas period. We posit that the withdrawal of glacial and associated glaciolacustrine environments through T1 provided a route for the

  19. Crustal deformation across the Southern Patagonian Icefield: GNSS observations and GIA models

    NASA Astrophysics Data System (ADS)

    Mendoza, Luciano; Richter, Andreas; Marderwald, Eric; Hormaechea, José Luis; Ivins, Erik; Perdomo, Raúl; Lange, Heiner; Schröder, Ludwig; Dietrich, Reinhard

    2017-04-01

    We present the geodetic observation and geodynamic interpretation of crustal deformation rates in a network of 43 GNSS sites covering the region of the Southern Patagonian Icefield (Argentina and Chile). Repeated and semi-permanent GNSS observations initiated in 1996 yield 3D site velocities within a terrestrial reference frame with mean accuracies of 1 mm/a and 6 mm/a for the horizontal and vertical components, respectively. These site velocities are interpreted with regard to the magnitude, patterns and primary driving processes of vertical and horizontal present-day crustal deformation (Richter et al. 2016). The vertical site velocities document a rapid uplift causally related to glacial-isostatic adjustment (GIA) reaching 4 cm/a. They yield now an unambiguous preference between two competing regional GIA models (Lange et al. 2014). Remaining discrepancies between the preferred model and our observations point toward an exceptionally low effective upper mantle viscosity and effects of lateral rheological heterogeneities. The extension and geometry of our network allow, for the first time, also a detailed analysis of the horizontal velocity components. An analysis of the horizontal strain-rate field reveals a complex composite, with compression dominating in the west and extension in the east. The observed velocities suggest significant contributions from three processes: GIA, a western interseismic tectonic deformation field related to plate subduction, and an extensional strain-rate field related to active Patagonian slab window tectonics. They document a dual interaction between the peculiar tectonic situation and the visco-elastic response to ice-load changes: First, a mechanical superposition of the characteristic patterns of each of the three processes, which results in the complex superposition of horizontal deformation revealed by our strain analysis. And second, the lateral differentiation of the glacial-isostatic response imposed by the three

  20. Physarum andinum, a new nivicolous species of myxomycete from the Patagonian Andes.

    PubMed

    Ronikier, Anna; Lado, Carlos

    2013-01-01

    A new nivicolous species of Physarum was discovered during the study of myxomycetes in the Patagonian Andes of South America. It is described herein under the name Physarum andinum. The species is characterized by stalked sporophores or more rarely sessile sporocarps or short plasmodiocarps. The sporocarps are strikingly large, reaching 2.6 mm tall and 3 mm diam when open, and have a peridium with three layers, the internal layer being clearly visible and opening separately. Physarum andinum was found at five localities in Argentina as well as in herbarium material collected about 100 y ago in Chile. The new species is reminiscent of the non-nivicolous species Physarum brunneolum, but the latter forms smaller sporophores, has darker spores and the three layers of the peridium are adhered and open together. The characters of the new species were examined under stereomicroscope, light microscope and scanning electron microscope and micrographs of relevant details are included.

  1. Impact of glaciations on the long-term erosion in Southern Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Simon-Labric, Thibaud; Herman, Frederic; Baumgartner, Lukas; Shuster, David L.; Braun, Jean; Reiners, Pete W.; Valla, Pierre G.; Leuthold, Julien

    2014-05-01

    The Southern Patagonian Andes are an ideal setting to study the impact of Late-Cenozoic climate cooling and onset of glaciations impact on the erosional history of mountain belts. The lack of tectonic activity during the last ~12 Myr makes the denudation history mainly controlled by surface processes, not by tectonics. Moreover, the glaciations history of Patagonia shows the best-preserved records within the southern hemisphere (with the exception of Antarctica). Indeed, the dry climate on the leeward side of Patagonia and the presence of lava flows interbedded with glacial deposits has allowed an exceptional preservation of late Cenozoic moraines with precise dating using K-Ar analyses on lava flow. The chronology of moraines reveals a long history covering all the Quaternary, Pliocene, and up to the Upper Miocene. The early growth of large glaciers flowing on eastern foothills started at ~7-6 Myr, while the maximum ice-sheet extent dates from approximately 1.1 Myr. In order to quantify the erosion history of the Southern Patagonian Andes and compare it to the glaciations sediment record, we collected samples along an age-elevation profile for low-temperature thermochronology in the eastern side of the mountain belt (Torres del Paine massif). The (U-Th)/He age-elevation relationship shows a clear convex shape providing an apparent long-term exhumation rate of ~0.2 km/Myr followed by an exhumation rate increase at ~6 Myr. Preliminary results of 4He/3He thermochronometry for a subset of samples complete the erosion history for the Plio-Pleistocene epoch. We used inverse procedure predicting 4He distributions within an apatite grain using a radiation-damage and annealing model to quantify He-diffusion kinetics in apatite. The model also allows quantifying the impact of potential U-Th zonation throughout each apatite crystal. Inversion results reveal a denudation history composed by a pulse of denudation at ~6 Ma, as suggested by the age-elevation relationship

  2. Satellite Observations of Mass Changes and Glacier Motions at the Patagonian Icefields, South America

    NASA Astrophysics Data System (ADS)

    Willis, M. J.; Melkonian, A. K.; Pritchard, M. E.; Ramage, J. M.

    2011-12-01

    The 4000 km2 Northern Patagonian Icefield (NPI), 13,000 km2 Southern Patagonian Icefield (SPI) and the 2500 km2 Cordillera Darwin Icefields (CDI) form the main ice bodies of the Patagonian Icefields of South America. Analysis of satellite imagery, derived digital elevation models (DEMs) and spaceborne laser altimetry confirm that each of the icefields is currently losing mass. The NPI lost mass at a rate of 3.40±0.07 Gt/yr between 2001 and 2011, equivalent to 0.009±0.0002 mm/yr of sea level rise. This contribution is a lower bound as we do not include sub-aqueous mass loss or area changes in our calculations. About 80% of the mass loss occurred from thinning over the ablation areas of the outlet glaciers of the icefield while the remaining ˜20% occurred at higher elevation above the equilibrium line altitude. Mass loss is especially concentrated at the low elevation southwestern and mid-western parts of the icefield. There, ice in the ablation zone approximately doubled in speed between 2007 and 2011. Passive microwave observations indicate that the glacier surface in these regions was "wet" for almost the entire study period. We suggest that the acceleration is linked to the reduction of friction at the bed of the glaciers via water making its way to the glacier sole. The glaciers that accelerated make up only a small proportion of the NPI and we find no evidence of accelerating mass loss from the NPI over the period considered. The SPI lost an average of 13.1±0.2 km3/yr of ice between 2001 and 2011. This rate is almost identical to previous studies, but the masks observations of rapidly accelerating thinning occuring at several of the outlet glaciers. Previous studies find that the peak rate of thinning at the HPS12 Glacier was ˜28 m/yr between 1995 and 2000. We find this slowed to 21±3 m/yr between 2000 and 2006, before accelerating to a rate of 57±13 m/yr between 2005 and 2011. Between 2000 and 2011 the HPS12 Glacier continued its rapid retreat, with the

  3. Detection of tides on the Patagonian shelf by the SEASAT satellite radar altimeter - An initial comparison

    NASA Technical Reports Server (NTRS)

    Parke, M. E.

    1980-01-01

    The detection of tides on the Patagonian shelf off Argentina by the SEASAT satellite radar altimeter is reported. The satellite data was obtained during two passes of the satellite over the shelf on August 1 and August 4, 1978, and compared with empirical estimates of the tidal elevation along the satellite ground tracks based on coastal tide gage data, an estimate of tidal variation over the shelf, and the tidal prediction equations of Shureman (1958). Good agreement was observed between the satellite data of sea surface height with respect to a standard ellipsoid and the empirical estimate for the near-shore pass, with agreement degraded slightly for the pass further off shore. It is concluded that the generally good agreement found demonstrates the applicability of satellite radar altimeter data to the determination of tides and that small length scale fluctuations in the geoid are minor along the two ground tracks.

  4. Trace metal concentrations in Spartina densiflora and associated soil from a Patagonian salt marsh.

    PubMed

    Idaszkin, Yanina L; Bouza, Pablo J; Marinho, Carmen H; Gil, Mónica N

    2014-12-15

    The objectives of this study were to (i) assess in situ trace metal concentrations in soil and in Spartina densiflora in a Patagonian salt marsh (Rawson, Chubut, Argentina) and (ii) investigate the relationship between trace metal concentrations in soils and in plants to improve our knowledge regarding the ability of S. densiflora to take up and accumulate trace metals from the soil within its native region. Our results indicate that the soil and S. densiflora exhibit low metal concentrations in the Rawson salt marsh. S. densiflora accumulates Zn in below- and above-ground plant structures and Cr in below-ground parts. These results suggest at the time of this study there is scarce human impact associated with metals in the Rawson salt marsh.

  5. Phenolic compounds as indicators of drought resistance in shrubs from Patagonian shrublands (Argentina).

    PubMed

    Varela, M Celeste; Arslan, Idris; Reginato, Mariana A; Cenzano, Ana M; Luna, M Virginia

    2016-07-01

    Plants exposed to drought stress, as usually occurs in Patagonian shrublands, have developed different strategies to avoid or tolerate the lack of water during their development. Production of phenolic compounds (or polyphenols) is one of the strategies used by some native species of adverse environments to avoid the oxidative damage caused by drought. In the present study the relationship between phenolic compounds content, water availability and oxidative damage were evaluated in two native shrubs: Larrea divaricata (evergreen) and Lycium chilense (deciduous) of Patagonian shrublands by their means and/or by multivariate analysis. Samples of both species were collected during the 4 seasons for the term of 1 year. Soil water content, relative water content, total phenols, flavonoids, flavonols, tartaric acid esters, flavan-3-ols, proanthocyanidins, antioxidant capacity and lipid peroxidation were measured. According to statistical univariate analysis, L. divaricata showed high production of polyphenols along the year, with a phenolic compound synthesis enhanced during autumn (season of greatest drought), while L. chilense has lower production of these compounds without variation between seasons. The variation in total phenols along the seasons is proportional to the antioxidant capacity and inversely proportional to lipid peroxidation. Multivariate analysis showed that, regardless their mechanism to face drought (avoidance or tolerance), both shrubs are well adapted to semi-arid regions and the phenolic compounds production is a strategy used by these species living in extreme environments. The identification of polyphenol compounds showed that L. divaricata produces different types of flavonoids, particularly bond with sugars, while L. chilense produces high amount of non-flavonoids compounds. These results suggest that flavonoid production and accumulation could be a useful indicator of drought tolerance in native species. Copyright © 2016 Elsevier Masson

  6. Recent geodetic mass balance of Monte Tronador glaciers, northern Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Ruiz, Lucas; Berthier, Etienne; Viale, Maximiliano; Pitte, Pierre; Masiokas, Mariano H.

    2017-02-01

    Glaciers in the northern Patagonian Andes (35-46° S) have shown a dramatic decline in area in the last decades. However, little is known about glacier mass balance changes in this region. This study presents a geodetic mass balance estimate of Monte Tronador (41.15° S; 71.88° W) glaciers by comparing a Pléiades digital elevation model (DEM) acquired in 2012 with the Shuttle Radar Topography Mission (SRTM) X-band DEM acquired in 2000. We find a slightly negative Monte-Tronador-wide mass budget of -0.17 m w.e. a-1 (ranging from -0.54 to 0.14 m w.e. a-1 for individual glaciers) and a slightly negative trend in glacier extent (-0.16 % a-1) over the 2000-2012 period. With a few exceptions, debris-covered valley glaciers that descend below a bedrock cliff are losing mass at higher rates, while mountain glaciers with termini located above this cliff are closer to mass equilibrium. Climate variations over the last decades show a notable increase in warm season temperatures in the late 1970s but limited warming afterwards. These warmer conditions combined with an overall drying trend may explain the moderate ice mass loss observed at Monte Tronador. The almost balanced mass budget of mountain glaciers suggests that they are probably approaching a dynamic equilibrium with current (post-1977) climate, whereas the valley glaciers tongues will continue to retreat. The slightly negative overall mass budget of Monte Tronador glaciers contrasts with the highly negative mass balance estimates observed in the Patagonian ice fields further south.

  7. Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield

    NASA Astrophysics Data System (ADS)

    Bertrand, S.; Hughen, K. A.; Lamy, F.; Stuut, J.-B. W.; Torrejón, F.; Lange, C. B.

    2011-09-01

    Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided in three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we demonstrate that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the Andes.

  8. Leafing patterns and leaf traits of four evergreen shrubs in the Patagonian Monte, Argentina

    NASA Astrophysics Data System (ADS)

    Campanella, María Victoria; Bertiller, Mónica B.

    2009-11-01

    We assessed leafing patterns (rate, timing, and duration of leafing) and leaf traits (leaf longevity, leaf mass per area and leaf-chemistry) in four co-occurring evergreen shrubs of the genus Larrea and Chuquiraga (each having two species) in the arid Patagonian Monte of Argentina. We asked whether species with leaves well-defended against water shortage (high LMA, leaf longevity, and lignin concentration, and low N concentration) have lower leaf production, duration of the leafing period, and inter-annual variation of leafing than species with the opposite traits. We observed two distinctive leafing patterns each related to one genus. Chuquiraga species produced new leaves concentrated in a massive short leafing event (5-48 days) while new leaves of Larrea species emerged gradually (128-258 days). Observed leafing patterns were consistent with simultaneous and successive leafing types previously described for woody plants. The peak of leaf production occurred earlier in Chuquiraga species (mid September) than in Larrea species (mid October-late November). Moreover, Chuquiraga species displayed leaves with the longest leaf lifespan, while leaves of Larrea species had the lowest LMA and the highest N and soluble phenolics concentrations. We also observed that only the leaf production of Larrea species increased in humid years. We concluded that co-occurring evergreen species in the Patagonian Monte displayed different leafing patterns, which were associated with some relevant leaf traits acting as plant defenses against water stress and herbivores. Differences in leafing patterns could provide evidence of ecological differentiation among coexisting species of the same life form.

  9. Seasonal change of phytoplankton (spring vs. summer) in the southern Patagonian shelf

    NASA Astrophysics Data System (ADS)

    Gonçalves-Araujo, Rafael; de Souza, Márcio Silva; Mendes, Carlos Rafael Borges; Tavano, Virginia Maria; Garcia, Carlos A. E.

    2016-08-01

    As part of the Patagonian Experiment (PATEX) project two sequential seasons (spring/summer 2007-2008) were sampled in the southern Patagonian shelf, when physical-chemical-biological (phytoplankton) data were collected. Phytoplankton biomass and community composition were assessed through both microscopic and high-performance liquid chromatography/chemical taxonomy (HPLC/CHEMTAX) techniques and related to both in situ and satellite data at spatial and seasonal scales. Phytoplankton seasonal variation was clearly modulated by water column thermohaline structure and nutrient dynamics [mainly dissolved inorganic nitrogen (DIN) and silicate]. The spring phytoplankton community showed elevated biomass and was dominated by diatoms [mainly Corethron pennatum and small (<20 μm) cells of Thalassiosira spp.], associated with a deeper and more weakly stratified upper mixed layer depth (UMLD) and relatively low nutrient concentrations, which were probably a result of consumption by the diatom bloom. In contrast, the phytoplankton community in summer presented lower biomass and was mainly dominated by haptophytes (primarily Emiliania huxleyi and Phaeocystis antarctica) and dinoflagellates, associated with shallower and well-stratified upper mixed layers with higher nutrient concentrations, likely due to lateral advection of nutrient-rich waters from the Malvinas Current. The gradual establishment of a strongly stratified and shallow UMLD as season progressed, was an important factor leading to the replacement of the spring diatom community by a dominance of calcifying organisms, as shown in remote sensing imagery and confirmed by microscopic examination. Furthermore, in spring, phaeopigments a (degradation products of chlorophyll a) relative to chlorophyll a, were twice that of summer, indicating the diatom bloom was under higher grazing pressure.

  10. Strike-slip faults in the southernmost Andes and the development of the Patagonian orocline

    NASA Astrophysics Data System (ADS)

    Cunningham, W. Dickson

    1993-02-01

    The Patagonian orocline is the 90° bend in the southernmost Andes between 50°S and 56°S. Paleomagnetic and structural data indicate that the orocline is, at least in part, the product of tectonic rotation. Recent field work in the Beagle Channel region of southernmost Chile provides evidence for widespread left-lateral strike-slip faulting in the internal zones of the mountain belt. Both arms of the Beagle Channel are interpreted to be left-lateral strike-slip faults based on detailed study of mesoscale strike-slip faults (Riedel shears) observed in coastal outcrops. Although much of the evidence indicates Cenozoic brittle strike-slip faulting, other fabric data, including vertical foliation zones containing horizontal quartz stretching lineations and ductile left-lateral kinematic indicators, suggest that Mesozoic ductile strike-slip or oblique-slip shearing also occurred. The implication is that the mid-Cretaceous Andean orogeny involved the transpressional inversion of the Rocas Verdes marginal basin and that transpression has been the dominant deformational regime in the region for the last 120 Ma. Regional left-lateral strike-slip faults are now recognized in all lithotectonic provinces of the southernmost Andes. A statistical study of regional lineament trends using aerial photographs and satellite imagery suggests that many unstudied lineaments are also strike-slip faults. A new model is proposed that integrates the development of strike-slip faulting and the structural evolution and uplift of the southernmost Andes with the rotational development of the orocline. The Patagonian orocline appears to be the product of broad interplate shearing accommodated by strike-slip faulting, block rotation, and contraction and is probably continuing to evolve today.

  11. Tracing dissolved organic matter (DOM) from land-based aquaculture systems in North Patagonian streams.

    PubMed

    Nimptsch, Jorge; Woelfl, Stefan; Osorio, Sebastian; Valenzuela, Jose; Ebersbach, Paul; von Tuempling, Wolf; Palma, Rodrigo; Encina, Francisco; Figueroa, David; Kamjunke, Norbert; Graeber, Daniel

    2015-12-15

    Chile is the second largest producer of salmonids worldwide. The first step in the production of salmonids takes place in land-based aquacultures. However, the effects of the discharge from these aquacultures on stream dissolved organic matter (DOM) content, molecular composition and degradability are unknown. The aim of this study was thus to investigate the inputs of anthropogenic DOM from land-based aquaculture to the predominantly pristine river systems of North Patagonia. We hypothesized, that i) DOM exported from land-based aquaculture mainly consists of protein-like fluorescence (tyrosine and tryptophan) released from fish feces and food remains, and that ii) this DOM is highly degradable and therefore rapidly turned-over within the receiving streams. In the North Patagonian region we conducted a screening of ten land-based aquacultures and an intensive sampling campaign for one aquaculture. This was combined with longitudinal transects and a degradation experiment in order to couple the composition of DOM exported from land-based aquacultures to its degradability in streams. We measured dissolved organic carbon (DOC) concentration by high-temperature catalytic oxidation and DOM composition by fluorescence spectroscopy and parallel factor analysis. In the effluent of the ten screened aquacultures and in the repeated sampling of one aquaculture, we consistently found an increase of DOC concentrations and a dominance of protein-like fluorescence. The protein-like fluorescence rapidly disappeared downstream of the aquacultures, and in the degradation experiment. 21% of the DOC export from the repeatedly sampled aquaculture resulted from food addition and 76% from fish production. We conclude that large amounts of degradable DOM are exported from land-based aquacultures. This probably has strong effects on the ecological structure and function of North Patagonian streams, and similarly affected streams worldwide. Copyright © 2015 Elsevier B.V. All rights

  12. Climate control on ancestral population dynamics: insight from Patagonian fish phylogeography.

    PubMed

    Ruzzante, Daniel E; Walde, Sandra J; Gosse, John C; Cussac, Victor E; Habit, Evelyn; Zemlak, Tyler S; Adams, Emily D M

    2008-05-01

    Changes in lake and stream habitats during the growth and retreat of Pleistocene glaciers repeatedly altered the spatial distributions and population sizes of the aquatic fauna of the southern Andes. Here, we use variation in mtDNA control region sequences to infer the temporal dynamics of two species of southern Andean fish during the past few million years. At least five important climate events were associated with major demographic changes: (i) the widespread glaciations of the mid-Pliocene (c. 3.5 Ma); (ii) the largest Patagonian glaciation (1.1 Ma); (iii) the coldest Pleistocene glaciation as indicated by stacked marine delta(18)O (c. 0.7 Ma); (iv) the last southern Patagonian glaciation to reach the Atlantic coast (180 ka); and (v) the last glacial maximum (LGM, 23-25,000 years ago). The colder-water inhabitant, Galaxias platei, underwent a strong bottleneck during the LGM and its haplotype diversity coalesces c. 0.7 Ma. In contrast, the more warm-adapted and widely distributed Percichthys trucha showed continuous growth through the last two glacial cycles but went through an important bottleneck c. 180,000 years ago, at which time populations east of the Andes may have been eliminated. Haplotype diversity of the most divergent P. trucha populations, found west of the Andes, coalesces c. 3.2 Ma. The demographic timelines obtained for the two species thus illustrate the continent-wide response of aquatic life in Patagonia to climate change during the Pleistocene, but also show how differing ecological traits and distributions led to distinctive responses.

  13. Historical seismicity

    USGS Publications Warehouse

    Dengler, L.

    1992-01-01

    The North Coast region of California in the vicinity of Cape Mendocino is one of the state's most seismically active areas, accounting for 25 percent of seismic energy release in California during the last 50 years. the region is located in a geologically dynamic are surrounding the Mendocino triple junction where three of the Earth's tectonic plates join together ( see preceding article by Sam Clarke). In the historic past the North Coast has been affected by earthquakes occurring on the San Andreas fault system to the south, the Mendocino fault to the southwest, and intraplate earthquakes within both the Gorda and North American plates. More than sixty of these earthquakes have caused damage since the mid-1800's. Recent studies indicate that California's North Coast is also at risk with respect to very large earthquakes (magnitude >8) originating along the Cascadia subduction zone. Although the subduction zone has not generated great earthquakes in historic time, paleoseismic evidence suggests that such earthquakes have been generated by the subduction zone in the recent prehistoric past. 

  14. Epidemiological studies on intestinal helminth parasites of the patagonian grey fox (Pseudalopex griseus) in Tierra del Fuego, Patagonia Argentina.

    PubMed

    Zanini, Fabián; Laferrara, Miguel; Bitsch, Matías; Pérez, Héctor; Elissondo, Maria Celina

    2006-03-31

    The present work was performed to study the intestinal helminths of the patagonian grey fox (Pseudalopex griseus) and to obtain information about its possible role in the sylvatic life cycle of Echinococcu granulosus in Tierra del Fuego, Patagonia Argentina. Eighty-one foxes were captured and subject to post-mortem analysis. Thirty-one foxes (38.3%) harboured helminths. A total of six helminth species were recovered. Only one adult of E. granulosus was found in the studied samples. The current study is the first report of the intestinal helminths of the patagonian grey fox in Tierra del Fuego, Argentina and showed that this specie is probably not an important reservoir host for E. granulosus.

  15. Seafood Substitutions Obscure Patterns of Mercury Contamination in Patagonian Toothfish (Dissostichus eleginoides) or “Chilean Sea Bass”

    PubMed Central

    Marko, Peter B.; Nance, Holly A.; van den Hurk, Peter

    2014-01-01

    Seafood mislabeling distorts the true abundance of fish in the sea, defrauds consumers, and can also cause unwanted exposure to harmful pollutants. By combining genetic data with analyses of total mercury content, we have investigated how species substitutions and fishery-stock substitutions obscure mercury contamination in Patagonian toothfish (Dissostichus eleginoides), also known as “Chilean sea bass”. Patagonian toothfish show wide variation in mercury concentrations such that consumers may be exposed to either acceptable or unacceptable levels of mercury depending on the geographic origins of the fish and the allowable limits of different countries. Most notably, stocks of Patagonian toothfish in Chile accumulate significantly more mercury than stocks closer to the South Pole, including the South Georgia/Shag Rocks stock, a fishery certified by the Marine Stewardship Council (MSC) as sustainably fished. Consistent with the documented geography of mercury contamination, our analysis showed that, on average, retail fish labeled as MSC-certified Patagonian toothfish had only half the mercury of uncertified fish. However, consideration of genetic data that were informative about seafood substitutions revealed a complex pattern of contamination hidden from consumers: species substitutions artificially inflated the expected difference in mercury levels between MSC-certified and uncertified fish whereas fishery stock substitutions artificially reduced the expected difference in mercury content between MSC-certified and uncertified fish that were actually D. eleginoides. Among MSC-certified fish that were actually D. eleginoides, several with exogenous mtDNA haplotypes (i.e., not known from the certified fishery) had mercury concentrations on par with uncertified fish from Chile. Overall, our analysis of mercury was consistent with inferences from the genetic data about the geographic origins of the fish, demonstrated the potential negative impact of seafood

  16. Pleistocene refugia and polytopic replacement of diploids by tetraploids in the Patagonian and Subantarctic plant Hypochaeris incana (Asteraceae, Cichorieae).

    PubMed

    Tremetsberger, Karin; Urtubey, Estrella; Terrab, Anass; Baeza, Carlos M; Ortiz, María Angeles; Talavera, María; König, Christiane; Temsch, Eva M; Kohl, Gudrun; Talavera, Salvador; Stuessy, Tod F

    2009-09-01

    We report the phylogeographic pattern of the Patagonian and Subantarctic plant Hypochaeris incana endemic to southeastern South America. We applied amplified fragment length polymorphism (AFLP) and chloroplast DNA (cpDNA) analysis to 28 and 32 populations, respectively, throughout its distributional range and assessed ploidy levels using flow cytometry. While cpDNA data suggest repeated or simultaneous parallel colonization of Patagonia and Tierra del Fuego by several haplotypes and/or hybridization, AFLPs reveal three clusters corresponding to geographic regions. The central and northern Patagonian clusters (approximately 38-51 degrees S), which are closer to the outgroup, contain mainly tetraploid, isolated and highly differentiated populations with low genetic diversity. To the contrary, the southern Patagonian and Fuegian cluster (approximately 51-55 degrees S) contains mainly diploid populations with high genetic diversity and connected by high levels of gene flow. The data suggest that H. incana originated at the diploid level in central or northern Patagonia, from where it migrated south. All three areas, northern, central and southern, have similar levels of rare and private AFLP bands, suggesting that all three served as refugia for H. incana during glacial times. In southern Patagonia and Tierra del Fuego, the species seems to have expanded its populational system in postglacial times, when the climate became warmer and more humid. In central and northern Patagonia, the populations seem to have become restricted to favourable sites with increasing temperature and decreasing moisture and there was a parallel replacement of diploids by tetraploids in local populations.

  17. Taxonomic review of the species of Helina R.-D. (Diptera: Muscidae) from Andean-Patagonian forests.

    PubMed

    Patitucci, Luciano Damián; Mulieri, Pablo Ricardo; Mariluis, Juan Carlos

    2016-08-12

    Helina Robineau-Desvoidy, 1830 is the second genus of Muscidae in terms of richness. This genus includes several species collected at high altitudes and high latitudes, and is poorly studied in the Neotropical region. Only 12 species of Helina have been recorded in the southern limit of South America in the Andean-Patagonian forests. In the present work, we studied all the species known from the Andean-Patagonian forests, with the exception of H. viola Malloch, 1934, present three new species, H. araucana sp. nov., H. dorada sp. nov., and H. ouina sp. nov., and provide the first description of the females of H. australis Carvalho & Pont, 1993 and H. rufoapicata Malloch, 1934. We also propose four new synonymies: H. nigrimana basilaris (Carvalho & Pont, 1993) and H. nigrimana grisea (Malloch, 1934) as new junior synonyms of H. nigrimana (Macquart, 1851); and H. fulvocalyptrata Malloch, 1934 and H. simplex Malloch, 1934 as new junior synonyms of H. chilensis Malloch, 1934. Finally, we provide a generic diagnosis and a new key for the Helina species of the Andean-Patagonian forests, as well as notes on the biology and distribution maps of each specimen, and discuss a preliminary contruction of groups of species.

  18. Understanding the Transport of Patagonian Dust and Its Influence on Marine Biological Activity in the South Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Johnson, Matthew; Meskhidze, Nicholas; Kiliyanpilakkil, Praju; Gasso, Santiago

    2010-01-01

    Modeling and remote sensing techniques were applied to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of soluble-iron- laden mineral dust deposition on marine primary productivity in the South Atlantic Ocean (SAO) surface waters. The global chemistry transport model GEOS-Chem, implemented with an iron dissolution scheme, was applied to evaluate the atmospheric transport and deposition of mineral dust and bioavailable iron during two dust outbreaks originating in the source regions of Patagonia. In addition to this "rapidly released" iron, offline calculations were also carried out to estimate the amount of bioavailable iron leached during the residence time of dust in the ocean mixed layer. Model simulations showed that the horizontal and vertical transport pathways of Patagonian dust plumes were largely influenced by the synoptic meteorological patterns of high and low pressure systems. Model-predicted horizontal and vertical transport pathways of Patagonian dust over the SAO were in reasonable agreement with remotely-sensed data. Comparison between remotely-sensed and offline calculated ocean surface chlorophyll-a concentrations indicated that, for the two dust outbreaks examined in this study, the deposition of bioavailable iron in the SAO through atmospheric pathways was insignificant. As the two dust transport episodes examined here represent typical outflows of mineral dust from South American sources, our study suggests that the atmospheric deposition of mineral dust is unlikely to induce large scale marine primary productivity and carbon sequestration in the South Atlantic sector of the Southern Ocean.

  19. Seismic sources

    DOEpatents

    Green, M.A.; Cook, N.G.W.; McEvilly, T.V.; Majer, E.L.; Witherspoon, P.A.

    1987-04-20

    Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Longitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements for more than about one minute. 9 figs.

  20. Alkaline lavas from southern Mendoza, Argentina, extend the Patagonian DUPAL mantle field to the north

    NASA Astrophysics Data System (ADS)

    Soager, N.; Holm, P. M.; Llambias, E.

    2010-12-01

    The lavas sampled around Río Colorado ~37°S at the border of Mendoza and Neuquén provinces, Argentina, define an OIB-like end-member composition for the Pleistocene and Holocene activity in the Payún Matrú volcanic field. Although positioned in the far back-arc of the Andes, only a few lavas show signs of involvement of slab fluids or crustal contamination such as relatively high LILEs relative to Nb. The very low La/Nb (~0.66) and Zr/Nb (~5) and high U/Pb (0.3-0.4) of the end-member composition clearly distinguish the source from normal MORB mantle, while high Ba/Nb (~10) and K/Nb (370-400) compared to FOZO and HIMU type OIBs suggest an EM type of mantle. Overall, the trace element patterns of the Río Colorado lavas are similar to the central and north Patagonian intraplate basalts and to South Atlantic E-MORB affected by the Discovery plume and the LOMU component (le Roux et al., 2002, EPSL 203). The isotopic composition of the Río Colorado component has a 206Pb/204Pb = 18.4, 207Pb/204Pb = 15.58, 208Pb/204Pb = 38.3, 87Sr/86Sr = 0.70353 and 143Nd/144Nd = 0.51285. This composition overlaps the central and north Patagonian intraplate basalts in Pb-isotopic space but is slightly less enriched in Sr and Nd-isotopes. It is distinctly different from the FOZO like composition of the south Patagonian intraplate basalts and the nearby Juan Fernandéz plume but similar to the South Atlantic N-MORB and MORB from the southern Chile Ridge segment 4 (Sturm et al., 1999, JGR 104) described as DUPAL type. The DUPAL-MORB type isotopic composition and the plume-like trace element patterns of the Río Colorado lavas suggest the presence of a weak plume beneath the area. The eruption of the large Payún Matrú volcano and the gigantic Pleistocene flood basalts also calls for a thermal anomaly to produce these melts during a weakly compressive tectonic regime with no significant addition of slab fluids. This was supported by Burd et al. (2008, Abstr., 7th Int. Sym. And. Geo

  1. Effects of Solar Radiation on the Patagonian Rhodophyte Corallina officinatis (L.).

    PubMed

    Häder, Donat-P; Lebert, Michael; Walter Helbling, E

    2003-01-01

    Experiments were conducted in Patagonian waters (Argentina) to assess the impact of solar radiation (PAR, 400-700 nm, and UVR, 280-400 nm) upon two strains of the red alga Corallina officinalis Linnaeus, characteristic of the mid and lower intertidal zone, during March 2000. Fluorescence parameters were determined using a pulse amplitude modulated (PAM) fluorometer. The two strains had different initial optimal quantum yields but similar strong decreases in the quantum yield when the algae were exposed to short-term solar radiation and similar recovery characteristics in dim light. The quantum yield had the lowest values at noon, but it increased in the afternoon / evening hours, when irradiances were lower. PAR (irradiance at noon about 500 W m(-2)) was responsible for most of the decrease in the yield ( approximately 50%) on clear days, with UVR accounting for a significant increment. However, on cloudy days the UVR component caused an even more pronounced decrease. In their natural environment, specimens in the shade had a higher effective quantum yield than in sun-lit areas. Fluence rate response curves indicated that thalli from the mid intertidal had a pronounced nonphotochemical quenching at intermediate and higher irradiances; however, this was not observed in the thalli from the lower intertidal. Fast induction and relaxation kinetics showed obvious differences between the two strains, but also demonstrated a rapid adaptation of the species to the changing light conditions as well as a fast decrease of PS II fluorescence upon exposure to solar radiation. All photosynthetic pigments were bleached during exposure to solar radiation over a full day. Strong absorption in the UV-A range, most likely due to mycosporine like amino acids, was determined in both strains. The study of the differential sensitivity to solar radiation and recovery capacity of these Corallina strains, as well as the presence of protective compounds, suggests that a combination of

  2. Didymosphenia geminata invasion in South America: Ecosystem impacts and potential biogeochemical state change in Patagonian rivers

    NASA Astrophysics Data System (ADS)

    Reid, Brian; Torres, Rodrigo

    2014-01-01

    The diatom Didymosphenia geminata has emerged as a major global concern, as both an aggressive invader of rivers and streams in the southern hemisphere, and for its ability to form nuisance blooms in oligotrophic systems in its native range. South American D. geminata blooms were first documented in Chilean Patagonia in May 2010, and have spread to over five regions and three provinces, in Chile and Argentina respectively. The Patagonian invasion represents a distinct challenge compared to other regions; not only are affected systems poorly characterized, but also a general synthesis of the nature and magnitude of ecosystem impacts is still lacking. The latter is essential in evaluating impacts to ecosystem services, forms the basis for a management response that is proportional to the potentially valid threats, or aids in the determination of whether action is warranted or feasible. Based on a revision of the recent literature, some of the most significant impacts may be mediated through physical changes: substantially increased algal biomass, trapping of fine sediment, altered hydrodynamics, and consequent effects on biogeochemical states and processes such as redox condition, pH and nutrient cycling in the benthic zone. Surveys conducted during the early invasion in Chile show a strong correlation between benthic biomass and associated fine sediments, both of which were one-two orders of magnitude higher within D. geminata blooms. Experimental phosphorous amendments showed significant abiotic uptake, while interstitial water in D. geminata mats had nearly 10-20 fold higher soluble reactive phosphorous and a pronounced pH cycle compared to the water column. A dominant and aggressive stalk-forming diatom with this combination of characteristics is in sharp contrast to the colonial cyanobacteria and bare gravel substrate that characterize many Patagonian streams. The potential displacement of native benthic algal communities with contrasting functional groups

  3. Magnetic signatures of the orogenic crust of the Patagonian Andes with implication for planetary exploration

    NASA Astrophysics Data System (ADS)

    Díaz Michelena, Marina; Kilian, Rolf

    2015-11-01

    The Patagonian Andes represent a good scenario of study because they have outcrops of diverse plutonic rocks representative of an orogenic crust on Earth and other planets. Furthermore, metamorphic surface rocks provide a window into deeper crustal lithologies. In such remote areas, satellite and aerial magnetic surveys could provide important geological information concerning exposed and not exposed rocks, but they integrate the magnetic anomalies in areas of kilometres. For the southernmost Andes long wavelength satellite data show clear positive magnetic anomalies (>+100 nT) for the Patagonian Batholith (PB), similar as parts of the older martian crust. This integrated signal covers regions with different ages and cooling histories during magnetic reversals apart from the variability of the rocks. To investigate the complex interplay of distinct magnetic signatures at short scale, we have analysed local magnetic anomalies across this orogen at representative sites by decimeter-scale magnetic ground surveys. As expected, the investigated sites have positive and negative local anomalies. They are related to surface and subsurface rocks, and their different formation and alternation processes including geomagnetic inversions, distinct Curie depths of the magnetic carriers, intracrustal deformation among other factors. Whole rock chemistry (ranging from 45 to >80 wt.% SiO2 and from 1 to 18 wt.% FeOtot.), magnetic characteristics (susceptibilities, magnetic remanence and Königsberger ratios) as well as the composition and texture of the magnetic carriers have been investigated for representative rocks. Rocks of an ultramafic to granodioritic intrusive suite of the western and central PB contain titanomagnetite as major magnetic carrier. Individual magnetic signatures of these plutonic rocks reflect their single versus multidomain status, complex exolution processes with ilmenite lamella formations and the stoichiometric proportions of Cr, Fe and Ti in the oxides. At

  4. Seismic sources

    DOEpatents

    Green, Michael A.; Cook, Neville G. W.; McEvilly, Thomas V.; Majer, Ernest L.; Witherspoon, Paul A.

    1992-01-01

    Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Logitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole relative to a stator that is clamped to the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements at a power level that causes heating to over 150.degree. C. within one minute of operation, but energizing the elements for no more than about one minute.

  5. Active seismic experiment

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.; Watkins, J. S.; Talwani, P.

    1972-01-01

    The Apollo 16 active seismic experiment (ASE) was designed to generate and monitor seismic waves for the study of the lunar near-surface structure. Several seismic energy sources are used: an astronaut-activated thumper device, a mortar package that contains rocket-launched grenades, and the impulse produced by the lunar module ascent. Analysis of some seismic signals recorded by the ASE has provided data concerning the near-surface structure at the Descartes landing site. Two compressional seismic velocities have so far been recognized in the seismic data. The deployment of the ASE is described, and the significant results obtained are discussed.

  6. Ecological Status of a Patagonian Mountain River: Usefulness of Environmental and Biotic Metrics for Rehabilitation Assessment

    NASA Astrophysics Data System (ADS)

    Laura, Miserendino M.; Adriana, M. Kutschker; Cecilia, Brand; La Ludmila, Manna; Cecilia, Prinzio Y. Di; Gabriela, Papazian; José, Bava

    2016-06-01

    This work evaluates the consequences of anthropogenic pressures at different sections of a Patagonian mountain river using a set of environmental and biological measures. A map of risk of soil erosion at a basin scale was also produced. The study was conducted at 12 sites along the Percy River system, where physicochemical parameters, riparian ecosystem quality, habitat condition, plants, and macroinvertebrates were investigated. While livestock and wood collection, the dominant activities at upper and mean basin sites resulted in an important loss of the forest cover still the riparian ecosystem remains in a relatively good status of conservation, as do the in-stream habitat conditions and physicochemical features. Besides, most indicators based on macroinvertebrates revealed that both upper and middle basin sections supported similar assemblages, richness, density, and most functional feeding group attributes. Instead, the lower urbanized basin showed increases in conductivity and nutrient values, poor quality in the riparian ecosystem, and habitat condition. According to the multivariate analysis, ammonia level, elevation, current velocity, and habitat conditions had explanatory power on benthos assemblages. Discharge, naturalness of the river channel, flood plain morphology, conservation status, and percent of urban areas were important moderators of plant composition. Finally, although the present land use in the basin would not produce a significant risk of soil erosion, unsustainable practices that promotes the substitution of the forest for shrubs would lead to severe consequences. Mitigation efforts should be directed to protect headwater forest, restore altered riparian ecosystem, and to control the incipient eutrophication process.

  7. Ecological Status of a Patagonian Mountain River: Usefulness of Environmental and Biotic Metrics for Rehabilitation Assessment.

    PubMed

    Laura, Miserendino M; Adriana, M Kutschker; Cecilia, Brand; La Ludmila, Manna; Cecilia, Prinzio Y Di; Gabriela, Papazian; José, Bava

    2016-06-01

    This work evaluates the consequences of anthropogenic pressures at different sections of a Patagonian mountain river using a set of environmental and biological measures. A map of risk of soil erosion at a basin scale was also produced. The study was conducted at 12 sites along the Percy River system, where physicochemical parameters, riparian ecosystem quality, habitat condition, plants, and macroinvertebrates were investigated. While livestock and wood collection, the dominant activities at upper and mean basin sites resulted in an important loss of the forest cover still the riparian ecosystem remains in a relatively good status of conservation, as do the in-stream habitat conditions and physicochemical features. Besides, most indicators based on macroinvertebrates revealed that both upper and middle basin sections supported similar assemblages, richness, density, and most functional feeding group attributes. Instead, the lower urbanized basin showed increases in conductivity and nutrient values, poor quality in the riparian ecosystem, and habitat condition. According to the multivariate analysis, ammonia level, elevation, current velocity, and habitat conditions had explanatory power on benthos assemblages. Discharge, naturalness of the river channel, flood plain morphology, conservation status, and percent of urban areas were important moderators of plant composition. Finally, although the present land use in the basin would not produce a significant risk of soil erosion, unsustainable practices that promotes the substitution of the forest for shrubs would lead to severe consequences. Mitigation efforts should be directed to protect headwater forest, restore altered riparian ecosystem, and to control the incipient eutrophication process.

  8. Torpor in the Patagonian opossum ( Lestodelphys halli): implications for the evolution of daily torpor and hibernation

    NASA Astrophysics Data System (ADS)

    Geiser, Fritz; Martin, Gabriel M.

    2013-10-01

    Hibernation and daily torpor are two distinct forms of torpor, and although they are related, it is not known how and in which sequence they evolved. As the pattern of torpor expressed by the oldest marsupial order the opossums (Didelphimorphia) may provide insights into the evolution of torpor, we aimed to provide the first quantitative data on the thermal biology and torpor expression of the rare Patagonian opossum ( Lestodelphys halli). It is the opossum with the southernmost distribution, has a propensity of autumnal fattening, and therefore, is likely to hibernate. We captured two male Lestodelphys, which while in captivity displayed strong daily fluctuations of body temperatures (Tb) measured with implanted miniature data loggers even when they remained normothermic. In autumn and early winter, torpor was expressed occasionally when food was available, but cold exposure and food withdrawal increased torpor use. The mean Tb throughout the study was 32.2 ± 1.4 °C, the minimum Tb measured in torpid Lestodelphys was 7.7 °C, average torpor bout duration was 10.3 h, and the maximum torpor bout duration was 42.5 h. Thus, the pattern of torpor expressed by Lestodelphys was intermediate between that of daily heterotherms and hibernators suggesting that it may represent an ancestral opportunistic torpor pattern from which the derived patterns of daily torpor and seasonal hibernation diverged.

  9. Spatial Models of Abundance and Habitat Preferences of Commerson's and Peale's Dolphin in Southern Patagonian Waters.

    PubMed

    Dellabianca, Natalia A; Pierce, Graham J; Raya Rey, Andrea; Scioscia, Gabriela; Miller, David L; Torres, Mónica A; Paso Viola, M Natalia; Goodall, R Natalie P; Schiavini, Adrián C M

    2016-01-01

    Commerson's dolphins (Cephalorhynchus c. commersonii) and Peale's dolphins (Lagenorhynchus australis) are two of the most common species of cetaceans in the coastal waters of southwest South Atlantic Ocean. Both species are listed as Data Deficient by the IUCN, mainly due to the lack of information about population sizes and trends. The goal of this study was to build spatially explicit models for the abundance of both species in relation to environmental variables using data collected during eight scientific cruises along the Patagonian shelf. Spatial models were constructed using generalized additive models. In total, 88 schools (212 individuals) of Commerson's dolphin and 134 schools (465 individuals) of Peale's dolphin were recorded in 8,535 km surveyed. Commerson's dolphin was found less than 60 km from shore; whereas Peale's dolphins occurred over a wider range of distances from the coast, the number of animals sighted usually being larger near or far from the coast. Fitted models indicate overall abundances of approximately 22,000 Commerson's dolphins and 20,000 Peale's dolphins in the total area studied. This work provides the first large-scale abundance estimate for Peale's dolphin in the Atlantic Ocean and an update of population size for Commerson's dolphin. Additionally, our results contribute to baseline data on suitable habitat conditions for both species in southern Patagonia, which is essential for the implementation of adequate conservation measures.

  10. Environmental Quality and Aquatic Invertebrate Metrics Relationships at Patagonian Wetlands Subjected to Livestock Grazing Pressures

    PubMed Central

    2015-01-01

    Livestock grazing can compromise the biotic integrity and health of wetlands, especially in remotes areas like Patagonia, which provide habitat for several endemic terrestrial and aquatic species. Understanding the effects of these land use practices on invertebrate communities can help prevent the deterioration of wetlands and provide insights for restoration. In this contribution, we assessed the responses of 36 metrics based on the structural and functional attributes of invertebrates (130 taxa) at 30 Patagonian wetlands that were subject to different levels of livestock grazing intensity. These levels were categorized as low, medium and high based on eight features (livestock stock densities plus seven wetland measurements). Significant changes in environmental features were detected across the gradient of wetlands, mainly related to pH, conductivity, and nutrient values. Regardless of rainfall gradient, symptoms of eutrophication were remarkable at some highly disturbed sites. Seven invertebrate metrics consistently and accurately responded to livestock grazing on wetlands. All of them were negatively related to increased levels of grazing disturbance, with the number of insect families appearing as the most robust measure. A multivariate approach (RDA) revealed that invertebrate metrics were significantly affected by environmental variables related to water quality: in particular, pH, conductivity, dissolved oxygen, nutrient concentrations, and the richness and coverage of aquatic plants. Our results suggest that the seven aforementioned metrics could be used to assess ecological quality in the arid and semi-arid wetlands of Patagonia, helping to ensure the creation of protected areas and their associated ecological services. PMID:26448652

  11. Effects of future sea-level rise on tidal processes on the Patagonian Shelf

    NASA Astrophysics Data System (ADS)

    Carless, Stacey J.; Green, J. A. Mattias; Pelling, Holly E.; Wilmes, Sophie-Berenice

    2016-11-01

    The response of tidally driven processes on the Patagonian Shelf to sea-level rise (SLR) is revisited using large but realistic levels of change in a numerical tidal model. The results relate to previous studies through significant differences in the impact, depending on how SLR is implemented. This is true for how the boundary at the coastline is treated, i.e., if we allow for inundation of land or assume flood defences along the coast, but also for how the sea-level change itself is implemented. Simulations with uniform SLR provide a different, and slightly larger, response than do runs where SLR is based on observed trends. In all cases, the effect on the tidal amplitudes is patchy, with alternating increases and decreases in amplitude along the shelf. Furthermore, simulations with a realistic future change in vertical stratification, thus affecting tidal conversion rates, imply that there may be a small but significant decrease in the amplitudes along the coast. Associated processes, e.g., the location of mixing fronts and potential impacts on biogeochemical cycles on the shelf are also discussed.

  12. Environmental Quality and Aquatic Invertebrate Metrics Relationships at Patagonian Wetlands Subjected to Livestock Grazing Pressures.

    PubMed

    Epele, Luis Beltrán; Miserendino, María Laura

    2015-01-01

    Livestock grazing can compromise the biotic integrity and health of wetlands, especially in remotes areas like Patagonia, which provide habitat for several endemic terrestrial and aquatic species. Understanding the effects of these land use practices on invertebrate communities can help prevent the deterioration of wetlands and provide insights for restoration. In this contribution, we assessed the responses of 36 metrics based on the structural and functional attributes of invertebrates (130 taxa) at 30 Patagonian wetlands that were subject to different levels of livestock grazing intensity. These levels were categorized as low, medium and high based on eight features (livestock stock densities plus seven wetland measurements). Significant changes in environmental features were detected across the gradient of wetlands, mainly related to pH, conductivity, and nutrient values. Regardless of rainfall gradient, symptoms of eutrophication were remarkable at some highly disturbed sites. Seven invertebrate metrics consistently and accurately responded to livestock grazing on wetlands. All of them were negatively related to increased levels of grazing disturbance, with the number of insect families appearing as the most robust measure. A multivariate approach (RDA) revealed that invertebrate metrics were significantly affected by environmental variables related to water quality: in particular, pH, conductivity, dissolved oxygen, nutrient concentrations, and the richness and coverage of aquatic plants. Our results suggest that the seven aforementioned metrics could be used to assess ecological quality in the arid and semi-arid wetlands of Patagonia, helping to ensure the creation of protected areas and their associated ecological services.

  13. Tolerance to winemaking stress conditions of Patagonian strains of Saccharomyces eubayanus and Saccharomyces uvarum.

    PubMed

    Origone, A C; Del Mónaco, S M; Ávila, J R; González Flores, M; Rodríguez, M E; Lopes, C A

    2017-08-01

    Evaluating the winemaking stress tolerance of a set of both Saccharomyces eubayanus and Saccharomyces uvarum strains from diverse Patagonian habitats. Yeast strains growth was analysed under increasing ethanol concentrations; all of them were able to grow until 8% v/v ethanol. The effect of different temperature and pH conditions as well as at SO2 and hexose concentrations was evaluated by means of a central composite experimental design. Only two S. uvarum strains (NPCC 1289 and 1321) were able to grow in most stress conditions. Kinetic parameters analysed (μmax and λ) were statistically affected by temperature, pH and SO2 , but not influenced by sugar concentration. The obtained growth model was used for predicting optimal growth conditions for both strains: 20°C, 0% w/v SO2 and pH 4·5. Strains from human-associated environments (chichas) presented the highest diversity in the response to different stress factors. Two S. uvarum strains from chichas demonstrated to be the most tolerant to winemaking conditions. This work evidenced the potential use of two S. uvarum yeast strains as starter cultures in wines fermented at low temperatures. Saccharomyces eubayanus was significantly affected by winemaking stress conditions, limiting its use in this industry. © 2017 The Society for Applied Microbiology.

  14. A histopathological survey of the razor clam Ensis macha (Pharidae) along the Patagonian Argentina coast.

    PubMed

    Vázquez, Nuria; Bruno, Elizabeth Perez; Márquez, Federico; Van der Molen, Silvina; Gilardoni, Carmen; Cremonte, Florencia

    2013-03-01

    This is the first study performed to determine the health status of the razor clam, Ensis macha, including six different populations along Argentina Patagonian coast and one of Chile. The parasites and pathologies affecting E. macha were analyzed and their prevalence and mean intensity values were calculated. To establish which factors affect the presence and intensity of infection, Generalized Linear Models (GLMs) were applied. Basophilic inclusions, ciliates, coccidians protozoans and turbellarians were found. We report an Aporocotylidae digenean and hemocyte infiltrations. None of the parasites is OIE (World Organisation for Animal Health) notifiable, and none seemed to be pathogenic, with the exception of the digenean. The prevalence of the parasites was affected mainly by environmental factors (such as site of sampling and season) instead of intrinsic conditions of the clam (such as size, condition index, sex and gonadal stage). On the other hand, the maximum intensity of parasites was not only related with cold seasons but also with the partially spawned gonadal stage of E. macha. During this stage, the clams would need to store energy for the next gametogenesis cycle, might be more susceptible to infection by the parasites.

  15. The impact of predation by marine mammals on patagonian toothfish longline fisheries.

    PubMed

    Söffker, Marta; Trathan, Phil; Clark, James; Collins, Martin A; Belchier, Mark; Scott, Robert

    2015-01-01

    Predatory interaction of marine mammals with longline fisheries is observed globally, leading to partial or complete loss of the catch and in some parts of the world to considerable financial loss. Depredation can also create additional unrecorded fishing mortality of a stock and has the potential to introduce bias to stock assessments. Here we aim to characterise depredation in the Patagonian toothfish (Dissostichus eleginoides) fishery around South Georgia focusing on the spatio-temporal component of these interactions. Antarctic fur seals (Arctocephalus gazella), sperm whales (Physeter macrocephalus), and orcas (Orcinus orca) frequently feed on fish hooked on longlines around South Georgia. A third of longlines encounter sperm whales, but loss of catch due to sperm whales is insignificant when compared to that due to orcas, which interact with only 5% of longlines but can take more than half of the catch in some cases. Orca depredation around South Georgia is spatially limited and focused in areas of putative migration routes, and the impact is compounded as a result of the fishery also concentrating in those areas at those times. Understanding the seasonal behaviour of orcas and the spatial and temporal distribution of "depredation hot spots" can reduce marine mammal interactions, will improve assessment and management of the stock and contribute to increased operational efficiency of the fishery. Such information is valuable in the effort to resolve the human-mammal conflict for resources.

  16. Xanthophyllomyces dendrorhous (Phaffia rhodozyma) on stromata of Cyttaria hariotii in northwestern Patagonian Nothofagus forests.

    PubMed

    Libkind, Diego; Tognetti, Celia; Ruffini, Alejandra; Sampaio, José Paulo; Van Broock, María

    2011-01-01

    The occurrence and distribution of Xanthophyllomyces dendrorhous associated with Cyttaria hariotii parasitizing three Nothofagus species (N. dombeyi, N. antarctica and N. pumilio) in northwestern Patagonia (Argentina), as well as the factors that may affect this distribution were herein studied. Between 2000 and 2007, samples were obtained from 18 different locations. Based on physiological tests and morphological characteristics of sexual structures, 72 isolates were identified as X. dendrorhous. Representative strains were studied by MSP-PCR fingerprinting and sequence analysis of the ITS region. MSP-PCR fingerprints were similar for the newly isolated strains, and were also identical to the profiles of the strains previously found in this region. Patagonian strains appear to be a genetically uniform and distinct population, supporting the hypothesis that the association with different host species has determined genetically distinct X. dendrorhous populations worldwide. X. dendrorhous was recovered from N. dombeyi and N. antarctica. Approximately half the sampling sites and samples were positive for X. dendrorhous, but the isolation recovery rate was low. X. dendrorhous was absent in the early stages of ascostromata maturation, becoming more abundant in later stages. The present work represents a step forward in the understanding of the natural distribution and ecology of this biotechnologically relevant yeast.

  17. The impact of Andean Patagonian mycoflora in the search for new lead molecules.

    PubMed

    Aqueveque, Pedro M; Cespedes, Carlos L; Kubo, Isao; Seigler, David S; Sterner, Olov

    2017-08-01

    Secondary metabolites from fungi have become a major source of chemical innovation in programs searching for lead molecules with bioactivities, especially over the last 50 years. In this review, we discuss the fundamental considerations in the discovery of molecules for agricultural and medicinal uses. This group of organisms possesses a strong potential for scientific and industrial communities. Recently, the incorporation of new technologies for the artificial cultivation of fungi and the use of better equipment to isolate and identify active metabolites has allowed the discovery of leading molecules for the design of new and safer drugs and pesticides. The geographical region including the Patagonian Andes mountains harbors a wide diversity of fungi, many of them still unknown and so far associated with Chilean-Argentinian Andean endemic forests. There have been very few chemical studies of the fungi located in this region. However, those few studies have allowed the discovery of new molecules. We argue that the richness of fungal biodiversity in this region offers an interesting source for the discovery of bioactive molecules for the basic and applied sciences. © 2017 New York Academy of Sciences.

  18. Postglacial formation and dynamics of North Patagonian Rainforest in the Chonos Archipelago, Southern Chile

    NASA Astrophysics Data System (ADS)

    Haberle, S. G.; Bennett, K. D.

    2004-12-01

    Pollen analysis of continuous sediment cores from two lakes in the northern Chonos Archipelago (44°S) in southern Chile shows a complete postglacial record of vegetation change. The fossil records indicate that deglaciation was complete in the northern Chonos by at least 13,600 14C yr BP. Ericaceous heath and grassland persisted for more than 600 years after deglaciation under the influence of dry/cold climates and frequent burning. Nothofagus- Pilgerodendron- Podocarpus forest, with modern analogues in the southern Chonos Archipelago, was established across the northern islands by 12,400 14C yr BP under increasingly warm and wet climates. There is no evidence for a return to cooler climates during the Younger Dryas chronozone. The rise of Tepualia stipularis and Weinmannia trichosperma as important forest components between 10,600 and 6000 14C yr BP may be associated with climates that were warmer than present. The collapse of Pilgerodendron communities during this time may have been triggered by a combination of factors related to disturbance frequency including tephra deposition events, fire and climate change. After 6000 14C yr BP Pilgerodendron recovers and Nothofagus-Pilgerodendron-Tepualia forest persists until the present. European logging and burning activity may have increased the susceptibility of North Patagonian Rainforest to invasion by introduced species and to future collapse of the long-lived Pilgerodendron communities.

  19. Ultraviolet radiation induces filamentation in bacterial assemblages from North Andean Patagonian lakes.

    PubMed

    Modenutti, Beatriz; Balseiro, Esteban; Corno, Gianluca; Callieri, Cristiana; Bertoni, Roberto; Caravati, Emanuele

    2010-01-01

    Through laboratory experiments, we tested whether UV radiation (UVR) induces filamentation in natural bacteria assemblages from North Andean Patagonian lakes. We incubated water from three different lakes for 72 h in four separate treatments: (1) UVR + PAR (photosynthetically active radiation), (2) 50% UVR + PAR, (3) PAR and (4) 50% PAR. The irradiance levels used in the experiments were equivalent to those registered at the epilimnion of the lakes. In the UVR treatments filamentation was induced after the first 24 h and the proportion continued to increase for the next 48-72 h. A comparison of the gross composition and diversity of the entire community (cells >0.2 microm) with bacterial filaments alone (>5.0 microm) showed that UVR-induced filamentation is not a feature of any particular cluster. By sequencing part of the 16S rRNA gene of the taxonomic units obtained using denaturing gels, we observed that strains in the beta-Proteobacteria group were of relatively high importance in filament formation, followed by Cytophaga-Flavobacterium-Bacteroides, gamma-Proteobacteria and alpha-Proteobacteria, whereas Actinobacteria were almost nonexistent in the filaments. We propose that UVR doses equivalent to those of Andean lakes produce bacterial morphological changes, and that all bacterial groups except Actinobacteria can potentially form filaments.

  20. Influence of Candida pulcherrima Patagonian strain on alcoholic fermentation behaviour and wine aroma.

    PubMed

    Rodríguez, María Eugenia; Lopes, Christian A; Barbagelata, Raúl J; Barda, Nora B; Caballero, Adriana C

    2010-03-31

    The use of selected Saccharomyces and non-Saccharomyces strains as mixed starters in winemaking would have advantages over the traditional spontaneous fermentation, producing wines with predictable and desirable characteristics. The aim of this study was to evaluate the impact of metabolic interactions between Patagonian indigenous Saccharomyces cerevisiae MMf9 and beta-glucosidase producer Candida pulcherrima V(6) strains on alcoholic fermentation behaviour and wine aroma Three inoculation strategies, simultaneous, sequential and final, were assayed at laboratory-scale fermentations using Muscat d'Alexandrie grape juice as substrate. The fermentation and yeast growth kinetics as well as the physicochemical and the sensory quality of wine were evaluated. Results evidenced that the sequential inoculation is the most adequate strategy of strains combination. The kinetic behaviour of sequential fermentation was similar to a successful spontaneous fermentation and its wine showed differential aromatic quality as evidenced through PC analysis using physicochemical and aromatic composition data. This wine presented the highest total concentration of higher alcohol, esters and terpenols and the strongest fruity and floral aroma.

  1. Are Vegetative Reproduction Capacities the Cause of Widespread Invasion of Eurasian Salicaceae in Patagonian River Landscapes?

    PubMed Central

    Thomas, Lisa K.; Tölle, Lena; Ziegenhagen, Birgit; Leyer, Ilona

    2012-01-01

    In recent decades, invasive willows and poplars (Salicaceae) have built dense floodplain forests along most of the rivers in Patagonia, Argentina. These invasion processes may affect Salix humboldtiana as the only native floodplain tree species in this region. It is assumed, that the property to reproduce vegetatively can play an important role in the establishment of invasive species in their new range. Thus, in order to contribute to a better understanding of willow and poplar invasions in riparian systems and to assess the potential impacts on S. humboldtiana the vegetative reproduction capacities of native and invasive Salicaceae were analysed. In a greenhouse experiment, we studied cutting survival and growth performance of the three most dominant invasive Salicaceae of the Patagonian Río Negro region (two Salix hybrids and Populus spec.), as well as S. humboldtiana, taking into account three different moisture and two different soil conditions. In a subsequent experiment, the shoot and root biomass of cuttings from the former experiment were removed and the bare cuttings were replanted to test their ability to re-sprout. The two invasive willow hybrids performed much better than S. humboldtiana and Populus spec. under all treatment combinations and tended to re-sprout more successfully after repeated biomass loss. Taking into account the ecology of vegetative and generative recruits of floodplain willows, the results indicate that the more vigorous vegetative reproduction capacity can be a crucial property for the success of invasive willow hybrids in Patagonia being a potential threat for S. humboldtiana. PMID:23226531

  2. Torpor in the Patagonian opossum (Lestodelphys halli): implications for the evolution of daily torpor and hibernation.

    PubMed

    Geiser, Fritz; Martin, Gabriel M

    2013-10-01

    Hibernation and daily torpor are two distinct forms of torpor, and although they are related, it is not known how and in which sequence they evolved. As the pattern of torpor expressed by the oldest marsupial order the opossums (Didelphimorphia) may provide insights into the evolution of torpor, we aimed to provide the first quantitative data on the thermal biology and torpor expression of the rare Patagonian opossum (Lestodelphys halli). It is the opossum with the southernmost distribution, has a propensity of autumnal fattening, and therefore, is likely to hibernate. We captured two male Lestodelphys, which while in captivity displayed strong daily fluctuations of body temperatures (Tb) measured with implanted miniature data loggers even when they remained normothermic. In autumn and early winter, torpor was expressed occasionally when food was available, but cold exposure and food withdrawal increased torpor use. The mean Tb throughout the study was 32.2 ± 1.4 °C, the minimum Tb measured in torpid Lestodelphys was 7.7 °C, average torpor bout duration was 10.3 h, and the maximum torpor bout duration was 42.5 h. Thus, the pattern of torpor expressed by Lestodelphys was intermediate between that of daily heterotherms and hibernators suggesting that it may represent an ancestral opportunistic torpor pattern from which the derived patterns of daily torpor and seasonal hibernation diverged.

  3. Rhodotorula mucilaginosa, a carotenoid producing yeast strain from a Patagonian high-altitude lake.

    PubMed

    Libkind, D; Brizzio, S; van Broock, M

    2004-01-01

    The red yeast Rhodotorula mucilaginosa strain CRUB 0138 (previously identified as R. lactosa) was isolated from a high-altitude Patagonian Lake Toncek (1700 m a.s.l.), and assigned with mucilaginosa species. Its biochemical, physiological and molecular features were assessed and compared to R. mucilaginosa PYCC 5166 type strain using a polyphasic approach; in addition, biomass and carotenoid pigment production at different C/N ratios were determined in an incubator shaker. Phenetic characterization by means of 70 current physiological tests including assimilation of aldaric acids and aromatic compounds, and also the ability to grow with amino acids as sole carbon sources, was carried out. According to numerical taxonomy calculations, similarity indexes between R. mucilaginosa CRUB 0138 and PYCC 5166 type strain were 0.86 and 0.77, corresponding to a complete set of physiological tests and MSP-PCR (Mini/Micro Satellite Primed PCR; (GTG)5, M13 and (GAC)5 primers were employed) fingerprinting. Killer activity against 2 native strains, Rhodosporidium kratochvilovae and R. mucilaginosa was detected. Maximum biomass-glucose conversion efficiency (87%) and maximum carotenoid yield (2.32 mg/L) were obtained at C/N = 5 in culture medium containing 10 and 40 g/L glucose, respectively. Different C/N ratios did not influence carotenoid pigment production but low C/N enhanced biomass yield.

  4. Are vegetative reproduction capacities the cause of widespread invasion of Eurasian Salicaceae in Patagonian river landscapes?

    PubMed

    Thomas, Lisa K; Tölle, Lena; Ziegenhagen, Birgit; Leyer, Ilona

    2012-01-01

    In recent decades, invasive willows and poplars (Salicaceae) have built dense floodplain forests along most of the rivers in Patagonia, Argentina. These invasion processes may affect Salix humboldtiana as the only native floodplain tree species in this region. It is assumed, that the property to reproduce vegetatively can play an important role in the establishment of invasive species in their new range. Thus, in order to contribute to a better understanding of willow and poplar invasions in riparian systems and to assess the potential impacts on S. humboldtiana the vegetative reproduction capacities of native and invasive Salicaceae were analysed. In a greenhouse experiment, we studied cutting survival and growth performance of the three most dominant invasive Salicaceae of the Patagonian Río Negro region (two Salix hybrids and Populus spec.), as well as S. humboldtiana, taking into account three different moisture and two different soil conditions. In a subsequent experiment, the shoot and root biomass of cuttings from the former experiment were removed and the bare cuttings were replanted to test their ability to re-sprout. The two invasive willow hybrids performed much better than S. humboldtiana and Populus spec. under all treatment combinations and tended to re-sprout more successfully after repeated biomass loss. Taking into account the ecology of vegetative and generative recruits of floodplain willows, the results indicate that the more vigorous vegetative reproduction capacity can be a crucial property for the success of invasive willow hybrids in Patagonia being a potential threat for S. humboldtiana.

  5. Aquatic Coleoptera Distribution and Environmental Relationships in a Large Patagonian River

    NASA Astrophysics Data System (ADS)

    Miserendino, María Laura; Archangelsky, Miguel

    2006-10-01

    The benthic coleopteran assemblages of the Chubut River basin were studied in order to assess the main factors affecting species composition and distribution along the upper, middle and lower catchments. A total of 13 sampling sites were selected and sampled seasonally. Eight taxa and 1,601 individuals were collected during the study. Richness was higher in the main channel of Chubut River at the upper basin than at the middle basin. Beetles were completely absent at the lower basin. Mean monthly density per sites varied from 0 to 85 ind m-2. Stethelmis kaszabi had a more restricted distribution whereas Hemiosus dejeanii, Austrelmis sp. and Austrolimnius spp. were more frequent and abundant. Austrelmis sp. appears as the most tolerant species, especially to higher TSS, ammonia, and conductivity values. Luchoelmis cekalovici was absent in stations associated with urban areas. A Canonical Correspondence Analysis shows that conductivity, total suspended solids, wet width, water temperature and pH were the most important variables structuring beetle assemblages. Land use related variables such as NH4, TP, and NO3 were less important but still significant. An increase in TSS affected negatively the coleopteran community; this could be related to both hydrogeological characteristics and agricultural activities (including overgrazing).This is the first approach to the knowledge of the ecological range of distribution of the coleopteran species in Patagonian rivers.

  6. New evidence for mid-Pliocene-early Pleistocene glaciation in the northern Patagonian Andes Argentina

    SciTech Connect

    Stephens, G.C.; Evenson, E.B.; Rabassa, J.

    1985-01-01

    Mount Tronador is an extinct, glacially eroded strato-volcano located in the northern Patagonian Andes. With a summit elevation of 3556 m, Mount Tronador lies mostly above the present regional snowline (2000 m) and is largely covered by extensive snow fields and glaciers. The rocks of Mount Tronador comprise the Tronador Formation, a 2000 m thick sequence of interlayered basalts, andesites, ignimbrites, agglomerates, volcanic mudflows and lahars. This volcanic edifice is built on an erosional land surface of Tertiary age. Three K-Ar dates from the Tronador Formation yield radiometric ages of 3.2, 0.34 and 0.18 m.y. Striated clasts have been found included in several large glacial boulders derived from volcanic mudflows and lahars of the Tronador Fm. These boulders have been eroded by the Rio Manso Glacier and deposited in its Neoglacial moraines. The lahar boulders themselves contain pebbles and boulders of andesitic rocks in a vitroclastic matrix of pyroclastic origin. The striated clasts are well-rounded, shaped and polished, and the striations can be traced beneath the volcanic matrix. Thus these striated clasts represent a pre-Holocene cycle of glaciation. Mercer (1976) and Ciesielski (1982) document glaciations from southern Patagonia (2.1-3.5 m.y.) and from the southwestern Atlantic (2.1-3.9 m.y.) respectively. The discovery of striated clasts in lahars and mudflows of the Tronador Fm. indicates the existence of a heretofore undocumented Pliocene-Pleistocene glaciation in northern Patagonia.

  7. Do soil organisms affect aboveground litter decomposition in the semiarid Patagonian steppe, Argentina?

    PubMed

    Araujo, Patricia I; Yahdjian, Laura; Austin, Amy T

    2012-01-01

    Surface litter decomposition in arid and semiarid ecosystems is often faster than predicted by climatic parameters such as annual precipitation or evapotranspiration, or based on standard indices of litter quality such as lignin or nitrogen concentrations. Abiotic photodegradation has been demonstrated to be an important factor controlling aboveground litter decomposition in aridland ecosystems, but soil fauna, particularly macrofauna such as termites and ants, have also been identified as key players affecting litter mass loss in warm deserts. Our objective was to quantify the importance of soil organisms on surface litter decomposition in the Patagonian steppe in the absence of photodegradative effects, to establish the relative importance of soil organisms on rates of mass loss and nitrogen release. We estimated the relative contribution of soil fauna and microbes to litter decomposition of a dominant grass using litterboxes with variable mesh sizes that excluded groups of soil fauna based on size class (10, 2, and 0.01 mm), which were placed beneath shrub canopies. We also employed chemical repellents (naphthalene and fungicide). The exclusion of macro- and mesofauna had no effect on litter mass loss over 3 years (P = 0.36), as litter decomposition was similar in all soil fauna exclusions and naphthalene-treated litter. In contrast, reduction of fungal activity significantly inhibited litter decomposition (P < 0.001). Although soil fauna have been mentioned as a key control of litter decomposition in warm deserts, biogeographic legacies and temperature limitation may constrain the importance of these organisms in temperate aridlands, particularly in the southern hemisphere.

  8. Preference for different inorganic nitrogen forms among plant functional types and species of the Patagonian steppe.

    PubMed

    Gherardi, Laureano A; Sala, Osvaldo E; Yahdjian, Laura

    2013-11-01

    We have explored species-specific preferences for nitrate (NO3(-)) and ammonium (NH4(+)) as an alternative niche separation in ecosystems where nitrogen (N) is present mostly in inorganic forms. The Patagonian steppe is dominated by shrubs and grasses. Shrubs absorb water and nutrients from deep soil layers, which are poor in N, while grasses have the opposite pattern, absorbing most of their water and nutrients from the upper layers of the soil. We hypothesized that the preferences of shrub and grass for inorganic N forms are different and that the rate of potential N uptake is greater in shrubs than in grasses. To test this hypothesis, we grew individuals of six dominant species in solutions of different NH4(+):NO3(-) concentration ratios. Nitrate uptake was found to be higher in shrubs, while ammonium uptake was similar between plant functional types. The NH4(+):NO3(-) uptake ratio was significantly lower for shrubs than grasses. Shrubs, which under field conditions have deeper rooting systems than grasses, showed a higher N absorption capacity than grasses and a preference for the more mobile N form, nitrate. Grasses, which had lower N uptake rates than shrubs, preferred ammonium over nitrate. These complementary patterns between grasses and shrubs suggest a more thorough exploitation of resources by diverse ecosystems than those dominated by just one functional type. The loss of one plant functional group or a significant change in its abundance would therefore represent a reduction in resource use efficiency and ecosystem functioning.

  9. The Impact of Predation by Marine Mammals on Patagonian Toothfish Longline Fisheries

    PubMed Central

    Söffker, Marta; Trathan, Phil; Clark, James; Collins, Martin A.; Belchier, Mark; Scott, Robert

    2015-01-01

    Predatory interaction of marine mammals with longline fisheries is observed globally, leading to partial or complete loss of the catch and in some parts of the world to considerable financial loss. Depredation can also create additional unrecorded fishing mortality of a stock and has the potential to introduce bias to stock assessments. Here we aim to characterise depredation in the Patagonian toothfish (Dissostichus eleginoides) fishery around South Georgia focusing on the spatio-temporal component of these interactions. Antarctic fur seals (Arctocephalus gazella), sperm whales (Physeter macrocephalus), and orcas (Orcinus orca) frequently feed on fish hooked on longlines around South Georgia. A third of longlines encounter sperm whales, but loss of catch due to sperm whales is insignificant when compared to that due to orcas, which interact with only 5% of longlines but can take more than half of the catch in some cases. Orca depredation around South Georgia is spatially limited and focused in areas of putative migration routes, and the impact is compounded as a result of the fishery also concentrating in those areas at those times. Understanding the seasonal behaviour of orcas and the spatial and temporal distribution of “depredation hot spots” can reduce marine mammal interactions, will improve assessment and management of the stock and contribute to increased operational efficiency of the fishery. Such information is valuable in the effort to resolve the human-mammal conflict for resources. PMID:25738698

  10. Seismic Reflection Methods

    EPA Pesticide Factsheets

    Seismic methods are the most commonly conducted geophysical surveys for engineering investigations. Seismic refraction provides engineers and geologists with the most basic of geologic data via simple procedures with common equipment.

  11. Seismic intrusion detector system

    DOEpatents

    Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

    1976-01-01

    A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

  12. Updated seismic solar model

    NASA Astrophysics Data System (ADS)

    Dziembowski, W. A.; Goode, Philip R.; Pamyatnykh, A. A.; Sienkiewicz, R.

    1995-05-01

    Recently released low-l solar oscillation data from the BISON network are combined with BBSO data to obtain an updated solar seismic model of the Sun's interior. For the core, the solar seismic model from the new data is more consistent with the current standard solar models than our earlier seismic model. An astrophysical solution to the solar neutrino problem fades away.

  13. Conflicting Evolutionary Patterns Due to Mitochondrial Introgression and Multilocus Phylogeography of the Patagonian Freshwater Crab Aegla neuquensis

    PubMed Central

    Barber, Brian R.; Xu, Jiawu; Pérez-Losada, Marcos; Jara, Carlos G.; Crandall, Keith A.

    2012-01-01

    Background Multiple loci and population genetic methods were employed to study the phylogeographic history of the Patagonian freshwater crab Aegla neuquensis (Aeglidae: Decopoda). This taxon occurs in two large river systems in the Patagonian Steppe, from the foothills of the Andes Mountains east to the Atlantic Ocean. Methodology/Principal Findings A nuclear phylogeny and multilocus nested clade phylogeographic analysis detected a fragmentation event between the Negro and Chico-Chubut river systems. This event occurred approximately 137 thousand years ago. An isolation-with-migration analysis and maximum-likelihood estimates of gene flow showed asymmetrical exchange of genetic material between these two river systems exclusively in their headwaters. We used information theory to determine the best-fit demographic history between these two river systems under an isolation-with-migration model. The best-fit model suggests that the Negro and the ancestral populations have the same effective population sizes; whereas the Chico-Chubut population is smaller and shows that gene flow from the Chico-Chubut into the Negro is four times higher than in the reverse direction. Much of the Chico-Chubut system appears to have only been recently colonized while the Negro populations appear to have been in place for most of the evolutionary history of this taxon. Conclusions/Significance Due to mitochondrial introgression, three nuclear loci provided different phylogeographic resolution than the three mitochondrial genes for an ancient fragmentation event observed in the nuclear phylogeny. However, the mitochondrial locus provided greater resolution on more recent evolutionary events. Our study, therefore, demonstrates the need to include both nuclear and mitochondrial loci for a more complete understanding of evolutionary histories and associated phylogeographic events. Our results suggest that gene flow between these systems, before and after fragmentation was through periodic

  14. Variability in light absorption and scattering of phytoplankton in Patagonian waters: Role of community size structure and pigment composition

    NASA Astrophysics Data System (ADS)

    Ferreira, Amabile; Stramski, Dariusz; Garcia, Carlos A. E.; Garcia, Virginia M. T.; Ciotti, ÁUrea M.; Mendes, Carlos R. B.

    2013-02-01

    Intense phytoplankton blooms were observed along the Patagonian shelf-break with satellite ocean color data, but few in situ optical observations were made in that region. We examine the variability of phytoplankton absorption and particulate scattering coefficients during such blooms on the basis of field data. The chlorophyll-a concentration, [Chla], ranged from 0.1 to 22.3 mg m-3 in surface waters. The size fractionation of [Chla] showed that 80% of samples were dominated by nanophytoplankton (N-group) and 20% by microphytoplankton (M-group). Chlorophyll-specific phytoplankton absorption coefficients at 440 and 676 nm, a*ph(440) and a*ph(676), and particulate scattering coefficient at 660 nm, b*p(660), ranged from 0.018 to 0.173, 0.009 to 0.046, and 0.031 to 2.37 m2 (mg Chla)-1, respectively. Both a*ph(440) and a*ph(676) were statistically higher for the N-group than M-group and also considerably higher than expected from global trends as a function of [Chla]. This result suggests that size of phytoplankton cells in Patagonian waters tends to be smaller than in other regions at similar [Chla]. The phytoplankton cell size parameter, Sf, derived from phytoplankton absorption spectra, proved to be useful for interpreting the variability in the data around the general inverse dependence of a*ph(440), a*ph(676), and b*p(660) on [Chla]. Sf also showed a pattern along the increasing trend of a*ph(440) and a*ph(676) as a function of the ratios of some accessory pigments to [Chla]. Our results suggest that the variability in phytoplankton absorption and scattering coefficients in Patagonian waters is caused primarily by changes in the dominant phytoplankton cell size accompanied by covariation in the concentrations of accessory pigments.

  15. Conflicting evolutionary patterns due to mitochondrial introgression and multilocus phylogeography of the Patagonian freshwater crab Aegla neuquensis.

    PubMed

    Barber, Brian R; Xu, Jiawu; Pérez-Losada, Marcos; Jara, Carlos G; Crandall, Keith A

    2012-01-01

    Multiple loci and population genetic methods were employed to study the phylogeographic history of the Patagonian freshwater crab Aegla neuquensis (Aeglidae: Decopoda). This taxon occurs in two large river systems in the Patagonian Steppe, from the foothills of the Andes Mountains east to the Atlantic Ocean. A nuclear phylogeny and multilocus nested clade phylogeographic analysis detected a fragmentation event between the Negro and Chico-Chubut river systems. This event occurred approximately 137 thousand years ago. An isolation-with-migration analysis and maximum-likelihood estimates of gene flow showed asymmetrical exchange of genetic material between these two river systems exclusively in their headwaters. We used information theory to determine the best-fit demographic history between these two river systems under an isolation-with-migration model. The best-fit model suggests that the Negro and the ancestral populations have the same effective population sizes; whereas the Chico-Chubut population is smaller and shows that gene flow from the Chico-Chubut into the Negro is four times higher than in the reverse direction. Much of the Chico-Chubut system appears to have only been recently colonized while the Negro populations appear to have been in place for most of the evolutionary history of this taxon. Due to mitochondrial introgression, three nuclear loci provided different phylogeographic resolution than the three mitochondrial genes for an ancient fragmentation event observed in the nuclear phylogeny. However, the mitochondrial locus provided greater resolution on more recent evolutionary events. Our study, therefore, demonstrates the need to include both nuclear and mitochondrial loci for a more complete understanding of evolutionary histories and associated phylogeographic events. Our results suggest that gene flow between these systems, before and after fragmentation was through periodic paleolakes that formed in the headwaters region. Fragmentation

  16. Temporal and spatial distribution of floating objects in coastal waters of central-southern Chile and Patagonian fjords

    NASA Astrophysics Data System (ADS)

    Hinojosa, Iván A.; Rivadeneira, Marcelo M.; Thiel, Martin

    2011-03-01

    Floating objects are suggested to be the principal vector for the transport and dispersal of marine invertebrates with direct development as well as catalysts for carbon and nutrient recycling in accumulation areas. The first step in identifying the ecological relevance of floating objects in a specific area is to identify their spatio-temporal distribution. We evaluated the composition, abundance, distribution, and temporal variability of floating objects along the continental coast of central-southern Chile (33-42°S) and the Patagonian fjords (42-50°S) using ship surveys conducted in austral winter (July/August) and spring (November) of the years 2002-2005 and 2008. Potential sources of floating items were identified with the aid of publicly available databases and scientific reports. We found three main types of floating objects, namely floating marine debris (mainly plastic objects and Styrofoam), wood (trunks and branches), and floating kelps ( Macrocystis pyrifera and Durvillaea antarctica). Floating marine debris were abundant along most of the examined transects, with markedly lower abundances toward the southern fjord areas. Floating marine debris abundances generally corresponded to the distribution of human activities, and were highest in the Interior Sea of Chiloé, where aquaculture activities are intense. Floating wood appeared sporadically in the study area, often close to the main rivers. In accordance with seasonal river run-off, wood was more abundant along the continental coast in winter (rainy season) and in the Patagonian fjords during the spring surveys (snow melt). Densities of the two floating kelp species were similar along the continental coast, without a clear seasonal pattern. M. pyrifera densities increased towards the south, peaking in the Patagonian fjords, where it was dominant over D. antarctica. Densities of M. pyrifera in the Patagonian fjords were highest in spring. Correlation analyses between the abundances of floating

  17. Selection and characterization of a Patagonian Pichia kudriavzevii for wine deacidification.

    PubMed

    Del Mónaco, S M; Barda, N B; Rubio, N C; Caballero, A C

    2014-08-01

    The purpose of this study was to select autochthonous yeasts with metabolic ability to degrade L-malic acid for its potential use in young wine deacidification. Fifty seven Patagonian nonSaccharomyces yeast of oenological origin were identified by conventional molecular methods and tested in their capability to grow at the expense of L-malic acid. Only four isolates belonging to Pichia kudriavzevii species showed this property, and one of them was selected to continue with the study. This isolate, named as P. kudriavzevii ÑNI15, was able to degrade L-malic acid in microvinifications, increasing the pH 0·2-0·3 units with a minimal effect on the acid structure of wine. Additionally, this isolate produced low levels of ethanol, important levels of glycerol (10·41 ± 0·48 g l(-1) ) and acceptable amounts of acetic acid (0·86 ± 0·13 g l(-1) ). In addition, it improved the sensorial attributes of wine increasing its fruity aroma. The selection of yeasts for oenological use among nonSaccharomyces species led to the finding of a yeast strain with novel and interesting oenological characteristics which could have significant implications in the production of well-balanced and more physicochemical and microbiological stable young wines. The use of P. kudriavzevii ÑNI15 as mixed starter with S. cerevisiae would eliminate the cultural and cellar operations undertaken to adjust the musts acidity, therefore improving wine quality and reducing production costs. © 2014 The Society for Applied Microbiology.

  18. Phenotypic plasticity as an index of drought tolerance in three Patagonian steppe grasses

    PubMed Central

    Couso, L. L.; Fernández, R. J.

    2012-01-01

    Background and Aims Despite general agreement regarding the adaptive importance of plasticity, evidence for the role of environmental resource availability in plants is scarce. In arid and semi-arid environments, the persistence and dominance of perennial species depends on their capacity to tolerate drought: tolerance could be given on one extreme by fixed traits and, on the other, by plastic traits. To understand drought tolerance of species it is necessary to know the plasticity of their water economy-related traits, i.e. the position in the fixed–plastic continuum. Methods Three conspicuous co-existing perennial grasses from a Patagonian steppe were grown under controlled conditions with four levels of steady-state water availability. Evaluated traits were divided into two groups. The first was associated with potential plant performance and correlated with fitness, and included above-ground biomass, total biomass, tillering and tiller density at harvest. The second group consisted of traits associated with mechanisms of plant adjustment to environmental changes and included root biomass, shoot/root ratio, tiller biomass, length of total elongated leaf, length of yellow tissue divided by time and final length divided by the time taken to reach final length. Key Results and Conclusions The most plastic species along this drought gradient was the most sensitive to drought, whereas the least plastic and slowest growing was the most tolerant. This negative relationship between tolerance and plasticity was true for fitness-related traits but was trait-dependent for underlying traits. Remarkably, the most tolerant species had the highest positive plasticity (i.e. opposite to the default response to stress) in an underlying trait, directly explaining its drought resistance: it increased absolute root biomass. The niche differentiation axis that allows the coexistence of species in this group of perennial dryland grasses, all limited by soil surface moisture, would

  19. A new anisakid species parasitizing the imperial cormorant Phalacrocorax atriceps from the North Patagonian Coast, Argentina.

    PubMed

    Garbin, Lucas E; Diaz, Julia I; Cremonte, Florencia; Navone, Graciela T

    2008-08-01

    The anisakid species Contracaecum chubutensis n. sp. was found parasitizing the imperial cormorant Phalacrocorax atriceps at 2 different localities, Bahía Bustamante (45 degrees 11'S, 66 degrees 30'W) and Puerto Madryn (42 degrees 47'S, 65 degrees 02'W) on the Patagonian coast. Morphometrical analysis and further studies of adult specimens of C. chubutensis n. sp. and fourth-stage larvae of Contracaecum sp. were done using light and scanning electron microscopy. The possession and disposition of 7 pairs of tail papillae differentiate this new species from C. osculatum, C. radiatum, C. plagiaticium, and C. mirounga. Double-sized spicules separate it from C. variegatum and C. pelagicum. Moreover, the paracloacal papillae disposition and tail shape differentiate this new species from C. travassosi. The presence of bifurcated interlabia separate it from C. ogmorhini and C. margolisi. Three well-marked lip notches, a sharp tail shape, and the of the transversal paracloacal papillae disposition distinguishes C. chubutensis n. sp. from C. magnipapillatum and C. septentrionale. The species here described can be differentiated from C. caballeroi by its bifurcated interlabia, longer spicules, and for possessing more precloacal papillae pairs. It can be separated from C. rudolphii by a thinner interlabia at the base, deeper lip notches, a sharper tail, the disposition of transversal paracloacal papillae, and greater distance between both papillae of the first subventral distal papillae pair. In addition, fourth-stage larvae recovered from the same host and localities were identified and described as Contracaecum sp. Prevalence of adult parasites was 66.7 %, mean intensity was 4.0, and mean abundance was 7.1.

  20. Dynamics of Fasciola hepatica transmission in the Andean Patagonian valleys, Argentina.

    PubMed

    Kleiman, Florencia; Pietrokovsky, Silvia; Prepelitchi, Lucila; Carbajo, Aníbal E; Wisnivesky-Colli, Cristina

    2007-04-30

    We described the transmission dynamics of Fasciola hepatica at its southern distribution range. Studies of prevalence and egg output in cattle and population dynamics and infection in snails were performed in a farm in the Andean Patagonian valleys, Argentina, between December 1998 and February 2002. Snail surveys were conducted from spring to autumn. Infection was diagnosed coprologically in the whole herd at the beginning and end of the study, and in a cohort of heifers at the beginning and end of 2001. A twice-a-year anthelmintic treatment was implemented in 1999. The relationship of the variables mentioned above with temperature and rainfall was determined. Lymnaea viatrix showed a life-span of about 15 months and an annual pattern of population dynamics. Specimens were frequently found in temporary environments and lagoons, and rarely in streams. Snail abundance and soil-water availability were directly related in temporary environments and inversely related in lagoons. Overall prevalence in L. viatrix was 0.67% (range: 0.9-14%) and infection was detected in summer and autumn. At the beginning of the study, calves were the least infected age group (15%). Prevalences and median egg counts in grazing animals were similar at the beginning (heifers: 81%, 3.3 epg; cows: 60%, 1.3 epg) and end of the study (heifers and cows: around 51%, 1 epg). Likewise, the prevalence in the cohort of heifers remained similar (around 40%) between surveys. Transmission to cattle was highly effective despite of the short activity period and the low infection rate of snails, and the regular anthelminthic treatment. There would be two seasonal transmission peaks, one in summer-autumn, when infected snails were present, and the other in early spring due to overwintering metacercariae. Some recommendations based on the climatic conditions of the region are provided to minimize snail infection and ultimately to reduce the incidence of fasciolosis in cattle.

  1. Transcriptome survey of Patagonian southern beech Nothofagus nervosa (= N. Alpina): assembly, annotation and molecular marker discovery.

    PubMed

    Torales, Susana L; Rivarola, Máximo; Pomponio, María F; Fernández, Paula; Acuña, Cintia V; Marchelli, Paula; Gonzalez, Sergio; Azpilicueta, María M; Hopp, Horacio Esteban; Gallo, Leonardo A; Paniego, Norma B; Poltri, Susana N Marcucci

    2012-07-02

    Nothofagus nervosa is one of the most emblematic native tree species of Patagonian temperate forests. Here, the shotgun RNA-sequencing (RNA-Seq) of the transcriptome of N. nervosa, including de novo assembly, functional annotation, and in silico discovery of potential molecular markers to support population and associations genetic studies, are described. Pyrosequencing of a young leaf cDNA library generated a total of 111,814 high quality reads, with an average length of 447 bp. De novo assembly using Newbler resulted into 3,005 tentative isotigs (including alternative transcripts). The non-assembled sequences (singletons) were clustered with CD-HIT-454 to identify natural and artificial duplicates from pyrosequencing reads, leading to 21,881 unique singletons. 15,497 out of 24,886 non-redundant sequences or unigenes, were successfully annotated against a plant protein database. A substantial number of simple sequence repeat markers (SSRs) were discovered in the assembled and annotated sequences. More than 40% of the SSR sequences were inside ORF sequences. To confirm the validity of these predicted markers, a subset of 73 SSRs selected through functional annotation evidences were successfully amplified from six seedlings DNA samples, being 14 polymorphic. This paper is the first report that shows a highly precise representation of the mRNAs diversity present in young leaves of a native South American tree, N. nervosa, as well as its in silico deduced putative functionality. The reported Nothofagus transcriptome sequences represent a unique resource for genetic studies and provide a tool to discover genes of interest and genetic markers that will greatly aid questions involving evolution, ecology, and conservation using genetic and genomic approaches in the genus.

  2. Transcriptome survey of Patagonian southern beech Nothofagus nervosa (= N. Alpina): assembly, annotation and molecular marker discovery

    PubMed Central

    2012-01-01

    Background Nothofagus nervosa is one of the most emblematic native tree species of Patagonian temperate forests. Here, the shotgun RNA-sequencing (RNA-Seq) of the transcriptome of N. nervosa, including de novo assembly, functional annotation, and in silico discovery of potential molecular markers to support population and associations genetic studies, are described. Results Pyrosequencing of a young leaf cDNA library generated a total of 111,814 high quality reads, with an average length of 447 bp. De novo assembly using Newbler resulted into 3,005 tentative isotigs (including alternative transcripts). The non-assembled sequences (singletons) were clustered with CD-HIT-454 to identify natural and artificial duplicates from pyrosequencing reads, leading to 21,881 unique singletons. 15,497 out of 24,886 non-redundant sequences or unigenes, were successfully annotated against a plant protein database. A substantial number of simple sequence repeat markers (SSRs) were discovered in the assembled and annotated sequences. More than 40% of the SSR sequences were inside ORF sequences. To confirm the validity of these predicted markers, a subset of 73 SSRs selected through functional annotation evidences were successfully amplified from six seedlings DNA samples, being 14 polymorphic. Conclusions This paper is the first report that shows a highly precise representation of the mRNAs diversity present in young leaves of a native South American tree, N. nervosa, as well as its in silico deduced putative functionality. The reported Nothofagus transcriptome sequences represent a unique resource for genetic studies and provide a tool to discover genes of interest and genetic markers that will greatly aid questions involving evolution, ecology, and conservation using genetic and genomic approaches in the genus. PMID:22747958

  3. Selenium and mercury in native and introduced fish species of patagonian lakes, Argentina.

    PubMed

    Arribére, M A; Ribeiro Guevara, S; Bubach, D F; Arcagni, M; Vigliano, P H

    2008-04-01

    A survey of mercury (Hg) and selenium (Se) contents was performed in fish collected from lakes located in two National Parks of the northern patagonian Andean range. Two native species, catfish (Diplomystes viedmensis) and creole perch (Percichthys trucha), and three introduced species, brown trout (Salmo trutta), rainbow trout (Oncorhynchus mykiss), and brook trout (Salvelinus fontinalis), were caught from lakes Nahuel Huapi, Moreno, Traful, Espejo Chico, and Guillelmo belonging to Nahuel Huapi National Park and from lakes Futalaufquen and Rivadavia, Los Alerces National Park. In lake Moreno, fish diet items were analyzed and rainbow trout grown in a farm. Hg and Se were measured in muscle and liver tissues by instrumental neutron activation analysis. The average concentrations in muscle of Hg for all species, ages, and lakes are between 0.4 to 1.0 microg g(-1) dry weight (DW) with a few fish, mainly native, exceeding the United States Environmental Protection Agency health advisory for freshwater fish limited consumption, and from 0.8 to 1.5 microg g(-1) DW for Se. Average concentrations in liver of Hg in all species range from 0.4 to 0.9 microg g(-1) DW. Brown trout, the top predator in these lakes, showed the lowest average Hg burden in both tissues. Se concentrations in the liver of brown and rainbow trout, up to 279 microg g(-1) DW, are higher than those expected for nearly pristine lakes, exceeding 20 microg g(-1) DW, the threshold concentration associated with Se toxicity. These species show lower Hg contents in muscle, suggesting a possible detoxification of Hg by a Se-rich diet. Creole perch and velvet catfish livers have lower Se concentrations, with a narrower span of values (2.3 to 8.5 microg g(-1) and 3.3 to 5.5 microg g(-1) DW respectively).

  4. Spectral attenuation of solar radiation in Patagonian fjord and coastal waters and implications for algal photobiology

    NASA Astrophysics Data System (ADS)

    Huovinen, Pirjo; Gómez, Iván

    2011-03-01

    The spectral attenuation of solar irradiation was measured during summer in two types of coastal waters in southern Chile, a north Patagonian fjord (Seno Reloncaví) and open coast (Valdivia). In order to relate the light availability with the light requirements of upper subtidal seaweeds, the saturating irradiance for photosynthesis ( Ek) from P- I curves was measured. In addition the UV risk was assessed. Based on the z1% of PAR, the lower limit of the euphotic zone in the studied systems averaged 21 m ( Kd 0.24 m -1) in Seno Reloncaví and 18 m ( Kd 0.27 m -1) in the coast of Valdivia. Photosynthesis of the studied seaweeds was saturated at markedly lower irradiances than found in their natural depths at the time of the study. Solar radiation penetrating into these depths at both locations largely supports the light requirements for the photosynthesis of subtidal species: 50-160 μmol m -2 s -1 for seaweeds from Seno Reloncaví (7 m tidal range) and 20-115 μmol m -2 s -1 for Valdivia assemblages (2 m tidal range). Optimal light conditions to saturate photosynthesis ( Ek) were present at 10-16 m water depth. The attenuation of solar irradiation did not vary significantly between the fjord and coastal sites of this study. However, the underwater light climates to which seaweeds are exposed in these sites vary significantly because of the stronger influence of tidal range affecting the fjord system as compared with the open coastal site. The patterns of UV-B penetration in these water bodies suggest that seaweeds living in upper littoral zones such as the intertidal and shallow subtidal (<3 m) may be at risk.

  5. Climate change and recent water level variability in Patagonian proglacial lakes, Argentina

    NASA Astrophysics Data System (ADS)

    Pasquini, Andrea I.; Lecomte, Karina L.; Depetris, Pedro J.

    2008-10-01

    A long series of lakes (~ 150) borders the Patagonian Andes (south of ~ 38°S), most of which are a geomorphologic relict of Pleistocene glaciations. Employing instrumental records, we inspected lake water level departures from seasonal variations in seven proglacial lakes: Lacar, Mascardi, Steffen, Escondido, Puelo, Vinter, and Argentino. Lakes north of ~ 42°S show maximum gage (water) level during austral winter months; lakes between ~ 42° and ~ 45°S appear transitional; the one lake south of ~ 50°S (Argentino) shows maximum water level in early autumn. Most lakes show moderate level fluctuation throughout yearly records and, in general, show heteroscedacity. Furthermore, Hurst exponents reveal persistent behavior (i.e., long-term memory effect) in all water level series. In most lakes there are no trends in deseasonalized mean and maximum water levels (Seasonal Kendall test). Lake Mascardi-Manso River system (mostly fed by melt water from the retreating Manso Glacier) is a contrasting example that shows a decreasing trend during summer months that we ascribe to the also declining ice volume. Harmonic analysis (Fourier and wavelet transform) of deseasonalized mean and maximum water level time series shows interannual and decadal periodicities that we link to the occurrence of El Niño and/or the Antarctic Oscillation. The associated phase spectrum indicates that there is a ~ 13-month lag between ENSO occurrences and its effect on anomalous lake water levels. Increased snow accumulation during austral winters usually follows summertime El Niño events, which normally result in increased melt water volume that occurs with about one-year delay during the following (austral) spring/summer.

  6. Recent spatial and temporal variations in debris cover on Patagonian glaciers

    NASA Astrophysics Data System (ADS)

    Glasser, Neil F.; Holt, Thomas O.; Evans, Zachary D.; Davies, Bethan J.; Pelto, Mauri; Harrison, Stephan

    2016-11-01

    Supraglacial debris cover is an important component of glacier mass balance, especially in areas characterised by widespread glacier recession. Mapping of the spatial and temporal changes in debris cover on the surface of the receding outlet glaciers of the temperate North Patagonian Icefield (NPI) in southern South America between 1987 and 2015 shows that the total amount of debris cover has increased over time, from 168 km2 in 1987 to 307 km2 in 2015. The number of debris-covered glaciers increased from 24 in 1987, to 31 in 2001 and 32 out of 43 studied glaciers in 2015. The proportion of debris-covered area has also increased, from 4.1% in 1987 to 7.9% in 2015, with the largest proportional increases occurring east of the ice divide (where 15.2% of the glacier ice is now debris covered). Over this time, the total area of the NPI decreased from 4133 to 3887 km2. The area occupied by proglacial and ice-proximal lakes also increased from 112 to 198 km2. Between 1987 and 2015, the terminal environment of many of the outlet glaciers of the NPI changed from land-terminating to lake-calving, and these glaciers are now receding into terminal lakes. The change in the area of debris-covered ice is influenced by the loss of ice at debris-covered termini and by an increase in debris cover at higher elevations. The glaciers of the NPI remain highly dynamic as they recede and are therefore behaving very differently to high-elevation glaciers, such as those of the Himalaya, where debris cover leads to glacier stagnation at the termini.

  7. How Much Is Too Much? Assessment of Prey Consumption by Magellanic Penguins in Patagonian Colonies

    PubMed Central

    Sala, Juan E.; Wilson, Rory P.; Quintana, Flavio

    2012-01-01

    Penguins are major consumers in the southern oceans although quantification of this has been problematic. One suggestion proposes the use of points of inflection in diving profiles (‘wiggles’) for this, a method that has been validated for the estimation of prey consumption by Magellanic penguins (Spheniscus magellanicus) by Simeone and Wilson (2003). Following them, we used wiggles from 31 depth logger-equipped Magellanic penguins foraging from four Patagonian colonies; Punta Norte (PN), Bahía Bustamente (BB), Puerto Deseado (PD) and Puerto San Julián (PSJ), all located in Argentina between 42–49° S, to estimate the prey captured and calculate the catch per unit time (CPUT) for birds foraging during the early chick-rearing period. Numbers of prey caught and CPUT were significantly different between colonies. Birds from PD caught the highest number of prey per foraging trip, with CPUT values of 68±19 prey per hour underwater (almost two times greater than for the three remaining colonies). We modeled consumption from these data and calculate that the world Magellanic penguin population consumes about 2 million tons of prey per year. Possible errors in this calculation are discussed. Despite this, the analysis of wiggles seems a powerful and simple tool to begin to quantify prey consumption by Magellanic penguins, allowing comparison between different breeding sites. The total number of wiggles and/or CPUT do not reflect, by themselves, the availability of food for each colony, as the number of prey consumed by foraging trip is strongly associated with the energy content and wet mass of each colony-specific ‘prey type’. Individuals consuming more profitable prey could be optimizing the time spent underwater, thereby optimizing the energy expenditure associated with the dives. PMID:23251554

  8. Biogeochemical and hydrological drivers of the dynamics of Vibrio species in two Patagonian estuaries.

    PubMed

    Kopprio, Germán A; Streitenberger, M Eugenia; Okuno, Kentaro; Baldini, Mónica; Biancalana, Florencia; Fricke, Anna; Martínez, Ana; Neogi, Sucharit B; Koch, Boris P; Yamasaki, Shinji; Lara, Rubén J

    2017-02-01

    The ecology of the most relevant Vibrio species for human health and their relation to water quality and biogeochemistry were studied in two estuaries in Argentinian Patagonia. Vibrio cholerae and Vibrio parahaemolyticus were reported in >29% of cases at the Río Colorado and Río Negro estuaries. Neither the pandemic serogroups of Vibrio cholerae O1, Vibrio cholerae O139 nor the cholera toxin gene were detected in this study. However, several strains of V. cholerae (not O1 or O139) are able to cause human disease or acquire pathogenic genes by horizontal transfer. Vibrio vulnificus was detected only in three instances in the microplankton fraction of the Río Negro estuary. The higher salinity in the Río Colorado estuary and in marine stations at both estuaries favours an abundance of culturable Vibrio. The extreme peaks for ammonium, heterotrophic bacteria and faecal coliforms in the Río Negro estuary supported a marked impact on sewage discharge. Generally, the more pathogenic strains of Vibrio have a faecal origin. Salinity, pH, ammonium, chlorophyll a, silicate and carbon/nitrogen ratio of suspended organic particulates were the primary factors explaining the distribution of culturable bacteria after distance-based linear models. Several effects of dissolved organic carbon on bacterial distribution are inferred. Global change is expected to increase the trophic state and the salinisation of Patagonian estuaries. Consequently, the distribution and abundance of Vibrio species is projected to increase under future changing baselines. Adaptation strategies should contribute to sustaining good water quality to buffer climate- and anthropogenic- driven impacts.

  9. The Patagonian Orocline: New paleomagnetic data from the Andean magmatic arc in Tierra del Fuego, Chile

    NASA Astrophysics Data System (ADS)

    Cunningham, W. Dickson; Klepeis, Keith A.; Gose, Wulf A.; Dalziel, Ian W. D.

    1991-09-01

    The Hardy Formation is a 1300-m-thick succession of Upper Jurassic-Lower Cretaceous volcaniclastic sedimentary rocks interbedded with lava flows on Hoste Island at the southernmost tip of South America (55.5°S, 291.8°E). The strata are gently folded and metamorphosed to the prehnite-pumpellyite grade. A well-defined characteristic direction of magnetization, carried by magnetite, was readily identified in 95 samples from seven sites. At a given site, the directions group slightly better without structural correction. However, the means of the seven sites cluster better without tilt correction at the 99% significance level, implying that the magnetization postdates the folding event. It is most likely that the magnetization was acquired during the mid- to Late Cretaceous Andean orogeny that involved the folding and emplacement of the Patagonian Batholith. The fact that all samples are normally magnetized supports this age assignment. The pole position of 42.9°N, 156.6°E, α95=3.3° implies that the sampling area has rotated counterclockwise relative to cratonic South America by 90.1±11.9° with no significant flattening of inclination (F=1.9 ± 3.7°). Geologic considerations indicate that the rotation involved the entire Andean magmatic arc in Tierra Del Fuego. The results support interpretation of the Hardy Formation as part of the Andean magmatic arc deposited on the Pacific side of the Late Jurassic-Early Cretaceous Rocas Verdes marginal basin. Oroclinal bending of the arc in southernmost South America accompanied inversion of the marginal basin and the development of a Late Cretaceous-Cenozoic left-lateral transform system (South America-Antarctica) that later developed into the North Scotia Ridge.

  10. A Paleomagnetic Test of the Patagonian Orocline, Thirty Years Later: New Data, New Insights, New Problems.

    NASA Astrophysics Data System (ADS)

    Rapalini, A.; Herve, F.; Calderon, M.; Singer, S.; Lippai, H.; Tassone, A.; Cordani, U.

    2005-05-01

    The Andean Chain undergoes a 90 degrees bend at around 52 S, from N-S to the north to E-W to the south. This feature is called the Patagonian orocline and its origin and evolution have been much debated. Since the first paleomagnetic test performed by Dalziel et al. in the early seventies that suggested a secondary bend, several paleomagnetic studies have been carried out in the region. However, density of studies is still very low compared to other oroclines. Despite numerous uncertainties, including in cases experimental reliability, ages of magnetization and paleohorizontal control, some preliminary conclusions can be drawn from the available distribution of paleomagnetic declinations along the curved orogen. A systematic pattern of ccw rotation is apparent along the orogen that in a broad sense is consistent with a secondary origin for the bend. Largest values of rotation, 90 or more degrees, on the ocean side of the inverted Rocas Verdes marginal basin, suggest that its closure was probably an important event in the development of the orocline. To the foreland, rotations are smaller, with ca. 30 degrees in the Fueguian Andes (south of 52 S), which suggest either magnetization ages younger than most of the oroclinal bending or a complex development with local patterns of rotations. To the north, anomalous ccw rotations of ca. 50 degrees have been observed along the front of the Magallanes thrust and fold belt and an identical declination anomaly has been found along the whole Sarmiento ophiolite, although in the latter case an alternative explanation to crustal block rotation around a vertical axis is possible.

  11. How much is too much? Assessment of prey consumption by Magellanic penguins in Patagonian colonies.

    PubMed

    Sala, Juan E; Wilson, Rory P; Quintana, Flavio

    2012-01-01

    Penguins are major consumers in the southern oceans although quantification of this has been problematic. One suggestion proposes the use of points of inflection in diving profiles ('wiggles') for this, a method that has been validated for the estimation of prey consumption by Magellanic penguins (Spheniscus magellanicus) by Simeone and Wilson (2003). Following them, we used wiggles from 31 depth logger-equipped Magellanic penguins foraging from four Patagonian colonies; Punta Norte (PN), Bahía Bustamente (BB), Puerto Deseado (PD) and Puerto San Julián (PSJ), all located in Argentina between 42-49° S, to estimate the prey captured and calculate the catch per unit time (CPUT) for birds foraging during the early chick-rearing period. Numbers of prey caught and CPUT were significantly different between colonies. Birds from PD caught the highest number of prey per foraging trip, with CPUT values of 68±19 prey per hour underwater (almost two times greater than for the three remaining colonies). We modeled consumption from these data and calculate that the world Magellanic penguin population consumes about 2 million tons of prey per year. Possible errors in this calculation are discussed. Despite this, the analysis of wiggles seems a powerful and simple tool to begin to quantify prey consumption by Magellanic penguins, allowing comparison between different breeding sites. The total number of wiggles and/or CPUT do not reflect, by themselves, the availability of food for each colony, as the number of prey consumed by foraging trip is strongly associated with the energy content and wet mass of each colony-specific 'prey type'. Individuals consuming more profitable prey could be optimizing the time spent underwater, thereby optimizing the energy expenditure associated with the dives.

  12. Age-independent osteopathology in skeletons of a South American cervid, the Patagonian huemul (Hippocamelus bisulcus).

    PubMed

    Flueck, Werner T; Smith-Flueck, Jo Anne M

    2008-07-01

    The huemul (Hippocamelus bisulcus), an endemic Patagonian deer, has been endangered for decades. Although conservation in Argentina has been directed at the 350-600 remaining huemul, the population has not recovered. In initial studies on the potential effects of diseases on huemul population dynamics, skeletal remains collected between 1993 and 2007 in the Andes (41-45 degrees S, 71.5-72 degrees W) were examined macroscopically for osteopathologic changes. Bones from six huemul were free of lesions, findings were inconclusive in 13 huemul with less than three bones, and osteopathologic processes were detected in 13 adults. Considering the limited remains/case, the prevalence of osteopathy (52%) among adults probably is conservative; 63% showed mandibular, 100% maxillary, and 78% appendicular lesions. Although predation represented the actual cause of death, the observed skeletal lesions would affect predator avoidance, possibly explaining the low average adult age (3.1 yr) and lack of population recovery. Compared with other studies in ungulates, huemul were affected at a younger age, and they had more severe pathologic changes. Due to the chronic nature of disease, low huemul population density, physiognomy, and spatiotemporal pattern of lesions, we discard senescence; gender; fulminating infections; congenital anomalies; metabolic, endocrine, genetic, or neurologic disorders; parasitism or marasmus; and fluorosis as primary etiologic factors. We hypothesize that generalized secondary chronic alveolar osteomyelitis and osteoarthritis in huemul is related to the nutritional ecology of these animals. Selenium deficiency, which impairs bone metabolism and causes periodontitis in ruminants, occurs in the region and it is more prevalent at high altitudes. Traditional winter grounds at low elevations, sometimes far from high mountains, have been converted to livestock production, which has eliminated migratory behavior and keeps huemul in remote high-elevation refuges

  13. Towards an annually-resolved record of Lateglacial Patagonian ice sheet dynamics using glaciolacustrine varves

    NASA Astrophysics Data System (ADS)

    Bendle, Jacob; Palmer, Adrain; Thorndycraft, Varyl

    2016-04-01

    Proglacial sedimentary archives, in particular, glaciolacustrine varve sequences, offer the potential for detailed reconstructions of past ice sheet dynamics. Specifically, glaciolacustrine varves (i) allow reconstructions of sediment (and thus meltwater) influx at annual and even sub-annual resolution; and (ii) provide a continuous, annually-resolved chronology to estimate rates of change and/or the duration of significant events in the deglaciation of a basin. In South America, glacial geologists have relied heavily on cosmogenic nuclide exposure dating to construct chronologies for palaeoglaciological activity. Whilst effective, the typical uncertainties associated with boulder dating methods (±10%) preclude the investigation of short-term (e.g. ≤ centennial-scale) glacier and/or climatic change(s), which are shown to be important at modern ice-margins. Moreover, moraine chronologies are fragmentary, and inherently biased towards episodes of positive glacier mass balance (i.e. moraine construction), and thus limit our understanding of ice sheet retreat dynamics. By contrast, long, continuous, high-resolution (i.e. varve) palaeolimnological records have the potential to significantly refine models of ice sheet deglaciation. In this talk, we present data from Valle Fenix Chico, in the Lago Buenos Aires (LBA) basin (-46.57°S -71.07°W), in which ice-contact Glacial Lake Buenos Aires formed as the LBA ice lobe of Patagonian ice sheet withdrew from its innermost LGM moraine (~17.2 ± 0.9 ka). Thick (>40m) sequences of laminated glaciolacustrine sediment were deposited in the palaeolake, and are now exposed in a sub-aerial canyon that was cut when the lake drained. We report on the detailed macro- and micro-facies of the LBA sediments. In particular, we: (1) develop a process model for the formation of silt and clay couplets, which suggests an annual (varve) origin; (2) present varve series for the initial phase (~1kyr) of LBA ice lobe deglaciation.

  14. Improving age constraints on Patagonian glaciations using a new luminescence dating method for feldspars

    NASA Astrophysics Data System (ADS)

    Smedley, R. K.; Glasser, N. F.; Duller, G. A.

    2013-12-01

    Multiple moraine ridges are preserved in the Lago Buenos Aires and Lago Pueyrrédon valleys, east of the Northern Patagonian Icefield and offer a unique perspective on understanding past environmental change in the mid-latitudes of the Southern Hemisphere. Previous age constraints provided for the moraine ridges relies on cosmogenic isotope dating and constraining radiocarbon and 40Ar/36Ar ages. Providing age constraints using luminescence dating of the glaciofluvial landforms associated with the moraine ridges offers great potential to contribute towards improving the accuracy and precision of age constraints in such challenging glacial settings. This is the first study to use a new luminescence dating method recently developed for feldspars (Thomsen et al. 2008) to constrain the ages of moraine deposition. A range of sediments were sampled from the outwash plains and glaciofluvial channels that are associated with moraine deposition in the Lago Buenos Aires and Lago Pueyrrédon valleys. Elevation measurements and the geomorphological context of the outwash plains and glaciofluvial channels are used to relate the sampled material to the associated moraine ridges, and therefore constrain the ages of moraine deposition in the valleys. Moraine ridges dated using cosmogenic isotope dating to the Last Glacial Maximum are the main focus of this study, but the overall aim is to provide a new dating technique that can be used to understand the temporal and spatial extent of terrestrial environmental change during past glaciations of the mid-latitudes in the Southern Hemisphere. Thomsen, K.J., Murray, A.S., Jain, M. and Bøtter-Jensen, L. 2008. Laboratory fading rates of various luminescence signals from feldspar-rich sediment extracts. Radiation Measurements 43, 1474 - 1486.

  15. Seismic exploration system

    SciTech Connect

    White, A.H.

    1983-02-08

    Seismic exploration method in arctic regions involving the generation of a seismic disturbance in the water beneath the ice in areas where conventional marine and land exploration methods are functionally inadequate. Seismic disturbances are generated by an air gun assembly which automatically executes lowering air guns through apertures in the ice and retrieving them while carrying out preventive measures against freeze-ups. Seismic sensing and recording equipment are positioned within an appropriate range to detect seismic data in the form of reflective or diffractive signals generated in response to the seismic disturbance after actuating the air gun array, wherein the seismic data is indicative of sub-surface structural formations existing below the body of water.

  16. Baylisascaris procyonis encephalitis in Patagonian conures (Cyanoliseus patagonus), crested screamers (Chauna torquata), and a western Canadian porcupine (Erethizon dorsatum epixanthus) in a Manitoba zoo

    PubMed Central

    Thompson, Amy B.; Glover, Gordon J.; Postey, Rosemary C.; Sexsmith, Jennifer L.; Hutchison, Thomas W.S.; Kazacos, Kevin R.

    2008-01-01

    Neurological disease occurred in 4 Patagonian conures (Cyanoliseus patagonus), 2 crested screamer chicks (Chauna torquata), and 1 western Canadian porcupine (Erethizon dorsatum epixanthus) at a Manitoba zoo. Baylisascaris procyonis, the common raccoon roundworm, not previously identified in Manitoba, is considered the likely cause of neural larval migrans in these cases. PMID:19043485

  17. Hydroacoustical evidence of the expansion of pelagic swarms of Munida gregaria (Decapoda, Munididae) in the Beagle Channel and the Argentine Patagonian Shelf, and its relationship with habitat features

    NASA Astrophysics Data System (ADS)

    Diez, Mariano J.; Cabreira, Ariel G.; Madirolas, Adrián; Lovrich, Gustavo A.

    2016-08-01

    Squat lobsters are highly diversified and widespread decapods, of which only three species form pelagic swarms. Here we infer the expansion of Munida gregaria populations in the Beagle Channel and the Argentine Patagonian Shelf by means of acoustic surveys of pelagic swarms. We also describe the habitat characteristics in which these swarms occur. Acoustic data was collected during three multidisciplinary scientific cruises on board of the R/V Puerto Deseado during 2009, 2012 and 2014. Despite differences in the environmental conditions between the two surveyed areas, between 2009 and 2014 pelagic swarms increased their occurrence and abundance both in the Beagle Channel and on the Argentine Patagonian Shelf. Towards the end of the studied period, pelagic swarms of M. gregaria occurred in new locations, supporting the notion of a population expansion. Within the Beagle Channel swarm expansions were more marked than on the Patagonian Shelf. We here postulate that M. gregaria expansions occur in association with productive areas of the Argentine continental shelf, such as frontal zones, favoured by the squat lobster phenotypic plasticity that permit to exploit resources in both the neritic and benthic environments. At a regional scale on the Patagonian Shelf, three main groups of pelagic swarms of M. gregaria were clearly associated to respective frontal zones. The information presented here is necessary to understand fluctuations in both distribution and abundance patterns of a key species on the Argentine continental shelf. These fluctuations could be direct or indirect indicators of changes in the ecosystem.

  18. Baylisascaris procyonis encephalitis in Patagonian conures (Cyanoliseus patagonus), crested screamers (Chauna torquata), and a western Canadian porcupine (Erethizon dorsatum epixanthus) in a Manitoba zoo.

    PubMed

    Thompson, Amy B; Glover, Gordon J; Postey, Rosemary C; Sexsmith, Jennifer L; Hutchison, Thomas W S; Kazacos, Kevin R

    2008-09-01

    Neurological disease occurred in 4 Patagonian conures (Cyanoliseus patagonus), 2 crested screamer chicks (Chauna torquata), and 1 western Canadian porcupine (Erethizon dorsatum epixanthus) at a Manitoba zoo. Baylisascaris procyonis, the common raccoon roundworm, not previously identified in Manitoba, is considered the likely cause of neural larval migrans in these cases.

  19. Metabolic and molecular characterization of bacterial community associated to Patagonian Chilean oligotrophic-lakes of quaternary glacial origin.

    PubMed

    Leon, Carla; Campos, Víctor; Urrutia, Roberto; Mondaca, María-Angélica

    2012-04-01

    The Patagonian Lakes have particular environmental conditions with or without intermittent disturbances. The study of the microorganisms present in aquatic ecosystems has increased notably because they can be used as micro-scale bioindicators of, among others, anthropogenic pollution and climatic change. The aim of the work was to compare the composition of the bacterial communities associated with sediments of three Patagonian Lakes with different geomorphologic patterns and disturbances. The lake sediments were characterized by molecular techniques, physiology profiles and physico-chemical analyses. The metabolic and physiological profiles of the microbial community demonstrated that non-impacted Tranquilo Lake is statistically different to impacted Bertrand and Plomo Lakes. Similar results were detected by DGGE profiles. FISH results demonstrated that betaproteobacteria showed the highest count in the Tranquilo Lake while gammaproteobacteria showed the highest counts in the Bertrand and Plomo Lakes, indicating that their sediments are highly dystrophic. The results demonstrate differences in the metabolic activity and structural and functional composition of bacterial communities of the studied lakes, which have different geomorphological patterns due to disturbances such as volcanic activity and the climatic change.

  20. Overland flow from plant patches: Coupled effects of preferential infiltration, surface roughness and depression storage at the semiarid Patagonian Monte

    NASA Astrophysics Data System (ADS)

    Rossi, María J.; Ares, Jorge O.

    2016-02-01

    The objective of this study is to characterize and quantify the overland flow generated from the plant patch areas of spotted vegetation toward the immediate surrounding bare ground including the coupled effects of preferential infiltration, surface roughness and depression storage. To this aim a series of overland flow plot experiments were designed in areas of the Patagonian Monte where evidence of patch-to-soil overland flow was observed. The experiments produced data on the plot micro-topography and physical properties of the soil, root density and the frictional parameters of the overland flow as well as the extent of the areas of water depression storage. The obtained data were used to calibrate a spatial-explicit (CREST) hydrological model of the flows and pathways generated by stemflow and throughfall during characteristic storms in the area. Good agreement between the model estimates and the measured data was found. This work provides physically-based metrics of runoff redistribution from the plant patch areas toward the immediate surrounding bare soil areas, including the effect of plant roots and depression storage as influenced by various shapes of the plant patch slopes. It is concluded that water transport can result from stemflow and throughfall at the patch areas during typical rainfall events at the semiarid Patagonian Monte. Implications of this phenomenon in the surface distribution of water, nutrients and seeds may feasibly follow.

  1. The Sarcophaginae (Diptera: Sarcophagidae) of Southern South America. I. The species of Microcerella Macquart from the Patagonian Region.

    PubMed

    Mulieri, Pablo Ricardo; Mariluis, Juan Carlos; Patitucci, Luciano Damián; Olea, María Sofía

    2015-03-17

    A revision is given of the species placed in the genus Microcerella Macquart, known from the southern extreme of South America, the so-called Patagonian Region. A new diagnosis of the genus is given on the basis of the revision of a large number of Neotropical species. A total of 25 valid species are recognized in the region. Most of these (21 species) are divided into four species-groups on the basis of general groundplan of genitalia and external characters. Four new species are described, M. deliae sp. nov., M. holmbergi sp. nov., M. nataliae sp. nov. and M. paetoi sp. nov. One new synonymy is established: Austrohartigia shannoni Lopes as a new junior synonym of Microcerella spinosa (Hall), syn. nov. A lectotype is designated for Doringia subandina Blanchard [a junior synonym of Microcerella spinigena (Rondani)]. Two species are recorded from Argentina for the first time: M. chicoensis (Lopes) and M. engeli (Hall). Three nominal species were not examined and are treated as nomina dubia within Microcerella: M. apicalis (Townsend), M. rufomaculata Macquart and M. sarcophagina Thomson. An illustrated key is provided to the males of Patagonian species of Microcerella allowing for separation of 25 species. Additionally, a series of images of male genitalia based on color photography and illustrations is provided to aid in the identification of these species of Microcerella. Biological information is given for the species, where known.

  2. Lower Pliensbachian caldera volcanism in high-obliquity rift systems in the western North Patagonian Massif, Argentina

    NASA Astrophysics Data System (ADS)

    Benedini, Leonardo; Gregori, Daniel; Strazzere, Leonardo; Falco, Juan I.; Dristas, Jorge A.

    2014-12-01

    In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén Basin and the North Patagonian Massif, the Garamilla Formation is composed of four volcanic stages: 1) andesitic lava-flows related to the beginning of the volcanic system; 2) basal massive lithic breccias that represent the caldera collapse; 3) voluminous, coarse-crystal rich massive lava-like ignimbrites related to multiple, steady eruptions that represent the principal infill of the system; and, finally 4) domes, dykes, lava flows, and lava domes of rhyolitic composition indicative of a post-collapse stage. The analysis of the regional and local structures, as well as, the architectures of the volcanic facies, indicates the existence of a highly oblique rift, with its principal extensional strain in an NNE-SSW direction (˜N10°). The analyzed rocks are mainly high-potassium dacites and rhyolites with trace and RE elements contents of an intraplate signature. The age of these rocks (189 ± 0.76 Ma) agree well with other volcanic sequences of the western North Patagonian Massif, as well as, the Neuquén Basin, indicating that Pliensbachian magmatism was widespread in both regions. The age is also coincident with phase 1 of volcanism of the eastern North Patagonia Massif (188-178 Ma) represented by ignimbrites, domes, and pyroclastic rocks of the Marifil Complex, related to intraplate magmatism.

  3. Traveling around Cape Horn: Otolith chemistry reveals a mixed stock of Patagonian hoki with separate Atlantic and Pacific spawning grounds

    USGS Publications Warehouse

    Schuchert, P.C.; Arkhipkin, A.I.; Koenig, A.E.

    2010-01-01

    Trace element fingerprints of edge and core regions in otoliths from 260 specimens of Patagonian hoki, Macruronus magellanicus L??nnberg, 1907, were analyzed by LA-ICPMS to reveal whether this species forms one or more population units (stocks) in the Southern Oceans. Fish were caught on their spawning grounds in Chile and feeding grounds in Chile and the Falkland Islands. Univariate and multivariate analyses of trace element concentrations in the otolith edges, which relate to the adult life of fish, could not distinguish between Atlantic (Falkland) and Pacific (Chile) hoki. Cluster analyses of element concentrations in the otolith edges produced three different clusters in all sample areas indicating high mixture of the stocks. Cluster analysis of trace element concentrations in the otolith cores, relating to juvenile and larval life stages, produced two separate clusters mainly distinguished by 137Ba concentrations. The results suggest that Patagonian hoki is a highly mixed fish stock with at least two spawning grounds around South America. ?? 2009 Elsevier B.V.

  4. Long-lasting concentrations of cefovecin after subcutaneous and intramuscular administration to Patagonian sea lions (Otaria flavescens).

    PubMed

    García-Párraga, D; Gilabert, J A; García-Peña, F J; Álvaro, T; Ros-Rodríguez, J M; Valls, M; Encinas, T

    2016-02-01

    Cefovecin is a third-generation cephalosporin developed as an aqueous solution for use by the subcutaneous route in dogs and cats. This study evaluated the duration of cefovecin plasma concentrations after single intramuscular (IM) or subcutaneous (SC) injection at different doses in 10 Patagonian sea lions (Otaria flavescens). Blood samples were collected serially from the day of the injection up to 60-90 days post-injection. Plasma drug concentrations were determined by high performance liquid chromatography-UV detection and pharmacokinetic parameters were calculated by non-compartmental analysis. No reactions or side effects associated with the drug were observed in any of the studied animals. Both routes showed very similar pharmacokinetic behaviour. Elimination half-life (11.3-21.6 days, SC; 13.1-15.9 days, IM) and mean residence time (17.6-36.8 days SC; 16.5-25.4 days IM) were, in all cases and doses, considerably longer than those previously reported for any other species. Based on these findings, and preliminary data on specific pathogen sensitivity, cefovecin was found to be a very promising antimicrobial for Patagonian sea lions, in particular those that are difficult to access or that are under certain rehabilitation conditions. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. Infection with Toxoplasma gondii in a red kangaroo (Macropus rufus) and a Patagonian mara (Dolichotis patagonum) in captivity.

    PubMed

    Díaz-Ayala, Nataly; Hidalgo-Hermoso, Ezequiel; Cabello-Araya, Constanza; Carvallo-Chaigneau, Francisco

    2016-01-01

    Toxoplasmosis is an infectious, zoonotic and parasitic disease, caused by Toxoplasma gondii. In this manucript, two cases of infection with T. gondii in captive animals from a zoological park in the central region of Chile are described. One case was a red kangaroo (Macropus rufus), which is highly susceptible to the infection, and the other was a Patagonian mara (Dolichotis patagonum), a rodent in which there is no previous report of the infection. Both animals had myocarditis, with the presence of intralesional tachizoites and cysts suggestive of infection with T. gondii. This infection was confirmed by immunohistochemistry in both animals. The origin of the infection is unknown, but it is likely that free ranging domestic felines were associated with the dissemination of the parasites. This highlights the importance of controlling the domestic animal populations in zoological parks. To the best of our knowledge, this is the first time that T. gondii infection is described in a Patagonian mara, adding a new host for this infectious agent.

  6. From gelatinous to muscle food chain: rock cod Patagonotothen ramsayi recycles coelenterate and tunicate resources on the Patagonian Shelf.

    PubMed

    Arkhipkin, A; Laptikhovsky, V

    2013-11-01

    Stomach contents of 4808 fishes of 20 species caught in the eastern part of the Patagonian Shelf between 1999 and 2012 were analysed to assess dietary contributions of gelatinous plankton resources. Gelatinous plankton occurred in diets of seven species with two species, Patagonotothen ramsayi and Squalus acanthias, having >10% ctenophores in their diet. Consumption of gelatinous plankton was important in P. ramsayi and was strikingly seasonal, with maximum occurrence (up to 46% of non-empty stomachs) in late summer to autumn. Ctenophores were most abundant in P. ramsayi of 25-34 cm total length, L(T) whereas salps were more frequent in larger >35 cm L(T) individuals. In winter to spring, occurrence of gelatinous plankton in diets was minimal, reflecting their overall seasonal abundance in the ocean. The recent increase in abundance of P. ramsayi has enabled the species to recycle a significant proportion of the ecosystem production from gelatinous dead end to the main muscular food chain via seasonal reliance on ctenophores, jellyfish and tunicates. This additional influx of production that has been diverted from the gelatinous food chain favours the increase in abundance of several piscivorous top predators and affects the trophic web structure of the Patagonian Shelf ecosystem. © 2013 The Fisheries Society of the British Isles.

  7. The Patagonian Orocline: Paleomagnetic evidence of a large counter-clockwise rotation during the closure of the Rocas Verdes basin.

    NASA Astrophysics Data System (ADS)

    Poblete, Fernando; Roperch, Pierrick; Herve, Francisco; Ramirez, Cristobal; Arriagada, Cesar

    2014-05-01

    The southernmost Andes of Patagonia and Tierra del Fuego present a prominent arc-shaped structure, the Patagonian Orocline. Despite the fact that this major structure was already described by Alfred Wegener in his famous textbook in 1929, few paleomagnetic studies have been attempted to describe the rotations associated with the formation of the Patagonian Orocline. In this study we present a paleomagnetic and anisotropy of magnetic susceptibility (AMS) study from more than 130 sites obtained from the Ultima Esperanza region (NS structures at ~51°S) to Península Hardy, south of the Beagle Channel at ~55°S. 45 sites were sampled in early-cretaceous gabbros (gabbro complex), mid-cretaceous tonalites and granodiorites (Canal Beagle group) and Paleocene intrusive rocks (Seno Año Nuevo group) from the South Patagonian batholith, 4 sites from the late Jurassic Hardy formation, a volcanic succession outcropping in Hardy Peninsula and Stewart Island, 9 sites were drilled in the lower cretaceous sedimentary infill of the Rocas Verdes Basin, 3 sites from the Tortuga ophiolite, a quasi-oceanic crust related to the opening of the Rocas Verdes basin. 80 sites were sampled in Cretaceous to Miocene sedimentary rocks from the Magallanes fold and thrust belt and Magallanes Basin. Characteristic Remanent Magnetizations (ChRMs) obtained from the Rocas Verdes Basin tectonic province correspond to secondary magnetizations postdating the early phase of folding. Pyrrhotite is the main magnetic carrier in some of these sites. ChRMs from the South Patagonian Batholith correspond to a primary magnetization. These rocks record about 90° counterclockwise rotations south of the Beagle channel. Few sites from sediments of the Magallanes fold and thrust belt have stable ChRM. The available paleomagnetic results show that no rotation has occurred in the Provincia of Ultima Esperanza (51.5°S), at least, for the last 60 Ma. In the southern part of Provincia de Magallanes and Tierra del Fuego

  8. Angola Seismicity MAP

    NASA Astrophysics Data System (ADS)

    Neto, F. A. P.; Franca, G.

    2014-12-01

    The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

  9. A model-based telecoupling analysis for the Patagonian shelf: a new suggested template on how to study global seabirds-fisheries interactions for sustainability

    NASA Astrophysics Data System (ADS)

    Huettmann, F.; Raya Rey, A.

    2016-12-01

    The Southwest Atlantic Ocean, and the extended Patagonian shelf in particular, presents us with a very complex ecosystem of global relevance for food security and global peace. It is a highly productive area and it maintains a great diversity and abundance of seabird species. Fisheries have been identified as a main stressor for the marine ecosystems and as one of the main causes of seabird population declines. Using the framework of telecoupling - a sophisticated description of natural and socioeconomic interactions over large distances - here we present a fresh holistic look at the dynamic fisheries and (endangered) seabird interactions for the Patagonian shelf. While data are sparse, we employ machine learning-based predictions for a more holistic overview. We found that these waters of the Patagonian Shelf are significantly affected by many nations and outside players. We found that the input, output and spill-over of the Patagonian shelf ecosystem are distributed virtually all over the globe. In addition, we also found `losers' (=nations and their citizens that are left out entirely from this global resource and its governance). Our findings are based on best-available public trade and fish harvest analysis for this region, linked with predictive modeling (machine learning and geographic information systems GIS) to generalize for nine seabird species. We conveniently extend this analysis with a perspective from the financial sector and policy that enables the Patagonian fisheries as international investment and development projects. As increasingly recognized elsewhere, we believe that telecoupling can serve as a new but rather sophisticated study template highlighting wider complexities, bottlenecks and sensitivities for a vastly improved conservation research on oceans and global sustainability questions.

  10. New Madrid Seismic Zone

    DTIC Science & Technology

    2007-11-02

    NEW MADRID SEISMIC ZONE BY COLONEL J.DAVID NORWOOD United States Army DISTRIBUTION STATEMENT A...mCTBB l USAWC STRATEGY RESEARCH PROJECT New Madrid Seismic Zone by J. David Norwood, COL, USA Michael A. Pearson, COL, USA Project Advisor The...ABSTRACT AUTHOR: J. David Norwood, Colonel, U.S. Army TITLE: New Madrid Seismic Zone FORMAT: Strategy Research Project DATE: 22 April 1998 . PAGES:

  11. Seismic Imaging and Monitoring

    SciTech Connect

    Huang, Lianjie

    2012-07-09

    I give an overview of LANL's capability in seismic imaging and monitoring. I present some seismic imaging and monitoring results, including imaging of complex structures, subsalt imaging of Gulf of Mexico, fault/fracture zone imaging for geothermal exploration at the Jemez pueblo, time-lapse imaging of a walkway vertical seismic profiling data for monitoring CO{sub 2} inject at SACROC, and microseismic event locations for monitoring CO{sub 2} injection at Aneth. These examples demonstrate LANL's high-resolution and high-fidelity seismic imaging and monitoring capabilities.

  12. Seismic Waveguide of Metamaterials

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Hoon; Das, Mukunda P.

    We developed a new method of an earthquake-resistant design to support conventional aseismic system using acoustic metamaterials. The device is an attenuator of a seismic wave that reduces the amplitude of the wave exponentially. Constructing a cylindrical shell-type waveguide composed of many Helmholtz resonators that creates a stop-band for the seismic frequency range, we convert the seismic wave into an attenuated one without touching the building that we want to protect. It is a mechanical way to convert the seismic energy into sound and heat.

  13. Geodetic mass balance of the Patagonian Icefields from STRM and TanDEM-X DEMs

    NASA Astrophysics Data System (ADS)

    Abdel Jaber, W.; Floricioiu, D.; Rott, H.

    2016-12-01

    The Northern and Southern Patagonian Icefields (NPI & SPI), represent the largest mid-latitude ice masses in the Southern Hemisphere. They are mostly drained by outlet glaciers with fronts calving into fresh water lakes or Pacific fjords. Both icefields were affected by significant downwasting in the last decades, as confirmed by published mass change trends obtained by means of gravimetric measurements and geodetic methods. Given their unique characteristics and the significant contribution to sea level rise per unit of area, they represent a fundamental barometer for climate research. The Shuttle Radar Topography Mission (SRTM) of 2000 provided the most complete and accurate Digital Elevation Model (DEM) at the time covering the entire globe from 56°S to 60°N. The present TanDEM-X mission shares the same objective aiming at a global coverage with much higher resolution and accuracy. Their combination leads to a unique multitemporal elevation dataset based solely on SAR single pass bistatic interferometry characterized by 11 to 16 year time span: an ideal setup for monitoring long-term large-scale geophysical phenomena. Using this dataset, detailed and extensive ice elevation change maps were obtained for the 12900 km² SPI for the observation period 2000 - 2011/2012 and for the 3900 km² NPI for the period 2000 - 2014. These maps were used to compute the glacier mass balance of the icefields through the geodetic method. Particular emphasis was set on the estimation of the uncertainty of the geodetic mass balance by quantifying all relevant sources of error. Among these, signal penetration into dry ice and snow can affect considerably radar elevation measurements. For this purpose the backscattering coefficient of the acquisitions along with concurrent meteorological data were analyzed to assess the conditions of the icefield surface. Mass change rates of -3.96±0.14 Gt a-1 and of -13.14±0.42 Gt a-1 (excluding subaqueous loss) were obtained for NPI and SPI

  14. Spring plankton communities in the southern Patagonian shelf: Hydrography, mesozooplankton patterns and trophic relationships

    NASA Astrophysics Data System (ADS)

    Sabatini, M. E.; Akselman, R.; Reta, R.; Negri, R. M.; Lutz, V. A.; Silva, R. I.; Segura, V.; Gil, M. N.; Santinelli, N. H.; Sastre, A. V.; Daponte, M. C.; Antacli, J. C.

    2012-06-01

    A strong interest in the southern Patagonian shelf has emerged in recent years, along with the increasing recognition of its high biological productivity. Knowledge of the pelagic food web structure that supports the richness of this system is still developing, but there are indications that mesozooplankton occupy a pivotal position, as consumers of smaller plankton and as vital prey for fish and squid. All plankton communities in the size 2 μm-20 mm, total and size-fractioned chlorophyll a (Chl a), nutrients and hydrology were surveyed simultaneously in October 2005 between 47°S-55°S. Picoplankton, nanoplankton and microplankton were taxonomically and functionally (autotrophs, heterotrophs) sorted within each size fraction. Plankton data and trophic relationships were examined through multivariate statistics. At that time fairly homogeneous thermal conditions prevailed over most of the shelf but weak saline horizontal gradients were evident. N/P ratios indicated no N or P limitation for phytoplankton. Surface concentrations of total Chl a were particularly high in the Grande Bay area at ca. 51°S near shore (28.6 mg m- 3) and at ca. 47°S on the shelf-break (7.7 mg m- 3). At both locations the contribution of the Chl a > 5 μm fraction was remarkably high. The dinoflagellate Prorocentrum minimum (10 · 106 cells L- 1) and the diatom Thalassiosira cf. oceanica (1.3 · 106 cells L- 1) were respectively blooming at these sites. Otherwise < 10 μm plankton prevailed overall. Copepods largely dominated the > 200 μm fraction. Three mesozooplankton assemblages typical of the inner, middle, and outer shelf were identified. The inner and middle shelf assemblages overlapped slightly but were spatially separated from the outer shelf community. Adults and late copepodids of Drepanopus forcipatus were typical of the inner shelf assemblage. Middle-shelf species included the copepod Ctenocalanus vanus, the amphipod Themisto gaudichaudii and the chaetognath Sagitta tasmanica

  15. Soil water availability and rooting depth as determinants of hydraulic architecture of Patagonian woody species.

    PubMed

    Bucci, Sandra J; Scholz, Fabian G; Goldstein, Guillermo; Meinzer, Frederick C; Arce, Maria E

    2009-07-01

    Adaptations of species to capture limiting resources is central for understanding structure and function of ecosystems. We studied the water economy of nine woody species differing in rooting depth in a Patagonian shrub steppe from southern Argentina to understand how soil water availability and rooting depth determine their hydraulic architecture. Soil water content and potentials, leaf water potentials (Psi(Leaf)), hydraulic conductivity, wood density (rho(w)), rooting depth, and specific leaf area (SLA) were measured during two summers. Water potentials in the upper soil layers during a summer drought ranged from -2.3 to -3.6 MPa, increasing to -0.05 MPa below 150 cm. Predawn Psi(Leaf) was used as a surrogate of weighted mean soil water potential because no statistical differences in Psi(Leaf) were observed between exposed and covered leaves. Species-specific differences in predawn Psi(Leaf) were consistent with rooting depths. Predawn Psi(Leaf) ranged from -4.0 MPa for shallow rooted shrubs to -1.0 MPa for deep-rooted shrubs, suggesting that the roots of the latter have access to abundant moisture, whereas shallow-rooted shrubs are adapted to use water deposited mainly by small rainfall events. Wood density was a good predictor of hydraulic conductivity and SLA. Overall, we found that shallow rooted species had efficient water transport in terms of high specific and leaf specific hydraulic conductivity, low rho(w), high SLA and a low minimum Psi(Leaf) that exhibited strong seasonal changes, whereas deeply rooted shrubs maintained similar minimum Psi(Leaf) throughout the year, had stems with high rho(w) and low hydraulic conductivity and leaves with low SLA. These two hydraulic syndromes were the extremes of a continuum with several species occupying different portions of a gradient in hydraulic characteristics. It appears that the marginal cost of having an extensive root system (e.g., high rho(w) and root hydraulic resistance) contributes to low growth rates

  16. Deep divers in shallow seas: Southern elephant seals on the Patagonian shelf

    NASA Astrophysics Data System (ADS)

    Campagna, Claudio; Piola, Alberto R.; Marin, Maria Rosa; Lewis, Mirtha; Zajaczkovski, Uriel; Fernández, Teresita

    2007-10-01

    Elephant seals are wide-ranging, pelagic, deep-diving (average of 400-600 m) predators that typically travel to open waters and continental shelf edges thousands of kilometers from their land breeding colonies. We report a less common pattern of foraging in the shallow waters of a continental shelf. Southern elephant seals, Mirounga leonina, that breed at Península Valdés (Argentina), face an extended (˜1,000,000 km 2; 400-700 km-wide, depending on track), shallow (<150 m) and seasonally productive plateau, the Patagonian shelf. Adults of both sexes usually cross it in rapid transit to other potential foraging grounds on the shelf edge or in the Argentine Basin, but 2-4 year-old juveniles spread over the plateau and spent months in shallow waters. This behavior was recorded for 9 seals (5 males and 4 females) of 23 satellite-tracked juveniles (springs of 2004 and 2005) and for 2 subadult males studied in previous seasons. Trips included travel trajectories and time spent in areas where swim speed decreased, suggesting foraging. Preferred locations of juvenile females were in the proximity of the shelf break, where stratified waters had relatively high phytoplankton concentrations, but young and subadult males used the relatively cold (7-8 °C), low-salinity (˜33.3) mid-shelf waters, with depths of 105-120 m and a poorly stratified water column. Three of the latter seals, instrumented with time-depth recorders, showed dives compatible with benthic feeding and no diel pattern of depths distribution. Regions of the mid-shelf were used in different seasons and were associated with low chlorophyll- a concentration at the time of the visit, suggesting that surface productivity does not overlap with putative quality habitat for benthic foragers. Benthic diving on the shallow mid-shelf would be a resource partitioning strategy advantageous for young males prior to greater energetic demands of a high growth rate and a large body size. Later in life, the more predictable

  17. The South Patagonian batholith: 150 my of granite magmatism on a plate margin

    NASA Astrophysics Data System (ADS)

    Hervé, F.; Pankhurst, R. J.; Fanning, C. M.; Calderón, M.; Yaxley, G. M.

    2007-09-01

    A new database of 70 U-Pb zircon ages (mostly determined by SHRIMP) indicates that the South Patagonian batholith resulted from the amalgamation of subduction-related plutons from the Late Jurassic to the Neogene. Construction of the batholith began with a voluminous, previously undetected, Late Jurassic bimodal body mainly composed of leucogranite with some gabbro, emplaced along its present eastern margin within a restricted time span (157 to 145 Ma). This episode is, at least in part, coeval with voluminous rhyolitic ignimbrites of the Tobífera Formation, deposited in the deep Rocas Verdes Basin east of the batholith; this was the last of several southwestward-migrating silicic volcanic episodes in Patagonia that commenced in an Early Jurassic extensional tectonic regime. The quasi-oceanic mafic floor of the basin was also contemporaneous with this Late Jurassic batholithic event, as indicated by mutually cross-cutting field relationships. Changes in subduction parameters then triggered the generation of earliest Cretaceous plutons (Cretaceous 1: 144-137 Ma) west of the Late Jurassic ones, a westward shift that culminated at 136-127 Ma (Cretaceous 2) along the present western margin of the batholith. Most mid- to Late Cretaceous (Cretaceous 3: 126-75 Ma) and Paleogene (67-40 Ma) granitoids are represented by geographically restricted plutons, mainly emplaced between the previously established margins of the batholith, and mostly in the far south; no associated volcanic rocks of similar age are known at present in this area. During the final Neogene stage of plutonism (25-15 Ma) a recurrence of coeval volcanism is recognized within and east of the batholith. Typical ɛNdt values for the granitoids vary from strongly negative (- 5) in the Late Jurassic, to progressively higher values for Cretaceous 1 (- 4), Cretaceous 2 (- 0.7), Cretaceous 3 (+ 2) and the Paleogene (+ 5), followed by lower and more variable ones in the Neogene (- 1 to + 5). These variations may

  18. Holocene activity of the Liquiñe-Ofqui Fault Zone near Aysén Fjord (Chilean Patagonia)

    NASA Astrophysics Data System (ADS)

    Wils, Katleen; Van Daele, Maarten; Lastras, Galderic; Kissel, Catherine; Lamy, Frank; Vanneste, Kris; Siani, Giuseppe

    2017-04-01

    In the first months of 2007, the Aysén region in southern Chile was affected by a seismic swarm with more than 7,200 recorded earthquakes. Its largest earthquake (M 6.2) occurred in April, and had its epicenter in Aysén fjord. Ground shaking intensities became so high (up to MMI IX) that hundreds of onshore mass movements were triggered, several of which entered into the fjord, resulting in mass-transport deposits (MTDs) preserved at the fjord bottom. Here we present a Holocene record of past earthquakes in the, up to now, unstudied Patagonian fjordland based on MTD stratigraphy. High-resolution seismic data retrieved using two different seismic sources (sparker and TOPAS) revealed multiple older MTDs on different stratigraphic levels. Correlation of the seismic stratigraphy with sedimentological data obtained from a long Calypso core (MD07-3117) provided conclusive identification of these deposits as to whether or not they were seismically triggered. Additionally, radiocarbon dating allowed to reconstruct an age model, which was validated by tephrochronology, providing an age for the different MTD levels. Moreover, the distribution of the MTDs in the fjord, combined with ground-motion modelling, allowed estimating potential source faults and rupture areas for each of the prehistorical events. We thus present a highly detailed paleoseismological history of the Aysén region, including at least six major Holocene earthquakes with possibly also different source mechanisms and areas. Even though earthquakes do not seem to have occurred at regular time intervals, an average recurrence time of 2,000 years can be inferred for earthquakes with a minimum shaking intensity of MMI VI.

  19. Seismic Catalogue and Seismic Network in Haiti

    NASA Astrophysics Data System (ADS)

    Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.

    2013-05-01

    The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address seismic phenomena. At the moment of the earthquake, there was no seismic network operating in the country, and only a partial control of the past seismicity was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a seismic catalogue providing the necessary input for seismic Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a seismic catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the seismic network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian System CARINA. In 2012, the Spanish IGN together

  20. Understanding the transport of Patagonian dust and its influence on marine biological activity in the South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Johnson, M. S.; Meskhidze, N.; Kiliyanpilakkil, V. P.; Gassó, S.

    2011-03-01

    The supply of bioavailable iron to the high-nitrate low-chlorophyll (HNLC) waters of the Southern Ocean through atmospheric pathways could stimulate phytoplankton blooms and have major implications for the global carbon cycle. In this study, model results and remotely-sensed data are analyzed to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of iron-laden mineral dust deposition on marine biological productivity in the surface waters of the South Atlantic Ocean (SAO). Model simulations for the atmospheric transport and deposition of mineral dust and bioavailable iron are carried out for two large dust outbreaks originated at the source regions of northern Patagonia during the austral summer of 2009. Model-simulated horizontal and vertical transport pathways of Patagonian dust plumes are in reasonable agreement with remotely-sensed data. Simulations indicate that the synoptic meteorological patterns of high and low pressure systems are largely accountable for dust transport trajectories over the SAO. According to model results and retrievals from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), synoptic flows caused by opposing pressure systems (a high pressure system located to the east or north-east of a low pressure system) elevate the South American dust plumes well above the marine boundary layer. Under such conditions, the bulk concentration of mineral dust can quickly be transported around the low pressure system in a clockwise manner, follow the southeasterly advection pathway, and reach the HNLC waters of the SAO and Antarctica in ~3-4 days after emission from the source regions of northern Patagonia. Two different mechanisms for dust-iron mobilization into a bioavailable form are considered in this study. A global 3-D chemical transport model (GEOS-Chem), implemented with an iron dissolution scheme, is employed to estimate the atmospheric fluxes of soluble iron, while a

  1. Understanding the transport of Patagonian dust and its influence on marine biological activity in the South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Johnson, M. S.; Meskhidze, N.; Kiliyanpilakkil, V. P.; Gassó, S.

    2010-11-01

    The supply of bioavailable iron to the high-nitrate low-chlorophyll (HNLC) waters of the Southern Ocean through atmospheric pathways could stimulate phytoplankton blooms and have major implications for the global carbon cycle. In this study, model results and remotely-sensed data are analyzed to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of iron-laden mineral dust deposition on marine biological productivity in the surface waters of the South Atlantic Ocean (SAO). Model simulations for the atmospheric transport and deposition of mineral dust and bioavailable iron are carried out for two large dust outbreaks originated at the source regions of Northern Patagonia during the austral summer of 2009. Model-simulated horizontal and vertical transport pathways of Patagonian dust plumes are in reasonable agreement with remotely-sensed data. Simulations indicate that the synoptic meteorological patterns of high and low pressure systems are largely accountable for dust transport trajectories over the SAO. According to model results and retrievals from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), synoptic flows caused by opposing pressure systems (a high pressure system located to the east or north-east of a low pressure system) elevate the South American dust plumes well above the marine boundary layer. Under such conditions, the bulk concentration of mineral dust can quickly be transported around the low pressure system in a clockwise manner, follow the southeasterly advection pathway, and reach the HNLC waters of the SAO and Antarctica in ~3-4 days after emission from the source regions of Northern Patagonia. Two different mechanisms for dust-iron mobilization into a bioavailable form are considered in this study. A global 3-D chemical transport model (GEOS-Chem), implemented with an iron dissolution scheme, is employed to estimate the atmospheric fluxes of soluble iron, while a

  2. Tides and lake-level variations in the great Patagonian lakes: Observations, modelling and geophysical implications.

    NASA Astrophysics Data System (ADS)

    Marderwald, Eric; Richter, Andreas; Horwath, Martin; Hormaechea, Jose Luis; Groh, Andreas

    2016-04-01

    -level time series from Lagos Argentino and Viedma yields the amplitudes and phases of the lake tides for the four major tidal constituents M2, S2, O1 and K1. The maximum amplitude, corresponding to the semi-diurnal moon tide M2 in Lago Argentino, amounts to 3 mm. For the four lakes under investigation the theoretical amplitudes and phases of seven constituents (Q1, O1, P1, K1, N2, M2 and S2) are modelled accounting for the contributions of both the solid earth's body tides and the ocean tidal loading (Marderwald 2014). Both contributions involve a deformation of the earth surface and of the equipotential surfaces of the gravity field. For the load tide computation the global ocean tide model EOT11a (Savcenko and Bosch, 2012) and the Gutenberg-Bullen A earth model (Farrell, 1972) was applied and the conservation of water volume is taken into account. The comparison of the tidal signal extracted from the lake-level observations in Lagos Argentino and Viedma with the lake tide models indicates a phase shift which is most likely explained by an 1 hour phase lag of the employed global ocean tide model in the region of the highly fragmented Pacific coast. REFERENCES: Farrell, W. E., (1972). Deformation of the Earth by Surface Loads. Rev. Geophy. Space Phy., 10(3):761-797. Ivins, E., James, T., 2004. Bedrock response to Llanquihue Holocene and present-day glaciation in southernmost South America. Geophys. Res. Lett. 31 (L24613). Doi:10.1029/2004GL021500. Klemann, V., E. R. Ivins, Z. Martinec, and D. Wolf (2007), Models of active glacial isostasy roofing warm subduction: Case of the South Patagonian Ice Field, J. Geophys. Res., 112, B09405, doi: 10.1029/2006JB004818. Lange, H., Casassa, G., Ivins, E. R., Schröder, L., Fritsche, M., Richter, A., Groh, A., Dietrich, R., (2014). Observed crustal uplift near the Southern Patagonian Icefield constrains improved viscoelastic Earth models. Geophysical Research Letters, DOI: 10.1002/2013GL058419. Marderwald ER, 2014. Modelado de las mareas

  3. SOAR Telescope seismic performance II: seismic mitigation

    NASA Astrophysics Data System (ADS)

    Elias, Jonathan H.; Muñoz, Freddy; Warner, Michael; Rivera, Rossano; Martínez, Manuel

    2016-07-01

    We describe design modifications to the SOAR telescope intended to reduce the impact of future major earthquakes, based on the facility's experience during recent events, most notably the September 2015 Illapel earthquake. Specific modifications include a redesign of the encoder systems for both azimuth and elevation, seismic trigger for the emergency stop system, and additional protections for the telescope secondary mirror system. The secondary mirror protection may combine measures to reduce amplification of seismic vibration and "fail-safe" components within the assembly. The status of these upgrades is presented.

  4. Marine effect of introduced salmonids: Prey consumption by exotic steelhead and anadromous brown trout in the Patagonian Continental Shelf

    USGS Publications Warehouse

    Ciancio, J.; Beauchamp, D.A.; Pascual, M.

    2010-01-01

    On the basis of stable isotope analysis, we estimated the marine diet of the most abundant anadromous salmonid species in Patagonian Atlantic basins. The results were coupled with bioenergetic and population models to estimate the consumption of food by salmonids and was compared with that by seabirds, the most abundant top predators in the area. Amphipods were the main salmonid prey, followed by sprat, silversides, squid, and euphausiids. The total consumption, even assuming large anadromous salmonid populations, represented <5% of the total consumption by seabirds. We also identified the particular seabird colonies and artisanal fisheries with which salmonid trophic interactions at a more local scale could be significant. ?? 2010, by the American Society of Limnology and Oceanography, Inc.

  5. An Alternative Interpretation of Plasma Selenium Data from Endangered Patagonian Huemul Deer ( Hippocamelus bisulcus )

    SciTech Connect

    Flueck, Werner T.; Smith-Flueck, Jo Anne M.; Mincher, Bruce J.; Winkel, Lenny H. H.E.

    2014-10-01

    The prevalence of osteopathology in 57% in the endangered adult Patagonian huemul deer (Hippocamelus bisulcus), malformed antler development, and general lack of recovery were previously suggested to possibly be related to mineral imbalances like selenium (Se) deficiency, and not to stem from fluorosis. From recent bone analyses of these diseased huemul, fluoride levels averaged 58 ppm (SE=10.7), thus eliminating fluorosis as a causal factor for the osteopathology reported in huemul. In contrast, when analyzing high-elevation sites commonly used by extant populations, we found soils deficient in Se. Ashes from recent volcanism also were very low in Se. As Se-responsive diseases in livestock have been documented in Chile, we reclassified recently published Se levels in huemul and determined that 73% were deficient and 18% marginal. Together with these several lines of indirect evidence, we conclude that Se deficiency plays a role in the lack of recovery of huemul populations.

  6. Allocation of biomass and photoassimilates in juvenile plants of six Patagonian species in response to five water supply regimes

    PubMed Central

    Cella Pizarro, Lucrecia; Bisigato, Alejandro J.

    2010-01-01

    Background and Aims The growth–differentiation balance hypothesis (GDBH) states that there is a physiological trade-off between growth and secondary metabolism and predicts a parabolic effect of resource availability (such as water or nutrients) on secondary metabolite production. To test this hypothesis, the response of six Patagonian Monte species (Jarava speciosa, Grindelia chiloensis, Prosopis alpataco, Bougainvillea spinosa, Chuquiraga erinacea and Larrea divaricata) were investigated in terms of total biomass and resource allocation patterns in response to a water gradient. Methods One-month-old seedlings were subjected to five water supply regimes (expressed as percentage dry soil weight: 13 %, 11 %, 9 %, 7 % or 5 % – field water capacity being 15 %). After 150 d, plants were harvested, oven-dried and partitioned into root, stem and leaf. Allometric analysis was used to correct for size differences in dry matter partitioning. Determinations of total phenolics (TP), condensed tannins (CT), nitrogen (N) and total non-structural carbohydrates (TNC) concentrations were done on each fraction. Based on concentrations and biomass data, contents of TP and CT were estimated for whole plants, and graphical vector analysis was applied to interpret drought effect. Key Results Four species (J. speciosa, G. chiloensis, P. alpataco and B. spinosa) showed a decrease in total biomass in the 5 % water supply regime. Differences in dry matter partitioning among treatments were mainly due to size variation. Concentrations of TP, CT, N and TNC varied little and the effect of drought on contents of TP and CT was not adequately predicted by the GDBH, except for G. chiloensis. Conclusions Water stress affected growth-related processes (i.e. reduced total biomass) rather than defence-related secondary metabolism or allocation to different organs in juvenile plants. Therefore, the results suggest that application of the GDBH to plants experiencing drought-stress should be done

  7. Heat-shock response and antioxidant defense during air exposure in Patagonian shallow-water limpets from different climatic habitats.

    PubMed

    Pöhlmann, Kevin; Koenigstein, Stefan; Alter, Katharina; Abele, Doris; Held, Christoph

    2011-11-01

    Climate warming involves not only a rise of air temperature means, but also more frequent heat waves in many regions on earth, and is predicted to intensify physiological stress especially in extremely changeable habitats like the intertidal. We investigated the heat-shock response (HSR) and enzymatic antioxidant defense levels of Patagonian shallow-water limpets, adapted to distinct tidal exposure conditions in the sub- and intertidal. Limpets were sampled in the temperate Northern Patagonia and the subpolar Magellan region. Expression levels of two Hsp70 genes and activities of the antioxidants superoxide dismutase (SOD) and catalase (CAT) were measured in submerged and 2- and 12-h air-exposed specimens. Air-exposed Patagonian limpets showed a tiered HSR increasing from South to North on the latitudinal gradient and from high to low shore levels on a tidal gradient. SOD activities in the Magellan region correlated with the tidal rhythm and were higher after 2 and 12 h when the tide was low at the experimental site compared to the 6 h value taken at high tide. This pattern was observed in intertidal and subtidal specimens, although subtidal individuals are little affected by tides. Our study shows that long-term thermal adaptation shapes the HSR in limpets, while the oxidative stress response is linked to the tidal rhythm. Close to the warm border of their distribution range, energy expenses to cope with stress might become overwhelming and represent one cause why the limpets are unable to colonize the shallow intertidal zone.

  8. Radiocarbon chronology of the late-glacial Puerto Bandera moraines, Southern Patagonian Icefield, Argentina

    NASA Astrophysics Data System (ADS)

    Strelin, J. A.; Denton, G. H.; Vandergoes, M. J.; Ninnemann, U. S.; Putnam, A. E.

    2011-09-01

    We report radiocarbon dates that constrain the timing of the deposition of the late-glacial Puerto Bandera moraine system alongside the western reaches of Lago Argentino adjacent to the Southern Patagonian Icefield. Close maximum-limiting radiocarbon ages ( n = 11) for glacier advance into the outer moraines, with a mean value of 11,100 ± 60 14C yrs BP (12,990 ± 80 cal yrs BP), were obtained from wood in deformation (soft) till exposed beneath flow and lodgment till in Bahía del Quemado on the northeast side of Brazo Norte (North Branch) of western Lago Argentino. Other exposures of this basal deformation till in Bahía del Quemado reveal incorporated clasts of peat, along with larger inclusions of deformed glaciofluvial and lacustrine deposits. Radiocarbon dates of wood included in these reworked peat clasts range from 11,450 ± 45 14C yrs BP to 13,450 ± 150 14C yrs BP (13,315 ± 60 to 16,440 ± 340 cal yrs BP). The implication is that, during this interval, glacier fronts were situated inboard of the Puerto Bandera moraines, with the peat clasts and larger proglacial deposits being eroded and then included in the basal till during the Puerto Bandera advance. Minimum-limiting radiocarbon ages for ice retreat come from basal peat in cores sampled in spillways and depressions generated during abandonment of the Puerto Bandera moraines. Glacier recession and subsequent plant colonization were initiated close behind different frontal sectors of these moraines prior to: 10,750 ± 75 14C yrs BP (12,660 ± 70 cal yrs BP) east of Brazo Rico, 10,550 ± 55 14C yrs BP (12,490 ± 80 cal yrs BP) in Peninsula Avellaneda, and 10,400 ± 50 14C yrs BP (12,280 ± 110 cal yrs BP) in Bahía Catalana. In addition, a radiocarbon date indicates that by 10,350 ± 45 14C yrs BP (12,220 ± 110 cal yrs BP), the Brazo Norte lobe (or former Upsala Glacier) had receded well up the northern branch of Lago Argentino, to a position behind the Herminita moraines. Furthermore, glacier termini

  9. Patagonian and Antarctic dust as recorded in the sediments of Laguna Potrok Aike (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Haberzettl, Torsten; Stopp, Annemarie; Lisé-Pronovost, Agathe; Gebhardt, Catalina; Ohlendorf, Christian; Zolitschka, Bernd; von Eynatten, Hilmar; Kleinhanns, Ilka; Pasado Science Team

    2010-05-01

    Although an increasing number of terrestrial paleoclimatic records from southern South America has been published during the last decade, these archives mostly cover the Lateglacial and/or the Holocene. Only little is known about the Patagonian climate before the Last Glacial Maximum. Here, we present a continuous, high-resolution magnetic susceptibility record for the past 48 ka from the maar lake Laguna Potrok Aike (51°58' S, 70°23' W, southern Patagonia, Argentina). Magnetic susceptibility serves as an excellent parameter for the parallelization of sediment cores all over Laguna Potrok Aike including sediment cores taken within the ICDP (International Continental Scientific Drilling Program) project PASADO (Potrok Aike maar lake Sediment Archive Drilling prOject). Additionally, magnetic susceptibility is assumed to be a proxy for dust deposition in this lake. Distinct similarities were found between the independently dated magnetic susceptibility record from Laguna Potrok Aike and the non-sea-salt calcium (nss-Ca) flux from the EPICA Dome C ice core record (75°06'S, 123°24'E) the latter being a proxy for mineral dust deposition in Antarctica [1]. Comparison of the two records and variations in grain size of the Laguna Potrok Aike sediment records indicate a relatively high aeolian activity in southern South America during the glacial period. During the Holocene climatic conditions driving sediment deposition seem to have been more variable and less dominated by wind compared to glacial times. Although the source of the dust found in Antarctic ice cores often has been attributed to Patagonia [2], we present the first evidence for contemporaneity of aeolian deposition in both the target area (Antarctica) and the major source area (Patagonia). Considering the similarities of the two records, magnetic susceptibility might yield the potential for chronological information: transfer of the ice core age model to a lacustrine sediment record. This would be important

  10. Occurrences of ikaite and pseudomorphs after ikaite in Patagonian lakes - crystal morphologies and stable isotope composition

    NASA Astrophysics Data System (ADS)

    Oehlerich, Markus; Mayr, Christoph; Griesshaber, Erika; Ohlendorf, Christian; Zolitschka, Bernd; Sánchez-Pastor, Nuria; Kremer, Barbara; Lücke, Andreas; Oeckler, Oliver; Schmahl, Wolfgang

    2010-05-01

    Ikaite (CaCO3•6H2O), a hydrated calcium carbonate mineral occasionally found in marine sediments, has so far rarely been reported from non-marine sites. Modern ikaite and calcitic pseudomorphs after ikaite were recently discovered in Patagonian Argentina at the polymictic lakes of Laguna Potrok Aike (51°57´S, 70°23´W) and Laguna Cháltel (49°57´S, 71°07´W), respectively. Both lakes are of volcanic origin and have phosphorous-rich, alkaline waters, but differ in altitude (790 m asl and 110 m asl for Laguna Cháltel and Laguna Potrok Aike, respectively) and water temperature. The aim of this study is (1) to investigate conditions for the formation of ikaite and its transformation to more stable, water-free carbonate pseudomorphs after ikaite and (2) to assess the potential of ikaite and calcite pseudomorphs after ikaite as a paleoenvironmental tool in freshwater lakes. Crystallographic, morphological and isotopic characteristics of the pseudomorphs were investigated. Ikaite crystals were found (in September 2008) primarily on aquatic macrophytes and cyanobacteria colonies at Laguna Potrok Aike. Ikaite crystals transformed quickly to calcite pseudomorphs after ikaite after recovery from the cool lake water (4°C). The crystal structure of ikaite was investigated with single crystal X-ray diffraction on samples that were permanently kept cold (in the lake water). At Laguna Cháltel calcite pseudomorphs after ikaite were discovered in littoral sediment cores from 25 m water depth. The mm-sized, porous, polycrystalline calcium carbonate aggregates from the 104 cm long sediment core of Laguna Cháltel are morphologically pseudomorphs after ikaite. SEM and XRD analyses highlight that these pseudomorphs consist of several µm-small calcite crystals in a calcitic matrix. The shape of these micro-crystals changes from rounded to fibrous with increasing sediment depth. Some specimens show casts of cyanobacteria trichomes. The oxygen isotopic composition of calcite

  11. In Search of Patagonian Dust: Atmospheric Deposition of Micronutrients to the Southern Atlantic

    NASA Astrophysics Data System (ADS)

    Chance, R.; Baker, A. R.; Jickells, T. D.

    2012-12-01

    Atmospheric inputs constitute a low but variable source of micronutrients to the south Atlantic and Southern Ocean, the magnitude and spatial distribution of which remains poorly constrained. In particular, dust arising from the arid parts of southern South America has been identified as a potentially significant source of micronutrients. Ice core records indicate large fluctuations in Patagonian dust supply over glacial-interglacial timescales, but little is known about modern day fluxes. As part of the UK-GEOTRACES program, atmospheric aerosol was simultaneously sampled in the eastern and western basins of the southern Atlantic downwind of Patagonia. Specifically, a new time-series station for monitoring atmospheric aerosol in the western south Atlantic was established at Carcass Island (51o15' S, 60o35' W) in the Falkland Islands, in September 2010, and shipboard aerosol and rain samples were collected in the region between Cape Town, South Africa, and 40oS, 5oW in November and December 2010 (cruise D357). Sampling at Carcass Island continued during the austral summer of 2011-2012, and in January 2012 a second shipboard transect across the Atlantic at 40oS was completed (cruise JC068). Here we compare atmospheric concentrations and wet and dry deposition fluxes for trace metals and major nutrients in the two basins are compared, and use principal component analysis to investigate qualitative differences in the overall composition of aerosol from different sources. Concentrations of aerosol nitrogen were higher at Carcass Island than in the eastern Atlantic. During cruise D357, median concentrations of 1.7 nmol m-3 nitrate and 2.0 nmol m-3 ammonium were observed, consistent with remote south Atlantic air, while on Carcass Island corresponding concentrations were 2.3 and 6.3 nmol m-3 during the first year of sampling. Differences in the isotopic composition of aerosol nitrate from the two campaigns are discussed. "Soluble" trace metals were operationally defined

  12. Seismic Hazard of Eritrea

    NASA Astrophysics Data System (ADS)

    Hagos, L.; Arvidsson, R.

    2003-04-01

    The method of spatially smoothed seismicity developed by Frankel(1995) and later extended by Lapajne et al.(1997) , is applied to estimate the seismic hazard of Eritrea. The extended method unlike the original one involves the delineation of the whole region into subregions with statistically determined directions of seismogenic faults pertaining to the respective tectonic regions (Poljak, 2000). Fault-rupture oriented elliptical Gaussian smoothing results in spatial models of expected seismicity. Seismic catalogue was compiled from ISC, NEIC, and Turyomurgyendo(1996) and homogenized to Ms. Three seismicity models suggested by Frankel(1995) which are based on different time and magnitude intervals are used in this approach, and a fourth model suggested by Lapajne et al.(2000), which is based on the seismic energy release is also used to enhance the influence of historical events on the hazard computation. Activity rates and maximum likelihood estimates of b- values for the different models are computed using the OHAZ program. The western part of the region shows no seismic activity. b -value for models 1-3 is estimated to be 0.91. Mmax has been estimated to be 7.0. Correlation distances are obtained objectively from the location error in the seismic catalogue. The attenuation relationship by Ambraseys et al .(1996) was found suitable for the region under study. PGA values for 10% probability of exceedence in 50 years (return period of 475 years) are computed for each model and a combined seismic hazard map was produced by subjectively assigning weights to each of the models. A worst case map is also obtained showing the highest PGA values at each location from the four hazard maps. The map indicates a higher hazard along the main tectonic features of the East African and the Red sea rift systems, with its highest PGA values within Eritrea exceeding 25% of g being located north of the red sea port of Massawa. In areas around Asmara PGA values exceed 10% of g.

  13. Presence of the telescope fish Mendosoma lineatum in Patagonian waters, a new species in the ichthyological fauna from the south-west Atlantic Ocean.

    PubMed

    Bovcon, N D; Cochia, P D; Ruibal Núñez, J; Vucica, M; Figueroa, D E

    2017-10-01

    The presence of the telescope fish Mendosoma lineatum in Patagonian waters of Argentina is reported. Mendosoma lineatum is the second species of the Latridae recorded in the south-west Atlantic Ocean and its presence in Patagonia is an addition to both the ichthyological fauna of the Argentinean Sea and the south-west Atlantic Ocean. © 2017 The Fisheries Society of the British Isles.

  14. Evidence from the Rio Bayo valley on the extent of the North Patagonian Icefield during the Late Pleistocene-Holocene transition

    NASA Astrophysics Data System (ADS)

    Glasser, Neil F.; Harrison, Stephan; Ivy-Ochs, Susan; Duller, Geoffrey A. T.; Kubik, Peter W.

    2006-01-01

    This paper presents data on the extent of the North Patagonian Icefield during the Late Pleistocene-Holocene transition using cosmogenic nuclide exposure age and optically stimulated luminescence dating. We describe geomorphological and geochronological evidence for glacier extent in one of the major valleys surrounding the North Patagonian Icefield, the Rio Bayo valley. Geomorphological mapping provides evidence for the existence of two types of former ice masses in this area: (i) a large outlet glacier of the North Patagonian Icefield, which occupied the main Rio Bayo valley, and (ii) a number of small glaciers that developed in cirques on the slopes of the mountains surrounding the valley. Cosmogenic nuclide exposure-age dating of two erratic boulders on the floor of the Rio Bayo valley indicate that the outlet glacier of the icefield withdrew from the Rio Bayo valley after 10,900 ± 1000 yr (the mean of two boulders dated to 11,400 ± 900 yr and 10,500 ± 800 yr). Single-grain optically stimulated luminescence (OSL) dating of an ice-contact landform constructed against this glacier indicates that this ice mass remained in the valley until at least 9700 ± 700 yr. The agreement between the two independent dating techniques (OSL and cosmogenic nuclide exposure age dating) increases our confidence in these age estimates. A date obtained from a boulder on a cirque moraine above the main valley indicates that glaciers advanced in cirques surrounding the icefield some time around 12,500 ± 900 yr. This evidence for an expanded North Patagonian Icefield between 10,900 ± 1000 yr and 9700 ± 700 yr implies cold climatic conditions dominated at this time.

  15. Method of migrating seismic records

    DOEpatents

    Ober, Curtis C.; Romero, Louis A.; Ghiglia, Dennis C.

    2000-01-01

    The present invention provides a method of migrating seismic records that retains the information in the seismic records and allows migration with significant reductions in computing cost. The present invention comprises phase encoding seismic records and combining the encoded seismic records before migration. Phase encoding can minimize the effect of unwanted cross terms while still allowing significant reductions in the cost to migrate a number of seismic records.

  16. Seismic sequences in the Sombrero Seismic Zone

    NASA Astrophysics Data System (ADS)

    Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.

    2007-05-01

    The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, seismicity has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero Seismic Zone by the Puerto Rico Seismic Network (PRSN). In the combined seismicity catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of seismicity in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of seismic hazard, and the tsunamigenic potential of seismic events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse system of faults? A careful analysis of seismicity patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify seismic sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault systems as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same system within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of

  17. Further Studies on the Physical and Biogeochemical Causes for Large Interannual Changes in the Patagonian Shelf Spring-Summer Phytoplankton Bloom Biomass

    NASA Technical Reports Server (NTRS)

    Signorini, Sergio R.; Garcia, Virginia M.T.; Piola, Alberto R.; Evangelista, Heitor; McClain, Charles R.; Garcia, Carlos A.E.; Mata, Mauricio M.

    2009-01-01

    A very strong and persistent phytoplankton bloom was observed by ocean color satellites during September - December 2003 along the northern Patagonian shelf. The 2003 bloom had the highest extent and chlorophyll a (Chl-a) concentrations of the entire Sea-viewing Wide Field-of-view Sensor (SeaWiFS) period (1997 to present). SeaWiFS-derived Chl-a exceeded 20 mg/cu m in November at the bloom center. The bloom was most extensive in December when it spanned more than 300 km across the shelf and nearly 900 km north-south (35degS to 43degS). The northward reach and the deep penetration on the shelf of the 2003 bloom were quite anomalous when compared with other years, which showed the bloom more confined to the Patagonian shelf break (PSB). The PSB bloom is a conspicuous austral spring-summer feature detected by ocean color satellites and its timing can be explained using the Sverdrup critical depth theory. Based on high-resolution numerical simulations, in situ and remote sensing data, we provide some suggestions for the probable mechanisms responsible for that large interannual change of biomass as seen by ocean color satellites. Potential sources of macro and micro (e.g., Fe) nutrients that sustain the high phytoplankton productivity of the Patagonian shelf waters are identified, and the most likely physical processes that maintain the nutrient balance in the region are discussed.

  18. BUILDING 341 Seismic Evaluation

    SciTech Connect

    Halle, J.

    2015-06-15

    The Seismic Evaluation of Building 341 located at Lawrence Livermore National Laboratory in Livermore, California has been completed. The subject building consists of a main building, Increment 1, and two smaller additions; Increments 2 and 3.

  19. The seismic design handbook

    SciTech Connect

    Naeim, F. )

    1989-01-01

    This book contains papers on the planning, analysis, and design of earthquake resistant building structures. Theories and concepts of earthquake resistant design and their implementation in seismic design practice are presented.

  20. Climate-Seismicity Coupling

    NASA Astrophysics Data System (ADS)

    Molchanov, O.

    2009-04-01

    Topic of the slow climate changes is rather popular at present. Two important problems are usually discussing in connection with the climate variability: several years quasi-periodicity (El Nino/La Nino effect) and long-term trend in the global temperature (global warming or cooling). Concerning forcing agent on the climate changes several hypotheses have been suggested including changes in solar luminosity, variations in the Earth's orbit around the Sun, cosmic rays, volcanic eruption activity and so on but the most accepted cause is the change in atmospheric greenhouse gas concentrations due to human activity. We have tried to find a correlation between slow climate changes using variation in sstoi indices (sea surface temperature anomalies in the 3 selected areas of near-equatorial Pacific Ocean, 160E-90W) and seismic activity using USGS catalog on crustal earthquakes (EQs) in about the same areas. We calculate the values that are proportional to seismic energy release as indices of seismic activity and compare the variation of half-year sstoi and seimic indicies during period of 1973-2008. Autocorrelation of both indices smoothed by 1-year window shows the same behavior in the all selected regions with averaged 4.5 year periodicity while the cross-correlation of the indices envisages 1.5-2 years time delay of sstoi indices in relation to seismic indices. Such the mother-daughter delay is checked by comparison of deep and crustal seismic activity using technique that described in the paper [1]. Furthermore there is clear similarity in the trends of sstoi and seismic indices. We conclude that slow climate variations are probably induced by changes in natural seismicity. Energetic estimations of the climate-seismicity coupling are also discussed. [1] O.A. Mochanov and S. Uyeda, Upward migration of earthquake hypocenters in Japan, Kurile-Kamchatka and Sunda subduction zones, Physics and Chemistry, 2008, doi:10.1016/j.pce.2008.09.011.

  1. Automatic Seismic Signal Processing

    DTIC Science & Technology

    1982-02-04

    CATALOG NUMBER 4. TITLE (end Sublitle) S. TYPE O REPORT & PERIOD COVERED FINAL TECHNICAL REPORT - ROUTINE AUTOM!ATIC SEISMIC ANALYSIS TECHNICAL PACKAGE 6...Seismic Analysis Package ARPA Order Number: 4199 Name of Contractor: ENSCO, Inc. 4 - Contract Number: F086 06-80-C-0021 Effective Date of Contract: 10...developed and demonstrated. This timing detector algorithm times the start time of signals and their envelope peaks. It was designed to measure the size

  2. Seismic Consequence Abstraction

    SciTech Connect

    M. Gross

    2004-10-25

    The primary purpose of this model report is to develop abstractions for the response of engineered barrier system (EBS) components to seismic hazards at a geologic repository at Yucca Mountain, Nevada, and to define the methodology for using these abstractions in a seismic scenario class for the Total System Performance Assessment - License Application (TSPA-LA). A secondary purpose of this model report is to provide information for criticality studies related to seismic hazards. The seismic hazards addressed herein are vibratory ground motion, fault displacement, and rockfall due to ground motion. The EBS components are the drip shield, the waste package, and the fuel cladding. The requirements for development of the abstractions and the associated algorithms for the seismic scenario class are defined in ''Technical Work Plan For: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The development of these abstractions will provide a more complete representation of flow into and transport from the EBS under disruptive events. The results from this development will also address portions of integrated subissue ENG2, Mechanical Disruption of Engineered Barriers, including the acceptance criteria for this subissue defined in Section 2.2.1.3.2.3 of the ''Yucca Mountain Review Plan, Final Report'' (NRC 2003 [DIRS 163274]).

  3. Seismic offset balancing

    SciTech Connect

    Ross, C.P.; Beale, P.L.

    1994-01-01

    The ability to successfully predict lithology and fluid content from reflection seismic records using AVO techniques is contingent upon accurate pre-analysis conditioning of the seismic data. However, all too often, residual amplitude effects remain after the many offset-dependent processing steps are completed. Residual amplitude effects often represent a significant error when compared to the amplitude variation with offset (AVO) response that the authors are attempting to quantify. They propose a model-based, offset-dependent amplitude balancing method that attempts to correct for these residuals and other errors due to sub-optimal processing. Seismic offset balancing attempts to quantify the relationship between the offset response of back-ground seismic reflections and corresponding theoretical predictions for average lithologic interfaces thought to cause these background reflections. It is assumed that any deviation from the theoretical response is a result of residual processing phenomenon and/or suboptimal processing, and a simple offset-dependent scaling function is designed to correct for these differences. This function can then be applied to seismic data over both prospective and nonprospective zones within an area where the theoretical values are appropriate and the seismic characteristics are consistent. A conservative application of the above procedure results in an AVO response over both gas sands and wet sands that is much closer to theoretically expected values. A case history from the Gulf of Mexico Flexure Trend is presented as an example to demonstrate the offset balancing technique.

  4. Modelling spatial distribution of Patagonian toothfish through life-stages and sex and its implications for the fishery on the Kerguelen Plateau

    NASA Astrophysics Data System (ADS)

    Péron, Clara; Welsford, Dirk C.; Ziegler, Philippe; Lamb, Timothy D.; Gasco, Nicolas; Chazeau, Charlotte; Sinègre, Romain; Duhamel, Guy

    2016-02-01

    Size and sex specific habitat preferences are common in animal populations and can have important implications for sound spatial management of harvested species. Patagonian toothfish (Dissostichus eleginoides) is a commercially exploited fish species characterised by its longevity (>50 yo) and its extremely broad distribution in depths ranging from 10 m to 2500 m on most of the Plateaux, banks and seamounts of the Southern Ocean. As many bentho-pelagic fish species, Patagonian toothfish exhibits sexual dimorphism and ontogenetic habitat shift towards deeper waters as they grow. In this study, we modelled the spatial structure of Patagonian toothfish population (median total length and sex composition) in a data-rich area, the Kerguelen Plateau (Southern Indian Ocean), to better understand the ecological drivers of their distributional patterns and inform current and future fishery management strategies. We applied spatially-explicit statistical models to quantify and predict the effects of the complex topography of the Kerguelen Plateau in structuring the spatial distribution of Patagonian toothfish total length and sex ratio, while controlling for gear selectivity and season. Model predictions showed that juvenile toothfish live in shallow regions (shelf and banks) and move downward progressively up to 600 m while they grow. Between 600 m and 1200 m, the downward movement stops and fish settle at their preferred depths. While in this depth range, fish are ∼75 cm long and most vulnerable to fisheries. As they approach maturity large fish move downward to deep-sea habitats (from 1200 m to >2300 m) and head towards the spawning grounds on the western side of the plateau and around Skiff Bank. Importantly, the sex ratio was not evenly distributed across the Plateau; prediction maps revealed a higher proportion of females in the South whereas a strong male-bias sex ratio (70%) occurred in the North-West. Large-scale prediction maps derived from our models assisted in

  5. Major and trace element whole rock and mineral chemistry of Southern Patagonian Mantle Xenoliths

    NASA Astrophysics Data System (ADS)

    Mundl, Andrea; Ntaflos, Theodoros; Bjerg, Ernesto; Hauzenberger, Christoph

    2013-04-01

    The Pali Aike Volcanic Field (PAVF) situated in the back-arc tectonic setting of southern Patagonia is one of the two Patagonian localities where garnet and spinel peridotites are brought to the surface by alkaline basalts. The other locality is Prahuaniyeu in northern Patagonia. The xenoliths from the PAVF were collected at Salsa, El Ruido and Potrok Aike mare and are spinel- and spinel-garnet-lherzolites, followed by spinel- and spinel-garnet harzburgites. Textures are protogranular to protogranular-equigranular with some samples slightly foliated. None of the studied xenoliths contain hydrous phases such as phlogopite and/or amphibole but few contain secondary interstitial clinopyroxenes and melt pockets. Inclusions of spinel in some garnets suggest transition from spinel to garnet peridotite stability field. Frequently, Opx show exsolution lamellae of Cpx (+/- Sp) and vice versa indicating subsolidus cooling. Occasionally, Cpx show spongy rims suggesting either decompression or reaction with infiltrating melt. Whole rock Al2O3 and CaO contents range from 0.63 to 3.54 wt% and 0.24 to 2.90 wt%, respectively. The variation diagrams of CaO and Al2O3 versus MgO exhibit a linear correlation that could be interpreted as residuals after extraction of melts with different degrees of partial melting from a common mantle source. Modeled fractional melting degrees for Salsa, El Ruido and Potrok Aike Sp-peridotites are 6.5 - 12%, 4 - 17% and 5.5 - 9%, respectively. Olivine compositions vary between Fo89.51 - Fo92.04. However, one El Ruido Sp-harzburgite and one Gt-harzburgite have lower Fo-contents (Fo88.88 -Fo89.11) indicating either a cumulate nature of the xenoliths or a change in chemical composition of the rocks due to reaction with infiltrating melts. Primary Cpx are Cr-diopsides with mean compositions En47-50Fs4-5Wo48-45 in lherzolites, En49-53Fs6-5Wo44-41 in harzburgites, and En47Fs3Wo50 in the El Ruido dunite. Cpx Al2O3 and Cr2O3 contents in all rock types vary

  6. Seismic Safety Study

    SciTech Connect

    Tokarz, F J; Coats, D W

    2006-05-16

    During the past three decades, the Laboratory has been proactive in providing a seismically safe working environment for its employees and the general public. Completed seismic upgrades during this period have exceeded $30M with over 24 buildings structurally upgraded. Nevertheless, seismic questions still frequently arise regarding the safety of existing buildings. To address these issues, a comprehensive study was undertaken to develop an improved understanding of the seismic integrity of the Laboratory's entire building inventory at the Livermore Main Site and Site 300. The completed study of February 2005 extended the results from the 1998 seismic safety study per Presidential Executive Order 12941, which required each federal agency to develop an inventory of its buildings and to estimate the cost of mitigating unacceptable seismic risks. Degenkolb Engineers, who performed the first study, was recontracted to perform structural evaluations, rank order the buildings based on their level of seismic deficiencies, and to develop conceptual rehabilitation schemes for the most seriously deficient buildings. Their evaluation is based on screening procedures and guidelines as established by the Interagency Committee on Seismic Safety in Construction (ICSSC). Currently, there is an inventory of 635 buildings in the Laboratory's Facility Information Management System's (FIMS's) database, out of which 58 buildings were identified by Degenkolb Engineers that require seismic rehabilitation. The remaining 577 buildings were judged to be adequate from a seismic safety viewpoint. The basis for these evaluations followed the seismic safety performance objectives of DOE standard (DOE STD 1020) Performance Category 1 (PC1). The 58 buildings were ranked according to three risk-based priority classifications (A, B, and C) as shown in Figure 1-1 (all 58 buildings have structural deficiencies). Table 1-1 provides a brief description of their expected performance and damage state

  7. Phylogenetic diversity of true morels (Morchella), the main edible non-timber product from native Patagonian forests of Argentina.

    PubMed

    Pildain, María B; Visnovsky, Sandra B; Barroetaveña, Carolina

    2014-01-01

    Morchella species are edible fungi in high demand and therefore command high prices in world markets. Phenotypic-based identification at the species-level remains inadequate because of their complex life cycles, minor differences and plasticity of morphological characteristics between species, and the lack of agreement between scientific and common names. In Patagonia-Argentina, morels are associated with native forests of Austrocedrus chilensis (Cordilleran or Chilean cypress) and Nothofagus antarctica (ñire) and several exotic conifers that were introduced from western North America. Little is known about their taxonomy and phylogenetic relationships with other species in the genus. This work focused on the identification of collections of Morchella from Patagonia and their phylogenetic relationships with other species from the Northern Hemisphere. The comparison was made by analysis of DNA sequences obtained from four loci: the nuclear ribosomal internal transcribed spacer region (ITS) and the partial RNA polymerase I gene (RPB1) for the complete collection; and ITS, RPB1, RNA polymerase II gene (RPB2), and translation elongation factor (EF1-α) for the species-rich Elata Subclade. Analyses of individual and combined data sets revealed that Patagonian morels belong to the Elata Clade and comprised three strongly supported species-level lineages from both Patagonian native forest, and exotic trees introduced from western North America. One lineage was identified as Morchella frustrata phylogenetic species Mel-2, which is known from the USA and Canada. The second lineage, which appeared to be 'fire-adapted', was identified as Morchella septimelata phylogenetic species (Mel-7), which is also known from the USA. This species was collected from burned native forests mainly composed of A. chilensis and N. antarctica but also Pseudotsuga menziesii (Mirb.) Blanco, which is native to western North America. The phylogenetic analyses suggested that the third species from

  8. Bayesian identification of multiple seismic change points and varying seismic rates caused by induced seismicity

    NASA Astrophysics Data System (ADS)

    Montoya-Noguera, Silvana; Wang, Yu

    2017-04-01

    The Central and Eastern United States (CEUS) has experienced an abnormal increase in seismic activity, which is believed to be related to anthropogenic activities. The U.S. Geological Survey has acknowledged this situation and developed the CEUS 2016 1 year seismic hazard model using the catalog of 2015 by assuming stationary seismicity in that period. However, due to the nonstationary nature of induced seismicity, it is essential to identify change points for accurate probabilistic seismic hazard analysis (PSHA). We present a Bayesian procedure to identify the most probable change points in seismicity and define their respective seismic rates. It uses prior distributions in agreement with conventional PSHA and updates them with recent data to identify seismicity changes. It can determine the change points in a regional scale and may incorporate different types of information in an objective manner. It is first successfully tested with simulated data, and then it is used to evaluate Oklahoma's regional seismicity.

  9. Landslide seismic magnitude

    NASA Astrophysics Data System (ADS)

    Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.

    2015-11-01

    Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

  10. Seismic Microzonation for Refinement of Seismic Load Parameters

    SciTech Connect

    Savich, A. I.; Bugaevskii, A. G. E-mail: bugaevskiy@geodyn.ru

    2016-05-15

    Functional dependencies are established for the characteristics of seismic transients recorded at various points of a studied site, which are used to propose a new approach to seismic microzonation (SMZ) that enables the creation of new SMZ maps of strong seismic motion, with due regard for dynamic parameters of recorded transients during weak earthquakes.

  11. Seismic ruggedness of relays

    SciTech Connect

    Merz, K.L. )

    1991-08-01

    This report complements EPRI report NP-5223 Revision 1, February 1991, and presents additional information and analyses concerning generic seismic ruggedness of power plant relays. Existing and new test data have been used to construct Generic Equipment Ruggedness Spectra (GERS) which can be used in identifying rugged relays during seismic re-evaluation of nuclear power plants. This document is an EPRI tier 1 report. The results of relay fragility tests for both old and new relays are included in an EPRI tier 2 report with the same title. In addition to the presentation of relay GERS, the tier 2 report addresses the applicability of GERS to relays of older vintage, discusses the important identifying nomenclature for each relay type, and examines relay adjustment effects on seismic ruggedness. 9 refs., 3 figs, 1 tab.

  12. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

  13. Controllable seismic source

    DOEpatents

    Gomez, Antonio; DeRego, Paul Jeffrey; Ferrell, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

    2015-09-29

    An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

  14. Controllable seismic source

    DOEpatents

    Gomez, Antonio; DeRego, Paul Jeffrey; Ferrel, Patrick Andrew; Thom, Robert Anthony; Trujillo, Joshua J.; Herridge, Brian

    2014-08-19

    An apparatus for generating seismic waves includes a housing, a strike surface within the housing, and a hammer movably disposed within the housing. An actuator induces a striking motion in the hammer such that the hammer impacts the strike surface as part of the striking motion. The actuator is selectively adjustable to change characteristics of the striking motion and characteristics of seismic waves generated by the impact. The hammer may be modified to change the physical characteristics of the hammer, thereby changing characteristics of seismic waves generated by the hammer. The hammer may be disposed within a removable shock cavity, and the apparatus may include two hammers and two shock cavities positioned symmetrically about a center of the apparatus.

  15. Induced seismicity. Final report

    SciTech Connect

    Segall, P.

    1997-09-18

    The objective of this project has been to develop a fundamental understanding of seismicity associated with energy production. Earthquakes are known to be associated with oil, gas, and geothermal energy production. The intent is to develop physical models that predict when seismicity is likely to occur, and to determine to what extent these earthquakes can be used to infer conditions within energy reservoirs. Early work focused on earthquakes induced by oil and gas extraction. Just completed research has addressed earthquakes within geothermal fields, such as The Geysers in northern California, as well as the interactions of dilatancy, friction, and shear heating, on the generation of earthquakes. The former has involved modeling thermo- and poro-elastic effects of geothermal production and water injection. Global Positioning System (GPS) receivers are used to measure deformation associated with geothermal activity, and these measurements along with seismic data are used to test and constrain thermo-mechanical models.

  16. Unraveling Megathrust Seismicity

    NASA Astrophysics Data System (ADS)

    Funiciello, Francesca; Corbi, Fabio; van Dinther, Ylona; Heuret, Arnauld

    2013-12-01

    The majority of global seismicity originates at subduction zones, either within the converging plates or along the plate interface. In particular, events with Mw ≥ 8.0 usually occur at the subduction megathrust, which is the frictional interface between subducting and overriding plates. Consequently, seismicity at subduction megathrusts is responsible for most of the seismic energy globally released during the last century [Pacheco and Sykes, 1992]. What's more, during the last decade giant megathrust earthquakes occurred at an increased rate with respect to the last century [Ammon et al., 2010], often revealing unexpected characteristics and resulting in catastrophic effects. Determining the controlling factors of these events would have fundamental implications for earthquake and tsunami hazard assessment.

  17. Interpolation of aliased seismic traces

    SciTech Connect

    Monk, D.J.; McBeath, R.G.; Wason, C.B.

    1993-08-10

    A method is described of interpolating seismic traces comprising the steps of: (a) processing seismic data to produce input seismic traces; (b) transforming the input seismic traces from the x, y, and time domain into the x-slope, y-slope and time domain (domains) by using a two dimensional power diversity slant stack; and (c) transforming the product of step (b) back into the x, y, and time domain using an inverse slant stack.

  18. Spatial Models of Abundance and Habitat Preferences of Commerson’s and Peale’s Dolphin in Southern Patagonian Waters

    PubMed Central

    Dellabianca, Natalia A.; Pierce, Graham J.; Raya Rey, Andrea; Scioscia, Gabriela; Miller, David L.; Torres, Mónica A.; Paso Viola, M. Natalia; Schiavini, Adrián C. M.

    2016-01-01

    Commerson’s dolphins (Cephalorhynchus c. commersonii) and Peale’s dolphins (Lagenorhynchus australis) are two of the most common species of cetaceans in the coastal waters of southwest South Atlantic Ocean. Both species are listed as Data Deficient by the IUCN, mainly due to the lack of information about population sizes and trends. The goal of this study was to build spatially explicit models for the abundance of both species in relation to environmental variables using data collected during eight scientific cruises along the Patagonian shelf. Spatial models were constructed using generalized additive models. In total, 88 schools (212 individuals) of Commerson’s dolphin and 134 schools (465 individuals) of Peale’s dolphin were recorded in 8,535 km surveyed. Commerson’s dolphin was found less than 60 km from shore; whereas Peale’s dolphins occurred over a wider range of distances from the coast, the number of animals sighted usually being larger near or far from the coast. Fitted models indicate overall abundances of approximately 22,000 Commerson’s dolphins and 20,000 Peale’s dolphins in the total area studied. This work provides the first large-scale abundance estimate for Peale’s dolphin in the Atlantic Ocean and an update of population size for Commerson’s dolphin. Additionally, our results contribute to baseline data on suitable habitat conditions for both species in southern Patagonia, which is essential for the implementation of adequate conservation measures. PMID:27783627

  19. Interannual variability in reproductive traits of the Patagonian toothfish Dissostichus eleginoides around the sub-Antarctic island of South Georgia.

    PubMed

    Brigden, K E; Marshall, C T; Scott, B E; Young, E F; Brickle, P

    2017-07-01

    Commercial fisheries data, collected as part of an observer programme and covering the period 1997-2014, were utilized in order to define key reproductive traits and spawning dynamics of the Patagonian toothfish Dissostichus eleginoides at South Georgia. Multi-year spawning site fidelity of D. eleginoides was revealed through the identification of previously unknown spawning hotspots. Timing of female spawning was shown to have shifted later, leading to a shorter spawning duration. A decrease in length and mass of female and male spawning fish and a reduced number of large spawning fish was found, evidence of a change in size structure of spawning D. eleginoides. During the study period fewer later maturity stage females (including spawning stage) were observed in conjunction with increased proportions of early stage female D. eleginoides. The findings are discussed in the context of reproductive success, with consideration of the possible effects such spawning characteristics and behaviours may have on egg and larval survival. This work presents the first long-term assessment of D. eleginoides spawning dynamics at South Georgia and provides valuable knowledge for both the ecology of the species and for future fisheries management of this commercially important species. © 2017 The Fisheries Society of the British Isles.

  20. Genetic evidence and new morphometric data as essential tools to identify the Patagonian seahorse Hippocampus patagonicus (Pisces, Syngnathidae).

    PubMed

    González, R; Dinghi, P; Corio, C; Medina, A; Maggioni, M; Storero, L; Gosztonyi, A

    2014-02-01

    A genetic study to support morphometric analyses was used to improve the description and validate the Patagonian seahorse Hippocampus patagonicus (Syngnathidae) on the basis of a large number of specimens collected in the type locality (San Antonio Bay, Patagonia, Argentina). DNA sequence data (from the cytochrome b region of the mitochondrial genome) were used to differentiate this species from its relatives cited for the west Atlantic Ocean. Both phylogenetic and genetic distance analyses supported the hypothesis that H. patagonicus is a species clearly differentiated from others, in agreement with morphometric studies. Hippocampus patagonicus can be distinguished from Hippocampus erectus by the combination of the following morphometric characteristics: (1) in both sexes and all sizes of H. patagonicus, the snout length is always less than the postorbital length, whereas the snout length of H. erectus is not shorter than the postorbital length in the largest specimens; (2) in both sexes of H. patagonicus, the trunk length:total length (LTr :LT ) is lower than in H. erectus (in female H. patagonicus: 0·27-0·39, H. erectus: 0·36-0·40 and in male H. patagonicus: 0·24-0·34, H. erectus: 0·33-0·43) and (3) in both sexes, tail length:total length (LTa :LT ) in H. patagonicus is larger than in H. erectus (0·61-0·78 v. 0·54-0·64). © 2014 The Fisheries Society of the British Isles.

  1. Emissions from potential Patagonian dust sources and associated biological response in the Atlantic sector of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Castagna, A.; Evangelista, H.; Tilstra, L. G.; Kerr, R.

    2014-07-01

    The effect of Patagonian dust over primary producers in the Southern Ocean has long been disputed. Here we present new remote sensing evidence in favour of dust mediated biological response and postulate a hypothesis to explain the spatial relation observed. A new remote sensing definition of dust source areas based on the Normalized Difference Vegetation Index (NDVI) and Absorbing Aerosol Index (AAI) correlation is presented and interannual variation in AAI is evaluated within the source regions as a proxy for dust activity. Correlation of this data with annual chlorophyll concentration, phytoplankton biomass, and diatom dominance reveals a spatially coherent latitudinal band of positive correlation concentrated between the Polar Front and the Subtropical Front. This pattern is restricted to western areas in the biomass correlation and extends toward Africa for the chlorophyll and diatom correlation. This region is equivalent to the area of the Subantarctic Mode Water formation, characterized by a ratio Si : N ≪ 1 in late summer, an unfavourable condition for diatom development, especially under iron limitation. Therefore, due to Si-Fe co-limitation, the positive correlation could be the consequence of an enhanced sensibility of this area to external iron addition for diatom growth. For the Argentinean shelf-break, is not clear whether direct dust input and/or wind stress driving water masses upwelling could be responsible for the positive correlation.

  2. Analysis and dynamic modeling of a moraine failure and glacier lake outburst flood at Ventisquero Negro, Patagonian Andes (Argentina)

    NASA Astrophysics Data System (ADS)

    Worni, Raphael; Stoffel, Markus; Huggel, Christian; Volz, Christian; Casteller, Alejandro; Luckman, Brian

    2012-06-01

    SummaryAlthough moraine dams are inherently prone to failure because of their often weak structure, loose internal composition and lack of an engineered spillway, the understanding of dam breaching processes remains largely incomplete and appropriate modeling approaches are scarce. This paper analyzes a recent glacier lake outburst, caused by the failure of the terminal moraine of Ventisquero Negro (Patagonian Andes, Argentina) in May 2009. The dam breach trigger, breaching and lake emptying processes, plus the dynamics of the outburst flood were reconstructed based on field evidence and the application of a dynamic dam break model. Results indicate that the moraine failure was caused most probably by a rising lake level due to heavy precipitation, resulting in high lake outflow which led to dam erosion and finally to dam failure. The lake volume of ca. 10 × 106 m3 was released in ca. 3 h, producing high-discharge (ca. 4100 m3 s-1) debris flows and hyperconcentrated flows as the escaping water entrained large volumes of clastic material. The methodology presented in this paper provides valuable insights into complex dam breach and GLOF processes, and closes a critical gap in dynamic dam break modeling aimed at providing the lake outburst hydrograph. An accurate determination of outburst hydrographs constitutes one of the most crucial aspects for hazard assessment of unstable lakes and will gain further importance with ongoing glacier retreat and glacier lake formation.

  3. Bacterial community structure in patagonian Andean Lakes above and below timberline: from community composition to community function.

    PubMed

    Bastidas Navarro, Marcela; Balseiro, Esteban; Modenutti, Beatriz

    2014-10-01

    Lakes located above the timberline are remote systems with a number of extreme environmental conditions, becoming physically harsh ecosystems, and sensors of global change. We analyze bacterial community composition and community-level physiological profiles in mountain lakes located in an altitude gradient in North Patagonian Andes below and above the timberline, together with dissolved organic carbon (DOC) characterization and consumption. Our results indicated a decrease in 71 % of DOC and 65 % in total dissolved phosphorus (TDP) concentration as well as in bacteria abundances along the altitude range (1,380 to 1,950 m a.s.l.). Dissolved organic matter (DOM) fluorescence analysis revealed a low global variability composed by two humic-like components (allochthonous substances) and a single protein-like component (autochthonous substances). Lakes below the timberline showed the presence of all the three components, while lakes above the timberline the protein-like compound constituted the main DOC component. Furthermore, bacterial community composition similarity and ordination analysis showed that altitude and resource concentration (DOC and TDP) were the main variables determining the ordination of groups. Community-level physiological profiles showed a mismatch with bacteria community composition (BCC), indicating the absence of a relationship between genetic and functional diversity in the altitude gradient. However, carbon utilization efficiencies varied according to the presence of different compounds in DOM bulk. The obtained results suggest that the different bacterial communities in these mountain lakes seem to have similar metabolic pathways in order to be able to exploit the available DOC molecules.

  4. B341 Seismic Evaluation

    SciTech Connect

    Halle, J.

    2014-01-02

    The Seismic Evaluation of Building 341 located at Lawrence Livermore National Laboratory in Livermore, California has been completed. The subject building consists of a main building, Increment 1, and two smaller additions; Increments 2 and 3. Based on our evaluation the building does not meet a Life Safety performance level for the BSE- 1E earthquake ground shaking hazard. The BSE-1E is the recommended seismic hazard level for evaluation of existing structures and is based on a 20% probability of exceedence in 50 years.

  5. Induced Seismicity Monitoring System

    NASA Astrophysics Data System (ADS)

    Taylor, S. R.; Jarpe, S.; Harben, P.

    2014-12-01

    There are many seismological aspects associated with monitoring of permanent storage of carbon dioxide (CO2) in geologic formations. Many of these include monitoring underground gas migration through detailed tomographic studies of rock properties, integrity of the cap rock and micro seismicity with time. These types of studies require expensive deployments of surface and borehole sensors in the vicinity of the CO2 injection wells. Another problem that may exist in CO2 sequestration fields is the potential for damaging induced seismicity associated with fluid injection into the geologic reservoir. Seismic hazard monitoring in CO2 sequestration fields requires a seismic network over a spatially larger region possibly having stations in remote settings. Expensive observatory-grade seismic systems are not necessary for seismic hazard deployments or small-scale tomographic studies. Hazard monitoring requires accurate location of induced seismicity to magnitude levels only slightly less than that which can be felt at the surface (e.g. magnitude 1), and the frequencies of interest for tomographic analysis are ~1 Hz and greater. We have developed a seismo/acoustic smart sensor system that can achieve the goals necessary for induced seismicity monitoring in CO2 sequestration fields. The unit is inexpensive, lightweight, easy to deploy, can operate remotely under harsh conditions and features 9 channels of recording (currently 3C 4.5 Hz geophone, MEMS accelerometer and microphone). An on-board processor allows for satellite transmission of parameter data to a processing center. Continuous or event-detected data is kept on two removable flash SD cards of up to 64+ Gbytes each. If available, data can be transmitted via cell phone modem or picked up via site visits. Low-power consumption allows for autonomous operation using only a 10 watt solar panel and a gel-cell battery. The system has been successfully tested for long-term (> 6 months) remote operations over a wide range

  6. The Cup of Tea - Drift Sediment Analogy: The Example of a Southern Patagonian Lacustrine Basin

    NASA Astrophysics Data System (ADS)

    Gilli, A.; Anselmetti, F. S.; Ariztegui, D.; McKenzie, J. A.; Markgraf, V.

    2001-12-01

    The tools to probe both modern and ancient lake deposits were perfected to a large degree during the 1970's when Kerry Kelts coined the concept of Limnogeology. Lakes could then be used as small, well-defined laboratories for ocean processes and marine techniques adapted to limnic settings. We present here a further application of a lake as a geological laboratory by comparing the sediment transport and drift deposition in a closed lacustrine basin as an analogue to marine settings. An ongoing study in Lago Cardiel, a 20 km diameter closed-basin in southern Patagonia (Argentina), is providing a wealth of limnogeological data that will help to clarify some fundamental questions concerning timing and extend of global paleoclimatic change. A dense grid of seismic lines with both a 3.5 kHz single-channel and a stronger boomer source has provided excellent seismic penetration with up to 10 cm vertical resolution. The quasi 3D mapping of six major acoustic packages resulted in detailed contour and thickness maps for each identified sequence. Combined with piston core analyses and AMS radiocarbon dating these data allowed a continuous lake level reconstruction since and beyond the last glacial maximum. Low lake levels are identified prior to 11.2 kyr and a prominent desiccation ca. 21 kyr. The Pleistocene/Holocene transition is characterized by a large lake level rise of at least 80 m higher than modern level. The transgression and the time there after are characterized by an almost uniform sediment distribution with a weak focusing towards the center of the basin. A dramatic change in depositional pattern characterizes the Mid- and Late-Holocene. A thick dome-shaped sediment package was deposited just north of the center of the basin during the last 5'000 years, with an average sedimentation rate of 6 m per 1000 years. Striking similarities can be observed among these lacustrine sediment geometries and marine drift settings such as the Straits of Florida or the Marion

  7. The seismic analyzer: interpreting and illustrating 2D seismic data.

    PubMed

    Patel, Daniel; Giertsen, Christopher; Thurmond, John; Gjelberg, John; Gröller, M Eduard

    2008-01-01

    We present a toolbox for quickly interpreting and illustrating 2D slices of seismic volumetric reflection data. Searching for oil and gas involves creating a structural overview of seismic reflection data to identify hydrocarbon reservoirs. We improve the search of seismic structures by precalculating the horizon structures of the seismic data prior to interpretation. We improve the annotation of seismic structures by applying novel illustrative rendering algorithms tailored to seismic data, such as deformed texturing and line and texture transfer functions. The illustrative rendering results in multi-attribute and scale invariant visualizations where features are represented clearly in both highly zoomed in and zoomed out views. Thumbnail views in combination with interactive appearance control allows for a quick overview of the data before detailed interpretation takes place. These techniques help reduce the work of seismic illustrators and interpreters.

  8. Ambient seismic wave field.

    PubMed

    Nishida, Kiwamu

    2017-01-01

    The ambient seismic wave field, also known as ambient noise, is excited by oceanic gravity waves primarily. This can be categorized as seismic hum (1-20 mHz), primary microseisms (0.02-0.1 Hz), and secondary microseisms (0.1-1 Hz). Below 20 mHz, pressure fluctuations of ocean infragravity waves reach the abyssal floor. Topographic coupling between seismic waves and ocean infragravity waves at the abyssal floor can explain the observed shear traction sources. Below 5 mHz, atmospheric disturbances may also contribute to this excitation. Excitation of primary microseisms can be attributed to topographic coupling between ocean swell and seismic waves on subtle undulation of continental shelves. Excitation of secondary microseisms can be attributed to non-linear forcing by standing ocean swell at the sea surface in both pelagic and coastal regions. Recent developments in source location based on body-wave microseisms enable us to estimate forcing quantitatively. For a comprehensive understanding, we must consider the solid Earth, the ocean, and the atmosphere as a coupled system.

  9. Hanford Seismic Network

    SciTech Connect

    Reidel, S.P.; Hartshorn, D.C.

    1997-05-01

    This report describes the Hanford Seismic Network. The network consists of two instrument arrays: seismometers and strong motion accelerometers. The seismometers determine the location and magnitude of earthquakes, and the strong motion accelerometers determine ground motion. Together these instruments arrays comply with the intent of DOE Order 5480.20, Natural Phenomena Hazards Mitigation.

  10. Solar versus seismic design

    SciTech Connect

    Reitherman, R.K.

    1980-01-01

    There are several recurring seismic problems induced by passive solar design trends. The structural significance of the amount and distribution of mass, asymmetry, fluid-filled container dynamics, setbacks, atria, and buried buildings is briefly explained. It is intended to assist the solar designer in developing a better conceptual understanding of these issues from a practical viewpoint, especially during the preliminary design phase.

  11. Mobile seismic exploration

    SciTech Connect

    Dräbenstedt, A. E-mail: rembe@iei.tu-clausthal.de Seyfried, V.; Cao, X.; Rembe, C. E-mail: rembe@iei.tu-clausthal.de; Polom, U. E-mail: rembe@iei.tu-clausthal.de; Pätzold, F.; Hecker, P.; Zeller, T.

    2016-06-28

    Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.

  12. Long Period Seismic Waves

    DTIC Science & Technology

    1976-08-01

    Grant, to correlate seismic noi- se with meteorological variables . Research plan has been rather ambitious for the personnel and financial...Geoffsica, TPHM. No. 5 , p. 161. Vargas, Freddy (To he published in 1976) 1 .-DTSCRP1TNACTON DE EVENTO«; NATHDALE«; Y ARTTFTCT ALES. 2.- CALCULO DEL

  13. The seismicity of Kenya

    NASA Astrophysics Data System (ADS)

    Maguire, P. K. H.; Shah, E. R.; Pointing, A. J.; Cooke, P. A. V.; Khan, M. A.; Swain, C. J.

    The Kenya Rift Valley, part of the East African Rift System, which extends from Lake Turkana in the north to Lake Magadi in the south, is seismically active. It is surprisingly free of teleseismic events compared to the Western Rift, but experiences considerable microseismic activity releasing the elastic strain energy. This is consistent with the crust having a low tensile strength, probably due to raised geotherms beneath the rift valley arising from lithospheric aattenuation. The microseismicity suggests presently active rifting occurs as far north as 2.5°N. This is consistent with recent seismic reflection results in this region which show deep half-grabens beneath Lake Turkana. There is also a broad zone of seismicity subparalleling the rift and displaced about 150 km to the east. This may be associated with a second culmination of the lithosphere-asthenosphere boundary. In order to obtain a better understanding of the rifting process in Kenya it is suggested that a microseismic study be carried out in the Turkana region, whose near surface 3-dimensional morphology has already been examined via the seismic reflection method.

  14. Seismic Inversion Methods

    NASA Astrophysics Data System (ADS)

    Jackiewicz, Jason

    2009-09-01

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  15. Seismic Inversion Methods

    SciTech Connect

    Jackiewicz, Jason

    2009-09-16

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  16. The Viking seismic experiment

    NASA Technical Reports Server (NTRS)

    Anderson, D. L.; Miller, W. F.; Duennebier, F. K.; Lazarewicz, A. R.; Sutton, G.; Latham, G. V.; Nakamura, Y.; Toksoz, M. F.; Kovach, R. L.; Knight, T. C. D.

    1976-01-01

    A three-axis short-period seismometer is now operating on Mars in the Utopia Planitia region. The noise background correlates well with wind gusts. Although no quakes have been detected in the first 60 days of observation, it is premature to draw any conclusions about the seismicity of Mars. The instrument is expected to return data for at least 2 years.

  17. Nonstructural seismic restraint guidelines

    SciTech Connect

    Butler, D.M.; Czapinski, R.H.; Firneno, M.J.; Feemster, H.C.; Fornaciari, N.R.; Hillaire, R.G.; Kinzel, R.L.; Kirk, D.; McMahon, T.T.

    1993-08-01

    The Nonstructural Seismic Restraint Guidelines provide general information about how to secure or restrain items (such as material, equipment, furniture, and tools) in order to prevent injury and property, environmental, or programmatic damage during or following an earthquake. All SNL sites may experience earthquakes of magnitude 6.0 or higher on the Richter scale. Therefore, these guidelines are written for all SNL sites.

  18. Mobile seismic exploration

    NASA Astrophysics Data System (ADS)

    Dräbenstedt, A.; Cao, X.; Polom, U.; Pätzold, F.; Zeller, T.; Hecker, P.; Seyfried, V.; Rembe, C.

    2016-06-01

    Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.

  19. Seismic on screen

    SciTech Connect

    Coffeen, J.A.

    1990-01-01

    This book discusses methods for interpreting seismic data on computer screens and highlights various functions and the several ways they can be performed, as well as the types of hardware that can performed these functions. Vital information for the geophysicist, petroleum engineer and geologist. Also an authoritative college text.

  20. Detrital provenance constraints from the Austral (Magallanes) Basin on dynamic changes in orogenic paleogeography during Cenozoic growth and denudation of the Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Fosdick, J. C.; Leonard, J. S.; Bostelmann, J. E.; Ugalde, R.; Schwartz, T.

    2015-12-01

    The topographic development of the Patagonian Andes is influenced by crustal shortening, magmatism, asthenospheric mantle upwelling, climate, and erosion - yet knowledge of how these processes interact is hindered by an incomplete understanding of the timing and tempo of deformation and erosion. We report new detrital zircon U/Pb geochronology and sedimentology from the Cenozoic Austral (Magallanes) foreland basin in Argentina and Chile (near 51°S) that record changes in orogenic paleogeography during uplift of the Patagonian Andes. Near Cerro Castillo, Chile, zircons from deltaic and estuarine sandstones of the Cerro Dorotea Fm. indicate sedimentation ~60-61 Ma, revising the long-held Danian age assignment based on the foraminiferal content. Lower Eocene (47-46 Ma) zircons constrain the age of the overlying unit, the deltaic lower Río Turbio Fm., which shares sedimentological, paleontological, and provenance affinity with the northern Man Aike Fm. Deposition of the upper Río Turbio Fm. in Argentina occurred during the Eocene-Oligocene transition ~33-34 Ma and continued until ~26 Ma. Deposition of the Río Guillermo Fm. resumed ~23.5 Ma with the first occurrence of fluvial sedimentation that continued until the marine Patagonian transgression ~21-19 Ma at this location. Detrital zircon ages reveal upsection reduction in Late Jurassic and Paleozoic igneous sources, variable contributions of Late Cretaceous zircons, and younging of arc-derived zircons. Combined with published bedrock thermochronology and structural data, we suggest that early Miocene faulting and exhumation of the thrust-belt resulted in drainage reorganization and eastward shift in the drainage divide to the central domain, isolating the retroarc basin from the Jurassic Tobífera thrust sheets. Revised timing of sedimentation and changes in upland source areas during Paleocene-Miocene time reveals a complex relationship between basin evolution, Cenozoic climate, and phases of Andean tectonic

  1. High Voltage Seismic Generator

    NASA Astrophysics Data System (ADS)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  2. Paleomagnetism of the Patagonian orocline (Tierra del Fuego, Argentina): Evidence for a pre-early Eocene (ca. 50 Ma) oroclinal bending.

    NASA Astrophysics Data System (ADS)

    Maffione, Marco; Speranza, Fabio; Faccenna, Claudio; Rossello, Eduardo

    2010-05-01

    The southernmost segment of the Andes of southern Patagonia and Tierra del Fuego forms a ~700 km long orogenic re-entrant with an interlimb angle of ~90° known as Patagonian orocline. No reliable paleomagnetic evidence has been gathered so far to assess whether this great orogenic bend is a primary arc formed over an articulated paleomargin, or is due to bending of a previously less curved (or rectilinear) chain. Here we report on an extensive paleomagnetic and anisotropy of magnetic susceptibility (AMS) study carried out on 22 sites (298 oriented cores), predominantly sampled in Eocene marine clays from the external Magallanes belt of Tierra del Fuego. Five sites (out of six giving reliable paleomagnetic results) containing magnetite and subordinate iron sulphides yield a positive fold test at the 99% significance level, and document no significant rotation since ~50 Ma. Thus, the Patagonian orocline is either a primary bend, or an orocline formed after Cretaceous-earliest Tertiary rotations. Our data imply that the opening of the Drake Passage between South America and Antarctica (probably causing the onset of Antarctica glaciation and global climate cooling), was definitely not related to the formation of the Patagonian orocline, but was likely the sole consequence of the 32±2 Ma Scotia plate spreading. Well-defined magnetic lineations gathered at 18 sites from the Magallanes belt are sub-parallel to (mostly E-W) local fold axes, while they trend randomly at two sites from the Magallanes foreland. Our and previous AMS data consistently show that the Fuegian Andes were characterized by a N-S compression and northward displacing fold-thrust sheets during Eocene-early Miocene times (50-20 Ma), an unexpected kinematics considering coeval South America-Antarctica relative motion. Both paleomagnetic and AMS data suggest no significant influence from the E-W left-lateral Magallanes-Fagnano strike-slip fault system (MFFS), running few kilometres south of our sampling

  3. Paleomagnetic evidence for a pre-early Eocene (˜ 50 Ma) bending of the Patagonian orocline (Tierra del Fuego, Argentina): Paleogeographic and tectonic implications

    NASA Astrophysics Data System (ADS)

    Maffione, Marco; Speranza, Fabio; Faccenna, Claudio; Rossello, Eduardo

    2010-01-01

    The southernmost segment of the Andes of southern Patagonia and Tierra del Fuego forms a ˜ 700 km long orogenic re-entrant with an interlimb angle of ˜ 90° known as Patagonian orocline. No reliable paleomagnetic evidence has been gathered so far to assess whether this great orogenic bend is a primary arc formed over an articulated paleomargin, or is due to bending of a previously less curved (or rectilinear) chain. Here we report on an extensive paleomagnetic and anisotropy of magnetic susceptibility (AMS) study carried out on 22 sites (298 oriented cores), predominantly sampled in Eocene marine clays from the external Magallanes belt of Tierra del Fuego. Five sites (out of six giving reliable paleomagnetic results) containing magnetite and subordinate iron sulphides yield a positive fold test at the 99% significance level, and document no significant rotation since ˜ 50 Ma. Thus, the Patagonian orocline is either a primary bend, or an orocline formed after Cretaceous-earliest Tertiary rotations. Our data imply that the opening of the Drake Passage between South America and Antarctica (probably causing the onset of Antarctica glaciation and global climate cooling), was definitely not related to the formation of the Patagonian orocline, but was likely the sole consequence of the 32 ± 2 Ma Scotia plate spreading. Well-defined magnetic lineations gathered at 18 sites from the Magallanes belt are sub-parallel to (mostly E-W) local fold axes, while they trend randomly at two sites from the Magallanes foreland. Our and previous AMS data consistently show that the Fuegian Andes were characterized by a N-S compression and northward displacing fold-thrust sheets during Eocene-early Miocene times (50-20 Ma), an unexpected kinematics considering coeval South America-Antarctica relative motion. Both paleomagnetic and AMS data suggest no significant influence from the E-W left-lateral Magallanes-Fagnano strike-slip fault system (MFFS), running a few kilometres south of our

  4. Migratory timing, rate, routes and wintering areas of White-crested Elaenia (Elaenia albiceps chilensis), a key seed disperser for Patagonian forest regeneration

    PubMed Central

    Bravo, Susana Patricia; Cueto, Victor Rodolfo; Gorosito, Cristian Andrés

    2017-01-01

    Migratory animals often play key ecological roles within the communities they visit throughout their annual journeys. As a consequence of the links between biomes mediated by migrants, changes in one biome could affect remote areas in unpredictable ways. Migratory routes and timing of most Neotropical austral migrants, which breed at south temperate latitudes of South America and overwinter closer to or within tropical latitudes of South America, have yet to be described in detail. As a result, our understanding about how these birds provide links between South American biomes is almost non-existent. White-crested Elaenia (Elaenia albiceps chilensis) is a long-distance austral migrant that breeds in the Patagonian Forest biome and overwinters in tropical South America. Because this small flycatcher plays a key role in the regeneration of this ecosystem, our objective was to describe the annual cycle of White-crested elaenias to evaluate the degree of migratory connectivity between breeding and wintering areas and therefore to determine if there are specific biomes of northern South America linked by elaenias to Patagonian forests. Fifteen individuals were successfully tracked throughout a complete migration cycle using miniature light-level geolocators. All individuals resided and moved through the same general regions. During fall (March-April-May), elaenias were located in the Caatinga and the Atlantic Forest biomes, from Rio de Janeiro to the region near Salvador da Bahia, Brazil. During winter (June-July-Aug.), birds were located further inland, within the Cerrado biome. Birds used three different routes during fall migration. Our results indicate that some individuals use a direct route, flying between 500–600 km/day, crossing desert and grasslands, while others took a detour, flying 100–200 km/day through forested areas with refueling opportunities. All birds used the Yunga forest during spring migration, with ten out of 15 individuals showing a clear

  5. Migratory timing, rate, routes and wintering areas of White-crested Elaenia (Elaenia albiceps chilensis), a key seed disperser for Patagonian forest regeneration.

    PubMed

    Bravo, Susana Patricia; Cueto, Victor Rodolfo; Gorosito, Cristian Andrés

    2017-01-01

    Migratory animals often play key ecological roles within the communities they visit throughout their annual journeys. As a consequence of the links between biomes mediated by migrants, changes in one biome could affect remote areas in unpredictable ways. Migratory routes and timing of most Neotropical austral migrants, which breed at south temperate latitudes of South America and overwinter closer to or within tropical latitudes of South America, have yet to be described in detail. As a result, our understanding about how these birds provide links between South American biomes is almost non-existent. White-crested Elaenia (Elaenia albiceps chilensis) is a long-distance austral migrant that breeds in the Patagonian Forest biome and overwinters in tropical South America. Because this small flycatcher plays a key role in the regeneration of this ecosystem, our objective was to describe the annual cycle of White-crested elaenias to evaluate the degree of migratory connectivity between breeding and wintering areas and therefore to determine if there are specific biomes of northern South America linked by elaenias to Patagonian forests. Fifteen individuals were successfully tracked throughout a complete migration cycle using miniature light-level geolocators. All individuals resided and moved through the same general regions. During fall (March-April-May), elaenias were located in the Caatinga and the Atlantic Forest biomes, from Rio de Janeiro to the region near Salvador da Bahia, Brazil. During winter (June-July-Aug.), birds were located further inland, within the Cerrado biome. Birds used three different routes during fall migration. Our results indicate that some individuals use a direct route, flying between 500-600 km/day, crossing desert and grasslands, while others took a detour, flying 100-200 km/day through forested areas with refueling opportunities. All birds used the Yunga forest during spring migration, with ten out of 15 individuals showing a clear

  6. Magnetic fabric and microstructures of Late Paleozoic granitoids from the North Patagonian Massif: Evidence of a collision between Patagonia and Gondwana?

    NASA Astrophysics Data System (ADS)

    López de Luchi, Mónica G.; Rapalini, Augusto E.; Tomezzoli, Renata N.

    2010-10-01

    Widespread Late Paleozoic magmatism in northern Patagonia is a target to test hypotheses on the long standing question over the origin of Patagonia. In recent years, a dispute over whether it is an accreted crustal block that collided with Gondwana in Paleozoic times or an autochthonous part of South America has taken place. As part of a multidisciplinary study, an integrated microstructural and magnetic fabric study was carried out on the Late Carboniferous Yaminué Complex and the Early Permian Navarrete Plutonic Complex, both exposed in the northeastern corner of the North Patagonian Massif (40.5°S, 67.0°W). Other investigated units are the Late Carboniferous Tardugno Granodiorite, the newly defined Cabeza de Vaca Granite and the Late Permian San Martin pluton. Over 300 oriented cores from 60 sites were collected for anisotropy of magnetic susceptibility (AMS) measurements. A systematic analysis of around 100 petrographic thin sections was performed to characterize the microstructures of the different magmatic units. Microstructures in the Yaminué Complex are indicative of a transition from magmatic to solid-state deformation. Microstructures of the orthogneiss of tonalitic composition suggest an early stage in the emplacement history of this complex. The Cabeza de Vaca Granite, intrusive in Yaminué Complex, is the most evolved unit and records less intense high-temperature solid-state deformation which suggests that the stress field that controlled the emplacement of the Yaminué Complex outlasted it. According to petrologic and structural considerations, the Navarrete Plutonic Complex has been subdivided into three facies, i.e. Robaina, Guanacos and Aranda, respectively. Microstructures of the Navarrete Plutonic Complex are mostly magmatic to submagmatic, versus the solid-state fabric that characterizes the Robaina facies at the contact with the Yaminué Complex. Combined analyses of AMS and microstructural data lead us to suggest that the Yaminué Complex

  7. Seismicity-Hydrology Relationships in the Eastern Tennessee Seismic Zone

    NASA Astrophysics Data System (ADS)

    Cameron, C.; Brandmayr, E.; Vlahovic, G.

    2016-12-01

    Causes of seismicity in the eastern Tennessee seismic zone (ETSZ), the second most active intraplate seismic zone in the United States, remain unclear. Hydroseismicity proposes that intraplate seismic events can result from surface-driven pore-fluid pressure transients triggering failure in pre-stressed crust. Alternative explanations to hydrology-seismicity correlations invoke crustal loading. Seismic strain (the square root of energy) in the ETSZ was evaluated for periodicity and relationships with river discharge using 1,580 seismic events from 1977 to 2015 located within the 55,430 km2 watershed of a Tennessee River streamgage near Chattanooga. Initial findings differ from many other seismic zones, including the nearby Central Virginia Seismic Zone, where discharge correlates positively with seismicity. In the ETSZ, by contrast, interpolated strain and discharge residuals anti-correlate (r = -0.61). Cross-correlation shows discharge leading strain by 1 year (r = -0.65) and lagging strain by 8 years (r = 0.75). Geodetic data from 2008 to 2015 show crustal displacement lagging residual discharge by 1 year (r = -0.71) and residual energy by 0 days (r = 0.74). Autocorrelation shows strong annual and weak decadal periodicities in both strain and discharge. Average monthly strain and discharge residuals anti-correlate at r = -0.65, and a monthly preference was found for seismic energy release (χ2 = 43.3, p < 0.01), although not for occurrence of seismic events (χ2 = 17.5, p = 0.10), suggesting interaction with the pronounced seasonal hydrologic cycle. The shared decadal cycle between seismicity and discharge could result from the interaction of seismic and hydrologic cycles or from coincidental temporal overlap of separate physical cycles. The decrease in seismicity as discharge and subsidence increase implies crustal loading rather than pore-fluid pressure transients as a control on seismicity in the ETSZ. The ETSZ may differ from other seismic zones with respect

  8. Sensitivity of North Patagonian temperate rainforests to changes in rainfall regimes: a process-based, dynamic forest model

    NASA Astrophysics Data System (ADS)

    Gutiérrez, A. G.; Armesto, J. J.; Díaz, M. F.; Huth, A.

    2012-06-01

    Rainfall changes due to climate change and their potential impacts on forests demand the development of predictable tools coupling vegetation dynamics to hydrologic processes. Such tools need to be accurate at local scales (i.e. < 100 ha) to develop efficient forest management strategies for climate change adaptation. In this study, we developed and tested a dynamic forest model to predict hydrological balance of North Patagonian temperate rainforests on Chiloé Island, Chile (42° S). The developed model includes detailed calculations of forest water fluxes and incorporates the dynamical linkage of rainfall regimes to soil moisture, and individual tree growth. We confronted model results with detailed field measurements of water fluxes in a young secondary stand (YS). We used the model to compare forest sensitivity in the YS and an old-growth stand (OG, > 500 yr-old), i.e. changes in forest evapotranspiration, soil moisture and forest structure (biomass and basal area). We evaluated sensitivity using changes in rainfall regimes comparable to future climatic scenarios for this century in the study region. The model depicted well the hydrological balance of temperate rainforests. We found a higher evapotranspiration in OG than YS under current climatic conditions. Dryer climatic conditions predicted for this century in the study area led to changes in the hydrological balance that impacted forest structure, with stronger impacts in OG. Changes in climatic parameters decreased evapotranspiration (up to 15 % in OG compared to current values) and soil moisture to 32 % . These changes in water fluxes induced decreases in above-ground biomass in OG (up to 27 %). Our results support the use of the model for detailed analyses of climate change impacts on hydrological balance of forests. Also, it provides a tool suitable for analyses of the impacts of multiple drivers of global change on forest processes (e.g., climate change, fragmentation, forest management).

  9. Water use efficiency of twenty-five co-existing Patagonian species growing under different soil water availability.

    PubMed

    Golluscio, R A; Oesterheld, M

    2007-11-01

    The variation of plant water use efficiency (WUE) with water availability has two interacting components: a plastic response, evident when individuals of the same genotype are compared (e.g. wet versus dry years), and an interspecific response, evident when different species living in habitats with different water availability are compared. We analysed the WUE of 25 Patagonian species that belong to four life forms (grasses, shrubs, annual herbs and perennial herbs) in relation to the climatic conditions of 2 years and the mean historic water availability experienced by each species. To estimate water availability, we calculated the effective soil water potential (EWP) of each species, based on available information about soil water dynamics, phenology and root system structure. To estimate WUE, we used isotopic discrimination of leaf C (Delta(13)C) and mean annual water vapour difference between leaves and atmosphere (Deltae) measured in situ. For the plastic response, for every species and life form, WUE increased from the dry to the wet year. We hypothesize that photosynthesis was less nutrient limited in the wet than in the dry year, facilitating higher net photosynthesis rates per unit of stomatal conductance in the wet year. For the interspecific response, WUE was lower in species native to drier habitats than in species native to wetter habitats. This response was mostly accounted for by a decrease in Deltae with EWP. Annual herbs, which avoid drought in time (they have the earliest growth cycle), and shrubs, which avoid drought in space (they have the deepest roots), showed the highest EWP and WUE. We conclude that the conventional wisdom which states that the highest WUE occurs within a species during the driest years, and among species in the driest habitats, does not always hold true, and that co-existing life forms drastically differ in water availability and water economy.

  10. Short-term variations in mesozooplankton, ichthyoplankton, and nutrients associated with semi-diurnal tides in a patagonian Gulf

    NASA Astrophysics Data System (ADS)

    Castro, L. R.; Cáceres, M. A.; Silva, N.; Muñoz, M. I.; León, R.; Landaeta, M. F.; Soto-Mendoza, S.

    2011-03-01

    The relationships between the distribution of different zooplankton and ichthyoplankton stages and physical and chemical variables were studied using samples and data (CTD profiles, ADCP and current meter measurements, nutrients, mesozooplankton, ichthyoplankton) obtained from different strata during two 24-h cycles at two oceanographic stations in a Chilean Patagonian gulf during the CIMAR 10-Fiordos cruise (November, 2004). A station located at the Chacao Channel was dominated by tidal mixing and small increments in surface stratification during high tides, leading to decreased nutrient availability. This agreed with short periods of increased phytoplankton abundance during slack waters at the end of flood currents. Increases in larval density for all zooplankton and ichthyoplankton taxa corresponded to the flooding phases of the tidal cycle. When the larval density data were fit to a sinusoidal model, the regression coefficients were high, suggesting that tides are important features that modulate short-term variations in plankton abundance. All larvae did not vary synchronously with the tidal phase; rather, time lags were observed among species. The abundances of older individuals of the copepodite Rhincalanus nasutus and all zoea stages of the squat lobster Munida gregaria increased during night flood tides, whereas younger stages increased during daytime flood tides. At a station located at the Queullin Pass, which was dominated by vertical stratification patterns, the variations in peak larval density were better fitted to the semi-diurnal sea level fluctuations. Other evidence indicated internal tides below the pycnocline, which could promote larval transport in deeper layers. In the overall picture that emerges from this study, planktonic organisms from different habitats and phylogenetic origins seem to respond to the local tidal regimes. In some cases, this response might be beneficial, transporting these individuals inshore to areas that are rich in

  11. Distribution of sea-air CO2 fluxes in the Patagonian Sea: Seasonal, biological and thermal effects

    NASA Astrophysics Data System (ADS)

    Kahl, Lucía C.; Bianchi, Alejandro A.; Osiroff, Ana Paula; Pino, Diana Ruiz; Piola, Alberto R.

    2017-07-01

    Sea-air CO2 fluxes (FCO2) in the Patagonian Sea (PS) were studied using observations collected in 2000-2006. Based on the PS frontal structures and the thermal and biological contributions to FCO2 we present a regional subdivision between distinct regimes that provide new insights on the processes that control these fluxes. The coastal regime (CR) is a net source of atmospheric CO2 (4.9 × 10-3 mol m-2 d-1) while the open shelf regime (SHR) is a net CO2 sink (-6.0 × 10-3 mol m-2 d-1). The interface between these two regions closely follows the location of along-shore fronts. In addition, based on the nature of the processes that drive the FCO2, the PS is subdivided between northern (NR) and southern (SR) regions. Both, NR and SR are CO2 sinks, but the CO2 uptake is significantly higher in NR (-6.4 × 10-3 mol m-2 d-1) than in SR (-0.5 × 10-3 mol m-2 d-1). The data reveal a strong seasonality in FCO2. The mean CO2 capture throughout the PS in austral spring is -5.8 × 10-3 mol m-2 d-1, reaching values lower than -50 × 10-3 mol m-2 d-1 in NR, while in winter FCO2 is close to equilibrium in SR. The analysis of the biological and thermal effects (BE and TE, respectively) on seasonal pCO2 variability indicates that regions of CO2 emission are dominated by the TE while regions of CO2 uptake are dominated by the BE. Our results indicate that the biological pump is the dominant process determining the sea-air CO2 flux in the PS.

  12. Continental underthrusting and obduction during the Cretaceous closure of the Rocas Verdes rift basin, Cordillera Darwin, Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Klepeis, Keith; Betka, Paul; Clarke, Geoffrey; Fanning, Mark; Hervé, Francisco; Rojas, Lisandro; Mpodozis, Constantino; Thomson, Stuart

    2010-06-01

    The Patagonian Andes record a period of Cretaceous-Neogene orogenesis that began with the compressional inversion of a Late Jurassic rift called the Rocas Verdes basin. Detrital zircon ages from sediment that filled the southern part of the basin provide a maximum depositional age of ˜148 Ma, suggesting that the basin opened approximately simultaneously along its length during the Late Jurassic. Structural data and U-Pb isotopic ages on zircon from granite plutons near the Beagle Channel (55°S) show that basin inversion involved two stages of shortening separated by tens of millions of years. An initial stage created a small (˜60 km wide) thrust wedge that placed the basaltic floor of the Rocas Verdes basin on top of adjacent continental crust prior to ˜86 Ma. Structures and metamorphic mineral assemblages preserved in an exhumed middle to lower crustal shear zone in Cordillera Darwin suggest that this obduction was accompanied by south directed subduction of the basaltic crust and underthrusting of continental crust to depths of ˜35 km beneath a coeval volcanic arc. A subsequent stage of out-of-sequence thrusting, culminating in the Paleogene, shortened basement and Upper Jurassic igneous rock in the internal part of the belt by at least ˜50 km, forming a bivergent thrust wedge. This latter period coincided with the exhumation of rocks in Cordillera Darwin and expansion of the fold-thrust belt into the Magallanes foreland basin. This orogen provides an important example of how orogenesis initiated and led to continental underthrusting and obduction of basaltic crust during closure of a quasi-oceanic rift basin.

  13. Rapid Assessment of Distribution of Wildlife and Human Activities for Prioritizing Conservation Actions in a Patagonian Landscape.

    PubMed

    Rivas, Lorena F; Novaro, Andrés J; Funes, Martín C; Walker, R Susan

    2015-01-01

    Large landscapes encompassing reserves and areas with other human uses are necessary for conservation of many species. Generating information for conservation planning over such landscapes may be expensive and time-consuming, though resources for conservation are generally limited and conservation is often urgent. We developed a sign-based occupancy survey to help prioritize conservation interventions by simultaneously assessing the distribution of 3 species, the lesser rhea, guanaco, and mara, and their association with human activities in a 20,000-km2 landscape in the northern Patagonian steppe. We used a single-season occupancy model with spatial rather than temporal replication of surveys in order to reduce costs of multiple visits to sites. We used covariates related to detectability, environmental factors, and different human activities to identify the most plausible models of occupancy, and calculated importance weights of covariates from these models to evaluate relative impacts of human activities on each species. Abundance of goats had the strongest negative association with lesser rheas and guanacos, and road density with maras. With six months of fieldwork, our results provided initial hypotheses for adaptive conservation interventions for each species. Addressing high livestock densities for rheas and guanacos, poaching by urban hunters for all three species, and hunting by rural people for rheas are priorities for conservation in this landscape. Our methodology provided new insights into the responses of these species, although low detection probabilities for maras indicate that the sampling scheme should be altered for future monitoring of this species. This method may be adapted for any large landscape where a rapid, objective means for prioritizing conservation actions on multiple species is needed and data are scarce.

  14. Influence of oceanographic features on the spatial and seasonal patterns of mesozooplankton in the southern Patagonian shelf (Argentina, SW Atlantic)

    NASA Astrophysics Data System (ADS)

    Sabatini, M. E.; Reta, R.; Lutz, V. A.; Segura, V.; Daponte, C.

    2016-05-01

    Surveys conducted during spring, summer and late winter in 2005-2006 over the southern Patagonian shelf have allowed the seasonal distribution of mesozooplankton communities in relation to water masses and circulation to be investigated. In this system, most of the shelf is dominated by a distinct low salinity plume that is related to the runoff from the Magellan Strait (MSW), while the outer shelf is highly influenced by the cold and salty Subantarctic water (SAW) of the boundary Malvinas Current. Separating these two, the Subantarctic Shelf water mass (SASW) extends over the middle shelf. Correspondingly, the structure of the MSW and SAW mesozooplankton communities was found to be clearly different, while the former and the SASW assemblages were barely separable. This relatively fresh water mass is actually a variant of Subantarctic water that enters into the region from the south and the shelf-break, and hence its mesozooplankton community was not significantly different from that of the SAW water mass. Dissimilar species abundance, in turn associated with different life histories and population development, was more important than species composition in defining the assemblages. Total mesozooplankton abundance increased about 2.5-fold from the beginning of spring to late summer, and then decreased at least two orders of magnitude in winter. Across all seasons copepods represented > 70-80% of total mesozooplankton over most of the shelf. Copepod species best represented through all seasons, in terms of both relative abundance and occurrence, were Drepanopus forcipatus and Oithona helgolandica. Although seasonal differences in abundance were striking, the spatial distribution of mesozooplankton was largely similar across seasons, with relatively higher concentrations occurring mainly in Grande Bay and surroundings. The well defined spatial patterns of mesozooplankton that appear from our results in conjunction with the southward wide extension of the shelf and

  15. Seasonal trends in usnic acid concentrations of Arctic, alpine and Patagonian populations of the lichen Flavocetraria nivalis.

    PubMed

    Bjerke, Jarle W; Elvebakk, Arve; Domínguez, Erwin; Dahlback, Arne

    2005-02-01

    The widespread secondary metabolite usnic acid, a dibenzofuran derivative, is the principal acetone-soluble compound in the lichen Flavocetraria nivalis. Seasonal variation in concentrations were studied in four populations of this lichen, three from Arctic-alpine habitats in the Northern Hemisphere, and one from Patagonian heathland in the Southern Hemisphere. Usnic acid is produced in large amounts, making up between 4% and 8% of thallus dry weight. Large seasonal variation is seen, with a trend towards peak levels in late spring and early summer, and generally low levels during autumn and winter. However, at an Arctic steppe in Central West Greenland, remarkably high levels were also detected during late autumn and early winter. Comparisons with environmental data using model selection procedures show that usnic acid levels of three of the populations are positively correlated with time of season, as measured by the proximity in time to nearest summer solstice, solar radiation levels, and temperature conditions. All these three variables are intercorrelated, thus indicating the same overall trend. For the three driest sites, precipitation rates are included in the models that best explain the variation in usnic acid. However, the explanatory powers of the models are generally low, partly due to high variation between thalli growing together and sampled at the same time. This is the first attempt to compare statistically seasonal variation in usnic acid concentrations and environmental variables, and thus also the first time it is shown that the concentration in various populations of the same lichen species shows different types of correlation with seasonal climatic changes.

  16. Rapid Assessment of Distribution of Wildlife and Human Activities for Prioritizing Conservation Actions in a Patagonian Landscape

    PubMed Central

    Rivas, Lorena F.; Novaro, Andrés J.; Funes, Martín C.; Walker, R. Susan

    2015-01-01

    Large landscapes encompassing reserves and areas with other human uses are necessary for conservation of many species. Generating information for conservation planning over such landscapes may be expensive and time-consuming, though resources for conservation are generally limited and conservation is often urgent. We developed a sign-based occupancy survey to help prioritize conservation interventions by simultaneously assessing the distribution of 3 species, the lesser rhea, guanaco, and mara, and their association with human activities in a 20,000-km2 landscape in the northern Patagonian steppe. We used a single-season occupancy model with spatial rather than temporal replication of surveys in order to reduce costs of multiple visits to sites. We used covariates related to detectability, environmental factors, and different human activities to identify the most plausible models of occupancy, and calculated importance weights of covariates from these models to evaluate relative impacts of human activities on each species. Abundance of goats had the strongest negative association with lesser rheas and guanacos, and road density with maras. With six months of fieldwork, our results provided initial hypotheses for adaptive conservation interventions for each species. Addressing high livestock densities for rheas and guanacos, poaching by urban hunters for all three species, and hunting by rural people for rheas are priorities for conservation in this landscape. Our methodology provided new insights into the responses of these species, although low detection probabilities for maras indicate that the sampling scheme should be altered for future monitoring of this species. This method may be adapted for any large landscape where a rapid, objective means for prioritizing conservation actions on multiple species is needed and data are scarce. PMID:26061066

  17. Genetic Structure in a Small Pelagic Fish Coincides with a Marine Protected Area: Seascape Genetics in Patagonian Fjords.

    PubMed

    Canales-Aguirre, Cristian B; Ferrada-Fuentes, Sandra; Galleguillos, Ricardo; Hernández, Cristián E

    2016-01-01

    Marine environmental variables can play an important role in promoting population genetic differentiation in marine organisms. Although fjord ecosystems have attracted much attention due to the great oscillation of environmental variables that produce heterogeneous habitats, species inhabiting this kind of ecosystem have received less attention. In this study, we used Sprattus fuegensis, a small pelagic species that populates the inner waters of the continental shelf, channels and fjords of Chilean Patagonia and Argentina, as a model species to test whether environmental variables of fjords relate to population genetic structure. A total of 282 individuals were analyzed from Chilean Patagonia with eight microsatellite loci. Bayesian and non-Bayesian analyses were conducted to describe the genetic variability of S. fuegensis and whether it shows spatial genetic structure. Results showed two well-differentiated genetic clusters along the Chilean Patagonia distribution (i.e. inside the embayment area called TicToc, and the rest of the fjords), but no spatial isolation by distance (IBD) pattern was found with a Mantel test analysis. Temperature and nitrate were correlated to the expected heterozygosities and explained the allelic frequency variation of data in the redundancy analyses. These results suggest that the singular genetic differences found in S. fuegensis from inside TicToc Bay (East of the Corcovado Gulf) are the result of larvae retention bya combination of oceanographic mesoscale processes (i.e. the west wind drift current reaches the continental shelf exactly in this zone), and the local geographical configuration (i.e. embayment area, islands, archipelagos). We propose that these features generated an isolated area in the Patagonian fjords that promoted genetic differentiation by drift and a singular biodiversity, adding support to the existence of the largest marine protected area (MPA) of continental Chile, which is the Tic-Toc MPA.

  18. Phylogeography of the Patagonian otter Lontra provocax: adaptive divergence to marine habitat or signature of southern glacial refugia?

    PubMed Central

    2011-01-01

    Background A number of studies have described the extension of ice cover in western Patagonia during the Last Glacial Maximum, providing evidence of a complete cover of terrestrial habitat from 41°S to 56°S and two main refugia, one in south-eastern Tierra del Fuego and the other north of the Chiloé Island. However, recent evidence of high genetic diversity in Patagonian river species suggests the existence of aquatic refugia in this region. Here, we further test this hypothesis based on phylogeographic inferences from a semi-aquatic species that is a top predator of river and marine fauna, the huillín or Southern river otter (Lontra provocax). Results We examined mtDNA sequences of the control region, ND5 and Cytochrome-b (2151 bp in total) in 75 samples of L. provocax from 21 locations in river and marine habitats. Phylogenetic analysis illustrates two main divergent clades for L. provocax in continental freshwater habitat. A highly diverse clade was represented by haplotypes from the marine habitat of the Southern Fjords and Channels (SFC) region (43°38' to 53°08'S), whereas only one of these haplotypes was paraphyletic and associated with northern river haplotypes. Conclusions Our data support the hypothesis of the persistence of L. provocax in western Patagonia, south of the ice sheet limit, during last glacial maximum (41°S latitude). This limit also corresponds to a strong environmental change, which might have spurred L. provocax differentiation between the two environments. PMID:21356052

  19. Genetic Structure in a Small Pelagic Fish Coincides with a Marine Protected Area: Seascape Genetics in Patagonian Fjords

    PubMed Central

    Ferrada-Fuentes, Sandra; Galleguillos, Ricardo; Hernández, Cristián E.

    2016-01-01

    Marine environmental variables can play an important role in promoting population genetic differentiation in marine organisms. Although fjord ecosystems have attracted much attention due to the great oscillation of environmental variables that produce heterogeneous habitats, species inhabiting this kind of ecosystem have received less attention. In this study, we used Sprattus fuegensis, a small pelagic species that populates the inner waters of the continental shelf, channels and fjords of Chilean Patagonia and Argentina, as a model species to test whether environmental variables of fjords relate to population genetic structure. A total of 282 individuals were analyzed from Chilean Patagonia with eight microsatellite loci. Bayesian and non-Bayesian analyses were conducted to describe the genetic variability of S. fuegensis and whether it shows spatial genetic structure. Results showed two well-differentiated genetic clusters along the Chilean Patagonia distribution (i.e. inside the embayment area called TicToc, and the rest of the fjords), but no spatial isolation by distance (IBD) pattern was found with a Mantel test analysis. Temperature and nitrate were correlated to the expected heterozygosities and explained the allelic frequency variation of data in the redundancy analyses. These results suggest that the singular genetic differences found in S. fuegensis from inside TicToc Bay (East of the Corcovado Gulf) are the result of larvae retention bya combination of oceanographic mesoscale processes (i.e. the west wind drift current reaches the continental shelf exactly in this zone), and the local geographical configuration (i.e. embayment area, islands, archipelagos). We propose that these features generated an isolated area in the Patagonian fjords that promoted genetic differentiation by drift and a singular biodiversity, adding support to the existence of the largest marine protected area (MPA) of continental Chile, which is the Tic-Toc MPA. PMID:27505009

  20. New estimated Holocene denudation rates for non-glaciated areas in the southernmost Patagonian Andes (53°S), Chile

    NASA Astrophysics Data System (ADS)

    Breuer, Sonja; Kilian, Rolf; Baeza, Oscar; Arz, Helge

    2010-05-01

    Cenozoic denudation rates are sparsely known for the southernmost Patagonian Andes. One of the scientific approaches is to calculate long-term denudation rates based on fission track analyses. Though, these average rates comprise a long period with distinct climate conditions and very different extend of glaciation. These integrated denudation rates include extensive surface areas with different morphological, glacial and vegetational properties. In contrast, our approach is restricted to relative short Holocene periods and small catchment areas, for which the denudation and its controlling surface characteristics could be defined more precisely. Thus a more precise evaluation of the influencing parameters like climate, morphology and vegetation cover was possible. We concentrated on three restricted and nearly closed areas of denudation and accumulation. In those catchments we determined the sediment masses of lakes, based on sediment drilling, echosounding and computer based interpolation of the siliciclastic sediment masses. These masses were transferred to the denudation areas which have been characterised and measured by remote sensing. The westernmost Tamar Lake is located on the Tamar Island in the western part of the Magellan Strait, where the annual precipitation is about 4,000 mm. The catchment area has a dense vegetation cover. The lake surrounding slopes reach an elevation of 400 m a.s.l and they are up to 60° steep. The calculated denudation rate for this catchment is about 2.56 mm/ka, which represents a minimum value, because the postglacial weathering horizon is only partly removed into the lake. The highest elevated lake Muy Profundo (500 m a.s.l.) possesses a denudation area with a nearly vegetation-free zone up to 750 m a.s.l. within the Patagonian Batholith. The catchment area of this lake is characterised by a roche moutonnée landform with steep slopes and active fracture zones. The precipitation varies between 5,000 and 8,000 mm/a. The

  1. Seismic capacity of switchgear

    SciTech Connect

    Bandyopadhyay, K.; Hofmayer, C.; Kassir, M.; Pepper, S.

    1989-01-01

    As part of a component fragility program sponsored by the USNRC, BNL has collected existing information on the seismic capacity of switchgear assemblies from major manufacturers. Existing seismic test data for both low and medium voltage switchgear assemblies have been evaluated and the generic results are presented in this paper. The failure modes are identified and the corresponding generic lower bound capacity levels are established. The test response spectra have been used as a measure of the test vibration input. The results indicate that relays chatter at a very low input level at the base of the switchgear cabinet. This change of state of devices including relays have been observed. Breaker tripping occurs at a higher vibration level. Although the structural failure of internal elements have been noticed, the overall switchgear cabinet structure withstands a high vibration level. 5 refs., 2 figs., 2 tabs.

  2. Seismic detection of tornadoes

    USGS Publications Warehouse

    Tatom, F. B.

    1993-01-01

    Tornadoes represent the most violent of all forms of atmospheric storms, each year resulting in hundreds of millions of dollars in property damage and approximately one hundred fatalities. In recent years, considerable success has been achieved in detecting tornadic storms by means of Doppler radar. However, radar systems cannot determine when a tornado is actually in contact with the ground, expect possibly at extremely close range. At the present time, human observation is the only truly reliable way of knowing that a tornado is actually on the ground. However, considerable evidence exists indicating that a tornado in contact with the ground produces a significant seismic signal. If such signals are generated, the seismic detection and warning of an imminent tornado can become a distinct possibility. 

  3. Lunar seismic data analysis

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.; Latham, G. V.; Dorman, H. J.

    1982-01-01

    The scientific data transmitted continuously from all ALSEP (Apollo Lunar Surface Experiment Package) stations on the Moon and recorded on instrumentation tapes at receiving stations distributed around the Earth were processed. The processing produced sets of computer-compatible digital tapes, from which various other data sets convenient for analysis were generated. The seismograms were read, various types of seismic events were classified; the detected events were cataloged.

  4. Albuquerque Basin seismic network

    USGS Publications Warehouse

    Jaksha, Lawrence H.; Locke, Jerry; Thompson, J.B.; Garcia, Alvin

    1977-01-01

    The U.S. Geological Survey has recently completed the installation of a seismic network around the Albuquerque Basin in New Mexico. The network consists of two seismometer arrays, a thirteen-station array monitoring an area of approximately 28,000 km 2 and an eight-element array monitoring the area immediately adjacent to the Albuquerque Seismological Laboratory. This report describes the instrumentation deployed in the network.

  5. Establishing seismic design criteria to achieve an acceptable seismic margin

    SciTech Connect

    Kennedy, R.P.

    1997-01-01

    In order to develop a risk based seismic design criteria the following four issues must be addressed: (1) What target annual probability of seismic induced unacceptable performance is acceptable? (2). What minimum seismic margin is acceptable? (3) Given the decisions made under Issues 1 and 2, at what annual frequency of exceedance should the Safe Shutdown Earthquake ground motion be defined? (4) What seismic design criteria should be established to reasonably achieve the seismic margin defined under Issue 2? The first issue is purely a policy decision and is not addressed in this paper. Each of the other three issues are addressed. Issues 2 and 3 are integrally tied together so that a very large number of possible combinations of responses to these two issues can be used to achieve the target goal defined under Issue 1. Section 2 lays out a combined approach to these two issues and presents three potentially attractive combined resolutions of these two issues which reasonably achieves the target goal. The remainder of the paper discusses an approach which can be used to develop seismic design criteria aimed at achieving the desired seismic margin defined in resolution of Issue 2. Suggestions for revising existing seismic design criteria to more consistently achieve the desired seismic margin are presented.

  6. ELASTIC-WAVEFIELD SEISMIC STRATIGRAPHY: A NEW SEISMIC IMAGING TECHNOLOGY

    SciTech Connect

    Bob A. Hardage

    2004-05-06

    The focus of elastic-wavefield seismic stratigraphy research shifted from onshore prospects to marine environments during this report period. Four-component ocean-bottom-cable (4-C OBC) seismic data acquired in water depths of 2400 to 2500 feet across Green Canyon Block 237 in the Gulf of Mexico were processed and analyzed. The P-P and P-SV images of strata immediately below the seafloor exhibit amazing differences in P-P and P-SV seismic facies. These data may be one of the classic examples of the basic concepts of elastic-wavefield seismic stratigraphy.

  7. Seismic basement in Poland

    NASA Astrophysics Data System (ADS)

    Grad, Marek; Polkowski, Marcin

    2016-06-01

    The area of contact between Precambrian and Phanerozoic Europe in Poland has complicated structure of sedimentary cover and basement. The thinnest sedimentary cover in the Mazury-Belarus anteclize is only 0.3-1 km thick, increases to 7-8 km along the East European Craton margin, and 9-12 km in the Trans-European Suture Zone (TESZ). The Variscan domain is characterized by a 1- to 2-km-thick sedimentary cover, while the Carpathians are characterized by very thick sediments, up to c. 20 km. The map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles. These maps do not provide data about the basement depth in the central part of the TESZ and in the Carpathians. Therefore, the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high-resistivity (low-conductivity) layer from magnetotelluric soundings, identified as a basement. All of these data provide knowledge about the basement depth and of P-wave seismic velocities of the crystalline and consolidated type of basement for the whole area of Poland. Finally, the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area.

  8. Seismicity in South Carolina

    USGS Publications Warehouse

    Shedlock, K.M.

    1988-01-01

    The largest historical earthquake in South Carolina, and in the southeastern US, occurred in the Coastal Plain province, probably northwest of Charleston, in 1886. Locations for aftershocks associated with this earthquake, estimated using intensities based on newspaper accounts, defined a northwest trending zone about 250 km long that was at least 100 km wide in the Coastal Plain but widened to a northeast trending zone in the Piedmont. The subsequent historical and instrumentally recorded seismicity in South Carolina images the 1886 aftershock zone. Instrumentally recorded seismicity in the Coastal Plain province occurs in 3 seismic zones or clusters: Middleton Place-Summervile (MPSSZ), Adams Run (ARC), and Bowman (BSZ). Approximately 68% of the Coastal Plain earthquakes occur in the MPSSZ, a north trending zone about 22 km long and 12 km wide, lying about 20 km northwest of Charleston. The hypocenters of MPSSZ earthquakes range in depth from near the surface to almost 12 km. Thrust, strike-slip, and some normal faulting are indicated by the fault plane solutions for Coastal Plain earthquakes. The maximum horizontal compressive stress, inferred from the P-axes of the fault plane solutions, is oriented NE-SW in the shallow crust (<9 km deep) but appears to be diffusely E-W between 9 to 12 km deep. -from Author

  9. Tectonic development of the North Patagonian Andes and their related Miocene foreland basin (41°30‧-43°S)

    NASA Astrophysics Data System (ADS)

    Orts, DaríO. Leandro; Folguera, AndréS.; Encinas, Alfonso; Ramos, Miguel; Tobal, Jonathan; Ramos, VíCtor A.

    2012-06-01

    The Northern Patagonian Andes have been constructed through multiple mechanisms that range from tectonic inversion of extensional structures of Early to Middle Jurassic age in the Main Andes to Oligocene in the Precordilleran region. These have acted during two distinctive orogenic stages, first in late Early Cretaceous and later in Miocene times Late Oligocene extension separates these two contractional periods and is recorded by half-grabens developed in the retroarc region. The last contractional stage coexists with an eastward foreland expansion of the late Miocene arc whose roots are presently exposed as minor granitic stocks and volcanic piles subordinately in the Main Andes, east of the present arc. As a consequence of this orogenic stage a foreland basin has developed, having progressed from 18 Ma in the main North Patagonian Andes, where the mountain front was flooded by a marine transgression corresponding to the base of the Ñirihuau Formation, to 11 Ma in the foreland area. Cannibalization of this foreland basin occurred initially in the hinterland and then progressed to the foreland zone. Blind structures formed a broken foreland at the frontal zone inferred from growth strata geometries. During Pliocene to Quaternary times most of the contractional deformation was dissipated in the orogenic wedge at the time when the arc front retracted to its present position.

  10. Ectomycorrhizal fungi associated with ponderosa pine and Douglas-fir: a comparison of species richness in native western North American forests and Patagonian plantations from Argentina.

    PubMed

    Barroetaveña, C; Cázares, E; Rajchenberg, M

    2007-07-01

    The putative ectomycorrhizal fungal species registered from sporocarps associated with ponderosa pine and Douglas-fir forests in their natural range distribution (i.e., western Canada, USA, and Mexico) and from plantations in south Argentina and other parts of the world are listed. One hundred and fifty seven taxa are reported for native ponderosa pine forests and 514 taxa for native Douglas-fir forests based on available literature and databases. A small group of genera comprises a high proportion of the species richness for native Douglas-fir (i.e., Cortinarius, Inocybe, and Russula), whereas in native ponderosa pine, the species richness is more evenly distributed among several genera. The comparison between ectomycorrhizal species richness associated with both trees in native forests and in Patagonia (Argentina) shows far fewer species in the latter, with 18 taxa for the ponderosa pine and 15 for the Douglas-fir. Epigeous species richness is clearly dominant in native Douglas-fir, whereas a more balanced relation epigeous/hypogeous richness is observed for native ponderosa pine; a similar trend was observed for Patagonian plantations. Most fungi in Patagonian Douglas-fir plantations have not been recorded in plantations elsewhere, except Suillus lakei and Thelephora terrestris, and only 56% of the fungal taxa recorded in Douglas-fir plantations around the world are known from native forests, the other taxa being new associations for this host, suggesting that new tree + ectomycorrhizal fungal taxa associations are favored in artificial situations as plantations.

  11. Use of AFLP and RAPD molecular genetic markers and cytogenetic analysis to explore relationships among taxa of the Patagonian Bromus setifolius complex

    PubMed Central

    2009-01-01

    Bromus setifolius var. pictus (Hook) Skottsb., B. setifolius var. setifolius Presl. and B.setifolius var. brevifolius Ness are three native Patagonian taxa in the section Pnigma Dumort of the genus Bromus L. AFLP and RAPD analysis, in conjunction with genetic distance measurements and statistical techniques, revealed variation within this group and indicated that B. setifolius var. brevifolius was closely related to B. setifolius var. pictus, with both taxa being more distantly related to B. setifolius var. setifolius. Cytogenetic analysis confirmed the chromosomal number of B. setifolius var. pictus (2n = 70) and B. setifolius var. setifolius (2n = 28) and showed for the first time that B. setifolius var. brevifolius had 2n = 70. The combination of molecular genetic and cytogenetic evidence supported a species status for two of the three taxa and suggested hypotheses for the evolutionary origin of these complex taxa. Species status was also indicated for B. setifolius var. setifolius. Based on these findings, we suggest that B. setifolius var. pictus be referred to as B. pictus Hook var. pictus, and B. setifolius var brevifolius as B. pictus Hook var brevifolius. The correlation between AFLP diversity and variation in ecological parameters suggested that this marker system could be used to assess breeding progress and to monitor the domestication of Patagonian Bromus species for agronomic use. PMID:21637686

  12. Seismic upgrades of healthcare facilities.

    PubMed

    Yusuf, A

    1997-06-01

    Before 1989 seismic upgrading of hospital structures was not a primary consideration among hospital owners. However, after extensive earthquake damage to hospital buildings at Loma Prieta in Northern California in 1989 and then at Northridge in Southern California in 1994, hospital owners, legislators, and design teams become concerned about the need for seismic upgrading of existing facilities. Because the damage hospital structures sustained in the earthquakes was so severe and far-reaching, California has enacted laws that mandate seismic upgrading for existing facilities. Now hospital owners will have to upgrade buildings that do not conform to statewide seismic adequacy laws. By 2030, California expects all of its hospital structures to be sufficiently seismic-resistant. Slowly, regions in the Midwest and on the East Coast are following their example. This article outlines reasons and ways for seismic upgrading of existing facilities.

  13. Seismic Imager Space Telescope

    NASA Technical Reports Server (NTRS)

    Sidick, Erkin; Coste, Keith; Cunningham, J.; Sievers,Michael W.; Agnes, Gregory S.; Polanco, Otto R.; Green, Joseph J.; Cameron, Bruce A.; Redding, David C.; Avouac, Jean Philippe; hide

    2012-01-01

    A concept has been developed for a geostationary seismic imager (GSI), a space telescope in geostationary orbit above the Pacific coast of the Americas that would provide movies of many large earthquakes occurring in the area from Southern Chile to Southern Alaska. The GSI movies would cover a field of view as long as 300 km, at a spatial resolution of 3 to 15 m and a temporal resolution of 1 to 2 Hz, which is sufficient for accurate measurement of surface displacements and photometric changes induced by seismic waves. Computer processing of the movie images would exploit these dynamic changes to accurately measure the rapidly evolving surface waves and surface ruptures as they happen. These measurements would provide key information to advance the understanding of the mechanisms governing earthquake ruptures, and the propagation and arrest of damaging seismic waves. GSI operational strategy is to react to earthquakes detected by ground seismometers, slewing the satellite to point at the epicenters of earthquakes above a certain magnitude. Some of these earthquakes will be foreshocks of larger earthquakes; these will be observed, as the spacecraft would have been pointed in the right direction. This strategy was tested against the historical record for the Pacific coast of the Americas, from 1973 until the present. Based on the seismicity recorded during this time period, a GSI mission with a lifetime of 10 years could have been in position to observe at least 13 (22 on average) earthquakes of magnitude larger than 6, and at least one (2 on average) earthquake of magnitude larger than 7. A GSI would provide data unprecedented in its extent and temporal and spatial resolution. It would provide this data for some of the world's most seismically active regions, and do so better and at a lower cost than could be done with ground-based instrumentation. A GSI would revolutionize the understanding of earthquake dynamics, perhaps leading ultimately to effective warning

  14. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2003-04-01

    In this report we will show results of seismic and well log derived attenuation attributes from a deep water Gulf of Mexico data set. This data was contributed by Burlington Resources and Seitel Inc. The data consists of ten square kilometers of 3D seismic data and three well penetrations. We have computed anomalous seismic absorption attributes on the seismic data and have computed Q from the well log curves. The results show a good correlation between the anomalous absorption (attenuation) attributes and the presence of gas as indicated by well logs.

  15. Modelling of NW Himalayan Seismicity

    NASA Astrophysics Data System (ADS)

    Bansal, A. R.; Dimri, V. P.

    2014-12-01

    The northwest Himalaya is seismicity active region due to the collision of Indian and Eurasian plates and experienced many large earthquakes in past. A systematic analysis of seismicity is useful for seismic hazard estimation of the region. We analyzed the seismicity of northwestern Himalaya since 1980. The magnitude of completeness of the catalogue is carried out using different methods and found as 3.0. A large difference in magnitude of completeness is found using different methods and a reliable value is obtained after testing the distribution of magnitudes with time. The region is prone to large earthquake and many studied have shown that seismic activation or quiescence takes place before large earthquakes. We studied such behavior of seismicity based on Epidemic Type Aftershock Sequence (ETAS) model and found that a stationary ETAS model is more suitable for modelling the seismicity of this region. The earthquake catalogue is de-clustered using stochasting approach to study behavior of background and triggered seismicity. The triggered seismicity is found to have shallower depths as compared to the background events.

  16. Seismicity around Brazilian dam reservoirs

    SciTech Connect

    Coelho, P.E.F.P. )

    1987-01-01

    More than 30 cases of seismicity associated with dam reservoir sites are known throughout the world. Despite the lack of data in some areas, where seismicity occurred after reservoir impounding, there have been distinct seismic patterns observed in seismic areas after dam projects implantation. This has demonstrated that reservoir loading can trigger earthquakes. A mechanism of earthquake generation by reservoir impounding is proposed here with particular application to the Brazilian cases and to areas subject to low confining stress conditions in stable regions. Six artificial lakes are described and the associated earthquake sources are discussed in terms of natural or induced seismicity. Earthquake monitoring in Brazil up to 1967, when Brasilia's seismological station started operation, was mainly based in personal communications to the media. Therefore, there is a general lack of seismic records in relatively uninhabited areas, making it difficult to establish a seismic risk classification for the territory and to distinguish natural from induced seismicity. Despite this, cases reported here have shown an alteration of the original seismic stability in dam sites after reservoir loading, as observed by the inhabitants or records from Brasilia's seismological station. All cases appear to be related to an increase in pore pressure in permeable rocks or fracture zones which are confined between impermeable rock slabs or more competent rock. It is apparent that some cases show some participation of high residual stress conditions in the area.

  17. Neural networks in seismic discrimination

    SciTech Connect

    Dowla, F.U.

    1995-01-01

    Neural networks are powerful and elegant computational tools that can be used in the analysis of geophysical signals. At Lawrence Livermore National Laboratory, we have developed neural networks to solve problems in seismic discrimination, event classification, and seismic and hydrodynamic yield estimation. Other researchers have used neural networks for seismic phase identification. We are currently developing neural networks to estimate depths of seismic events using regional seismograms. In this paper different types of network architecture and representation techniques are discussed. We address the important problem of designing neural networks with good generalization capabilities. Examples of neural networks for treaty verification applications are also described.

  18. Seismic hazard estimation of northern Iran using smoothed seismicity

    NASA Astrophysics Data System (ADS)

    Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.

    2017-03-01

    This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

  19. Seismic hazard estimation of northern Iran using smoothed seismicity

    NASA Astrophysics Data System (ADS)

    Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.

    2017-07-01

    This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

  20. Validating induced seismicity forecast models—Induced Seismicity Test Bench

    NASA Astrophysics Data System (ADS)

    Király-Proag, Eszter; Zechar, J. Douglas; Gischig, Valentin; Wiemer, Stefan; Karvounis, Dimitrios; Doetsch, Joseph

    2016-08-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. In this study, we propose an Induced Seismicity Test Bench to test and rank such models; this test bench can be used for model development, model selection, and ensemble model building. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models: Shapiro and Smoothed Seismicity (SaSS) and Hydraulics and Seismics (HySei). These models incorporate a different mix of physics-based elements and stochastic representation of the induced sequences. Our results show that neither model is fully superior to the other. Generally, HySei forecasts the seismicity rate better after shut-in but is only mediocre at forecasting the spatial distribution. On the other hand, SaSS forecasts the spatial distribution better and gives better seismicity rate estimates before shut-in. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in.

  1. Seismic monitoring of Poland - temporary seismic project - first results

    NASA Astrophysics Data System (ADS)

    Trojanowski, J.; Plesiewicz, B.; Wiszniowski, J.; Suchcicki, J.; Tokarz, A.

    2012-04-01

    The aim of the project is to develop national database of seismic activity for seismic hazard assessment. Poland is known as a region of very low seismicity, however some earthquakes occur from time to time. The historical catalogue consists of less than one hundred earthquakes in the time span of almost one thousand years. Due to such a low occurrence rate, the study has been focussing on events at magnitudes lower than 2 which are more likely to occur during a few-year-long project. There are 24 mobile seismic stations involved in the project which are deployed in temporary locations close to humans neighbourhood. It causes a high level of noise and disturbances in recorded seismic signal. Moreover, the majority of Polish territory is covered by a thick sediments. It causes the problem of a reliable detection method for small seismic events in noisy data. The majority of algorithms is based on the concept of STA/LTA ratio and is designed for strong teleseismic events registered on many stations. Unfortunately they fail on the problem of weak events in the signal with noise and disturbances. It has been decided to apply Real Time Recurrent Neural Network (RTRN) to detect small natural seismic events from Poland. This method is able to assess relations of seismic signal in frequency domains as well as in time of seismic phases. The RTRN was taught by wide range of seismic signals - regional, teleseismic as well as blasts. The method is routinely used to analyse data from the project. In the firs two years of the project the seismic network was set in southern Poland, where relatively large seismicity in known. Since the mid-2010 the stations have been working in several regions of central and northern Poland where some minor historical earthquakes occurred. Over one hundred seismic events in magnitude range from 0.5 to 2.3 confirms the activity of Podhale region (Tatra Mountains, Carpathians), where an earthquake of magnitude 4.3 occurred in 2004. Initially three

  2. Automating Shallow Seismic Imaging

    SciTech Connect

    Steeples, Don W.

    2004-12-09

    This seven-year, shallow-seismic reflection research project had the aim of improving geophysical imaging of possible contaminant flow paths. Thousands of chemically contaminated sites exist in the United States, including at least 3,700 at Department of Energy (DOE) facilities. Imaging technologies such as shallow seismic reflection (SSR) and ground-penetrating radar (GPR) sometimes are capable of identifying geologic conditions that might indicate preferential contaminant-flow paths. Historically, SSR has been used very little at depths shallower than 30 m, and even more rarely at depths of 10 m or less. Conversely, GPR is rarely useful at depths greater than 10 m, especially in areas where clay or other electrically conductive materials are present near the surface. Efforts to image the cone of depression around a pumping well using seismic methods were only partially successful (for complete references of all research results, see the full Final Technical Report, DOE/ER/14826-F), but peripheral results included development of SSR methods for depths shallower than one meter, a depth range that had not been achieved before. Imaging at such shallow depths, however, requires geophone intervals of the order of 10 cm or less, which makes such surveys very expensive in terms of human time and effort. We also showed that SSR and GPR could be used in a complementary fashion to image the same volume of earth at very shallow depths. The primary research focus of the second three-year period of funding was to develop and demonstrate an automated method of conducting two-dimensional (2D) shallow-seismic surveys with the goal of saving time, effort, and money. Tests involving the second generation of the hydraulic geophone-planting device dubbed the ''Autojuggie'' showed that large numbers of geophones can be placed quickly and automatically and can acquire high-quality data, although not under rough topographic conditions. In some easy-access environments, this device could

  3. Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology

    SciTech Connect

    Bob A. Hardage; Milo M. Backus; Michael V. DeAngelo; Sergey Fomel; Khaled Fouad; Robert J. Graebner; Paul E. Murray; Randy Remington; Diana Sava

    2006-07-31

    The purpose of our research has been to develop and demonstrate a seismic technology that will provide the oil and gas industry a better methodology for understanding reservoir and seal architectures and for improving interpretations of hydrocarbon systems. Our research goal was to expand the valuable science of seismic stratigraphy beyond the constraints of compressional (P-P) seismic data by using all modes (P-P, P-SV, SH-SH, SV-SV, SV-P) of a seismic elastic wavefield to define depositional sequences and facies. Our objective was to demonstrate that one or more modes of an elastic wavefield may image stratal surfaces across some stratigraphic intervals that are not seen by companion wave modes and thus provide different, but equally valid, information regarding depositional sequences and sedimentary facies within that interval. We use the term elastic wavefield stratigraphy to describe the methodology we use to integrate seismic sequences and seismic facies from all modes of an elastic wavefield into a seismic interpretation. We interpreted both onshore and marine multicomponent seismic surveys to select the data examples that we use to document the principles of elastic wavefield stratigraphy. We have also used examples from published papers that illustrate some concepts better than did the multicomponent seismic data that were available for our analysis. In each interpretation study, we used rock physics modeling to explain how and why certain geological conditions caused differences in P and S reflectivities that resulted in P-wave seismic sequences and facies being different from depth-equivalent S-wave sequences and facies across the targets we studied.

  4. Seismic risk perception test

    NASA Astrophysics Data System (ADS)

    Crescimbene, Massimo; La Longa, Federica; Camassi, Romano; Pino, Nicola Alessandro

    2013-04-01

    The perception of risks involves the process of collecting, selecting and interpreting signals about uncertain impacts of events, activities or technologies. In the natural sciences the term risk seems to be clearly defined, it means the probability distribution of adverse effects, but the everyday use of risk has different connotations (Renn, 2008). The two terms, hazards and risks, are often used interchangeably by the public. Knowledge, experience, values, attitudes and feelings all influence the thinking and judgement of people about the seriousness and acceptability of risks. Within the social sciences however the terminology of 'risk perception' has become the conventional standard (Slovic, 1987). The mental models and other psychological mechanisms which people use to judge risks (such as cognitive heuristics and risk images) are internalized through social and cultural learning and constantly moderated (reinforced, modified, amplified or attenuated) by media reports, peer influences and other communication processes (Morgan et al., 2001). Yet, a theory of risk perception that offers an integrative, as well as empirically valid, approach to understanding and explaining risk perception is still missing". To understand the perception of risk is necessary to consider several areas: social, psychological, cultural, and their interactions. Among the various research in an international context on the perception of natural hazards, it seemed promising the approach with the method of semantic differential (Osgood, C.E., Suci, G., & Tannenbaum, P. 1957, The measurement of meaning. Urbana, IL: University of Illinois Press). The test on seismic risk perception has been constructed by the method of the semantic differential. To compare opposite adjectives or terms has been used a Likert's scale to seven point. The test consists of an informative part and six sections respectively dedicated to: hazard; vulnerability (home and workplace); exposed value (with reference to

  5. Geographical differentiation in floral traits across the distribution range of the Patagonian oil-secreting Calceolaria polyrhiza: do pollinators matter?

    PubMed Central

    Cosacov, Andrea; Cocucci, Andrea A.; Sérsic, Alicia N.

    2014-01-01

    Background and Aims The underlying evolutionary processes of pollinator-driven floral diversification are still poorly understood. According to the Grant–Stebbins model speciation begins with adaptive local differentiation in the response to spatial heterogeneity in pollinators. Although this crucial process links the micro- and macroevolution of floral adaptation, it has received little attention. In this study geographical phenotypic variation was investigated in Patagonian Calceolaria polyrhiza and its pollinators, two oil-collecting bee species that differ in body size and geographical distribution. Methods Patterns of phenotypic variation were examined together with their relationships with pollinators and abiotic factors. Six floral and seven vegetative traits were measured in 45 populations distributed across the entire species range. Climatic and edaphic parameters were determined for 25 selected sites, 2–16 bees per site of the most frequent pollinator species were captured, and a critical flower–bee mechanical fitting trait involved in effective pollination was measured. Geographical patterns of phenotypic and environmental variation were examined using uni- and multivariate analyses. Decoupled geographical variation between corolla area and floral traits related to the mechanical fit of pollinators was explored using a Mantel test. Key Results The body length of pollinators and the floral traits related to mechanical fit were strongly correlated with each other. Geographical variation of the mechanical-fit-related traits was decoupled from variation in corolla size; the latter had a geographical pattern consistent with that of the vegetative traits and was mainly affected by climatic gradients. Conclusions The results are consistent with pollinators playing a key role in shaping floral phenotype at a geographical scale and promoting the differentiation of two floral ecotypes. The relationship between the critical floral-fit-related trait and bee

  6. Three-dimensional temperature fields of the North Patagonian Sea recorded by Magellanic penguins as biological sampling platforms

    NASA Astrophysics Data System (ADS)

    Sala, Juan E.; Pisoni, Juan P.; Quintana, Flavio

    2017-04-01

    Temperature is a primary determinant of biogeographic patterns and ecosystem processes. Standard techniques to study the ocean temperature in situ are, however, particularly limited by their time and spatial coverage, problems which might be partially mitigated by using marine top predators as biological platforms for oceanographic sampling. We used small archival tags deployed on 33 Magellanic penguins (Spheniscus magellanicus), and obtained 21,070 geo-localized profiles of water temperature, during late spring of 2008, 2011, 2012 and 2013; in a region of the North Patagonian Sea with limited oceanographic records in situ. We compared our in situ data of sea surface temperature (SST) with those available from satellite remote sensing; to describe the three-dimensional temperature fields around the area of influence of two important tidal frontal systems; and to study the inter-annual variation in the three-dimensional temperature fields. There was a strong positive relationship between satellite- and animal-derived SST data although there was an overestimation by remote-sensing by a maximum difference of +2 °C. Little inter-annual variability in the 3-dimensional temperature fields was found, with the exception of 2012 (and to a lesser extent in 2013) where the SST was significantly higher. In 2013, we found weak stratification in a region which was unexpected. In addition, during the same year, a warm small-scale vortex is indicated by the animal-derived temperature data. This allowed us to describe and better understand the dynamics of the water masses, which, so far, have been mainly studied by remote sensors and numerical models. Our results highlight again the potential of using marine top predators as biological platforms to collect oceanographic data, which will enhance and accelerate studies on the Southwest Atlantic Ocean. In a changing world, threatened by climate change, it is urgent to fill information gaps on the coupled ocean-atmosphere system

  7. Effects of long-term grazing disturbance on the belowground storage of organic carbon in the Patagonian Monte, Argentina.

    PubMed

    Larreguy, C; Carrera, A L; Bertiller, M B

    2014-02-15

    The objective of this study was to analyze the effect of grazing disturbance on the amount and the spatial distribution (vertical and horizontal) of root biomass and soil organic carbon (SOC) in order to evaluate whether grazing alters the belowground storage of organic carbon (C) in arid rangelands of the Patagonian Monte. We selected three representative sites (3 ha each) with low, moderate and high grazing disturbance located far, mid-distance and near the watering point, respectively, in rangelands submitted to sheep grazing for more than 100 years. We assessed the canopy structure and identified the four most frequent plant patch types at each site. We selected four replications of each patch type and extracted a soil sample (0-30 cm depth) underneath the canopy and in the middle of the nearest inter-patch bare soil area in winter and summer. We assessed the root and soil dry mass and the respective organic C concentration in each sample and then we estimated the total belowground organic C storage at each site. Total plant and perennial grass cover were lower with high than low grazing disturbance while the reverse occurred with dwarf shrub cover. High grazing disturbance led to the increase in total root biomass in the whole soil profile of patch areas and in the upper soil of inter-patch areas. SOC was higher in patch than in inter-patch areas at all sites but at both areas was reduced with high grazing disturbance. This was probably the result of the low total plant cover and the low and recalcitrant contribution of above and below-ground plant litter to soils at sites with high grazing disturbance. Accordingly, these changes did not result in variations in the total belowground organic C storage. We concluded that high grazing disturbance did not affect the total belowground organic C storage but led to changes in the spatial patterning of this organic C storage (i.e shifting from soil to roots). Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Patagonian wines: implantation of an indigenous strain of Saccharomyces cerevisiae in fermentations conducted in traditional and modern cellars.

    PubMed

    Lopes, Christian A; Rodríguez, María E; Sangorrín, Marcela; Querol, Amparo; Caballero, Adriana C

    2007-02-01

    characteristics. Even when its implantation in T fermentation was lower than that observed in M one, we can conclude that the wine features from MMf9 fermentations were better than those from their respective controls. Therefore, MMf9 selected indigenous strain could be an interesting yeast starter culture in North Patagonian wines.

  9. Synoptic oceanography of San Jorge Gulf (Argentina): A template for Patagonian red shrimp (Pleoticus muelleri) spatial dynamics

    NASA Astrophysics Data System (ADS)

    Glembocki, Nora Gabriela; Williams, Gabriela Noemí; Góngora, María Eva; Gagliardini, Domingo Antonio; Orensanz, José María (Lobo)

    2015-01-01

    An extensive series of high-resolution satellite images from the advanced very high-resolution radiometer (AVHRR) and the sea-viewing wide field-of-view sensor (SeaWIFS) was used in a synoptic oceanographic characterization of San Jorge Gulf (SJG, Argentine Patagonia), an area of great significance for marine conservation and commercial fishing. Remotely sensed information was combined with on-board observer's data and published information to investigate the role of distinctive oceanographic features in relation to the life cycle of the Patagonian red shrimp (Pleoticus muelleri), main target of the industrial fleet in SJG. Three frontal systems-North, South and Outer SJG-are characterized. The North and South SJG fronts are associated with shrimp reproductive aggregations during late spring and summer. While both function as spawning/nursery grounds, they differ from each other in many respects. The thermohaline South SJG front has its maximum expression during the winter, reflecting the influence of the low-salinity Magellanic Plume, while the thermal North SJG front develops during spring and summer as the water column becomes stratified in the central basin of the gulf. Wind-related down-welling inshore of the front prevails in the North SJG, and upwelling in the South SJG frontal area. Chlorophyll a is concentrated near the thermocline on the stratified side of the North SJG, and for that reason, it is not detected by remote sensors during the spring bloom and the summer but becomes apparent offshore from the location of the front when the thermocline deepens during the fall (May). In the South SJG front, Chl-a concentration is apparent inshore from the front all year-round, related in part to upwelling-mediated resuspension. The northern end of the outer front coincides in time and space with a recurrent non-reproductive aggregation of red shrimp between November and January and is presumably related to foraging. It is argued that keeping the North and South

  10. Geographical differentiation in floral traits across the distribution range of the Patagonian oil-secreting Calceolaria polyrhiza: do pollinators matter?

    PubMed

    Cosacov, Andrea; Cocucci, Andrea A; Sérsic, Alicia N

    2014-01-01

    The underlying evolutionary processes of pollinator-driven floral diversification are still poorly understood. According to the Grant-Stebbins model speciation begins with adaptive local differentiation in the response to spatial heterogeneity in pollinators. Although this crucial process links the micro- and macroevolution of floral adaptation, it has received little attention. In this study geographical phenotypic variation was investigated in Patagonian Calceolaria polyrhiza and its pollinators, two oil-collecting bee species that differ in body size and geographical distribution. Patterns of phenotypic variation were examined together with their relationships with pollinators and abiotic factors. Six floral and seven vegetative traits were measured in 45 populations distributed across the entire species range. Climatic and edaphic parameters were determined for 25 selected sites, 2-16 bees per site of the most frequent pollinator species were captured, and a critical flower-bee mechanical fitting trait involved in effective pollination was measured. Geographical patterns of phenotypic and environmental variation were examined using uni- and multivariate analyses. Decoupled geographical variation between corolla area and floral traits related to the mechanical fit of pollinators was explored using a Mantel test. The body length of pollinators and the floral traits related to mechanical fit were strongly correlated with each other. Geographical variation of the mechanical-fit-related traits was decoupled from variation in corolla size; the latter had a geographical pattern consistent with that of the vegetative traits and was mainly affected by climatic gradients. The results are consistent with pollinators playing a key role in shaping floral phenotype at a geographical scale and promoting the differentiation of two floral ecotypes. The relationship between the critical floral-fit-related trait and bee length remained significant even in models that included

  11. Seismic Data Gathering and Validation

    SciTech Connect

    Coleman, Justin

    2015-02-01

    Three recent earthquakes in the last seven years have exceeded their design basis earthquake values (so it is implied that damage to SSC’s should have occurred). These seismic events were recorded at North Anna (August 2011, detailed information provided in [Virginia Electric and Power Company Memo]), Fukushima Daichii and Daini (March 2011 [TEPCO 1]), and Kaswazaki-Kariwa (2007, [TEPCO 2]). However, seismic walk downs at some of these plants indicate that very little damage occurred to safety class systems and components due to the seismic motion. This report presents seismic data gathered for two of the three events mentioned above and recommends a path for using that data for two purposes. One purpose is to determine what margins exist in current industry standard seismic soil-structure interaction (SSI) tools. The second purpose is the use the data to validated seismic site response tools and SSI tools. The gathered data represents free field soil and in-structure acceleration time histories data. Gathered data also includes elastic and dynamic soil properties and structural drawings. Gathering data and comparing with existing models has potential to identify areas of uncertainty that should be removed from current seismic analysis and SPRA approaches. Removing uncertainty (to the extent possible) from SPRA’s will allow NPP owners to make decisions on where to reduce risk. Once a realistic understanding of seismic response is established for a nuclear power plant (NPP) then decisions on needed protective measures, such as SI, can be made.

  12. Procedures for computing site seismicity

    NASA Astrophysics Data System (ADS)

    Ferritto, John

    1994-02-01

    This report was prepared as part of the Navy's Seismic Hazard Mitigation Program. The Navy has numerous bases located in seismically active regions throughout the world. Safe effective design of waterfront structures requires determining expected earthquake ground motion. The Navy's problem is further complicated by the presence of soft saturated marginal soils that can significantly amplify the levels of seismic shaking as evidenced in the 1989 Loma Prieta earthquake. The Naval Facilities Engineering Command's seismic design manual, NAVFAC P355.l, requires a probabilistic assessment of ground motion for design of essential structures. This report presents the basis for the Navy's Seismic Hazard Analysis procedure that was developed and is intended to be used with the Seismic Hazard Analysis computer program and user's manual. This report also presents data on geology and seismology to establish the background for the seismic hazard model developed. The procedure uses the historical epicenter data base and available geologic data, together with source models, recurrence models, and attenuation relationships to compute the probability distribution of site acceleration and an appropriate spectra. This report discusses the developed stochastic model for seismic hazard evaluation and the associated research.

  13. Key aspects governing induced seismicity

    NASA Astrophysics Data System (ADS)

    Buijze, Loes; Wassing, Brecht; Fokker, Peter

    2013-04-01

    In the past decades numerous examples of earthquakes induced by human-induced changes in subsurface fluid pressures have been reported. This poses a major threat to the future development of some of these operations and calls for an understanding and quantification of the seismicity generated. From geomechanical considerations and insights from laboratory experiments the factors controlling induced seismicity may be grouped into 4 categories; the magnitude of the stress disturbance, the pre-existing stress conditions, the reservoir/fault rock properties and the local geometry. We investigated whether the (relative) contributions of these factors and their influence on magnitudes generated could be recognized by looking at the entire dataset of reported cases of induced seismicity as a whole, and what this might imply for future developments. An extensive database has been built out of over a 160 known cases of induced seismicity worldwide, incorporating the relevant geological, seismological and fluid-related parameters. The cases studied include hydrocarbon depletion and secondary recovery, waste water injection, (enhanced) geothermal systems and hydraulic fracturing with observed magnitudes ranging from less than -1.5 to 7. The parameters taken into account were based on the theoretical background of the mechanisms of induced seismicity and include the injection/depletion-related parameters, (spatial) characteristics of seismicity, lithological properties and the local stress situation. Correlations between the seismic response and the geological/geomechanical characteristics of the various sites were investigated. The injected/depleted volumes and the scale of the activities are major controlling factors on the maximum magnitudes generated. Spatial signatures of seismicity such as the depth and lateral spread of the seismicity were observed to be distinct for different activities, which is useful when considering future operations. Where available the local

  14. Advances in Rotational Seismic Measurements

    SciTech Connect

    Pierson, Robert; Laughlin, Darren; Brune, Robert

    2016-10-19

    Rotational motion is increasingly understood to be a significant part of seismic wave motion. Rotations can be important in earthquake strong motion and in Induced Seismicity Monitoring. Rotational seismic data can also enable shear selectivity and improve wavefield sampling for vertical geophones in 3D surveys, among other applications. However, sensor technology has been a limiting factor to date. The US Department of Energy (DOE) and Applied Technology Associates (ATA) are funding a multi-year project that is now entering Phase 2 to develop and deploy a new generation of rotational sensors for validation of rotational seismic applications. Initial focus is on induced seismicity monitoring, particularly for Enhanced Geothermal Systems (EGS) with fracturing. The sensors employ Magnetohydrodynamic (MHD) principles with broadband response, improved noise floors, robustness, and repeatability. This paper presents a summary of Phase 1 results and Phase 2 status.

  15. Micromachined silicon seismic transducers

    SciTech Connect

    Barron, C.C.; Fleming, J.G.; Sniegowski, J.J.; Armour, D.L.; Fleming, R.P.

    1995-08-01

    Batch-fabricated silicon seismic transducers could revolutionize the discipline of CTBT monitoring by providing inexpensive, easily depolyable sensor arrays. Although our goal is to fabricate seismic sensors that provide the same performance level as the current state-of-the-art ``macro`` systems, if necessary one could deploy a larger number of these small sensors at closer proximity to the location being monitored in order to compensate for lower performance. We have chosen a modified pendulum design and are manufacturing prototypes in two different silicon micromachining fabrication technologies. The first set of prototypes, fabricated in our advanced surface- micromachining technology, are currently being packaged for testing in servo circuits -- we anticipate that these devices, which have masses in the 1--10 {mu}g range, will resolve sub-mG signals. Concurrently, we are developing a novel ``mold`` micromachining technology that promises to make proof masses in the 1--10 mg range possible -- our calculations indicate that devices made in this new technology will resolve down to at least sub-{mu}G signals, and may even approach to 10{sup {minus}10} G/{radical}Hz acceleration levels found in the low-earth-noise model.

  16. Seismic event classification system

    DOEpatents

    Dowla, F.U.; Jarpe, S.P.; Maurer, W.

    1994-12-13

    In the computer interpretation of seismic data, the critical first step is to identify the general class of an unknown event. For example, the classification might be: teleseismic, regional, local, vehicular, or noise. Self-organizing neural networks (SONNs) can be used for classifying such events. Both Kohonen and Adaptive Resonance Theory (ART) SONNs are useful for this purpose. Given the detection of a seismic event and the corresponding signal, computation is made of: the time-frequency distribution, its binary representation, and finally a shift-invariant representation, which is the magnitude of the two-dimensional Fourier transform (2-D FFT) of the binary time-frequency distribution. This pre-processed input is fed into the SONNs. These neural networks are able to group events that look similar. The ART SONN has an advantage in classifying the event because the types of cluster groups do not need to be pre-defined. The results from the SONNs together with an expert seismologist's classification are then used to derive event classification probabilities. 21 figures.

  17. Seismic event classification system

    DOEpatents

    Dowla, Farid U.; Jarpe, Stephen P.; Maurer, William

    1994-01-01

    In the computer interpretation of seismic data, the critical first step is to identify the general class of an unknown event. For example, the classification might be: teleseismic, regional, local, vehicular, or noise. Self-organizing neural networks (SONNs) can be used for classifying such events. Both Kohonen and Adaptive Resonance Theory (ART) SONNs are useful for this purpose. Given the detection of a seismic event and the corresponding signal, computation is made of: the time-frequency distribution, its binary representation, and finally a shift-invariant representation, which is the magnitude of the two-dimensional Fourier transform (2-D FFT) of the binary time-frequency distribution. This pre-processed input is fed into the SONNs. These neural networks are able to group events that look similar. The ART SONN has an advantage in classifying the event because the types of cluster groups do not need to be pre-defined. The results from the SONNs together with an expert seismologist's classification are then used to derive event classification probabilities.

  18. Observed Seismic Solitary Waves

    NASA Astrophysics Data System (ADS)

    Bataille, K.

    2008-05-01

    A feature that has been observed for many decades in a variety of instruments, without a solid explanation, is a signal with a shape of a "bump" in velocity records, especially near small earthquakes. This signal arrives at times close to the S wave and has commonly being argued by some to be a nonlinear effect of the instrument (Aki and Richards, 1980), while by others as to be a real earth motion due to an unknown wave propagation phenomena. Here we propose that these observations are seismic solitary waves. The seismic solitary wave arises from an equation that describes the propagation of Love waves within a general nonlinear media. For a specific "bump-like" solution, the dispersive and nonlinear effects balance each other, allowing its propagation without distortion for long distances. Solitary waves have been observed in a variety of physical systems, including the ocean, but so far it has not been recognized in the seismological literature. The theory and modelling of several observations from different instruments will be presented.

  19. Seismic moulin tremor

    NASA Astrophysics Data System (ADS)

    Roeoesli, Claudia; Walter, Fabian; Ampuero, Jean-Paul; Kissling, Edi

    2016-08-01

    Through glacial moulins, meltwater is routed from the glacier surface to its base. Moulins are a main feature feeding subglacial drainage systems and thus influencing basal motion and ice dynamics, but their geometry remains poorly known. Here we show that analysis of the seismic wavefield generated by water falling into a moulin can help constrain its geometry. We present modeling results of hour-long seimic tremors emitted from a vertical moulin shaft, observed with a seismometer array installed at the surface of the Greenland Ice Sheet. The tremor was triggered when the moulin water level exceeded a certain height, which we associate with the threshold for the waterfall to hit directly the surface of the moulin water column. The amplitude of the tremor signal changed over each tremor episode, in close relation to the amount of inflowing water. The tremor spectrum features multiple prominent peaks, whose characteristic frequencies are distributed like the resonant modes of a semiopen organ pipe and were found to depend on the moulin water level, consistent with a source composed of resonant tube waves (water pressure waves coupled to elastic deformation of the moulin walls) along the water-filled moulin pipe. Analysis of surface particle motions lends further support to this interpretation. The seismic wavefield was modeled as a superposition of sustained wave radiation by pressure sources on the side walls and at the bottom of the moulin. The former was found to dominate the wave field at close distance and the latter at large distance to the moulin.

  20. Community Seismic Network (CSN)

    NASA Astrophysics Data System (ADS)

    Clayton, R. W.; Heaton, T. H.; Kohler, M. D.; Chandy, M.; Krause, A.

    2010-12-01

    In collaboration with computer science and earthquake engineering, we are developing a dense network of low-cost accelerometers that send their data via the Internet to a cloud-based center. The goal is to make block-by-block measurements of ground shaking in urban areas, which will provide emergency response information in the case of large earthquakes, and an unprecedented high-frequency seismic array to study structure and the earthquake process with moderate shaking. When deployed in high-rise buildings they can be used to monitor the state of health of the structure. The sensors are capable of a resolution of approximately 80 micro-g, connect via USB ports to desktop computers, and cost about $100 each. The network will adapt to its environment by using network-wide machine learning to adjust the picking sensitivity. We are also looking into using other motion sensing devices such as cell phones. For a pilot project, we plan to deploy more than 1000 sensors in the greater Pasadena area. The system is easily adaptable to other seismically vulnerable urban areas.

  1. Geochronologic and paleontologic evidence for a Pacific-Atlantic connection during the late Oligocene-early Miocene in the Patagonian Andes (43-44°S)

    NASA Astrophysics Data System (ADS)

    Encinas, Alfonso; Pérez, Felipe; Nielsen, Sven N.; Finger, Kenneth L.; Valencia, Victor; Duhart, Paul

    2014-11-01

    Cenozoic marine strata occur in the western, eastern, and central parts of the North Patagonian Andes between ˜43°S and 44°S. Correlation of these deposits is difficult because they occur in small and discontinuous outcrops and their ages are uncertain. In order to better understand the age and sedimentary environment of these strata, we combined U-Pb (LA-MC-ICPMS) geochronology on detrital zircons with sedimentologic and paleontologic (foraminifers and molluscs) studies. Sedimentologic analyses suggest that the Puduhuapi Formation on the western flank of the Andean Cordillera was deposited in a deep-marine setting, the Vargas Formation in the central part of the Andes was deposited at outer-neritic or bathyal depths, and the La Cascada Formation on the eastern flank of the range was deposited in a shallow-marine environment. Geochronologic and paleontologic results indicate that the three marine units were deposited during the late Oligocene-early Miocene interval, although it is not clear whether this occurred during one or more marine incursions in the area. The alluvial(?) conglomeratic deposits of the La Junta Formation, exposed in the proximity of the Vargas Formation outcrops, have a maximum depositional age of ˜26 Ma and could have been deposited during the initial stage of subsidence that affected this region prior to the marine transgression over this area. The occurrence of both Pacific and Atlantic molluscan taxa in the La Cascada and Vargas formations suggests that a marine strait connected both oceans during the accumulation of these units. The new data on the age of the Puduhuapi, Vargas, and La Cascada formations indicate that these units may correlate with lower Miocene marine deposits in the forearc of central and southern Chile (Navidad Formation and equivalent units) and on the eastern flank of the Patagonian Andes (Río Foyel Formation and equivalent units). A late Oligocene-early Miocene age for these marine deposits is a reliable maximum

  2. Seismic Gradiometry using Ambient Seismic Noise in an Anisotropic Earth

    NASA Astrophysics Data System (ADS)

    de Ridder, S. A. L.; Curtis, A.

    2017-02-01

    We introduce a wavefield gradiometry technique to estimate both isotropic and anisotropic local medium characteristics from short recordings of seismic signals by inverting a wave equation. The method exploits the information in the spatial gradients of a seismic wavefield that are calculated using dense deployments of seismic arrays. The application of the method uses the surface wave energy in the ambient seismic field. To estimate isotropic and anisotropic medium properties we invert an elliptically anisotropic wave equation. The spatial derivatives of the recorded wavefield are evaluated by calculating finite differences over nearby recordings, which introduces a systematic anisotropic error. A two step approach corrects this error: finite difference stencils are first calibrated, then the output of the wave-equation inversion is corrected using the linearized impulse response to the inverted velocity anomaly. We test the procedure on ambient seismic noise recorded in a large and dense ocean bottom cable array installed over Ekofisk field. The estimated azimuthal anisotropy forms a circular geometry around the production-induced subsidence bowl. This conforms with results from studies employing controlled sources, and with interferometry correlating long records of seismic noise. Yet in this example, the results where obtained using only a few minutes of ambient seismic noise.

  3. Seismic gradiometry using ambient seismic noise in an anisotropic Earth

    NASA Astrophysics Data System (ADS)

    de Ridder, S. A. L.; Curtis, A.

    2017-05-01

    We introduce a wavefield gradiometry technique to estimate both isotropic and anisotropic local medium characteristics from short recordings of seismic signals by inverting a wave equation. The method exploits the information in the spatial gradients of a seismic wavefield that are calculated using dense deployments of seismic arrays. The application of the method uses the surface wave energy in the ambient seismic field. To estimate isotropic and anisotropic medium properties we invert an elliptically anisotropic wave equation. The spatial derivatives of the recorded wavefield are evaluated by calculating finite differences over nearby recordings, which introduces a systematic anisotropic error. A two-step approach corrects this error: finite difference stencils are first calibrated, then the output of the wave-equation inversion is corrected using the linearized impulse response to the inverted velocity anomaly. We test the procedure on ambient seismic noise recorded in a large and dense ocean bottom cable array installed over Ekofisk field. The estimated azimuthal anisotropy forms a circular geometry around the production-induced subsidence bowl. This conforms with results from studies employing controlled sources, and with interferometry correlating long records of seismic noise. Yet in this example, the results were obtained using only a few minutes of ambient seismic noise.

  4. Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology

    SciTech Connect

    Bob A. Hardage

    2005-07-31

    We have developed a numerical technique that will adjust 3-D S-wave seismic images so that they are depth equivalent to 3-D P-wave seismic images. The ability to make this type of P-SV to P-P depth registration is critical to our elastic wavefield seismic stratigraphy research because we now have higher confidence that depth-equivalent data windows are being used in the P-SV to P-P comparisons that we are making.

  5. Updated Colombian Seismic Hazard Map

    NASA Astrophysics Data System (ADS)

    Eraso, J.; Arcila, M.; Romero, J.; Dimate, C.; Bermúdez, M. L.; Alvarado, C.

    2013-05-01

    The Colombian seismic hazard map used by the National Building Code (NSR-98) in effect until 2009 was developed in 1996. Since then, the National Seismological Network of Colombia has improved in both coverage and technology providing fifteen years of additional seismic records. These improvements have allowed a better understanding of the regional geology and tectonics which in addition to the seismic activity in Colombia with destructive effects has motivated the interest and the need to develop a new seismic hazard assessment in this country. Taking advantage of new instrumental information sources such as new broad band stations of the National Seismological Network, new historical seismicity data, standardized global databases availability, and in general, of advances in models and techniques, a new Colombian seismic hazard map was developed. A PSHA model was applied. The use of the PSHA model is because it incorporates the effects of all seismic sources that may affect a particular site solving the uncertainties caused by the parameters and assumptions defined in this kind of studies. First, the seismic sources geometry and a complete and homogeneous seismic catalog were defined; the parameters of seismic rate of each one of the seismic sources occurrence were calculated establishing a national seismotectonic model. Several of attenuation-distance relationships were selected depending on the type of seismicity considered. The seismic hazard was estimated using the CRISIS2007 software created by the Engineering Institute of the Universidad Nacional Autónoma de México -UNAM (National Autonomous University of Mexico). A uniformly spaced grid each 0.1° was used to calculate the peak ground acceleration (PGA) and response spectral values at 0.1, 0.2, 0.3, 0.5, 0.75, 1, 1.5, 2, 2.5 and 3.0 seconds with return periods of 75, 225, 475, 975 and 2475 years. For each site, a uniform hazard spectrum and exceedance rate curves were calculated. With the results, it is

  6. Seismic Analysis Capability in NASTRAN

    NASA Technical Reports Server (NTRS)

    Butler, T. G.; Strang, R. F.

    1984-01-01

    Seismic analysis is a technique which pertains to loading described in terms of boundary accelerations. Earthquake shocks to buildings is the type of excitation which usually comes to mind when one hears the word seismic, but this technique also applied to a broad class of acceleration excitations which are applied at the base of a structure such as vibration shaker testing or shocks to machinery foundations. Four different solution paths are available in NASTRAN for seismic analysis. They are: Direct Seismic Frequency Response, Direct Seismic Transient Response, Modal Seismic Frequency Response, and Modal Seismic Transient Response. This capability, at present, is invoked not as separate rigid formats, but as pre-packaged ALTER packets to existing RIGID Formats 8, 9, 11, and 12. These ALTER packets are included with the delivery of the NASTRAN program and are stored on the computer as a library of callable utilities. The user calls one of these utilities and merges it into the Executive Control Section of the data deck to perform any of the four options are invoked by setting parameter values in the bulk data.

  7. Latitudinal patterns of export production recorded in surface sediments of the Chilean Patagonian fjords (41-55°S) as a response to water column productivity

    NASA Astrophysics Data System (ADS)

    Aracena, Claudia; Lange, Carina B.; Luis Iriarte, José; Rebolledo, Lorena; Pantoja, Silvio

    2011-03-01

    The Chilean Patagonian fjords region (41-56°S) is characterized by highly complex geomorphology and hydrographic conditions, and strong seasonal and latitudinal patterns in precipitation, freshwater discharge, glacier coverage, and light regime; all of these directly affect biological production in the water column. In this study, we compiled published and new information on water column properties (primary production, nutrients) and surface sediment characteristics (biogenic opal, organic carbon, molar C/N, bulk sedimentary δ13C org) from the Chilean Patagonian fjords between 41°S and 55°S, describing herein the latitudinal pattern of water column productivity and its imprint in the underlying sediments. Based on information collected at 188 water column and 118 sediment sampling sites, we grouped the Chilean fjords into four main zones: Inner Sea of Chiloé (41° to ˜44°S), Northern Patagonia (44° to ˜47°S), Central Patagonia (48-51°S), and Southern Patagonia (Magellan Strait region between 52° and 55°S). Primary production in the Chilean Patagonian fjords was the highest in spring-summer, reflecting the seasonal pattern of water column productivity. A clear north-south latitudinal pattern in primary production was observed, with the highest average spring and summer estimates in the Inner Sea of Chiloé (2427 and 5860 mg C m -2 d -1) and Northern Patagonia (1667 and 2616 mg C m -2 d -1). This pattern was closely related to the higher availability of nutrients, greater solar radiation, and extended photoperiod during the productive season in these two zones. The lowest spring value was found in Caleta Tortel, Central Patagonia (91 mg C m -2 d -1), a site heavily influenced by glacier meltwater and river discharge loaded with glacial sediments. Biogenic opal, an important constituent of the Chilean fjord surface sediments (Si OPAL ˜1-13%), reproduced the general north-south pattern of primary production and was directly related to water column silicic

  8. Exploring the causes of differences in growth rate of the Patagonian scallop Zygochlamys patagonica along its commercial bed distribution in the SW Atlantic

    NASA Astrophysics Data System (ADS)

    Lomovasky, Betina J.; Baldoni, Ana; Ribeiro, Pablo; Alvarez, Graciela; Lasta, Mario; Campodónico, Silvana; Iribarne, Oscar

    2011-08-01

    Comparisons of maximum age and growth rates of the Patagonian scallop Zygochlamys patagonica from seven beds across most of its distribution range (39°30'S to 46°47'S; SW Atlantic) were studied in relation with physical parameters and Chlorophyll a concentration. The estimated maximum age varies between 19 and 25 years across different beds. Differences in the von Bertalanffy parameters were found between beds located at 39°37'S (San Blas) and 42°15'S (Valdes) increasing H ∞, and decreasing k from North to South. These latitudinal trends are correlated with a meridional difference of spring Chl a concentration and the timing of the thermocline decreasing from North to South. Thus, with the available information we hypothesize that differences in scallop growth parameters between beds are due to hydrographical processes that influence primary productivity.

  9. Population dynamics of Philureter trigoniopsis (Monogenea: Ancyrocephalinae) from urinary organs of Galaxias maculatus (Osmeriformes: Galaxiidae) in a cold temperate Andean Patagonian lake (Argentina).

    PubMed

    Viozzi, Gustavo P; Semenas, Liliana G; Gutiérrez, Pablo

    2005-12-01

    Philureter trigoniopsis parasitizes the ureters and urinary bladder of Galaxias maculatus in Patagonian Andean lakes. To investigate factors associated with variation in the prevalence and intensity of this monogenean, fish were sampled periodically over 2 yr in Lake Gutiérrez. Prevalence and mean intensity are higher in smaller fishes than in larger ones. A seasonal pattern was observed, with peak recruitment and peak mean intensity occurring in early spring (September), followed by lows in late summer (January-February). Galaxias maculatus length classes are spatially segregated due to seasonal migrations, so the annual infection cycle is characterized by higher prevalence and intensity from late winter to early summer in the smaller fish from the deep zone of the lake.

  10. Seismic hazard assessment: Issues and alternatives

    USGS Publications Warehouse

    Wang, Z.

    2011-01-01

    Seismic hazard and risk are two very important concepts in engineering design and other policy considerations. Although seismic hazard and risk have often been used inter-changeably, they are fundamentally different. Furthermore, seismic risk is more important in engineering design and other policy considerations. Seismic hazard assessment is an effort by earth scientists to quantify seismic hazard and its associated uncertainty in time and space and to provide seismic hazard estimates for seismic risk assessment and other applications. Although seismic hazard assessment is more a scientific issue, it deserves special attention because of its significant implication to society. Two approaches, probabilistic seismic hazard analysis (PSHA) and deterministic seismic hazard analysis (DSHA), are commonly used for seismic hazard assessment. Although PSHA has been pro-claimed as the best approach for seismic hazard assessment, it is scientifically flawed (i.e., the physics and mathematics that PSHA is based on are not valid). Use of PSHA could lead to either unsafe or overly conservative engineering design or public policy, each of which has dire consequences to society. On the other hand, DSHA is a viable approach for seismic hazard assessment even though it has been labeled as unreliable. The biggest drawback of DSHA is that the temporal characteristics (i.e., earthquake frequency of occurrence and the associated uncertainty) are often neglected. An alternative, seismic hazard analysis (SHA), utilizes earthquake science and statistics directly and provides a seismic hazard estimate that can be readily used for seismic risk assessment and other applications. ?? 2010 Springer Basel AG.

  11. Seismic modeling of carbonate outcrops

    SciTech Connect

    Stafleu, J.; Schlager, W.; Campbell, E.; Everts, A.J. )

    1993-09-01

    Traditionally, seismic modeling has concentrated on one-dimensional borehole modeling and two-dimensional forward modeling of basic structural-stratigraphic schemes, which are directly compared with real seismic data. Two-dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines. Examples include the Dolomites (north Italy), the High Atlas (Morocco), the Vercors (southeast France) and the Last chance Canyon (New Mexico). The seismic models generally are constructed using the following procedure: (1) construction of a detailed lithological model based on direct outcrop observations; (2) division of the lithological model into lithostratigraphic units, using master bedding planes and important facies transitions as boundaries; (3) assignment of petrophysical properties of these lithostratigraphic units; (4) computation of time sections of reflectivity, using different modeling techniques; and (5) convolution with source wavelets of different frequencies. The lithological detail modeled in the case studies lead to some striking results, particularly the discovery of pseudo-unconformities. Pseudo-unconformities are unconformities in seismics, but correspond to rapid changes of dip and facies in outcrop. None of the outcrop geometries studied were correctly portrayed seismically at 25 Hz frequency. However, in some instances the true relationship would emerge gradually at frequencies of 50 to 100 Hz. These results demonstrate that detailed, outcrop-derived/seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less ideal conditions, and what pitfalls may befall the interpreter of real seismic data.

  12. Influence of dissolved organic matter character on mercury incorporation by planktonic organisms: an experimental study using oligotrophic water from Patagonian lakes

    USGS Publications Warehouse

    Diéguez, Maria C.; Queimaliños, Claudia P.; Guevara, Sergio Ribeiro; Marvin-DiPasquale, Mark C.; Cárdenas, Carolina Soto; Arribére, María A.

    2013-01-01

    Ligands present in dissolved organic matter (DOM) form complexes with inorganic divalent mercury (Hg2+) affecting its bioavailability in pelagic food webs. This investigation addresses the influence of a natural gradient of DOM present in Patagonian lakes on the bioaccumulation of Hg2+ (the prevailing mercury species in the water column of these lakes) by the algae Cryptomonas erosa and the zooplankters Brachionus calyciflorus and Boeckella antiqua. Hg2+ accumulation was studied through laboratory experiments using natural water of four oligotrophic Patagonian lakes amended with197Hg2+. The bioavailability of Hg2+ was affected by the concentration and character of DOM. The entrance of Hg2+ into pelagic food webs occurs mostly through passive and active accumulation. The incorporation of Hg2+ by Cryptomonas, up to 27% of the Hg2+ amended, was found to be rapid and dominated by passive adsorption, and was greatest when low molecular weight compounds with protein-like or small phenolic signatures prevailed in the DOM. Conversely, high molecular weight compounds with a humic or fulvic signature kept Hg2+ in the dissolved phase, resulting in the lowest Hg2+ accumulation in this algae. In Brachionus and Boeckella the direct incorporation of Hg from the aqueous phase was up to 3% of the Hg2+ amended. The dietary incorporation of Hg2+ by Boeckella exceeded the direct absorption of this metal in natural water, and was remarkably similar to the Hg2+ adsorbed in their prey. Overall, DOM concentration and character affected the adsorption of Hg2+ by algae through competitive binding, while the incorporation of Hg2+ into the zooplankton was dominated by trophic or dietary transfer.

  13. Deciphering the Role of Tectonic and Climatic Processes on the Landscape Development of the Patagonian Andes Along the Liquiñe-Ofqui Fault System, Chile

    NASA Astrophysics Data System (ADS)

    Buscher, J.; Morata, D.; Arancibia, G.; Cembrano, J. M.

    2016-12-01

    Transpressional plate boundaries often exhibit a correlation between plate obliquity and crustal deformation, but establishing spatial and temporal constraints on this relationship is challenging. The presence of continuous rugged topography along many transpressional fault zones as well as along-fault translation of crustal blocks can obscure the link between plate boundary geometry and mountain belt development. The Liquiñe-Ofqui fault system in the Patagonian Andes is an intra-arc dextral-reverse fault zone linked to oblique plate convergence between the Nazca and South America plates that represents a model setting for studying transpressional landscape development. The topography along the Liquiñe-Ofqui fault system is characterized by glacially and fluvially carved rocks of the Patagonian batholith interspersed by a chain of volcanoes that extends subparallel to the fault zone. Available structural and low-temperature thermochronometry data from the region suggest that both transpressional exhumation and glacial erosion have contributed to the long-term development of the orogen (Cembrano et al., 2002; Thomson, 2002; Thomson et al., 2010). Of particular interest is a near-field locus of young cooling ages thought to reflect shear heating along the fault zone (Thomson, 2002) or focused glacial erosion (Thomson et al., 2010; Herman and Brandon, 2015). To help quantify the topographic response to tectonic and climatic processes along the fault zone, we have evaluated first-order topographic features (gross distribution of elevation, relief and slope) and conducted river profile analyses (stream length-gradient, normalized channel steepness and stream convexity indices) using SRTM digital elevation data for comparison with low-temperature thermochronometry data. Preliminary results suggest that the distribution of topographic and river profile features varies with location along the Liquiñe-Ofqui fault system.

  14. Influence of dissolved organic matter character on mercury incorporation by planktonic organisms: an experimental study using oligotrophic water from Patagonian lakes.

    PubMed

    Diéguez, María C; Queimaliños, Claudia P; Guevara, Sergio Ribeiro; Marvin-DiPasquale, Mark; Cárdenas, Carolina Soto; Arribére, María A

    2013-10-01

    Ligands present in dissolved organic matter (DOM) form complexes with inorganic divalent mercury (Hg2+) affecting its bioavailability in pelagic food webs. This investigation addresses the influence of a natural gradient of DOM present in Patagonian lakes on the bioaccumulation of Hg2+ (the prevailing mercury species in the water column of these lakes) by the algae Cryptomonas erosa and the zooplankters Brachionus calyciflorus and Boeckella antiqua. Hg2+ accumulation was studied through laboratory experiments using natural water of four oligotrophic Patagonian lakes amended witht'97Hg2+. The bioavailability of Hg2+ was affected by the concentration and character of DOM. The entrance of Hg2+ into pelagic food webs occurs mostly through passive and active accumulation. The incorporation of Hg2+ by Cryptomonas, up to 27% of the Hg2+ amended, was found to be rapid and dominated by passive adsorption, and was greatest when low molecular weight compounds with protein-like or small phenolic signatures prevailed in the DOM. Conversely, high molecular weight compounds with a humic or fulvic signature kept Hg2+ in the dissolved phase, resulting in the lowest Hg2+ accumulation in this algae. In Brachionus and Boeckella the direct incorporation of Hg from the aqueous phase was up to 3% of the Hg2+ amended. The dietary incorporation of Hg2+ by Boeckella exceeded the direct absorption of this metal in natural water, and was remarkably similar to the Hg2+ adsorbed in their prey. Overall, DOM concentration and character affected the adsorption of Hg2+ by algae through competitive binding, while the incorporation of Hg2+ into the zooplankton was dominated by trophic or dietary transfer.

  15. Seismic instrumentation of buildings

    USGS Publications Warehouse

    Çelebi, Mehmet

    2000-01-01

    The purpose of this report is to provide information on how and why we deploy seismic instruments in and around building structures. The recorded response data from buildings and other instrumented structures can be and are being primarily used to facilitate necessary studies to improve building codes and therefore reduce losses of life and property during damaging earthquakes. Other uses of such data can be in emergency response situations in large urban environments. The report discusses typical instrumentation schemes, existing instrumentation programs, the steps generally followed in instrumenting a structure, selection and type of instruments, installation and maintenance requirements and data retrieval and processing issues. In addition, a summary section on how recorded response data have been utilized is included. The benefits from instrumentation of structural systems are discussed.

  16. Modeling Regional Seismic Waves

    DTIC Science & Technology

    1992-06-29

    AD-A264 002 PL-TR-92-2186 iIIiL NIl$111111IlIlIl DTIC 0i•ELECTE fl MODELING REGIONAL SEISMIC WAVES c U 19 Donald V . Heimberger David G. Harkrider...09 WU BA 6. AU~m~ri(ý) -Contract F19628-90-K-0049 Donald V . Helmberger David G. Harkrider .I. PLIFOitRNIhGI OACANIZATItO’ NANIL(ý.) ANO A;ýDOREý(eS...01731-5000 PL-TR-92-2186 Contract Manager: James Lewkowicz/GPEH 11. SUh1Lt 0 ’L.i..TAiY v ~u rLS 1 24. ULr r l,, 4 lI0NAVAIL/jILITY STArTMENT 12b

  17. Downhole hydraulic seismic generator

    DOEpatents

    Gregory, Danny L.; Hardee, Harry C.; Smallwood, David O.

    1992-01-01

    A downhole hydraulic seismic generator system for transmitting energy wave vibrations into earth strata surrounding a borehole. The system contains an elongated, unitary housing operably connected to a well head aboveground by support and electrical cabling, and contains clamping apparatus for selectively clamping the housing to the walls of the borehole. The system further comprises a hydraulic oscillator containing a double-actuating piston whose movement is controlled by an electro-servovalve regulating a high pressure hydraulic fluid flow into and out of upper and lower chambers surrounding the piston. The spent hydraulic fluid from the hydraulic oscillator is stored and pumped back into the system to provide high pressure fluid for conducting another run at the same, or a different location within the borehole.

  18. Fractal features of seismic noise

    NASA Astrophysics Data System (ADS)

    Caserta, A.; Consolini, G.; Michelis, P. De

    2003-04-01

    We present experimental observations and data analysis concerning the fractal features of seismic noise in the frequency range from 1 Hz to 40 Hz. In detail, we investigate the 3D average squared soil displacement and the distribution function of its fluctuations for different near-surface geological structures. We found that the seismic noise is consistent with a persistent fractal brownian motion characterized by a Hurst exponent grather than 1/2. Moreover, a clear dependence of the fractal nature of the seismic noise on the near-surface local geology has been found.

  19. Seismic Hazard and Public Safety

    NASA Astrophysics Data System (ADS)

    Marzocchi, Warner

    2013-07-01

    The recent destructive earthquakes in Wenchuan (China), L'Aquila (Italy), Port-au-Prince (Haiti), Christchurch (New Zealand), and Tohoku (Japan) have reignited the discussion over seismic safety. Several scientists [e.g., Stein et al., 2012; Wyss et al., 2012] have questioned the reliability of some seismic hazard maps based on the probabilistic seismic hazard analysis (PSHA)—a widely used probabilistic approach that estimates the likelihood of various levels of ground shaking occurring at a given location in a given future time period—raising an intense discussion on this specific point [Hanks et al., 2012; Frankel, 2013; Stein et al., 2013].

  20. SEISMIC-REFLECTOR DATABASE SOFTWARE.

    USGS Publications Warehouse

    Wright, Evelyn L.; Hosom, John-Paul; ,

    1986-01-01

    The seismic data analysis (SDA) software system facilitates generation of marine seismic reflector databases composed of reflector depths, travel times, root-mean-square and interval velocities, geographic coordinates, and identifying information. System processes include digitizing of seismic profiles and velocity semblance curves, merging of velocity and navigation data with profile travel-time data, calculation of reflector depths in meters, profile and map graphic displays, data editing and smoothing, and entry of finalized data into a comprehensive database. An overview of concepts, file structures, and programs is presented.

  1. Seismic efficiency of meteor airbursts

    NASA Astrophysics Data System (ADS)

    Svetsov, V. V.; Artemieva, N. A.; Shuvalov, V. V.

    2017-08-01

    We present the results of numerical simulation for impacts of relatively small asteroids and ice bodies of 30-100 m in size, decelerated in the atmosphere and exploding before they reach the surface, but still producing seismic effects due to the impact wave reaching the surface. The calculated magnitudes fall within the range of 4 to 6, and average seismic efficiency of these events is 2.5 × 10-5. The results obtained allow the seismic hazard from impacts of cosmic bodies to be estimated.

  2. Seismic calm predictors of rockburst

    NASA Astrophysics Data System (ADS)

    Zmushko, Tatjana; Turuntaev, Sergey; Kulikov, Vladimir

    2013-04-01

    The method of "seismic calm" is widely used for forecasting of strong natural earthquakes (Sobolev G.A., Ponomarev A.V., 2003). The "seismic calm" means that during some time period before the main earthquake, the smaller events (with energies of several order smaller than that of the main earthquake) don't occur. In the presented paper the applicability of the method based on the idea of seismic calm for forecasting rockburst is considered. Three deposits (with seismicity induced by mining) are analyzed: Tashtagol iron deposit (Altai, Russia), Vorkuta (North Ural, Russia) and Barentsburg (Spitsbergen, Norway) coalmines. Local seismic monitoring networks are installed on each of them. The catalogues of seismic events were processed and strong events (rockbursts) were studied (Vorkuta M=2,3; Barentsburg M=1,8; Tashtagol M=1,9÷2,2). All catalogues cover at least two years (Vorkuta - 2008-2011, Barentsburg - 2011-2012, Tashtagol - 2002-2012). It was found that the number of seismic events with magnitudes M=0,5÷1 decreased in a month before the main strong event at Vorkuta coalmines. This event was not directly related with coal mining, its epicenter was located aside of the area of coal mining. In Barentsburg mine the rockburst wasn't so strong as in Vorkuta. The number of events with energies M=0,5 decreased slightly before the rockburst, but not so obviously as in Vorkuta case. The seismic events with high energies occur often at Tashtagol iron deposit. Mining methods used there differ from the coal deposit mining. At coalmines the mining combine runs from edge to edge of the wall, cutting off the coal. The considered iron deposit is developed by a method of block blasting. Not all rockbursts occur immediately after the blasting, so, the problem of the rockburst prediction is important for mining safety. To find rockburst precursors it is necessary to separate the events occurred due to the block blasting from the seismic events due to relocation of stresses in

  3. SEISMIC ANALYSIS FOR PRECLOSURE SAFETY

    SciTech Connect

    E.N. Lindner

    2004-12-03

    The purpose of this seismic preclosure safety analysis is to identify the potential seismically-initiated event sequences associated with preclosure operations of the repository at Yucca Mountain and assign appropriate design bases to provide assurance of achieving the performance objectives specified in the Code of Federal Regulations (CFR) 10 CFR Part 63 for radiological consequences. This seismic preclosure safety analysis is performed in support of the License Application for the Yucca Mountain Project. In more detail, this analysis identifies the systems, structures, and components (SSCs) that are subject to seismic design bases. This analysis assigns one of two design basis ground motion (DBGM) levels, DBGM-1 or DBGM-2, to SSCs important to safety (ITS) that are credited in the prevention or mitigation of seismically-initiated event sequences. An application of seismic margins approach is also demonstrated for SSCs assigned to DBGM-2 by showing a high confidence of a low probability of failure at a higher ground acceleration value, termed a beyond-design basis ground motion (BDBGM) level. The objective of this analysis is to meet the performance requirements of 10 CFR 63.111(a) and 10 CFR 63.111(b) for offsite and worker doses. The results of this calculation are used as inputs to the following: (1) A classification analysis of SSCs ITS by identifying potential seismically-initiated failures (loss of safety function) that could lead to undesired consequences; (2) An assignment of either DBGM-1 or DBGM-2 to each SSC ITS credited in the prevention or mitigation of a seismically-initiated event sequence; and (3) A nuclear safety design basis report that will state the seismic design requirements that are credited in this analysis. The present analysis reflects the design information available as of October 2004 and is considered preliminary. The evolving design of the repository will be re-evaluated periodically to ensure that seismic hazards are properly

  4. The seismic traffic footprint: Tracking trains, aircraft, and cars seismically

    NASA Astrophysics Data System (ADS)

    Riahi, Nima; Gerstoft, Peter

    2015-04-01

    Although naturally occurring vibrations have proven useful to probe the subsurface, the vibrations caused by traffic have not been explored much. Such data, however, are less sensitive to weather and low visibility compared to some common out-of-road traffic sensing systems. We study traffic-generated seismic noise measured by an array of 5200 geophones that covered a 7 × 10 km area in Long Beach (California, USA) with a receiver spacing of 100 m. This allows us to look into urban vibrations below the resolution of a typical city block. The spatiotemporal structure of the anthropogenic seismic noise intensity reveals the Blue Line Metro train activity, departing and landing aircraft in Long Beach Airport and their acceleration, and gives clues about traffic movement along the I-405 highway at night. As low-cost, stand-alone seismic sensors are becoming more common, these findings indicate that seismic data may be useful for traffic monitoring.

  5. Seismic hazard assessment in Central Asia using smoothed seismicity approaches

    NASA Astrophysics Data System (ADS)

    Ullah, Shahid; Bindi, Dino; Zuccolo, Elisa; Mikhailova, Natalia; Danciu, Laurentiu; Parolai, Stefano

    2014-05-01

    Central Asia has a long history of large to moderate frequent seismicity and is therefore considered one of the most seismically active regions with a high hazard level in the world. In the hazard map produced at global scale by GSHAP project in 1999( Giardini, 1999), Central Asia is characterized by peak ground accelerations with return period of 475 years as high as 4.8 m/s2. Therefore Central Asia was selected as a target area for EMCA project (Earthquake Model Central Asia), a regional project of GEM (Global Earthquake Model) for this area. In the framework of EMCA, a new generation of seismic hazard maps are foreseen in terms of macro-seismic intensity, in turn to be used to obtain seismic risk maps for the region. Therefore Intensity Prediction Equation (IPE) had been developed for the region based on the distribution of intensity data for different earthquakes occurred in Central Asia since the end of 19th century (Bindi et al. 2011). The same observed intensity distribution had been used to assess the seismic hazard following the site approach (Bindi et al. 2012). In this study, we present the probabilistic seismic hazard assessment of Central Asia in terms of MSK-64 based on two kernel estimation methods. We consider the smoothed seismicity approaches of Frankel (1995), modified for considering the adaptive kernel proposed by Stock and Smith (2002), and of Woo (1996), modified for considering a grid of sites and estimating a separate bandwidth for each site. The activity rate maps are shown from Frankel approach showing the effects of fixed and adaptive kernel. The hazard is estimated for rock site condition based on 10% probability of exceedance in 50 years. Maximum intensity of about 9 is observed in the Hindukush region.

  6. Progressive Seismic Failure, Seismic Gap, and Great Seismic Risk across the Densely Populated North China Basin

    NASA Astrophysics Data System (ADS)

    Yin, A.; Yu, X.; Shen, Z.

    2014-12-01

    Although the seismically active North China basin has the most complete written records of pre-instrumentation earthquakes in the world, this information has not been fully utilized for assessing potential earthquake hazards of this densely populated region that hosts ~200 million people. In this study, we use the historical records to document the earthquake migration pattern and the existence of a 180-km seismic gap along the 600-km long right-slip Tangshan-Hejian-Cixian (THC) fault zone that cuts across the North China basin. The newly recognized seismic gap, which is centered at Tianjin with a population of 11 million people and ~120 km from Beijing (22 million people) and Tangshan (7 million people), has not been ruptured in the past 1000 years by M≥6 earthquakes. The seismic migration pattern in the past millennium suggests that the epicenters of major earthquakes have shifted towards this seismic gap along the THC fault, which implies that the 180- km gap could be the site of the next great earthquake with M≈7.6 if it is ruptured by a single event. Alternatively, the seismic gap may be explained by aseismic creeping or seismic strain transfer between active faults.

  7. Investigating the point seismic array concept with seismic rotation measurements.

    SciTech Connect

    Abbott, Robert E.; Aldridge, David Franklin

    2009-02-01

    Spatially-distributed arrays of seismometers are often utilized to infer the speed and direction of incident seismic waves. Conventionally, individual seismometers of the array measure one or more orthogonal components of rectilinear particle motion (displacement, velocity, or acceleration). The present work demonstrates that measure of both the particle velocity vector and the particle rotation vector at a single point receiver yields sufficient information to discern the type (compressional or shear), speed, and direction of an incident plane seismic wave. Hence, the approach offers the intriguing possibility of dispensing with spatially-extended received arrays, with their many problematic deployment, maintenance, relocation, and post-acquisition data processing issues. This study outlines straightforward mathematical theory underlying the point seismic array concept, and implements a simple cross-correlation scanning algorithm for determining the azimuth of incident seismic waves from measured acceleration and rotation rate data. The algorithm is successfully applied to synthetic seismic data generated by an advanced finite-difference seismic wave propagation modeling algorithm. Application of the same azimuth scanning approach to data acquired at a site near Yucca Mountain, Nevada yields ambiguous, albeit encouraging, results. Practical issues associated with rotational seismometry are recognized as important, but are not addressed in this investigation.

  8. Ecological responses to mid- and late-Holocene climate variability in the Patagonian Andes (lat 34-55S)

    NASA Astrophysics Data System (ADS)

    Iglesias, V.; Whitlock, C. L.; Bianchi, M. M.; Markgraf, V.; Navarro, D.; Bartlein, P. J.

    2009-12-01

    Along the eastern Andes, a prominent ecotone separates steppe from North Patagonian forest, dominated by Nothofagus spp. and at middle latitudes by Nothofagus spp. and Austrocedrus. The elevational position of the ecotone is determined by effective moisture, which in turn is governed by the strength and latitudinal position of the Southern Westerlies. As a result, past changes in forest composition and fire activity provide an opportunity to examine past climate variations in this region. The vegetation and fire history can be inferred from a longitudinal transect of 8 lake and bog sites. Pollen data indicate that, on millennial time scales, late-glacial steppe was replaced by open forest in the early Holocene and then by closed forest in the middle and late Holocene (south of lat 36S). Charcoal data suggest that fire activity south of latitude 41S was highest between 11 and 8-6 ka and significantly decreased between 8-6 and 3 ka. The opposite pattern occurred north of lat 41S, where fire activity was highest between 6 and 3 ka. Between lat 40 and 43S, fires were nearly as frequent between 3 and 1 ka as in the early Holocene, and this period was followed by a decline in fire activity to the 20th century. The long-term vegetation and fire patterns are partly explained as a response to variations in seasonal and annual insolation and their effect on summer (fire-season) conditions. In the last 5000 years, changes in precipitation and interannual/decadal variability, inferred from independent data, matched closely with variations in the abundance of Nothofagus, Austrocedrus, and Poaceae pollen and charcoal influx. Four climate scenarios (dry conditions/low variability, dry conditions/high variability, wet conditions/high variability, wet conditions/low variability) registered distinctive ecotonal responses. For example, wet conditions led to the expansion of forest into steppe, and high moisture variability, mainly through its effects on fire occurrence, shaped the

  9. Pole tide triggering of seismicity

    NASA Astrophysics Data System (ADS)

    Gorshkov, V.

    2015-08-01

    The influence of the pole tide (PT) on intensity of seismic process is searched on base of Harvard Centroid-moment tensors catalogue (CMT). The normal and shear stresses excited by PT were calculated for each earthquake (EQ) from CMT (32.3 thousands of EQ events after for- and aftershock declustering). There was revealed that there are two maxima of PT influence on weak (less 5.5 magnitudes) thrust-slip EQ near the both extrema (min and max) of shear stress. This influence has 95 % level of statistical significance by Schuster and χ^2 criteria and could explain the 0.6-year periodicity in seismic intensity spectrum. The PT influence on seismicity becomes negligible when PT variations decrease up to 100~mas. This could explain 6-7 years periodicity in seismic intensity spectrum.

  10. Down hole periodic seismic generator

    DOEpatents

    Hardee, Harry C.; Hills, Richard G.; Striker, Richard P.

    1989-01-01

    A down hole periodic seismic generator system for transmitting variable frequency, predominantly shear-wave vibration into earth strata surrounding a borehole. The system comprises a unitary housing operably connected to a well head by support and electrical cabling and contains clamping apparatus for selectively clamping the housing to the walls of the borehole. The system further comprises a variable speed pneumatic oscillator and a self-contained pneumatic reservoir for producing a frequency-swept seismic output over a discrete frequency range.

  11. Advanced downhole periodic seismic generator

    DOEpatents

    Hardee, Harry C.; Hills, Richard G.; Striker, Richard P.

    1991-07-16

    An advanced downhole periodic seismic generator system for transmitting variable frequency, predominantly shear-wave vibration into earth strata surrounding a borehole. The system comprises a unitary housing operably connected to a well head by support and electrical cabling and contains clamping apparatus for selectively clamping the housing to the walls of the borehole. The system further comprises a variable speed pneumatic oscillator and a self-contained pneumatic reservoir for producing a frequency-swept seismic output over a discrete frequency range.

  12. Weak localization of seismic waves.

    PubMed

    Larose, E; Margerin, L; Van Tiggelen, B A; Campillo, M

    2004-07-23

    We report the observation of weak localization of seismic waves in a natural environment. It emerges as a doubling of the seismic energy around the source within a spot of the width of a wavelength, which is several tens of meters in our case. The characteristic time for its onset is the scattering mean-free time that quantifies the internal heterogeneity. Copyright 2004 The American Physical Society

  13. Position paper: Seismic design criteria

    SciTech Connect

    Farnworth, S.K.

    1995-05-22

    The purpose of this paper is to document the seismic design criteria to be used on the Title 11 design of the underground double-shell waste storage tanks and appurtenant facilities of the Multi-Function Waste Tank Facility (MWTF) project, and to provide the history and methodologies for determining the recommended Design Basis Earthquake (DBE) Peak Ground Acceleration (PGA) anchors for site-specific seismic response spectra curves. Response spectra curves for use in design are provided in Appendix A.

  14. Visualization of volumetric seismic data

    NASA Astrophysics Data System (ADS)

    Spickermann, Dela; Böttinger, Michael; Ashfaq Ahmed, Khawar; Gajewski, Dirk

    2015-04-01

    Mostly driven by demands of high quality subsurface imaging, highly specialized tools and methods have been developed to support the processing, visualization and interpretation of seismic data. 3D seismic data acquisition and 4D time-lapse seismic monitoring are well-established techniques in academia and industry, producing large amounts of data to be processed, visualized and interpreted. In this context, interactive 3D visualization methods proved to be valuable for the analysis of 3D seismic data cubes - especially for sedimentary environments with continuous horizons. In crystalline and hard rock environments, where hydraulic stimulation techniques may be applied to produce geothermal energy, interpretation of the seismic data is a more challenging problem. Instead of continuous reflection horizons, the imaging targets are often steep dipping faults, causing a lot of diffractions. Without further preprocessing these geological structures are often hidden behind the noise in the data. In this PICO presentation we will present a workflow consisting of data processing steps, which enhance the signal-to-noise ratio, followed by a visualization step based on the use the commercially available general purpose 3D visualization system Avizo. Specifically, we have used Avizo Earth, an extension to Avizo, which supports the import of seismic data in SEG-Y format and offers easy access to state-of-the-art 3D visualization methods at interactive frame rates, even for large seismic data cubes. In seismic interpretation using visualization, interactivity is a key requirement for understanding complex 3D structures. In order to enable an easy communication of the insights gained during the interactive visualization process, animations of the visualized data were created which support the spatial understanding of the data.

  15. Seismic stratigraphy of the Bahamas

    SciTech Connect

    Ladd, J.W.; Sheridan, R.E.

    1987-06-01

    Seismic reflection profiles from the Straits of Florida, Northwest Providence Channel, Tongue of the Ocean, and Exuma Sound reveal a seismic stratigraphy characterized by a series of prograding Upper Cretaceous and Tertiary seismic sequences with seismic velocities generally less than 4 km/sec overlying a Lower Cretaceous section of low-amplitude reflections which are more nearly horizontal than the overlying prograding clinoforms and have seismic velocities greater than 5 km/sec. The prograding units are detrital shallow-water carbonates shed from nearby carbonate banks into deep intrabank basins that were established in the Late Cretaceous. The Lower Cretaceous units are probably shallow-water carbonate banks that were drowned in the middle Cretaceous but which, during the Early Cretaceous, extended from Florida throughout the Bahamas region. The seismic reflection profiles reveal a sharp angular unconformity at 5-sec two-way traveltime in northwest Tongue of the Ocean, suggesting a rift-drift unconformity and deposition on thinned continental crust. No such unconformity is seen in central and southeast Tongue of the Ocean or in Exuma Sound, suggesting that these areas are built on oceanic crust.

  16. Newberry Seismic Deployment Fieldwork Report

    SciTech Connect

    Wang, J; Templeton, D C

    2012-03-21

    This report summarizes the seismic deployment of Lawrence Livermore National Laboratory (LLNL) Geotech GS-13 short-period seismometers at the Newberry Enhanced Geothermal System (EGS) Demonstration site located in Central Oregon. This Department of Energy (DOE) demonstration project is managed by AltaRock Energy Inc. AltaRock Energy had previously deployed Geospace GS-11D geophones at the Newberry EGS Demonstration site, however the quality of the seismic data was somewhat low. The purpose of the LLNL deployment was to install more sensitive sensors which would record higher quality seismic data for use in future seismic studies, such as ambient noise correlation, matched field processing earthquake detection studies, and general EGS microearthquake studies. For the LLNL deployment, seven three-component seismic stations were installed around the proposed AltaRock Energy stimulation well. The LLNL seismic sensors were connected to AltaRock Energy Gueralp CMG-DM24 digitizers, which are powered by AltaRock Energy solar panels and batteries. The deployment took four days in two phases. In phase I, the sites were identified, a cavity approximately 3 feet deep was dug and a flat concrete pad oriented to true North was made for each site. In phase II, we installed three single component GS-13 seismometers at each site, quality controlled the data to ensure that each station was recording data properly, and filled in each cavity with native soil.

  17. Seismic risk perception in Italy

    NASA Astrophysics Data System (ADS)

    Crescimbene, Massimo; La Longa, Federica; Camassi, Romano; Pino, Nicola Alessandro; Peruzza, Laura

    2014-05-01

    Risk perception is a fundamental element in the definition and the adoption of preventive counter-measures. In order to develop effective information and risk communication strategies, the perception of risks and the influencing factors should be known. This paper presents results of a survey on seismic risk perception in Italy conducted from January 2013 to present . The research design combines a psychometric and a cultural theoretic approach. More than 7,000 on-line tests have been compiled. The data collected show that in Italy seismic risk perception is strongly underestimated; 86 on 100 Italian citizens, living in the most dangerous zone (namely Zone 1), do not have a correct perception of seismic hazard. From these observations we deem that extremely urgent measures are required in Italy to reach an effective way to communicate seismic risk. Finally, the research presents a comparison between groups on seismic risk perception: a group involved in campaigns of information and education on seismic risk and a control group.

  18. Quantifying the seismicity on Taiwan

    NASA Astrophysics Data System (ADS)

    Wu, Yi-Hsuan; Chen, Chien-Chih; Turcotte, Donald L.; Rundle, John B.

    2013-07-01

    We quantify the seismicity on the island of Taiwan using the frequency-magnitude statistics of earthquakes since 1900. A break in Gutenberg-Richter scaling for large earthquakes in global seismicity has been observed, this break is also observed in our Taiwan study. The seismic data from the Central Weather Bureau Seismic Network are in good agreement with the Gutenberg-Richter relation taking b ≈ 1 when M < 7. For large earthquakes, M ≥ 7, the seismic data fit Gutenberg-Richter scaling with b ≈ 1.5. If the Gutenberg-Richter scaling for M < 7 earthquakes is extrapolated to larger earthquakes, we would expect a M > 8 earthquake in the study region about every 25 yr. However, our analysis shows a lower frequency of occurrence of large earthquakes so that the expected frequency of M > 8 earthquakes is about 200 yr. The level of seismicity for smaller earthquakes on Taiwan is about 12 times greater than in Southern California and the possibility of a M ≈ 9 earthquake north or south of Taiwan cannot be ruled out. In light of the Fukushima, Japan nuclear disaster, we also discuss the implications of our study for the three operating nuclear power plants on the coast of Taiwan.

  19. Artificial Seismic Shadow Zone by Acoustic Metamaterials

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Hoon; Das, Mukunda P.

    2013-08-01

    We developed a new method of earthquake-proof engineering to create an artificial seismic shadow zone using acoustic metamaterials. By designing huge empty boxes with a few side-holes corresponding to the resonance frequencies of seismic waves and burying them around the buildings that we want to protect, the velocity of the seismic wave becomes imaginary. The meta-barrier composed of many meta-boxes attenuates the seismic waves, which reduces the amplitude of the wave exponentially by dissipating the seismic energy. This is a mechanical method of converting the seismic energy into sound and heat. We estimated the sound level generated from a seismic wave. This method of area protection differs from the point protection of conventional seismic design, including the traditional cloaking method. The artificial seismic shadow zone is tested by computer simulation and compared with a normal barrier.

  20. How Forgetful are Seismic Waves ?

    NASA Astrophysics Data System (ADS)

    Milkereit, B.

    2005-05-01

    3D surface seismic and vertical seismic profiling (VSP) techniques can be employed to image crustal structures in complex geological settings. The effects of heterogeneities on seismic wave propagation can be described in terms of different propagation regimes (Wu, 1989): quasi-homogeneous for heterogeneities too small to be seen by seismic waves, Rayleigh scattering, Mie scattering and small-angle scattering. These scattering regimes cause characteristic amplitude, phase and travel time fluctuation, which can be used to obtain estimates of scale length. Horizontal resolution of exploration seismic data is often discussed in terms of Fresnel zone. For surface and VSP data, the Fresnel radius increases with increasing depth of investigation. In addition, the lateral resolution is limited by the effective frequency content of the seismic signal. Based on strong contrast in petrophysical data, crustal exploration targets (such as gas-hydrates, permafrost or massive sulfide ores) should make strong P-wave, S-wave and converted wave reflectors against most background velocity models. In the context of realistic geological models, 3D numerical simulations are required to better assess elastic wave interactions with high acoustic impedance targets. In addition, it is important to study the influence of composition and shape of high acoustic impedance targets on the full scattered wavefield through a series of numerical modeling experiments based on the 3D elastic finite-difference (FD) method. Massive sulfide ores consisting of the end-member sulfide minerals pyrite, sphalerite, and galena, which span the full range of observed P- and S- wave velocities and densities in ore rocks, as well as gabbro inclusions, are investigated for different shapes which represent the complex morphologies often observed for ore deposits. 3D FD modeling reveals that large ore deposits lead to a strong and complex scattering response that is often dominated by shear-wave events (Bohlen et al

  1. Romanian Educational Seismic Network Project

    NASA Astrophysics Data System (ADS)

    Tataru, Dragos; Ionescu, Constantin; Zaharia, Bogdan; Grecu, Bogdan; Tibu, Speranta; Popa, Mihaela; Borleanu, Felix; Toma, Dragos; Brisan, Nicoleta; Georgescu, Emil-Sever; Dobre, Daniela; Dragomir, Claudiu-Sorin

    2013-04-01

    Romania is one of the most active seismic countries in Europe, with more than 500 earthquakes occurring every year. The seismic hazard of Romania is relatively high and thus understanding the earthquake phenomena and their effects at the earth surface represents an important step toward the education of population in earthquake affected regions of the country and aims to raise the awareness about the earthquake risk and possible mitigation actions. In this direction, the first national educational project in the field of seismology has recently started in Romania: the ROmanian EDUcational SEISmic NETwork (ROEDUSEIS-NET) project. It involves four partners: the National Institute for Earth Physics as coordinator, the National Institute for Research and Development in Construction, Urban Planning and Sustainable Spatial Development " URBAN - INCERC" Bucharest, the Babeş-Bolyai University (Faculty of Environmental Sciences and Engineering) and the software firm "BETA Software". The project has many educational, scientific and social goals. The main educational objectives are: training students and teachers in the analysis and interpretation of seismological data, preparing of several comprehensive educational materials, designing and testing didactic activities using informatics and web-oriented tools. The scientific objective is to introduce into schools the use of advanced instruments and experimental methods that are usually restricted to research laboratories, with the main product being the creation of an earthquake waveform archive. Thus a large amount of such data will be used by students and teachers for educational purposes. For the social objectives, the project represents an effective instrument for informing and creating an awareness of the seismic risk, for experimentation into the efficacy of scientific communication, and for an increase in the direct involvement of schools and the general public. A network of nine seismic stations with SEP seismometers

  2. Seismic energy source

    SciTech Connect

    Trudeau, C.A.

    1987-10-20

    A hydraulically actuated seismic energy apparatus for producing as single impact with the surface of the earth is described including: hydraulic means including a ram cylinder adapted to be vertically disposed above the surface of the earth, and a ram member movable relative to the ram cylinder in response to fluid under pressure between a first upper position and a second lower position where the ram member has face plate and impacts and compresses the earth in the lower position; first pressure responsive means coupled to the ram cylinder for providing a defined volume of fluid at a first actuation pressure to the ram member for accelerating the ram member in a downward direction between the first and second positions until the face plate of the ram member is in proximate spaced relationship to the surface of the earth; and second pressure responsive means coupled to the first pressure responsive means for providing a low pressure fluid chamber to receive return of fluid from the cylinder when a reaction force in the compressed earth overcomes the downward acceleration forces of the ram member at the lower position thereby accelerate the ram member in an upward direction from the lower position toward the upper position.

  3. Practical Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Mutter, John C.

    This book provides something of a manual or “how-to” guide to the derivation of stratigraphic and structural information from multichannel seismic reflection profiles. Its emphasis is, as the title suggests, the practical business of just how one goes about extracting this information. I believe the intent is that one should be able to first read the book, then place it on the work table next to a reflection profile to be interpreted, and by examining the profile while thumbing through the book, find interpreted examples of features similar to those to be interpreted and hence be guided toward a geological interpretation of the data. The book is replete with examples—I counted more than 130 individual reflection profile segments illustrating commonly observed structural and stratigraphic features. Beyond this, the reader also gets a large amount of practical advice, such as the type of colored pencils and eraser to use, what phase of the reflecting event should be marked, how to fold the profiles to check for ties at line intersections, how to mark faults, the various types of unconformity, and many, many other intensely practical aspects of data interpretation.

  4. Monitoring seismic wave speed by an active seismic source

    NASA Astrophysics Data System (ADS)

    Yokoyama, K.; Kawakata, H.; Doi, I.; Okubo, M.; Saiga, A.

    2012-12-01

    Decreases in elastic wave speed around cracked zones prior to faulting in rock fracture experiments have been reported (e.g., Yukutake, 1989; Yoshimitsu et al., 2009). These decreases in wave speed have been considered to be associated with crack and fault growth based on non-destructive observation using X-ray CT scan (Kawakata et al., 1999). Meanwhile, there were some reports on the decreases in seismic wave speed along paths that cross the hypocentral area in periods including some large earthquakes. Uchida et al. (2002) analyzed seismic waveform with explosive sources before and after the 1998 northern Iwate prefecture earthquake, and they showed that the decrease in seismic wave speed approximately 0.1-0.9 % by the earthquake occurrence. Justin et al. (2007) reported the reduction in seismic wave speed accompanied with the 2003 Tokachi oki earthquake around the rupture area by using the four repeating earthquakes that occurred before and after the 2003 Tokachi oki earthquake. However, seismograms of explosive sources or repeating earthquakes are hard to be frequently recorded, which makes the time intervals of estimated seismic wave speed be too long to distinguish preseismic changes from coseismic and post seismic changes. In order to monitor crustal structures and detecting the variation of rock properties in the crust, a kind of active seismic source systems ACROSS (Accurately Controlled Routinely Operated Signal System) has been developed(e.g., Kunitomo and Kumazawa, 2004). We used the controlled seismic source ACROSS, which installed at the Tono mine, Gifu prefecture, central Japan and has been routinely operated by Tono Geoscience center of JAEA (Japan Atomic Energy Agency), automatically. Frequency modulated seismic waves are continuously radiated from approximately 10-20 Hz by eccentric rotation of the source. In order to investigate the stability of ACROSS signals, we used seismograms recorded at the 110m depth of Shobasama observing site, which is

  5. The Recent Seismicity Near Tabouk

    NASA Astrophysics Data System (ADS)

    Aldamegh, K. S.; Aljurayed, I. M.; Mostafa, M. H.

    2007-12-01

    Tabouk is a very populated historic city that was jolted by a 5.2 earthquake in June of 2004. Fortunately no damage has been reported. The seismic activity attracted the attention of residence as well as scientists and authorities in the region. The earthquake is located in a neogene/Quaternary volcanic region named Harat ar Raha about 140 km south west of Tabouk. Not far from the Red Sea and the Gulf of Aqaba, Tabouk is at the north western edge of the Arabian Shield. The main shock was followed by small magnitude (less than 4) aftershocks. Moreover the region remained active (many events with a magnitudes less than 2 has been recorded) every now and then until now. According to historic reports the city and the region surrounding it has been affected by a large magnitude earthquake in March of 1068 that caused about 20000 deaths in the region. The goal of this study is to map the seismicity and understand the source of the activity. The results would hopefully have an impact on hazard mitigation in the region. Realizing that more seismic stations were needed to better monitor the activities and locate the small events, we deployed 5 temporary short period and broadband seismic stations to the region. We have also collected waveform data from 23 broadband stations that are part of the National Seismic Network previously run by King Abdulaziz City for Science and Technology (KACST). Our early results show that the historic event location does not match with the current seismicity. In addition we have been able to present a new and more accurate seismicity map for the study region. This project has been fully funded by KACST and is planned to last until the end of 2008.

  6. Midget Seismic in Sandbox Models

    NASA Astrophysics Data System (ADS)

    Krawczyk, C. M.; Buddensiek, M. L.; Philipp, J.; Kukowski, N.; Oncken, O.

    2008-12-01

    Analog sandbox simulation has been applied to study geological processes to provide qualitative and quantitative insights into specific geological problems. In nature, the structures, which are simulated in those sandbox models, are often inferred from seismic data. With the study introduced here, we want to combine the analog sandbox simulation techniques with seismic physical modeling of those sandbox models. The long-term objectives of this approach are (1) imaging of seismic and seismological events of actively deforming and static 3D analogue models, and (2) assessment of the transferability of the model data to field data in order to improve field data acquisition and interpretation according to the addressed geological problem. To achieve this objective, a new midget-seismic facility for laboratory use was designed and developed, comprising a seismic tank, a PC control unit including piezo-electric transducers, and a positioning system. The first experiments are aimed at studying the wave field properties of the piezo- transducers in order to investigate their feasibility for seismic profiling. The properties investigated are their directionality and the change of waveform due to their size (5-12 mm) compared to the wavelengths (< 1.5 mm). The best quality signals and least directionality and waveform change are achieved when the center source frequency is between 350-500 kHz, and the offset is less than 8 cm for a reflector depth of 10 cm. With respect to the technical hardware reflection processing on such a small scale is feasible as long as the offset does not exceed a certain value, which is dependent on the reflector depth and frequency. The next steps will include a study of material properties and the effects of wave propagation in an-/isotropic media by physical studies, before we finally start using different seismic imaging and processing techniques on static and actively deforming 3D analog models.

  7. National Seismic Network of Georgia

    NASA Astrophysics Data System (ADS)

    Tumanova, N.; Kakhoberashvili, S.; Omarashvili, V.; Tserodze, M.; Akubardia, D.

    2016-12-01

    Georgia, as a part of the Southern Caucasus, is tectonically active and structurally complex region. It is one of the most active segments of the Alpine-Himalayan collision belt. The deformation and the associated seismicity are due to the continent-continent collision between the Arabian and Eurasian plates. Seismic Monitoring of country and the quality of seismic data is the major tool for the rapid response policy, population safety, basic scientific research and in the end for the sustainable development of the country. National Seismic Network of Georgia has been developing since the end of 19th century. Digital era of the network started from 2003. Recently continuous data streams from 25 stations acquired and analyzed in the real time. Data is combined to calculate rapid location and magnitude for the earthquake. Information for the bigger events (Ml>=3.5) is simultaneously transferred to the website of the monitoring center and to the related governmental agencies. To improve rapid earthquake location and magnitude estimation the seismic network was enhanced by installing additional 7 new stations. Each new station is equipped with coupled Broadband and Strong Motion seismometers and permanent GPS system as well. To select the sites for the 7 new base stations, we used standard network optimization techniques. To choose the optimal sites for new stations we've taken into account geometry of the existed seismic network, topographic conditions of the site. For each site we studied local geology (Vs30 was mandatory for each site), local noise level and seismic vault construction parameters. Due to the country elevation, stations were installed in the high mountains, no accessible in winter due to the heavy snow conditions. To secure online data transmission we used satellite data transmission as well as cell data network coverage from the different local companies. As a result we've already have the improved earthquake location and event magnitudes. We

  8. Fluid injection and induced seismicity

    NASA Astrophysics Data System (ADS)

    Kendall, Michael; Verdon, James

    2016-04-01

    The link between fluid injection, or extraction, and induced seismicity has been observed in reservoirs for many decades. In fact spatial mapping of low magnitude events is routinely used to estimate a stimulated reservoir volume. However, the link between subsurface fluid injection and larger felt seismicity is less clear and has attracted recent interest with a dramatic increase in earthquakes associated with the disposal of oilfield waste fluids. In a few cases, hydraulic fracturing has also been linked to induced seismicity. Much can be learned from past case-studies of induced seismicity so that we can better understand the risks posed. Here we examine 12 case examples and consider in particular controls on maximum event size, lateral event distributions, and event depths. Our results suggest that injection volume is a better control on maximum magnitude than past, natural seismicity in a region. This might, however, simply reflect the lack of baseline monitoring and/or long-term seismic records in certain regions. To address this in the UK, the British Geological Survey is leading the deployment of monitoring arrays in prospective shale gas areas in Lancashire and Yorkshire. In most cases, seismicity is generally located in close vicinity to the injection site. However, in some cases, the nearest events are up to 5km from the injection point. This gives an indication of the minimum radius of influence of such fluid injection projects. The most distant events are never more than 20km from the injection point, perhaps implying a maximum radius of influence. Some events are located in the target reservoir, but most occur below the injection depth. In fact, most events lie in the crystalline basement underlying the sedimentary rocks. This suggests that induced seismicity may not pose a leakage risk for fluid migration back to the surface, as it does not impact caprock integrity. A useful application for microseismic data is to try and forecast induced seismicity

  9. 2015 USGS Seismic Hazard Model for Induced Seismicity

    NASA Astrophysics Data System (ADS)

    Petersen, M. D.; Mueller, C. S.; Moschetti, M. P.; Hoover, S. M.; Ellsworth, W. L.; Llenos, A. L.; Michael, A. J.

    2015-12-01

    Over the past several years, the seismicity rate has increased markedly in multiple areas of the central U.S. Studies have tied the majority of this increased activity to wastewater injection in deep wells and hydrocarbon production. These earthquakes are induced by human activities that change rapidly based on economic and policy decisions, making them difficult to forecast. Our 2014 USGS National Seismic Hazard Model and previous models are intended to provide the long-term hazard (2% probability of exceedance in 50 years) and are based on seismicity rates and patterns observed mostly from tectonic earthquakes. However, potentially induced earthquakes were identified in 14 regions that were not included in the earthquake catalog used for constructing the 2014 model. We recognized the importance of considering these induced earthquakes in a separate hazard analysis, and as a result in April 2015 we released preliminary models that explored the impact of this induced seismicity on the hazard. Several factors are important in determining the hazard from induced seismicity: period of the catalog that optimally forecasts the next year's activity, earthquake magnitude-rate distribution, earthquake location statistics, maximum magnitude, ground motion models, and industrial drivers such as injection rates. The industrial drivers are not currently available in a form that we can implement in a 1-year model. Hazard model inputs have been evaluated by a broad group of scientists and engineers to assess the range of acceptable models. Results indicate that next year's hazard is significantly higher by more than a factor of three in Oklahoma, Texas, and Colorado compared to the long-term 2014 hazard model. These results have raised concern about the impacts of induced earthquakes on the built environment and have led to many engineering and policy discussions about how to mitigate these effects for the more than 7 million people that live near areas of induced seismicity.

  10. A study on seismicity and seismic hazard for Karnataka State

    NASA Astrophysics Data System (ADS)

    Sitharam, T. G.; James, Naveen; Vipin, K. S.; Raj, K. Ganesha

    2012-04-01

    This paper presents a detailed study on the seismic pattern of the state of Karnataka and also quantifies the seismic hazard for the entire state. In the present work, historical and instrumental seismicity data for Karnataka (within 300 km from Karnataka political boundary) were compiled and hazard analysis was done based on this data. Geographically, Karnataka forms a part of peninsular India which is tectonically identified as an intraplate region of Indian plate. Due to the convergent movement of the Indian plate with the Eurasian plate, movements are occurring along major intraplate faults resulting in seismic activity of the region and hence the hazard assessment of this region is very important. Apart from referring to seismotectonic atlas for identifying faults and fractures, major lineaments in the study area were also mapped using satellite data. The earthquake events reported by various national and international agencies were collected until 2009. Declustering of earthquake events was done to remove foreshocks and aftershocks. Seismic hazard analysis was done for the state of Karnataka using both deterministic and probabilistic approaches incorporating logic tree methodology. The peak ground acceleration (PGA) at rock level was evaluated for the entire state considering a grid size of 0.05° × 0.05°. The attenuation relations proposed for stable continental shield region were used in evaluating the seismic hazard with appropriate weightage factors. Response spectra at rock level for important Tier II cities and Bangalore were evaluated. The contour maps showing the spatial variation of PGA values at bedrock are presented in this work.

  11. Generalized seismic analysis

    NASA Technical Reports Server (NTRS)

    Butler, Thomas G.

    1993-01-01

    There is a constant need to be able to solve for enforced motion of structures. Spacecraft need to be qualified for acceleration inputs. Truck cargoes need to be safeguarded from road mishaps. Office buildings need to withstand earthquake shocks. Marine machinery needs to be able to withstand hull shocks. All of these kinds of enforced motions are being grouped together under the heading of seismic inputs. Attempts have been made to cope with this problem over the years and they usually have ended up with some limiting or compromise conditions. The crudest approach was to limit the problem to acceleration occurring only at a base of a structure, constrained to be rigid. The analyst would assign arbitrarily outsized masses to base points. He would then calculate the magnitude of force to apply to the base mass (or masses) in order to produce the specified acceleration. He would of necessity have to sacrifice the determination of stresses in the vicinity of the base, because of the artificial nature of the input forces. The author followed the lead of John M. Biggs by using relative coordinates for a rigid base in a 1975 paper, and again in a 1981 paper . This method of relative coordinates was extended and made operational as DMAP ALTER packets to rigid formats 9, 10, 11, and 12 under contract N60921-82-C-0128. This method was presented at the twelfth NASTRAN Colloquium. Another analyst in the field developed a method that computed the forces from enforced motion then applied them as a forcing to the remaining unknowns after the knowns were partitioned off. The method was translated into DMAP ALTER's but was never made operational. All of this activity jelled into the current effort. Much thought was invested in working out ways to unshakle the analysis of enforced motions from the limitations that persisted.

  12. The Geoscope Seismic Network

    NASA Astrophysics Data System (ADS)

    Leroy, N.; Stutzmann, E.; Maggi, A.; Vallee, M.; Pardo, C.

    2014-12-01

    The GEOSCOPE observatory provides 32 years of continuous broadband data to the scientific community. The 31 GEOSCOPE stations are installed in 19 countries, across all continents and on islands throughout the oceans. They are equipped with three component very broadband seismometers (STS1 or STS2) and 24 or 26 bit digitizers (Q330HR). Seismometers are installed with warpless base plates, which decrease long period noise on horizontal components by up to 15dB. In most stations, a pressure gauge and a thermometer are also installed. In 2014, we upgraded 4 stations: SSB in France, CAN in Australia, ROCAM in Rodrigues and ECH in France. 27 stations send data in real or near real time to the GEOSCOPE Data Center and to tsunami warning centers. Continuous data of all stations are collected in real time or with a delay by the IPGP Data Center in Paris where they are validated, archived and made available to the international scientific community through different interfaces including web services (see details on http://geoscope.ipgp.fr). In 2015, GEOSCOPE data will also be available through the French national data center RESIF. Seismic noise level of the continuous data are computed every 24 hours and accessible via the geoscope web site. GEOSCOPE data are also validated by comparing real and synthetic body wave waveforms using the SCARDEC method (Vallee et al., 2011). The information on earthquake characteristics, on GEOSCOPE data available for each event and on the waveform fit for each channel are available through the geoscope web portal.

  13. Generalized seismic analysis

    NASA Astrophysics Data System (ADS)

    Butler, Thomas G.

    1993-09-01

    There is a constant need to be able to solve for enforced motion of structures. Spacecraft need to be qualified for acceleration inputs. Truck cargoes need to be safeguarded from road mishaps. Office buildings need to withstand earthquake shocks. Marine machinery needs to be able to withstand hull shocks. All of these kinds of enforced motions are being grouped together under the heading of seismic inputs. Attempts have been made to cope with this problem over the years and they usually have ended up with some limiting or compromise conditions. The crudest approach was to limit the problem to acceleration occurring only at a base of a structure, constrained to be rigid. The analyst would assign arbitrarily outsized masses to base points. He would then calculate the magnitude of force to apply to the base mass (or masses) in order to produce the specified acceleration. He would of necessity have to sacrifice the determination of stresses in the vicinity of the base, because of the artificial nature of the input forces. The author followed the lead of John M. Biggs by using relative coordinates for a rigid base in a 1975 paper, and again in a 1981 paper . This method of relative coordinates was extended and made operational as DMAP ALTER packets to rigid formats 9, 10, 11, and 12 under contract N60921-82-C-0128. This method was presented at the twelfth NASTRAN Colloquium. Another analyst in the field developed a method that computed the forces from enforced motion then applied them as a forcing to the remaining unknowns after the knowns were partitioned off. The method was translated into DMAP ALTER's but was never made operational. All of this activity jelled into the current effort. Much thought was invested in working out ways to unshakle the analysis of enforced motions from the limitations that persisted.

  14. Seismic waves increase permeability.

    PubMed

    Elkhoury, Jean E; Brodsky, Emily E; Agnew, Duncan C

    2006-06-29

    Earthquakes have been observed to affect hydrological systems in a variety of ways--water well levels can change dramatically, streams can become fuller and spring discharges can increase at the time of earthquakes. Distant earthquakes may even increase the permeability in faults. Most of these hydrological observations can be explained by some form of permeability increase. Here we use the response of water well levels to solid Earth tides to measure permeability over a 20-year period. At the time of each of seven earthquakes in Southern California, we observe transient changes of up to 24 degrees in the phase of the water level response to the dilatational volumetric strain of the semidiurnal tidal components of wells at the Piñon Flat Observatory in Southern California. After the earthquakes, the phase gradually returns to the background value at a rate of less than 0.1 degrees per day. We use a model of axisymmetric flow driven by an imposed head oscillation through a single, laterally extensive, confined, homogeneous and isotropic aquifer to relate the phase response to aquifer properties. We interpret the changes in phase response as due to changes in permeability. At the time of the earthquakes, the permeability at the site increases by a factor as high as three. The permeability increase depends roughly linearly on the amplitude of seismic-wave peak ground velocity in the range of 0.21-2.1 cm s(-1). Such permeability increases are of interest to hydrologists and oil reservoir engineers as they affect fluid flow and might determine long-term evolution of hydrological and oil-bearing systems. They may also be interesting to seismologists, as the resulting pore pressure changes can affect earthquakes by changing normal stresses on faults.

  15. Seismic Resonant Emission

    NASA Astrophysics Data System (ADS)

    Korneev, V. A.

    2007-12-01

    There are several classes of underground objects which can produce resonant emission after being hit by incident seismic waves. Those objects include tunnels, pipes, buried containers, ground-filled excavations, unexploded ordinances, fluid-filled fractures, mine shafts, and the like. Being high contrast scatterers, these objects are capable of generating strong scattered waves where primary PP, PS, SS waves carry away most of the energy which was brought by incident waves. For both high- and low- velocity objects the primary scattered waves have the same order of magnitude as incident waves. The main difference between these groups of objects is in later arrivals of multiple scattered waves. While high-velocity objects effectively radiate most of the energy soon after impact, the low-velocity objects trap some fraction of incident wave energy in the form of circumferential waves which propagate rotating along the interface between the object and the embedding medium. Circumferential waves include surface Rayleigh-type waves (propagating mostly in the embedding medium), Stoneley waves (propagating mostly in the fluid, if present), and Frantz waves (body waves trapped in the object because of its curvature). Strong impedance contrast ensures small radiation loss for circumferential waves and they slowly decay in amplitude while rotating inside/around the object. Some circumferential waves exist in the high-velocity objects but their amplitudes decay very fast because of strong radiation in outer medium. Most of the secondary (multiply reflected from an object's boundaries or multiply circled around the object) resonant-scattered energy radiates in the embedding medium as shear waves. The possibility of neglecting P- waves in late scattering arrivals simplifies imaging as is demonstrated for the field and modeled data of the example. Resonant emission phenomenon provides an effective tool for active monitoring for a number of applications such as tunnel detection

  16. Community Seismic Network (CSN)

    NASA Astrophysics Data System (ADS)

    Clayton, R. W.; Heaton, T. H.; Kohler, M. D.; Cheng, M.; Guy, R.; Chandy, M.; Krause, A.; Bunn, J.; Olson, M.; Faulkner, M.

    2011-12-01

    The CSN is a network of low-cost accelerometers deployed in the Pasadena, CA region. It is a prototype network with the goal of demonstrating the importance of dense measurements in determining the rapid lateral variations in ground motion due to earthquakes. The main product of the CSN is a map of peak ground produced within seconds of significant local earthquakes that can be used as a proxy for damage. Examples of this are shown using data from a temporary network in Long Beach, CA. Dense measurements in buildings are also being used to determine the state of health of structures. In addition to fixed sensors, portable sensors such as smart phones are also used in the network. The CSN has necessitated several changes in the standard design of a seismic network. The first is that the data collection and processing is done in the "cloud" (Google cloud in this case) for robustness and the ability to handle large impulsive loads (earthquakes). Second, the database is highly de-normalized (i.e. station locations are part of waveform and event-detection meta data) because of the mobile nature of the sensors. Third, since the sensors are hosted and/or owned by individuals, the privacy of the data is very important. The location of fixed sensors is displayed on maps as sensor counts in block-wide cells, and mobile sensors are shown in a similar way, with the additional requirement to inhibit tracking that at least two must be present in a particular cell before any are shown. The raw waveform data are only released to users outside of the network after a felt earthquake.

  17. Seismicity of southern Lake Tanganyika

    NASA Astrophysics Data System (ADS)

    Lavayssiere, A.; Gallacher, R. J.; Keir, D.; Ebinger, C. J.; Drooff, C.; Khalfan, M.; Bull, J. M.

    2015-12-01

    Global seismic networks document frequent and unusually deep earthquakes in East African rift sectors lacking central volcanoes. The deep seismicity means that we can use earthquakes to probe the geometry and kinematics of fault systems throughout the crust, and to understand the distribution of strain between large offset border fault systems and intrabasinal faults. The southern Tanganyika rift zone has the highest seismicity rate within East Africa during the period 1973-present, yet earlier temporary seismometer networks have been too sparse in space and time to relocate earthquakes with location and depth errors of < 5-10 km. We address this issue by recording seismicity of southern Lake Tanganyika since June 2014 using a network at 12 broadband seismic stations. The distribution of earthquakes shows that deformation primarily occurs on large offset border faults beneath the lake. Subsidiary earthquake activity occurs along the subparrallel Rukwa graben, and beneath the NE-SW striking Mweru rift. The distribution of earthquakes suggests the southern end of lake Tanganyika is characterized by a network of intersecting NNW and NE striking faults. The depths of earthquakes are distributed throughout the crust, consistent with the relatively strong lithosphere.

  18. Seismic assessment of buried pipelines

    SciTech Connect

    Al-Chaar, G.; Brady, P.; Fernandez, G.

    1995-12-31

    A structure and its lifelines are closely linked because the disruption of lifeline systems will obstruct emergency service functions that are vitally needed after an earthquake. As an example of the criticality of these systems, the Association of Bay Area Government (ABAG) recorded thousands of leaks in pipelines that resulted in more than twenty million gallons of hazardous materials being released in several recorded earthquakes. The cost of cleaning the spills from these materials was very high. This information supports the development of seismic protection of lifeline systems. The US Army Corps of Engineers Construction Engineering Research Laboratories (USACERL) has, among its missions, the responsibility to develop seismic vulnerability assessment procedures for military installations. Within this mission, a preliminary research program to assess the seismic vulnerability of buried pipeline systems on military installations was initiated. Phase 1 of this research project resulted in two major studies. In the first, evaluating current procedures to seismically design or evaluate existing lifeline systems, the authors found several significant aspects that deserve special consideration and need to be addressed in future research. The second was focused on identifying parameters related to buried pipeline system vulnerability and developing a generalized analytical method to relate these parameters to the seismic vulnerability assessment of existing pipeline systems.

  19. A fuzzy multi-objective linear programming approach for integrated sheep farming and wildlife in land management decisions: a case study in the Patagonian rangelands

    NASA Astrophysics Data System (ADS)

    Metternicht, Graciela; Blanco, Paula; del Valle, Hector; Laterra, Pedro; Hardtke, Leonardo; Bouza, Pablo

    2015-04-01

    Wildlife is part of the Patagonian rangelands sheep farming environment, with the potential of providing extra revenue to livestock owners. As sheep farming became less profitable, farmers and ranchers could focus on sustainable wildlife harvesting. It has been argued that sustainable wildlife harvesting is ecologically one of the most rational forms of land use because of its potential to provide multiple products of high value, while reducing pressure on ecosystems. The guanaco (Lama guanicoe) is the most conspicuous wild ungulate of Patagonia. Guanaco ?bre, meat, pelts and hides are economically valuable and have the potential to be used within the present Patagonian context of production systems. Guanaco populations in South America, including Patagonia, have experienced a sustained decline. Causes for this decline are related to habitat alteration, competition for forage with sheep, and lack of reasonable management plans to develop livelihoods for ranchers. In this study we propose an approach to explicitly determinate optimal stocking rates based on trade-offs between guanaco density and livestock grazing intensity on rangelands. The focus of our research is on finding optimal sheep stocking rates at paddock level, to ensure the highest production outputs while: a) meeting requirements of sustainable conservation of guanacos over their minimum viable population; b) maximizing soil carbon sequestration, and c) minimizing soil erosion. In this way, determination of optimal stocking rate in rangelands becomes a multi-objective optimization problem that can be addressed using a Fuzzy Multi-Objective Linear Programming (MOLP) approach. Basically, this approach converts multi-objective problems into single-objective optimizations, by introducing a set of objective weights. Objectives are represented using fuzzy set theory and fuzzy memberships, enabling each objective function to adopt a value between 0 and 1. Each objective function indicates the satisfaction of

  20. SEG Advances in Rotational Seismic Measurements

    SciTech Connect

    Pierson, Robert; Laughlin, Darren; Brune, Bob

    2016-10-17

    Significant advancements in the development of sensors to enable rotational seismic measurements have been achieved. Prototypes are available now to support experiments that help validate the utility of rotational seismic measurements.

  1. Annual Hanford seismic report -- fiscal year 1996

    SciTech Connect

    Hartshorn, D.C.; Reidel, S.P.

    1996-12-01

    Seismic monitoring (SM) at the Hanford Site was established in 1969 by the US Geological Survey (USGS) under a contract with the US Atomic Energy Commission. Since 1980, the program has been managed by several contractors under the US Department of Energy (USDOE). Effective October 1, 1996, the Seismic Monitoring workscope, personnel, and associated contracts were transferred to the USDOE Pacific Northwest National Laboratory (PNNL). SM is tasked to provide an uninterrupted collection and archives of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) located on and encircling the Hanford Site. SM is also tasked to locate and identify sources of seismic activity and monitor changes in the historical pattern of seismic activity at the Hanford Site. The data compiled are used by SM, Waste Management, and engineering activities at the Hanford Site to evaluate seismic hazards and seismic design for the Site.

  2. Calibration of Seismic Attributes for Reservoir Characterization

    SciTech Connect

    Pennington, Wayne D.

    2002-05-29

    This project is intended to enhance the ability to use seismic data for the determination of rock and fluid properties through an improved understanding of the physics underlying the relationships between seismic attributes and formation.

  3. Seismicity of the Adriatic microplate

    USGS Publications Warehouse

    Console, R.; Di, Giovambattista R.; Favali, P.; Presgrave, B.W.; Smriglio, G.

    1993-01-01

    The Adriatic microplate was previously considered to be a unique block, tectonically active only along its margins. The seismic sequences that took place in the basin from 1986 to 1990 give new information about the geodynamics of this area. Three subsets of well recorded events were relocated by the joint hypocentre determination technique. On the whole, this seismic activity was concentrated in a belt crossing the southern Adriatic sea around latitude 42??, in connection with regional E-W fault systems. Some features of this seismicity, similar to those observed in other well known active margins of the Adriatic plate, support a model of a southern Adriatic lithospheric block, detached from the Northern one. Other geophysical information provides evidence of a transitional zone at the same latitude. ?? 1993.

  4. The Apollo passive seismic experiment

    NASA Technical Reports Server (NTRS)

    Latham, G. V.; Dorman, H. J.; Horvath, P.; Ibrahim, A. K.; Koyama, J.; Nakamura, Y.

    1979-01-01

    The completed data set obtained from the 4-station Apollo seismic network includes signals from approximately 11,800 events of various types. Four data sets for use by other investigators, through the NSSDC, are in preparation. Some refinement of the lunar model based on seismic data can be expected, but its gross features remain as presented two years ago. The existence of a small, molten core remains dependent upon the analysis of signals from a single, far-side impact. Analysis of secondary arrivals from other sources may eventually resolve this issue, as well as continued refinement of the magnetic field measurements. Evidence of considerable lateral heterogeneity within the moon continues to build. The mystery of the much meteoroid flux estimate derived from lunar seismic measurements, as compared with earth-based estimates, remains; although, significant correlations between terrestrial and lunar observations are beginning to emerge.

  5. Land-ocean gradient in haline stratification and its effects on plankton dynamics and trophic carbon fluxes in Chilean Patagonian fjords (47-50°S)

    NASA Astrophysics Data System (ADS)

    González, H. E.; Castro, L. R.; Daneri, G.; Iriarte, J. L.; Silva, N.; Tapia, F.; Teca, E.; Vargas, C. A.

    2013-12-01

    Patagonian fjord systems, and in particular the fjords and channels associated with the Baker/Pascua Rivers, are currently under conspicuous natural and anthropogenic perturbations. These systems display very high variability, where limnetic and oceanic features overlap generating strong vertical and horizontal physicochemical gradients. The CIMAR 14-Fiordos cruise was conducted in the Chilean fjords located between 47° and 50°S during the spring (October-November) of 2008. The main objectives were to study vertical and horizontal gradients in physical, chemical and biological characteristics of the water column, and to assess plankton dynamics and trophic carbon fluxes in the fjords and channels of central-south Patagonia. The water column was strongly stratified, with a pycnocline at ca. 20 m depth separating a surface layer of silicic acid-rich freshwater discharged by rivers, from the underlying nitrate- and orthophosphate-rich Subantarctic waters. The outflows from the Baker and Pascua Rivers, which range annually between 500 and 1500 m3 s-1, generate the strong land-ocean gradient in salinity (1-32 psu) and inorganic nutrient concentrations (2-8 and 2-24 μM in nitrate and silicic-acid, respectively) we observed along the Baker Fjord. The POC:chl-a ratio fluctuated from 1087 near the fjord’s head to 175 at its oceanic end in the Penas Gulf. This change was mainly due to an increase in diatom dominance and a concurrent decrease in allochthonous POC towards the ocean. Depth-integrated net primary production (NPP) and bacterial secondary production (BSP) fluctuated between 49 and 1215 and 36 and 150 mg C m-2 d-1, respectively, with higher rates in oceanic waters. At a time series station located close to the Baker River mouth, the average NPP was lower (average 360 mg C m-2 d-1) than at more oceanic stations (average 1063 mg C m-2 d-1), and numerically dominated (45%) by the picoplankton (<2 μm) and nanoplankton (2-20 μm) size fractions. The high average

  6. Recent Advances in Seismic Oceanography

    NASA Astrophysics Data System (ADS)

    Papenberg, Cord; Klaeschen, Dirk; Krahmann, Gerd; Hobbs, Richard; Vsemirnova, Ekaterina

    2010-05-01

    Recently seismic reflection methods have been successfully applied to oceanographic issues. Acoustic imaging of internal oceanic structure (‘‘seismic oceanography'') is providing views of thermohaline finestructure with the potential to provide quantitative information on such processes as internal waves, eddy dynamics, and turbulent dissipation. Here we present sound-speed data und subsequently temperature and salinity images inverted from combined seismic and hydrographic observations at unprecedented resolution. However, unlike the solid earth, where the boundaries between two rock masses may be sharp and a description by the impedance above and below the boundary suffice, the boundaries in the ocean are affected by diffusion processes, so that the reflection coefficient needs to be described by continuous profiles of the vertical impedance gradient or the underlying properties sound speed and density. These quantities can be related to temperature and salinity of the water. For this we use a T-S(z) relationship (temperature-salinity) derived from CTD observations and the equation of state for seawater to simultaneously calculate temperature and salinity for the whole profile in an iterative process. The inverted temperature and salinity maps thereby allow us to identify different water mass bodies at intermediate scales. Furthermore, we use these accurate sound-speed models to derive reflector movement velocities of water mass bodies as an additional property from seismic reflection data. For migration of seismic data over the solid Earth we know the geometry and need to find the optimum sound speed model, here we reverse this procedure, given the sound speed model we can compute the optimum geometry for a dynamic fluid and hence its motion. The movement velocity gives a dynamic property to the instant seismic reflector image and may have great potential to study the temporal dynamics of the water structure.

  7. Historical Seismicity of Central Panama

    NASA Astrophysics Data System (ADS)

    Camacho, E.

    2013-05-01

    Central Panama lies in the Panama microplate, neighboring seismically active regions of Costa Rica and Colombia. This region, crossed by the Panama Canal, concentrates most of the population and economic activity of the Republic of Panama. Instrumental observation of earthquakes in Panama began on 1882 by the Compagnie Universelle du Canal Interocéanique de Panama and continued from 1904 to 1977 by the Panama Canal Company. From October 1997 to March 1998 the USGS deployed a temporary digital seismic network. Since 2003 this region is monitored by a digital seismic network operated by the Panama Canal Authority and I complemented by the broad band stations of the University of Panama seismic network. The seismicity in this region is very diffuse and the few events which are recorded have magnitudes less than 3.0. Historical archives and antique newspapers from Spain, Colombia, Panama and the United Sates have been searched looking for historical earthquake information which could provide a better estimate of the seismicity in this region. We find that Panama City has been shaken by two destructive earthquakes in historical times. One by a local fault (i.e. Pedro Miguel fault) on May 2, 1621 (I=Vlll MM), and a subduction event from the North Panama Deformed Belt (NPDB) on September 7, 1882 (I=Vll MM). To test these findings two earthquakes scenarios were generated, using SELENA, for Panama City Old Quarter. Panama City was rebuilt on January 21, 1673, on a rocky point facing the Pacific Ocean after the sack by pirate Morgan on January 28, 1671. The pattern of damage to calicanto (unreinforced colonial masonry) and wood structures for a crustal local event are higher than those for an event from the NPDB and seem to confirm that the city has not been shaken by a major local event since May 2, 1621 and a subduction event since September 7, 1882

  8. Time-Dependent Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Julian, B. R.

    2008-12-01

    Temporal changes in seismic wave speeds in the Earth's crust have been measured at several locations, notably The Geysers geothermal area in California, in studies that used three-dimensional seismic tomography. These studies have used conventional tomography methods to invert multiple seismic-wave arrival time data sets independently and assumed that any differences in the derived structures reflect real temporal variations. Such an assumption is dangerous because the results of repeated tomography experiments would differ even if the structure did not change, simply because of variation in the seismic ray distribution caused by the natural variation in earthquake locations. This problem can be severe when changes in the seismicity distribution are systematic, as, for example, at the onset of an aftershock sequence. The sudden change in the ray distribution can produce artifacts that mimic changes in the seismic wave speeds at the time of a large earthquake. Even if the source locations did not change (if only explosion data were used, for example), derived structures would inevitably differ because of observational errors. A better approach to determining what temporal changes are truly required by the data is to invert multiple data sets simultaneously, imposing constraints to minimize differences between the models for different epochs. This problem is similar to that of seeking models similar to some a priori initial assumption, and a method similar to "damped least squares" can solve it. The order of the system of normal equations for inverting data from two epochs is twice as large as that for a single epoch, and solving it by standard methods requires eight times the computational labor. We present an algorithm for reducing this factor to two, so that inverting multiple epochs simultaneously is comparable in difficulty to inverting them independently, and illustrate its performance using synthetic arrival times and observed data from several areas in

  9. USGS National Seismic Hazard Maps

    USGS Publications Warehouse

    Frankel, A.D.; Mueller, C.S.; Barnhard, T.P.; Leyendecker, E.V.; Wesson, R.L.; Harmsen, S.C.; Klein, F.W.; Perkins, D.M.; Dickman, N.C.; Hanson, S.L.; Hopper, M.G.

    2000-01-01

    The U.S. Geological Survey (USGS) recently completed new probabilistic seismic hazard maps for the United States, including Alaska and Hawaii. These hazard maps form the basis of the probabilistic component of the design maps used in the 1997 edition of the NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures, prepared by the Building Seismic Safety Council arid published by FEMA. The hazard maps depict peak horizontal ground acceleration and spectral response at 0.2, 0.3, and 1.0 sec periods, with 10%, 5%, and 2% probabilities of exceedance in 50 years, corresponding to return times of about 500, 1000, and 2500 years, respectively. In this paper we outline the methodology used to construct the hazard maps. There are three basic components to the maps. First, we use spatially smoothed historic seismicity as one portion of the hazard calculation. In this model, we apply the general observation that moderate and large earthquakes tend to occur near areas of previous small or moderate events, with some notable exceptions. Second, we consider large background source zones based on broad geologic criteria to quantify hazard in areas with little or no historic seismicity, but with the potential for generating large events. Third, we include the hazard from specific fault sources. We use about 450 faults in the western United States (WUS) and derive recurrence times from either geologic slip rates or the dating of pre-historic earthquakes from trenching of faults or other paleoseismic methods. Recurrence estimates for large earthquakes in New Madrid and Charleston, South Carolina, were taken from recent paleoliquefaction studies. We used logic trees to incorporate different seismicity models, fault recurrence models, Cascadia great earthquake scenarios, and ground-motion attenuation relations. We present disaggregation plots showing the contribution to hazard at four cities from potential earthquakes with various magnitudes and

  10. Advanced Seismic While Drilling System

    SciTech Connect

    Robert Radtke; John Fontenot; David Glowka; Robert Stokes; Jeffery Sutherland; Ron Evans; Jim Musser

    2008-06-30

    A breakthrough has been discovered for controlling seismic sources to generate selectable low frequencies. Conventional seismic sources, including sparkers, rotary mechanical, hydraulic, air guns, and explosives, by their very nature produce high-frequencies. This is counter to the need for long signal transmission through rock. The patent pending SeismicPULSER{trademark} methodology has been developed for controlling otherwise high-frequency seismic sources to generate selectable low-frequency peak spectra applicable to many seismic applications. Specifically, we have demonstrated the application of a low-frequency sparker source which can be incorporated into a drill bit for Drill Bit Seismic While Drilling (SWD). To create the methodology of a controllable low-frequency sparker seismic source, it was necessary to learn how to maximize sparker efficiencies to couple to, and transmit through, rock with the study of sparker designs and mechanisms for (a) coupling the sparker-generated gas bubble expansion and contraction to the rock, (b) the effects of fluid properties and dynamics, (c) linear and non-linear acoustics, and (d) imparted force directionality. After extensive seismic modeling, the design of high-efficiency sparkers, laboratory high frequency sparker testing, and field tests were performed at the University of Texas Devine seismic test site. The conclusion of the field test was that extremely high power levels would be required to have the range required for deep, 15,000+ ft, high-temperature, high-pressure (HTHP) wells. Thereafter, more modeling and laboratory testing led to the discovery of a method to control a sparker that could generate low frequencies required for deep wells. The low frequency sparker was successfully tested at the Department of Energy Rocky Mountain Oilfield Test Center (DOE RMOTC) field test site in Casper, Wyoming. An 8-in diameter by 26-ft long SeismicPULSER{trademark} drill string tool was designed and manufactured by TII

  11. Seismic Holography of Solar Activity

    NASA Technical Reports Server (NTRS)

    Lindsey, Charles

    2000-01-01

    The basic goal of the project was to extend holographic seismic imaging techniques developed under a previous NASA contract, and to incorporate phase diagnostics. Phase-sensitive imaging gives us a powerful probe of local thermal and Doppler perturbations in active region subphotospheres, allowing us to map thermal structure and flows associated with "acoustic moats" and "acoustic glories". These remarkable features were discovered during our work, by applying simple acoustic power holography to active regions. Included in the original project statement was an effort to obtain the first seismic images of active regions on the Sun's far surface.

  12. Seismic assessment for offshore pipelines

    SciTech Connect

    Bruschi, R.; Gudmestad, O.T.; Blaker, F.; Nadim, F.

    1995-12-31

    An international consensus on seismic design criteria for onshore pipelines has been established during the last thirty years. The need to assess seismic design for offshore pipelines has not been similarly recognized. In this paper, the geotechnical hazard for a pipeline routed across steep slopes and irregular terrains affected by earthquakes, is discussed. The integrity of both natural and artificial load bearing supports is assessed.d The response of the pipeline to direct excitation from soil or through discontinuous, sparsely distributed natural or artificial supports, is commented.

  13. Seismic Hazard Study for Utah.

    DTIC Science & Technology

    1982-10-26

    Smith, R. I. , and Sbar, M. L. (1974) Contemporary tectonics and seismicity of the Western Inited States with emphasis on the inter-mountain seismic belt...thc tilt! a lo P1 itt-au onl thn cas. he di.stinct tectonics of each of these provinces is z-~ nfi ntill th, -eisllmit r(tionailii ation Of tueL area...Vton, G. 11. (1979) A plate tectonic model for late Cenozoic spreading in the Western I niteth States, in Rio Girande Rift: Tectonics and Magmatism

  14. Seismic event near Jarocin (Poland)

    NASA Astrophysics Data System (ADS)

    Lizurek, Grzegorz; Plesiewicz, Beata; Wiejacz, Paweł; Wiszniowski, Jan; Trojanowski, Jacek

    2013-02-01

    The earthquake of magnitude M L = 3:8 (EMSC) took place on Friday, 6 January 2012, north-east of the town of Jarocin in Wielkopolska Region, Poland. The only historical information about past earthquakes in the region was found in the diary from 1824; apart of it, there was a seismic event noticed in the vicinity of Wielkopolska in 1606 (Pagaczewski 1982). The scope of this paper is to describe the 6 January 2012 event in view of instrumental seismology, macroseismic data analysis and known tectonics of the region, which should be useful in future seismic hazard analysis of Poland.

  15. Community Seismic Network (CSN)

    NASA Astrophysics Data System (ADS)

    Clayton, R. W.; Heaton, T. H.; Kohler, M. D.; Cheng, M.; Guy, R.; Chandy, M.; Krause, A.; Bunn, J.; Olson, M.; Faulkner, M.; Liu, A.; Strand, L.

    2012-12-01

    We report on developments in sensor connectivity, architecture, and data fusion algorithms executed in Cloud computing systems in the Community Seismic Network (CSN), a network of low-cost sensors housed in homes and offices by volunteers in the Pasadena, CA area. The network has over 200 sensors continuously reporting anomalies in local acceleration through the Internet to a Cloud computing service (the Google App Engine) that continually fuses sensor data to rapidly detect shaking from earthquakes. The Cloud computing system consists of data centers geographically distributed across the continent and is likely to be resilient even during earthquakes and other local disasters. The region of Southern California is partitioned in a multi-grid style into sets of telescoping cells called geocells. Data streams from sensors within a geocell are fused to detect anomalous shaking across the geocell. Temporal spatial patterns across geocells are used to detect anomalies across regions. The challenge is to detect earthquakes rapidly with an extremely low false positive rate. We report on two data fusion algorithms, one that tessellates the surface so as to fuse data from a large region around Pasadena and the other, which uses a standard tessellation of equal-sized cells. Since September 2011, the network has successfully detected earthquakes of magnitude 2.5 or higher within 40 Km of Pasadena. In addition to the standard USB device, which connects to the host's computer, we have developed a stand-alone sensor that directly connects to the internet via Ethernet or wifi. This bypasses security concerns that some companies have with the USB-connected devices, and allows for 24/7 monitoring at sites that would otherwise shut down their computers after working hours. In buildings we use the sensors to model the behavior of the structures during weak events in order to understand how they will perform during strong events. Visualization models of instrumented buildings ranging

  16. 7 CFR 1792.104 - Seismic acknowledgments.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 12 2014-01-01 2013-01-01 true Seismic acknowledgments. 1792.104 Section 1792.104... AGRICULTURE (CONTINUED) COMPLIANCE WITH OTHER FEDERAL STATUTES, REGULATIONS, AND EXECUTIVE ORDERS Seismic Safety of Federally Assisted New Building Construction § 1792.104 Seismic acknowledgments. For...

  17. 7 CFR 1792.104 - Seismic acknowledgments.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 12 2012-01-01 2012-01-01 false Seismic acknowledgments. 1792.104 Section 1792.104... AGRICULTURE (CONTINUED) COMPLIANCE WITH OTHER FEDERAL STATUTES, REGULATIONS, AND EXECUTIVE ORDERS Seismic Safety of Federally Assisted New Building Construction § 1792.104 Seismic acknowledgments. For...

  18. 7 CFR 1792.104 - Seismic acknowledgments.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 12 2013-01-01 2013-01-01 false Seismic acknowledgments. 1792.104 Section 1792.104... AGRICULTURE (CONTINUED) COMPLIANCE WITH OTHER FEDERAL STATUTES, REGULATIONS, AND EXECUTIVE ORDERS Seismic Safety of Federally Assisted New Building Construction § 1792.104 Seismic acknowledgments. For...

  19. Seismic Mitigation Strategies for Existing School Buildings.

    ERIC Educational Resources Information Center

    Hattis, D. B.; Krimgold, F.; Green, M.

    California provides the paradigm for lessening devastating earthquake damage in U.S. buildings. This document examines specific examples of the seismic mitigation process, a process showing that seismic retrofit in existing schools in other parts of the country are possible and could lead to more general seismic rehabilitation in other buildings.…

  20. Simplified seismic performance assessment and implications for seismic design

    NASA Astrophysics Data System (ADS)

    Sullivan, Timothy J.; Welch, David P.; Calvi, Gian Michele

    2014-08-01

    The last decade or so has seen the development of refined performance-based earthquake engineering (PBEE) approaches that now provide a framework for estimation of a range of important decision variables, such as repair costs, repair time and number of casualties. This paper reviews current tools for PBEE, including the PACT software, and examines the possibility of extending the innovative displacement-based assessment approach as a simplified structural analysis option for performance assessment. Details of the displacement-based s+eismic assessment method are reviewed and a simple means of quickly assessing multiple hazard levels is proposed. Furthermore, proposals for a simple definition of collapse fragility and relations between equivalent single-degree-of-freedom characteristics and multi-degree-of-freedom story drift and floor acceleration demands are discussed, highlighting needs for future research. To illustrate the potential of the methodology, performance measures obtained from the simplified method are compared with those computed using the results of incremental dynamic analyses within the PEER performance-based earthquake engineering framework, applied to a benchmark building. The comparison illustrates that the simplified method could be a very effective conceptual seismic design tool. The advantages and disadvantages of the simplified approach are discussed and potential implications of advanced seismic performance assessments for conceptual seismic design are highlighted through examination of different case study scenarios including different structural configurations.

  1. On the distribution of seismic reflection coefficients and seismic amplitudes

    SciTech Connect

    Painter, S.; Paterson, L.; Beresford, G.

    1995-07-01

    Reflection coefficient sequences from 14 wells in Australia have a statistical character consistent with a non-Gaussian scaling noise model based on the Levy-stable family of probability distributions. Experimental histograms of reflection coefficients are accurately approximated by symmetric Levy-stable probability density functions with Levy index between 0.99 and 1.43. These distributions have the same canonical role in mathematical statistics as the Gaussian distribution, but they have slowly decaying tails and infinite moments. The distribution of reflection coefficients is independent of the spatial scale (statistically self-similar), and the reflection coefficient sequences have long-range dependence. These results suggest that the logarithm of seismic impedance can be modeled accurately using fractional Levy motion, which is a generalization of fractional Brownian motion. Synthetic seismograms produced from the authors` model for the reflection coefficients also have Levy-stable distributions. These isolations include transmission losses, the effects of reverberations, and the loss of resolution caused by band-limited wavelets, and suggest that actual seismic amplitudes with sufficient signal-to-noise ratio should also have a Levy-stable distribution. This prediction is verified using post-stack seismic data acquired in the Timor Sea and in the continental USA. However, prestack seismic amplitudes from the Timor Sea are nearly Gaussian. They attribute the difference between prestack and poststack data to the high level of measurement noise in the prestack data.

  2. Expanding Conventional Seismic Stratigrphy into the Multicomponent Seismic Domain

    SciTech Connect

    Innocent Aluka

    2008-08-31

    Multicomponent seismic data are composed of three independent vector-based seismic wave modes. These wave modes are, compressional mode (P), and shear modes SV and SH. The three modes are generated using three orthogonal source-displacement vectors and then recorded using three orthogonal vector sensors. The components travel through the earth at differing velocities and directions. The velocities of SH and SV as they travel through the subsurface differ by only a few percent, but the velocities of SV and SH (Vs) are appreciably lower than the P-wave velocity (Vp). The velocity ratio Vp/Vs varies by an order of magnitude in the earth from a value of 15 to 1.5 depending on the degree of sedimentary lithification. The data used in this study were acquired by nine-component (9C) vertical seismic profile (VSP), using three orthogonal vector sources. The 9C vertical seismic profile is capable of generating P-wave mode and the fundamental S-wave mode (SH-SH and SV-SV) directly at the source station and permits the basic components of elastic wavefield (P, SH-SH and SV-SV) to be separated from one another for the purposes of imaging. Analysis and interpretations of data from the study area show that incident full-elastic seismic wavefield is capable of reflecting four different wave modes, P, SH , SV and C which can be utilized to fully understand the architecture and heterogeneities of geologic sequences. The conventional seismic stratigraphy utilizes only reflected P-wave modes. The notation SH mode is the same as SH-SH; SV mode means SV-SV and C mode which is a converted shear wave is a special SV mode and is the same as P-SV. These four wave modes image unique geologic stratigraphy and facies and at the same time reflect independent stratal surfaces because of the unique orientation of their particle-displacement vectors. As a result of the distinct orientation of individual mode's particle-displacement vector, one mode may react to a critical subsurface sequence more

  3. Andean evolution of the Aluminé fold and thrust belt, Northern Patagonian Andes (38°30‧-40°30‧S)

    NASA Astrophysics Data System (ADS)

    García Morabito, Ezequiel; Ramos, Víctor A.

    2012-10-01

    The Aluminé fold and thrust belt between 38°30' and 40°30'S is the result of two periods of progression of deformation toward the foreland. The chronology of deformation and its relationship with magmatism through time show spatially and temporally separated magmatic events closely linked to distinct deformational stages. Data presented here confirms a Late Cretaceous mountain-building phase that coexisted in space and time with an eastward arc-migration. During this stage, a belt of deformation expanded through the foreland where it produced the Southern Neuquen Precordillera. This eastern independent mountain grew separately from the main Andean axis through a combination of inversion of the old rift systems and interaction with a pre-Andean belt which acted as a foreland obstacle. On the basis of tectonostratigraphic controls we define the last Andean contractional phase between the Late Miocene and the Pliocene. This event induced the reactivation of both sectors of the fold and thrust belt with minor propagation toward the foreland, leading to the uplift of the Patagonian Andes and reshaping the Southern Neuquén Precordillera. Both intervals of shortening are separated by a period of localized extension that resulted in the development of the Collón Cura basin within this Andean segment. Here, large thicknesses of volcanosedimentary sequences accumulated contemporaneously with the extensional activity between the earliest Oligocene and the Early Miocene.

  4. Thaulin-1: The first antimicrobial peptide isolated from the skin of a Patagonian frog Pleurodema thaul (Anura: Leptodactylidae: Leiuperinae) with activity against Escherichia coli.

    PubMed

    Marani, Mariela M; Perez, Luis O; de Araujo, Alyne Rodrigues; Plácido, Alexandra; Sousa, Carla F; Quelemes, Patrick Veras; Oliveira, Mayara; Gomes-Alves, Ana G; Pueta, Mariana; Gameiro, Paula; Tomás, Ana M; Delerue-Matos, Cristina; Eaton, Peter; Camperi, Silvia A; Basso, Néstor G; de Souza de Almeida Leite, Jose Roberto

    2017-03-20

    Patagonia's biodiversity has been explored from many points of view, however, skin secretions of native amphibians have not been evaluated for antimicrobial peptide research until now. In this sense, Pleurodema thaul is the first amphibian specie to be studied from this large region of South America. Analysis of cDNA-encoding peptide in skin samples allowed identification of four new antimicrobial peptides. The predicted mature peptides were synthesized and all of them showed weak or null antimicrobial activity against Klebsiella pneumoniae, Staphylococcus aureus and Escherichia coli with the exception of thaulin-1, a cationic 26-residue linear, amphipathic, Gly- and Leu-rich peptide with moderate antimicrobial activity against E. coli (MIC of 24.7μM). AFM and SPR studies suggested a preferential interaction between these peptides and bacterial membranes. Cytotoxicity assays showed that thaulin peptides had minimal effects at MIC concentrations towards human and animal cells. These are the first peptides described for amphibians of the Pleurodema genus. These findings highlight the potential of the Patagonian region's unexplored biodiversity as a source for new molecule discovery. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Geochemistry of the Mamil Choique granitoids at Rio Chico, Río Negro, Argentina: Late Paleozoic crustal melting in the North Patagonian Massif

    NASA Astrophysics Data System (ADS)

    López de Luchi, Mónica G.; Cerredo, María Elena

    2008-06-01

    The Mamil Choique granitoids located in the SW border of the North Patagonian Massif consist of three peraluminous units: the banded Huenchuquil tonalites and granodiorites (HTG) and the Cerro Mojón biotite-muscovite monzogranites (CMG), which are intruded by the Nahuelfil monzogranites (NG). According to their major and trace element relations, as well as a comparison with experimentally produced melts, HTG are compatible with partial melting of mafic source rocks at variable H 2O contents; residual garnet is suggested by HREE depletion that indicates a minimum P of 9-10 kbar during melting. The CMG would have formed from partial melting of supracrustal fertile lithologies (biotite-bearing) in the presence of H 2O-bearing volatile phase that resulted in Sr-rich, moderately depressed HREE melts, likely produced within the garnet stability field (7-10 kbar). The intrusive NG display distinct geochemical signatures (low Sr, no HREE depletion) and general major element ratios akin to the experimentally produced melt at low P (≈5 kbar). Regional constraints indicate that coeval HTG and CMG emplacement took place along a decompressing path slightly postdating the climax of regional metamorphism in the host Cushamen Formation. Later NG intrusion would have occurred at upper crustal levels.

  6. Environmental conditions, early life stages distributions and larval feeding of patagonian sprat Sprattusfuegensis and common sardine Strangomerabentincki in fjords and channels of the northern Chilean patagonia

    NASA Astrophysics Data System (ADS)

    Contreras, Tabit; Castro, Leonardo R.; Montecinos, Sandra; Gonzalez, Humberto E.; Soto, Samuel; Muñoz, Maria I.; Palma, Sergio

    2014-12-01

    We assessed ontogenetic changes in distribution and feeding of the Patagonian sprat Sprattus fuegensis and common sardine Strangomera bentincki, and their association with environmental characteristics (hydrography, larval food, gelatinous zooplankton predators), and actual feeding from inshore to offshore areas of the Chilean Patagonia. During the springs of 2007 and 2008, S. bentincki egg and larvae were present north of the Taitao Peninsula (47°S) and S. fuegensis was found to the south of the peninsula. Along the inshore-offshore axis, distributions also differed: while eggs and early larval stages of S. bentincki occurred inshore and seawards, larger larvae occurred mostly seawards. The opposite was observed in S. fuegensis. However, distributions of both species followed the same rule, determined by the size of their prey: eggs and early larval stages occurred in areas of higher abundance of small prey sizes, and larger larvae coincided with the highest abundances of larger prey sizes. No relationship was detected between potential gelatinous predators and the egg and larval distributions of both fish species. Mean ingested prey sizes in both species increased as larvae grew, while maintaining the capacity to feed on small sized items. This ontogenetic feeding pattern and the distributions linked to prey seem to be beneficial in order to take advantage of short term food pulses and to overcome the strong changes in environmental conditions east to west from fjords to open waters.

  7. Newly isolated Bacillus sp. G51 from Patagonian wool produces an enzyme combination suitable for felt-resist treatments of organic wool.

    PubMed

    Iglesias, Martín S; Sequeiros, Cynthia; García, Sebastián; Olivera, Nelda L

    2017-06-01

    Bacteria from Patagonian Merino wool were isolated to assess their wool-keratinolytic activity and potential for felt-resist treatments. Strains from Bacillus, Exiguobacterium, Deinococcus, and Micrococcus produced wool-degrading enzymes. Bacillus sp. G51 showed the highest wool-keratinolytic activity. LC-MS/MS analysis revealed that G51 secreted two serine proteases belonging to the peptidase family S8 (MEROPS) and a metalloprotease associated with Bacillolysin, along with other enzymes (γ-glutamyltranspeptidase and dihydrolipoyl dehydrogenases) that could be involved in reduction of keratin disulfide bonds. Optimum pH and temperature of G51 proteolytic activity were 9 and 60 °C, respectively. More than 80% of activity was retained in H2O2, Triton X-100, Tween 20, Lipocol OXO650, Teridol B, and β-mercaptoethanol. Treatment of wool top with G51 enzyme extract caused a decrease in wool felting tendency without significant weight loss (<1.5%). Sparse work has so far been performed to investigate suitable keratinases for the organic wool sector. This eco-friendly treatment based on a new enzyme combination produced by a wild bacterium has potential for meeting the demands of organic wool processing which bans the use of hazardous chemicals and genetic engineering.

  8. Silicic acid enrichment of subantarctic surface water from continental inputs along the Patagonian archipelago interior sea (41-56°S)

    NASA Astrophysics Data System (ADS)

    Torres, Rodrigo; Silva, Nelson; Reid, Brian; Frangopulos, Máximo

    2014-12-01

    We estimated Si∗, the surplus or deficit of orthosilicic acid (DSi) relative to nitrate available for diatom growth, in the Chilean Patagonian Archipelago Interior Sea (PAIS). Si∗ and salinity were negatively correlated in the PAIS because of the mixing of high nitrate, low DSi subantarctic surface water and high DSi, low nitrate continental freshwater runoff. Both the slope and the intercept of this relationship decreased from northern to southern Patagonia, which was likely a consequence of reduced DSi inputs from several overlapping hydrological, biological and geological drivers along this gradient. In general, lower freshwater DSi concentrations were expected below 46°S, and a lower total DSi load was expected from reduced runoff below 51°S. The north-south decreasing DSi concentration trend may be linked to dilutions from a higher proportion of runoff in latitudes with higher precipitation rates (45-53°S), the transition to more resistant granitic rocks and glacial melt-water from the Northern and Southern Patagonia Ice Fields (46-51°S) and a reduced density of volcanoes active during the Holocene (48-56°S). The intensification of a southward DSi deficit may be a forcing factor involved in the reported southward reductions in plankton biomass and a more frequent occurrence of non-diatom blooms in southern PAIS.

  9. Geochemistry of a Triassic dyke swarm in the North Patagonian Massif, Argentina. Implications for a postorogenic event of the Permian Gondwanide orogeny

    NASA Astrophysics Data System (ADS)

    González, Santiago N.; Greco, Gerson A.; González, Pablo D.; Sato, Ana M.; Llambías, Eduardo J.; Varela, Ricardo

    2016-10-01

    Permo-Triassic magmatism is widespread in the eastern North Patagonian Massif and has been related to the Gondwanide orogeny. Although a magmatic arc setting is widely accepted for the Permian plutonic rocks, the origin and geotectonic setting for the Triassic plutonic and volcanic rocks are still unknown. A NW-SE Triassic dyke swarm composed of andesites and latites with minor rhyolites was previously described in the Sierra Grande - Rincon de Paileman area. The dyke swarm was associated with extensional tectonics which was linked to a postorogenic process. In this paper we present new geochemical data of the rocks that form the swarm. Trachyandesites and rhyolites were separated based on their geochemical characteristics. Both groups may be considered originated from different sources. On the other hand, the content of incompatible elements (LILE and HFSE) indicates a strong relation between the swarm and an active continental margin. The samples also show a transitional signature between continental-arc and postcollisional or anorogenic settings. The new geochemical data on the dyke swarm support the idea of a magmatism that was linked to a postorogenic extensional tectonic regime related to a continental magmatic arc. Such an extension started in the Paleopacific margin of Pangea during the Anisian and might indicate the beginning of the Pangea break-up.

  10. Seismic maps foster landmark legislation

    USGS Publications Warehouse

    Borcherdt, Roger D.; Brown, Robert B.; Page, Robert A.; Wentworth, Carl M.; Hendley, James W.

    1995-01-01

    When a powerful earthquake strikes an urban region, damage concentrates not only near the quake's source. Damage can also occur many miles from the source in areas of soft ground. In recent years, scientists have developed ways to identify and map these areas of high seismic hazard. This advance has spurred pioneering legislation to reduce earthquake losses in areas of greatest hazard.

  11. Micromachined silicon seismic accelerometer development

    SciTech Connect

    Barron, C.C.; Fleming, J.G.; Montague, S.

    1996-08-01

    Batch-fabricated silicon seismic transducers could revolutionize the discipline of seismic monitoring by providing inexpensive, easily deployable sensor arrays. Our ultimate goal is to fabricate seismic sensors with sensitivity and noise performance comparable to short-period seismometers in common use. We expect several phases of development will be required to accomplish that level of performance. Traditional silicon micromachining techniques are not ideally suited to the simultaneous fabrication of a large proof mass and soft suspension, such as one needs to achieve the extreme sensitivities required for seismic measurements. We have therefore developed a novel {open_quotes}mold{close_quotes} micromachining technology that promises to make larger proof masses (in the 1-10 mg range) possible. We have successfully integrated this micromolding capability with our surface-micromachining process, which enables the formation of soft suspension springs. Our calculations indicate that devices made in this new integrated technology will resolve down to at least sub-{mu}G signals, and may even approach the 10{sup -10} G/{radical}Hz acceleration levels found in the low-earth-noise model.

  12. Seismicity of California's north coast

    USGS Publications Warehouse

    Bakun, W.H.

    2000-01-01

    At least three moment magnitude (M) 7 earthquakes occurred along California's north coast in the second half of the nineteenth century. The M 7.3 earthquake on 23 November 1873 occurred near the California-Oregon coast and likely was located on the Cascadia subduction zone or within the North American plate. The M 7.0 + earthquake on 9 May 1878 was located about 75 km offshore near the Mendocino fault. The surface-wave magnitude (M(s)) 7.0 earthquake on 16 April 1899 was located about 150 km offshore within the Gorda plate. There were at least three M 7 north-coast earthquakes in the 35 years before 1906, two M 7 earthquakes in the 20 years after 1906, no M 7 earthquakes from 1923 until 1980, and four M 7 earthquakes since 1980. The relative seismic quiescence after 1906 for M 7 earthquakes along California's north coast mimics the post-1906 seismic quiescence in the San Francisco Bay area for M 6 earthquakes. The post-1906 relative quiescence did not extend to lower magnitudes in either area. The 18 April 1906 earthquake apparently influenced the rate of occurrence of M 7 north-coast earthquakes as it apparently influenced the rate of M 6 earthquakes in the San Francisco Bay area. The relative seismic quiescence along the California north-coast region after 1906 should be taken into account when evaluating seismic hazards in northwest California.

  13. Boat with seismic gun jib

    SciTech Connect

    Bertrams, R. B.

    1984-11-06

    A ship is disclosed for seismic or geophysical exploration. The ship is provided with a pair of jibs which are supported between upper and lower decks for pivotal movement between a retracted position between the decks and an outwardly pivotted position extending laterally outward from the sides thereof. The jibs are each of a reinf

  14. Seismic exploration in Raton basin

    SciTech Connect

    Applegate, J.K.; Rose, P.R.

    1985-05-01

    Exploration in the Raton basin has delineated complex mountain-front structure in the asymmetric basin, and defined possible basin-centered gas. Exploration has included subsurface and surface geology, remote sensing, and seismic reflection. The Raton basin is a north-south-trending structural basin straddling the Colorado-New Mexico boundary. It is bounded on the west by the Sangre de Cristo Mountains, on the north and northeast by the Wet Mountains and Apishapa arch, and the Sierra Grande uplift on the south and southeast. The basin is asymmetric with transcurrent faulting and thrusting associated with the steeper western flank of the basin. Rocks range from Devonian-Mississippian overlying Precambrian basement to Miocene volcanics associated with the Spanish Peaks. Principal targets include the Entrada, Dakota, Codell, and Trinidad Sandstones and the Purgatoire and Raton Formations. Seismic data include explosive and Vibroseis data. Data quality is good in the basin center and is fair in the thrusted areas. Correlations are difficult from line to line. However, a strike line in the disturbed area would probably be more disrupted by out-of-the-plane reflections than the dip lines would be. Significant stratigraphic changes are seen in both the Trinidad and Dakota intervals. Integrated seismic and geological studies are keys to exploration in the basin. Subsequent work will rely heavily on improved seismic information.

  15. New Zealand Seismic Risk Model

    NASA Astrophysics Data System (ADS)

    Molas, G.; Aslani, H.; Bryngelson, J.; Khan, Z.

    2006-12-01

    A seismic risk model for New Zealand has been developed to assisted insurers and reinsurers in assessing their financial risk posed by earthquakes. This presentation summarizes the methodology and data within the model and includes a discussion of the key results from the hazard and risk perspectives. The earthquake, risk-model framework has four components. First, the stochastic event set is determined, as well as its associated event probabilities. A ground-motion model including geotechnical data is added to complete the seismic hazard model. To determine risk, regional building vulnerability curves and a financial model are incorporated. An insurer property exposure database was developed to determine the insured seismic risk in these countries. Using this model, examination of resulting hazard maps (200, 475, 1000 and 2500 years) and of city-level, hazard-curves gives insight to the key drivers of risk across the region. Hazard de-aggregation allow for examination of key drivers of risk in terms of seismic sources, event magnitude and events types. Examination of loss costs for residential and commercial (short and mid-rise) structures gives insight into the risk perspective for these various lines of business. Finally, incorporation of the insurer property exposure allows for an examination of the insured risk across the region and between exposure concentrations including Wellington, Auckland and Christchurch.

  16. Seismic maps foster landmark legislation

    USGS Publications Warehouse

    Borcherdt, Roger D.; Brown, Robert B.; Page, Robert A.; Wentworth, Carl M.; Hendley, James W.

    1995-01-01

    When a powerful earthquake strikes an urban region, damage concentrates not only near the quake's source. Damage can also occur many miles from the source in areas of soft ground. In recent years, scientists have developed ways to identify and map these areas of high seismic hazard. This advance has spurred pioneering legislation to reduce earthquake losses in areas of greatest hazard.

  17. Quantifying Similarity in Seismic Polarizations

    NASA Astrophysics Data System (ADS)

    Eaton, D. W. S.; Jones, J. P.; Caffagni, E.

    2015-12-01

    Measuring similarity in seismic attributes can help identify tremor, low S/N signals, and converted or reflected phases, in addition to diagnosing site noise and sensor misalignment in arrays. Polarization analysis is a widely accepted method for studying the orientation and directional characteristics of seismic phases via. computed attributes, but similarity is ordinarily discussed using qualitative comparisons with reference values. Here we introduce a technique for quantitative polarization similarity that uses weighted histograms computed in short, overlapping time windows, drawing on methods adapted from the image processing and computer vision literature. Our method accounts for ambiguity in azimuth and incidence angle and variations in signal-to-noise (S/N) ratio. Using records of the Mw=8.3 Sea of Okhotsk earthquake from CNSN broadband sensors in British Columbia and Yukon Territory, Canada, and vertical borehole array data from a monitoring experiment at Hoadley gas field, central Alberta, Canada, we demonstrate that our method is robust to station spacing. Discrete wavelet analysis extends polarization similarity to the time-frequency domain in a straightforward way. Because histogram distance metrics are bounded by [0 1], clustering allows empirical time-frequency separation of seismic phase arrivals on single-station three-component records. Array processing for automatic seismic phase classification may be possible using subspace clustering of polarization similarity, but efficient algorithms are required to reduce the dimensionality.

  18. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

    Joel Walls; M.T. Taner; Naum Derzhi; Gary Mavko; Jack Dvorkin

    2003-12-01

    We have developed and tested technology for a new type of direct hydrocarbon detection. The method uses inelastic rock properties to greatly enhance the sensitivity of surface seismic methods to the presence of oil and gas saturation. These methods include use of energy absorption, dispersion, and attenuation (Q) along with traditional seismic attributes like velocity, impedance, and AVO. Our approach is to combine three elements: (1) a synthesis of the latest rock physics understanding of how rock inelasticity is related to rock type, pore fluid types, and pore microstructure, (2) synthetic seismic modeling that will help identify the relative contributions of scattering and intrinsic inelasticity to apparent Q attributes, and (3) robust algorithms that extract relative wave attenuation attributes from seismic data. This project provides: (1) Additional petrophysical insight from acquired data; (2) Increased understanding of rock and fluid properties; (3) New techniques to measure reservoir properties that are not currently available; and (4) Provide tools to more accurately describe the reservoir and predict oil location and volumes. These methodologies will improve the industry's ability to predict and quantify oil and gas saturation distribution, and to apply this information through geologic models to enhance reservoir simulation. We have applied for two separate patents relating to work that was completed as part of this project.

  19. Southern Appalachian Regional Seismic Network

    SciTech Connect

    Chiu, S.C.C.; Johnston, A.C.; Chiu, J.M.

    1994-08-01

    The seismic activity in the southern Appalachian area was monitored by the Southern Appalachian Regional Seismic Network (SARSN) since late 1979 by the Center for Earthquake Research and Information (CERI) at Memphis State University. This network provides good spatial coverage for earthquake locations especially in east Tennessee. The level of activity concentrates more heavily in the Valley and Ridge province of eastern Tennessee, as opposed to the Blue Ridge or Inner Piedmont. The large majority of these events lie between New York - Alabama lineament and the Clingman/Ocoee lineament, magnetic anomalies produced by deep-seated basement structures. Therefore SARSN, even with its wide station spacing, has been able to define the essential first-order seismological characteristics of the Southern Appalachian seismic zone. The focal depths of the southeastern U.S. earthquakes concentrate between 8 and 16 km, occurring principally beneath the Appalachian overthrust. In cross-sectional views, the average seismicity is shallower to the east beneath the Blue Ridge and Piedmont provinces and deeper to the west beneath the Valley and Ridge and the North American craton. Results of recent focal mechanism studies by using the CERI digital earthquake catalog between October, 1986 and December, 1991, indicate that the basement of the Valley and Ridge province is under a horizontal, NE-SW compressive stress. Right-lateral strike-slip faulting on nearly north-south fault planes is preferred because it agrees with the trend of the regional magnetic anomaly pattern.

  20. Seismic hazard studies in Egypt

    NASA Astrophysics Data System (ADS)

    Mohamed, Abuo El-Ela A.; El-Hadidy, M.; Deif, A.; Abou Elenean, K.

    2012-12-01

    The study of earthquake activity and seismic hazard assessment of Egypt is very important due to the great and rapid spreading of large investments in national projects, especially the nuclear power plant that will be held in the northern part of Egypt. Although Egypt is characterized by low seismicity, it has experienced occurring of damaging earthquake effect through its history. The seismotectonic sitting of Egypt suggests that large earthquakes are possible particularly along the Gulf of Aqaba-Dead Sea transform, the Subduction zone along the Hellenic and Cyprean Arcs, and the Northern Red Sea triple junction point. In addition some inland significant sources at Aswan, Dahshour, and Cairo-Suez District should be considered. The seismic hazard for Egypt is calculated utilizing a probabilistic approach (for a grid of 0.5° × 0.5°) within a logic-tree framework. Alternative seismogenic models and ground motion scaling relationships are selected to account for the epistemic uncertainty. Seismic hazard values on rock were calculated to create contour maps for four ground motion spectral periods and for different return periods. In addition, the uniform hazard spectra for rock sites for different 25 periods, and the probabilistic hazard curves for Cairo, and Alexandria cities are graphed. The peak ground acceleration (PGA) values were found close to the Gulf of Aqaba and it was about 220 gal for 475 year return period. While the lowest (PGA) values were detected in the western part of the western desert and it is less than 25 gal.

  1. Britannia rules the seismic waves

    SciTech Connect

    Green, P.

    1984-04-01

    When a longwall mining operation penetrates an unforeseen discontinuity in the coal seam, all hell breaks loose. Productivity plummets while the shearer cuts through rock, and the high proportion of reject material overwhelms the preparation plant. And, if the discontinuity is large enough, the face may have to be abandoned. To avert such catastrophies, a technique developed in Britain for mapping the presence of discontinuities has been applied in the Meigs No. 1 mine of the Southern Ohio Coal Co. in Athens, Ohio. The technology, called in-seam seismic surveying, is similar to seismic exploration in the oil and gas industry. The principle of the in-seam survey is simple: A shock wave is sent through the coal seam. If there is a sandstone channel or a displacement fault in the seam, the sound waves will be reflected back and can be picked up by geophones. Conversely, geophones installed on the opposite side of a channel or fault will not pick up the sound waves (see box). Seismic surveys have been made for four years by Britain's National Coal Board (NCB), and were developed because practically all its production is from longwall mining, and knowing what lies ahead is critical. And with about 500 ft between longwall entries there's a large amount of unpenetrated seam to contain hidden discontinuities. Hence the interest in in-seam seismic surveys.

  2. Gun shot control unit for seismic exploration

    SciTech Connect

    Bowden, E. A.; Deline, G. R.; Koeijmans, G. D.

    1985-04-16

    A gun shot control unit for a seismic exploration system compensates for the inherent delay between the shot command signal and the actual occurrence of the seismic pulse. A digital clock is synchronized with an external source. Timing pulses occurring at a time preceding the timing pulse upon which the occurrence of a seismic pulse is desired are produced by the clock. These timing pulses start a digital counter at a time preceding the desired time of occurrence of the seismic pulse. This counter is adjustable so that the delay which interposes between the timing and the actual occurrence of the seismic pulse can be minimized.

  3. Tunnel Detection Using Seismic Methods

    NASA Astrophysics Data System (ADS)

    Miller, R.; Park, C. B.; Xia, J.; Ivanov, J.; Steeples, D. W.; Ryden, N.; Ballard, R. F.; Llopis, J. L.; Anderson, T. S.; Moran, M. L.; Ketcham, S. A.

    2006-05-01

    Surface seismic methods have shown great promise for use in detecting clandestine tunnels in areas where unauthorized movement beneath secure boundaries have been or are a matter of concern for authorities. Unauthorized infiltration beneath national borders and into or out of secure facilities is possible at many sites by tunneling. Developments in acquisition, processing, and analysis techniques using multi-channel seismic imaging have opened the door to a vast number of near-surface applications including anomaly detection and delineation, specifically tunnels. Body waves have great potential based on modeling and very preliminary empirical studies trying to capitalize on diffracted energy. A primary limitation of all seismic energy is the natural attenuation of high-frequency energy by earth materials and the difficulty in transmitting a high- amplitude source pulse with a broad spectrum above 500 Hz into the earth. Surface waves have shown great potential since the development of multi-channel analysis methods (e.g., MASW). Both shear-wave velocity and backscatter energy from surface waves have been shown through modeling and empirical studies to have great promise in detecting the presence of anomalies, such as tunnels. Success in developing and evaluating various seismic approaches for detecting tunnels relies on investigations at known tunnel locations, in a variety of geologic settings, employing a wide range of seismic methods, and targeting a range of uniquely different tunnel geometries, characteristics, and host lithologies. Body-wave research at the Moffat tunnels in Winter Park, Colorado, provided well-defined diffraction-looking events that correlated with the subsurface location of the tunnel complex. Natural voids related to karst have been studied in Kansas, Oklahoma, Alabama, and Florida using shear-wave velocity imaging techniques based on the MASW approach. Manmade tunnels, culverts, and crawl spaces have been the target of multi-modal analysis

  4. Seismic Imaging of Sandbox Models

    NASA Astrophysics Data System (ADS)

    Buddensiek, M. L.; Krawczyk, C. M.; Kukowski, N.; Oncken, O.

    2009-04-01

    Analog sandbox simulations have been applied to study structural geological processes to provide qualitative and quantitative insights into the evolution of mountain belts and basins. These sandbox simulations provide either two-dimensional and dynamic or pseudo-three-dimensional and static information. To extend the dynamic simulations to three dimensions, we combine the analog sandbox simulation techniques with seismic physical modeling of these sandbox models. The long-term objective of this approach is to image seismic and seismological events of static and actively deforming 3D analog models. To achieve this objective, a small-scale seismic apparatus, composed of a water tank, a PC control unit including piezo-electric transducers, and a positioning system, was built for laboratory use. For the models, we use granular material such as sand and glass beads, so that the simulations can evolve dynamically. The granular models are required to be completely water saturated so that the sources and receivers are directly and well coupled to the propagating medium. Ultrasonic source frequencies (˜500 kHz) corresponding to wavelengths ˜5 times the grain diameter are necessary to be able to resolve small scale structures. In three experiments of different two-layer models, we show that (1) interfaces of layers of granular materials can be resolved depending on the interface preparation more than on the material itself. Secondly, we show that the dilation between the sand grains caused by a string that has been pulled through the grains, simulating a shear zone, causes a reflection that can be detected in the seismic data. In the third model, we perform a seismic reflection survey across a model that contains both the prepared interface and a shear zone, and apply 2D-seismic reflection processing to improve the resolution. Especially for more complex models, the clarity and penetration depth need to be improved to study the evolution of geological structures in dynamic

  5. Seismic excitation by space shuttles

    USGS Publications Warehouse

    Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

    1992-01-01

    Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were

  6. Hybrid Streamers for Polar Seismic

    NASA Astrophysics Data System (ADS)

    Gifford, C. M.; Agah, A.; Tsoflias, G. P.

    2006-12-01

    We propose a new hybrid streamer seismic approach for polar regions that incorporates insertion of spiked geophones, the land streamer method of transportation, and mobile robotics. Current land streamers do not plant the geophone spike at each node location on the streamer(s) nor use robotic control. This approach combines the two methods, and is therefore termed "Hybrid Streamers". Land seismic 3D surveying is costly and time consuming due to manual handling of geophones and cables. Multiple streamers make this process simpler by allowing efficient deployment of large numbers of geophones. Hybrid streamers go further to robotically insert the geophone spike at each node location to achieve higher frequency and better resolution seismic images. For deployment and retrieval, the geophone spikes are drilled into the ground, or inserted using heat. This can be accomplished by modifying the geophone spike to be similar to a threaded screw or similar to a soldering iron for polar environments. Heat could help melt the ice during deployment, which would refreeze around the geophone for firm coupling. Heat could also be used to make polar geophone retrieval easier. By ensuring that the towing robots are robust and effective, the problem of single point of failure can be less of an issue. Polar rovers have proven useful in harsh environments, and could be utilized in polar seismic applications. Towing geophone nodes in a tethered fashion not only provides all nodes with power to operate the onboard equipment, but also gives them a medium to transfer data to the towing rover. Hybrid streamers could be used in several ways. One or more hybrid streamers could be tethered and towed by a single robot. Several robots could be used to form a single grid, working in conjunction to image larger areas in three dimensions. Such an approach could speed up entire missions and make efficient use of seismic source ignitions. The reduction of human involvement by use of mobile robots

  7. Statistical Seismology and Induced Seismicity

    NASA Astrophysics Data System (ADS)

    Tiampo, K. F.; González, P. J.; Kazemian, J.

    2014-12-01

    While seismicity triggered or induced by natural resources production such as mining or water impoundment in large dams has long been recognized, the recent increase in the unconventional production of oil and gas has been linked to rapid rise in seismicity in many places, including central North America (Ellsworth et al., 2012; Ellsworth, 2013). Worldwide, induced events of M~5 have occurred and, although rare, have resulted in both damage and public concern (Horton, 2012; Keranen et al., 2013). In addition, over the past twenty years, the increase in both number and coverage of seismic stations has resulted in an unprecedented ability to precisely record the magnitude and location of large numbers of small magnitude events. The increase in the number and type of seismic sequences available for detailed study has revealed differences in their statistics that previously difficult to quantify. For example, seismic swarms that produce significant numbers of foreshocks as well as aftershocks have been observed in different tectonic settings, including California, Iceland, and the East Pacific Rise (McGuire et al., 2005; Shearer, 2012; Kazemian et al., 2014). Similarly, smaller events have been observed prior to larger induced events in several occurrences from energy production. The field of statistical seismology has long focused on the question of triggering and the mechanisms responsible (Stein et al., 1992; Hill et al., 1993; Steacy et al., 2005; Parsons, 2005; Main et al., 2006). For example, in most cases the associated stress perturbations are much smaller than the earthquake stress drop, suggesting an inherent sensitivity to relatively small stress changes (Nalbant et al., 2005). Induced seismicity provides the opportunity to investigate triggering and, in particular, the differences between long- and short-range triggering. Here we investigate the statistics of induced seismicity sequences from around the world, including central North America and Spain, and

  8. Seismic electromagnetic study in China

    NASA Astrophysics Data System (ADS)

    Huang, Qinghua

    2016-04-01

    Seismo-electromagnetism is becoming a hot interdisciplinary study in both geosciences and electromagnetism. Numerous electromagnetic changes at a broad range of frequencies associated with earthquakes have been reported independently. There are some attempts of applying such electromagnetic data to short-term earthquake prediction. Although due to the complexity of seismogenic process and underground structure, the seismic electromagnetic phenomena cannot be fully understood, the seismic electromagnetic study plays a key role in the mitigation of seismic hazard. China is one of the countries which have the earliest reports on seismo-electromagnetic phenomena. The seismic electromagnetic study in China started in late 1960's. There are almost 50 years continuous observation data up to now, which provides a unique database for seismo-electromagnetic study not only in China, but also in the world. Therefore, seismo-electromagnetic study in China is interested broadly by international communities of geosciences and electromagnetism. I present here a brief review on seismic electromagnetic study in China, especially focusing on geo-electromagnetic observation and empirical prediction based on the observation data. After summarizing various electromagnetic observations such as apparent resistivity, geoelectric potential, geomagnetic field, electromagnetic disturbance, and so on, I show the cases of the empirical prediction based on the observed electromagnetic data associated with some earthquakes in China. Finally, based on the above review, I propose an integrated research scheme of earthquake-related electromagnetic phenomena, which includes the interaction between appropriate observations, robust methodology of data processing, and theoretical model analysis. This study is supported partially by the National Natural Science Foundation of China (41274075) and the National Basic Research Program of China (2014CB845903).

  9. The Southern Kansas Seismic Network

    NASA Astrophysics Data System (ADS)

    Terra, F. M.

    2015-12-01

    Historically aseismic Harper and Sumner counties in Southern Kansas experienced a dramatic increase in seismicity beginning in early 2014, coincident with the development of new oil production in the Mississippi Lime Play. In order to better understand the potential relationships between seismicity and oil development, the USGS installed a real-time telemetered seismic network in cooperation with the Kansas Geological Survey, the Kansas Corporation Commission, the Kansas Department of Health and Environment, Harper County, and the Oklahoma Geological Survey. The network began operation in March 2014 with an initial deployment of 5 NetQuakes accelerometers and by July 2014 had expanded to include 10 broadband sites. The network currently has 14 stations, all with accelerometers and 12 with broadband seismometers. The network has interstation spacing of 15 - 25 km and typical azimuthal gap of 80 for well-located events. Data are continuously streamed to IRIS at 200 samples per second from most sites. Earthquake locations are augmented with additional stations from the USGS National Network, Oklahoma Geological Survey Seismic Network, Kansas Seismic Monitoring Network and the Enid Oklahoma Network. Since the spring of 2014 over 7500 earthquakes have been identified with data from this network, 1400 of which have been manually timed and cataloged. Focal depths for earthquakes typically range between 2 and 7 km. The catalog is available at earthquake.usgs.gov/earthquakes/search/ under network code 'Ismpkansas'. The network recorded the largest known earthquake in Harper County, Mw 4.3, on October 2, 2014 and in Sumner County, Mw 4.9, on November 12, 2014. Recorded ground motions at the epicenter of the October earthquake were 0.70 g (PGA) and 12 cm/s (PGV). These high ground motion values agree with near-source recordings made by other USGS temporary deployments in the U. S. midcontinent, indicating a significant shaking hazard from such shallow, moderate

  10. Time-dependent seismic tomography

    USGS Publications Warehouse

    Julian, B.R.; Foulger, G.R.

    2010-01-01

    Of methods for measuring temporal changes in seismic-wave speeds in the Earth, seismic tomography is among those that offer the highest spatial resolution. 3-D tomographic methods are commonly applied in this context by inverting seismic wave arrival time data sets from different epochs independently and assuming that differences in the derived structures represent real temporal variations. This assumption is dangerous because the results of independent inversions would differ even if the structure in the Earth did not change, due to observational errors and differences in the seismic ray distributions. The latter effect may be especially severe when data sets include earthquake swarms or aftershock sequences, and may produce the appearance of correlation between structural changes and seismicity when the wave speeds are actually temporally invariant. A better approach, which makes it possible to assess what changes are truly required by the data, is to invert multiple data sets simultaneously, minimizing the difference between models for different epochs as well as the rms arrival-time residuals. This problem leads, in the case of two epochs, to a system of normal equations whose order is twice as great as for a single epoch. The direct solution of this system would require twice as much memory and four times as much computational effort as would independent inversions. We present an algorithm, tomo4d, that takes advantage of the structure and sparseness of the system to obtain the solution with essentially no more effort than independent inversions require. No claim to original US government works Journal compilation ?? 2010 RAS.

  11. Assessment of seismic loss dependence using copula.

    PubMed

    Goda, Katsuichiro; Ren, Jiandong

    2010-07-01

    The catastrophic nature of seismic risk is attributed to spatiotemporal correlation of seismic losses of buildings and infrastructure. For seismic risk management, such correlated seismic effects must be adequately taken into account, since they affect the probability distribution of aggregate seismic losses of spatially distributed structures significantly, and its upper tail behavior can be of particular importance. To investigate seismic loss dependence for two closely located portfolios of buildings, simulated seismic loss samples, which are obtained from a seismic risk model of spatially distributed buildings by taking spatiotemporally correlated ground motions into account, are employed. The characterization considers a loss frequency model that incorporates one dependent random component acting as a common shock to all buildings, and a copula-based loss severity model, which facilitates the separate construction of marginal loss distribution functions and nonlinear copula function with upper tail dependence. The proposed method is applied to groups of wood-frame buildings located in southwestern British Columbia. Analysis results indicate that the dependence structure of aggregate seismic losses can be adequately modeled by the right heavy tail copula or Gumbel copula, and that for the considered example, overall accuracy of the proposed method is satisfactory at probability levels of practical interest (at most 10% estimation error of fractiles of aggregate seismic loss). The developed statistical seismic loss model may be adopted in dynamic financial analysis for achieving faster evaluation with reasonable accuracy.

  12. New sensitive seismic cable with imbedded geophones

    NASA Astrophysics Data System (ADS)

    Pakhomov, Alex; Pisano, Dan; Goldburt, Tim

    2005-10-01

    Seismic detection systems for homeland security applications are an important additional layer to perimeter and border protection and other security systems. General Sensing Systems has been developing low mass, low cost, highly sensitive geophones. These geophones are being incorporated within a seismic cable. This article reports on the concept of a seismic sensitive cable and seismic sensitive ribbon design. Unlike existing seismic cables with sensitivity distributed along their lengths, the GSS new cable and ribbon possesses high sensitivity distributed in several points along the cable/ribbon with spacing of about 8-12 to 100 meters between geophones. This cable/ribbon is highly suitable for design and installation in extended perimeter protection systems. It allows the use of a mechanical cable layer for high speed installation. We show that any installation mistakes in using the GSS seismic sensitive cable/ribbon have low impact on output seismic signal value and detection range of security systems.

  13. Seismic evaluation of municipal solid waste landfill

    SciTech Connect

    Hovind, C.; Slyh, R.

    1995-12-31

    With the promulgation of the Resource Conservation and Recovery (RCRA) Subtitle D, landfills situated within seismic impact zones must be evaluated for seismic hazards to demonstrate that the containment structures of the landfill can resist the maximum horizontal acceleration in lithified earth materials (bedrock) for the site. If a landfill is sited on saturated soils, it must also be evaluated for liquefaction and lateral spreading. In 1994, EMCON evaluated the seismic hazard for a landfill located along the Columbia River in southwestern Washington. The landfill was founded on dredge fill over natural alluvial deposits. Laboratory testing and state-of-the-art engineering analyses indicated that the sand unit below the landfill had a high potential for liquefaction. The seismic hazard evaluation for the site included a site-specific seismic response analysis, a liquefaction potential analysis, and seismic stability and deformation analysis. The seismic response analysis was conducted for nonliquefied, partially liquefied, and fully liquefied foundation soil conditions. Results are described.

  14. Seismic Risk Perception compared with seismic Risk Factors

    NASA Astrophysics Data System (ADS)

    Crescimbene, Massimo; La Longa, Federica; Pessina, Vera; Pino, Nicola Alessandro; Peruzza, Laura

    2016-04-01

    The communication of natural hazards and their consequences is one of the more relevant ethical issues faced by scientists. In the last years, social studies have provided evidence that risk communication is strongly influenced by the risk perception of people. In order to develop effective information and risk communication strategies, the perception of risks and the influencing factors should be known. A theory that offers an integrative approach to understanding and explaining risk perception is still missing. To explain risk perception, it is necessary to consider several perspectives: social, psychological and cultural perspectives and their interactions. This paper presents the results of the CATI survey on seismic risk perception in Italy, conducted by INGV researchers on funding by the DPC. We built a questionnaire to assess seismic risk perception, with a particular attention to compare hazard, vulnerability and exposure perception with the real data of the same factors. The Seismic Risk Perception Questionnaire (SRP-Q) is designed by semantic differential method, using opposite terms on a Likert scale to seven points. The questionnaire allows to obtain the scores of five risk indicators: Hazard, Exposure, Vulnerability, People and Community, Earthquake Phenomenon. The questionnaire was administered by telephone interview (C.A.T.I.) on a statistical sample at national level of over 4,000 people, in the period January -February 2015. Results show that risk perception seems be underestimated for all indicators considered. In particular scores of seismic Vulnerability factor are extremely low compared with house information data of the respondents. Other data collected by the questionnaire regard Earthquake information level, Sources of information, Earthquake occurrence with respect to other natural hazards, participation at risk reduction activities and level of involvement. Research on risk perception aims to aid risk analysis and policy-making by

  15. Broadband seismic and acoustic observations of volcanic seismicity

    NASA Astrophysics Data System (ADS)

    Aster, R.; Lees, J.; Neuberg, J.

    2000-08-01

    It has been frequently noted (e.g. Aki, 1992) that volcanoes present some of the most difficult challenges in seismology due to a plethora of complex source and structural issues. The broadband seismo-acoustic study of active volcanoes is still in its adolescence, and the papers in this volume primarily describe first-order attempts to understand these signals and to build on a much longer history of short-period seismic observations and interpretations.

  16. Gravity and seismicity over the Guerrero Seismic Gap, Mexico

    NASA Astrophysics Data System (ADS)

    Kostoglodov, V.; Bandy, W.; Domínguez, J.; Mena, M.

    Four detailed (average station interval = 5 km) gravity transects were recently conducted in the Pacific coastal region of Mexico. A differential GPS technique was used to determine the elevation and coordinates of the gravity stations. The profiles are oriented northeast-southwest and extend from the coast up to ˜60 km inland. The Bouguer gravity anomaly is decreasing consistently along every profile from 60-80 mGal at the coast with an approximately constant regional gradient of -2.2 mGal/km normal to the trench. A plot of the gravity anomaly against the distance from the trench axis demonstrates that the regional slope in the gravity anomaly is shifting gradually (20-25 mGal) inland along the coast of Guerrero from the southeast (Atoyac) to the northwest (Petatlán - Zihuatanejo). A model cross section of the Mexican subduction zone (MSZ) based on the tomography inversion for the Guerrero region shows that the gravity anomaly values and the regional anomaly trend can be explained mostly by the effect of the density contrast between the slab and the continental crust. The upper surface of the subducted slab (USS) and the seismogenic contact zone between the upper plate and the slab is traced clearly in several seismicity cross sections based on the data of the regional seismic network in Guerrero. The depth and shape of the USS revealed from the seismicity and gravity anomaly data for the same profiles are in good agreement. This correlation may be fairly useful when applied to gravity profiles in order to estimate the depth of the USS and the seismogenic contact in other parts of the MSZ which lack reliable seismicity data.

  17. Seismic slip deficit along Nepal Himalayas: implications for seismic hazard

    NASA Astrophysics Data System (ADS)

    Bollinger, Laurent; Tapponnier, Paul; Nath Sapkota, Soma; Klinger, Yann

    2016-04-01

    In 1255, 1344 and 1408 AD, then again in 1833, 1934 and 2015, large earthquakes, devastated Kathmandu. The 1255 and 1934 surface ruptures have been identified east of the city, along comparable segments of the Main Frontal Thrust (MFT). Whether the other two pairs of events were similar, is unclear. Taking into account charcoal's "Inbuilt-ages", we revisit the timing of terrace offsets at key sites, to compare them with the seismic record since 1200 AD. The location, extent, and seismic moment of the 1833 and 2015 events imply that they released only a small part of the regional slip deficit, on a deep thrust segment that stopped north of the Siwaliks. By contrast, the 1344 or 1408 AD earthquake may have ruptured the MFT up to the surface in central Nepal between Kathmandu and Pokhara, East of the surface trace of the great 1505 AD earthquake which affected Western Nepal. If so, the whole megathrust system in Nepal ruptured during a sequence of earthquakes that lasted less than three centuries and propagated the rupture up to the surface from East to West. Today's situation in the himalayan seismic sequence might be close to that of the 14th century.

  18. Seismic Velocity Measurements at Expanded Seismic Network Sites

    SciTech Connect

    Woolery, Edward W; Wang, Zhenming

    2005-01-01

    Structures at the Paducah Gaseous Diffusion Plant (PGDP), as well as at other locations in the northern Jackson Purchase of western Kentucky may be subjected to large far-field earthquake ground motions from the New Madrid seismic zone, as well as those from small and moderate-sized local events. The resultant ground motion a particular structure is exposed from such event will be a consequence of the earthquake magnitude, the structures' proximity to the event, and the dynamic and geometrical characteristics of the thick soils upon which they are, of necessity, constructed. This investigation evaluated the latter. Downhole and surface (i.e., refraction and reflection) seismic velocity data were collected at the Kentucky Seismic and Strong-Motion Network expansion sites in the vicinity of the Paducah Gaseous Diffusion Plant (PGDP) to define the dynamic properties of the deep sediment overburden that can produce modifying effects on earthquake waves. These effects are manifested as modifications of the earthquake waves' amplitude, frequency, and duration. Each of these three ground motion manifestations is also fundamental to the assessment of secondary earthquake engineering hazards such as liquefaction.

  19. Reconstruction of a 2D seismic wavefield by seismic gradiometry

    NASA Astrophysics Data System (ADS)

    Maeda, Takuto; Nishida, Kiwamu; Takagi, Ryota; Obara, Kazushige

    2016-12-01

    We reconstructed a 2D seismic wavefield and obtained its propagation properties by using the seismic gradiometry method together with dense observations of the Hi-net seismograph network in Japan. The seismic gradiometry method estimates the wave amplitude and its spatial derivative coefficients at any location from a discrete station record by using a Taylor series approximation. From the spatial derivatives in horizontal directions, the properties of a propagating wave packet, including the arrival direction, slowness, geometrical spreading, and radiation pattern can be obtained. In addition, by using spatial derivatives together with free-surface boundary conditions, the 2D vector elastic wavefield can be decomposed into divergence and rotation components. First, as a feasibility test, we performed an analysis with a synthetic seismogram dataset computed by a numerical simulation for a realistic 3D medium and the actual Hi-net station layout. We confirmed that the wave amplitude and its spatial derivatives were very well-reproduced for period bands longer than 25 s. Applications to a real large earthquake showed that the amplitude and phase of the wavefield were well reconstructed, along with slowness vector. The slowness of the reconstructed wavefield showed a clear contrast between body and surface waves and regional non-great-circle-path wave propagation, possibly owing to scattering. Slowness vectors together with divergence and rotation decomposition are expected to be useful for determining constituents of observed wavefields in inhomogeneous media.

  20. Hanford quarterly seismic monitoring report 96C

    SciTech Connect

    Reidel, S.P.

    1996-09-24

    Seismic monitoring at the Hanford Site was established in 1969 by the United States Geological Survey (USGS) under a contract with the U.S. Atomic Energy Commission. In 1975 the University of Washington assumed responsibility for and expanded the network. In 1979 the Basalt Waste Isolation Program (BWIP) became responsible for collecting seismic data for the site as part of site characterization. Rockwell International Operations followed by Westinghouse Hanford Company (WHC), Geosciences Group, operated the local network and were the contract technical advisors for the Eastern Washington Regional Network operated by the University of Washington. Funding ended for BWIP in December 1988. Seismic Monitoring and the University of Washington contract was then transferred WHC`s Environmental Division. Seismic Monitoring is currently assigned to WHC`s Hanford Technical Services (HTS), part of the Environmental Division. The Seismic Monitoring Analysis and Repair Team (SMART) operates, maintains, and analyzes data from the Hanford Seismic Network (HSN), extending the site historical seismic database and fulfilling U.S. Department of Energy, Richland Operations Office requirements and orders. The Seismic Monitoring Analysis and Repair Team also maintains the Eastern Washington Regional Network (EWRN). The University of Washington uses the data from the EWRN and other seismic networks in the Northwest to provide the SMART with necessary regional input for the seismic hazards analysis at the Hanford Site.

  1. Seismic Isolation Working Meeting Gap Analysis Report

    SciTech Connect

    Coleman, Justin; Sabharwall, Piyush

    2014-09-01

    The ultimate goal in nuclear facility and nuclear power plant operations is operating safety during normal operations and maintaining core cooling capabilities during off-normal events including external hazards. Understanding the impact external hazards, such as flooding and earthquakes, have on nuclear facilities and NPPs is critical to deciding how to manage these hazards to expectable levels of risk. From a seismic risk perspective the goal is to manage seismic risk. Seismic risk is determined by convolving the seismic hazard with seismic fragilities (capacity of systems, structures, and components (SSCs)). There are large uncertainties associated with evolving nature of the seismic hazard curves. Additionally there are requirements within DOE and potential requirements within NRC to reconsider updated seismic hazard curves every 10 years. Therefore opportunity exists for engineered solutions to manage this seismic uncertainty. One engineered solution is seismic isolation. Current seismic isolation (SI) designs (used in commercial industry) reduce horizontal earthquake loads and protect critical infrastructure from the potentially destructive effects of large earthquakes. The benefit of SI application in the nuclear industry is being recognized and SI systems have been proposed, in the American Society of Civil Engineers (ASCE) 4 standard, to be released in 2014, for Light Water Reactors (LWR) facilities using commercially available technology. However, there is a lack of industry application to the nuclear industry and uncertainty with implementing the procedures outlined in ASCE-4. Opportunity exists to determine barriers associated with implementation of current ASCE-4 standard language.

  2. Subaqueous landslides at the distal basin of Lago Nahuel Huapi (Argentina): Towards a tsunami hazard evaluation in Northern Patagonian lakes

    NASA Astrophysics Data System (ADS)

    Beigt, Débora; Villarosa, Gustavo; Gómez, Eduardo A.; Manzoni, Carolina

    2016-09-01

    The May 22nd, 1960 Valdivia earthquake, Chile (Mw 9.5) triggered a series of subaqueous mass-wasting processes (debris flows and slides) in Lago Nahuel Huapi (Argentina), generating a tsunami-like wave that hit the coasts of San Carlos de Bariloche. Aiming to provide a first preliminary insight into tsunami hazards for the lakeshore communities, in this paper we identify and characterize the subaqueous landslides at the populated distal basin of the lake. Swath bathymetric and seismic profiling surveys were carried out and high-resolution digital elevation models were derived from these data to perform a landslide inventory map. A series of morphometrical parameters (including the landslide area, the volume of displaced materials and the run-out distance, among others) were estimated upon selected events. The results indicated that landslide activity at the distal basin of Lago Nahuel Huapi has been concentrated in the vicinity of Bariloche (massive landslide triggered by the 1960 earthquake) and within steep delta fronts where the slope failures typically initiate at shallow waters (9-11 m depth). The sliding mass frequently travels basinward along a great distance (≥ 1000 m). At the delta fronts, the volume of material removed by landslides can reach ~ 40 × 104 m3, leaving scar areas of up to 13 m thick. The periodic occurrence of rotational-translational mass movements initiating at the upper edge of the delta fronts, with vertical displacements of the mobilized materials reaching ~ 200 m, probably represents a potential tsunami hazard for the nearby populated coasts.

  3. Exploring the seismic expression of fault zones in 3D seismic volumes

    NASA Astrophysics Data System (ADS)

    Iacopini, D.; Butler, R. W. H.; Purves, S.; McArdle, N.; De Freslon, N.

    2016-08-01

    Mapping and understanding distributed deformation is a major challenge for the structural interpretation of seismic data. However, volumes of seismic signal disturbance with low signal/noise ratio are systematically observed within 3D seismic datasets around fault systems. These seismic disturbance zones (SDZ) are commonly characterized by complex perturbations of the signal and occur at the sub-seismic (10 s m) to seismic scale (100 s m). They may store important information on deformation distributed around those larger scale structures that may be readily interpreted in conventional amplitude displays of seismic data. We introduce a method to detect fault-related disturbance zones and to discriminate between this and other noise sources such as those associated with the seismic acquisition (footprint noise). Two case studies from the Taranaki basin and deep-water Niger delta are presented. These resolve SDZs using tensor and semblance attributes along with conventional seismic mapping. The tensor attribute is more efficient in tracking volumes containing structural displacements while structurally-oriented semblance coherency is commonly disturbed by small waveform variations around the fault throw. We propose a workflow to map and cross-plot seismic waveform signal properties extracted from the seismic disturbance zone as a tool to investigate the seismic signature and explore seismic facies of a SDZ.

  4. Exploring the seismic expression of fault zones in 3D seismic volumes

    NASA Astrophysics Data System (ADS)

    Iacopini, David; Butler, Rob; Purves, Steve

    2016-04-01

    Mapping and understanding distributed deformation is a major challenge for the structural interpretation of seismic data. However, volumes of seismic signal disturbance with low signal/noise ratio are systematically observed within 3D seismic datasets around fault systems. These seismic disturbance zones (SDZ) are commonly characterized by complex perturbations of the signal and occur at the sub-seismic to seismic scale. They may store important information on deformation distributed around those larger scale structures that may be readily interpreted in conventional amplitude displays of seismic data scale. We introduce a method to detect fault-related disturbance zones and to discriminate between this and other noise sources such as those associated with the seismic acquisition (footprint noise). Two case studies, from the Taranaki basin and deep-water Niger delta are presented. These resolve structure within SDZs using tensor and semblance attributes along with conventional seismic mapping. The tensor attribute is more efficient in tracking volumes containing structural displacements while structurally-oriented semblance coherency is commonly disturbed by small waveform variations around the fault throw. We propose a workflow to map and cross-plot seismic waveform signal properties extracted from the seismic disturbance zone as a tool to investigate the seismic signature and explore seismic facies of a SDZ.

  5. Tube-wave seismic imaging

    DOEpatents

    Korneev, Valeri A [Lafayette, CA; Bakulin, Andrey [Houston, TX

    2009-10-13

    The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded approximately 2000 feet above the reservoir. A tube-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a tube-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The tube-wave has been shown to be extremely sensitive to changes in reservoir characteristics. Tube-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.

  6. Tube-wave seismic imaging

    DOEpatents

    Korneev, Valeri A [LaFayette, CA

    2009-05-05

    The detailed analysis of cross well seismic data for a gas reservoir in Texas revealed two newly detected seismic wave effects, recorded approximately 2000 feet above the reservoir. A tube-wave (150) is initiated in a source well (110) by a source (111), travels in the source well (110), is coupled to a geological feature (140), propagates (151) through the geological feature (140), is coupled back to a tube-wave (152) at a receiver well (120), and is and received by receiver(s) (121) in either the same (110) or a different receiving well (120). The tube-wave has been shown to be extremely sensitive to changes in reservoir characteristics. Tube-waves appear to couple most effectively to reservoirs where the well casing is perforated, allowing direct fluid contact from the interior of a well case to the reservoir.

  7. DISPLACEMENT BASED SEISMIC DESIGN CRITERIA

    SciTech Connect

    HOFMAYER,C.H.

    1999-03-29

    The USNRC has initiated a project to determine if any of the likely revisions to traditional earthquake engineering practice are relevant to seismic design of the specialized structures, systems and components of nuclear power plants and of such significance to suggest that a change in design practice might be warranted. As part of the initial phase of this study, a literature survey was conducted on the recent changes in seismic design codes/standards, on-going activities of code-writing organizations/communities, and published documents on displacement-based design methods. This paper provides a summary of recent changes in building codes and on-going activities for future codes. It also discusses some technical issues for further consideration.

  8. Regional variations in seismic boundaries

    NASA Astrophysics Data System (ADS)

    Shumlyanska, Ludmila

    2010-05-01

    Dividing of the Earth into zones in the frame one-dimensional velocity model was proposed Jeffreys and Gutenberg is the first half of XX century. They recovered the following zones: A - the crust; B - zone in the depth interval 33-413 km, C - zone 413-984 km, D - zone 984-2898 km, E - 2898-4982 km, F - 4982-5121 km, G - 5121-6371 km (centre of the Earth). These zones differ in their seismic properties. Later, zone D was divided to the areas D' (984-2700 km) and D" (2700-2900 km). At present, this scheme is significantly modified and only the layer D" is in wide use. The more seismological studies are carried out, the more seismic boundaries appear. Boundaries at 410, 520, 670, and 2900 km, at which increase in the velocity of the seismic waves is particularly noticeable are considered as having global significance. Moreover, there are indications of the existence of geophysical boundaries at 800, 1200-1300, 1700, 1900-2000 km. Using 3D P-velocity model of the mantle based on Taylor approximation method for solving of the inverse kinematics multi-dimensional seismic task we have obtained seismic boundaries for the area covering 20-55° E × 40-55° N. Data on the time of first arrivals of P waves from earthquakes and nuclear explosions recorded at ISC stations during 1964-2002 were used as input to construct a 3-D model. The model has two a priori limits: 1) the velocity is a continuous function of spatial coordinates, 2) the function v(r)/r where r is a radius in the spherical coordinate system r, φ, λ decreases with depth. The first limitation is forced since velocity leaps can not be sustainably restored from the times of first arrival; the second one follows from the nature of the observed data. Results presented as horizontal sections of the actual velocity every 25 km in the depth interval 850-2850 km, and as the longitudinal and latitudinal sections of the discrepancy on the 1-D reference model, obtained as a result of solving of the inversion task at 1

  9. Continental collisions and seismic signature

    NASA Astrophysics Data System (ADS)

    Meissner, R.; Wever, Th.; Sadowiak, P.

    1991-04-01

    Reflection seismics in compressional belts has revealed the structure of crustal shortening and thickening processes, showing complex patterns of indentation and interfingering of colliding crusts and subcrustal lithospheres. Generally, in the upper crust large zones of detachments develop, often showing duplexes and 'crocodile' structures. The lower crust from zones of active collision (e.g. Alps, Pyrenees) is characterized by strongly dipping reflections. The base of the crust with the Moho must be continuously equilibrating after orogenic collapse as areas of former continental collision exhibit flat Mohos and subhorizontal reflections. The depth to the Moho increases during collision and decreases after the onset of post-orogenic extension, until finally the crustal root disappears completely together with the erosion of the mountains. Processes, active during continental collisions and orogenic collapse, create distinct structures which are imaged by reflection seismic profiling. Examples are shown and discussed.

  10. Laboratory simulation of volcano seismicity.

    PubMed

    Benson, Philip M; Vinciguerra, Sergio; Meredith, Philip G; Young, R Paul

    2008-10-10

    The physical processes generating seismicity within volcanic edifices are highly complex and not fully understood. We report results from a laboratory experiment in which basalt from Mount Etna volcano (Italy) was deformed and fractured. The experiment was monitored with an array of transducers around the sample to permit full-waveform capture, location, and analysis of microseismic events. Rapid post-failure decompression of the water-filled pore volume and damage zone triggered many low-frequency events, analogous to volcanic long-period seismicity. The low frequencies were associated with pore fluid decompression and were located in the damage zone in the fractured sample; these events exhibited a weak component of shear (double-couple) slip, consistent with fluid-driven events occurring beneath active volcanoes.

  11. Nuclear component horizontal seismic restraint

    DOEpatents

    Snyder, Glenn J.

    1988-01-01

    A nuclear component horizontal seismic restraint. Small gaps limit horizontal displacement of components during a seismic occurrence and therefore reduce dynamic loadings on the free lower end. The reactor vessel and reactor guard vessel use thicker section roll-forged rings welded between the vessel straight shell sections and the bottom hemispherical head sections. The inside of the reactor guard vessel ring forging contains local vertical dovetail slots and upper ledge pockets to mount and retain field fitted and installed blocks. As an option, the horizontal displacement of the reactor vessel core support cone can be limited by including shop fitted/installed local blocks in opposing alignment with the reactor vessel forged ring. Beams embedded in the wall of the reactor building protrude into apertures in the thermal insulation shell adjacent the reactor guard vessel ring and have motion limit blocks attached thereto to provide to a predetermined clearance between the blocks and reactor guard vessel ring.

  12. An economical educational seismic system

    USGS Publications Warehouse

    Lehman, J. D.

    1980-01-01

    There is a considerable interest in seismology from the nonprofessional or amateur standpoint. The operation of a seismic system can be satisfying and educational, especially when you have built and operated the system yourself. A long-period indoor-type sensor and recording system that works extremely well has been developed in the James Madison University Physics Deparment. The system can be built quite economically, and any educational institution that cannot commit themselves to a professional installation need not be without first-hand seismic information. The system design approach has been selected by college students working a project or senior thesis, several elementary and secondary science teachers, as well as the more ambitious tinkerer or hobbyist at home 

  13. The Norwegian Seismic Array (NORSAR).

    DTIC Science & Technology

    1985-12-01

    by the Western Norway seismic network. For one site where a large number of known explosions (36) were processed, the average NORESS location error... description of NOI{ESS data tapes. NORESS * "data are recorded 24 hours a day and all data are stored permanently. Data from NORESS are available from NORSAR...list activities carried out at both the NORSAR and NORESS sites . Subarray/ area Task Date NORESS A satellite transmitter amplifier (TWT) 24 April failed

  14. Seismic Analysis of Intake Towers

    DTIC Science & Technology

    1982-10-01

    AREA & WORK UNIT NUMBERS Structures Laboratory Structural Engineering P. 0. Box 631, Vicksburg, Miss. 39180 Research Work Unit 31588 It. CONTROLLING ...AGENCY NAME & ADDRESS(if ditffrsnt frost Controlling Office) IS. SECURITY CLASS. (of this report) Unclassified I4a. DECL ASSIFI CATION/DOWN GRADI NO...needed for a controlled release of the reservoir to repair any seismic damage in the damming structure. The high cost associated with these criteria for a

  15. Solar, geomagnetic and seismic activity

    NASA Astrophysics Data System (ADS)

    Mazzarella, A.; Palumbo, A.

    1988-08-01

    An 11-yr modulation of large Italian earthquakes has been successfully identified and found to be positively linked to sunspot activity. The seismic activity appears to be modulated by the 11-yr sunspot cycle through the coherent variation of geomagnetic activity. It is proposed that the two phenomena are linked by the influence of a magnetostriction process on stresses in the crust. An implication of this model is that geomagnetic storms may directly trigger large earthquakes.

  16. Seismic Imaging of Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Nataf, Henri-Claude

    The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

  17. The ISC Seismic Event Bibliography

    NASA Astrophysics Data System (ADS)

    Di Giacomo, Domenico; Storchak, Dmitry

    2015-04-01

    The International Seismological Centre (ISC) is a not-for-profit organization operating in the UK for the last 50 years and producing the ISC Bulletin - the definitive worldwide summary of seismic events, both natural and anthropogenic - starting from the beginning of 20th century. Often researchers need to gather information related to specific seismic events for various reasons. To facilitate such task, in 2012 we set up a new database linking earthquakes and other seismic events in the ISC Bulletin to bibliographic records of scientific articles (mostly peer-reviewed journals) that describe those events. Such association allows users of the ISC Event Bibliography (www.isc.ac.uk/event_bibliography/index.php) to run searches for publications via a map-based web interface and, optionally, selecting scientific publications related to either specific events or events in the area of interest. Some of the greatest earthquakes were described in several hundreds of articles published over a period of few years. The journals included in our database are not limited to seismology but bring together a variety of fields in geosciences (e.g., engineering seismology, geodesy and remote sensing, tectonophysics, monitoring research, tsunami, geology, geochemistry, hydrogeology, atmospheric sciences, etc.) making this service useful in multidisciplinary studies. Usually papers dealing with large data set are not included (e.g., papers describing a seismic catalogue). Currently the ISC Event Bibliography includes over 17,000 individual publications from about 500 titles related to over 14,000 events that occurred in last 100+ years. The bibliographic records in the Event Bibliography start in the 1950s, and it is updated as new publications become available.

  18. Seismic Observation of Infrasonic Signals

    DTIC Science & Technology

    1984-11-01

    the event on day 088 are presented in figures 6 through 12. This eruptive sequence was complex with repeated injections into the plinian column...presented in figures 36 through 46. This eruptive sequence was large and complex with repeated injections into the plinian column. Envelope maxima... eruptive sequences of El Chichon volcano. Application of the pure-state filter improved the signal-to-noise ratio of the seismically detected infrasonic

  19. Seismic Imaging from a TBM

    NASA Astrophysics Data System (ADS)

    Swinnen, G.; Thorbecke, J. W.; Drijkoningen, G. G.

    2007-12-01

    Seismic monitoring from the head of a tunnel-boring machine (TBM) enables improved assessment of the risks associated with the tunnel-boring process. The monitoring system provides a live image of ground conditions along the trajectory followed by the TBM and detects local heterogeneities such as boulders, foundations, and other obstacles that commonly pass undetected using local geotechnical techniques. From a seismic perspective, the underground setting of tunnelling projects places limitations on imaging capability. The principal limiting factor is the size of the area upon which transducers can be installed. This limitation requires adjustments to traditional seismic imaging techniques in which a large area is assumed to be available for attaching the transducers. Recently developed short imaging operators take this limitation into account and are used in the examples described herein. The unique conditions of tunnelling yield two advantages over traditional settings in terms of imaging: rotation of the cutter wheel and the lateral progression of the TBM. Rotation of the cutter wheel, upon which the transducers are installed, provides the opportunity to illuminate obstacles from different angles in different recordings. Spatial progression of the TBM enables improvement in the illumination of obstacles and the signal-to-noise ratio by combining recordings from different lateral positions. In this paper, these specific aspects of seismic imaging during tunnelling are discussed via models that represent different cases encountered in actual tunnelling projects. These case studies demonstrate the way in which image quality along the trajectory of the TBM is improved over that in traditional settings. In this way, the risks associated with the tunnelling process can be more accurately assured.

  20. Oklahoma seismic network. Final report

    SciTech Connect

    Luza, K.V.; Lawson, J.E. Jr. |

    1993-07-01

    The US Nuclear Regulatory Commission has established rigorous guidelines that must be adhered to before a permit to construct a nuclear-power plant is granted to an applicant. Local as well as regional seismicity and structural relationships play an integral role in the final design criteria for nuclear power plants. The existing historical record of seismicity is inadequate in a number of areas of the Midcontinent region because of the lack of instrumentation and (or) the sensitivity of the instruments deployed to monitor earthquake events. The Nemaha Uplift/Midcontinent Geophysical Anomaly is one of five principal areas east of the Rocky Mountain front that has a moderately high seismic-risk classification. The Nemaha uplift, which is common to the states of Oklahoma, Kansas, and Nebraska, is approximately 415 miles long and 12-14 miles wide. The Midcontinent Geophysical Anomaly extends southward from Minnesota across Iowa and the southeastern corner of Nebraska and probably terminates in central Kansas. A number of moderate-sized earthquakes--magnitude 5 or greater--have occurred along or west of the Nemaha uplift. The Oklahoma Geological Survey, in cooperation with the geological surveys of Kansas, Nebraska, and Iowa, conducted a 5-year investigation of the seismicity and tectonic relationships of the Nemaha uplift and associated geologic features in the Midcontinent. This investigation was intended to provide data to be used to design nuclear-power plants. However, the information is also being used to design better large-scale structures, such as dams and high-use buildings, and to provide the necessary data to evaluate earthquake-insurance rates in the Midcontinent.

  1. Application of Neutral Networks to Seismic Signal Discrimination

    DTIC Science & Technology

    1993-05-15

    seismic classifications include [26,27]: Table 1 Seismic Event Classifications Natural events: tectonic volcanic collapse earthquakes ocean...classification of seismic events. This classification involves discriminating between natural seismic events such as tectonic, volcanic and collapse...movement, volcanic activity, collapse earthquakes, and oceanic microseisms. Man made seismic events can be the result of a controlled event or that of an

  2. Seismicity of Afghanistan and vicinity

    USGS Publications Warehouse

    Dewey, James W.

    2006-01-01

    This publication describes the seismicity of Afghanistan and vicinity and is intended for use in seismic hazard studies of that nation. Included are digital files with information on earthquakes that have been recorded in Afghanistan and vicinity through mid-December 2004. Chapter A provides an overview of the seismicity and tectonics of Afghanistan and defines the earthquake parameters included in the 'Summary Catalog' and the 'Summary of Macroseismic Effects.' Chapter B summarizes compilation of the 'Master Catalog' and 'Sub-Threshold Catalog' and documents their formats. The 'Summary Catalog' itself is presented as a comma-delimited ASCII file, the 'Summary of Macroseismic Effects' is presented as an html file, and the 'Master Catalog' and 'Sub-Threshold Catalog' are presented as flat ASCII files. Finally, this report includes as separate plates a digital image of a map of epicenters of earthquakes occurring since 1964 (Plate 1) and a representation of areas of damage or strong shaking from selected past earthquakes in Afghanistan and vicinity (Plate 2).

  3. Martian seismicity. [from Viking data

    NASA Technical Reports Server (NTRS)

    Goins, N. R.; Lazarewicz, A. R.

    1979-01-01

    During the Viking mission to Mars, the seismometer on Lander II collected approximately 0.24 earth years of observational data, excluding periods of time dominated by wind-induced Lander vibration. The 'quiet-time' data set contains no confirmed seismic events. A proper assessment of the significance of this fact requires quantitative estimates of the expected detection rate of the Viking seismometer. The first step is to calculate the minimum magnitude event detectable at a given distance, including the effects of geometric spreading, anelastic attenuation, seismic signal duration, seismometer frequency response, and possible poor ground coupling. Assuming various numerical quantities and a Martian seismic activity comparable to that of intraplate earthquakes, the appropriate integral gives an expected annual detection rate of 10 events, nearly all of which are local. Thus only two to three events would be expected in the observational period presently on hand and the lack of observed events is not in gross contradiction to reasonable expectations. Given the same assumptions, a seismometer 20 times more sensitive than the present instrument would be expected to detect about 120 events annually.

  4. Building a Smartphone Seismic Network

    NASA Astrophysics Data System (ADS)

    Kong, Q.; Allen, R. M.

    2013-12-01

    We are exploring to build a new type of seismic network by using the smartphones. The accelerometers in smartphones can be used to record earthquakes, the GPS unit can give an accurate location, and the built-in communication unit makes the communication easier for this network. In the future, these smartphones may work as a supplement network to the current traditional network for scientific research and real-time applications. In order to build this network, we developed an application for android phones and server to record the acceleration in real time. These records can be sent back to a server in real time, and analyzed at the server. We evaluated the performance of the smartphone as a seismic recording instrument by comparing them with high quality accelerometer while located on controlled shake tables for a variety of tests, and also the noise floor test. Based on the daily human activity data recorded by the volunteers and the shake table tests data, we also developed algorithm for the smartphones to detect earthquakes from daily human activities. These all form the basis of setting up a new prototype smartphone seismic network in the near future.

  5. Martian seismicity. [from Viking data

    NASA Technical Reports Server (NTRS)

    Goins, N. R.; Lazarewicz, A. R.

    1979-01-01

    During the Viking mission to Mars, the seismometer on Lander II collected approximately 0.24 earth years of observational data, excluding periods of time dominated by wind-induced Lander vibration. The 'quiet-time' data set contains no confirmed seismic events. A proper assessment of the significance of this fact requires quantitative estimates of the expected detection rate of the Viking seismometer. The first step is to calculate the minimum magnitude event detectable at a given distance, including the effects of geometric spreading, anelastic attenuation, seismic signal duration, seismometer frequency response, and possible poor ground coupling. Assuming various numerical quantities and a Martian seismic activity comparable to that of intraplate earthquakes, the appropriate integral gives an expected annual detection rate of 10 events, nearly all of which are local. Thus only two to three events would be expected in the observational period presently on hand and the lack of observed events is not in gross contradiction to reasonable expectations. Given the same assumptions, a seismometer 20 times more sensitive than the present instrument would be expected to detect about 120 events annually.

  6. Seismic risk mapping for Germany

    NASA Astrophysics Data System (ADS)

    Tyagunov, S.; Grünthal, G.; Wahlström, R.; Stempniewski, L.; Zschau, J.

    2006-06-01

    The aim of this study is to assess and map the seismic risk for Germany, restricted to the expected losses of damage to residential buildings. There are several earthquake prone regions in the country which have produced Mw magnitudes above 6 and up to 6.7 corresponding to observed ground shaking intensity up to VIII-IX (EMS-98). Combined with the fact that some of the earthquake prone areas are densely populated and highly industrialized and where therefore the hazard coincides with high concentration of exposed assets, the damaging implications from earthquakes must be taken seriously. In this study a methodology is presented and pursued to calculate the seismic risk from (1) intensity based probabilistic seismic hazard, (2) vulnerability composition models, which are based on the distribution of residential buildings of various structural types in representative communities and (3) the distribution of assets in terms of replacement costs for residential buildings. The estimates of the risk are treated as primary economic losses due to structural damage to residential buildings. The obtained results are presented as maps of the damage and risk distributions. For a probability level of 90% non-exceedence in 50 years (corresponding to a mean return period of 475 years) the mean damage ratio is up to 20% and the risk up to hundreds of millions of euro in the most endangered communities. The developed models have been calibrated with observed data from several damaging earthquakes in Germany and the nearby area in the past 30 years.

  7. Climate-vegetation-fire linkages on decadal-to-millennial time scales along the Patagonian forest-steppe ecotone (41 - 43°S)

    NASA Astrophysics Data System (ADS)

    Iglesias, V.; Whitlock, C. L.

    2013-12-01

    Patagonian vegetation has dramatically changed in composition and distribution over the last 16,000 years. Although patterns of vegetation change are relatively clear, our understanding of the processes that produce them is limited. In this study, we reconstructed the vegetation and fire history of the North Patagonian forest-steppe ecotone (41 - 43°S) and linked past ecological changes to variations in large-scale synoptic controls of climate and past human activity. Postglacial vegetation and fire dynamics were inferred from high-resolution pollen and charcoal records from seven lakes located along the forest-steppe ecotone in the eastern flanks of the Andes. We fit Mixed Generalized Additive Models to these time series to estimate regional trends in vegetation composition and biomass burning through time, and compared them with independent paleoclimate data so as to assess long-term vegetation-fire-climate linkages. Pollen data indicate that late-glacial steppe was replaced by open forest in the early Holocene and by closed forest in the middle and late Holocene. Fire activity was lowest during the late-glacial to early-Holocene transition and gradually increased through the Holocene. Long-term vegetation and fire patterns responded to variations in seasonal and annual insolation and their effect on moisture during the growing season. Submillennial-scale precipitation variability explained much of the fine-scale ecotonal behavior, mainly through its effect on fire, which can amplify or override the direct influence of climate on ecotone composition. During the late Holocene, in particular, century-long oscillations in forest composition were largely driven by changes in humidity, associated with the strengthening of the westerlies and ENSO variability. Humid periods (4900-3800 cal yr BP, 2850-1350 cal yr BP) promoted Nothofagus forest, and dry times (3800-2850 cal yr BP, 1350-450 cal yr BP) favored Austrocedrus expansion. At intermediate moisture levels

  8. Trace-element and Sr, Nd, Pb, and O isotopic composition of Pliocene and Quaternary alkali basalts of the Patagonian Plateau lavas of southernmost South America

    USGS Publications Warehouse

    Stern, C.R.; Frey, F.A.; Futa, K.; Zartman, R.E.; Peng, Z.; Kurtis, Kyser T.

    1990-01-01

    The Pliocene and Quaternary Patagonian alkali basalts of southernmost South America can be divided into two groups. The "cratonic" basalts erupted in areas of Cenozoic plateau volcanism and continental sedimentation and show considerable variation in 87Sr/86Sr (0.70316 to 0.70512), 143Nd/144Nd (e{open}Nd) and 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios (18.26 to 19.38, 15.53 to 15.68, and 38.30 to 39.23, respectively). These isotopic values are within the range of oceanic island basalts, as are the Ba/La, Ba/Nb, La/Nb, K/Rb, and Cs/Rb ratios of the "cratonic" basalts. In contrast, the "transitional" basalts, erupted along the western edge of the outcrop belt of the Pliocene and Quaternary plateau lavas in areas that were the locus of earlier Cenozoic Andean orogenic arc colcanism, have a much more restricted range of isotopic composition which can be approximated by 87Sr/86Sr=0.7039??0.0004, e{open}Nd, 206Pb/204Pb=18.60??0.08, 207Pb/204Pb=15.60??0.01, and 208Pb/204Pb=38.50??0.10. These isotopic values are similar to those of Andean orogenic are basalts and, compared to the "cratonic" basalts, are displaced to higher 87Sr/86Sr at a given 143Nd/144Nd and to higher 207Pb/204Pb at a given 208Pb/204Pb. The "transitional" basalts also have Ba/La, Ba/Nb, La/Nb, and Cs/Rb ratios higher than the "cratonic" and oceanic island basalts, although not as high as Andean orogenic are basalts. In contrast to the radiogenic isotopes, ??18O values for both groups of the Patagonian alkali basalts are indistinguishable and are more restricted than the range reported for Andean orogenic are basalts. Whole rock ??18O values calculated from mineral separates for both groups range from 5.3 to 6.5, while measured whole rock ??18O values range from 5.1 to 7.8. The trace element and isotopic data suggest that decreasing degrees of partial melting in association with lessened significance of subducted slabderived components are fundamental factors in the west to east transition from arc

  9. The Formation of a Retroarc Fold-Thrust Belt by the Closure and Inversion of a Back-Arc Basin; Patagonian-Fuegian Fold-Thrust Belt, Chile

    NASA Astrophysics Data System (ADS)

    Betka, P.; Klepeis, K. A.; Mosher, S.

    2012-12-01

    The Late Cretaceous closure and inversion of the Late Jurassic Rocas Verdes back-arc basin (RVB) defines the onset of the Andean orogeny and the development of the Patagonian retroarc fold-thrust belt (FTB) between 50°-54.5° S. Back-arc extension in the RVB led to the generation of new oceanic crust that was coeval with the deposition of syn-rift silicic volcanoclastic rocks on the continental margin. A > 500 m thick succession of mudstone and distal turbidite deposits accumulated in the RVB (post-rift). New maps and line-balanced cross-sections from three transects across the FTB show a transition through time from thin-to thick-skinned structural styles that is controlled by the inherited stratigraphic architecture and structure of the RVB. The closure of the RVB and development of the FTB occurred in two stages. During the initial stage, mafic schist, gabbro, basalt, and hemipelagic mudstone of the RVB floor were imbricated and thrust onto the continental margin resulting in the formation of the Magallanes foreland basin and underthrusting of the continental crust to depths of ~ 35 km. Displacement from the obduction of the RVB was transferred along two decollement levels into the FTB by ~85 Ma. Each decollement level formed at a rheological boundary within the syn- and post-rift stratigraphy. The lower decollement formed in quartz-chlorite schist (basement) > 1 km beneath the top-basement contact with relatively strong syn-rift volcanoclastic deposits. The lower decollement is defined by a ~1 km thick ductile shear zone. C-S fabrics, C-C' shear bands and prominent SW plunging quartz stretching lineations that occur within the shear zone indicate a top-NE transport direction. Isoclinal recumbent F2 folds and inclined tight F3 folds refold the S1/L1 surface. The decollement cuts up-section through the syn-rift volcanoclastic deposits to join a structurally higher decollement that formed within weak, post-rift mudstone and turbidite deposits on the continental

  10. Near-surface Fun with Seismic Data

    NASA Astrophysics Data System (ADS)

    Clapp, M.

    2015-12-01

    What is happening in the near-surface often has a direct effect on human activity. Seismic exploration has routinely targeted geology at depths of kilometers to tens of kilometers. However, these techniques can be applied to answer questions about shallower targets. Several recent experiments demonstrate seismic applicability to near-surface problems. One example is passive seismic monitoring using ambient noise to identify shallow changes and potential hazards in a producing hydrocarbon field. Another example is the use of seismic reflection data from within the water column to determine layering caused by temperature and salinity differences in depth. A third example is identifying historical elevation changes along coast lines using seismic reflection data. These examples show that exploration seismic methods can be effectively used for a variety of near-surface applications.

  11. Seismic energy release of the moon

    NASA Technical Reports Server (NTRS)

    Goins, N. R.; Dainty, A. M.; Toksoz, M. N.

    1981-01-01

    Lunar seismicity is investigated by calculating various source parameters for a number of shallow and deep-focus moonquakes. The seismic moment, seismic energy release, annual seismic energy release, stress drop, and body-wave magnitude are determined for the largest shallow moonquakes and for large deep-focus events. It is found that the shallow events dominate the lunar seismic energy release, that tidal dissipation may account for the energy release by the deep-focus events, and that the stress drops for the deep-focus events are comparable to or smaller than the calculated tidal stresses. A comparison of the results with terrestrial data indicates that the seismic characteristics of a planet are controlled more by tectonic style and state than by the relative magnitude of the driving forces.

  12. New seismic study begins in Puerto Rico

    USGS Publications Warehouse

    Tarr, A.C.

    1974-01-01

    A new seismological project is now underway in Puerto Rico to provide information needed for accurate assessment of the island's seismic hazard. The project should also help to increase understanding of the tectonics and geologic evolution of the Caribbean region. The Puerto Rico Seismic Program is being conducted by the Geological Survey with support provided by the Puerto Rico Water Resources Authority, an agency responsible for generation and distribution of electric power throughout the Commonwealth. The Program will include the installation of a network of high quality seismograph stations to monitor seismic activity on and around Puerto Rico. These stations will be distributed across the island to record the seismicity as uniformly as possible. The detection and accurate location of small earthquakes, as well as moderate magnitude shocks, will aid in mapping active seismic zones and in compiling frequency of occurrence statistics which ultimately wil be useful in seismic risk-zoning of hte island. 

  13. Reconstructing 2000 years of hydrological variation derived from laminated proglacial sediments of Lago del Desierto at the eastern margin of the South Patagonian Ice Field, Argentina

    NASA Astrophysics Data System (ADS)

    Kastner, Stephanie; Enters, Dirk; Ohlendorf, Christian; Haberzettl, Torsten; Kuhn, Gerhard; Lücke, Andreas; Mayr, Christoph; Reyss, Jean-Louis; Wastegård, Stefan; Zolitschka, Bernd

    2010-06-01

    Lago del Desierto (49°02'S, 72°51'W) is situated in the climatically sensitive area of Southern Patagonia close to the Hielo Patagonico Sur (HPS or South Patagonian Ice Field, Argentina). Next to marine records and Antarctic ice cores, this continental area is important to reveal hemispheric and global climate trends. As instrumental climate records from this region are generally short and scarce, environmental archives are the only source of long-term records of climate variations. In this study, the potential of laminated proglacial sediments from Lago del Desierto as a palaeoclimate archive is evaluated. Two parallel gravity cores (max. length 283 cm) were analysed using a multi-proxy approach. Radiometric dating ( 14C, 210Pb and 137Cs) and tephrochronology document that the sediment cover the last 2000 years. Especially in the middle part of the record, numerous turbidites make climate variations difficult to decipher. However, after exclusion of event layers changes in sedimentological, mineralogical, and geochemical parameters reveal a long-term trend of runoff variations and sediment accessibility controlled by changes in temperature and precipitation. An abrupt transition in sediment composition occurred around AD 850 and is interpreted as a change in sediment availability related to the initial exposure of formerly glaciated areas in the catchment. This striking change mirrors the onset of warmer climate conditions during the Medieval Climate Anomaly. Moreover, the Little Ice Age cooling and the subsequent 20th century warming can be traced in the sediment record corresponding to an overall trend observed for southern South America. The proglacial lacustrine sediment record of Lago del Desierto thus constitutes a link between glacier studies of the HPS and other terrestrial climate archives in a region were long, and continuous climate records are still rare.

  14. Breizacanthus aznari sp. n. (Acanthocephala: Arhythmacanthidae) from the banded cusk-eel Raneya brasiliensis (Ophidiiformes: Ophidiidae) from the Patagonian coast in Argentina.

    PubMed

    Hernández-Orts, Jesús Servando; Alama-Bermejo, Gema; Alberto Crespo, Enrique; Anibal García, Néstor; Antonio Raga, Juan; Esteban Montero, Francisco

    2012-12-01

    Breizacanthus aznari sp. n. is described from the banded cusk-eel Raneya brasiliensis (Kaup) (Ophidiiformes: Ophidiidae) from the Patagonian coast in Argentina. Breizacanthus Golvan, 1969 is currently composed of five species (including the new species) and is characterised by the absence of trunk spines; a short cylindrical proboscis with two types of hooks and lemnisci longer than the proboscis receptacle. Breizacanthus aznari is clearly distinguished from B. chabaudi Golvan, 1969 by having 12 longitudinal rows of hooks on the proboscis, instead of 16-18. The new species resembles B. golvani Gaevskaya et Shukhgalter, 1984, B. irenae Golvan, 1969, and B. ligur Paggi, Orecchia et Della Seta, 1975, all possessing 12 longitudinal rows of hooks. However, B. aznari differs from B. golvani in having 4-5 large hooks per row (vs. 8-9) and larger eggs. The new species can be distinguished from B. irenae by the shorter body size of females, the different range of numbers of large hooks of males (4-5 and 5-6, respectively), the smaller maximum number of small hooks of females (3 and 4, respectively), and the shorter lemnisci. Breizacanthus aznari differs from B. ligur by the smaller body length of females, the smaller maximum body length of males, the different range of numbers of large hooks of males (4-5 and 5-6, respectively), and smaller lemnisci. This is the first record of a species of Breizacanthus from fishes of the order Ophidiiformes and from the Southern Hemisphere. Comparative data on species of Euzetacanthus Golvan et Houlin, 1964 and Breizacanthus are also provided.

  15. Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47°S), Chile

    NASA Astrophysics Data System (ADS)

    Georgieva, Viktoria; Melnick, Daniel; Schildgen, Taylor F.; Ehlers, Todd A.; Lagabrielle, Yves; Enkelmann, Eva; Strecker, Manfred R.

    2016-06-01

    The subduction of bathymetric anomalies at convergent margins can profoundly affect subduction dynamics, magmatism, and the structural and geomorphic evolution of the overriding plate. The Northern Patagonian Icefield (NPI) is located east of the Chile Triple Junction at ~47°S, where the Chile Rise spreading center collides with South America. This region is characterized by an abrupt increase in summit elevations and relief that has been controversially debated in the context of geodynamic versus glacial erosion effects on topography. Here we present geomorphic, thermochronological, and structural data that document neotectonic activity along hitherto unrecognized faults along the flanks of the NPI. New apatite (U-Th)/He bedrock cooling ages suggest faulting since 2-3 Ma. We infer the northward translation of an ~140 km long fore-arc sliver -- the NPI block -- results from enhanced partitioning of oblique plate convergence due to the closely spaced collision of three successive segments of the Chile Rise. In this model, greater uplift occurs in the hanging wall of the Exploradores thrust at the northern leading edge of the NPI block, whereas the Cachet and Liquiñe-Ofqui dextral faults decouple the NPI block along its eastern and western flanks, respectively. Localized extension possibly occurs at its southern trailing edge along normal faults associated with margin-parallel extension, tectonic subsidence, and lower elevations along the Andean crest line. Our neotectonic model provides a novel explanation for the abrupt topographic variations inland of the Chile Triple Junction and emphasizes the fundamental effects of local tectonics on exhumation and topographic patterns in this glaciated landscape.

  16. Butyltins, polyaromatic hydrocarbons, organochlorine pesticides, and polychlorinated biphenyls in sediments and bivalve mollusks in a mid-latitude environment from the Patagonian coastal zone.

    PubMed

    Commendatore, Marta G; Franco, Marcos A; Gomes Costa, Patricia; Castro, Italo B; Fillmann, Gilberto; Bigatti, Gregorio; Esteves, José L; Nievas, Marina L

    2015-12-01

    Butyltins (BTs), polyaromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) were assessed in a mid-latitude environment of the Patagonian coast, distant from significant pollutant sources. Bioaccumulation processes through bottom sediment resuspension were suggested by BTs level (expressed as ng of tin [Sn] g(-1) dry wt) found in surface sediment (

  17. Geochemical processes controlling the distribution and concentration of metals in soils from a Patagonian (Argentina) salt marsh affected by mining residues.

    PubMed

    Idaszkin, Yanina L; Alvarez, María Del Pilar; Carol, Eleonora

    2017-10-15

    Heavy metal pollution that affects salt marshes is a major environmental concern due to its toxic nature, persistence, and potential risk to organisms and to human health. Mining waste deposits originated four decades ago, by the metallurgical extraction of heavy metals, are found near to the San Antonio salt marsh in Patagonia. The aim of the work was to determine the geochemical processes that control the distribution and concentration of Cu, Fe, Pb and Zn in the soils of this Patagonian salt marsh. A survey of the mining waste deposits was carried out where three dumps were identified. Samples were collected to determine soil texture, Eh pH, organic matter and metal contents and the soil mineralogical composition. The results shows that the soils developed over the mining waste deposits are predominantly reddish constituted mainly by iron oxide, hydroxide and highly soluble minerals such as Zn and Cu sulphates. The drainage from these deposits tends to move towards the salt marsh. Within the salt marsh, the highest concentrations of Cu, Pb and Zn occur in the sectors closest to the mining wastes deposits. The sulphide oxidation and the dissolution of the Cu, Pb and Zn sulphates could be the mainly source of these metals in the drainage water. The metals in solution that reach the salt marsh, are adsorbed by the organic matter and the fine fraction of the soils. These adsorbed metals are then remobilized by tides in the lower sectors of the marsh by desorption from the cations present in the tidal flow. On the other hand, Fe tends to form non soluble oxides, hydroxides and sulphates which remain as altering material within the mining waste deposit. Finally, the heavy metal pollutants recorded in the San Antonio salt marsh shows that the mining waste deposits that were abandoned four decades ago are still a source metal contamination. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Climate variability reflected by tree-ring width and δ18O in a heavily glaciated area of the Patagonian Andes since the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Meier, W. J. H.; Wernicke, J., Jr.; Braun, M.; Aravena, J. C.; Jaña, R.; Griessinger, J.

    2016-12-01

    Since the end of the Little Ice Age, the area of the Northern and Southern Patagonian ice sheet decreased by more than 14% and 11%, respectively. The melting increased since the last decade by 2.3%. The glaciers of Cordillera Darwin recorded a surface decrease of approximately 14% for the last 140 years. The reason for the excessive glacial change is often explained through the rise in temperature combined with a decrease in precipitation or a change in seasonality. Since a spatially coherent coverage of climatological measurement is lacking it is not possible to verify this assumption in a differentiated manner. Hence, the German- Chilean joint project "Responses of GlAciers, Biosphere and hYdrology to climate Variability and climate chAnge across the Southern Andes (GABY-VASA)" aims to determine the influence of long and short term climate variabilities (El Niño-Southern Oscillation (ENSO), Southern Hemisphere Annular Mode (SAM)) on the cryo- and biosphere. Trees growing at the glacier margins and at the natural treeline were sampled at four different locations ranging from the humid western part of the southern Andes (annual precipitation > 10.000mma-1) to the distinct dryer eastern part (annual precipitation < 500mma-1). Besides the tree-ring width based temperature reconstruction the precipitation variability reflected by δ18O in tree-rings is a promising approach to obtain detailed information of small-scaled hydro climatic conditions. Furthermore the use of δ18O as a proxy in combination with tree-ring width offers the opportunity of meteorological back trajectories and the derivation of air masses since the Little Ice Age. It thus interlinks past and present climate and allows to draw conclusions about the driving forces of glacial change.

  19. Description of plerocerci and adults of a new species of Grillotia (Cestoda: Trypanorhyncha) in teleosts and elasmobranchs from the Patagonian shelf off Argentina.

    PubMed

    Menoret, Adriana; Ivanov, Verónica A

    2012-12-01

    A new species of Grillotia was found from teleosts and elasmobranchs along the Patagonian shelf off Argentina. Grillotia patagonica n. sp. is described from plerocerci recovered from gadiform (Moridae) and perciform fish (Cheilodactylidae, Bovichtidae, and Nototheniidae) and adults from the smallthorn sand skate Psammobatis rudis (Rajiformes, Rajidae). Grillotia patagonica most closely resembles species in the Grillotia erinaceus species complex (viz., Grillotia borealis, Grillotia brayi, Grillotia dollfusi, G. erinaceus, and Grillotia musculara) in having 4 hooks per principal row and 2 or more intercalary rows in the metabasal region, a band of hooks on the external surface of the tentacle, numerous proglottids, a hermaphroditic sac, internal and external seminal vesicles, uterine pore, and attachment of the retractor muscle in the mid region of the tentacular bulb. Grillotia patagonica n. sp. is unique among all valid species in the genus by having the hooks on the first row reduced and of a different shape from the rest of the metabasal rows. Despite the diversity of elasmobranchs that are available as definitive hosts for species in Grillotia, most species (10/14) are oioxenous or mesostenoxenous. The specificity for the last intermediate host is variable among species of Grillotia, with most plerocerci being oioxenous (5/15) or euryxenous (8/15). Host specificity is higher for the adult stage in the definitive host (mean HS(S) = 4.07) than for the plerocerci (mean HS(S) = 7.30). All the species with oioxenous specificity (either larvae or adults) have limited geographic distributions. Some previous records of species of Grillotia from fishes caught off Argentina require reconsideration, i.e., G. erinaceus, Grillotia minuta (reported as Grillotia bothridiopunctata) and G. borealis . An updated host-parasite checklist for the valid species of Grillotia is also presented along with new host records for Grillotia carvajalregorum.

  20. Spatial overlap of Black-browed albatrosses with longline and trawl fisheries in the Patagonian Shelf during the non-breeding season

    NASA Astrophysics Data System (ADS)

    Copello, Sofía; Seco Pon, Juan Pablo; Favero, Marco

    2014-05-01

    Incidental mortality in fisheries is the main at-sea threat albatrosses are facing nowadays. In this study we used remote sensing techniques to model the degree of spatial overlapping between the Black-browed albatross (Thalassarche melanophris) and Argentine fisheries, assuming this as a proxy of risk for albatrosses. Eleven tags were deployed on albatrosses during the non-breeding seasons 2011 and 2012 in the Patagonian Shelf. Their distribution overlapped to different extents with the two coastal trawl, three offshore trawl and one demersal longline fisheries. The overlap index showed highest values with both coastal fleets, followed by the ice-chilling trawl fleet. These intersections were located in the Argentinean-Uruguayan Common Fishing Zone, in coastal areas of the SE of Buenos Aires province, El Rincón estuary and over the shelf break. The analysis of intersections of focal areas from albatrosses and all fisheries allowed the identification of thirty-four fishing management units (1° by 1° grid within the Argentine EEZ) classified as of medium, high or very high conservation priority. Very high priority units were placed between 35 and 38°S in the external mouth of Rio de la Plata, and between 45 and 47°S in neighboring waters East to the hake fishing closure. Although there were possible biases due to the limited number of tracked birds and the locations where albatrosses were captured and instrumented, the information presented in this study provides a comprehensive picture of important areas of overlapping during winter that could be used by the fishery administration to prioritize conservation actions under limited resource scenarios.

  1. Regional Seismic Intensity Anomalies in the Korean Peninsula and Its Implications for Seismic-Hazard Potentials

    NASA Astrophysics Data System (ADS)

    Park, Seongjun; Hong, Tae-Kyung

    2017-07-01

    The strength of seismic ground motion is a consequence of seismic source strength and medium response. The dependence of seismic amplitudes and seismic intensity on regional geological structures and crustal properties in the stable intraplate region around the Korean Peninsula is investigated. An instrumental seismic intensity scale based on spectral accelerations are proposed after calibrating with the reported macroseismic intensities. A representative seismic intensity attenuation curve for the Korean Peninsula is given by I(M_{ {L}},l,h) = -0.998 (± 0.222) + 1.72 (± 0.04) M_{ {L}} - 0.322 (± 0.027) {ln}(l^2 + h^2) - 0.00608 (± 0.00049) √{l^2 + h^2}, where I(M_{ {L}},l,h) is the seismic intensity at an epicentral distance l in km for an earthquake with local magnitude M_{ {L}} and focal depth h in km. Seismic intensities decay slowly with distance in the Korean Peninsula. The observed decay rate for the Korean Peninsula is comparable with those for other stable intraplate regions, while are lower than those for active regions. The regional seismic intensity anomalies present a characteristic correlation with geological structures. Positive seismic intensity anomalies appear in the Yeongnam massif, Okcheon belt and Gyeongsang basin, while negative seismic intensity anomalies in the Gyeonggi massif. The regional seismic intensity anomalies display positive correlations with crustal thicknesses, crustal amplifications, and seismicity density and negative correlations with heat flows. Positive seismic intensity anomalies are observed in the Yeongnam massif and Gyeongsang basin, suggesting high seismic-hazard potentials in the regions. The regional crustal properties may provide useful information on potential seismic hazards.

  2. LANL seismic screening method for existing buildings

    SciTech Connect

    Dickson, S.L.; Feller, K.C.; Fritz de la Orta, G.O.

    1997-01-01

    The purpose of the Los Alamos National Laboratory (LANL) Seismic Screening Method is to provide a comprehensive, rational, and inexpensive method for evaluating the relative seismic integrity of a large building inventory using substantial life-safety as the minimum goal. The substantial life-safety goal is deemed to be satisfied if the extent of structural damage or nonstructural component damage does not pose a significant risk to human life. The screening is limited to Performance Category (PC) -0, -1, and -2 buildings and structures. Because of their higher performance objectives, PC-3 and PC-4 buildings automatically fail the LANL Seismic Screening Method and will be subject to a more detailed seismic analysis. The Laboratory has also designated that PC-0, PC-1, and PC-2 unreinforced masonry bearing wall and masonry infill shear wall buildings fail the LANL Seismic Screening Method because of their historically poor seismic performance or complex behavior. These building types are also recommended for a more detailed seismic analysis. The results of the LANL Seismic Screening Method are expressed in terms of separate scores for potential configuration or physical hazards (Phase One) and calculated capacity/demand ratios (Phase Two). This two-phase method allows the user to quickly identify buildings that have adequate seismic characteristics and structural capacity and screen them out from further evaluation. The resulting scores also provide a ranking of those buildings found to be inadequate. Thus, buildings not passing the screening can be rationally prioritized for further evaluation. For the purpose of complying with Executive Order 12941, the buildings failing the LANL Seismic Screening Method are deemed to have seismic deficiencies, and cost estimates for mitigation must be prepared. Mitigation techniques and cost-estimate guidelines are not included in the LANL Seismic Screening Method.

  3. Hierarchical Bayesian Approach to Locating Seismic Events

    SciTech Connect

    Johannesson, G; Myers, S C; Hanley, W G

    2005-11-09

    We propose a hierarchical Bayesian model for conducting inference on the location of multiple seismic events (earthquakes) given data on the arrival of various seismic phases to sensor locations. The model explicitly accounts for the uncertainty associated with a theoretical seismic-wave travel-time model used along with the uncertainty of the arrival data. Posterior inferences is carried out using Markov chain Monte Carlo (MCMC).

  4. New Methodology for Rapid Seismic Risk Assessment

    NASA Astrophysics Data System (ADS)

    Melikyan, A. E.; Balassanian, S. Y.

    2002-05-01

    Seismic risk is growing worldwide and is, increasingly, a problem of developing countries. Along with growing urbanization future earthquakes will have more disastrous social and economic consequences. Seismic risk assessment and reduction are important goals for each country located in seismically active zone. For Armenia these goals are of primary importance because the results of studies carried out by Armenian NSSP for assessment of the losses caused by various types of disasters in Armenia had shown that earthquakes are the most disastrous hazard for Armenia. The strategy for seismic risk reduction in 1999 was adopted by the Government of Armenia as a high priority state program. The world experience demonstrates that for efficient response the rapid assessment of seismic losses is necessary. There are several state-of-the-art approaches for seismic risk assessment (Radius, Hazus, etc.). All of them required large amount of various input data, which is impossible to collect in many developing countries, in particular in Armenia. Taking into account this very serious problem existing for developing countries, as well as rapid seismic risk assessment need immediately after strong earthquake the author undertake the attempt to contribute into a new approach for rapid seismic risk assessment under the supervision of Prof. S. Balassanian. The analysis of numerous factors influencing seismic risk in Armenia shows that the following elements contribute most significantly to the possible losses: seismic hazard; density of population; vulnerability of structures. Proposed approach for rapid seismic risk assessment based on these three factors has been tested for several seismic events. These tests have shown that such approach might represent from 80 to 90 percent of real losses.

  5. Seismic Velocity Models for Western Alluvial Basins.

    DTIC Science & Technology

    1981-05-05

    indicate that local seismic wave propagation in the Basin and Range Province cannot be modeled adequately using the typical simplifying assump- tions...requires models of the geologic structure (Received for publication 5 May 1981) 5 through which the seismic waves will pass. In the following report...sharp velocity contrasts in three dimensions, are expected to have significant effects on the characteristics of local seismic wave propagation. MX

  6. Investigating the Origin of Seismic Swarms

    NASA Astrophysics Data System (ADS)

    Govoni, Aladino; Passarelli, Luigi; Braun, Thomas; Maccaferri, Francesco; Moretti, Milena; Lucente, Francesco Pio; Rivalta, Eleonora; Cesca, Simone; Hainzl, Sebastian; Woith, Heiko; De Gori, Pasquale; Dahm, Torsten; Chiarabba, Claudio; Margheriti, Lucia

    2013-10-01

    According to the U.S. Geological Survey's Earthquake Hazards Program, a seismic swarm is "a localized surge of earthquakes, with no one shock being conspicuously larger than all other shocks of the swarm. They might occur in a variety of geologic environments and are not known to be indicative of any change in the long-term seismic risk of the region in which they occur" (http://vulcan.wr.usgs.gov/Glossary/Seismicity/description_earthquakes.html).

  7. Coherent Waves in Seismic Researches

    NASA Astrophysics Data System (ADS)

    Emanov, A.; Seleznev, V. S.

    2013-05-01

    Development of digital processing algorithms of seismic wave fields for the purpose of useful event picking to study environment and other objects is the basis for the establishment of new seismic techniques. In the submitted paper a fundamental property of seismic wave field coherence is used. The authors extended conception of coherence types of observed wave fields and devised a technique of coherent component selection from observed wave field. Time coherence and space coherence are widely known. In this paper conception "parameter coherence" has been added. The parameter by which wave field is coherent can be the most manifold. The reason is that the wave field is a multivariate process described by a set of parameters. Coherence in the first place means independence of linear connection in wave field of parameter. In seismic wave fields, recorded in confined space, in building-blocks and stratified mediums time coherent standing waves are formed. In prospecting seismology at observation systems with multiple overlapping head waves are coherent by parallel correlation course or, in other words, by one measurement on generalized plane of observation system. For detail prospecting seismology at observation systems with multiple overlapping on basis of coherence property by one measurement of area algorithms have been developed, permitting seismic records to be converted to head wave time sections which have neither reflected nor other types of waves. Conversion in time section is executed on any specified observation base. Energy storage of head waves relative to noise on basis of multiplicity of observation system is realized within area of head wave recording. Conversion on base below the area of wave tracking is performed with lack of signal/noise ratio relative to maximum of this ratio, fit to observation system. Construction of head wave time section and dynamic plots a basis of automatic processing have been developed, similar to CDP procedure in method of

  8. Causality between expansion of seismic cloud and maximum magnitude of induced seismicity in geothermal field

    NASA Astrophysics Data System (ADS)

    Mukuhira, Yusuke; Asanuma, Hiroshi; Ito, Takatoshi; Häring, Markus

    2016-04-01

    Occurrence of induced seismicity with large magnitude is critical environmental issues associated with fluid injection for shale gas/oil extraction, waste water disposal, carbon capture and storage, and engineered geothermal systems (EGS). Studies for prediction of the hazardous seismicity and risk assessment of induced seismicity has been activated recently. Many of these studies are based on the seismological statistics and these models use the information of the occurrence time and event magnitude. We have originally developed physics based model named "possible seismic moment model" to evaluate seismic activity and assess seismic moment which can be ready to release. This model is totally based on microseismic information of occurrence time, hypocenter location and magnitude (seismic moment). This model assumes existence of representative parameter having physical meaning that release-able seismic moment per rock volume (seismic moment density) at given field. Seismic moment density is to be estimated from microseismic distribution and their seismic moment. In addition to this, stimulated rock volume is also inferred by progress of microseismic cloud at given time and this quantity can be interpreted as the rock volume which can release seismic energy due to weakening effect of normal stress by injected fluid. Product of these two parameters (equation (1)) provide possible seismic moment which can be released from current stimulated zone as a model output. Difference between output of this model and observed cumulative seismic moment corresponds the seismic moment which will be released in future, based on current stimulation conditions. This value can be translated into possible maximum magnitude of induced seismicity in future. As this way, possible seismic moment can be used to have feedback to hydraulic stimulation operation in real time as an index which can be interpreted easily and intuitively. Possible seismic moment is defined as equation (1), where D

  9. Seismic reflection imaging of shallow oceanographic structures

    NASA Astrophysics Data System (ADS)

    Piété, Helen; Marié, Louis; Marsset, Bruno; Thomas, Yannick; Gutscher, Marc-André

    2013-05-01

    Multichannel seismic (MCS) reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure. However, the shallowest layers of the water column (z < 150 m) have remained unexplored by this technique until recently. In order to explore the feasibility of shallow seismic oceanography (SO), we reprocessed and analyzed four multichannel seismic reflection sections featuring reflectors at depths between 10 and 150 m. The influence of the acquisition parameters was quantified. Seismic data processing dedicated to SO was also investigated. Conventional seismic acquisition systems were found to be ill-suited to the imaging of shallow oceanographic structures, because of a high antenna filter effect induced by large offsets and seismic trace lengths, and sources that typically cannot provide both a high level of emission and fine vertical resolution. We considered a test case, the imagery of the seasonal thermocline on the western Brittany continental shelf. New oceanographic data acquired in this area allowed simulation of the seismic acquisition. Sea trials of a specifically designed system were performed during the ASPEX survey, conducted in early summer 2012. The seismic device featured: (i) four seismic streamers, each consisting of six traces of 1.80 m; (ii) a 1000 J SIG sparker source, providing a 400 Hz signal with a level of emission of 205 dB re 1 μPa @ 1 m. This survey captured the 15 m thick, 30 m deep seasonal thermocline in unprecedented detail, showing images of vertical displacements most probably induced by internal waves.

  10. Nationwide Assessment of Seismic Hazard for Georgia

    NASA Astrophysics Data System (ADS)

    Tsereteli, N. S.; Varazanashvili, O.; Mumladze, T.

    2014-12-01

    The work presents a framework for assessment of seismic hazards on national level for the Georgia. Based on a historical review of the compilation of seismic hazard zoning maps for the Georgia became evident that there were gaps in