Science.gov

Sample records for patagonian fjordland seismic

  1. The origin and evolution of a southern Patagonian lake based on multi-channel seismic reflection methods

    NASA Astrophysics Data System (ADS)

    Beres, M.; Gilli, A.; Ariztegui, D.; Anselmetti, F. S.

    2003-04-01

    As part of an ongoing study of interhemispheric correlations in climate change, 65^o km of multi-channel seismic reflection profiles were recorded with an air-gun source in the closed lake system of Lago Cardiel, Argentina (49^oS). Previous studies, using 3.5-kHz echo-sounder data, revealed six major seismic sequences throughout the lake's subsurface. Calibration of these earlier data with the dated piston-core samples permitted the reconstruction of lake levels since the late Pleistocene. The intent of using the stronger seismic source in this study was to concentrate on the deepest seismic units, Sequences V and VI, which may hold records of Pleistocene climatic conditions as well as information about the origin of the lake. Sequence VI is the oldest unit and underlies the entire lake basin. It has a parallel to wavy reflection pattern with km-scale fold wavelengths and a maximum dip of 3^o. The upper sequence boundary of Sequence VI is strongly reflective and highly irregular. A small depression, about 1 km wide and 2 km long, characterizes its deepest portion, which is over 160 ms (˜120 m) beneath the lake surface. This depression is slightly west of the lake center and oriented NNE. Sequence V unconformably overlies Sequence VI, and its extent is limited to the western part of the lake basin. It is irregular in shape and largely transparent to seismic waves, but its few internal reflections indicate an eastward progradation. The maximum thickness of Sequence V, 47 ms (˜35 m), occurs approximately in the center of the depression. Outcrops around the lake help to interpret Sequence VI as Cretaceous-Tertiary marls. Both the outcrops and the seismic profiles show fold axes that primarily strike north-south, thus indicating a generally east-west orientation of tectonic compression. Although Tertiary volcanism is widespread in the region, the nature and continuity of Sequence VI beneath the lake do not point to volcanic or impact-related origin of the lake. The

  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. 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

  5. Phylogenetic analysis of Ostreococcus virus sequences from the Patagonian Coast.

    PubMed

    Manrique, Julieta M; Calvo, Andrea Y; Jones, Leandro R

    2012-10-01

    A phylogenetic analysis of new Ostreococcus virus (OV) sequences from the Patagonian Coast, Argentina, and homologous sequences from public databases was performed. This analysis showed that the Patagonian sequences represented a divergent viral clade and that the rest of OV sequences analyzed here were clustered into six additional phylogenetic groups. Analyses of 18S gene libraries supported a close relationship of the Patagonian Ostreococcus host with clade A sequences described elsewhere, corroborating previous studies indicating that clade A strains are ubiquitous. Besides the Patagonian OV sequences, several phylogenetic groupings were linked to particular geographic locations, suggesting a role for allopatric cladogenesis in viral diversification. However, and in agreement with previous observations, other viral lineages included sequences with diverse geographic origins. These findings, together with analyses of ancestral trait trajectories performed here, are consistent with an evolutionary dynamics in which geographical isolation has a role in OV diversification but can be followed by rapid dispersion to remote places. PMID:22674355

  6. Magmatic evolution of the Austral Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Ramos, V. A.; Niemeyer, H.; Skarmeta, J.; Mun˜oz, J.

    1982-11-01

    New geological evidence and geochronological data obtained within the Patagonian Cordillera between Lat. 47° and 49°S, allow the redefinition of an Andean region with different and characteristic geological evolution compared to the adjacent segments. An acidic Middle Jurassic volcanism covered a "metamorphic basement" formed by low-grade metasediments and metabasites of Upper Paleozoic age. Dike swarms of basic alkaline rocks were emplaced since the Cretaceous in a marginal basin developed on the Jurassic sialic crust. The outcrop density of such bodies seems to indicate an attenuation of the sialic crust, towards the south, where oceanic crust of Upper Jurassic-Lower Cretaceous age floored the marginal basin. The Cretaceous volcanic activity is well developed in the adjacent sectors, but almost absent in the studied segment. Several magmatic pulses lead to the final emplacement of the Patagonian batholith which yields its peak activity around 98 m.y. and presents typical geochemical variations. The Upper Cretaceous and Cenozoic magmatism are mainly exposed to the east of the cordillera and are represented by a series of alkali plateau basalts. Different pulses of activity have been recorded during Eocene, Upper Miocene, Pliocene and even during Quaternary times, associated with deep crustal fractures and probable upper-mantle origin, as evidenced by the low 87Sr/ 86Sr ratios and the ultramafic and mafic xenoliths of the lavas. Granitic stocks in the Andean domain are post-orogenic in relation to a compressive tectonic phase during Miocene times. The Upper Cenozoic calc-alkaline volcanism presents a gap in this segment of the Andean belt, probably related with the post-Miocene migration of the Chile rise.

  7. 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.

  8. Regional lithologic variations in the Patagonian batholith

    NASA Astrophysics Data System (ADS)

    Nelson, E.; Bruce, B.; Elthon, D.; Kammer, D.; Weaver, S.

    The Patagonian batholith, in the southern Andes of Chile, represents a major addition to the Pacific margin of the South American plate due to semi-continual subduction since the Late Jurassic. Plutonic ages range from 166 to 12 Ma, with an apparent peak around 100-70 Ma. Most of the batholith is composed of I-type, metaluminous, calc-alkaline rocks ultimately related to partial melting of mantle wedge material and/or subducted material. Tonalite (plus minor quartz diorite) is the dominant lithology (36% of 585 samples); other lithologic groups (granite, granodiorite + quartz monzodiorite, and diorite + gabbro) make up roughly equal proportions of the samples (18-25% each). Minor amounts of peraluminous rock suggest some amount of crustal recycling (contamination of mantle magmas or melting of continental crust). Most plutons are undeformed; foliated rocks crop out in Andean orogenic zones and locally along lineaments. Local, protracted, felsic to mafic progressions are probably related to intrusion geometry and erosion level rather than evolution of a single magma. Similarities with the Coastal batholith of Peru include size, the period of intrusion (mainly Cretaceous-Tertiary), and the general I-type, tonalitic character. Differences include no unidirectional migration in time, thinner and younger pre-batholithic crust, deeper level of erosion (generally mesozonal), and significant primary biotite in mafic rocks. These differences probably reflect different mechanisms of magmatic evolution and arc construction related to subduction kinematics and crustal setting.

  9. Space Radar Image of Patagonian Ice Fields

    NASA Technical Reports Server (NTRS)

    1994-01-01

    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

  10. Geomorphology and shallow structure of a segment of the Atlantic Patagonian margin

    NASA Astrophysics Data System (ADS)

    Muñoz, A.; Acosta, J.; Cristobo, J.; Druet, M.; Uchupi, E.

    2013-06-01

    We study an area little known of the Atlantic Patagonian margin from 44°30'S to 47°40'S and from 59°W to nearly 61°W. The multi-beam bathymetry coupled with high resolution seismic reflection profiles, has provided details on the morphology and shallow acoustic structure on this area. The main morphological characteristics of the seafloor features on the shelf and middle slope are described. The Atlantic Patagonian continental shelf north of 45°40'S is located at a depth of 170-200 m, south of this latitude the shelf edge is at 128 to 200 m. The shelf surface is marred by circular depression and ridges oriented oblique to the shelf edge. The upper slope and upper middle slope are plowing by icebergs from Antarctica in Pleistocene and local reefs of cold-water coral further enhance the topography of the area. In the middle slope there are two terraces, the 20 to 60 km wide Nágera and the 15 to 60 km wide Perito Moreno terraces, showing moats, hollows, pot holes, sediment drifts and sediment waves. The terraces may have been formed in Late Miocene whereas the other forms are of Pleistocene age. Other features are a sediment swell south of 47°S and seven submarine canyons on the middle slope. These incipient canyons have been developed in the middle slope by retrogressive erosion, some terminating on the upper middle slope, and others on the upper slope and the Canyon 6 breaching the shelf edge. Individual seafloor features existing on the Atlantic Patagonian Margin have been classified into two main groups according to their origin: along and across-slope processes. These primary agents were supplemented by endogenic processes such as expulsion of gas/water, diapirism of high-pressure mud and folding/faulting. The results suggest that today down-slope processes on the slope are practically non-existent and that the morphology of the upper and middle slope is slowly being remolded by along-slope bottom currents.

  11. Modeling the Glacial Buzzsaw in the Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Brandon, M. T.; Tomkin, J. H.

    2006-12-01

    Modeling the Glacial Buzzsaw in the Patagonian Andes The concept of a "glacial buzzsaw" was spawned by Steve Porter's observation in 1977 and 1988 that the "equilibrium line altitude" (ELA) for alpine glaciation in the Andes parallels the summit elevations of the range. The modern ELA in the Patagonian Andes drops from about 4.5 km at 30 S to about 1 km at 50 S, due to colder temperatures at higher latitudes. The summit elevations decrease steadily by a similar amount over this 2200 km distance. The landscape of the western side of the Patagonian Andes clearly shows that it has long been dominated by glacial erosion. Locally preserved tills indicate that alpine glaciation was active at 7 to 4.6 Ma, if not earlier. The idea of a glacial buzzsaw is that erosion by alpine glaciers is aggressive enough to limit the height of a mountain range. Fission-track cooling ages indicate modest long-term erosion rates (~0.5 to 1 km/Ma) for the Patagonian Andes, which precludes the possibility that the range was trimmed down to size by Quaternary- age glaciations. Furthermore, the range shows clear evidence of growth by continental subduction and tectonic accretion along its eastern margin. Evidence for recent tectonic shortening is based on the observation that the range has an approximately constant taper, as expected for a critical wedge. The width of the range decreases southward in parallel with the decreasing summit elevations. We have developed a general analytical model for coupled wedge growth and glacial erosion that accounts for much of the tectonic evolution of the Patagonian Andes. The model is based on an actively accreting wedge that maintains a constant taper geometry. The size of the wedge is controlled by competition between accretion and glacial erosion. Recent work by one of us (JHT) and Gerard Roe shows that the erosional yield caused by alpine glaciation is approximately proportional to the local elevation difference between the summit of the range and the

  12. Behavior, nutrition, and veterinary care of patagonian cavies (Dolichotis patagonum).

    PubMed

    Kessler, David S; Hope, Katharine; Maslanka, Michael

    2009-05-01

    Patagonian cavies (Dolichotis patagonum) are large South American rodents well adapted for cursorial life (well adapted for running). They are monogamous but can live in groups of up to 70 individuals who maintain communal burrows. They are primarily herbivorous and may be maintained on commercially produced rodent or primate diets. Their long, thin legs and skittish nature make them difficult to restrain. Common medical problems include malocclusion of cheek teeth, gastrointestinal parasites, hypertrophic cardiomyopathy, and traumatic leg fractures. PMID:19341953

  13. Morphology of the lingual papillae in the Patagonian cavy.

    PubMed

    Emura, Shoichi; Okumura, Toshihiko; Chen, Huayue

    2011-11-01

    We examined the dorsal lingual surfaces of an adult Patagonian cavy (Dolichotis patagonum) by scanning electron microscopy. The tongue of the Patagonian cavy is about 8 cm long and the lingual body had lingual prominence on the posterior third. There were no fungiform papillae in the lingual dorsal surface. The fungiform papillae were observed in both lateral sides of the lingual apex. The filiform papilla of the lingual body consisted of a large conical papilla. The connective tissue core of the filiform papilla showed many slender processes. The fungiform papillae were round in shape. The connective tissue core of the fungiform papilla was flower-bud shaped. Two vallate papillae were located on between lingual body and root, and insert in two grooves. The connective tissue core of the vallate papilla was covered with numerous small spines. Many foliate papillae were observed on the posterolateral regions of the tongue. After removing epithelium from the foliate papillae many vertical depressions became apparent. These findings suggest that in the structure of the lingual papillae of the Patagonian cavy there is similar to that of the capybara. PMID:22519071

  14. 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

  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. 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. PMID:20140380

  17. Simple models for late Holocene and present-day Patagonian glacier fluctuations and predictions of a geodetically detectable isostatic response

    NASA Astrophysics Data System (ADS)

    Ivins, Erik R.; James, Thomas S.

    1999-09-01

    The late Holocene glacial moraine chronology in the southernmost South American Andes includes four ^1 ^4 C dated Neoglacial advances and retreats. These are used as proxy information to characterize mass fluctuation of the Patagonian icefields during the last 5000 years. Modelled ice loads force a phase-lagged viscoelastic gravitational deformation of the solid Earth. The ancient glacier fluctuations may, therefore, drive present-day crustal motion even in the absence of present-day ice mass imbalance. Numerical models show that such rates of present-day uplift and subsidence are larger than those driven by the viscous memory of late Pleistocene deglaciation. Both spherical and flat-earth models are employed, the latter being used to study exhaustively the effects of glacial load history on the predicted vertical crustal velocity. Recent assessment of net mass balance from 1944 to 1985 indicates that the Southern Patagonian icefield has significantly deteriorated due to snout retreat and thinning. Volume loss rates are estimated at about 3.4-9.3 km^3 yr^- ^1 . The predicted vertical isostatic response to this recession and to the modelled Holocene Neoglaciations is at a marginally detectable level (~1 mm yr^- ^1 ) if the mantle/asthenosphere beneath Patagonia has a viscosity of about 10^2 ^1 Pa s. However, for reduced mantle viscosities, the younger Holocene glacial load histories predict larger signatures. In fact, if the viscosity is about 2x10^2 ^0 Pa s, or lower, then geodetically detectable vertical motion may be driven by a regional Little Ice Age (LIA) (1400-1750 AD) glacier advance and subsequent 20th century retreat. Although this value for mantle viscosity is lower than thought typical of continental shield mantle (~10^2 ^1 Pa s), it is consistent with inversions for post-seismic relaxation time constants in island arc environments and in regions with significant Neogene continental tectonism. In the viscosity regime of 5x10^1 ^8 -2x10^1 ^9 Pa s, the

  18. 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. PMID:18635799

  19. 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

  20. 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.

  1. Dendrogeomorphic reconstruction of flash floods in the Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Casteller, Alejandro; Stoffel, Markus; Crespo, Sebastián; Villalba, Ricardo; Corona, Christophe; Bianchi, Emilio

    2015-01-01

    Flash floods represent a significant natural hazard in small mountainous catchments of the Patagonian Andes and have repeatedly caused loss to life and infrastructure. At the same time, however, documentary records of past events remain fairly scarce and highly fragmentary in most cases. In this study, we therefore reconstruct the spatiotemporal patterns of past flash flood activity along the Los Cipreses torrent (Neuquén, Argentina) using dendrogeomorphic methods. Based on samples from Austrocedrus chilensis, Pseudotsuga menziesii, and Nothofagus dombeyi, we document 21 flash flood events covering the period A.D. 1890-2009 and reconstruct mean recurrence intervals of events at the level of individual trees being impacted, which varies from 4 to 93 years. Results show that trees tend to be older (younger) in sectors of the torrent with gentler (steeper) slope gradients. Potential triggers of flash floods were analyzed using daily temperature and precipitation data from a nearby weather station. Weather conditions leading to flash floods are abundant precipitations during one to three consecutive days, combined with temperatures above the rain/snow threshold (2 °C) in the whole watershed.

  2. First paleoparasitological results from late Holocene in Patagonian coprolites.

    PubMed

    Beltrame, M O; Fugassa, M H; Sardella, N H

    2010-06-01

    These are the first paleoparasitological results from the Late Holocene in Patagonian coprolites. Coprolites collected from layers dated at 3,480 and 2,740 yr before present (B.P.), from the archaeological site Cerro Casa de Piedra, were examined. The site is a hill located in a forest steppe ecotone in Perito Moreno National Park. The coprolites could belong to humans or to other carnivores such as canids. After rehydration and spontaneous sedimentation of the samples, the parasite contents were examined. Results obtained showed the common presence of eggs of a Calodium sp., eggs of other capillariids and trichostrongylids, oocysts of Eimeria macusaniensis (Apicomplexa), and eggs of taeniids (Cestoda). Although the generic identification of some parasites could not be provided, the presence of tapeworm eggs represents the first record for the Late Holocene in Patagonia and shows that parasitism by cestodes existed in the region in pre-Columbian times. Results indicate that in the Late Patagonic Holocene, zoonotic helminths may have been commonly present in the inhabitants of Patagonia. The parasites found in the coprolites allow us to deduce what these people were eating and, thus, indicate what other pathogens, such as viruses, bacteria, and parasitic protozoans, may have infected them via the same sources. PMID:20557211

  3. Evidence of upwelling events at the northern Patagonian shelf break

    NASA Astrophysics Data System (ADS)

    Valla, Daniel; Piola, Alberto R.

    2015-11-01

    The Patagonian shelf break marks a transition between relative warm-fresh shelf waters and relative cold-salty Subantarctic Water advected northward by the Malvinas Current. From early spring to late autumn, the outer shelf region is characterized by a band of high chlorophyll concentration that sustains higher trophic levels, including significant fisheries. We analyze time series of current and water mass property observations collected at two moorings deployed at the shelf edge at 41°S and 43.8°S to investigate what mechanisms lead to temperature variability at the shelf break, and their role on the nutrient supply to the upper layer. The in situ data are combined with satellite-derived observations of sea surface temperature and chlorophyll a to analyze a sharp cooling event at the outer shelf that lasted 10 days and extended ˜500 km along the outer shelf. The event is consistent with upwelling of cold waters through the base of the mixed layer. The vertical velocity required to explain the observed cooling is 13-29 m d-1. Satellite-derived sea surface temperature reveals additional cooling events of similar characteristics. Seventy-five percent of these events are concurrent with surface chlorophyll increase over a 5 day period suggesting that cooling events observed at the shelf break are associated with nutrient fluxes that promote the growth of phytoplankton.

  4. Double-diffusive layering and mixing in Patagonian fjords

    NASA Astrophysics Data System (ADS)

    Pérez-Santos, Iván; Garcés-Vargas, José; Schneider, Wolfgang; Ross, Lauren; Parra, Sabrina; Valle-Levinson, Arnoldo

    2014-12-01

    Double-diffusive layering was quantified for the first time in the Chilean Patagonian fjords region (41.5-56°S). Approximately 600 temperature and salinity profiles collected during 1995-2012 were used to study water masses, quantify diffusive layering and compute the vertical diffusivity of heat. Development of 'diffusive-layering' or simply 'layering' was favored by relatively fresh-cold waters overlying salty-warm waters. Fresh waters are frequently derived from glacial melting that influences the fjord either directly or through rivers. Salty waters are associated with Modified Subantarctic (MSAAW) and Subantarctic Water (SAAW). Double-diffusive convection occurred as layering in 40% of the year-round data and as salt fingering in <1% of the time. The most vigorous layering, was found at depths between 20 and 70 m, as quantified by (a) Turner angles, (b) density ratios, and (c) heat diffusivity (with maximum values of 5 × 10-5 m2 s-1). Diffusive-layering events presented a meridional gradient with less layering within the 41-47°S northern region, relative to the southern region between 47° and 56°S. Layering occupied, on average, 27% and 56% of the water column in the northern and southern regions, respectively. Thermohaline staircases were detected with microprofile measurements in Martinez and Baker channels (48°S), showing homogeneous layers (2-4 m thick) below the pycnocline (10-40 m). Also in this area, increased vertical mixing coincided with the increased layering events. High values of Thorpe scale (LT ∼ 7 m), dissipation rate of TKE (ε = 10-5-10-3 W kg-1) and diapycnal eddy diffusivity (Kρ = 10-6-10-3 m-2 s-1) were associated with diffusive layering. Implications of these results are that diffusive layering should be taken into account, together with other mixing processes such as shear instabilities and wind-driven flows, in biological and geochemical studies.

  5. 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. PMID:26981689

  6. 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.

  7. 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.

  8. 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

  9. Cowpoxvirus infection in the Patagonian cavy (Dolichotis patagonum) emerging disease in an educational animal park the first reported case.

    PubMed

    Kik, M J L; Liu, P L; van Asten, J A M

    2006-06-01

    Generalized cowpox infection in the Patagonian cavy may represent a threat to the health of immunocompromised persons. We report the first case of cowpoxvirus infection in the Patagonian cavy in an educational animal park. The mara developed extensive pox lesions, shedding large amounts of viral particles. The ending of vaccination programmes against smallpox in the late 1970's may lead to an increase in susceptibility of humans to zoonotic poxviruses. PMID:16841565

  10. 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

  11. 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. PMID:17539428

  12. 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. PMID:25339654

  13. 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

  14. Antifungal steroidal glycosides from the patagonian starfish anasteriasminuta: structure-activity correlations.

    PubMed

    Chludil, Hugo D; Seldes, Alicia M; Maier, Marta S

    2002-02-01

    Two new sulfated steroidal hexaglycosides, anasterosides A (2) and B (3), along with the known versicoside A (1) have been isolated from the Patagonian starfish Anasterias minuta. Their structures have been elucidated by spectroscopic analysis (NMR and FABMS) and chemical transformations. Compounds 1 and 2 and the synthetic pentaglycoside 1b derived from versicoside A showed antifungal activity against the plant pathogenic fungus Cladosporium cucumerinum. Desulfation of hexaglycoside 1 rendered a totally inactive saponin. PMID:11858747

  15. Source waters for the highly productive Patagonian shelf in the southwestern Atlantic

    NASA Astrophysics Data System (ADS)

    Song, Hajoon; Marshall, John; Follows, Michael J.; Dutkiewicz, Stephanie; Forget, Gaël

    2016-06-01

    Possible nutrient sources and delivery mechanisms for the highly productive Patagonian shelf in the southwest Atlantic are identified. Using a passive tracer adjoint sensitivity experiment, we identify three source waters: waters local to the Patagonian shelf, coastal waters near the Chilean coast and the subsurface waters in the southeast Pacific. We perform a series of forward simulations of a biogeochemical model to investigate the impact of nutrient perturbations in these source regions to productivity on the Patagonian shelf. Positive nitrate perturbations from local waters have an immediate impact elevating productivity. Iron perturbations local to the shelf, however, do not change productivity because the shelf region is limited by nitrate. Additional nutrient supply from the other source regions leads to increases in productivity. We find that positive nutrient perturbations in subsurface waters in the southeast Pacific result in the largest boost of productivity over the shelf. These source waters are rich in nutrients and upwelled from the depth where light levels are so low that they cannot be consumed. Finally, we identify wintertime intense vertical mixing as the key process which draws nutrients from below 300-500 m to the surface before being delivered to the shelf.

  16. 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. PMID:22497404

  17. Dining hall at sea: feeding migrations of nektonic predators to the eastern Patagonian Shelf.

    PubMed

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

    2012-07-01

    Seasonal changes in relative abundance and biomass of nektonic predators were analysed on the eastern Patagonian Shelf and continental slope; one of the most productive large marine ecosystems of the southern hemisphere. Several migratory types were revealed for species belonging to either temperate or sub-Antarctic faunas. Despite high productivity, only a few large nektonic predators spend their entire life cycle on the eastern Patagonian Shelf and use only a small proportion of the meso-nektonic resource. Most of the resource is exploited by non-resident nektonic migrants, which move to the area from distant spawning grounds. Pelagic and demersal sharks and skates, the squid Illex argentinus, tunas and gadoids migrate to the eastern part of the Patagonian Shelf to feed at different times of the year; arriving in seasonal waves according to their life cycle and spawning seasonality. Some deepwater fishes and squid migrate onto the shelf as juveniles to harvest the resource, and then return to deepwater habitat as adults. It is hypothesized that the large biomass of meso-planktonic and meso-nektonic consumers prevents most higher-trophic level predators from establishing spawning populations in this area, as their larvae and fry would be overwhelmed by predation. Instead, the higher-trophic level predators establish spawning and nursery grounds elsewhere and arrive to feed on the meso-planktonic and meso-nektonic resources after they have outgrown their own stages of predation vulnerability. PMID:22803740

  18. 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. PMID:20618900

  19. 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

    2014-01-01

    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. PMID:24675482

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  1. Tectono-magmatic response to major convergence changes in the North Patagonian suprasubduction system; the Paleogene subduction-transcurrent plate margin transition

    NASA Astrophysics Data System (ADS)

    Aragón, Eugenio; D'Eramo, Fernando; Castro, Antonio; Pinotti, Lucio; Brunelli, Daniele; Rabbia, Osvaldo; Rivalenti, Giorgio; Varela, Ricardo; Spakman, Wim; Demartis, Manuel; Cavarozzi, Claudia E.; Aguilera, Yolanda E.; Mazzucchelli, Maurizio; Ribot, Alejandro

    2011-08-01

    The southern and central Andes reflect significant along-strike differences of tectonic activity, including shortening, alternating flat-to-normal subduction styles and magmatism. In northern Patagonia, the subduction/supra-subduction system, fore arc, arc and back arc basins developed in an extensional setting during the Paleogene. This was accompanied by landward migration of calc-alkalic magmatism which changed to synextensional bimodal volcanism of rhyolitic ignimbrites and interbedded tholeiitic and alkalic basalts. These Paleogene events occurred during a time when the Farallon-Aluk active ridge reached the South American plate, and the Farallon plate subduction was interrupted. They represent a new tectonic regime, characterized by a transcurrent plate margin. The presence in the back arc of a rigid lithospheric block of 100,000 km 2 represented by the North Patagonian Massif focused the rotation of the coastal blocks. This resulted in the development of two Paleogene extensional regions to the north and south, respectively, of the Massif and replaced the former back arc. Plate rearrangement caused by the inauguration of the Nazca plate and its regime of orthogonal subduction at the beginning of the Miocene, re-established typical calc-alkaline arc magmatism at the former upper Cretaceous arc locus. Present seismic activity in the subducted plate and tomographic modeling of p-wave velocity anomalies in the upper mantle also suggest the presence of a subduction gap that lasted for most of the Paleogene in northern Patagonia.

  2. 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.

  3. 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

  4. Tissue preservation biases in stable isotopes of fishes and molluscs from Patagonian lakes.

    PubMed

    Correa, C

    2012-11-01

    Field work commonly involves preserving samples for later use; however, most preservation methods distort stable-isotope (SI) signatures that are of interest to ecologists. Although preservation of muscle samples with table salt and rubbing alcohol affected the SI (δ(13)C and δ(15)N) of important consumers in Patagonian lakes (molluscs and fishes), variation among individuals and lakes generally exceeded that among preservation treatments. Mathematical corrections for these preservation biases are provided, and a potentially bias-free preservation by air-drying is suggested. PMID:23130701

  5. 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. PMID:15218147

  6. Cytotoxic and antifungal triterpene glycosides from the Patagonian sea cucumber Hemoiedema spectabilis.

    PubMed

    Chludil, Hugo D; Muniain, Claudia C; Seldes, Alicia M; Maier, Marta S

    2002-06-01

    Two new sulfated triterpene glycosides, hemoiedemosides A (1) and B (2), have been isolated from the Patagonian sea cucumber Hemoiedema spectabilis. Their structures have been established by a combination of spectroscopic analysis (NMR and FABMS) and chemical transformations. Both glycosides present the same aglycon and differ in the degree of sulfation of the tetrasaccharide chain. Hemoiedemoside B (2) is a new example of a small number of trisulfated triterpene glycosides from sea cucumbers belonging to the family Cucumariidae. Glycosides 1 and 2 exhibit considerable antifungal activity against the phytopathogenic fungus Cladosporium cucumerinum, while the semisynthetic desulfated derivative 1a is less active. PMID:12088428

  7. 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. PMID:26352974

  8. Seismic Ecology

    NASA Astrophysics Data System (ADS)

    Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

    The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

  9. 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

  10. Molecular detection of bioluminescent dinoflagellates in surface waters of the Patagonian shelf during early austral summer 2008.

    PubMed

    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

  11. Comparative flight morphology in queens of invasive and native Patagonian bumblebees (Hymenoptera: Bombus).

    PubMed

    Polidori, Carlo; Nieves-Aldrey, José Luis

    2015-02-01

    Since its introduction in Chile, the European Bombus terrestris L. (Hymenoptera: Apidae) has progressively reduced the abundance of the native Patagonian bumblebee, Bombus dahlbomii Guérin. Because an important cause of successful invasion of a species may depend on a potentially advantageous phenotype, we studied morphologies related to flight performance (flight muscle ratio (FMR), wing loading (WL), excess power index (EPI, which integrates FMR and WL) and wing aspect ratio (AR)) in the queens of the two species. Previous empirical studies showed that greater FMR, AR and EPI, and lower WL increase flight performance. In the Patagonian Chilean fjord where the study was carried out, B. dahlbomii was 40% heavier than B. terrestris, a difference theoretically allowing the queens of the native species to take off with heavier loads, despite the fact that the two species have virtually identical FMRs. However, FMR negatively depended on body mass at the intra-specific level. The total wing area was 35% greater in B. dahlbomii, but the difference in forewing length was only of 16%. Once taken into account the effect of body size, WL, was significantly lower in B. terrestris. AR increased with body mass and did not differ between species. EPI was weakly but significantly higher in B. terrestris. Experiments formally linking such parameters with flight performance may help to explain the observed quick and wide spread of this alien species in Patagonia in the last few years. PMID:25499798

  12. 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

  13. 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. PMID:27386563

  14. 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

  15. 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. PMID:23546829

  16. Controlling factors on productivity and size abundance distribution of phytoplankton in Patagonian fjords

    NASA Astrophysics Data System (ADS)

    Cuevas, L. A.; Iriarte, J. L.; Gonzalez, H.; Silva, N.; Vargas, C.

    2012-12-01

    Temperature and resource availability has been suggested to play an important role controlling phytoplankton size structure and productivity. Here we used five independent research cruisers covering the entire Patagonian fjords (41.5-56.0 degress latitude South) to conduct a comparative analysis between zones and to determine the importance of the controlling factors. For the entire Patagonian area phytoplankton size structure seems independent from temperature, but varies with total phytoplankton biomass and productivity. Microphytoplankton contribute with more than 80% in high productivity waters (chlorophyll-a higher than 5 μg L-1) and picophytoplankton dominates when chlorophyll-a is lower than 1 μg L-1. In addition, NO3:Si(OH)4 ratio control phytoplankton size structure, where a large decrease in Si(OH)4 from north to south Patagonia (from 20 to 0.1 mM average, respectively) seems to be a major factor of control. Major and prolonged effects expected in fjord areas, such as anthropogenic eutrophication and global warning, may modify the observed relationships leading to important changes in the phytoplankton community and its ecological role.

  17. 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.

  18. 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.

  19. Modeling Past and Future Surface Mass Balance of the Patagonian Icefields

    NASA Astrophysics Data System (ADS)

    Schaefer, M.; Casassa, G., Sr.; Machguth, H.; Falvey, M. J.

    2014-12-01

    We present surface mass balance simulations of the Patagonian Icefield that were driven by global climate data (reanalysis/GCM) which were downscaled using the regional climate model Weather Research and Forecasting (WRF) and statistical downscaling methods. The special climatic situation in the region with sharp climate gradients introduced by the blocking of the westerlies by the high peaks of the Icefield are reproduced by downscaled climatic data. The mass balance simulations were validated and interpreted using geodetic mass balances, measured point balances and a complete velocity field of the Southern Patagonia Icefield (SPI) from spring 2004. The high measured accumulation of snow as well as the high measured ablation values are reproduced by the model. Subtracting the modeled surface mass balance from the geodetic balances, calving fluxes of major outlet glaciers were inferred. Good agreement with calving fluxes estimated from velocity data was obtained in many cases however on several glaciers the inferred calving fluxes seem to overestimate the measured calving fluxes. The measured calving fluxes exhibit large uncertainties due to mostly unknown ice thickness data and evolution of glacier velocities through time. The accumulation of snow and its redistribution due to wind drift present the mayor uncertainties in the modeled surface mass balance. Assuming no substantial changes in ice flow, the surface mass balance model driven by ECHAM5 data in the A1B scenario predicts a contribution of the Patagonian Icefields to sea-level rise in the 21st century of 7.3 mm.

  20. 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. PMID:18576739

  1. 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.

  2. Feeding strategy of juvenile (age-0+ year) Argentine hake Merluccius hubbsi in the Patagonian nursery ground.

    PubMed

    Temperoni, B; Viñas, M D; Buratti, C C

    2013-11-01

    Age-0+ year juvenile Argentine hake Merluccius hubbsi (60-150 mm total length, L(T)) from San Jorge Gulf, north Patagonian shelf region of the Argentine Sea, had an almost exclusively pelagic diet dominated by the hyperiid amphipod Themisto gaudichaudii and the euphausiid Euphausia lucens. This suggested that final settlement and permanent demersal habitat utilization might not, as previously reported, occur at earlier sizes (c. 20 mm L(T)). Their feeding strategy involves specialization at a population level towards both the main pelagic prey, indicating a narrow trophic niche. Novel data are provided which contribute to the growing body of information in relation to the age-0+ year transitional stage in demersal fishes and particularly to M. hubbsi recruitment in the Argentine Sea. PMID:24580669

  3. 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.

  4. 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. PMID:18363661

  5. 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.

  6. 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. PMID:26282747

  7. Freezing resistance in Patagonian woody shrubs: the role of cell wall elasticity and stem vessel size.

    PubMed

    Zhang, Yong-Jiang; Bucci, Sandra J; Arias, Nadia S; Scholz, Fabian G; Hao, Guang-You; Cao, Kun-Fang; Goldstein, Guillermo

    2016-08-01

    Freezing resistance through avoidance or tolerance of extracellular ice nucleation is important for plant survival in habitats with frequent subzero temperatures. However, the role of cell walls in leaf freezing resistance and the coordination between leaf and stem physiological processes under subzero temperatures are not well understood. We studied leaf and stem responses to freezing temperatures, leaf and stem supercooling, leaf bulk elastic modulus and stem xylem vessel size of six Patagonian shrub species from two sites (plateau and low elevation sites) with different elevation and minimum temperatures. Ice seeding was initiated in the stem and quickly spread to leaves, but two species from the plateau site had barriers against rapid spread of ice. Shrubs with xylem vessels smaller in diameter had greater stem supercooling capacity, i.e., ice nucleated at lower subzero temperatures. Only one species with the lowest ice nucleation temperature among all species studied exhibited freezing avoidance by substantial supercooling, while the rest were able to tolerate extracellular freezing from -11.3 to -20 °C. Leaves of species with more rigid cell walls (higher bulk elastic modulus) could survive freezing to lower subzero temperatures, suggesting that rigid cell walls potentially reduce the degree of physical injury to cell membranes during the extracellular freezing and/or thaw processes. In conclusion, our results reveal the temporal-spatial ice spreading pattern (from stem to leaves) in Patagonian shrubs, and indicate the role of xylem vessel size in determining supercooling capacity and the role of cell wall elasticity in determining leaf tolerance of extracellular ice formation. PMID:27217529

  8. 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.

  9. 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. PMID:16414190

  10. 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.

  11. 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

    2016-01-01

    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. PMID:27515658

  12. 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. PMID:19674310

  13. 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

  14. Unraveling burial heating and sediment recycling in retroarc foreland basins: Detrital thermochronologic insights from the northern Magallanes Basin, Patagonian Andes

    NASA Astrophysics Data System (ADS)

    Fosdick, J. C.; Grove, M. J.; Graham, S. A.; Hourigan, J. K.; Lovera, O. M.; Romans, B.

    2014-12-01

    Sediment recycling is expected in many tectonic settings, such as foreland basins, where the path followed by grains initially derived from erosion of a basement source region typically involves significant intermediate stages of crustal evolution before the detritus is finally incorporated into tectonically stable basin strata. The shallow-crustal thermal histories experienced by eroded sediment may go undetected by traditional provenance methods but are potentially recoverable by thermochronologic methods. The Patagonian Magallanes retroarc foreland basin affords an excellent case study of sediment burial and recycling within a thrust belt setting. Combined detrital zircon U-Pb geochronology and (U-Th)/He thermochronology data and thermal modeling results confirm delivery of both rapidly cooled, first-cycle volcanogenic sediments from the Patagonian magmatic arc and recycled sediment from deeply buried and exhumed Cretaceous foredeep strata to the Cenozoic Magallanes basin depocenter. Numerical models of temperature-time histories indicate that ca. 54-45 Ma burial of the Maastrichtian Dorotea Formation produced 164-180°C conditions and heating to within the zircon He partial retention zone. Such deep burial is unusual for Andean foreland basins and may have resulted from combined effects of high basal heat flow and high sediment accumulation within a rapidly subsiding foredeep that was floored by basement weakened by previous Late Jurassic rifting. In this interpretation, Cenozoic thrust-related deformation deeply eroded the Dorotea Formation and underlying strata from ~5 km burial depths and may be associated with the development of a regionally extensive Paleogene unconformity. Results from the Cenozoic Río Turbio and Santa Cruz formations confirm that they contain both Cenozoic first-cycle zircon from the Patagonian magmatic arc and highly outgassed recycled zircon. This work suggests that Middle Miocene sediments were most likely derived from recycling of

  15. 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)

  16. 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

  17. Igneous History of the Andean Cordillera and Patagonian Plateau around Latitude 46 degrees S

    NASA Astrophysics Data System (ADS)

    Baker, P. E.; Rea, W. J.; Skarmeta, J.; Caminos, R.; Rex, D. C.

    1981-11-01

    From the Middle Jurassic onwards persistent igneous activity in the southern Andes around 46 degrees S was controlled by easterly dipping subduction along the Pacific margin. Cogenetic plutonic rocks belonging to the Patagonian batholith, and calc-alkaline volcanics ranging from basaltic andesites to rhyolitic tuffs and ignimbrites are the principal products. Erosion of the primary volcanics has led at various times to the development of thick volcaniclastic sequences, for example in the Cretaceous--Lower Tertiary Divisadero formation. The Coyhaique region marks the northerly extension of a narrow back-arc basin in which the marine Neocomian successions accumulated. Volcaniclastics from the island arc, which presumably lay to the west, are intercalated with the sediments. Although the marine basin was short-lived a mildly extensional back-arc regime may have existed through much of Mesozoic--Recent times. Widespread basalt--rhyolite volcanism on the eastern side of the cordillera seems to have been associated with this tectonic environment. Remnants of the Patagonian basalt plateau at latitude 45-47 degrees S extend from the Argentine--Chile frontier to Lago Colhue Huapi. Four principal age and compositional groups have been distinguished in the lavas. (i) The oldest, which are about 80 Ma, occur in sections at Senguerr and Morro Negro. They are almost exclusively tholeiitic, but show some calc-alkaline affinities and resemble in other respects basalts from marginal basins. (ii) The second group (57-43 Ma) occur in the lower part of the Chile Chico section with a compositional spread from olivine tholeiites through alkali basalts to one occurrence of a basanite. (iii) The upper part of the main plateau sequence, where the flows are in the range 25-9 Ma, are dominantly of alkali basalt composition. (iv) Post-plateau flows from small cinder cones on the surface of the plateau range in age from ca. 4 Ma to 0.2 Ma or less. They are mostly highly undersaturated

  18. 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

  19. 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

  20. Patagonian Andean evolution from Miocene foreland basin detrital zircon geochronology (Invited)

    NASA Astrophysics Data System (ADS)

    Lo, S.; Fosdick, J. C.

    2009-12-01

    Sedimentary basins record the erosional history of their sediment sources, and in particular, the unroofing evolution of nearby mountain belts. As such, we use the unique U-Pb crystallization age distribution of zircon crystals separated from basin sediments to assess the spatial distribution of mountain belt exhumation. The Magallanes retroarc foreland basin in southernmost Chile and Argentina developed in response to crustal loading of the Patagonian fold-thrust belt during orogenesis. As such, this basin filled with sediment during the active formation of the Patagonian fold-thrust belt. Previous work suggests that the Cretaceous basin fill was derived from the magmatic arc and fold-thrust belt, and that the growth of the thrust belt progressively isolated the basin from detrital input from the magmatic arc. Our project goal is to evaluate the rates and timing of thrust belt growth by comparing the sediment source age and exhumation record in the Paleogene-Neogene basin fill. We separated zircons from paired sandstone and volcanic ash samples collected from the syntectonic Paleogene-Neogene section of the Magallanes Basin in Chile and Argentina, Patagonia (51 30’S). Our analytical strategy involves three steps: 1) refine stratigraphic age of sandstones by U-Pb dating of nearby volcanic ashes, 2) characterize sediment source age by detrital zircon U-Pb dating. These sandstone and ash samples were prepared for zircon U-Pb geochronologic analysis using a variety of mineral separation methods. These included crushing, grinding of bulk samples, Gemini table separation of dense and light grains, and magnetic frantz removal of iron-rich minerals. A heavy liquid, lithium meta-tungstate (LMT) was used to further separate minerals, and finally, samples were handpicked under a binocular microscope. New zircon U-Pb SHRIMP age results from the volcanic ashes indicate the syntectonic sedimentary succession was deposited between ca. 21-18 Ma. These ages refine the existing

  1. Scenarios of Future Climate and Land-Management Effects on Carbon Stocks in Northern Patagonian Shrublands

    NASA Astrophysics Data System (ADS)

    Carrera, Analia; Ares, Jorge; Labraga, Juan; Thurner, Stephanie; Bertiller, Mónica

    2007-12-01

    We analyzed the possible effects of grazing management and future climate change on carbon (C) stocks in soils of northern Patagonian shrublands. To this aim, we coupled the outputs of three (HadCM3, CSIRO Mk2, and CCSR/NIES) global climate models to the CENTURY (v5.3) model of terrestrial C balance. The CENTURY model was initialized with long-term field data on local biome physiognomy, seasonal phenologic trends, and prevailing land-management systems and was validated with recent sequences of 1-km Normalized Difference Vegetation Index (MODIS-Terra) images and soil C data. In the tested scenarios, the predicted climate changes would result in increased total C in soil organic matter (SOMTC). Maximum SOMTC under changed climate forcing would not differ significantly from that expected under baseline conditions (8 kg m-2). A decrease in grazing intensity would result in SOMTC increases of 11% to 12% even if climate changes did not occur. Climate change would account for SOMTC increases of 5% to 6%.

  2. Scenarios of future climate and land-management effects on carbon stocks in northern Patagonian shrublands.

    PubMed

    Carrera, Analia; Ares, Jorge; Labraga, Juan; Thurner, Stephanie; Bertiller, Mónica

    2007-12-01

    We analyzed the possible effects of grazing management and future climate change on carbon (C) stocks in soils of northern Patagonian shrublands. To this aim, we coupled the outputs of three (HadCM3, CSIRO Mk2, and CCSR/NIES) global climate models to the CENTURY (v5.3) model of terrestrial C balance. The CENTURY model was initialized with long-term field data on local biome physiognomy, seasonal phenologic trends, and prevailing land-management systems and was validated with recent sequences of 1-km Normalized Difference Vegetation Index (MODIS-Terra) images and soil C data. In the tested scenarios, the predicted climate changes would result in increased total C in soil organic matter (SOMTC). Maximum SOMTC under changed climate forcing would not differ significantly from that expected under baseline conditions (8 kg m(-2)). A decrease in grazing intensity would result in SOMTC increases of 11% to 12% even if climate changes did not occur. Climate change would account for SOMTC increases of 5% to 6%. PMID:17786512

  3. 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.

  4. 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. PMID:23812108

  5. 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

  6. 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.

  7. 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. PMID:25738698

  8. 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.

  9. 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. PMID:26961305

  10. Interannual variability in the skate assemblage on the South Patagonian shelf and slope.

    PubMed

    Winter, A; Pompert, J; Arkhipkin, A; Brewin, P E

    2015-12-01

    Observer data from the commercial fishery on the Patagonian shelf and slope around the Falkland Islands (home to an assemblage of >16 skate species (Rajiformes), for which commercial catches have been recorded since 1987), as well as survey data from an area closed to skate target fishing after exploitation, were summarized by species to examine changes in the population status of individual skate species. Total skate catch per unit effort increased significantly in the target fishery since 1994, and four species have made up >85% of all skate catch. Bathyraja brachyurops and Zearaja chilensis increased significantly in catch proportions and abundance from 1994 to 2013. Bathyraja albomaculata and Bathyraja griseocauda decreased significantly before rebounding with trends of increasing abundance. Concurrently, B. brachyurops and Z. chilensis showed decreasing trends in size at 50% maturity in areas where skates continue to be targeted commercially. The increasing abundances and concomitant reductions in size at maturity of B. brachyurops and Z. chilensis suggest either plasticity in life-history traits or a density-dependent growth response to fishing pressure. Bathyraja griseocauda decreased in size at 50% maturity in the area that was closed to skate target fishing, where it was initially larger, but only decreased to the same average size as in the commercially targeted areas. Bathyraja albomaculata and Z. chilensis are IUCN-listed as vulnerable and B. griseocauda is listed as endangered, but their abundance trends since 1994 indicate that these populations are not declining in Falkland waters. PMID:26709216

  11. 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.

  12. Succession in subtidal macrofouling assemblages of a Patagonian harbour (Argentina, SW Atlantic)

    NASA Astrophysics Data System (ADS)

    Rico, Alicia; Peralta, Roxana; López Gappa, Juan

    2012-12-01

    Subtidal fouling assemblages usually consist of short-lived organisms. Colonisation sequences on man-made structures may thus be greatly affected by the temporal and spatial variability of propagule supply. This study explores the influence of seasonality on succession in the macrofouling assemblage of a Patagonian harbour (Argentina, Southwest Atlantic). Replicated artificial substrata were suspended horizontally and sampled at quarterly intervals during 1 year. The influence of seasonality on 1-year-old assemblages was further analysed using additional sets of replicated panels submersed at different seasons and collected 1 year later. Upper surfaces were always dominated by ephemeral algae, while lower surfaces exhibited high coverage of filter-feeding invertebrates. Regardless of submersion length, species richness was significantly higher on lower than on upper surfaces. A significant interaction between orientation and submersion length was found for the Shannon diversity index, meaning that temporal changes in diversity depended on substratum orientation. On the lower surfaces, diversity reached a maximum after 9 months and then declined, mainly due to extensive dislodgment of two species of ascidians. On algal-dominated upper surfaces, differences in structure of annual assemblages were due to seasonal changes in the abundance of ephemeral algae. This study shows that constancy or variability of 1-year-old assemblages whose development began at different seasons depended greatly on the life history of the organisms that settled and managed to persist on both surfaces, which in turn depended on substratum orientation.

  13. 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

  14. 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

  15. 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

  16. The COPAS’08 expedition to the Patagonian Shelf: Physical and environmental conditions during the 2008 coccolithophore bloom

    NASA Astrophysics Data System (ADS)

    Painter, Stuart C.; Poulton, Alex J.; Allen, John T.; Pidcock, Rosalind; Balch, William M.

    2010-10-01

    Here we present observations of the hydrography of the Patagonian Shelf, shelf break and offshore waters, with reference to the environmental conditions present during the period of peak coccolithophore abundance. Analysis of a hydrographic dataset collected in December 2008 (austral spring/summer), as part of the Coccolithophores of the Patagonian Shelf (COPAS) research cruise, identified 5 distinct surface water masses in the region between 37°S and 55°S. These water masses, identified through salinity gradients, displayed varying mixed layer depths, macronutrient inventories and chlorophyll- a fluorescence. Subantarctic Shelf Water (SSW), located to the north of the Falkland Islands and extending north along the shelf break, was also host to a large coccolithophore bloom. The similarities between the distribution of calcite, as seen in remote sensing data, and SSW indicate that the coccolithophore bloom encountered conditions conducive to bloom development within this water mass. Analysis of chemical and environmental data also collected during the COPAS cruise revealed that many of the commonly cited conditions for coccolithophore bloom development were present within SSW (e.g. low N:P ratio, high N:Si ratio, shallow mixed layer depth). In the other water masses present on the Patagonian Shelf greater variability in these same parameters may explain the more diffuse concentration of calcite, and the smaller size of possible coccolithophore blooms. The distribution of SSW is strongly influenced by the latitudinal variation in shelf break frontal width, which varies from 20 to 200 km, and consequently strong hydrographic controls underlie the position of the coccolithophore bloom during austral summer.

  17. Initiation of the Magallanes foreland basin: Timing of the southernmost Patagonian Andes orogeny revised by detrital zircon provenance analysis

    USGS Publications Warehouse

    Fildani, A.; Cope, T.D.; Graham, S.A.; Wooden, J.L.

    2003-01-01

    New sensitive high-resolution ion microprobe-reverse geometry U-Pb detrital zircon data establish the timing of onset of foreland basin subsidence in the Magallanes basin and the age of the Patagonian Andes in southernmost Chile. Initiation of the Magallanes foreland basin is signaled by the abrupt occurrence of sandstone of the Punta Barrosa Formation, loosely dated as upper Albian-Cenomanian from biofacies assemblages. Detrital zircon analyses demonstrate that the Punta Barrosa Formation is not older than 92 ?? 1 Ma and that the linked Andean belt started forming in the Turonian.

  18. 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

  19. Description of Maritrema formicae sp. nov. (Digenea, Microphallidae) parasitic in the kelp gull, Larus dominicanus, from the Patagonian coast, Argentina.

    PubMed

    Diaz, Julia I; Gilardoni, Carmen; Cremonte, Florencia

    2012-06-01

    Maritrema formicae sp. nov. is described from the Patagonian coast, Argentina, based on adults obtained from the kelp gull, Larus dominicanus. The new species fits with the "eroliae complex" and can be distinguished from other related species mainly in shape and size of body, shape, size, and pattern of distribution of cirrus spines, uterus extension, number and size of eggs, vitellarium in a complete ring in all specimens, and its Neotropical distribution. The new species is sympatric with another species of the genus, Maritrema madrynense, which was recorded in the same host and locality. PMID:22807050

  20. 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.

  1. 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.

  2. 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.

  3. 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

  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. The 2008 Emiliania huxleyi bloom along the Patagonian Shelf: Ecology, biogeochemistry, and cellular calcification

    NASA Astrophysics Data System (ADS)

    Poulton, Alex J.; Painter, Stuart C.; Young, Jeremy R.; Bates, Nicholas R.; Bowler, Bruce; Drapeau, Dave; Lyczsckowski, Emily; Balch, William M.

    2013-12-01

    blooms are significant contributors to the global production and export of calcium carbonate (calcite). The Patagonian Shelf is a site of intense annual coccolithophore blooms during austral summer. During December 2008, we made intensive measurements of the ecology, biogeochemistry, and physiology of a coccolithophore bloom. High numbers of Emiliania huxleyi cells and detached coccoliths (>1 × 103 mL-1 and >10 × 103 mL-1, respectively), high particulate inorganic carbon concentrations (>10 mmol C m-2), and high calcite production (up to 7.3 mmol C m-2 d-1) all characterized bloom waters. The bloom was dominated by the low-calcite-containing B/C morphotype of Emiliania huxleyi, although a small (<10 µm) Southern Ocean diatom of the genus Fragilariopsis was present in almost equal numbers (0.2-2 × 103 mL-1). Estimates of Fragilariopsis contributions to chlorophyll, phytoplankton carbon, and primary production were >30%, similar to estimates for E. huxleyi and indicative of a significant role for this diatom in bloom biogeochemistry. Cell-normalized calcification rates, when corrected for a high number of nonactive cells, were relatively high and when normalized to estimates of coccolith calcite indicate excessive coccolith production in the declining phase of the bloom. We find that low measures of calcite and calcite production relative to other blooms in the global ocean indicate that the dominance of the B/C morphotype may lead to overall lower calcite production. Globally, this suggests that morphotype composition influences regional bloom inventories of carbonate production and export and that climate-induced changes in morphotype biogeography could affect the carbon cycle.

  6. 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

  7. Seasonal variability in satellite-measured surface chlorophyll in the Patagonian Shelf

    NASA Astrophysics Data System (ADS)

    Rivas, Andrés L.; Dogliotti, Ana Inés; Gagliardini, Domingo A.

    2006-04-01

    Six years (January 1998—December 2003) of SeaWiFS ocean color satellite data are used to estimate monthly climatological means and to present the near-surface chlorophyll-a seasonal evolution in the Patagonian Shelf. The southern part of the shelf presents elevated chlorophyll concentrations from spring through autumn, while the northern part shows three regions with particular characteristics. The external region, bordering the 200 m isobath, presents elevated concentrations from spring through autumn supported by the nutrient-rich waters from the Malvinas (Falkland) Current. The central region presents a typical pattern of temperate regions, characterized by two well-defined maxima, a stronger spring bloom and a weaker fall bloom, and low chlorophyll values throughout summer (scarce availability of nutrients) and winter (light being the limiting factor). Even though the displacement direction of the spring and fall blooms do not agree with previous information reported in the literature, they are interpreted based on the heat exchange in the air-sea interface that controls the development and erosion of the seasonal thermocline. Finally, the coastal region presents less-marked seasonal variability and isolated small areas with elevated concentrations associated with frontal areas are observed. The spatial mean chlorophyll evolution, averaged over the whole shelf (less than 200 m depth), shows a marked annual cycle with high values from spring to autumn, supporting the importance of frontal regions as a fertilization mechanism. An increasing trend in chlorophyll concentrations, within the 6 years analyzed here (in the order of 23%), is apparent based on an increasing of the maximum annual values. From the comparison with in situ data it can be concluded that satellite information reproduces the spatial patterns of chlorophyll fields obtained from more classical data, while differences exist in absolute values obtained from both methodologies.

  8. 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. PMID:23251554

  9. 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

  10. 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.

  11. 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. PMID:19043485

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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. PMID:24580663

  17. 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

    2015-01-01

    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. PMID:25781852

  18. 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. PMID:26639826

  19. 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

  20. 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.

  1. Seismic refraction exploration

    SciTech Connect

    Ruehle, W.H.

    1980-12-30

    In seismic exploration, refracted seismic energy is detected by seismic receivers to produce seismograms of subsurface formations. The seismograms are produced by directing seismic energy from an array of sources at an angle to be refracted by the subsurface formations and detected by the receivers. The directivity of the array is obtained by delaying the seismic pulses produced by each source in the source array.

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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.

  12. Accumulation and distribution of trace metals within soils and the austral cordgrass Spartina densiflora in a Patagonian salt marsh.

    PubMed

    Idaszkin, Yanina L; Lancelotti, Julio L; Bouza, Pablo J; Marcovecchio, Jorge E

    2015-12-15

    Concentrations of Cd, Cu, Fe, Pb, and Zn were determined in soils and in below- and above-ground structures of Spartina densiflora in a Patagonian salt marsh (San Antonio, Río Negro, Argentina). Also, the relationship between trace metal concentrations in soils and plants was investigated to improve our knowledge regarding the ability of this plant species to take up and accumulate trace metals from the soil. Our results indicate that, within the studied salt marsh, soil trace metal concentrations follow a decreasing concentration gradient toward the sea. They show moderate pollution and a potentially negative biological effect in one site of the salt marsh. While below-ground structures reflect the soil metal concentration pattern, this is not so evident in above-ground concentrations. Also, S. densiflora is able to absorb a limited amount of metals present in the soil, the soil bioaccumulation factor being lower in sites where soil metal concentration is higher. PMID:26481413

  13. 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.

  14. Exhuming retroarc fold-and-thrust belts: a comparison between the southern Patagonian Andes and the Argentine Precordillera

    NASA Astrophysics Data System (ADS)

    Fosdick, J. C.

    2014-12-01

    Detailed constraints on erosional flux are critical for understanding how exhumational processes control and respond to tectonic events in orogenic belts. This work compares the thermochronologic record and erosional behavior of retroarc thrust belts at two latitudes in the Andes with contrasting Cenozoic climate and deformational records: the glaciated southern Patagonian Andes and the semiarid Argentine Precordillera of the Central Andes. Both regions have undergone crustal shortening during Andean growth and have been affected by thermotectonic processes associated with subduction of oceanic ridges; the Chile Ridge spreading center and Juan Fernández Ridge, respectively. In Patagonia, deep erosion occurred during Miocene retroarc deformation. Zircon He thermochronology documents regional cooling and unroofing of the thrust belt ~22-17 Ma. This behavior likely reflects an upper plate manifestation of incipient subduction of the Chile Ridge spreading center and enhanced unroofing during thermally driven regional uplift. Late Cenozoic expansion of the Patagonian icesheet led to further excavation of the thrust belt, indicating a strong climatic overprinting on thrust belt erosional behavior. In contrast, less overall Cenozoic exhumation is observed in the Argentine Precordillera, despite high strain and crustal thickening. Pre-Jurassic zircon He dates from the Paleozoic strata within thrust sheets suggest Cenozoic Andean deformation was insufficient to exhume rocks from beneath the zircon He closure depth. The apatite He record shows a close correlation between thrust faulting and locus of erosion, and document eastward in-sequence rock cooling from 16 to 2 Ma across the Precordillera tracking with the progressive faulting of the Blanca, San Roque, and Niquivil thrust faults during this time. Pliocene apatite He dates located along the external margins of the Precordillera suggest that the most recent cooling and unroofing is associated with both out

  15. 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.

  16. Holocene glacier history of the Lago Argentino basin, Southern Patagonian Icefield

    NASA Astrophysics Data System (ADS)

    Strelin, Jorge A.; Kaplan, Michael R.; Vandergoes, Marcus J.; Denton, George H.; Schaefer, Joerg M.

    2014-10-01

    We present new geomorphic, stratigraphic, and chronologic data for Holocene glacier fluctuations in the Lago Argentino basin on the eastern side of the southern Patagonian Andes. Chronologic control is based on 14C and surface-exposure 10Be dating. After the Lateglacial maximum at 13,000 cal yrs BP, the large ice lobes that filled the eastern reaches of Lago Argentino retreated and separated into individual outlet glaciers; this recession was interrupted only by a stillstand or minor readvance at 12,200 cal yrs BP. The eight largest of these individual outlet glaciers are, from north to south: Upsala, Agassiz, Onelli, Spegazzini, Mayo, Ameghino, Perito Moreno, and Grande (formerly Frías). Holocene recession of Upsala Glacier exposed Brazo Cristina more than 10,115 ± 100 cal yrs BP, and reached inboard of the Holocene moraines in Agassiz Este Valley by 9205 ± 85 cal yrs BP; ice remained in an inboard position until 7730 ± 50 cal yrs BP. Several subsequent glacier readvances are well documented for the Upsala and Frías glaciers. The Upsala Glacier readvanced at least seven times, the first being a relatively minor expansion - documented only in stratigraphic sections - between 7730 ± 50 and 7210 ± 45 cal yrs BP. The most extensive Holocene advances of Upsala Glacier resulted in the deposition of the Pearson 1 moraines and related landforms, which are divided into three systems. The Pearson 1a advance occurred about 6000-5000 cal yrs BP and was followed by the slightly less-extensive Pearson 1b and 1c advances dated to 2500-2000 and 1500-1100 cal yrs BP, respectively. Subsequent advances of Upsala Glacier resulted in deposition of the Pearson 2 moraines and corresponding landforms, also separated into three systems, Pearson 2a, 2b, and 2c, constructed respectively at ˜700, >400, and <300 cal yrs BP to the early 20th century. Similar advances are also recorded by moraine systems in front of Grande Glacier and herein separated into the Frías 1 and Frías 2a, 2b

  17. 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

  18. 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.

  19. The reconstruction and climatic implication of an independent palaeo ice cap within the Andean rain shadow east of the former Patagonian ice sheet, Santa Cruz Province, Argentina

    NASA Astrophysics Data System (ADS)

    Wolff, Ingo W.; Glasser, Neil F.; Hubbard, Alun

    2013-03-01

    This paper describes the reconstruction of the previously undocumented Meseta Cuadrada palaeo ice cap on south-west Meseta del Lago Buenos Aires, Santa Cruz Province, Patagonia. Based on theoretical surface profiles the reconstruction of the Meseta Cuadrada Palaeo Ice Cap indicates an ice mass covering at least 78 km2 with a total ice volume around 9.2 km3. The inferred equilibrium line altitude (ELA) of the palaeo ice cap (2031 m asl) represents a drop of 286 m compared to the ELA of the current Meseta Cuadrada glacier (~ 2317 m asl). We explain this small change in ELA with reference to the flat hypsometry of the palaeo ice cap and an enhanced aridity to the west of the Patagonian Andes caused by the existence of the Last Glacial Maximum (LGM) Patagonian ice sheet. Calculated annual accumulation values of ca. 402 to 957 mm/a at the ELA of the Meseta Cuadrada palaeo ice cap derived by a degree day model (DDM) during the last local glacial maximum extent are low compared with estimations of the current accumulation at the ELA of the remaining glacierized area of around 3789 mm/a. This strongly supports the existence of increased aridity and seasonality east of the Patagonian Andes during the Last Glacial Maximum, provided both maximum extents were synchronous.

  20. 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

  1. 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

  2. Seismic signal of avalanches

    NASA Astrophysics Data System (ADS)

    Pesaresi, Damiano; Ravanat, Xavier; Thibert, Emmanuel

    2010-05-01

    The characterization of avalanches with seismic signals is an important task. For risk mitigation, estimating remotely avalanche activity by means of seismic signals is a good alternative to direct observations that are often limited by visual conditions and observer's availability. In seismology, the main challenge is to discriminate avalanche signals within the natural earth seismic activity and background noise. Some anthropogenic low frequency (infra-sound) sources like helicopters also generate seismic signals. In order to characterize an avalanche seismic signal, a 3-axis broad band seismometer (Guralp 3T) has been set-up on a real scale avalanche test site in Lautaret (France). The sensor is located in proximity of 2 avalanche paths where avalanches can be artificially released. Preliminary results of seismic records are presented, correlated with avalanche physical parameters (volume released, velocity, energy).

  3. Mapping Europe's Seismic Hazard

    NASA Astrophysics Data System (ADS)

    Giardini, Domenico; Wössner, Jochen; Danciu, Laurentiu

    2014-07-01

    From the rift that cuts through the heart of Iceland to the complex tectonic convergence that causes frequent and often deadly earthquakes in Italy, Greece, and Turkey to the volcanic tremors that rattle the Mediterranean, seismic activity is a prevalent and often life-threatening reality across Europe. Any attempt to mitigate the seismic risk faced by society requires an accurate estimate of the seismic hazard.

  4. Volcano seismicity in Alaska

    NASA Astrophysics Data System (ADS)

    Buurman, Helena

    I examine the many facets of volcano seismicity in Alaska: from the short-lived eruption seismicity that is limited to only the few weeks during which a volcano is active, to the seismicity that occurs in the months following an eruption, and finally to the long-term volcano seismicity that occurs in the years in which volcanoes are dormant. I use the rich seismic dataset that was recorded during the 2009 eruption of Redoubt Volcano to examine eruptive volcano seismicity. I show that the progression of magma through the conduit system at Redoubt could be readily tracked by the seismicity. Many of my interpretations benefited greatly from the numerous other datasets collected during the eruption. Rarely was there volcanic activity that did not manifest itself in some way seismically, however, resulting in a remarkably complete chronology within the seismic record of the 2009 eruption. I also use the Redoubt seismic dataset to study post-eruptive seismicity. During the year following the eruption there were a number of unexplained bursts of shallow seismicity that did not culminate in eruptive activity despite closely mirroring seismic signals that had preceded explosions less than a year prior. I show that these episodes of shallow seismicity were in fact related to volcanic processes much deeper in the volcanic edifice by demonstrating that earthquakes that were related to magmatic activity during the eruption were also present during the renewed shallow unrest. These results show that magmatic processes can continue for many months after eruptions end, suggesting that volcanoes can stay active for much longer than previously thought. In the final chapter I characterize volcanic earthquakes on a much broader scale by analyzing a decade of continuous seismic data across 46 volcanoes in the Aleutian arc to search for regional-scale trends in volcano seismicity. I find that volcanic earthquakes below 20 km depth are much more common in the central region of the arc

  5. 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.

  6. Amphipod-supported food web: Themisto gaudichaudii, a key food resource for fishes in the southern Patagonian Shelf

    NASA Astrophysics Data System (ADS)

    Padovani, Luciano N.; Viñas, María Delia; Sánchez, Felisa; Mianzan, Hermes

    2012-01-01

    The trophic role of the hyperiid amphipod Themisto gaudichaudii in the southern Patagonian shelf food web was assessed from the analysis of stomach contents of the local fish assemblage. A total of 461 trawl samples were collected during seven seasonal cruises. A total of 17 out of 38 fish species were found to ingest T. gaudichaudii. This amphipod was a main prey item in five of these species, showing high values of alimentary index: Seriolella porosa (99.9%), Macruronus magellanicus (68.8%), Micromesistius australis (59.1%), Patagonotothen ramsayi (48.6%), and Merluccius hubbsi (10.9%). The contribution of T. gaudichaudii, in weight, to their summer diet was 60%, on average. This contribution was minimal in winter and maximal in summer. Fisheries studies have indicated that these five species, mainly M. magellanicus, account for almost 85% of the fish biomass in the area. Although the remaining 15% did not feed heavily on T. gaudichaudii, they are known to prey on the main hyperiid predators. Our study shows that T. gaudichaudii contributes greatly, both directly and indirectly, to supporting the fish community. We thus proposed that T. gaudichaudii plays a key role as a "wasp-waist" species in the sub-Antarctic region, similar to that of krill in Antarctic waters, channeling the energy flow and enabling a short and efficient food chain.

  7. Interaction of position, litter type, and water pulses on decomposition of grasses from the semiarid Patagonian steppe.

    PubMed

    Austin, Amy T; Araujo, Patricia I; Leva, Paula E

    2009-09-01

    Litter lignin and nutrient content, annual rainfall, and biotic activity are not good predictors of litter decomposition in arid and semiarid ecosystems, suggesting that other factors may be important in controlling carbon turnover. We explored the relative importance of litter position (above- vs. belowground), litter type (leaf vs. root), and pulsed water events (large vs. small) on mass loss with grass species of the semiarid Patagonian steppe. In a factorial experiment of mesocosms, we incubated leaf and root litter simultaneously above- and belowground and manipulated water availability with large and small pulses. Significant interactions between position and litter type and position and pulse sizes demonstrated interactive controls on organic mass loss. Aboveground decomposition showed no response to pulse size or litter type, as roots and leaves decomposed equally rapidly under all circumstances. In contrast, belowground decomposition was significantly altered by litter type and water pulses, with roots decomposing significantly slower and small water pulses reducing belowground decomposition. The results of this mesocosm experiment support the idea that controls other than water availability may dominate aboveground mass loss, while a combination of recalcitrant litter and water penetration in the soil profile are critical factors determining belowground decomposition, which is ultimately mediated by biotic degradation. PMID:19769141

  8. 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.

  9. Dento-alveolar lesions and palaeodietary inferences from the Paso Alsina 1 site (eastern Pampean-Patagonian transition, Argentina).

    PubMed

    Flensborg, G

    2011-10-01

    Several archaeological researches in northeastern Patagonia and southeastern Pampas have evaluated various indicators of the diets of hunter-gatherers who inhabited these regions during the Late Holocene, including the role of plant foods. Dental analysis is an important way to introduce new information about subsistence. In this sense, the objective of this work is to document and interpret dento-alveolar lesions in an osteological sample recovered from the Paso Alsina 1 archaeological site (eastern Pampean-Patagonian transition, Argentina). This paper will explore the oral health status of individuals and discuss palaeodietary information of hunter-gatherers that inhabited the lower valley of the Colorado River during the final Late Holocene (ca. 500 years BP). The site is defined as a formal area bundle composed of 10 secondary multiple burials containing 56 individuals of both sexes and various ages (e.g., perinatal, infant, and adult). In this study, 781 teeth and 1036 alveoli from 47 maxillae and 38 mandibles were analysed from 51 adult individuals. The results indicate a moderate rate of dental wear, and dental calculus, and low percentages of caries, abscesses, and antemortem tooth loss. The information obtained suggests a diet based on a combination of proteins, fat and carbohydrates. Results are then compared with those from other lines of analysis for the study area and for the neighboring regions (northeastern Patagonia and southeastern Pampas). PMID:21924417

  10. Immunological and health-state parameters in the Patagonian rockfish Sebastes oculatus. Their relation to chemical stressors and seasonal changes.

    PubMed

    Sueiro, Maria Cruz; Palacios, María Gabriela

    2016-01-01

    We present the results of a field study that evaluates whether exposure to anthropogenic pollution impacts immunological and health-state parameters of wild marine fish during the breeding and non-breeding periods. We assessed aspects of innate immunity (bactericidal capacity, bacterial agglutination, and leukocyte profile) and general health-related parameters (neutrophil to lymphocyte ratio, hematocrit, and condition factor) in the Patagonian rockfish (Sebastes oculatus) sampled from polluted (exposed) and reference (control) sites during winter (i.e., coolest temperatures and active reproductive period) and in summer (i.e., warmest temperatures and non-reproductive period). Results showed lower bactericidal competence, hematocrit, and condition factor in fish from exposed sites independently of season, whereas lymphocytes were higher and monocytes lower at the exposed site only during summer. Moreover, fish sampled during winter displayed lower bactericidal competence, hematocrit, and condition factor than those sampled in summer independently of site, whereas the opposite pattern was found for bacterial agglutination. These results could be explained by life-history theory, which predicts a re-allocation of resources between reproduction and other physiological functions (including immunity) during the most energetically demanding season. The present results show an alteration in immunological and health-state parameters of wild marine fish exposed to anthropogenic pollution independently of season, which could potentially result in higher susceptibility to disease and in turn population decline. PMID:26584758

  11. Use of a hybrid external skeletal fixator for repair of a periarticular tibial fracture in a Patagonian cavy.

    PubMed

    Joyner, Priscilla H; Rochat, Mark C; Hoover, John P

    2004-04-15

    An 8-week-old female Patagonian cavy was examined because of acute right hind limb lameness; radiography revealed a moderately displaced, comminuted fracture of the proximal third of the tibia. The fracture was stabilized with a hybrid external skeletal fixator. Two Kirschner wires were placed in the main proximal fragment, parallel to the tibial plateau and at right angles to each other. These wires were connected to a partial circular external fixator ring. Three half pins were placed in the distal fragment, and a straight connecting rod positioned on the medial side of the limb was connected to these pins and the fixator ring. A second connecting rod was positioned on the craniomedial side of the limb and was connected to the fixator ring and a fourth half pin in the distal fragment. The fracture healed without complications, and the fixator was removed 3 weeks after surgery. Hybrid external skeletal fixators combine the benefits of circular and linear external skeletal fixation methods, enabling rigid fixation of periarticular long bone fractures without adversely affecting mobility of the adjacent joint. PMID:15112778

  12. 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

  13. Seismic Computerized Alert Network

    USGS Publications Warehouse

    1986-01-01

    In 1985 the USGS devised a model for a Seismic Computerized Alert Network (SCAN) that would use continuous monitoring of seismic data from existing types of instruments to provide automatic, highly-reliable early warnings of earthquake shaking. In a large earthquake, substantial damaging ground motions may occur at great distances from the earthquake's epicenter.

  14. Proceedings of seismic engineering 1991

    SciTech Connect

    Ware, A.G. )

    1991-01-01

    This book contains proceedings of the Seismic Engineering Technical Subcommittee of the ASME Pressure Vessels and Piping Division. Topics covered include: seismic damping and energy absorption, advanced seismic analysis methods, new analysis techniques and applications of advanced methods, seismic supports and test results, margins inherent in the current design methods, and risk assessment, and component and equipment qualification.

  15. 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

  16. 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. PMID:27505009

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. Seismicity, 1980-86

    SciTech Connect

    Hill, D.P.; Eaton, J.P.; Jones, L.M.

    1990-01-01

    Tens of thousands of small earthquakes occur in California each year, reflecting brittle deformation of the margins of the Pacific and North American plates as they grind inexorably past one another along the San Andreas fault system. The deformational patterns revealed by this ongoing earthquake activity provide a wealth of information on the tectonic processes along this major transform boundary that, every few hundred years, culminate in rupture of the San Andreas fault in a great (M {approx} 8) earthquake. This chapter describes the regional seismicity and the San Andreas transform boundary; seismicity along the San Andreas Fault system; and focal mechanisms and transform-boundary kinematics. Seismicity patterns and the earthquake cycle and distributed seismicity and deformation of the plate margins are discussed.

  6. Seismic attenuation in Florida

    SciTech Connect

    Bellini, J.J.; Bartolini, T.J.; Lord, K.M.; Smith, D.L. . Dept. of Geology)

    1993-03-01

    Seismic signals recorded by the expanded distribution of earthquake seismograph stations throughout Florida and data from a comprehensive review of record archives from stations GAI contribute to an initial seismic attenuation model for the Florida Plateau. Based on calculations of surface particle velocity, a pattern of attenuation exists that appears to deviate from that established for the remainder of the southeastern US. Most values suggest greater seismic attenuation within the Florida Plateau. However, a separate pattern may exist for those signals arising from the Gulf of Mexico. These results have important implications for seismic hazard assessments in Florida and may be indicative of the unique lithospheric identity of the Florida basement as an exotic terrane.

  7. Seismic Ray Theory

    NASA Astrophysics Data System (ADS)

    Cerveny, V.

    2001-07-01

    The seismic ray method plays an important role in seismology, seismic exploration, and in the interpretation of seismic measurements. Seismic Ray Theory presents the most comprehensive treatment of the method available. Many new concepts that extend the possibilities and increase the method's efficiency are included. The book has a tutorial character: derivations start with a relatively simple problem, in which the main ideas are easier to explain, and then advance to more complex problems. Most of the derived equations are expressed in algorithmic form and may be used directly for computer programming. This book will prove to be an invaluable advanced text and reference in all academic institutions in which seismology is taught or researched.

  8. 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.

  9. Passive seismic experiment

    NASA Technical Reports Server (NTRS)

    Latham, G. V.; Ewing, M.; Press, F.; Sutton, G.; Dorman, J.; Nakamura, Y.; Toksoz, N.; Lammlein, D.; Duennebier, F.

    1972-01-01

    The establishment of a network of seismic stations on the lunar surface as a result of equipment installed by Apollo 12, 14, and 15 flights is described. Four major discoveries obtained by analyzing seismic data from the network are discussed. The use of the system to detect vibrations of the lunar surface and the use of the data to determine the internal structure, physical state, and tectonic activity of the moon are examined.

  10. AUTOMATING SHALLOW SEISMIC IMAGING

    SciTech Connect

    Steeples, Don W.

    2003-09-14

    The current project is a continuation of an effort to develop ultrashallow seismic imaging as a cost-effective method potentially applicable to DOE facilities. The objective of the present research is to develop and demonstrate the use of a cost-effective, automated method of conducting shallow seismic surveys, an approach that represents a significant departure from conventional seismic-survey field procedures. Initial testing of a mechanical geophone-planting device suggests that large numbers of geophones can be placed both quickly and automatically. The development of such a device could make the application of SSR considerably more efficient and less expensive. The imaging results obtained using automated seismic methods will be compared with results obtained using classical seismic techniques. Although this research falls primarily into the field of seismology, for comparison and quality-control purposes, some GPR data will be collected as well. In the final year of th e research, demonstration surveys at one or more DOE facilities will be performed. An automated geophone-planting device of the type under development would not necessarily be limited to the use of shallow seismic reflection methods; it also would be capable of collecting data for seismic-refraction and possibly for surface-wave studies. Another element of our research plan involves monitoring the cone of depression of a pumping well that is being used as a proxy site for fluid-flow at a contaminated site. Our next data set will be collected at a well site where drawdown equilibrium has been reached. Noninvasive, in-situ methods such as placing geophones automatically and using near-surface seismic methods to identify and characterize the hydrologic flow regimes at contaminated sites support the prospect of developing effective, cost-conscious cleanup strategies for DOE and others.

  11. 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.

  12. 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

  13. 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

  14. 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

  15. Seismic source parameters

    SciTech Connect

    Johnson, L.R.

    1994-06-01

    The use of information contained on seismograms to infer the properties of an explosion source presents an interesting challenge because the seismic waves recorded on the seismograms represent only small indirect, effects of the explosion. The essential physics of the problem includes the process by which these elastic waves are generated by the explosion and also the process involved in propagating the seismic waves from the source region to the sites where the seismic data are collected. Interpretation of the seismic data in terms of source properties requires that the effects of these generation and propagation processes be taken into account. The propagation process involves linear mechanics and a variety of standard seismological methods have been developed for handling this part of the problem. The generation process presents a more difficult problem, as it involves non-linear mechanics, but semi-empirical methods have been developed for handling this part of the problem which appear to yield reasonable results. These basic properties of the seismic method are illustrated with some of the results from the NPE.

  16. 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.

  17. Magnitude correlations in global seismicity

    SciTech Connect

    Sarlis, N. V.

    2011-08-15

    By employing natural time analysis, we analyze the worldwide seismicity and study the existence of correlations between earthquake magnitudes. We find that global seismicity exhibits nontrivial magnitude correlations for earthquake magnitudes greater than M{sub w}6.5.

  18. 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.

  19. Downhole seismic array system

    SciTech Connect

    Petermann, S.G.

    1992-03-03

    This patent describes an apparatus of receiving seismic signals from an earth formation at least at one or more points in a wellbore penetrating the formation. It comprises a sonde including extensible and retractable support means thereon for supporting seismic signal receiver means, hydraulic actuator means for extending and reacting the support means, body means for supporting the actuator means and the support means and signal transmitting means for transmitting electrical signals related to seismic signals received by the receiver means; tubing means connected to the sonde for deploying the sonde in the wellbore, the tubing means including electrical conductor means disposed therein for conducting electrical signals between means on the surface of the formation and the sonde and the tubing means comprising means for conducting hydraulic fluid to the sonde for operation of the actuator means; and means for supplying hydraulic fluid from the surface of the formation through the tubing means to the sonde for operating the actuator means.

  20. 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.

  1. Canadian Seismic Agreement

    SciTech Connect

    Wetmiller, R.J.; Lyons, J.A.; Shannon, W.E.; Munro, P.S.; Thomas, J.T.; Andrew, M.D.; Lapointe, S.P.; Lamontagne, M.; Wong, C.; Anglin, F.M.; Adams, J.; Cajka, M.G.; McNeil, W.; Drysdale, J.A. )

    1992-05-01

    This is a progress report of work carried out under the terms of a research agreement entitled the Canadian Seismic Agreement'' between the US Nuclear Regulatory Commission (USNRC), the Canadian Commercial Corporation and the Geophysics Division of the Geological Survey of Canada (GD/GSC) during the period from July 01, 1989 to June 30, 1990. The Canadian Seismic Agreement'' supports generally the operation of various seismograph stations in eastern Canada and the collection and analysis of earthquake data for the purpose of mitigating seismic hazards in eastern Canada and the northeastern US. The specific activities carried out in this one-year period are summarized below under four headings; Eastern Canada Telemetred Network and local network developments, Datalab developments, strong-motion network developments and earthquake activity. During this period the first surface fault unequivocably determined to have accompanied a historic earthquake in eastern North America, occurred in northern Quebec.

  2. Controllable seismic source

    SciTech Connect

    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.

  3. Controllable seismic source

    SciTech Connect

    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.

  4. 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

  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. 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. PMID:16539018

  7. Tectonic models for the Patagonian orogenic curve (southernmost Andes): An appraisal based on analog experiments from the Fuegian thrust-fold belt

    NASA Astrophysics Data System (ADS)

    Torres Carbonell, Pablo J.; Guzmán, Cecilia; Yagupsky, Daniel; Dimieri, Luis V.

    2016-03-01

    Tectonic models for the evolution of the Patagonian orogenic curve were evaluated using analog experiments that considered either a rotational or a non-rotational orogenic backstop, combined with a basement promontory on the foreland cratonic margin. Five different kinematic configurations were used, aiming to evaluate the influence of the Río Chico Arc as a rigid obstacle on the evolution of the Fuegian thrust-fold belt. Rotations, strains and displacement fields obtained from each analog experiment were compared with the structural geology known from the Fuegian thrust-fold belt, in order to appraise the tectonic models that are more consistent with the natural structure. The push of a counterclockwise rotational backstop, combined with the buttressing effect of a foreland promontory, seem of major importance in controlling the final structure and map-view shape of the thrust wedge.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Geothermal induced seismicity program plan

    SciTech Connect

    Not Available

    1981-03-01

    A plan for a National Geothermal Induced Seismicity Program has been prepared in consultation with a panel of experts from industry, academia, and government. The program calls for baseline seismic monitoring in regions of known future geothermal development, continued seismic monitoring and characterization of earthquakes in zones of geothermal fluid production and injection, modeling of the earthquake-inducing mechanism, and in situ measurement of stresses in the geothermal development. The Geothermal Induced Seismicity Program (GISP) will have as its objectives the evaluation of the seismic hazard, if any, associated with geothermal resource exploitation and the devising of a technology which, when properly utilized, will control or mitigate such hazards.

  13. 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

  14. Seismicity of west Texas

    SciTech Connect

    Dumas, D.B.

    1981-01-01

    A four year seismic study has found the Basin and Range province of west Texas and the adjacent area of Mexico to be more seismically active then than heretofore known. A University of Texas five station seismic array around the Marfa Basin has located or detected approximately 800 local and regional earthquakes with S-P times of less than 30 sec. A crustal model for the Basin and Range is derived from natural and artificial sources and contains four layers having velocities of 3.60, 4.93, 6.11, and 6.60 km/sec, respectively, overlying a mantle of 8.37 km/sec. A moderate level of seismic activity has been detected near Van Horn, in the Marfa Basin, and along the Texas-Mexico border between latitudes 30 and 31/sup 0/N. Five earthquake sequences were recorded, two near the Texas-Mexico border and three in the Marfa Basin. Four of these sequences showed quiescent periods in foreshock activity preceding the main shock. On the eastern side of the Marfa Basin a diffuse linear seismic zone may represent an unmapped fault, striking N 50/sup 0/W that coincides with Muehlberger's proposed eastern boundary of Basin and Range faulting. A new epicenter for the Valentine, Texas earthquake of August 16, 1931 has been relocated instrumentally at the northern end of this diffuse zone. Regional and local teleseismic P-wave arrival time anomalies observed for the nearby Gnome underground nuclear explosion of 1961 are used to determine station corrections and thus to locate the new 1931 epicenter at 3.69/sup 0/N, 104.57/sup 0/W. Several estimates of magnitude (m/sub b/) based on intensity data range from 5.6 to 6.4. Fault-plane and composite fault-plane solutions support Muehlberger's hypothesis that the Basin and Range is undergoing extension in a SW-NE direction.

  15. Seismic Rotations Observed with Inertial Seismic Sensors

    NASA Astrophysics Data System (ADS)

    Jean, V.

    2006-12-01

    Recent interest of the seismological community has arisen for possible rotation effects of the Earth on signals recorded by inertial seismometers. Wiechert and Schluter (1903) and more recently Pancha et al. (2000), Igel et al. (2005, 2006) show that, in the teleseismic range, rotations may be neglected and account for less than 0.1% of the translation waves generated by earthquakes. On the contrary, we may see effects of rotation on seismic traces recorded in the near field of an earthquake. As instruments will deliver unsaturated signals in this near field, rotation detection will be more and more frequent. We may observe rotation effects as well in the noise signal at long period. - In the near field, the three components integrated signal of the accelerograms (i.e; velocity signal) diverge and this drift is the effect of an nearly invisible little jump in acceleration signal. The second integrated step diverges and the co-seismic displacement could not be estimated. - By studying the long period noise, we have found that the two horizontal components of some of GEOSCOPE stations with STS-1 seismometer from Streckeisen, present the same noise both in amplitude and in phase with a coherency greater than 95%. This similarity could occur at some stations and not at others and during some time periods. Therefore, the noise has a quite stable horizontal polarisation at N045 during these periods. We may argue that these two separate effects comes from ground rotations and the way they are recorded by seismic instruments. For example, GEOSCOPE stations equipped by STS-2 which have a quite different mechanical structure do not exhibit the polarisation effect. Mechanical pendulums as vertical LaCoste sensor and horizontal 'garden-gate' sensor present effects of rotations on the different translation motions of the mass. Therefore, for the long period noise, a quite probable explanation is that a rotation around the vertical axis acts similarly on the two horizontal

  16. Intermediate depth seismicity - a reflection seismic approach

    NASA Astrophysics Data System (ADS)

    Haberland, C.; Rietbrock, A.

    2004-12-01

    During subduction the descending oceanic lithosphere is subject to metamorphic reactions, some of them associated with the release of fluids. It is now widely accepted, that these reactions and associated dehydration processes are directly related with the generation of intermediate depth earthquakes (dehydration embrittlement). However, the structure of the layered oceanic plate at depth and the location of the earthquakes relative to structural units of the subducting plate (sources within the oceanic crust and/or in the upper oceanic mantle lithosphere?) are still not resolved yet. This is in mainly due to the fact that the observational resolution needed to address these topics (in the range of only a few kilometers) is hardly achieved in field experiments and related studies. Here we study the wavefields of intermediate depth earthquakes typically observed by temporary networks in order to assess their high-resolution potential in resolving structure of the down going slab and locus of seismicity. In particular we study whether the subducted oceanic Moho can be detected by the analysis of secondary phases of local earthquakes (near vertical reflection). Due to the irregular geometry of sources and receivers we apply an imaging technique similar to diffraction stack migration. The method is tested using synthetic data both based on 2-D finite difference simulations and 3-D kinematic ray tracing. The accuracy of the hypocenter location and onset times crucial for the successful application of stacking techniques (coherency) was achieved by the use of relatively relocated intermediate depth seismicity. Additionally, we simulate the propagation of the wavefields at larger distance (wide angle) indicating the development of guided waves traveling in the low-velocity waveguide associated with the modeled oceanic crust. We also present application on local earthquake data from the South American subduction zone.

  17. Fjord circulation and hydrographic structure associated with a rapidly-retreating glacier in the Patagonian Ice Fields

    NASA Astrophysics Data System (ADS)

    Moffat, C. F.

    2013-12-01

    Understanding the structure of buoyant plumes originating from melting glaciers and their interaction with the hydrographic structure and circulation of the surrounding ocean is key to elucidating the role of the ocean in modulating freshwater loss from the continents and to appropriately estimate present and future sea-level rise. Here, hydrographic and current velocity surveys are used to study the freshwater outflow in a fjord adjacent to Jorge Montt, an until recently rapidly (1 km/year) retreating glacier in the southern Patagonian Ice Fields. Surveys were conducted in the Summer of 2010 to 2012, Winter of 2011 and Fall 2012 to provide constraints on seasonal-scale changes. Montt fjord is approximately 20 km long, and is composed of a deep, proximal (to the ice) sub-basin of 350 m maximum depth and a shallower, distal sub-basin of around 100 m depth. Exchange with the 120-km long Baker Channel, the main conduit of exchange for the fjord with the South Eastern Pacific is severely constrained by a v-shaped, 45-m deep sill. During Summer, the freshwater outflow from the glacier mixes with the deep oceanic water found in the fjord to form a buoyant plume. This plume splits into a branch that reaches the surface and forms a relatively thick (10-20 m) brackish layer with salinities of 5 or less, and at least one subsurface branch that forms a horizontally coherent lateral intrusion found everywhere in the deep sub-basin. Results from using a thermodynamical melting model in combination with a linear mixing model suggest that the meltwater in the plume is dominated by subsurface runoff (10 %) with a smaller proportion of submarine melt (1-3 %). The fraction of subsurface runoff is higher in the top 100 m and it increases monotonically towards the surface, while subsurface melting also has a subsurface concentration maximum between 100 and 150 m. Velocity measurements show flow away from the glacier at the surface layer (top 10-20 m) and also at mid-depth, below the

  18. Teaching Reflection Seismic Processing

    NASA Astrophysics Data System (ADS)

    Forel, D.; Benz, T.; Pennington, W. D.

    2004-12-01

    Without pictures, it is difficult to give students a feeling for wave propagation, transmission, and reflection. Even with pictures, wave propagation is still static to many. However, when students use and modify scripts that generate wavefronts and rays through a geologic model that they have modified themselves, we find that students gain a real feeling for wave propagation. To facilitate teaching 2-D seismic reflection data processing (from acquisition through migration) to our undergraduate and graduate Reflection Seismology students, we use Seismic Un*x (SU) software. SU is maintained and distributed by Colorado School of Mines, and it is freely available (at www.cwp.mines.edu/cwpcodes). Our approach includes use of synthetic and real seismic data, processing scripts, and detailed explanation of the scripts. Our real data were provided by Gregory F. Moore of the University of Hawaii. This approach can be used by any school at virtually no expense for either software or data, and can provide students with a sound introduction to techniques used in processing of reflection seismic data. The same software can be used for other purposes, such as research, with no additional expense. Students who have completed a course using SU are well equipped to begin using it for research, as well. Scripts for each processing step are supplied and explained to the students. Our detailed description of the scripts means students do not have to know anything about SU to start. Experience with the Unix operating system is preferable but not necessary -- our notes include Computer Hints to help the beginner work with the Unix operating system. We include several examples of synthetic model building, acquiring shot gathers through synthetic models, sorting shot gathers to CMP gathers, gain, 1-D frequency filtering, f-k filtering, deconvolution, semblance displays and velocity analysis, flattening data (NMO), stacking the CMPs, and migration. We use two real (marine) data sets. One

  19. Comparison of seismic sources for shallow seismic: sledgehammer and pyrotechnics

    NASA Astrophysics Data System (ADS)

    Brom, Aleksander; Stan-Kłeczek, Iwona

    2015-10-01

    The pyrotechnic materials are one of the types of the explosives materials which produce thermal, luminous or sound effects, gas, smoke and their combination as a result of a self-sustaining chemical reaction. Therefore, pyrotechnics can be used as a seismic source that is designed to release accumulated energy in a form of seismic wave recorded by tremor sensors (geophones) after its passage through the rock mass. The aim of this paper was to determine the utility of pyrotechnics for shallow seismic engineering. The work presented comparing the conventional method of seismic wave excitation for seismic refraction method like plate and hammer and activating of firecrackers on the surface. The energy released by various sources and frequency spectra was compared for the two types of sources. The obtained results did not determine which sources gave the better results but showed very interesting aspects of using pyrotechnics in seismic measurements for example the use of pyrotechnic materials in MASW.

  20. 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. 

  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. Canadian seismic agreement

    SciTech Connect

    Wetmiller, R.J.; Lyons, J.A.; Shannon, W.E.; Munro, P.S.; Thomas, J.T.; Andrew, M.D.; Lamontagne, M.; Wong, C.; Anglin, F.M.; Plouffe, M.; Adams, J.; Drysdale, J.A. . Geophysics Div.)

    1990-04-01

    During the period of this report, the contract resources were spent on operation and maintenance of the Eastern Canada Telemetred Network (ECTN), development of special purpose local network systems, servicing and maintenance of the strong-motion seismograph network in eastern Canada, operation of the Ottawa data lab and earthquake monitoring and reporting. Of special note in this period was the final completion of the Sudbury (SLTN) and Charlevoix (CLTN) local networks and the integration of their data processing and analysis requirements in the regular analysis stream for ECTN data. These networks now acquire high quality digital data for detailed analysis of seismic activity and source properties from these two areas, thus effectively doubling the amount of seismic data being received by the Ottawa data lab. 37 refs., 17 figs., 2 tabs.

  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. Active Seismic Imaging Experiment

    NASA Astrophysics Data System (ADS)

    Berge, Patricia A.; Dawson, Phillip B.; Evans, John R.

    In September 1985 the U.S. Geological Survey (USGS) and Lawrence Livermore National Laboratory (LLNL) will conduct an active seismic experiment in the Medicine Lake area of northern California. The work is supported by the Geothermal Research Program of USGS and by the Geothermal and Hydropower Technologies Division of the U.S. Department of Energy. We invite interested organizations or individuals to record our explosions from Medicine Lake volcano and surrounding areas not covered by the USGS-LLNL array.

  5. 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.

  6. 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.

  7. 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.

  8. Seismic basement in Poland

    NASA Astrophysics Data System (ADS)

    Grad, Marek; Polkowski, Marcin

    2015-09-01

    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.

  9. 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.

  10. 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; Ampuero, Jean Paul; Leprince, Sebastien; Michel, Remi

    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

  11. Seismic databases of The Caucasus

    NASA Astrophysics Data System (ADS)

    Gunia, I.; Sokhadze, G.; Mikava, D.; Tvaradze, N.; Godoladze, T.

    2012-12-01

    The Caucasus is one of the active segments of the Alpine-Himalayan collision belt. The region needs continues seismic monitoring systems for better understanding of tectonic processes going in the region. Seismic Monitoring Center of Georgia (Ilia State University) is operating the digital seismic network of the country and is also collecting and exchanging data with neighboring countries. The main focus of our study was to create seismic database which is well organized, easily reachable and is convenient for scientists to use. The seismological database includes the information about more than 100 000 earthquakes from the whole Caucasus. We have to mention that it includes data from analog and digital seismic networks. The first analog seismic station in Georgia was installed in 1899 in the Caucasus in Tbilisi city. The number of analog seismic stations was increasing during next decades and in 1980s about 100 analog stations were operated all over the region. From 1992 due to political and economical situation the number of stations has been decreased and in 2002 just two analog equipments was operated. New digital seismic network was developed in Georgia since 2003. The number of digital seismic stations was increasing and in current days there are more than 25 digital stations operating in the country. The database includes the detailed information about all equipments installed on seismic stations. Database is available online. That will make convenient interface for seismic data exchange data between Caucasus neighboring countries. It also makes easier both the seismic data processing and transferring them to the database and decreases the operator's mistakes during the routine work. The database was created using the followings: php, MySql, Javascript, Ajax, GMT, Gmap, Hypoinverse.

  12. 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.

  13. 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

  14. 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

  15. Seismic monitoring of geomorphic processes

    NASA Astrophysics Data System (ADS)

    Burtin, A.; Hovius, N.; Turowski, J. M.

    2014-12-01

    In seismology, the signal is usually analysed for earthquake data, but these represent less than 1% of continuous recording. The remaining data are considered as seismic noise and were for a long time ignored. Over the past decades, the analysis of seismic noise has constantly increased in popularity, and this has led to develop new approaches and applications in geophysics. The study of continuous seismic records is now open to other disciplines, like geomorphology. The motion of mass at the Earth's surface generates seismic waves that are recorded by nearby seismometers and can be used to monitor its transfer through the landscape. Surface processes vary in nature, mechanism, magnitude and space and time, and this variability can be observed in the seismic signals. This contribution aims to give an overview of the development and current opportunities for the seismic monitoring of geomorphic processes. We first describe the common principles of seismic signal monitoring and introduce time-frequency analysis for the purpose of identification and differentiation of surface processes. Second, we present techniques to detect, locate and quantify geomorphic events. Third, we review the diverse layout of seismic arrays and highlight their advantages and limitations for specific processes, like slope or channel activity. Finally, we illustrate all these characteristics with the analysis of seismic data acquired in a small debris-flow catchment where geomorphic events show interactions and feedbacks. Further developments must aim to fully understand the richness of the continuous seismic signals, to better quantify the geomorphic activity and improve the performance of warning systems. Seismic monitoring may ultimately allow the continuous survey of erosion and transfer of sediments in the landscape on the scales of external forcing.

  16. 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

  17. Borehole seismic modeling

    NASA Astrophysics Data System (ADS)

    Zhen, Tao

    In many borehole seismic experiments, the velocity of the tube wave is higher than that of the surrounding rock shear wave. This fast tube wave creates a strong conical shear wave in the surrounding rock, similar to the Mach wave in supersonic aviation and the Cherenkov radiation in electrodynamics. Many geophysicists have tried to utilize the conical signal in VSP (vertical seismic profiling) and cross borehole data interpretation, using quasi static approximations to model the borehole effect. Two popular quasi static approximations are: the effective source array method for source borehole modeling and the squeeze strain method for receiver borehole modeling. These quasi static approximations are sensible as they qualitatively conform to Hueygen's principle and the typical wavelength of a VSP or a cross borehole seismic experiment is much larger than the borehole radius. However, they have not been quantitatively benchmarked against other non approximation method such as the frequency wave number method. The frequency wave number method is a rigorous, non approximation method for modeling straight boreholes without lengthwise variation. The boreholes may consist of many coaxial, homogeneous and axially symmetric shells. In this thesis, the results of the quasi static approximations are compared to the results obtained from the frequency wave number method. The comparison demonstrates that both the effective source array method and squeeze strain method gives the correct arrival time. The effective source array method gives incorrect amplitude and waveform for direct arrivals and tube waves due to its arbitrary assumption of the elementary source radiation pattern. The squeeze strain method gives fairly accurate amplitude and waveform for P and S direct arrivals but it fails to match the tube wave results obtained from the frequency wave number method. The omission of tube wave dispersion and amplitude loss by the quasi static approximation methods also

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Global overview of subduction seismicity

    NASA Astrophysics Data System (ADS)

    Funiciello, F.; Presti, D.; Heuret, A.; Piromallo, C.

    2013-12-01

    In the framework of the EURYI Project ';Convergent margins and seismogenesis: defining the risk of great earthquakes by using statistical data and modelling', we propose the first global overview of subduction seismicity. Previous studies have been focused on interplate seismicity, intraslab seismicity, upper plate deformation, or relation between interplate and intraslab seismicity, but the three components of subduction seismicity have been never approached in an systematic and exhaustive study. To allow such a study, nodal planes and seismic moments of worldwide subduction-related earthquakes heve been extracted by EHB hypocenter and CMT Harvard catalogues for the period 1976 - 2007. Data were collected for centroid depths between sea level and 700 km and for magnitude Mw 5.5. For each subduction zone, a set of trench-normal transects were constructed choosing a 120km width of the cross-section on each side of a vertical plane and a spacing of 1 degree along the trench. For each of the 505 resulting transects, the whole subduction seismogenic zone was mapped as focal mechanisms projected on to a vertical plane after their faulting type classification according to the Aki-Richards convention. Transect by transect, fist the seismicity that can be considered not related to the subduction process under investigation was removed, then was selected the upper plate seismicity (i.e. earthquakes generated within the upper plate as a result of the subduction process). After deletion from the so obtained event subset of the interplate seismicity as identified in the framework of this project by Heuret et al. (2011), we can be reasonably confident that the remaining seismicity can be related to the subducting plate. Among these earthquakes we then selected the shallow (0-70 km), intermediate (70-300 km) and deep (300-660 km) depth seismicity. Following Heuret et al. (2011), the 505 transects were merged into 62 larger segments that were ideally homogeneous in terms of their

  4. 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

  5. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

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

    2002-10-01

    RSI has access to two synthetic seismic programs: Osiris seismic modeling system provided by Odegaard (Osiris) and synthetic seismic program, developed by SRB, implementing the Kennett method for normal incidence. Achieving virtually identical synthetic seismic traces from these different programs serves as cross-validation for both. The subsequent experiments have been performed with the Kennett normal incidence code because: We have access to the source code, which allowed us to easily control computational parameters and integrate the synthetics computations with our graphical and I/O systems. This code allows to perform computations and displays on a PC in MatLab or Octave environment, which is faster and more convenient. The normal incidence model allows us to exclude from the synthetic traces some of the physical effects that take place in 3-D models (like inhomogeneous waves) but have no relevance to the topic of our investigation, which is attenuation effects on seismic reflection and transmission.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Regional seismic networks upgrade encouraged

    NASA Astrophysics Data System (ADS)

    A partnership between the U.S. National Seismic Network (USNSN)—planned by the U.S. Geological Survey for implementation in the early 1990s—and a group of modernized, independently run regional seismic networks is recommended by the National Research Council in their recent report, “Assessing the Nation's Earthquakes: The Health and Future of Regional Seismograph Networks.” The panel that prepared the report said that together, the facilities would constitute a National Seismic System, a satellite-based network capable of systematically monitoring and analyzing earthquakes throughout the nation within minutes of their occurrence.Regional seismic networks are arrays of tens to hundreds of seismic stations targeted chiefly on seismically active regions. They provide a broad range of data and information, which can be applied to public safety and emergency management, quantification of hazard and risk assessment associated with natural and human-induced earthquakes, surveillance of underground nuclear explosions, basic research on earthquake mechanics and dynamics, seismic wave propagation, seismotectonic processes, earthquake forecasting and prediction, and properties and composition of the crust and the internal structure of the Earth.

  12. 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.

  13. Canadian seismic agreement

    SciTech Connect

    Wetmiller, R.J.; Lyons, J.A.; Shannon, W.E.; Munro, P.S.; Thomas, J.T.; Andrew, M.D.; Lamontagne, M.; Wong, C., Anglin, F.M.; Plouffe, M.; Lapointe, S.P.; Adams, J.; Drysdale, J.A. . Geophysics Div.)

    1990-04-01

    This is the twenty-first progress report under the agreement entitled Canadian Seismic Agreement between the US Nuclear Regulatory Commission (NRC) and the Canadian Commercial Corporation. Activities undertaken by the Geophysics Division of the Geological Survey of Canada (GD/GSC) during the period from July 01, 1988 to June 30, 1989 and supported in part by the NRC agreement are described below under four headings; Eastern Canada Telemetred Network and local network developments, Datalab developments, strong motion network developments and earthquake activity. In this time period eastern Canada experienced its largest earthquake in over 50 years. This earthquake, which has been christened the Saguenay earthquake, has provided a wealth of new data pertinent to earthquake engineering studies in eastern North America and is the subject of many continuing studies, which are presently being carried out at GD and elsewhere. 41 refs., 21 figs., 7 tabs.

  14. Methods for seismic exploration

    SciTech Connect

    Savit, C. H.

    1985-10-01

    Sweeps of seismic signals consisting of pulse trains having a predetermined number of pulses in which the periods or durations of the pulses are randomized and in which the wave shape and relative time displacements of the pulses in different trains provides substantially constant spectral level over a frequency range containing several octaves even though the durations of the pulses correspond to a frequency range not exceeding an octave during the sweep are transmitted through the medium being explored such as an earth formation to receptors such as geophones or hydrophones. Groups of signals contained in less than the entire length of the sweep which are transmitted and which are received can be cross correlated to vary the effective duration of the sweep. The cross correlation output of successively occurring sweeps may be stacked to reduce the side lobe amplitude of the cross correlation outputs from each sweep, from which outputs seismograms may be constructed.

  15. 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.

  16. 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

  17. 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.

  18. 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

  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. Transdimensional Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Bodin, T.; Sambridge, M.

    2009-12-01

    In seismic imaging the degree of model complexity is usually determined by manually tuning damping parameters within a fixed parameterization chosen in advance. Here we present an alternative methodology for seismic travel time tomography where the model complexity is controlled automatically by the data. In particular we use a variable parametrization consisting of Voronoi cells with mobile geometry, shape and number, all treated as unknowns in the inversion. The reversible jump algorithm is used to sample the transdimensional model space within a Bayesian framework which avoids global damping procedures and the need to tune regularisation parameters. The method is an ensemble inference approach, as many potential solutions are generated with variable numbers of cells. Information is extracted from the ensemble as a whole by performing Monte Carlo integration to produce the expected Earth model. The ensemble of models can also be used to produce velocity uncertainty estimates and experiments with synthetic data suggest they represent actual uncertainty surprisingly well. In a transdimensional approach, the level of data uncertainty directly determines the model complexity needed to satisfy the data. Intriguingly, the Bayesian formulation can be extended to the case where data uncertainty is also uncertain. Experiments show that it is possible to recover data noise estimate while at the same time controlling model complexity in an automated fashion. The method is tested on synthetic data in a 2-D application and compared with a more standard matrix based inversion scheme. The method has also been applied to real data obtained from cross correlation of ambient noise where little is known about the size of the errors associated with the travel times. As an example, a tomographic image of Rayleigh wave group velocity for the Australian continent is constructed for 5s data together with uncertainty estimates.

  1. 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.

  2. 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

  3. Tilt and seismicity changes in the Shumagin seismic gap

    SciTech Connect

    Beavan, J.; Hauksson, E.; McNutt, S.R.; Bilham, R.; Jacob, K.H.

    1983-10-21

    Changes in the ground surface tilt and in the rate of seismicity indicate that an aseismic deformation event may have occurred between 1978 and 1980 along the plate boundary in the eastern Aleutians, Alaska, within the Shumagin seismic gap. Pavlof Volcano was unusually quiescent during this period. The proposed event would cause an increase of stress on the shallow locked portion of the plate boundary, bringing it closer to rupture in a great earthquake.

  4. From Induced Seismicity to Direct Time-Dependent Seismic Hazard

    NASA Astrophysics Data System (ADS)

    Convertito, V.; Maercklin, N.; Sharma, N.; Zollo, A.

    2012-12-01

    The growing installation of industrial facilities for subsurface exploration worldwide requires continuous refinements in understanding both the mechanisms by which seismicity is induced by field operations and the related seismic hazard. Particularly in proximity of densely populated areas, induced low-to-moderate magnitude seismicity characterized by high-frequency content can be clearly felt by the surrounding inhabitants and, in some cases, may produce damage. In this respect we propose a technique for time-dependent probabilistic seismic hazard analysis to be used in geothermal fields as a monitoring tool for the effects of on-going field operations. The technique integrates the observed features of the seismicity induced by fluid injection and extraction with a local ground-motion prediction equation. The result of the analysis is the time-evolving probability of exceedance of peak ground acceleration (PGA), which can be compared with selected critical values to manage field operations. To evaluate the reliability of the proposed technique, we applied it to data collected in The Geysers geothermal field in northern California between 1 September 2007 and 15 November 2010. We show that the period considered the seismic hazard at The Geysers was variable in time and space, which is a consequence of the field operations and the variation of both seismicity rate and b-value. We conclude that, for the exposure period taken into account (i.e., two months), as a conservative limit, PGA values corresponding to the lowest probability of exceedance (e.g., 30%) must not be exceeded to ensure safe field operations. We suggest testing the proposed technique at other geothermal areas or in regions where seismicity is induced, for example, by hydrocarbon exploitation or carbon dioxide storage.

  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. Seismic background noise at the Norwegian Regional Seismic Array

    SciTech Connect

    Breding, D.R.

    1987-10-01

    The System Control and Receiving Station (SCARS) has been collecting spectral history data on the Regional Seismic Test Network (RSTN) since 1981 and on the Norwegian Regional Seismic Array (NRSA) since it was installed in 1984. This report details the spectral history data for the NRSA through 1986. The appendix contains spectral history data for all five RSTN stations from the time they were installed until their deactivation in September 1986.

  7. Seismic engineering -- 1996. PVP-volume 340

    SciTech Connect

    Saleem, M.A.; Aggarwal, M.C.

    1996-12-01

    The 37 papers in this volume have been arranged under the following topical sections: advanced methods in seismic engineering (7 papers); high level dynamic response of piping systems (5); equipment seismic qualification (6); soil structure interaction (3); advanced seismic technology in Asian countries (8); developments in seismic codes and standards (8); and a panel discussion on the review of current issues by the Special Working Group on seismic rules. Papers have been processed separately for inclusion on the data base.

  8. 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.

  9. 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.

  10. Static behaviour of induced seismicity

    NASA Astrophysics Data System (ADS)

    Mignan, A.

    2015-12-01

    The standard paradigm to describe seismicity induced by fluid injection is to apply nonlinear diffusion dynamics in a poroelastic medium. I show that the spatiotemporal behaviour and rate evolution of induced seismicity can, instead, be expressed by geometric operations on a static stress field produced by volume change at depth. I obtain laws similar in form to the ones derived from poroelasticity while requiring a lower description length. Although fluid flow is known to occur in the ground, it is not pertinent to the behaviour of induced seismicity. The proposed model is equivalent to the static stress model for tectonic foreshocks generated by the Non-Critical Precursory Accelerating Seismicity Theory. This study hence verifies the explanatory power of this theory outside of its original scope.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Seismic Station Functionality Improvements of Seismic Network of Slovenia

    NASA Astrophysics Data System (ADS)

    Sincic, Peter; Tasic, Izidor; Mali, Marko; Pancur, Luka; Vidrih, Renato

    2010-05-01

    The Environmental Agency of the Republic of Slovenia, the Office of Seismology and Geology is responsible for the fast and reliable information about earthquakes, originating in the area of Slovenia and nearby. The Seismic Network of Slovenia, which covers the entire Slovenian territory, involving an area of 20,256 km2, consists of 26 seismic stations equipped with broadband seismometers (CMG-40T, CMG-3ESPC, CMG-3T and STS2) and Quanterra Q730 data loggers. The seismic data is transmitted in real-time to the Data Center in Ljubljana (DCL). Leased lines, xDSL and satellite communication are used for data transfer from stations to DCL. When an event occurs main earthquake parameters (magnitude and the location of the epicenter) can be evaluated at sufficient accuracy only if data from several seismic stations is available. In case of temporary communication failure loss of important seismic data can occur. The duration of communication failure, which exceeds 2 hours can cause data loss. This is due to low memory storage of Quanterra Q730 acquisition unit. In this paper our solution for extending storage capabilities of particular seismic station to several months is presented (momentarily the storage capabilities of particular seismic station lies between 1 and 2 hours). To extend storage capabilities we used a special Industrial Computer (JetBox 8100), which runs on Linux. To collect seismic data from the Q730 unit the acquisition software SeiComP is used. The combination of Q730 and JetBox 8100 assures that in case of temporary communication failure there will be no data loss. Seismic data is simply retrieved from JetBox 8100 (from ring buffer that is generated by SeiComP acquisition software) after communication is once again established. Moreover, an advanced state of health system was build and installed on JetBox 8100, that makes identifying, predicting and solving of different problems quick and effective. With combining Q730 data logger and JetBox 8100 we did

  16. 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.

  17. Seismicity of the Jalisco Block

    NASA Astrophysics Data System (ADS)

    Nunez-Cornu, F. J.; Rutz, M.; Camarena-Garcia, M.; Trejo-Gomez, E.; Reyes-Davila, G.; Suarez-Plascencia, C.

    2002-12-01

    In April 2002 began to transmit the stations of the first phase of Jalisco Telemetric Network located at the northwest of Jalisco Block and at the area of Volcan de Fuego (Colima Volcano), in June were deployed four additional MarsLite portable stations in the Bahia de Banderas area, and by the end of August one more portable station at Ceboruco Volcano. The data of these stations jointly with the data from RESCO (Colima Telemetric Network) give us the minimum seismic stations coverage to initiate in a systematic and permanent way the study of the seismicity in this very complex tectonic region. A preliminary analysis of seismicity based on the events registered by the networks using a shutter algorithm, confirms several important features proposed by microseismicity studies carried out between 1996 and 1998. A high level of seismicity inside and below of Rivera plate is observed, this fact suggest a very complex stress pattern acting on this plate. Shallow seismicity at south and east of Bahia de Banderas also suggest a complex stress pattern in this region of the Jalisco Block, events at more than 30 km depth are located under the mouth of the bay and in face of it, a feature denominated Banderas Boundary mark the change of the seismic regime at north of this latitude (20.75°N), however some shallow events were located at the region of Nayarit.

  18. Seismic volumetric flattening and segmentation

    NASA Astrophysics Data System (ADS)

    Lomask, Jesse

    Two novel algorithms provide seismic interpretation solutions that use the full dimensionality of the data. The first is volumetric flattening and the second is image segmentation for tracking salt boundaries. Volumetric flattening is an efficient full-volume automatic dense-picking method applied to seismic data. First local dips (step-outs) are calculated over the entire seismic volume. The dips are then resolved into time shifts (or depth shifts) in a least-squares sense. To handle faults (discontinuous reflections), I apply a weighted inversion scheme. Additional information is incorporated in this flattening algorithm as geological constraints. The method is tested successfully on both synthetic and field data sets of varying degrees of complexity including salt piercements, angular unconformities, and laterally limited faults. The second full-volume interpretation method uses normalized cuts image segmentation to track salt interfaces. I apply a modified version of the normalized cuts image segmentation (NCIS) method to partition seismic images along salt interfaces. The method is capable of tracking interfaces that are not continuous, where conventional horizon tracking algorithms may fail. This method partitions the seismic image into two groups. One group is inside the salt body and the other is outside. Where the two groups meet is the salt boundary. By imposing bounds and by distributing the algorithm on a parallel cluster, I significantly increase efficiency and robustness. This method is demonstrated to be effective on both 2D and 3D seismic data sets.

  19. 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.

  20. 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.

  1. Seismic tracking of Hurricane Sandy

    NASA Astrophysics Data System (ADS)

    Chen, X.; Wen, L.

    2013-12-01

    Very weak, narrow band seismic signals excited by Hurricane Sandy are detected in cross-correlations of continuous waveforms recorded by stations in eastern United States, at the end of October 2012. We analyze propagational properties of the signal and track the source locations using travel-time difference residual projection, from 26 October to 1 November 2012. We find that (1) the seismic signals driven by Hurricane Sandy are azimuthal dependent. Signals are correlated only within close azimuths from the source, (2) seismic signals propagate as Rayleigh surface wave with an average velocity of about 3.3 km/s, and (3) the inferred seismic source locations follow the path of Sandy before UTC 2012.10.30 12:00:00(about half a day after its landfall in New Jersey), but then deviate from the hurricane center and stay in the coastal area near New England for another 12 hours after the hurricane dissipated. Our research discovers the properties of seismic source excited by Hurricane Sandy and demonstrates the capability of using seismic data to real-time track a hurricane and estimate its direct impacts and the subsequent disasters after it dissipates.

  2. 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.

  3. seismicity and seismotectonics of Libya

    NASA Astrophysics Data System (ADS)

    Ben Suleman, abdunnur

    2015-04-01

    Libya, located at the central Mediterranean margin of the African shield, underwent many episodes of orogenic activity that shaped its geological setting. The present day deformation of Libya is the result of the Eurasia-Africa continental collision. The tectonic evolution of Libya has yielded a complex crustal structure that is composed of a series of basins and uplifts. This study aims to explain in detail the seismicity and seismotectonics of Libya using new data recorded by the recently established Libyan National Seismograph Network (LNSN) incorporating other available geophysical and geological information. Detailed investigations of the Libyan seismicity indicates that Libya has experienced earthquakes of varying magnitudes The seismic activity of Libya shows dominant trends of Seismicity with most of the seismic activity concentrated along the northern coastal areas. Four major clusters of Seismicity were quit noticeable. Fault plane solution was estimated for 20 earthquakes recorded by the Libyan National Seismograph Network in northwestern and northeastern Libya. Results of fault plane solution suggest that normal faulting was dominant in the westernmost part of Libya; strike slip faulting was dominant in northern-central part of Libya. The northern-eastern part of the country suggests that dip-dip faulting were more prevalent.

  4. Time dependent seismic hazard

    NASA Astrophysics Data System (ADS)

    Polidoro, B.; Iervolino, I.; Chioccarelli, E.; Giorgio, M.

    2012-04-01

    Probabilistic seismic hazard is usually computed trough a homogeneous Poisson process that even though it is a time-independent process it is widely used for its very convenient properties. However, when a single fault is of concern and/or the time scale is different from that of the long term, time-dependent processes are required. In this paper, different time-dependent models are reviewed with working examples. In fact, the Paganica fault (in central Italy) has been considered to compute both the probability of occurrence of at least one event in the lifespan of the structure, as well as the seismic hazard expressed in terms of probability of exceedance of an intensity value in a given time frame causing the collapse of the structure. Several models, well known or novel application to engineering hazard have been considered, limitation and issues in their applications are also discussed. The Brownian Passage Time (BPT) model is based on a stochastic modification of the deterministic stick-slip oscillator model for characteristic earthquakes; i.e., based on the addition of random perturbations (a Gaussian white noise) to the deterministic load path predicted by elastic rebound theory. This model assumes that the load state is at some ground level immediately after an event, increases steadly over time, reaches a failure threshold and relaxes instantaneously back to the ground level. For this model also a variable threshold has been considered to take into account the uncertainty of the threshold value. For the slip-predictable model it is assumed that the stress accumulates at a constant rate starting from some initial stress level. Stress is assumed to accumulate for a random period of time until an earthquake occurs. The size of the earthquake is governed by the stress release and it is a function of the elapsed time since the last event. In the time-predictable model stress buildup occurs at a constant rate until the accumulated stress reaches a threshold

  5. 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.

  6. A university-developed seismic source for shallow seismic surveys

    NASA Astrophysics Data System (ADS)

    Yordkayhun, Sawasdee; Na Suwan, Jumras

    2012-07-01

    The main objectives of this study were to (1) design and develop a low cost seismic source for shallow seismic surveys and (2) test the performance of the developed source at a test site. The surface seismic source, referred to here as a university-developed seismic source is based upon the principle of an accelerated weight drop. A 30 kg activated mass is lifted by a mechanical rack and pinion gear and is accelerated by a mounted spring. When the mass is released from 0.5 m above the surface, it hits a 30 kg base plate and energy is transferred to the ground, generating a seismic wave. The developed source is portable, environmentally friendly, easy to operate and maintain, and is a highly repeatable impact source. To compare the developed source with a sledgehammer source, a source test was performed at a test site, a study site for mapping a major fault zone in southern Thailand. The sledgehammer and the developed sources were shot along a 300 m long seismic reflection profile with the same parameters. Data were recorded using 12 channels off-end geometry with source and receiver spacing of 5 m, resulting in CDP stacked sections with 2.5 m between traces. Source performances were evaluated based on analyses of signal penetration, frequency content and repeatability, as well as the comparison of stacked sections. The results show that both surface sources are suitable for seismic studies down to a depth of about 200 m at the site. The hammer data are characterized by relatively higher frequency signals than the developed source data, whereas the developed source generates signals with overall higher signal energy transmission and greater signal penetration. In addition, the repeatability of the developed source is considerably higher than the hammer source.

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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 (

  12. 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.

  13. 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.

  14. Magnitude, geomorphologic response and climate links of lake level oscillations at Laguna Potrok Aike, Patagonian steppe (Argentina)

    NASA Astrophysics Data System (ADS)

    PASADO science Team Kliem, P.; Buylaert, J. P.; Hahn, A.; Mayr, C.; Murray, A. S.; Ohlendorf, C.; Veres, D.; Wastegård, S.; Zolitschka, B.

    2013-07-01

    Laguna Potrok Aike is a large maar lake located in the semiarid steppe of southern Patagonia known for its Lateglacial and Holocene lake level fluctuations. Based on sedimentary, seismic and geomorphological evidences, the lake level curve is updated and extended into the Last Glacial period and the geomorphological development of the lake basin and its catchment area is interpreted.Abrasion and lake level oscillations since at least ˜50 ka caused concentric erosion of the surrounding soft rocks of the Miocene Santa Cruz Formation and expanded the basin diameter by approximately 1 km. A high lake level and overflow conditions of the lake were dated by luminescence methods and tephra correlation to the early Lateglacial as well as to ˜45 ka. The lowest lake level of record occurred during the mid-Holocene. A further lake level drop was probably prevented by groundwater supply. This low lake level eroded a distinct terrace into lacustrine sediments. Collapse of these terraces probably caused mass movement deposits in the profundal zone of the lake. After the mid-Holocene lake level low stand a general and successive transgression occurred until the Little Ice Age maximum; i.e. ca 40 m above the local groundwater table. Frequent lake level oscillations caused deflation of emerged terraces only along the eastern shoreline due to prevailing westerly winds. Preservation of eolian deposits might be linked to relatively moist climate conditions during the past 2.5 ka.Precisely dated lake level reconstructions in the rain-shadow of the Andes document high Last Glacial and low Holocene lake levels that could suggest increased precipitation during the Last Glacial period. As permafrost in semiarid Patagonia is documented and dated to the Last Glacial period we argue that the frozen ground might have increased surficial runoff from the catchment and thus influenced the water balance of the lake. This is important for investigating the glacial to Holocene latitudinal shift

  15. Magnitude, geomorphologic response and climate links of lake level oscillations at Laguna Potrok Aike, Patagonian steppe (Argentina)

    NASA Astrophysics Data System (ADS)

    Kliem, P.; Buylaert, J. P.; Hahn, A.; Mayr, C.; Murray, A. S.; Ohlendorf, C.; Veres, D.; Wastegård, S.; Zolitschka, B.; The Pasado Science Team

    2013-07-01

    Laguna Potrok Aike is a large maar lake located in the semiarid steppe of southern Patagonia known for its Lateglacial and Holocene lake level fluctuations. Based on sedimentary, seismic and geomorphological evidences, the lake level curve is updated and extended into the Last Glacial period and the geomorphological development of the lake basin and its catchment area is interpreted. Abrasion and lake level oscillations since at least ˜50 ka caused concentric erosion of the surrounding soft rocks of the Miocene Santa Cruz Formation and expanded the basin diameter by approximately 1 km. A high lake level and overflow conditions of the lake were dated by luminescence methods and tephra correlation to the early Lateglacial as well as to ˜45 ka. The lowest lake level of record occurred during the mid-Holocene. A further lake level drop was probably prevented by groundwater supply. This low lake level eroded a distinct terrace into lacustrine sediments. Collapse of these terraces probably caused mass movement deposits in the profundal zone of the lake. After the mid-Holocene lake level low stand a general and successive transgression occurred until the Little Ice Age maximum; i.e. ca 40 m above the local groundwater table. Frequent lake level oscillations caused deflation of emerged terraces only along the eastern shoreline due to prevailing westerly winds. Preservation of eolian deposits might be linked to relatively moist climate conditions during the past 2.5 ka. Precisely dated lake level reconstructions in the rain-shadow of the Andes document high Last Glacial and low Holocene lake levels that could suggest increased precipitation during the Last Glacial period. As permafrost in semiarid Patagonia is documented and dated to the Last Glacial period we argue that the frozen ground might have increased surficial runoff from the catchment and thus influenced the water balance of the lake. This is important for investigating the glacial to Holocene latitudinal shift

  16. Infection patterns of Tylodelphys barilochensis and T. crubensis (Trematoda: Diplostomatidae) metacercariae in Galaxias maculatus (Osmeriformes: Galaxiidae) from two Patagonian lakes and observations on their geographical distribution in the southern Andean region, Argentina.

    PubMed

    Flores, Verónica; Liliana, Semenas

    2002-12-01

    In the Patagonian Andean region, 2 species of diplostomatids parasitize the brains of Galaxias maculatus. The purpose of this study was to evaluate seasonal variation, spatial variation, and association with host age in the transmission of Tylodelphys barilochensis and T. crubensis in several oligotrophic lakes in Argentinian Patagonia. Fishes were captured monthly in Lake Gutiérrez and bimonthly in Lake Escondido. One summer or autumn sample was also taken in several other Patagonian lakes. Infection parameters were calculated and compared using nonparametric tests. The 2 species co-occurred in most of the sampled lakes, with high values of prevalence and mean intensity. In Lake Gutiérrez and Lake Escondido, the intensity of both diplostomatid species did not show significant differences between sexes and co-varied with host length. All age classes were infected; maximum prevalence values were reached before maximum mean intensity values in the 1-yr age class. A seasonal pattern of prevalence and mean intensity of the 2 parasite species with autumn mean intensity values differing significantly from those of the other seasons was evident only in Lake Gutiérrez. PMID:12537107

  17. 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

  18. 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.

  19. 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.

  20. Static behaviour of induced seismicity

    NASA Astrophysics Data System (ADS)

    Mignan, Arnaud

    2016-04-01

    The standard paradigm to describe seismicity induced by fluid injection is to apply non-linear diffusion dynamics in a poroelastic medium. I show that the spatio-temporal behaviour and rate evolution of induced seismicity can, instead, be expressed by geometric operations on a static stress field produced by volume change at depth. I obtain laws similar in form to the ones derived from poroelasticity while requiring a lower description length. Although fluid flow is known to occur in the ground, it is not pertinent to the geometrical description of the spatio-temporal patterns of induced seismicity. The proposed model is equivalent to the static stress model for tectonic foreshocks generated by the Non-Critical Precursory Accelerating Seismicity Theory. This study hence verifies the explanatory power of this theory outside of its original scope and provides an alternative physical approach to poroelasticity for the modelling of induced seismicity. The applicability of the proposed geometrical approach is illustrated for the case of the 2006, Basel enhanced geothermal system stimulation experiment. Applicability to more problematic cases where the stress field may be spatially heterogeneous is also discussed.

  1. 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.

  2. 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.

  3. 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. PMID:16810253

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Analysis of the ambient seismic noise at Bulgarian seismic stations

    NASA Astrophysics Data System (ADS)

    Dimitrova, Liliya; Nikolova, Svetlana

    2010-05-01

    Modernization of Bulgarian National Seismological Network has been performed during a month in 2005. Broadband seismometers and 24-bits digital acquisition systems with dynamic range more than 132dB type DAS130-01 produced by RefTek Inc. were installed at the seismic stations from the existing analog network. In the present study the ambient seismic noise at Bulgarian National Digital Seismological Network (BNDSN) stations is evaluated. In order to compare the performance of the network against international standards the detail analysis of the seismic noise was performed using software and models that are applied in the international practice. The method of McNamara and Bulland was applied and the software code PDFSA was used to determine power spectral density function (PSD) of the background noise and to evaluate the probability density function (PDF). The levels of the ambient seismic noise were determined and the full range of the factors influencing the quality of the data and the performance of a seismic station was analyzed. The estimated PSD functions were compared against two models for high (NHNM) and low (NLNM) noise that are widely used in seismological practice for seismic station monitoring qualities assessment. The mode PDF are used to prepare annual, seasonal, diurnal and frequency analyses of the noise levels at BNDSN stations. The annual analysis shows that the noise levels at the Northern Bulgarian stations are higher than the ones at Central and Southern stations for the microseisms' periods (1sec -7sec). It is well observable at SS PRV and PSN located near Black sea. This is due to the different geological conditions of the seismic stations as well. For the periods of "cultural" noise the power distribution depends on the type of noise sources and as a rule is related to human activities at or near the Earth surface. Seismic stations MPE, VTS and MMB have least mode noise levels and the noisiest stations are PGB, PVL и JMB. The seasonal

  10. 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.

  11. Statistical models for seismic magnitude

    NASA Astrophysics Data System (ADS)

    Christoffersson, Anders

    1980-02-01

    In this paper some statistical models in connection with seismic magnitude are presented. Two main situations are treated. The first deals with the estimation of magnitude for an event, using a fixed network of stations and taking into account the detection and bias properties of the individual stations. The second treats the problem of estimating seismicity, and detection and bias properties of individual stations. The models are applied to analyze the magnitude bias effects for an earthquake aftershock sequence from Japan, as recorded by a hypothetical network of 15 stations. It is found that network magnitudes computed by the conventional averaging technique are considerably biased, and that a maximum likelihood approach using instantaneous noise-level estimates for non-detecting stations gives the most consistent magnitude estimates. Finally, the models are applied to evaluate the detection characteristics and associated seismicity as recorded by three VELA arrays: UBO (Uinta Basin), TFO (Tonto Forest) and WMO (Wichita Mountains).

  12. Seismic interferometry for temporal monitoring

    NASA Astrophysics Data System (ADS)

    Nakata, Norimitsu

    Seismic interferometry, where one computes coherency of waves between two or more receivers and averages over many sources, is a technique of signal processing to reconstruct wavefields. This technique is used in geophysics, especially exploration geophysics and seismology. After more than a half century from the first study related to seismic interferometry (although the name of seismic interferometry has been used for approximately the last 15 years), researchers have developed this technique for many aspects: using multiples for increasing illuminations, enhancement of survey areas, ambient-noise analysis, and removal of the imprint of a complicated overburden. In this dissertation, I focus on the advantages of seismic interferometry for time-lapse measurements. Measurements of temporal changes yield beneficial information of fluid flow, crustal deformation, temperature, and/or stress. Estimation of temporal changes using active sources is, however, technically and economically challenging. Because seismic interferometry reconstruct waves that would have been recorded with a repeatable active sources using only receivers, this technique is appropriate for temporal monitoring. With seismic interferometry, one obtains some advantages that include canceling the complexity of wave propagation to a virtual source, creating virtual shear-wave (S-wave) sources (active S sources are expensive), and using waves that are not usable for active sources (e.g., ambient noise and multiples). I seek applications of seismic interferometry in a variety of topics (i.e., seismology, structural engineering, and exploration geophysics), and develop and/or modify several techniques of seismic interferometry for each application. Some chapters focus on developing techniques of seismic interferometry, and other chapters aim to estimate and interpret temporal changes with the developed techniques. For passive seismic sources, deconvolution-based seismic interferometry has better

  13. Cross well seismic reservoir characterization

    SciTech Connect

    Sheline, H.E.

    1995-08-01

    A striking example of how Cross Well Seismic reflection data can help characterize a reservoir, has resulted from an ongoing Multi-Discipline study of the carbonate Mishrif reservoir offshore Dubai, U.A.E. Because the study objectives include a more detailed description of intra reservoir structure and layering, Dubai Petroleum Company (DPC) analyzed the feasibility of Cross Well Seismic (CWS) and decided to acquire two surveys between three wells 337 to 523 feet apart. DPC has concluded that CWS can be cost effectively acquired offshore, in a Carbonate reservoir; as well as processed and interpreted. However, generally it is not often easy to acquire cross well seismic when and where it will be most useful. A CWS survey can provide multiple images such as a velocity Tomogram, P-wave reflections, and S-wave reflections. To date, Tomograms and P-wave reflections have been produced, and the reflection data has proven to be the most useful for reservoir characterization. Cross Well Seismic Reflection data have provided a level of vertical seismic reflection resolution of around 2 feet, which is more than 10 times better than surface seismic data (2D or 3D). The increase in vertical resolution has provided important detailed information about the reservoir, it`s continuity/heterogeneity; it`s detailed structure, stratigraphy and layering; and definition of any faults with more than 2 feet of offset. The CWS has shown detailed intra Mishrif reflectors. These reflectors have verified or changed detailed correlations between well bores, and show significant intra Mishrif thinning. These reflectors imply time stratigraphic layering which is consistent with tracer study results and regional sequence stratigraphy. This new data will be used to improve the reservoir model description.

  14. 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

  15. 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

  16. Repeating seismic events in China.

    PubMed

    Schaff, David P; Richards, Paul G

    2004-02-20

    About 10% of seismic events in and near China from 1985 to 2000 were repeating events not more than about 1 kilometer from each other. We cross-correlated seismograms from approximately 14,000 earthquakes and explosions and measured relative arrival times to approximately 0.01 second, enabling lateral location precision of about 100 to 300 meters. Such precision is important for seismic hazard studies, earthquake physics, and nuclear test ban verification. Recognition and measurement of repeating signals in archived data and the resulting improvement in location specificity quantifies the inaccuracy of current procedures for picking onset times and locating events. PMID:14976310

  17. 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.

  18. Mud Volcanoes, Geodynamics and Seismicity

    NASA Astrophysics Data System (ADS)

    Martinelli, Giovanni; Panahi, Behrouz

    The purpose of the book is to link together knowledge obtained in the observation of mud volcanism and local seismicity. Geological, Seismological, Geophysical and Geochemical parameters are considered. The book represents the modern state of the art after many decades of observations. The book fills an editorial gap and improves knowledge in the fields of natural risks and energy resources. Mud volcanism occurs both onshore and offshore in many places of the world. Mud volcanic phenomena have been to date described by local monographs or by articles published in scientific journals and no books were published on topics highlighting the link between mud volcanism, geodynamics and seismicity.

  19. Seismic Imaging Processing and Migration

    Energy Science and Technology Software Center (ESTSC)

    2000-06-26

    Salvo is a 3D, finite difference, prestack, depth migration code for parallel computers. It is also capable of processing 2D and poststack data. The code requires as input a seismic dataset, a velocity model and a file of parameters that allows the user to select various options. The code uses this information to produce a seismic image. Some of the options available to the user include the application of various filters and imaging conditions. Themore » code also incorporates phase encoding (patent applied for) to process multiple shots simultaneously.« less

  20. 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

  1. Observations on seismic probabilistic risk assessments (PRAs)

    SciTech Connect

    Smith, P.D.

    1984-06-01

    In this paper we present observations on a number of issues related to seismic PRAs including: strengths and weaknesses of seismic PRAs; uncertainty, sensitivity and variability; common misconceptions; possible improvements in seismic safety acceptance criteria; recommended modifications to the NRC approach to safety goals; and major problems. Some specific examples are provided.

  2. Seismic, shock, and vibration isolation - 1988

    SciTech Connect

    Chung, H. ); Mostaghel, N. )

    1988-01-01

    This book contains papers presented at a conference on pressure vessels and piping. Topics covered include: Design of R-FBI bearings for seismic isolation; Benefits of vertical and horizontal seismic isolation for LMR nuclear reactor units; and Some remarks on the use and perspectives of seismic isolation for fast reactors.

  3. 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.

  4. 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.

  5. 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

  6. Laboratory seismic anisotropy in mylonites

    NASA Astrophysics Data System (ADS)

    Almqvist, B. S. G.; Herwegh, M.; Hirt, A. M.; Ebert, A.; Linckens, J.; Precigout, J.; Leiss, B.; Walter, J. M.; Burg, J.-P.

    2012-04-01

    Tectonic strain is often accommodated along narrow zones in the Earth's crust and upper mantle, and these high-strain zones represent an important mechanical and rheological component in geodynamics. In outcrop we observe the intense deformation along and across these structures. But at depth, in the mid and lower crust, and in the mantle, we are dependent on geophysical methods for analysis of structures, such as seismic reflection and refraction surveys. A natural progression has therefore been to understand the remote geophysical signal in terms of laboratory ultrasonic pulse transmission measurements on rock cores, collected in the field or from borehole drill core. Here we first present a brief review that consider key studies in the area of laboratory seismic measurements in strongly anisotropic rocks, ranging from calcite mylonites to metapelites. In the second part we focus attention on ongoing research projects targetting laboratory seismic anisotropy in mylonitized rocks, and associated challenges. Measurements of compressional (P) and shear (S) waves were made at high confining pressure (up to 5 kbar). Mineral texture analysis was performed with electron backscatter diffraction (EBSD) and neutron texture diffraction to determine crystallographic preferred orientation (CPO). So-called "rock-recipe" models are used to calculate seismic anisotropy, which consider the elastic properties of minerals that constitutes the rock, and their respective CPO. However, the outcome of such models do not always simply correspond to the measured seismic anisotropy. Differences are attributed to several factors, such as grain boundaries, mineral microstructures including shape-preferred orientation (SPO), micro-cracks and pores, and grain-scale stress-strain conditions. We highlight the combination of these factors in case studies on calcite and peridotite mylonites. In calcite mylonites, sampled in the Morcles nappe shear zone, the measured seismic anisotropy generally

  7. Towards a model of postglacial biogeography in shallow marine species along the Patagonian Province: lessons from the limpet Nacella magellanica (Gmelin, 1791)

    PubMed Central

    2012-01-01

    suggest that fjords and channels represent the areas most recently colonized by the species. Hence recolonization seems to follow a west to east direction to areas that were progressively deglaciated. Significant genetic differences among Pacific, Atlantic and Falkland/Malvinas Islands populations may be also explained through disparities in their respective glaciological and geological histories. The Falkland/Malvinas Islands, more than representing a glacial refugium for the species, seems to constitute a sink area considering the strong asymmetric gene flow detected from Pacific to Atlantic sectors. These results suggest that historical and contemporary processes represent the main factors shaping the modern biogeography of most shallow marine benthic invertebrates inhabiting the Patagonian Province. PMID:22871029

  8. Seismic maps foster landmark legislation

    USGS Publications Warehouse

    Borcherdt, Roger D.; Brown, Robert B.; Page, Robert A.; Wentworth, Carl M.; Hendley, James W., II

    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.

  9. 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.

  10. 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.

  11. 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.

  12. Seismic performance of underground facilities

    SciTech Connect

    Marine, I W

    1982-01-01

    A workshop was held in Augusta, GA, February 11-13, 1981 to review and assess the state-of-the-art for determining and predicting earthquake damage to underground facilities. The papers presented related to data collection and analysis, modeling, and repository design. Discussion groups addressed seismology, rock mechanics and hydrology, modeling, design, and licensing, siting, and tectonics. Most scientists in attendance believed that enough was known to proceed with site selection, design, and licensing of a waste repository. However, there was recognition of several items of research that would enhance understanding of the subsurface effects of seismicity. In general, the subsurface effects of earthquakes are substantially less than their surface effects. This conclusion is supported by both observation and by modeling studies. The absence of wave reflections, the absence of high flexural stresses, and the absence of poor soil conditions contribute to the improved seismic performance of subsurface facilities. Seismic considerations for geologic disposal of nuclear waste vary with the phase of operation. During construction and waste loading, the primary concern is for the safety of onsite personnel. However, during long-term waste storage, the principal interest is in the migration of contaminants due to seismic cracking and enhancement of permeability. Backfilling the storage facility will mitigate this effect.

  13. Sealevel, global seismicity and tectonics

    NASA Astrophysics Data System (ADS)

    Melini, D.; Piersanti, A.

    2004-12-01

    Current estimates of secular relative sealevel variations give a uniform rise in the range 1.5-2.0 mm/yr over the last century. The main climatological contributions come from water volume increase due to thermal expansion and water mass increase due to ice melting. The volume increase accounts for a rise of about 0.5 mm/yr while the mass increase is thought to be even smaller. Since earthquakes produce vertical crust displacements and geoid height variations, they change also the relative sea level. On a global scale the combined effect of world seismicity is responsible for a mean relative sealevel variation of 0.1 mm/yr, with a large regional variability. This value is of the same order of magnitude of the climatological contributions and, in sites with strong seismotectonical activity, may represent the dominant contribution of relative sealevel variations measured by tide gauges. The recent measures of sealevel obtained by satellite altimetry show a wide regional variation of sealevel trends over the oceanic surfaces. These measurements, when compared with the global seismic driven signal, show a strong correlation of the geographical distribution of trend signs, while the absolute values of seismic RSL trends are much smaller in magnitude. The physical processes underlying the observed correlation need a deeper analysis to be understood, but we have a strong indication that seismic and tectonic processes plays an important role in the variation of global sealevel.

  14. 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.

  15. 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.

  16. Seismicity dynamics and earthquake predictability

    NASA Astrophysics Data System (ADS)

    Sobolev, G. A.

    2011-02-01

    Many factors complicate earthquake sequences, including the heterogeneity and self-similarity of the geological medium, the hierarchical structure of faults and stresses, and small-scale variations in the stresses from different sources. A seismic process is a type of nonlinear dissipative system demonstrating opposing trends towards order and chaos. Transitions from equilibrium to unstable equilibrium and local dynamic instability appear when there is an inflow of energy; reverse transitions appear when energy is dissipating. Several metastable areas of a different scale exist in the seismically active region before an earthquake. Some earthquakes are preceded by precursory phenomena of a different scale in space and time. These include long-term activation, seismic quiescence, foreshocks in the broad and narrow sense, hidden periodical vibrations, effects of the synchronization of seismic activity, and others. Such phenomena indicate that the dynamic system of lithosphere is moving to a new state - catastrophe. A number of examples of medium-term and short-term precursors is shown in this paper. However, no precursors identified to date are clear and unambiguous: the percentage of missed targets and false alarms is high. The weak fluctuations from outer and internal sources play a great role on the eve of an earthquake and the occurrence time of the future event depends on the collective behavior of triggers. The main task is to improve the methods of metastable zone detection and probabilistic forecasting.

  17. 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.

  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. Seismic component fragility data base for IPEEE

    SciTech Connect

    Bandyopadhyay, K.; Hofmayer, C.

    1990-01-01

    Seismic probabilistic risk assessment or a seismic margin study will require a reliable data base of seismic fragility of various equipment classes. Brookhaven National Laboratory (BNL) has selected a group of equipment and generically evaluated the seismic fragility of each equipment class by use of existing test data. This paper briefly discusses the evaluation methodology and the fragility results. The fragility analysis results when used in the Individual Plant Examination for External Events (IPEEE) Program for nuclear power plants are expected to provide insights into seismic vulnerabilities of equipment for earthquakes beyond the design basis. 3 refs., 1 fig., 1 tab.

  20. 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

  1. 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

  2. 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.

  3. 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).

  4. 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

  5. Functional performance requirements for seismic network upgrade

    SciTech Connect

    Lee, R.C.

    1991-08-18

    The SRL seismic network, established in 1976, was developed to monitor site and regional seismic activity that may have any potential to impact the safety or reduce containment capability of existing and planned structures and systems at the SRS, report seismic activity that may be relevant to emergency preparedness, including rapid assessments of earthquake location and magnitude, and estimates of potential on-site and off-site damage to facilities and lifelines for mitigation measures. All of these tasks require SRL seismologists to provide rapid analysis of large amounts of seismic data. The current seismic network upgrade, the subject of this Functional Performance Requirements Document, is necessary to improve system reliability and resolution. The upgrade provides equipment for the analysis of the network seismic data and replacement of old out-dated equipment. The digital network upgrade is configured for field station and laboratory digital processing systems. The upgrade consists of the purchase and installation of seismic sensors,, data telemetry digital upgrades, a dedicated Seismic Data Processing (SDP) system (already in procurement stage), and a Seismic Signal Analysis (SSA) system. The field stations and telephone telemetry upgrades include equipment necessary for three remote station upgrades including seismic amplifiers, voltage controlled oscillators, pulse calibrators, weather protection (including lightning protection) systems, seismometers, seismic amplifiers, and miscellaneous other parts. The central receiving and recording station upgrades will include discriminators, helicopter amplifier, omega timing system, strong motion instruments, wide-band velocity sensors, and other miscellaneous equipment.

  6. 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.

  7. 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

  8. The Kyrgyz Seismic Network (KNET)

    NASA Astrophysics Data System (ADS)

    Bragin, V. D.; Willemann, R. J.; Matix, A. I.; Dudinskih, R. R.; Vernon, F.; Offield, G.

    2007-05-01

    The Kyrgyz Digital Seismic Network (KNET) is a regional continuous telemetric network of very broadband seismic data. KNET was installed in 1991. The telemetry system was upgraded in 1998. The seismograms are transmitted in near real time. KNET is located along part of the boundary between the northern Tien Shan Mountains and the Kazakh platform. Several major tectonic features are spanned by the network including a series of thrust faults in the Tien Shan, the Chu Valley, and the NW-SE trending ridges north of Bishkek. This network is designed to monitor regional seismic activity at the magnitude 3.5+ level as well as to provide high quality data for research projects in regional and global broadband seismology. The Kyrgyz seismic network array consists of 10 stations - 3 of them with more than 3600 m altitude, 2 mountain repeaters, 1 intermediate data base and 2 data centers. One of data centers is a remote source for IRIS data base. KNET is operated by International Research Center - Geodynamic Proving Ground in Bishkek (IGRC) with the participation of Research Station of the Russian Academy of Sciences (RS RAS) and Kyrgyz Institute of Seismology (KIS). The network consists of Streckeisen STS-2 sensors with 24-bit PASSCAL data loggers. All continuous real-time data are accessible through the IRIS DMC in Seattle with over 95% data availability, which compares favorably to the best networks currently operating worldwide. National institutes of seismology in Kyrgyzstan and Kazakhstan, National Nuclear Centre of Kazakhstan, RS RAS, divisions of the ministries on extreme situations and the institutes of the Russian Academy of Sciences use KNET data for estimating seismic hazards and to study deep-seated structure of researched territory. KNET data is used by National Nuclear Centre of Republic of Kazakhstan, which together with LAMONT laboratory (USA) carries out verification researches and monitoring of nuclear detonations in China, India and Pakistan. The uniform

  9. 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.

  10. 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.

  11. Seismicity and seismotectonic study of the Kermit Seismic Zone, Texas

    SciTech Connect

    Keller, G.R.; Rogers, A.M.; Lund, R.J.; Orr, C.D.

    1981-01-01

    This work presents and summarizes all data that were collected during the operation of a 12-station seismograph network in the vicinity of Kermit, Texas, during the period December 1975 to September 1979. The results of this study have several implications relating to the seismic hazard at the Waste Isolation Pilot Plant (WIPP) facility. First, the widespread occurrence of small earthquakes within the seismic network area suggests that additional microearthquake studies in regions closer to the WIPP site are warranted. Second, the apparent relation between hydrocarbon production and earthquake occurrence indicates that the WIPP site probably should not be included in the same seismic source region as the central basin platform because the WIPP site is isolated from the major hydrocarbon producing zones. Third, the maximum magnitude of earthquakes in the active zone may be limited, if these earthquakes are in fact induced by secondary hydrocarbon recovery operations, because the spatial extent of artificial pressure increases is limited, and increase of more than 70 bars have resulted in earthquakes with magnitudes consistently less than 4.0. 14 references.

  12. 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.

  13. Seismic Isolation Working Meeting Gap Analysis Report

    SciTech Connect

    Justin Coleman; Piyush Sabharwall

    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.

  14. 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.

  15. 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.

  16. Mantle dynamics and seismic tomography.

    PubMed

    Tanimoto, T; Lay, T

    2000-11-01

    Three-dimensional imaging of the Earth's interior, called seismic tomography, has achieved breakthrough advances in the last two decades, revealing fundamental geodynamical processes throughout the Earth's mantle and core. Convective circulation of the entire mantle is taking place, with subducted oceanic lithosphere sinking into the lower mantle, overcoming the resistance to penetration provided by the phase boundary near 650-km depth that separates the upper and lower mantle. The boundary layer at the base of the mantle has been revealed to have complex structure, involving local stratification, extensive structural anisotropy, and massive regions of partial melt. The Earth's high Rayleigh number convective regime now is recognized to be much more interesting and complex than suggested by textbook cartoons, and continued advances in seismic tomography, geodynamical modeling, and high-pressure-high-temperature mineral physics will be needed to fully quantify the complex dynamics of our planet's interior. PMID:11035784

  17. 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

  18. Displacement Based Seismic Design Criteria

    SciTech Connect

    Costello, J.F.; Hofmayer, C.; Park, Y.J.

    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.

  19. 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.

  20. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

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

    2002-01-01

    In Section 1 of this first report we will describe the work we are doing to collect and analyze rock physics data for the purpose of modeling seismic attenuation from other measurable quantities such as porosity, water saturation, clay content and net stress. This work and other empirical methods to be presented later, will form the basis for ''Q pseudo-well modeling'' that is a key part of this project. In Section 2 of this report, we will show the fundamentals of a new method to extract Q, dispersion, and attenuation from field seismic data. The method is called Gabor-Morlet time-frequency decomposition. This technique has a number of advantages including greater stability and better time resolution than spectral ratio methods.

  1. 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.

  2. Seismic detection of sonic booms.

    PubMed

    Cates, Joseph E; Sturtevant, Bradford

    2002-01-01

    The pressure signals from a sonic boom will produce a small, but detectable, ground motion. The extensive seismic network in southern California, consisting of over 200 sites covering over 50000 square kilometers, is used to map primary and secondary sonic boom carpets. Data from the network is used to analyze three supersonic overflights in the western United States. The results are compared to ray-tracing computations using a realistic model of the stratified atmospheric at the time of the measurements. The results show sonic boom ground exposure under the real atmosphere is much larger than previously expected or predicted by ray tracing alone. Finally, seismic observations are used to draw some inferences on the origin of a set of "mystery booms" recorded in 1992-1993 in southern California. PMID:11837967

  3. Tube-wave seismic imaging

    DOEpatents

    Korneev, Valeri A.; Bakulin, Andrey

    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.

  4. Lunar seismicity, structure, and tectonics

    NASA Technical Reports Server (NTRS)

    Lammlein, D. R.; Latham, G. V.; Dorman, J.; Nakamura, Y.; Ewing, M.

    1974-01-01

    Natural seismic events have been detected by the long-period seismometers at Apollo stations 16, 14, 15, and 12 at annual rates of 3300, 1700, 800, and 700, respectively, with peak activity at 13- to 14-day intervals. The data are used to describe magnitudes, source characteristics, and periodic features of lunar seismicity. In a present model, the rigid lithosphere overlies an asthenosphere of reduced rigidity in which present-day partial melting is probable. Tidal deformation presumably leads to critical stress concentrations at the base of the lithosphere, where moonquakes are found to occur. The striking tidal periodicities in the pattern of moonquake occurrence and energy release suggest that tidal energy is the dominant source of energy released as moonquakes. Thus, tidal energy is dissipated by moonquakes in the lithosphere and probably by inelastic processes in the asthenosphere.

  5. 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.

  6. 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.

  7. 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 

  8. 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.

  9. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    SciTech Connect

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

    2003-10-01

    In this report we will show the fundamental concepts of two different methods to compute seismic energy absorption. The first methods gives and absolute value of Q and is based on computation with minimum phase operators. The second method gives a relative energy loss compared to a background trend. This method is a rapid, qualitative indicator of anomalous absorption and can be combined with other attributes such as band limited acoustic impedance to indicate areas of likely gas saturation.

  10. Compound hydraulic seismic source vibrator

    SciTech Connect

    Myers, W.J.

    1989-12-05

    This patent describes a compound seismic source vibrator. It comprises: a housing having an upper section and a low frequency radiating section; a low frequency means for vibrating the low frequency radiating section; a high frequency radiating section flexibly connected to the low frequency radiating section; and a high frequency means rigidly secured to the low frequency radiating section for separately vibrating the high frequency radiating section.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Jalisco Regional Seismic Network (RESAJ)

    NASA Astrophysics Data System (ADS)

    Nunez-Cornu, F. J.; Suarez Plascencia, C.; Escudero, C. R.; Gomez, A.

    2011-12-01

    Many societies and their economies endure the disastrous consequences of destructive earthquakes. The Jalisco region is exposing to this natural hazard. Scientific knowledge constitutes the only way to avoid or at least to mitigate the negative effects of such events. Accordingly the study of geological and geophysical causes; structural, kinematics and dynamic characteristics; and destructive effects of such events is indispensable. The main objective of this project is to developed capability to monitor and to analyze the potential destructive earthquakes along the Jalisco region. This network will allows us to study the Rivera plate and the Jalisco block seismicity. Ten earthquakes greater than 7.4 occurred in the last 160 years, including the largest Mexican earthquake (8.2) producing considerable damage in the area. During this project we installed 20 telemetric seismic stations and we plan to deploy up to 30. The stations are component by 24 bit A/D, 6 channels Quanterra Q330-6 DAS, Lennartz Triaxial 1Hz wide band seismometer, a triaxial accelerometer episensor Model FBA ES-T from Kinemetrics and solar power supply. The data is transmitted using freewave Ethernet radios or wireless internet links. All stations will transmit the data in to the central at Puerto Vallarta where all data is processed using Antelope system to localize and make preliminary evaluations of the events in almost real time and stored for future research. This network will produce high quality data enough to evaluate the eight previously identified seismic zones along Jalisco.

  16. Parkfield seismicity: Fluid-driven?

    SciTech Connect

    Johnson, P.A.; McEvilly, T.V.

    1995-07-10

    Characteristics of microearthquake occurrence along the locked-to-creeping transition of the San Andreas fault at Parkfield in central California are reviewed for evidence that fault zone fluids play a critical role in slip dynamics there. Previous studies at Parkfield have defined a low-velocity, anisotropic, attenuating fault zone and a high V{sub P}/V{sub S} ratio in the nucleation zone of the repeating M 6 earthquakes. Most of the ongoing seismicity is organized into a temporally-evolving checkerboard pattern of alternating high and low seismic slip regions divided on the fault zone at 3-6 km spacings. Much of the seismicity is further confined to a few hundred small (20-30 m radius) cells of densely clustered microearthquakes that exhibit periodic recurrence. Space-time development of small (tens to hundreds of meters), transient (minutes to days) earthquake sequences reveals diffusivelike outward spreading along the fault zone. There is some evidence for anomalous source mechanisms in sequence-initiating events, possibly indicative of hydraulic fracturing. The data are consistent with a model in which some microearthquake clusters and confined sequences occur by the cyclic pressurization of fluid within localized patches of the fault zone. The consequent modulation of the effective normal stress leads to fluid-driven slip manifested both as the highly periodic earthquake clusters and as localized earthquake sequences observed at Parkfield. 53 refs., 8 figs., 1 tab.

  17. 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.

  18. Seismic qualification of unanchored equipment

    SciTech Connect

    Moran, T.J.

    1995-12-01

    This paper describes procedures used to design and qualify unanchored equipment to survive Seismic events to the PC = 4 level in a moderate seismic area. The need for flexibility to move experimental equipment together with the requirements for remote handling in a highly-radioactive non-reactor nuclear facility precluded normal equipment anchorage. Instead equipment was designed to remain stable under anticipated DBE floor motions with sufficient margin to achieve the performance goal. The equipment was also designed to accommodate anticipated sliding motions with sufficient. The simplified design criteria used to achieve these goals were based on extensive time-history simulations of sliding, rocking, and overturning of generic equipment models. The entire process was subject to independent peer review and accepted in a Safety Evaluation Report. The process provides a model suitable for adaptation to similar applications and for assessment of the potential for seismic damage of existing, unanchored equipment In particular, the paper describes: (1) Two dimensional sliding studies of deformable equipment subject to 3-D floor excitation as the basis for simplified sliding radius and sliding velocity design criteria. (2) Two dimensional rocking and overturning simulations of rigid equipment used to establish design criteria for minimum base dimensions and equipment rigidity to prevent overturning. (3) Assumed mode rocking analyses of deformable equipment models used to establish uplift magnitudes and subsequent impacts during stable rocking motions. The model used for these dynamic impact studies is reported elsewhere.

  19. 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. 

  20. 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.

  1. 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.

  2. New insights into 3D calving investigations: use of Terrestrial LiDAR for monitoring the Perito Moreno glacier front (Southern Patagonian Ice Fields, Argentina)

    NASA Astrophysics Data System (ADS)

    Abellan, Antonio; Penna, Ivanna; Daicz, Sergio; Carrea, Dario; Derron, Marc-Henri; Guerin, Antoine; Jaboyedoff, Michel

    2015-04-01

    There exists a great incertitude concerning the processes that control and lead to glaciers' fronts disintegration, including the laws and the processes governing ice calving phenomena. The record of surface processes occurring at glacier's front has proven problematic due to the highly dynamic nature of the calving phenomenon, creating a great uncertainty concerning the processes and forms controlling and leading to the occurrence of discrete calving events. For instance, some common observational errors for quantifying the sudden occurrence of the calving phenomena include the insufficient spatial and/or temporal resolution of the conventional photogrammetric techniques and satellites missions. Furthermore, a lack of high quality four dimensional data of failures is currently affecting our ability to straightforward analyse and predict the glaciers' dynamics. In order to overcome these limitations, we used a terrestrial LiDAR sensor (Optech Ilris 3D-LR) for intensively monitoring the changes occurred at one of the most impressive calving glacier fronts: the Perito Moreno glacier, located in the Southern Patagonian Ice Fields (Argentina). Using this system, we were able to capture at an unprecedented level of detail the three-dimensional geometry of the glacier's front during five days (from 10th to 14th of March 2014). Each data collection, which was acquired at a mean interval of 20 minutes each, consisted in the automatic acquisition of several million points at a mean density between 100-200 points per square meter. The maximum attainable range for the utilized wavelength of the Ilris-LR system (1064 nm) was around 500 meters over massive ice (showing no-significant loss of information), being this distance considerably reduced on crystalline or wet ice short after the occurrence of calving events. By comparing successive three-dimensional datasets, we have investigated not only the magnitude and frequency of several ice failures at the glacier's terminus, but

  3. Miocene to Late Quaternary Patagonian basalts (46 47°S): Geochronometric and geochemical evidence for slab tearing due to active spreading ridge subduction

    NASA Astrophysics Data System (ADS)

    Guivel, Christèle; Morata, Diego; Pelleter, Ewan; Espinoza, Felipe; Maury, René C.; Lagabrielle, Yves; Polvé, Mireille; Bellon, Hervé; Cotten, Joseph; Benoit, Mathieu; Suárez, Manuel; de la Cruz, Rita

    2006-01-01

    + 5.4). These features are consistent with their derivation from an enriched mantle source contaminated by ca. 10% rutile-bearing restite of altered oceanic crust. The petrogenesis of the studied Mio-Pliocene basalts from MLBA and MCC is consistent with contributions of the subslab asthenosphere, the South American subcontinental lithospheric mantle and the subducted Pacific oceanic crust to their sources. However, their chronology of emplacement is not consistent with an ascent through an asthenospheric window opened as a consequence of the subduction of segment SCR-1, which entered the trench at 6 Ma. Indeed, magmatic activity was already important between 12 and 8 Ma in MLBA and MCC as well as in southernmost plateaus, i.e., 6 Ma before the subduction of the SCR-1 segment. We propose a geodynamic model in which OIB and intermediate magmas derived from deep subslab asthenospheric mantle did uprise through a tear-in-the-slab, which formed when the southernmost segments of the SCR collided with the Chile Trench around 15 Ma. During their ascent, they interacted with the Patagonian supraslab mantle and, locally, with slivers of subducted Pacific oceanic crust that contributed to the geochemical signature of the intermediate basalts.

  4. Environmental and biological factors controlling the spring phytoplankton bloom at the Patagonian shelf-break front - Degraded fucoxanthin pigments and the importance of microzooplankton grazing

    NASA Astrophysics Data System (ADS)

    Carreto, José I.; Montoya, Nora G.; Carignan, Mario O.; Akselman, Rut; Acha, E. Marcelo; Derisio, Carla

    2016-08-01

    The aim of this study was to investigate the biotic and abiotic factors controlling the spring phytoplankton blooms at the Patagonian shelf-break front (PSBF). Using a CHEMTAX analysis of HPLC pigment data and other methods, the biomass and spatial variability of plankton communities were studied in four sections (39-48°S) across the PSBF during October 2005. Environmental factors and the biomass and composition of plankton communities exhibited a marked spatial heterogeneity. The latitudinal and cross-shelf progression in the timing of the spring bloom initiation and the nutritive properties of the water masses (Subantarctic Shelf Waters and Malvinas Current Waters) seemed to be the key factors. Three plankton regions were distinguished: (a) Outer shelf (OS), (b) Shelf-break front (SBF) and (c) Malvinas Current (MC). At the highly stratified OS region, the post-bloom community showed low-biomasshigh-phytoplankton diversity formed mainly by small cells (haptophytes 30-62%, diatoms 17-49%, chlorophytes 0-34%, and prasinophytes 0-21% of total Chl a). High amounts of degraded fucoxanthin were found associated with the heterotrophic dinoflagellate, Protoperidinium capurroi. Grazing by this microheterotroph on the diatom population seemed to be the most important factor for the spring bloom decay at the OS. A remarkable quasi monospecific bloom (∼90%) of a nanodiatom (Thalassiosira bioculata var. raripora) associated with high Chl a (up to 20 mg m-3) occurred along (∼1000 km) the SBF and in the most northern extension of the MC. In the southern region, the bloom was developed under absent or incipient density stratification, increasing solar irradiance, high nitrate and phosphate availability, and low numbers of phytoplankton grazers. The average mixedlayer PAR irradiance (<2.0 mol quanta PAR m-2 d-1) and Si:N ratios (<0.2) were low, suggesting a diatom population limited by light and under progressive silicate limitation. The more stratified northern region of the

  5. 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).

  6. 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.

  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. 3-D seismic imaging of complex geologies

    SciTech Connect

    Womble, D.E.; Dosanjh, S.S.; VanDyke, J.P.; Oldfield, R.A.; Greenberg, D.S.

    1995-02-01

    We present three codes for the Intel Paragon that address the problem of three-dimensional seismic imaging of complex geologies. The first code models acoustic wave propagation and can be used to generate data sets to calibrate and validate seismic imaging codes. This code reported the fastest timings for acoustic wave propagation codes at a recent SEG (Society of Exploration Geophysicists) meeting. The second code implements a Kirchhoff method for pre-stack depth migration. Development of this code is almost complete, and preliminary results are presented. The third code implements a wave equation approach to seismic migration and is a Paragon implementation of a code from the ARCO Seismic Benchmark Suite.

  10. Code System for Seismic Probabilistic Risk Assessment.

    Energy Science and Technology Software Center (ESTSC)

    2001-03-27

    Version 00 SEISIM1 calculates the probabilities of seismically induced failures for components and systems and propagates these calculations to determine the probability of accident sequences and the resulting total risk, which is quantified as an expected value of radiation release and exposure from a given nuclear power plant. SEISIM1 was developed as a fundamental tool for the systems analysis portion of the NRC's Seismic Safety Margins Research Program (SSMRP). The SSMRP provides a complete, self-containedmore » methodology to assess and quantify the risk to nuclear power plants from seismic events and seismically induced failures.« less

  11. Estimating primaries from passive seismic data

    NASA Astrophysics Data System (ADS)

    Cheng, Hao; Wang, De-Li; Feng, Fei; Zhu, Heng

    2015-12-01

    Passive seismic sources can generally be divided into transient sources and noise sources. Noise sources are particularly the continuous, random small bursts, like background noise. The virtual-shot gathers obtained by the traditional cross-correlation algorithm from passive seismic data not only contain primaries, but also include surface-related multiples. Through estimating primaries by sparse inversion, we can directly obtain primaries from passive seismic data activated by transient sources, which are free of surface-related multiples. The problem of estimating primaries from passive seismic data activated by noise sources has not been discussed to date. First, by introducing the optimisation problem via the L1-norm constraint, this paper makes the traditional method of estimating primaries by sparse inversion from passive seismic data activated by transient sources improved, which overcomes the time-window problem. During the sparse inversion, the sparsifying transform, S = C2⊗W, is introduced. In the sparsifying-transform domain, the transformed data is more sparse, so the solution becomes more accurate. Second, this paper proposes estimating primaries from passive seismic data activated by noise sources. In the case of the sparse assumption not holding, we use the least-squares method based on the principle of minimum energy to estimate primaries from passive seismic data using the noise sources. Finally, we compare the primaries estimated from passive seismic data using transient sources and noise sources and analyse the characteristics of the estimated primaries obtained from two passive seismic data.

  12. 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 seismic hazard assessment and the present normative seismic hazard map needed a careful recalculation. The methodology for the probabilistic assessment of seismic hazard used here includes the following steps: produce comprehensive catalogue of historical earthquakes (up to 1900) and the period of instrumental observations with uniform scale of magnitudes; produce models of seismic source zones (SSZ) and their parameterization; develop appropriate ground motion prediction equation (GMPE) models; develop seismic hazard curves for spectral amplitudes at each period and maps in digital format. Firstly, the new seismic catalog of Georgia was created, with 1700 eqs from ancient times on 2012, Mw³4.0. Secondly, were allocated seismic source zones (SSZ). The identification of area SSZ was obtained on the bases of structural geology, parameters of seismicity and seismotectonics. In constructing the SSZ, the slope of the appropriate active fault plane, the width of the dynamic influence of the fault, power of seismoactive layer are taken into account. Finally each SSZ was defined with the parameters: the geometry, the percentage of focal mechanism, predominant azimuth and dip angle values, activity rates, maximum magnitude, hypocenter depth distribution, lower and upper seismogenic depth values. Thirdly, seismic hazard maps were calculated based on modern approach of selecting and ranking global and regional ground motion prediction equation for region. Finally, probabilistic seismic hazard assessment in terms of ground acceleration were calculated for the territory of Georgia. On the basis of obtained area seismic sources probabilistic seismic hazard maps were calculated showing peak ground acceleration (PGA) and spectral accelerations (SA) at

  13. 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.

  14. Infrasound Generation from the HH Seismic Hammer.

    SciTech Connect

    Jones, Kyle Richard

    2014-10-01

    The HH Seismic hammer is a large, "weight-drop" source for active source seismic experiments. This system provides a repetitive source that can be stacked for subsurface imaging and exploration studies. Although the seismic hammer was designed for seismological studies it was surmised that it might produce energy in the infrasonic frequency range due to the ground motion generated by the 13 metric ton drop mass. This study demonstrates that the seismic hammer generates a consistent acoustic source that could be used for in-situ sensor characterization, array evaluation and surface-air coupling studies for source characterization.

  15. Seismic monitoring of torrential and fluvial processes

    NASA Astrophysics Data System (ADS)

    Burtin, Arnaud; Hovius, Niels; Turowski, Jens M.

    2016-04-01

    In seismology, the signal is usually analysed for earthquake data, but earthquakes represent less than 1 % of continuous recording. The remaining data are considered as seismic noise and were for a long time ignored. Over the past decades, the analysis of seismic noise has constantly increased in popularity, and this has led to the development of new approaches and applications in geophysics. The study of continuous seismic records is now open to other disciplines, like geomorphology. The motion of mass at the Earth's surface generates seismic waves that are recorded by nearby seismometers and can be used to monitor mass transfer throughout the landscape. Surface processes vary in nature, mechanism, magnitude, space and time, and this variability can be observed in the seismic signals. This contribution gives an overview of the development and current opportunities for the seismic monitoring of geomorphic processes. We first describe the common principles of seismic signal monitoring and introduce time-frequency analysis for the purpose of identification and differentiation of surface processes. Second, we present techniques to detect, locate and quantify geomorphic events. Third, we review the diverse layout of seismic arrays and highlight their advantages and limitations for specific processes, like slope or channel activity. Finally, we illustrate all these characteristics with the analysis of seismic data acquired in a small debris-flow catchment where geomorphic events show interactions and feedbacks. Further developments must aim to fully understand the richness of the continuous seismic signals, to better quantify the geomorphic activity and to improve the performance of warning systems. Seismic monitoring may ultimately allow the continuous survey of erosion and transfer of sediments in the landscape on the scales of external forcing.

  16. Glacial-Interglacial period in Lago Sarmiento (Chilean Patagonia) using high resolution seismic

    NASA Astrophysics Data System (ADS)

    Vizcaino Marti, A.; Dunbar, R. B.; Mucciarone, D. A.; LeRoy, S.; Stadnyk, A. D.

    2011-12-01

    Southern South America is the only large continental landmass situated in the core of the southern westerly wind field. Precipitation in the region is generally produced by frontal systems associated with surface depressions. Stronger westerlies at interannual and longer time scales promote extratropical storms, leading to an increase in precipitation. Orographic effects amplify this process, and the resulting precipitation is an important source of moisture along the Pacific margin of the Andes. Eastward to the Patagonian Andes there is a drying effect, and stronger westerlies produce a decrease in precipitation. Lago Sarmiento is a deep 25 km long and 6 km wide, E-W oriented closed-basin lake located at 51°S 72.5°W and about 70 meters above sea level. The lake is supplied by small ephemeral streams and does not directly receive glacial meltwater. Water level and composition depends on the evaporation-rainfall ratio. The abundant carbonate in the lake sediments precipitate in equilibrium with lake waters. High resolution seismic stratigraphic analyses, obtained using a Chirp 3.5 kHz in Lago Sarmiento, are the basis for an interpretation of the sedimentological changes in the lake. Different acoustic facies show an evolution from glacial sediment facies when ice occupied the drainage basin during the Last Glacial Maximum (LGM). From the Glacial/Glacio-lacustrine acoustic facies we observe an upward trend to a high laminated facies indicating an ice retreat and a domination of lacustrine processes. All shallow water areas of the lake support modern Rivularia (cyanobacteria) bioherms. Individual structures are as much as 5 m in height and 6 m in diameter. Emergent "fossil" bioherms occur along all shorelines and define previous lake highstands. With the exception of autochthonous carbonate deposits along the shoreline of Sarmiento, there are no significant carbonate lithologies present within the drainage basin. In addition to the acoustic facies, a number of

  17. Seismic-wave attenuation associated with crustal faults in the New Madrid seismic zone

    USGS Publications Warehouse

    Hamilton, R.M.; Mooney, W.D.

    1990-01-01

    The attenuation of upper crustal seismic waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid seismic zone in the central Mississippi Valley. The waves that have the strongest attenuation pass through the seismic trend along the axis of the Reelfoot rift in the area of the Blytheville arch. Defocusing of the waves in a low-velocity zone and/ or seismic scattering and absorption could cause the attenuation; these effects are most likely associated with the highly deformed rocks along the arch. Consequently, strong seismic-wave attenuation may be a useful criterion for identifying seismogenic fault zones.

  18. The Italian National Seismic Network

    NASA Astrophysics Data System (ADS)

    Michelini, Alberto

    2016-04-01

    The Italian National Seismic Network is composed by about 400 stations, mainly broadband, installed in the Country and in the surrounding regions. About 110 stations feature also collocated strong motion instruments. The Centro Nazionale Terremoti, (National Earthquake Center), CNT, has installed and operates most of these stations, although a considerable number of stations contributing to the INGV surveillance has been installed and is maintained by other INGV sections (Napoli, Catania, Bologna, Milano) or even other Italian or European Institutions. The important technological upgrades carried out in the last years has allowed for significant improvements of the seismic monitoring of Italy and of the Euro-Mediterranean Countries. The adopted data transmission systems include satellite, wireless connections and wired lines. The Seedlink protocol has been adopted for data transmission. INGV is a primary node of EIDA (European Integrated Data Archive) for archiving and distributing, continuous, quality checked data. The data acquisition system was designed to accomplish, in near-real-time, automatic earthquake detection and hypocenter and magnitude determination (moment tensors, shake maps, etc.). Database archiving of all parametric results are closely linked to the existing procedures of the INGV seismic monitoring environment. Overall, the Italian earthquake surveillance service provides, in quasi real-time, hypocenter parameters which are then revised routinely by the analysts of the Bollettino Sismico Nazionale. The results are published on the web page http://cnt.rm.ingv.it/ and are publicly available to both the scientific community and the the general public. This presentation will describe the various activities and resulting products of the Centro Nazionale Terremoti. spanning from data acquisition to archiving, distribution and specialised products.

  19. Seismic monitoring at The Geysers

    SciTech Connect

    Majer, E.L.; Romero, A.; Vasco, D.; Kirkpatrick, A.; Peterson, J.E.; Zucca, J.J.; Hutchings, L.J.; Kasameyer, P.W.

    1993-04-01

    During the last several years Lawrence Berkeley Laboratory (LBL) and Lawrence Livermore National Laboratory (LLNL) have been working with industry partners at The Geysers geothermal field to evaluate and develop methods for applying the results of microearthquake (MEQ) monitoring. It is a well know fact that seismicity at The Geysers is a common occurrence, however, there have been many studies and papers written on the origin and significance of the seismicity. The attitude toward MEQ data ranges from being nothing more than an curious artifact of the production activities, to being a critical tool in evaluating the reservoir performance. The purpose of the work undertaken b y LBL and LLNL is to evaluate the utility, as well as the methods and procedures used in of MEQ monitoring, recommend the most cost effective implementation of the methods, and if possible link physical processes and parameters to the generation of MEQ activity. To address the objectives above the MEQ work can be categorized into two types of studies. The first type is the direct analysis of the spatial and temporal distribution of MEQ activity and studying the nature of the source function relative to the physical or chemical processes causing the seismicity. The second broad area of study is imaging the reservoir/geothermal areas with the energy created by the MEQ activity and inferring the physical and/or chemical properties within the zone of imaging. The two types of studies have obvious overlap, and for a complete evaluation and development require high quality data from arrays of multicomponent stations. Much of the effort to date at The Geysers by both DOE and the producers has concentrated establishing a high quality data base. It is only within the last several years that this data base is being fully evaluated for the proper and cost effective use of MEQ activity. Presented here are the results to date of DOE`s effort in the acquisition and analysis of the MEQ data.

  20. Apollo 14 active seismic experiment.

    PubMed

    Watkins, J S; Kovach, R L

    1972-03-17

    Explosion seismic refraction data indicate that the lunar near-surface rocks at the Apollo 14 site consist of a regolith 8.5 meters thick and characterized by a compressional wave velocity of 104 meters per second. The regolith is underlain by a layer with a compressional wave velocity of 299 meters per second. The thickness of this layer, which we interpret to be the Fra Mauro Formation, is between 16 and 76 meters. The layer immediately beneath this has a velocity greater than 370 meters per second. We found no evidence of permafrost. PMID:17794200

  1. Seismically imaging the Afar plume

    NASA Astrophysics Data System (ADS)

    Hammond, J. O.; Kendall, J. M.; Bastow, I. D.; Stuart, G. W.; Keir, D.; Ayele, A.; Ogubazghi, G.; Ebinger, C. J.; Belachew, M.

    2011-12-01

    Plume related flood basalt volcanism in Ethiopia has long been cited to have instigated continental breakup in northeast Africa. However, to date seismic images of the mantle beneath the region have not produced conclusive evidence of a plume-like structure. As a result the nature and even existence of a plume in the region and its role in rift initiation and continental rupture are debated. Previous seismic studies using regional deployments of sensors in East-Africa show that low seismic velocities underlie northeast Africa, but their resolution is limited to the top 200-300km of the Earth. Thus, the connection between the low velocities in the uppermost mantle and those imaged in global studies in the lower mantle is unclear. We have combined new data from Afar, Ethiopia with 6 other regional experiments and global network stations across Ethiopia, Eritrea, Djibouti and Yemen, to produce high-resolution models of upper mantle P- and S- wave velocities to the base of the transition zone. Relative travel time tomographic inversions show that the top 100km is dominated by focussed low velocity zones, likely associated with melt in the lithosphere/uppermost asthenosphere. Below these depths a broad SW-NE oriented sheet like upwelling extends down to the top of the transition zone. Within the transition zone two focussed sharp-sided low velocity regions exist: one beneath the Western Ethiopian plateau outside the rift valley, and the other beneath the Afar depression. The nature of the transition zone anomalies suggests that small upwellings may rise from a broader low velocity plume-like feature in the lower mantle. This interpretation is supported by numerical and analogue experiments that suggest the 660km phase change and viscosity jump may impede flow from the lower to upper mantle creating a thermal boundary layer at the base of the transition zone. This allows smaller, secondary upwellings to initiate and rise to the surface. Our images of secondary upwellings

  2. Newberry EGS Seismic Velocity Model

    DOE Data Explorer

    Templeton, Dennise

    2013-10-01

    We use ambient noise correlation (ANC) to create a detailed image of the subsurface seismic velocity at the Newberry EGS site down to 5 km. We collected continuous data for the 22 stations in the Newberry network, together with 12 additional stations from the nearby CC, UO and UW networks. The data were instrument corrected, whitened and converted to single bit traces before cross correlation according to the methodology in Benson (2007). There are 231 unique paths connecting the 22 stations of the Newberry network. The additional networks extended that to 402 unique paths crossing beneath the Newberry site.

  3. 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 some new Q related seismic attributes on the Burlington-Seitel data set. One example will be called Energy Absorption Attribute (EAA) and is based on a spectral analysis. The EAA algorithm is designed to detect a sudden increase in the rate of exponential decay in the relatively higher frequency portion of the spectrum. In addition we will show results from a hybrid attribute that combines attenuation with relative acoustic impedance to give a better indication of commercial gas saturation.

  4. The GEOSCOPE broadband seismic observatory

    NASA Astrophysics Data System (ADS)

    Douet, Vincent; Vallée, Martin; Zigone, Dimitri; Bonaimé, Sébastien; Stutzmann, Eléonore; Maggi, Alessia; Pardo, Constanza; Bernard, Armelle; Leroy, Nicolas; Pesqueira, Frédéric; Lévêque, Jean-Jacques; Thoré, Jean-Yves; Bes de Berc, Maxime; Sayadi, Jihane

    2016-04-01

    The GEOSCOPE observatory has provided continuous broadband data to the scientific community for the past 34 years. The 31 operational GEOSCOPE stations are installed in 17 countries, across all continents and on islands throughout the oceans. They are equipped with three component very broadband seismometers (STS1, T240 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. All stations send data in real time to the IPGP data center, which transmits them automatically to other data centers (FDSN/IRIS-DMC and RESIF) and tsunami warning centers. In 2016, three stations are expected to be installed or re-installed: in Western China (WUS station), in Saint Pierre and Miquelon Island (off the East coast of Canada) and in Walis and Futuna (SouthWest Pacific Ocean). The waveform data are technically validated by IPGP (25 stations) or EOST (6 stations) in order to check their continuity and integrity. Scientific data validation is also performed by analyzing seismic noise level of the continuous data and by comparing real and synthetic earthquake waveforms (body waves). After these validations, data are archived by the IPGP data center in Paris. They are made available to the international scientific community through different interfaces (see details on http://geoscope.ipgp.fr). Data are duplicated at the FDSN/IRIS-DMC data center and a similar duplication at the French national data center RESIF will be operational in 2016. The GEOSCOPE broadband seismic observatory also provides near-real time information on global moderate-to-large seismicity (above magnitude 5.5-6) through the automated application of the SCARDEC method (Vallée et al., 2011). By using global data from the FDSN - in particular from GEOSCOPE and IRIS/USGS stations -, earthquake source parameters (depth, moment magnitude, focal mechanism, source time function) are determined about 45

  5. Evaluation of seismic energy evolution

    NASA Astrophysics Data System (ADS)

    -Emilian Toader, Victorin; Marmureanu, Alexandru

    2013-04-01

    The program analyzes seismicity on a defined area with the use of bulletins (event information) provided by ANTELOPE software. These include earthquake localization (moment, latitude, longitude, magnitude, depth, P and S for each station and other parameters). The evolution of the calculated energy from the Richter magnitude is characterized by steps which can be linearly interpolated. In this way tendencies of energy accumulation / release through tectonic movement can be estimated. Also, it will be calculated and displayed the 'b' coefficient from the Gutenberg - Richter law. The results will be saved as a HTML list which allows global and individual visualization of the seismic forecasts accompanied by the epicenter position on the map. The ANTELOPE users are the first beneficiaries but the program could be modified for other formats of data which include the same information related to the earthquakes localization. The software allows to select the analysis area in which the epicenters are located. In this respect, we are using the free Google Static Maps service (in this case an internet connection is necessary) as well as there is an offline option. In a configuration file the coordinates of the epicenter area has to be defined, the zoom level and the map type if Google Maps is used. The user may redefine the investigation area in online mode. Furthermore, the program allows the selection of the time interval during which the analysis is performed, the configuration of the magnitude and depth intervals, the folders in which the ANTELOPE bulletins are located and where the results will be saved in HTML format. In a separate panel the time intervals between 2 seismic events, the resulted energy from the magnitude conversion (Ml or Md) and magnitudes - depths evolution at which the earthquakes took place can be visualized. During the analysis of the seismic bulletins generated by ANTELOPE, the epicenters are displayed dynamically in the original selected area

  6. Buildings As Secondary Seismic Sources

    NASA Astrophysics Data System (ADS)

    Semblat, J.-F.; Kham, M.; Guéguen, P.; Bard, P.-Y.

    At the scale of a city, surface structures like buildings can modify the seismic free- field and behave as secondary seismic sources. At a local scale, some experimental evidences of the site-structure interaction were previously given (Guéguen, 2000). Thanks to the boundary element method, the global problem of site-city interaction is herein investigated in two dimensions at the scale of an alluvial deposit and an entire city considering a whole building network. An alluvial deposit located in the center of Nice (France) was firstly considered for the analysis of free-field amplification (Semblat, 2000). The amplification factor was estimated by the boundary element method and compared with experimental results (SSR, HVSR). Starting from these free-field simulations, several site-city models were considered which describe both superficial soil layers and surface structures. We in- vestigate herein the influence of both building type and building density on the modi- fication of free-field amplification. To compare free-field amplification and amplification in urban configurations, sur- face amplification is compared in both cases for a specific uniform building type and various building densities at differents frequencies. Depending on these various pa- rameters, the free-field amplification level could be increased by 20 to 50%. Other urban configurations are considered with various building types in uniform and inho- mogeneous arrangements. For the specific site considered, the various site-city BEM models show that site-city interaction can lead to a strong increase of the free-field am- plification factor. Around the fundamental frequency of a specific building type, for a homogeneous urban configuration, particular resonance effects are observed. These results are in good agreement with previous experimental and local scale numerical results (Guéguen, 2000) and show that the coincidence of the respective eigenfre- quencies of both alluvial deposit and

  7. Apollo 14 active seismic experiment.

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    Explosion seismic refraction data indicate that the lunar near-surface rocks at the Apollo 14 site consist of a regolith 8.5 meters thick and characterized by a compressional wave velocity of 104 meters per second. The regolith is underlain by a layer with a compressional wave velocity of 299 meters per second. The thickness of this layer, which we interpret to be the Fra Mauro Formation, is between 16 and 76 meters. The layer immediately beneath this has a velocity greater than 370 meters per second. We found no evidence of permafrost.

  8. Probabilistic Simulation of Territorial Seismic Scenarios

    SciTech Connect

    Baratta, Alessandro; Corbi, Ileana

    2008-07-08

    The paper is focused on a stochastic process for the prevision of seismic scenarios on the territory and developed by means of some basic assumptions in the procedure and by elaborating the fundamental parameters recorded during some ground motions occurred in a seismic area.

  9. Fennoscandian lithosphere - electromagnetic and seismic constraints

    NASA Astrophysics Data System (ADS)

    Korja, T.; Kozlovskaya, E.; Smirnov, M.

    2009-04-01

    Knowledge of the present-day structure of the Earth's mantle is essential to our understanding of plate tectonics as well as Earth's thermomechanical evolution over long periods of geological time. Several factors including temperature, chemical composition, presence of partial melt or water influence seismic velocities and electrical conductivity in the upper mantle. Similarly, anisotropy may have a profound effect on seismic and magnetotelluric observations. During last ten years, several large scale multinational and national seismic and magnetotelluric experiments have been carried out in Fennnoscandia including e.g. the SVEKALAPKO seismic tomography experiment, Swedish National Seismic Network (SNSN) array monitoring, BEAR and EMMA magnetotelluric array studies and magnetotelluric profiling such as TOR and Jamtland. Altogether these studies cover most of Fennoscandia and make it possible to correlate two different data sets and to study lithospheric structures in Fennoscandia. In particular, we will compare the thickness of the lithosphere obtained from seismic anisotropy studies and from magnetotelluric studies. We will also correlate spatially sparse indications on seismic reflectors and electrically conducting layers in the mantle lithosphere. Finally, we aim to compare directly absolute values of seismic velocity and electrical conductivity.

  10. Seismic analysis of the LSST telescope

    NASA Astrophysics Data System (ADS)

    Neill, Douglas R.

    2012-09-01

    The Large Synoptic Survey Telescope (LSST) will be located on the seismically active Chilean mountain of Cerro Pachón. The accelerations resulting from seismic events produce the most demanding load cases the telescope and its components must withstand. Seismic ground accelerations were applied to a comprehensive finite element analysis (FEA) model which included the telescope, its pier and the mountain top. Response accelerations for specific critical components (camera and secondary mirror assembly) on the telescope were determined by applying seismic accelerations in the form of Power Spectral Densities (PSD) to the FEA model. The PSDs were chosen based on the components design lives. Survival level accelerations were determined utilizing PSDs for seismic events with return periods 10 times the telescope's design life which is equivalent to a 10% chance of occurring over the lifetime. Since the telescope has a design life of 30 years it was analyzed for a return period of 300 years. Operational level seismic accelerations were determined using return periods of 5 times the lifetimes. Since the seismic accelerations provided by the Chilean design codes were provided in the form of Peak Spectral Accelerations (PSA), a method to convert between the two forms was developed. The accelerations are also affected by damping level. The LSST incorporates added damping to meets its rapid slew and settle requirements. This added damping also reduces the components' seismic accelerations. The analysis was repeated for the telescope horizon and zenith pointing. Closed form solutions were utilized to verify the results.

  11. Seismic Monitoring for the United Arab Emirates

    SciTech Connect

    Rodgers, A; Nakanishi, K

    2005-04-11

    There is potential for earthquakes in the United Arab Emirates and in the Zagros mountains to cause structural damage and pose a threat to safety of people. Damaging effects from earthquakes can be mitigated by knowledge of the location and size of earthquakes, effects on construction, and monitoring these effects over time. Although a general idea of seismicity in the UAE may be determined with data from global seismic networks, these global networks do not have the sensitivity to record smaller seismic events and do not have the necessary accuracy to locate the events. A National Seismic Monitoring Observatory is needed for the UAE that consists of a modern seismic network and a multidisciplinary staff that can analyze and interpret the data from the network. A seismic network is essential to locate earthquakes, determine event magnitudes, identify active faults and measure ground motions from earthquakes. Such a network can provide the data necessary for a reliable seismic hazard assessment in the UAE. The National Seismic Monitoring Observatory would ideally be situated at a university that would provide access to the wide range of disciplines needed in operating the network and providing expertise in analysis and interpretation.

  12. Site effects on seismic behavior of pipelines

    SciTech Connect

    Liang, J.W.; Sun, S.

    1996-12-01

    Post-earthquake investigations and earthquake observations have shown that the site conditions have spectacular effects on seismic behavior of pipelines. In this paper, an updated and detailed review of the site effects on seismic behavior of pipelines is presented, and research needs are pointed out. 90 refs.

  13. Onshore seismic amplifications due to bathymetric features

    NASA Astrophysics Data System (ADS)

    Rodríguez-Castellanos, A.; Carbajal-Romero, M.; Flores-Guzmán, N.; Olivera-Villaseñor, E.; Kryvko, A.

    2016-08-01

    We perform numerical calculations for onshore seismic amplifications, taking into consideration the effect of bathymetric features on the propagation of seismic movements. To this end, the boundary element method is applied. Boundary elements are employed to irradiate waves and, consequently, force densities can be obtained for each boundary element. From this assumption, Huygens’ principle is applied, and since the diffracted waves are built at the boundary from which they are radiated, this idea is equivalent to Somigliana’s representation theorem. The application of boundary conditions leads to a linear system being obtained (Fredholm integral equations). Several numerical models are analyzed, with the first one being used to verify the proposed formulation, and the others being used to estimate onshore seismic amplifications due to the presence of bathymetric features. The results obtained show that compressional waves (P-waves) generate onshore seismic amplifications that can vary from 1.2 to 5.2 times the amplitude of the incident wave. On the other hand, the shear waves (S-waves) can cause seismic amplifications of up to 4.0 times the incident wave. Furthermore, an important result is that in most cases the highest seismic amplifications from an offshore earthquake are located on the shoreline and not offshore, despite the seafloor configuration. Moreover, the influence of the incident angle of seismic waves on the seismic amplifications is highlighted.

  14. 3D Elastic Seismic Wave Propagation Code

    Energy Science and Technology Software Center (ESTSC)

    1998-09-23

    E3D is capable of simulating seismic wave propagation in a 3D heterogeneous earth. Seismic waves are initiated by earthquake, explosive, and/or other sources. These waves propagate through a 3D geologic model, and are simulated as synthetic seismograms or other graphical output.

  15. A description of seismic amplitude techniques

    NASA Astrophysics Data System (ADS)

    Shadlow, James

    2014-02-01

    The acquisition of seismic data is a non-invasive technique used for determining the sub surface geology. Changes in lithology and fluid fill affect the seismic wavelet. Analysing seismic data for direct hydrocarbon indicators (DHIs), such as full stack amplitude anomalies, or amplitude variation with offset (AVO), can help a seismic interpreter relate the geophysical response to real geology and, more importantly, to distinguish the presence of hydrocarbons. Inversion is another commonly used technique that attempts to tie the seismic data back to the geology. Much has been written about these techniques, and attempting to gain an understanding on the theory and application of them by reading through various journals can be quite daunting. The purpose of this paper is to briefly outline DHI analysis, including full stack amplitude anomalies, AVO and inversion and show the relationship between all three. The equations presented have been included for completeness, but the reader can pass over the mathematical detail.

  16. Seismicity in Azerbaijan and Adjacent Caspian Sea

    SciTech Connect

    Panahi, Behrouz M.

    2006-03-23

    So far no general view on the geodynamic evolution of the Black Sea to the Caspian Sea region is elaborated. This is associated with the geological and structural complexities of the region revealed by geophysical, geochemical, petrologic, structural, and other studies. A clash of opinions on geodynamic conditions of the Caucasus region, sometimes mutually exclusive, can be explained by a simplified interpretation of the seismic data. In this paper I analyze available data on earthquake occurrences in Azerbaijan and the adjacent Caspian Sea region. The results of the analysis of macroseismic and instrumental data, seismic regime, and earthquake reoccurrence indicate that a level of seismicity in the region is moderate, and seismic event are concentrated in the shallow part of the lithosphere. Seismicity is mostly intra-plate, and spatial distribution of earthquake epicenters does not correlate with the plate boundaries.

  17. Seismic safety of high concrete dams

    NASA Astrophysics Data System (ADS)

    Chen, Houqun

    2014-08-01

    China is a country of high seismicity with many hydropower resources. Recently, a series of high arch dams have either been completed or are being constructed in seismic regions, of which most are concrete dams. The evaluation of seismic safety often becomes a critical problem in dam design. In this paper, a brief introduction to major progress in the research on seismic aspects of large concrete dams, conducted mainly at the Institute of Water Resources and Hydropower Research (IWHR) during the past 60 years, is presented. The dam site-specific ground motion input, improved response analysis, dynamic model test verification, field experiment investigations, dynamic behavior of dam concrete, and seismic monitoring and observation are described. Methods to prevent collapse of high concrete dams under maximum credible earthquakes are discussed.

  18. Seismic analysis of nuclear power plant structures

    NASA Technical Reports Server (NTRS)

    Go, J. C.

    1973-01-01

    Primary structures for nuclear power plants are designed to resist expected earthquakes of the site. Two intensities are referred to as Operating Basis Earthquake and Design Basis Earthquake. These structures are required to accommodate these seismic loadings without loss of their functional integrity. Thus, no plastic yield is allowed. The application of NASTRAN in analyzing some of these seismic induced structural dynamic problems is described. NASTRAN, with some modifications, can be used to analyze most structures that are subjected to seismic loads. A brief review of the formulation of seismic-induced structural dynamics is also presented. Two typical structural problems were selected to illustrate the application of the various methods of seismic structural analysis by the NASTRAN system.

  19. Seismic of the territory Toktogul reservoir, Kyrgyzstan

    SciTech Connect

    Kamchybekov, Murataly; Yegemberdiyeva, Kuliya

    2008-07-08

    In connection with that this seismic in the territory of Naryn cascade maybe has its peculiarity in cludding in the territory Toktogul reservoir before of the building of the Toktogul dam, during of the building and after accordingly was decided to consider the seismic in this space of times. The arm of the present paper is estimation seismic of the territory Toktogul reservoir for different times: before of the building of the Toktogul dam (1960-1973), during its filling (1974-1980) and since start it's of the uninterruptedly exploitation to present time (1981-2006). The territory in that located the cascade of Naryn River is considered that seismic active in the Central part of the Tien Shan. The tectonic motions are become here intensity. The presence of the large faults is complicating significantly the seismic situation of the study region.

  20. Broadband seismology and small regional seismic networks

    USGS Publications Warehouse

    Herrmann, Robert B.

    1995-01-01

    In the winter of 1811-12, three of the largest historic earthquakes in the United States occurred near New Madrid, Missouri. Seismicity continues to the present day throughout a tightly clustered pattern of epicenters centered on the bootheel of Missouri, including parts of northeastern Arkansas, northwestern Tennessee, western Kentucky, and southern Illinois. In 1990, the New Madrid seismic zone/Central United States became the first seismically active region east of the Rocky Mountains to be designated a priority research area within the National Earthquake Hazards Reduction Program (NEHRP). This Professional Paper is a collection of papers, some published separately, presenting results of the newly intensified research program in this area. Major components of this research program include tectonic framework studies, seismicity and deformation monitoring and modeling, improved seismic hazard and risk assessments, and cooperative hazard mitigation studies.

  1. Hierarchical model for distributed seismicity

    SciTech Connect

    Tejedor, Alejandro; Gomez, Javier B.; Pacheco, Amalio F.

    2010-07-15

    A cellular automata model for the interaction between seismic faults in an extended region is presented. Faults are represented by boxes formed by a different number of sites and located in the nodes of a fractal tree. Both the distribution of box sizes and the interaction between them is assumed to be hierarchical. Load particles are randomly added to the system, simulating the action of external tectonic forces. These particles fill the sites of the boxes progressively. When a box is full it topples, some of the particles are redistributed to other boxes and some of them are lost. A box relaxation simulates the occurrence of an earthquake in the region. The particle redistributions mostly occur upwards (to larger faults) and downwards (to smaller faults) in the hierarchy producing new relaxations. A simple and efficient bookkeeping of the information allows the running of systems with more than fifty million faults. This model is consistent with the definition of magnitude, i.e., earthquakes of magnitude m take place in boxes with a number of sites ten times bigger than those boxes responsible for earthquakes with a magnitude m-1 which are placed in the immediate lower level of the hierarchy. The three parameters of the model have a geometrical nature: the height or number of levels of the fractal tree, the coordination of the tree and the ratio of areas between boxes in two consecutive levels. Besides reproducing several seismicity properties and regularities, this model is used to test the performance of some precursory patterns.

  2. Seismic transducer modeling using ABAQUS

    SciTech Connect

    Stephen R. Novascone

    2004-05-01

    A seismic transducer, known as an orbital vibrator, consists of a rotating imbalance driven by an electric motor. When suspended in a liquid-filled wellbore, vibrations of the device are coupled to the surrounding geologic media. In this mode, an orbital vibrator can be used as an efficient rotating dipole source for seismic imaging. Alternately, the motion of an orbital vibrator is affected by the physical properties of the surrounding media. From this point of view, an orbital vibrator can be used as a stand-alone sensor. The reaction to the surroundings can be sensed and recorded by geophones inside the orbital vibrator. These reactions are a function of the media’s physical properties such as modulus, damping, and density, thereby identifying the rock type. This presentation shows how the orbital vibrator and surroundings were modeled with an ABAQUS acoustic FEM. The FEM is found to compare favorably with theoretical predictions. A 2D FEM and analytical model are compared to an experimental data set. Each model compares favorably with the data set.

  3. Kutch Seismicity And Crustal Structure

    NASA Astrophysics Data System (ADS)

    Reddy, P. R.; Sarkar, D.; Sain, K.; Mooney, W. D.; Catchings, R. D.

    The devastating 2001 Bhuj (western India) earthquake has triggered widespread dis- cussion in the scientific community about the nature and the causes behind such earth- quakes in the Kutch region, and their similarities or differences with earthquakes elsewhere (particularly the 1811-1812 New Madrid earthquake sequence in mid- continental North America). Many unanswered questions remain and these require not only renewed thinking and understanding, but also fresh efforts for additional data gathering. The problem is more acute in the case of the less-studied Kutch region than for the well-researched New Madrid Seismic Zone (NMSZ). Before we can make an objective comparison between these two regions, we have to first update our knowl- edge of Kutch. Here, we summarize the available information about the destructive 2001 Bhuj and other major earthquakes in Kutch and their tectonic setting. We will also examine the current understanding of the seismicity of the NMSZ. We shall also assess the basic data gaps that need to be filled in order to understanding the Kutch earthquakes, and thereby will be in a better position to find commonalties among such intraplate earthquakes.

  4. DISPLACEMENT BASED SEISMIC DESIGN METHODS.

    SciTech Connect

    HOFMAYER,C.MILLER,C.WANG,Y.COSTELLO,J.

    2003-07-15

    A research effort was undertaken to determine the need for any changes to USNRC's seismic regulatory practice to reflect the move, in the earthquake engineering community, toward using expected displacement rather than force (or stress) as the basis for assessing design adequacy. The research explored the extent to which displacement based seismic design methods, such as given in FEMA 273, could be useful for reviewing nuclear power stations. Two structures common to nuclear power plants were chosen to compare the results of the analysis models used. The first structure is a four-story frame structure with shear walls providing the primary lateral load system, referred herein as the shear wall model. The second structure is the turbine building of the Diablo Canyon nuclear power plant. The models were analyzed using both displacement based (pushover) analysis and nonlinear dynamic analysis. In addition, for the shear wall model an elastic analysis with ductility factors applied was also performed. The objectives of the work were to compare the results between the analyses, and to develop insights regarding the work that would be needed before the displacement based analysis methodology could be considered applicable to facilities licensed by the NRC. A summary of the research results, which were published in NUREGICR-6719 in July 2001, is presented in this paper.

  5. Seismic waveform modeling over cloud

    NASA Astrophysics Data System (ADS)

    Luo, Cong; Friederich, Wolfgang

    2016-04-01

    With the fast growing computational technologies, numerical simulation of seismic wave propagation achieved huge successes. Obtaining the synthetic waveforms through numerical simulation receives an increasing amount of attention from seismologists. However, computational seismology is a data-intensive research field, and the numerical packages usually come with a steep learning curve. Users are expected to master considerable amount of computer knowledge and data processing skills. Training users to use the numerical packages, correctly access and utilize the computational resources is a troubled task. In addition to that, accessing to HPC is also a common difficulty for many users. To solve these problems, a cloud based solution dedicated on shallow seismic waveform modeling has been developed with the state-of-the-art web technologies. It is a web platform integrating both software and hardware with multilayer architecture: a well designed SQL database serves as the data layer, HPC and dedicated pipeline for it is the business layer. Through this platform, users will no longer need to compile and manipulate various packages on the local machine within local network to perform a simulation. By providing users professional access to the computational code through its interfaces and delivering our computational resources to the users over cloud, users can customize the simulation at expert-level, submit and run the job through it.

  6. Methane and seismicity: A reply

    NASA Astrophysics Data System (ADS)

    Gold, Thomas; Soter, Steven

    In a recent Forum article in Eos (“Methane in Association With Seismic Activity,” June 14, 1983, p. 410), R. S. Oremland presents observations which he claims contradict the deep methane gas hypothesis. His principal case rests on observations of one M 5.7 earthquake near the volcanic area of Mammouth Lakes, California, which did not result in any increase in methane content of gases in four local seeps.In our published discussions of the deep gas hypothesis [Gold and Soter, 1980, 1982], we proposed (1) that outgassing from mantle depths is an ongoing process both in volcanic and nonvolcanic regions; (2) that the gases CO2 and CH4 are the principal carriers of the surface excess carbon; (3) that chemical equilibrium between CO2 and CH4 in the presence of hot or liquid rock is strongly shifted towards CO2, especially in the low pressure domain, and that therefore active volcanic or high heat flow regions would be less likely to exhibit CH4; and (4) that faultlines, particularly those which are seismically active, are locations where outgassing in cool regions can be sampled. The evidence there is that flames from the ground are often seen in association with major earthquakes. (Just as in many mud volcano eruptions, ignition of combustible gases can be attributed to electrostatic effects.) Methane is also observed in many of the major crustal rifts, together with helium having the high 3He to 4He ratio indicative of deep origin [Lupton, 1983].

  7. Hanford Seismic Report for Fiscal Year 2000

    SciTech Connect

    Hartshorn, D.C.; Reidel, S.; Rohay, A.C.

    2000-02-23

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its contractors. Hanford Seismic Monitoring also locates and identifies sources of seismic activity and monitors changes in the historical pattern of seismic activity at the Hanford Site. The data are compiled, archived, and published for use by the Hanford Site for waste management, Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of a significant earthquake on the Hanford Site. The HSN and the Eastern Washington Regional Network (EWRN) consist of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The HSN uses 21 sites and the EWRN uses 36 sites; both networks share 16 sites. The networks have 46 combined data channels because Gable Butte and Frenchman Hills East are three-component sites. The reconfiguration of the telemetry and recording systems was completed during the first quarter. All leased telephone lines have been eliminated and radio telemetry is now used exclusively. For the HSN, there were 311 triggers on two parallel detection and recording systems during the first quarter of fiscal year (FY) 2000. Twelve seismic events were located by the Hanford Seismic Network within the reporting region of 46{degree}-47{degree}N latitude and 119{degree}-120{degree}W longitude; 2 were earthquakes in the Columbia River Basalt Group, 3 were earthquakes in the pre-basalt sediments, 9 were earthquakes in the crystalline basement, and 1 was a quarry blast. Two earthquakes appear to be related to a major geologic structure, no earthquakes occurred in known swarm areas, and 9 earthquakes were random occurrences. No earthquakes triggered the Hanford Strong Motion

  8. Seismic risk assessment and application in the central United States

    USGS Publications Warehouse

    Wang, Z.

    2011-01-01

    Seismic risk is a somewhat subjective, but important, concept in earthquake engineering and other related decision-making. Another important concept that is closely related to seismic risk is seismic hazard. Although seismic hazard and seismic risk have often been used interchangeably, they are fundamentally different: seismic hazard describes the natural phenomenon or physical property of an earthquake, whereas seismic risk describes the probability of loss or damage that could be caused by a seismic hazard. The distinction between seismic hazard and seismic risk is of practical significance because measures for seismic hazard mitigation may differ from those for seismic risk reduction. Seismic risk assessment is a complicated process and starts with seismic hazard assessment. Although probabilistic seismic hazard analysis (PSHA) is the most widely used method for seismic hazard assessment, recent studies have found that PSHA is not scientifically valid. Use of PSHA will lead to (1) artifact estimates of seismic risk, (2) misleading use of the annual probability of exccedance (i.e., the probability of exceedance in one year) as a frequency (per year), and (3) numerical creation of extremely high ground motion. An alternative approach, which is similar to those used for flood and wind hazard assessments, has been proposed. ?? 2011 ASCE.

  9. Seismic Noise Analysis and Reduction through Utilization of Collocated Seismic and Atmospheric Sensors at the GRO Chile Seismic Network

    NASA Astrophysics Data System (ADS)

    Farrell, M. E.; Russo, R. M.

    2013-12-01

    The installation of Earthscope Transportable Array-style geophysical observatories in Chile expands open data seismic recording capabilities in the southern hemisphere by nearly 30%, and has nearly tripled the number of seismic stations providing freely-available data in southern South America. Through the use of collocated seismic and atmospheric sensors at these stations we are able to analyze how local atmospheric conditions generate seismic noise, which can degrade data in seismic frequency bands at stations in the ';roaring forties' (S latitudes). Seismic vaults that are climate-controlled and insulated from the local environment are now employed throughout the world in an attempt to isolate seismometers from as many noise sources as possible. However, this is an expensive solution that is neither practical nor possible for all seismic deployments; and also, the increasing number and scope of temporary seismic deployments has resulted in the collection and archiving of terabytes of seismic data that is affected to some degree by natural seismic noise sources such as wind and atmospheric pressure changes. Changing air pressure can result in a depression and subsequent rebound of Earth's surface - which generates low frequency noise in seismic frequency bands - and even moderate winds can apply enough force to ground-coupled structures or to the surface above the seismometers themselves, resulting in significant noise. The 10 stations of the permanent Geophysical Reporting Observatories (GRO Chile), jointly installed during 2011-12 by IRIS and the Chilean Servicio Sismológico, include instrumentation in addition to the standard three seismic components. These stations, spaced approximately 300 km apart along the length of the country, continuously record a variety of atmospheric data including infrasound, air pressure, wind speed, and wind direction. The collocated seismic and atmospheric sensors at each station allow us to analyze both datasets together, to

  10. Multiscale seismic attributes: source-corrected wavelet response and application to high-resolution seismic data

    NASA Astrophysics Data System (ADS)

    Ker, Stephan; Le Gonidec, Yves; Gibert, Dominique

    2012-09-01

    A wavelet-based method was presented in a previous work to introduce multiscale seismic attributes for high-resolution seismic data. Because of the limited frequency bandwidth of the seismic source, we observed distortions in the seismic attributes based on the wavelet response of the subsurface discontinuities (Le Gonidec et al.). In this paper, we go further in the seismic source-correction by considering Lévy alpha-stable distributions introduced in the formalism of the continuous wavelet transform (CWT). The wavelets are Gaussian derivative functions (GDF), characterized by a derivative order. We show that a high-resolution seismic source, after a classical signature processing, can be taken into account with a GDF. We demonstrate that in the framework of the Born approximation, the CWT of a seismic trace involving such a finite frequency bandwidth can be made equivalent to the CWT of the impulse response of the subsurface and is defined for a reduced range of dilations. We apply the method for the SYSIF seismic device (Marsset et al.; Ker et al.) and show that the source-corrections allow to define seismic attributes for layer thicknesses in the range [24; 115 cm]. We present the analysis for two seismic reflectors identified on a SYSIF profile, and we show that the source-corrected multiscale analysis quantifies their complex geometries.

  11. Natural fracture characterization using passive seismic illumination

    SciTech Connect

    Nihei, K.T.

    2003-01-08

    The presence of natural fractures in reservoir rock can significantly enhance gas production, especially in tight gas formations. Any general knowledge of the existence, location, orientation, spatial density, and connectivity of natural fractures, as well as general reservoir structure, that can be obtained prior to active seismic acquisition and drilling can be exploited to identify key areas for subsequent higher resolution active seismic imaging. Current practices for estimating fracture properties before the acquisition of surface seismic data are usually based on the assumed geology and tectonics of the region, and empirical or fracture mechanics-based relationships between stratigraphic curvature and fracturing. The objective of this research is to investigate the potential of multicomponent surface sensor arrays, and passive seismic sources in the form of local earthquakes to identify and characterize potential fractured gas reservoirs located near seismically active regions. To assess the feasibility of passive seismic fracture detection and characterization, we have developed numerical codes for modeling elastic wave propagation in reservoir structures containing multiple, finite-length fractures. This article describes our efforts to determine the conditions for favorable excitation of fracture converted waves, and to develop an imaging method that can be used to locate and characterize fractures using multicomponent, passive seismic data recorded on a surface array.

  12. Structural concepts and details for seismic design

    SciTech Connect

    Not Available

    1991-09-01

    This manual discusses building and building component behavior during earthquakes, and provides suggested details for seismic resistance which have shown by experience to provide adequate performance during earthquakes. Special design and construction practices are also described which, although they might be common in some high-seismic regions, may not be common in low and moderate seismic-hazard regions of the United States. Special attention is given to describing the level of detailing appropriate for each seismic region. The UBC seismic criteria for all seismic zones is carefully examined, and many examples of connection details are given. The general scope of discussion is limited to materials and construction types common to Department of Energy (DOE) sites. Although the manual is primarily written for professional engineers engaged in performing seismic-resistant design for DOE facilities, the first two chapters, plus the introductory sections of succeeding chapters, contain descriptions which are also directed toward project engineers who authorize, review, or supervise the design and construction of DOE facilities. 88 refs., 188 figs.

  13. Code for Calculating Regional Seismic Travel Time

    SciTech Connect

    BALLARD, SANFORD; HIPP, JAMES; & BARKER, GLENN

    2009-07-10

    The RSTT software computes predictions of the travel time of seismic energy traveling from a source to a receiver through 2.5D models of the seismic velocity distribution within the Earth. The two primary applications for the RSTT library are tomographic inversion studies and seismic event location calculations. In tomographic inversions studies, a seismologist begins with number of source-receiver travel time observations and an initial starting model of the velocity distribution within the Earth. A forward travel time calculator, such as the RSTT library, is used to compute predictions of each observed travel time and all of the residuals (observed minus predicted travel time) are calculated. The Earth model is then modified in some systematic way with the goal of minimizing the residuals. The Earth model obtained in this way is assumed to be a better model than the starting model if it has lower residuals. The other major application for the RSTT library is seismic event location. Given an Earth model, an initial estimate of the location of a seismic event, and some number of observations of seismic travel time thought to have originated from that event, location codes systematically modify the estimate of the location of the event with the goal of minimizing the difference between the observed and predicted travel times. The second application, seismic event location, is routinely implemented by the military as part of its effort to monitor the Earth for nuclear tests conducted by foreign countries.

  14. Code for Calculating Regional Seismic Travel Time

    Energy Science and Technology Software Center (ESTSC)

    2009-07-10

    The RSTT software computes predictions of the travel time of seismic energy traveling from a source to a receiver through 2.5D models of the seismic velocity distribution within the Earth. The two primary applications for the RSTT library are tomographic inversion studies and seismic event location calculations. In tomographic inversions studies, a seismologist begins with number of source-receiver travel time observations and an initial starting model of the velocity distribution within the Earth. A forwardmore » travel time calculator, such as the RSTT library, is used to compute predictions of each observed travel time and all of the residuals (observed minus predicted travel time) are calculated. The Earth model is then modified in some systematic way with the goal of minimizing the residuals. The Earth model obtained in this way is assumed to be a better model than the starting model if it has lower residuals. The other major application for the RSTT library is seismic event location. Given an Earth model, an initial estimate of the location of a seismic event, and some number of observations of seismic travel time thought to have originated from that event, location codes systematically modify the estimate of the location of the event with the goal of minimizing the difference between the observed and predicted travel times. The second application, seismic event location, is routinely implemented by the military as part of its effort to monitor the Earth for nuclear tests conducted by foreign countries.« less

  15. Moon meteoritic seismic hum: Steady state prediction

    USGS Publications Warehouse

    Lognonne, P.; Feuvre, M.L.; Johnson, C.L.; Weber, R.C.

    2009-01-01

    We use three different statistical models describing the frequency of meteoroid impacts on Earth to estimate the seismic background noise due to impacts on the lunar surface. Because of diffraction, seismic events on the Moon are typically characterized by long codas, lasting 1 h or more. We find that the small but frequent impacts generate seismic signals whose codas overlap in time, resulting in a permanent seismic noise that we term the "lunar hum" by analogy with the Earth's continuous seismic background seismic hum. We find that the Apollo era impact detection rates and amplitudes are well explained by a model that parameterizes (1) the net seismic impulse due to the impactor and resulting ejecta and (2) the effects of diffraction and attenuation. The formulation permits the calculation of a composite waveform at any point on the Moon due to simulated impacts at any epicentral distance. The root-mean-square amplitude of this waveform yields a background noise level that is about 100 times lower than the resolution of the Apollo long-period seismometers. At 2 s periods, this noise level is more than 1000 times lower than the low noise model prediction for Earth's microseismic noise. Sufficiently sensitive seismometers will allow the future detection of several impacts per day at body wave frequencies. Copyright 2009 by the American Geophysical Union.

  16. Factors Affecting Seismic Velocity in Alluvium

    NASA Astrophysics Data System (ADS)

    Huckins-Gang, H.; Mercadante, J.; Prothro, L.

    2015-12-01

    Yucca Flat at the Nevada National Security Site has been selected as the Source Physics Experiment (SPE) Dry Alluvium Geology Phase II site. The alluvium in this part of Yucca Flat is typical of desert basin fill, with discontinuous beds that are highly variable in clast size and provenance. Detailed understanding of the subsurface geology will be needed for interpretation of the SPE seismic data. A 3D seismic velocity model, created for Yucca Flat using interval seismic velocity data, shows variations in velocity within alluvium near the SPE Phase II site beyond the usual gradual increase of density with depth due to compaction. In this study we examined borehole lithologic logs, geophysical logs, downhole videos, and laboratory analyses of sidewall core samples to understand which characteristics of the alluvium are related to these variations in seismic velocity. Seismic velocity of alluvium is generally related to its density, which can be affected by sediment provenance, clast size, gravel percentage, and matrix properties, in addition to compaction. This study presents a preliminary subdivision of the alluvial strata in the SPE Phase II area into mappable units expected to be significant to seismic modeling. Further refinements of the alluvial units may be possible when seismic data are obtained from SPE Phase II tests. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy.

  17. Seismicity at Jalisco-Nayarit Border, Mexico

    NASA Astrophysics Data System (ADS)

    Rutz, M.; Nunez-Cornu, F.; Camarena, M.; Trejo, E.; Reyes-Davila, G.; Suarez-Plasencia, C.

    2003-12-01

    Since 2002 a regional seismic network from Jalisco Civil Defense and University of Guadalalajara is monitoring seismicity at the northwest border of Jalisco block. With the installation of a seismic station on Ceboruco Volcano, by Nayarit Civil Defense, coverage of the network extends to east. Ceboruco Volcano is located on the Tepic-Zacoalco graben, the east border of Jalisco block, this allow us to begin to monitoring this area. The zone of Bahia de Banderas, between the north coast of Jalisco and south coast of Nayarit, probably on a tectonic triple point, is a region of high seismic potential. Activ tectonic structures and clusters in the zone of El Tuito and the Dam Cajon de Pe¤as have been identified. The seismicity in the north area of the bay is low, meanwhile in the south, where the bay is deeper, the seismicity level is higher with an East-West tendency. At the east, the Amatlan de Ca¤as-Ameca zone presents continue activity, here have been possible to locate events with local magnitude between 2 and 4. Tectonovolcanic events registred at Ceboruco station presents waveform with scattering. The seismic distribution of the coast of Jalisco shows parallel alignments to the trench throughout al the coast. Other perpendicular alignments to the coastline show active morphologic structures within the Jalisco block related to the subduction of the Rivera plate under the Jalisco block.

  18. Alternative Energy Sources in Seismic Methods

    NASA Astrophysics Data System (ADS)

    Tün, Muammer; Pekkan, Emrah; Mutlu, Sunay; Ecevitoğlu, Berkan

    2015-04-01

    When the suitability of a settlement area is investigated, soil-amplification, liquefaction and fault-related hazards should be defined, and the associated risks should be clarified. For this reason, soil engineering parameters and subsurface geological structure of a new settlement area should be investigated. Especially, faults covered with quaternary alluvium; thicknesses, shear-wave velocities and geometry of subsurface sediments could lead to a soil amplification during an earthquake. Likewise, changes in shear-wave velocities along the basin are also very important. Geophysical methods can be used to determine the local soil properties. In this study, use of alternative seismic energy sources when implementing seismic reflection, seismic refraction and MASW methods in the residential areas of Eskisehir/Turkey, were discussed. Our home developed seismic energy source, EAPSG (Electrically-Fired-PS-Gun), capable to shoot 2x24 magnum shotgun cartridges at once to generate P and S waves; and our home developed WD-500 (500 kg Weight Drop) seismic energy source, mounted on a truck, were developed under a scientific research project of Anadolu University. We were able to reach up to penetration depths of 1200 m for EAPSG, and 800 m for WD-500 in our seismic reflection surveys. WD-500 seismic energy source was also used to perform MASW surveys, using 24-channel, 10 m apart, 4.5 Hz vertical geophone configuration. We were able to reach 100 m of penetration depth in MASW surveys.

  19. Seismotectonics and seismic Hazard map of Tunisia

    NASA Astrophysics Data System (ADS)

    Soumaya, Abdelkader; Ben Ayed, Noureddine; Khayati Ammar, Hayet; Kadri, Ali; Zargouni, Fouad; Ghanmi, Mohamed

    2016-04-01

    One natural hazard in Tunisia is caused by earthquakes and one way to measure the shaking risk is the probabilistic seismic-hazard map. The study of seismic hazard and risk assessment in Tunisia started in 1990 within the framework of the National Program for Assessment of Earthquake Risk. Because earthquakes are random events characterized by specific uncertainties, we used a probabilistic method to build the seismic hazard map of Tunisia. Probabilities were derived from the available seismic data and from results of neotectonic, geophysical and geological studies on the main active domains of Tunisia. This map displays earthquake ground motions for various probability levels across Tunisia and it is used in seismic provisions of building codes, insurance rate structures, risk assessment and other public management activities. The product is a seismotectonic map of Tunisia summarizing the available datasets (e.g., active fault, focal mechanism, instrumental and historical seismicity, peak ground acceleration). In addition, we elaborate some thematic seismic hazard maps that represent an important tool for the social and economic development.

  20. Seismic stimulation for enhanced oil recovery

    SciTech Connect

    Pride, S.R.; Flekkoy, E.G.; Aursjo, O.

    2008-07-22

    The pore-scale effects of seismic stimulation on two-phase flow are modeled numerically in random 2D grain0pack geometries. Seismic stimulation aims to enhance oil production by sending seismic waves across a reservoir to liberate immobile patches of oil. For seismic amplitudes above a well-defined (analytically expressed) dimensionless criterion, the force perturbation associated with the waves indeed can liberate oil trapped on capillary barriers and get it flowing again under the background pressure gradient. Subsequent coalescence of the freed oil droplets acts to enhance oil movement further because longer bubbles overcome capillary barriers more efficiently than shorter bubbles do. Poroelasticity theory defines the effective force that a seismic wave adds to the background fluid-pressure gradient. The lattice-Boltzmann model in two dimensions is used to perform pore-scale numerical simulations. Dimensionless numbers (groups of material and force parameters) involved in seismic stimulation are defined carefully so that numerical simulations can be applied to field-scale conditions. Using the analytical criteria defined in the paper, there is a significant range of reservoir conditions over which seismic stimulation can be expected to enhance oil production.

  1. Seismic margins and calibration of piping systems

    SciTech Connect

    Shieh, L.C.; Tsai, N.C.; Yang, M.S.; Wong, W.L.

    1985-01-01

    The Seismic Safety Margins Research Program (SSMRP) is a US Nuclear Regulatory Commission-funded, multiyear program conducted by Lawrence Livermore National Laboratory (LLNL). Its objective is to develop a complete, fully coupled analysis procedure for estimating the risk of earthquake-induced radioactive release from a commercial nuclear power plant and to determine major contributors to the state-of-the-art seismic and systems analysis process and explicitly includes the uncertainties in such a process. The results will be used to improve seismic licensing requirements for nuclear power plants. In Phase I of SSMRP, the overall seismic risk assessment methodology was developed and assembled. The application of this methodology to the seismic PRA (Probabilistic Risk Assessment) at the Zion Nuclear Power Plant has been documented. This report documents the method deriving response factors. The response factors, which relate design calculated responses to best estimate values, were used in the seismic response determination of piping systems for a simplified seismic probablistic risk assessment. 13 references, 31 figures, 25 tables.

  2. Technology creates role for small seismic crews

    SciTech Connect

    Moriarty, B.J. . Kiwi American Energy Inc.)

    1993-09-27

    While the oil and gas industry focuses on large, complex 3D seismic surveys around the world, other, more-quiet changes are taking place. A new breed of small, high-tech seismic crew is emerging as the latest generation of seismic equipment becomes available. Light, economical equipment formerly used for shallow engineering purposes now can produce high-quality data at depths required for oil and gas exploration. Improvements in acquisition technology and equipment reduce costs of seismic surveys, providing new and expanded opportunities in exploration. These improvements include powerful, light recording systems; advanced seismic processing methods; portable processing and analysis on powerful notebook computers; and light, environmentally safe seismic sources. The growing ability of small crews and compact equipment to acquire high-quality data provides operators the option of shooting surveys in especially sensitive areas or of shooting tailor-made surveys in areas of high interest. Niche surveys of this type are especially useful in mature producing areas, such as the U.S. The paper describes the challenges, the dynamic ranges that must be handled (recording weak signals in the presence of strong ones), seismic equipment, and exploration opportunities.

  3. Geological mounds and their seismic expression

    SciTech Connect

    Swarbrick, R.E. )

    1991-03-01

    Mound geometry (convex upward structure developed above a subhorizontal surface) is common in many geological environments and frequently observed in 2-dimensions on seismic sections. Seismic mounds are typically associated with deep-water clastic sediments, e.g. submarine fans and slumps, and with a variety of carbonate depositional settings, e.g., reefs and banks, but also exist in other depositional settings. Recognition will be dependent on mound dimension, velocity contrast, amplitude strength, and the resolution of the seismic data. Since mounds can represent an important exploration target and recognition of porous, hydrocarbon-bearing section is all-important, careful restitution of the original depositional morphology from the seismic data is required. Details of present velocity distribution are critical, along with a realistic concept of any post-depositional modification, such as compaction, which may have taken place during burial. Where differential compaction is taking place, for example between sand and shale, seismic expression of morphology will be continually modified during progressive burial. Analysis of structure at the top and base of the mound can provide support for lithological interpretation based on other criteria, such as seismic facies analysis based on internal and external reflections. Modeling, using parameters from mounds in a variety of known depositional settings, illustrates many of the interpretational problems associated with seismic mounds and provides some objective criteria for analysis of mound morphology. Comparison is made with real data, principally from northwest Europe and North America.

  4. Oceanic crust deep seismic survey

    NASA Astrophysics Data System (ADS)

    McBride, J. H.; White, R. S.

    In September 1991, the British Institutions Reflection Profiling Syndicate (BIRPS) collected 578 km of deep seismic reflection profiles over the oceanic crust beneath the Cape Verde abssyal plain in approximately 4900 m of water (Fig. 1). The survey, under the direction of J. H. McBride, was undertaken in response to a proposal made by R. S. White at the 1990 BIRPS open syndicate meeting in Birmingham, England, and was acquired using GECO-PRAKLA'S M/V Bin Hai 511. The survey consisted of two strike lines parallel to magnetic sea-floor lineations and nine orthogonal crossing lines oriented parallel to the spreading direction (Fig. 2). Adjacent lines are spaced at 4 km. For the first time, this provides the ability to map oceanic crust in “3D,” since the line spacing is less than or equal to the Fresnel-zone diameter for the lower crust.

  5. Quantification of seismic liquefaction risk

    SciTech Connect

    Arango, I.; Ostadan, F.; Lewis, M.R.; Gutierrez, B.J.

    1996-02-29

    Explicit goals of acceptable risk for natural phenomena hazards (earthquake, extreme wind, and flood) have been established by the Department of Energy (DOE) 1994. Closely associated to the earthquake risk is the issue of seismically-induced liquefaction. Because deterministic methods currently available to answer the question to whether a site is liquefiable or not are incapable of providing a clue as to the likelihood or risk of liquefaction, the application of the criteria to a given facility requires that alternative evaluation techniques be formulated. This paper describes the application to a nuclear facility of a newly developed probabilistic methodology which rigorously accounts for geotechnical and seismologic uncertainties. The results of the analyses are compared with the acceptable levels of risk presented by DOE. This comparison is used to emphasize the power of the methodology as a tool in the decision-making processes.

  6. Seismic data acquisition through tubing

    SciTech Connect

    Buettner, H M; Jervis, M

    1999-07-01

    We have collected good quality crosswell seismic data through production tubing in active oil fields at realistic interwell distances (300 ft). The data were collected at the Aera Cymric field (1998) and at a Chevron site (1997); both located in the Central Valley of California. The Aera data were used to produce travel-time tomographic images of the interwell region. Both sites have similar geology, namely siliceous shale (diatomite) with moderate to highly attenuating reservoir rocks. In addition we confirmed modeling predictions that typical tubing attenuation losses are on the order of 12 dB. We expect that the use of stronger sources and tube wave suppression will allow for crosswell imaging at realistic distances even for low Q or high noise situations. We are searching for an industrial partner now for a data collection in the gas wells of the San Juan Basin or South Texas.

  7. Seismic hazard maps for Haiti

    USGS Publications Warehouse

    Frankel, Arthur; Harmsen, Stephen; Mueller, Charles; Calais, Eric; Haase, Jennifer

    2011-01-01

    We have produced probabilistic seismic hazard maps of Haiti for peak ground acceleration and response spectral accelerations that include the hazard from the major crustal faults, subduction zones, and background earthquakes. The hazard from the Enriquillo-Plantain Garden, Septentrional, and Matheux-Neiba fault zones was estimated using fault slip rates determined from GPS measurements. The hazard from the subduction zones along the northern and southeastern coasts of Hispaniola was calculated from slip rates derived from GPS data and the overall plate motion. Hazard maps were made for a firm-rock site condition and for a grid of shallow shear-wave velocities estimated from topographic slope. The maps show substantial hazard throughout Haiti, with the highest hazard in Haiti along the Enriquillo-Plantain Garden and Septentrional fault zones. The Matheux-Neiba Fault exhibits high hazard in the maps for 2% probability of exceedance in 50 years, although its slip rate is poorly constrained.

  8. Regional Observation of Seismic Activity in Baekdu Mountain

    NASA Astrophysics Data System (ADS)

    Kim, Geunyoung; Che, Il-Young; Shin, Jin-Soo; Chi, Heon-Cheol

    2015-04-01

    Seismic unrest in Baekdu Mountain area between North Korea and Northeast China region has called attention to geological research community in Northeast Asia due to her historical and cultural importance. Seismic bulletin shows level of seismic activity in the area is higher than that of Jilin Province of Northeast China. Local volcanic observation shows a symptom of magmatic unrest in period between 2002 and 2006. Regional seismic data have been used to analyze seismic activity of the area. The seismic activity could be differentiated from other seismic phenomena in the region by the analysis.

  9. Mantle compression affects seismic wave propagation

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2014-02-01

    To try to understand the direction of motion of the Earth's mantle, which lies hidden beneath tens of kilometers of crust, researchers have relied on the property of seismic anisotropy. When seismic shear waves pass through some types of materials, known as anisotropic materials, the speed of the wave can vary depending on the direction in which it is moving. Traditionally, scientists have assumed that the direction in which waves move more quickly aligns with the direction of mantle motion. For subduction zones, however, this general rule seemed to break down—a discrepancy exists between numerical model simulations and observed seismic data.

  10. Meteoroid flux from passive seismic experiment data

    NASA Technical Reports Server (NTRS)

    Duennebier, F.; Dorman, J.; Lammlein, D.; Latham, G.; Nakamura, Y.

    1975-01-01

    The meteoroid flux hitting the moon is recomputed using new information on the decrease of seismic signal amplitude with range. The new data are principally 17 large meteoroid impacts whose locations have been computed from recordings at all four of the operating Passive Seismic Experiment stations. These data suggest a rapid decrease in amplitudes beyond about 2200 km (chord range) which was not suspected earlier. The new estimate predicts the abundance of meteoroids with masses between 500 and 50,000 g. The result is considerably lower than estimates from earth-based observations, and close to our previous estimate from long-period lunar seismic data.

  11. Georgia-Armenia Transboarder seismicity studies

    NASA Astrophysics Data System (ADS)

    Godoladze, T.; Tvaradze, N.; Javakishvili, Z.; Elashvili, M.; Durgaryan, R.; Arakelyan, A.; Gevorgyan, M.

    2012-12-01

    In the presented study we performed Comprehensive seismic analyses for the Armenian-Georgian transboarder active seismic fault starting on Armenian territory, cutting the state boarder and having possibly northern termination on Adjara-Triealeti frontal structure in Georgia. In the scope of International projects: ISTC A-1418 "Open network of scientific Centers for mitigation risk of natural hazards in the Southern Caucasus and Central Asia" and NATO SfP- 983284 Project "Caucasus Seismic Emergency Response" in Akhalkalaki (Georgia) seismic center, Regional Summer school trainings and intensive filed investigations were conducted. Main goal was multidisciplinary study of the Javakheti fault structure and better understanding seismicity of the area. Young scientists from Turkey, Armenia, Azerbaijan and Georgia were participated in the deployment of temporal seismic network in order to monitor seisimity on the Javakheti highland and particularly delineate fault scarf and identify active seismic structures. In the scope of international collaboration the common seismic database has been created in the southern Caucasus and collected data from the field works is available now online. Javakheti highland, which is located in the central part of the Caucasus, belongs to the structure of the lesser Caucasus and represents a history of neotectonic volcanism existed in the area. Jasvakheti highland is seismicalu active region devastating from several severe earthquakes(1088, 1283, 1899…). Hypocenters located during analogue network were highly scattered and did not describe real pattern of seismicity of the highland. We relocated hypocenters of the region and improved local velocity model. The hypocenters derived from recently deployed local seismic network in the Javakheti highland, clearly identified seismically active structures. Fault plane solutions of analogue data of the Soviet times have been carefully analyzed and examined. Moment tensor inversion were preformed

  12. Estimation of Seismicity Parameters Using a Computer

    NASA Astrophysics Data System (ADS)

    Veneziano, Daniele

    The book is a translation from an original in Russian, published in 1972. After 15 years, the book appears dated, its emphasis being the use of computers as an innovative technology for seismicity parameter estimation.The book is divided into two parts. Part I (29 pages) reviews the literature for quantitative measures of seismicity and for earthquake recurrence models, and describes previous uses of the computer to determine seismicity parameters. The literature reviewed is mainly that of the 1960s, with prevalence of Russian and European titles. This part of the book may retain some interest for the historical perspective it gives on the subject.

  13. Monitoring gas reservoirs by seismic interferometry

    NASA Astrophysics Data System (ADS)

    Grigoli, Francesco; Cesca, Simone; Sens-Schoenfelder, Christoph; Priolo, Enrico

    2014-05-01

    Ambient seismic noise can be used to image spatial anomalies in the subsurface, without the need of recordings from seismic sources, such as earthquakes or explosions. Furthermore, the temporal variation of ambient seismic noise's can be used to infer temporal changes of the seismic velocities in the investigated medium. Such temporal variations can reflect changes of several physical properties/conditions in the medium. For example, they may be consequence of stress changes, variation of hydrogeological parameters, pore pressure and saturation changes due to fluid injection or extraction. Passive image interferometry allows to continuously monitor small temporal changes of seismic velocities in the subsurface, making it a suitable tool to monitor time-variant systems such as oil and gas reservoirs or volcanic environments. The technique does not require recordings from seismic sources in the classical sense, but is based on the processing of noise records. Moreover, it requires only data from one or two seismic stations, their locations constraining the sampled target area. Here we apply passive image interferometry to monitor a gas storage reservoir in northern Italy. The Collalto field (Northern Italy) is a depleted gas reservoir located at 1500 m depth, now used as a gas storage facility. The reservoir experience a significant temporal variation in the amount of stored gas: the injection phases mainly occur in the summer, while the extraction take place mostly in winter. In order to monitor induced seismicity related to gas storage operations, a seismic network (the Collalto Seismic Network) has been deployed in 2011. The Collalto Seismic Network is composed by 10 broadband stations, deployed within an area of about 20 km x 20 km, and provides high-quality continuous data since January 1st, 2012. In this work we present preliminary results from ambient noise interferometry using a two-months sample of continuous seismic data, i.e. from October 1st, 2012, to the

  14. Man-caused seismicity of Kuzbass

    NASA Astrophysics Data System (ADS)

    Emanov, Alexandr; Emanov, Alexey; Leskova, Ekaterina; Fateyev, Alexandr

    2010-05-01

    A natural seismicity of Kuznetsk Basin is confined in the main to mountain frame of Kuznetsk hollow. In this paper materials of experimental work with local station networks within sediment basin are presented. Two types of seismicity display within Kuznetsk hollow have been understood: first, man-caused seismic processes, confined to mine working and concentrated on depths up to one and a half of km; secondly, seismic activations on depths of 2-56 km, not coordinated in plan with coal mines. Every of studied seismic activations consists of large quantity of earthquakes of small powers (Ms=1-3). From one to first tens of earthquakes were recorded in a day. The earthquakes near mine working shift in space along with mine working, and seismic process become stronger at the instant a coal-plough machine is operated, and slacken at the instant the preventive works are executed. The seismic processes near three lavas in Kuznetsk Basin have been studied in detail. Uplift is the most typical focal mechanism. Activated zone near mine working reach in diameter 1-1,5 km. Seismic activations not linked with mine working testify that the subsoil of Kuznetsk hollow remain in stress state in whole. The most probable causes of man-caused action on hollow are processes, coupled with change of physical state of rocks at loss of methane from large volume or change by mine working of rock watering in large volume. In this case condensed rocks, lost gas and water, can press out upwards, realizing the reverse fault mechanism of earthquakes. A combination of stress state of hollow with man-caused action at deep mining may account for incipient activations in Kuznetsk Basin. Today earthquakes happen mainly under mine workings, though damages of workings themselves do not happen, but intensive shaking on surface calls for intent study of so dangerous phenomena. In 2009 replicates of the experiment on research of seismic activations in area of before investigated lavas have been conducted

  15. Assessment of seismic margin calculation methods

    SciTech Connect

    Kennedy, R.P.; Murray, R.C.; Ravindra, M.K.; Reed, J.W.; Stevenson, J.D.

    1989-03-01

    Seismic margin review of nuclear power plants requires that the High Confidence of Low Probability of Failure (HCLPF) capacity be calculated for certain components. The candidate methods for calculating the HCLPF capacity as recommended by the Expert Panel on Quantification of Seismic Margins are the Conservative Deterministic Failure Margin (CDFM) method and the Fragility Analysis (FA) method. The present study evaluated these two methods using some representative components in order to provide further guidance in conducting seismic margin reviews. It is concluded that either of the two methods could be used for calculating HCLPF capacities. 21 refs., 9 figs., 6 tabs.

  16. Seismic reflection imaging at a Shallow Site

    SciTech Connect

    Milligan, P.; Rector, J.; Bainer, R.

    1997-01-01

    The objective of our studies was to determine the best seismic method to image these sediments, between the water table at 3 m depth to the basement at 35 m depth. Good cross-correlation between well logs and the seismic data was also desirable, and would facilitate the tracking of known lithological units away from the wells. For instance, known aquifer control boundaries may then be mapped out over the boundaries, and may be used in a joint inversion with reflectivity data and other non-seismic geophysical data to produce a 3-D image containing quantitative physical properties of the target area.

  17. 2008 United States National Seismic Hazard Maps

    USGS Publications Warehouse

    Petersen, M.D.; and others

    2008-01-01

    The U.S. Geological Survey recently updated the National Seismic Hazard Maps by incorporating new seismic, geologic, and geodetic information on earthquake rates and associated ground shaking. The 2008 versions supersede those released in 1996 and 2002. These maps are the basis for seismic design provisions of building codes, insurance rate structures, earthquake loss studies, retrofit priorities, and land-use planning. Their use in design of buildings, bridges, highways, and critical infrastructure allows structures to better withstand earthquake shaking, saving lives and reducing disruption to critical activities following a damaging event. The maps also help engineers avoid costs from over-design for unlikely levels of ground motion.

  18. Seismic Retrofit for Electric Power Systems

    SciTech Connect

    Romero, Natalia; Nozick, Linda K.; Dobson, Ian; Xu, Ningxiong; Jones, Dean A.

    2015-05-01

    Our paper develops a two-stage stochastic program and solution procedure to optimize the selection of seismic retrofit strategies to increase the resilience of electric power systems against earthquake hazards. The model explicitly considers the range of earthquake events that are possible and, for each, an approximation of the distribution of damage experienced. Furthermore, this is important because electric power systems are spatially distributed and so their performance is driven by the distribution of component damage. We also test this solution procedure against the nonlinear integer solver in LINGO 13 and apply the formulation and solution strategy to the Eastern Interconnection, where seismic hazard stems from the New Madrid seismic zone.

  19. Frictional melt and seismic slip

    NASA Astrophysics Data System (ADS)

    Nielsen, S.; di Toro, G.; Hirose, T.; Shimamoto, T.

    2008-01-01

    Frictional melt is implied in a variety of processes such as seismic slip, ice skating, and meteorite combustion. A steady state can be reached when melt is continuously produced and extruded from the sliding interface, as shown recently in a number of laboratory rock friction experiments. A thin, low-viscosity, high-temperature melt layer is formed resulting in low shear resistance. A theoretical solution describing the coupling of shear heating, thermal diffusion, and extrusion is obtained, without imposing a priori the melt thickness. The steady state shear traction can be approximated at high slip rates by the theoretical form τss = σn1/4 (A/?) ? under a normal stress σn, slip rate V, radius of contact area R (A is a dimensional normalizing factor and W is a characteristic rate). Although the model offers a rather simplified view of a complex process, the predictions are compatible with experimental observations. In particular, we consider laboratory simulations of seismic slip on earthquake faults. A series of high-velocity rotary shear experiments on rocks, performed for σn in the range 1-20 MPa and slip rates in the range 0.5-2 m s-1, is confronted to the theoretical model. The behavior is reasonably well reproduced, though the effect of radiation loss taking place in the experiment somewhat alters the data. The scaling of friction with σn, R, and V in the presence of melt suggests that extrapolation of laboratory measures to real Earth is a highly nonlinear, nontrivial exercise.

  20. Hierarchical model for distributed seismicity.

    PubMed

    Tejedor, Alejandro; Gómez, Javier B; Pacheco, Amalio F

    2010-07-01

    A cellular automata model for the interaction between seismic faults in an extended region is presented. Faults are represented by boxes formed by a different number of sites and located in the nodes of a fractal tree. Both the distribution of box sizes and the interaction between them is assumed to be hierarchical. Load particles are randomly added to the system, simulating the action of external tectonic forces. These particles fill the sites of the boxes progressively. When a box is full it topples, some of the particles are redistributed to other boxes and some of them are lost. A box relaxation simulates the occurrence of an earthquake in the region. The particle redistributions mostly occur upwards (to larger faults) and downwards (to smaller faults) in the hierarchy producing new relaxations. A simple and efficient bookkeeping of the information allows the running of systems with more than fifty million faults. This model is consistent with the definition of magnitude, i.e., earthquakes of magnitude m take place in boxes with a number of sites ten times bigger than those boxes responsible for earthquakes with a magnitude m-1 which are placed in the immediate lower level of the hierarchy. The three parameters of the model have a geometrical nature: the height or number of levels of the fractal tree, the coordination of the tree and the ratio of areas between boxes in two consecutive levels. Besides reproducing several seismicity properties and regularities, this model is used to test the performance of some precursory patterns. PMID:20866700

  1. SeismicCanvas: Interactive software for accessing and analyzing seismic waveform data

    NASA Astrophysics Data System (ADS)

    Kroeger, G. C.

    2011-12-01

    SeismicCavas, a cross-platform, graphically interactive application for accessing and analyzing waveform data is presented. Unlike command-line driven packages like SAC and MatSeis, SeismicCanvas adopts a graphically interactive interface to minimize the learning curve for classroom and laboratory application. The menu structure is patterned after common desktop word processing and spreadsheet applications. Direct graphical interaction with traces adopts a "select, then operate" paradigm used in familiar desktop graphics packages. Viewing options include arbitrary arrangement of traces, seismic sections, spectra and spectrograms. Operations include stacking, filtering, windowing and tapering. Interactive picking and measurement of times and amplitudes and WYSIWYG printing are implemented. SeismicCanvas can import data from local files, or through the new web services interface of the IRIS Data Management System. We invite feedback including suggestions for changes to the user interface or additional capabilities that will allow SeismicCanvas to support classroom and laboratory use of digital seismic data.

  2. Seismic-while-drilling data processing with seismic interferometry in the Daqing Oilfield experiment

    NASA Astrophysics Data System (ADS)

    Liu, Hongtao 1Huang, Weichuan 24Li, Yuquan

    2014-03-01

    Seismic interferometry was used to process the data collected with seismic-while-drilling (SWD) experiments at the Daqing Oilfield. The experiments simultaneously recorded the data at the drilling stem and on the ground. After conducting the frequency and the energy property analysis, the data was processed using the correlation and deconvolution method. Seismic data was then obtained from excitation of the drill bit. The result maps show that the deconvolution method can suppress the source effects and enhance the resolution of the profile, and that the vertical stacks enhance the seismic response of the subsurface. The interferometry process after band-filtering can obtain maps with very high resolution. Seismic interferometry by deconvolution shows great advantages based on the results of this experimental data. The method can also be applied to the SWD data and the ambient seismic data to obtain better processing results.

  3. Evaluation of induced seismicity forecast models in the Induced Seismicity Test Bench

    NASA Astrophysics Data System (ADS)

    Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan

    2016-04-01

    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. Here, we propose an Induced Seismicity Test Bench to test and rank such models. 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 that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and Seismics (HySei). SiS is based on three pillars: the seismicity rate is computed with help of the seismogenic index and a simple exponential decay of the seismicity; the magnitude distribution follows the Gutenberg-Richter relation; and seismicity is distributed in space based on smoothing seismicity during the learning period with 3D Gaussian kernels. The HySei model describes seismicity triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the seismicity rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the seismicity rate. 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. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.

  4. Seismic Empirical Relations for the Tellian Atlas, North Africa, and their Usefulness for Seismic Risk Assessment

    NASA Astrophysics Data System (ADS)

    Beghoul, Noureddine; Chatelain, Jean-Luc; Boughacha, Mohamed-Salah; Benhallou, Hadj; Dadou, Rida; Mezioud-Saïch, Amira

    2010-03-01

    Seismic events that occurred during the past half century in the Tellian Atlas, North Africa, are used to establish fundamental seismic empirical relations, tying earthquake magnitude to source parameters (seismic moment, fault plane area, maximal displacement along the fault, and fault plane length). Those empirical relations applied to the overall seismicity from 1716 to present are used to transform the magnitude (or intensity) versus time distribution into (1) cumulative seismic moment versus time, and (2) cumulative displacements versus time. Both of those parameters as well as the computed seismic moment rate, the strain rate along the Tellian Atlas strike, and various other geological observations are consistent with the existence, in the Tellian Atlas, of three distinct active tectonic blocks. These blocks are seismically decoupled from each other, thus allowing consideration of the seismicity as occurring in three different distinct seismotectonic blocks. The cumulative displacement versus time from 1900 to present for each of these tectonic blocks presents a remarkable pattern of recurrence time intervals and precursors associated with major earthquakes. Indeed, most major earthquakes that occurred in these three blocks might have been predicted in time. The Tellian Atlas historical seismicity from the year 881 to the present more substantially confirms these observations, in particular for the western block of the Tellian Atlas. Theoretical determination of recurrence time intervals for the Tellian Atlas large earthquakes using Molnar and Kostrov formalisms is also consistent with these observations. Substantial observations support the fact that the western and central Tellian Atlas are currently at very high seismic risk, in particular the central part. Indeed, most of the accumulated seismic energy in the central Tellian Atlas crust has yet to be released, despite the occurrence of the recent destructive May 2003 Boumerdes earthquake ( M w = 6.8). The

  5. A prediction of mars seismicity from surface faulting

    USGS Publications Warehouse

    Golombek, M.P.; Banerdt, W.B.; Tanaka, K.L.; Tralli, D.M.

    1992-01-01

    The shallow seismicity of Mars has been estimated by measurement of the total slip on faults visible on the surface of the planet throughout geologic time. Seismicity was calibrated with estimates based on surface structures on the moon and measured lunar seismicity that includes the entire seismogenic lithosphere. Results indicate that Mars is seismically active today, with a sufficient number of detectable marsquakes to allow seismic investigations of its interior.

  6. Features of seismicity of the Euro-Arctic region

    NASA Astrophysics Data System (ADS)

    Rogozhin, E. A.; Antonovskaya, G. N.; Kapustian, N. K.; Fedorenko, I. V.

    2016-04-01

    New results from seismic monitoring in the Euro-Arctic region, including the seismicity of Gakkel Ridge and the Barents-Kara Sea shelf, are presented. The data used were obtained from the Arkhan-gelsk seismic network. The role of island-based seismic stations, in particular, those in Franz Josef Land, in the monitoring network is discussed. The possibility of specifying the nature of seismicity by waveform spectral-temporal analysis, even in the case of a single station, is considered.

  7. Seismic Pulses Derivation from the Study of Source Signature Characteristics

    SciTech Connect

    Rahman, Syed Mustafizur; Nawawi, M. N. Mohd.; Saad, Rosli

    2010-07-07

    This paper deals with a deterministic technique for the derivation of seismic pulses by the study of source characteristics. The spectral characteristics of the directly or the nearest detected seismic signal is analyzed and considered as the principle source signature. Using this signature seismic pulses are derived with accurate time position in the seismic traces. The technique is applied on both synthetic and field refraction seismic traces. In both cases it has estimated that the accurate time shifts along with amplitude coefficients.

  8. Seismic transducer measures small horizontal displacements

    NASA Technical Reports Server (NTRS)

    Greenwood, T. L.

    1965-01-01

    Pendular seismic transducer mounted on base plate measures small horizontal displacements of structures subjected to vibration where no fixed reference point is available. Enclosure of transducer in transparent plastic case prevents air currents from disturbing the pendulum balance.

  9. THK: CLB Crossed Linear Bearing Seismic Isolators

    SciTech Connect

    Toniolo, Roberto

    2008-07-08

    This text highlights the new seismic isolation technology called CLB (Crossed Linear Bearing), which is made of linear guides with recirculating steel ball technology. It describes specifications and building characteristics, provides examples of seismic isolation and application functionalities and shows experimental data. Since 1994, the constant commitment by Japan to develop diversified anti-seismic systems based on the precise needs of the structures to protect and the areas where they were built has led to the creation of important synergy between the research institutions of leading Japanese companies and THK's Centre for Research and Development. Their goal has been to develop new technology and solutions to allow seismic isolation to be effective in the following cases:.

  10. Q analysis on reflection seismic data

    NASA Astrophysics Data System (ADS)

    Wang, Yanghua

    2004-09-01

    Q analysis refers to the procedure for estimating Q directly from a reflection seismic trace. Conventional Q analysis method compares two seismic wavelets selected from different depth (or time) levels, but picking ``clean'' wavelets without interferences from other wavelet and noise from a reflection seismic trace is really a problem. Therefore, instead of analysing individual wavelets, I perform Q analysis using the Gabor transform spectrum which reveals the frequency content changing with time in a seismic trace. I propose two Q analysis methods based on the attenuation function and compensation function, respectively, each of which may produce a series of average values of Q-1 (inverse Q), averaging between the recording surface (or the water bottom) and the subsurface time samples. But the latter is much more stable than the former one. I then calculate the interval or layered values of Q-1 by a constrained linear inversion, which produces a stable estimation of the interval-Q series.

  11. Differential equation-based seismic data filtering

    SciTech Connect

    Li, Jianchao; Larner, K.

    1992-05-01

    Suppressing noise and enhancing useful seismic signal by filtering is one of the important tasks of seismic data processing. conventional filtering methods are implemented through either the convolution operation or various mathematical transforms. In this paper, we describe a methodology for studying and implementing filters, which, unlike those conventional filtering methods, is based on solving differential equations in the time and space domain. We call this kind of filtering differential equation-based filtering (DEBF). DEBF does not require that seismic data be stationary, so filtering parameters can vary with every time and space point. Also, in 2-D and 3-D, DEBF has higher computational efficiency than do conventional multiple-trace filtering methods. Examples with synthetic and field seismic data show the DEBF methods presented here to be efficient and effective.

  12. Seismic waveform viewer, processor and calculator

    Energy Science and Technology Software Center (ESTSC)

    2015-02-15

    SWIFT is a computer code that is designed to do research level signal analysis on seismic waveforms, including visualization, filtering and measurement. LLNL is using this code, amplitude and global tomography efforts.

  13. Evaluation of seismic interactions: Guidelines and application

    SciTech Connect

    Antaki, G.A.; Flanders, H.E.; Thomas, B.D.

    1992-06-01

    It is readily recognized that a significant source of damage from earthquakes is due to interactions between structures and components, such as the fall of a masonry wall or a ceiling on equipment, or the impact of a valve on a wall or structure. There are also other significant, while less intuitively evident, sources of seismic interaction damage, such as flooding, spraying, fires, or electrical shorts. The understanding of all these sources of interaction damage and their evaluation in the field can easily turn into a significant effort. Yet, it is the opinion of the Senior Seismic Review and Advisory Panel (SSRAP) that the evaluation of interactions, in a commercial nuclear power plant, should account for about 10 to 20% of the seismic ``walkdown`` devoted to equipment seismic qualification. To this end, SSRAP recognizes the need for ``exercising of considerable judgement and experience -- so that the program remains cost effective.``

  14. Quarterly seismic monitoring report 96B

    SciTech Connect

    Reidel, S.P.

    1996-06-12

    This report summarizes the location, magnitude, and other pertinent information on earthquakes recorded on and near the Hanford Site by Westinghouse Seismic Monitoring during the period encompassing January 1, 1996 to March 31, 1996.

  15. A seismic metamaterial: The resonant metawedge

    PubMed Central

    Colombi, Andrea; Colquitt, Daniel; Roux, Philippe; Guenneau, Sebastien; Craster, Richard V.

    2016-01-01

    Critical concepts from three different fields, elasticity, plasmonics and metamaterials, are brought together to design a metasurface at the geophysical scale, the resonant metawedge, to control seismic Rayleigh waves. Made of spatially graded vertical subwavelength resonators on an elastic substrate, the metawedge can either mode convert incident surface Rayleigh waves into bulk elastic shear waves or reflect the Rayleigh waves creating a “seismic rainbow” effect analogous to the optical rainbow for electromagnetic metasurfaces. Time-domain spectral element simulations demonstrate the broadband efficacy of the metawedge in mode conversion while an analytical model is developed to accurately describe and predict the seismic rainbow effect; allowing the metawedge to be designed without the need for extensive parametric studies and simulations. The efficiency of the resonant metawedge shows that large-scale mechanical metamaterials are feasible, will have application, and that the time is ripe for considering many optical devices in the seismic and geophysical context. PMID:27283587

  16. A seismic metamaterial: The resonant metawedge.

    PubMed

    Colombi, Andrea; Colquitt, Daniel; Roux, Philippe; Guenneau, Sebastien; Craster, Richard V

    2016-01-01

    Critical concepts from three different fields, elasticity, plasmonics and metamaterials, are brought together to design a metasurface at the geophysical scale, the resonant metawedge, to control seismic Rayleigh waves. Made of spatially graded vertical subwavelength resonators on an elastic substrate, the metawedge can either mode convert incident surface Rayleigh waves into bulk elastic shear waves or reflect the Rayleigh waves creating a "seismic rainbow" effect analogous to the optical rainbow for electromagnetic metasurfaces. Time-domain spectral element simulations demonstrate the broadband efficacy of the metawedge in mode conversion while an analytical model is developed to accurately describe and predict the seismic rainbow effect; allowing the metawedge to be designed without the need for extensive parametric studies and simulations. The efficiency of the resonant metawedge shows that large-scale mechanical metamaterials are feasible, will have application, and that the time is ripe for considering many optical devices in the seismic and geophysical context. PMID:27283587

  17. A seismic metamaterial: The resonant metawedge

    NASA Astrophysics Data System (ADS)

    Colombi, Andrea; Colquitt, Daniel; Roux, Philippe; Guenneau, Sebastien; Craster, Richard V.

    2016-06-01

    Critical concepts from three different fields, elasticity, plasmonics and metamaterials, are brought together to design a metasurface at the geophysical scale, the resonant metawedge, to control seismic Rayleigh waves. Made of spatially graded vertical subwavelength resonators on an elastic substrate, the metawedge can either mode convert incident surface Rayleigh waves into bulk elastic shear waves or reflect the Rayleigh waves creating a “seismic rainbow” effect analogous to the optical rainbow for electromagnetic metasurfaces. Time-domain spectral element simulations demonstrate the broadband efficacy of the metawedge in mode conversion while an analytical model is developed to accurately describe and predict the seismic rainbow effect; allowing the metawedge to be designed without the need for extensive parametric studies and simulations. The efficiency of the resonant metawedge shows that large-scale mechanical metamaterials are feasible, will have application, and that the time is ripe for considering many optical devices in the seismic and geophysical context.

  18. "Interactive Seismics", Aki & Richards, Chapter 16

    NASA Astrophysics Data System (ADS)

    Leary, P. C.; Walter, L.; Crampin, S.

    2004-12-01

    The defining physical character of cold brittle crustal rock hosting geofluid reservoirs and earthquake instabilities is '1/f-noise' spatially-correlated fluctuations in fracture-density. Evidence for 1/f-noise fracture-density fluctuations is manifest in power-law-scaling well-log spectra from <1/km to >1/cm, spatial correlation of well-core porosity and log(permeability), and the Gutenberg-Richter relation. Unlike spatially-uncorrelated randomness, power-law-scaling spatially-correlated randomness provides no reliable spatio-predictive relation between a sample and the whole. In particular, no point-measurement sequence in a crustal reservoir -- static well-log, temporal pressure-log or strain-log, or earthquake locations - accurately samples a reservoir state. Rather, useful knowledge of a reservoir state requires broadband observation of the whole reservoir as it is perturbed. Such observations could be called 'interactive seismics'. 'Interactive seismics' reservoir monitoring is becoming routine in the oil and gas industry, as embedded sensors record time-lapse source signals to determine where water replaces produced oil and gas. Interactive seismics is feasible with CO2 injection, and may become feasible for active fault zones. Interactive seismics benefits from stable downhole sources and sensors. Imperatives for better hydrocarbon reservoir observation are providing compact, robust, stable seismic sources and vector-sensors, and the means to deploy them downhole. Extensive crosswell seismic data, including monitored travel-times in a tectonically active crust, establish useful performance levels for downhole seismic sourcing at wavelengths 5-50m: crosswell transmission scale ˜1km, single-well back-scattering scale ˜200m, source wavelet stability \\delta S/S ˜ 0.03%, and travel-time resolution \\delta\\tau/\\tau ˜ 0.03%. Using the attested downhole source parameters, we simulate interactive seismic observation of a 1/f-noise fracture volume undergoing

  19. The low-grade Canal de las Montañas Shear Zone and its role in the tectonic emplacement of the Sarmiento Ophiolitic Complex and Late Cretaceous Patagonian Andes orogeny, Chile

    NASA Astrophysics Data System (ADS)

    Calderón, M.; Fosdick, J. C.; Warren, C.; Massonne, H.-J.; Fanning, C. M.; Cury, L. Fadel; Schwanethal, J.; Fonseca, P. E.; Galaz, G.; Gaytán, D.; Hervé, F.

    2012-02-01

    The Canal de las Montañas Shear Zone (CMSZ), southern Patagonian Andes (51-52°S), is a low-grade mylonite belt generated from felsic ignimbritic, pelitic and basaltic protoliths of the Late Jurassic-Early Cretaceous Rocas Verdes basin. The different types of rock fabrics across the CMSZ are thought to be associated with relatively intermediate and high strain conditions, characterized by the development of a narrow western belt of S-Ć-type mylonites and phyllonites interpreted as the metamorphic sole thrust of the Sarmiento Ophiolitic Complex. Highly strained rocks of the CMSZ display a reverse, continent-ward tectonic transport, with a minor dextral component of shearing. Transitional pumpellyite-actinolite and upper greenschist facies metamorphic conditions at ca. 5-6 kbar and 230-260 °C indicate that the primary shearing event occurred in a subduction zone setting. In-situ 40Ar/39Ar laserprobe chronology yielded ages of ca. 85 Ma on syntectonic phengite which are interpreted as representing cooling synchronous with mica crystallization during the main compressive deformational event. The 78-81 Ma U-Pb zircon crystallization ages of cross-cutting plutonic and hypabyssal rocks and 40Ar/39Ar amphibole age of ca.79 Ma from lamprophyric dikes within the fold-thrust belt constrain an upper age limit of the ophiolite tectonic emplacement deformation.

  20. Induced Seismicity Potential of Energy Technologies

    NASA Astrophysics Data System (ADS)

    Hitzman, Murray

    2013-03-01

    Earthquakes attributable to human activities-``induced seismic events''-have received heightened public attention in the United States over the past several years. Upon request from the U.S. Congress and the Department of Energy, the National Research Council was asked to assemble a committee of experts to examine the scale, scope, and consequences of seismicity induced during fluid injection and withdrawal associated with geothermal energy development, oil and gas development, and carbon capture and storage (CCS). The committee's report, publicly released in June 2012, indicates that induced seismicity associated with fluid injection or withdrawal is caused in most cases by change in pore fluid pressure and/or change in stress in the subsurface in the presence of faults with specific properties and orientations and a critical state of stress in the rocks. The factor that appears to have the most direct consequence in regard to induced seismicity is the net fluid balance (total balance of fluid introduced into or removed from the subsurface). Energy technology projects that are designed to maintain a balance between the amount of fluid being injected and withdrawn, such as most oil and gas development projects, appear to produce fewer seismic events than projects that do not maintain fluid balance. Major findings from the study include: (1) as presently implemented, the process of hydraulic fracturing for shale gas recovery does not pose a high risk for inducing felt seismic events; (2) injection for disposal of waste water derived from energy technologies does pose some risk for induced seismicity, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation; and (3) CCS, due to the large net volumes of injected fluids suggested for future large-scale carbon storage projects, may have potential for inducing larger seismic events.

  1. Seismic analysis of piping with nonlinear supports

    SciTech Connect

    Barta, D.A.; Huang, S.N.; Severud, L.K.

    1980-01-01

    The modeling and results of nonlinear time-history seismic analyses for three sizes of pipelines restrained by mechanical snubbes are presented. Numerous parametric analyses were conducted to obtain sensitivity information which identifies relative importance of the model and analysis ingredients. Special considerations for modeling the pipe clamps and the mechanical snubbers based on experimental characterization data are discussed. Comparisions are also given of seismic responses, loads and pipe stresses predicted by standard response spectra methods and the nonlinear time-history methods.

  2. Fluid driven torsional dipole seismic source

    DOEpatents

    Hardee, Harry C.

    1991-01-01

    A compressible fluid powered oscillating downhole seismic source device capable of periodically generating uncontaminated horizontally-propagated, shear waves is provided. A compressible fluid generated oscillation is created within the device which imparts an oscillation to a housing when the device is installed in a housing such as the cylinder off an existing downhole tool, thereby a torsional seismic source is established. Horizontal waves are transferred to the surrounding bore hole medium through downhole clamping.

  3. Introduction about Seismic array Laboratory, IGGCAS

    NASA Astrophysics Data System (ADS)

    Ai, Y.; Xu, W.

    2007-12-01

    Seismic Array Laboratory (SAL, IGGCAS) was built up in 2000, whose initiative was to study the earth structures through portable seismic observation and it has been operating for about 7 years till now. Totally, the lab have 272 sets of seismographs, including 152 CMG-3ESP seismometers, 18 CMG-3T seismometers, 2 STS-2 seismometers, 100 domestic seismometers, 172 Reftek recording system and 100 domestic recording system, respectively. The seismographs in IGGCAS are only used for temporary seismic observations and are open to users who aim at seismic observation based research and, in principle, are able to afford instrument rental. For the past seven years, more than 10 scientific research groups have used these seismographs and set up more than 470 portable stations in Chinese mainland. Up to now, IGGCAS has carried out 15 temporary seismic station arrays which are mainly distributed in North and Southwest China. The data collected at these seismic stations are currently managed by the SAL of IGGCAS and some regulations have been set down for data usage. Users who implement seismic observations with the seismographs in IGGCAS have three years priority to use the corresponding seismic data after field operation. Then, those data should be released by the SAL of IGGCAS. Now, parts of the data have been open to public through the website http://www.seislab.cn/data, and currently, only some event data in SAC format are released due to the lack of high-level technicians dealing with data pre- processing and quality control. In the near future, the lab will release more data in multiple formats to facilitate researchers in relative area via internet connection.

  4. Active Seismic Monitoring for Earthquake Forecasting

    NASA Astrophysics Data System (ADS)

    Artamonova, M.; Korneev, V.

    2005-12-01

    Earthquake prediction remains high priority issue for disaster prevention. Study of the M6.0 2004 Parkfield and M7.0 1989 Loma Prieta strike-slip earthquakes on the San Andreas Fault (SAF) reveal seismicity peaks in the surrounding crust several months prior to the main events. Earthquakes directly within the SAF zone were intentionally excluded from the analysis because they manifest stress-release processes rather than stress accumulation. The observed increase in seismicity is interpreted as a signature of the increasing stress level in the surrounding crust, while the peak that occurs several months prior to the main event and the subsequent decrease in seismicity are attributed to damage-induced softening processes. Furthermore, in both cases there is a distinctive zone of low seismic activity that surrounds the epicentral region in the pre-event period. The increase of seismicity in the crust surrounding a potential future event and the development of a low-seismicity epicentral zone can be regarded as promising precursory information that could help signal the arrival of large earthquakes. We modeled the seismicity precursor phenomena using finite-element 2D model capable to replicate non-linear breaking of elastic rock. The distinctive seismicity peak was observed for a model simulating SAF properties at Park field. Such peaks are likely to be a good mid-term precursors allowing to declare alerts several months before earthquakes and pointing on their epicenter regions. The short tern alerts require use of active sources and their proper placement in order to monitor the developments of rock softening processes.

  5. Seismic Safety Of Simple Masonry Buildings

    SciTech Connect

    Guadagnuolo, Mariateresa; Faella, Giuseppe

    2008-07-08

    Several masonry buildings comply with the rules for simple buildings provided by seismic codes. For these buildings explicit safety verifications are not compulsory if specific code rules are fulfilled. In fact it is assumed that their fulfilment ensures a suitable seismic behaviour of buildings and thus adequate safety under earthquakes. Italian and European seismic codes differ in the requirements for simple masonry buildings, mostly concerning the building typology, the building geometry and the acceleration at site. Obviously, a wide percentage of buildings assumed simple by codes should satisfy the numerical safety verification, so that no confusion and uncertainty have to be given rise to designers who must use the codes. This paper aims at evaluating the seismic response of some simple unreinforced masonry buildings that comply with the provisions of the new Italian seismic code. Two-story buildings, having different geometry, are analysed and results from nonlinear static analyses performed by varying the acceleration at site are presented and discussed. Indications on the congruence between code rules and results of numerical analyses performed according to the code itself are supplied and, in this context, the obtained result can provide a contribution for improving the seismic code requirements.

  6. Refined seismic stratigraphy in prograding carbonates

    SciTech Connect

    Pomar, L. )

    1991-03-01

    Complete exposure of the upper Miocene Reef Complex in the sea cliffs of Mallorca (Spain) allows for a more refined interpretation of seismic lines with similar progradational patterns. A 6 km long high-resolution cross section in the direction of reef progradation displays four hierarchical orders of accretional units. Although all these units are of higher order, they all exhibit similar characteristics as a third order depositional sequence and can likewise be interpreted as the result of high order sea-level cycles. The accretional units are composed of lagoonal horizontal beds, reefal sigmoids and gently dipping slope deposits. They are bounded by erosion surfaces at the top and basinwards by their correlative conformities. These architectural patterns are similar to progradational sequences seen on seismic lines. On seismic lines, the progradational pattern often shows the following geometrical details: (1) discontinuous climbing high-energy reflectors, (2) truncation of clinoforms by these high-energy reflectors with seaward dips, (3) transparent areas intercalated between clinoforms. Based on facies distribution in the outcrops of Mallorca the high-energy reflectors are interpreted as sectors where the erosion surfaces truncated the reef wall and are overlain by lagoonal sediments deposited during the following sealevel rise. The more transparent zones seem to correspond with areas of superposition of undifferentiated lagoonal beds. Offlapping geometries can also be detected in highest quality seismic lines. The comparison between seismic and outcrop data provides a more accurate prediction of lithologies, facies distribution, and reservoir properties on seismic profiles.

  7. Experimental seismic investigations for porous media characterization

    NASA Astrophysics Data System (ADS)

    Senechal, P.; Bordes, C.; Barrière, J.; Garambois, S.; Brito, D.

    2009-12-01

    During decades, seismic investigations were based on the hypothesis of elastic media which is generally appropriate for geological imaging. Nevertheless, the necessity to improve non destructive geophysical methods for reservoir characterization implies to take into account the role of pore fluids for the seismic propagation. On the one hand, the water saturation modifies porous media bulk moduli and density and implies strong phase velocity variations. On the other hand, mechanical couplings between solid and fluid phases which can have inertial or viscous origin, generates attenuation and dispersion phenomena. In order to study these phenomena, we develop laboratory experiments for the measurement of seismic propagation in controlled porous media. We choose to work in a broad band [100-10 000 Hz] which includes Biot's frequency by using different seismic source (launched ball, pendulum, piezoelectric spherical source). These investigations are performed on various media from suspension (fresh concrete) to continuous framework (sand). Seismic propagation is recorded by accelerometers, discussed in term of frequency content, velocity analyses, attenuation and dispersion and compared to theoretical models. Moreover, seismoelectric measurements are used to study fluid displacements (filtration) associated to the seismic propagation.

  8. Seismic monitoring of the Yucca Mountain facility

    SciTech Connect

    Garbin, H.D.; Herrington, P.B.; Kromer, R.P.

    1997-08-01

    Questions have arisen regarding the applicability of seismic sensors to detect mining (re-entry) with a tunnel boring machine (TBM). Unlike cut and blast techniques of mining which produce impulsive seismic signals, the TBM produces seismic signals which are of long duration. (There are well established techniques available for detecting and locating the sources of the impulsive signals.) The Yucca Mountain repository offered an opportunity to perform field evaluations of the capabilities of seismic sensors because during much of 1996, mining there was progressing with the use of a TBM. During the mining of the repository`s southern branch, an effort was designed to evaluate whether the TBM could be detected, identified and located using seismic sensors. Three data acquisition stations were established in the Yucca Mountain area to monitor the TBM activity. A ratio of short term average to long term average algorithm was developed for use in signal detection based on the characteristics shown in the time series. For location of the source of detected signals, FK analysis was used on the array data to estimate back azimuths. The back azimuth from the 3 component system was estimated from the horizontal components. Unique features in the timing of the seismic signal were used to identify the source as the TBM.

  9. Experiments on Seismic Metamaterials: Molding Surface Waves

    NASA Astrophysics Data System (ADS)

    Brûlé, S.; Javelaud, E. H.; Enoch, S.; Guenneau, S.

    2014-04-01

    Materials engineered at the micro- and nanometer scales have had a tremendous and lasting impact in photonics and phononics. At much larger scales, natural soils civil engineered at decimeter to meter scales may interact with seismic waves when the global properties of the medium are modified, or alternatively thanks to a seismic metamaterial constituted of a mesh of vertical empty inclusions bored in the initial soil. Here, we show the experimental results of a seismic test carried out using seismic waves generated by a monochromatic vibrocompaction probe. Measurements of the particles' velocities show a modification of the seismic energy distribution in the presence of the metamaterial in agreement with numerical simulations using an approximate plate model. For complex natural materials such as soils, this large-scale experiment was needed to show the practical feasibility of seismic metamaterials and to stress their importance for applications in civil engineering. We anticipate this experiment to be a starting point for smart devices for anthropic and natural vibrations.

  10. Seismic full waveform inversion from compressive measurements

    NASA Astrophysics Data System (ADS)

    Ramirez, Ana; Arce, Gonzalo R.

    2015-05-01

    Traditional methods in seismic acquisition require sources and geophones that are uniformly located along a spatial line, using the Nyquist sampling rate. Depending on the area to be explored, it can be necessary to use seismic surveys with large offsets, or decrease the separation between adjacent geophones to improve the resolution, which generates very high volumes of data. It makes the exploration process more difficult and particularly expensive. This work presents the reconstruction of a compressive set of seismic traces acquired using the compressive sensing paradigm where the pair of sources and geophones are randomly located along the spatial line. The recovery of the wavefield from compressive measurements is feasible due to the capabilities of Curvelets on representing wave propagators with only a small set of coefficients. The method first uses the compressive samples to find a sparse vector representation of each pixel in a 2-D Curvelet dictionary. The sparse vector representation is estimated by solving a sparsity constrained optimization problem using the Gradient Projection for Sparse Reconstruction (GPSR) method. The estimated vector is then used to compute the seismic velocity profiles via acoustic Full Waveform Inversion (FWI). Simulations of the reconstructed image gathers and the resulting seismic velocity profiles illustrate the performance of the method. An improvement in the resulting images is obtained in comparison with traditional F-K filtering used in seismic data processing when traces are missing.

  11. Martian seismicity through time from surface faulting

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Tanaka, Kenneth L.; Banerdt, W. B.; Tralli, D.

    1991-01-01

    An objective of future Mars missions involves emplacing a seismic network on Mars to determine the internal structure of the planet. An argument based on the relative geologic histories of the terrestrial planets suggests that Mars should be seismically more active than the Moon, but less active than the Earth. The seismicity is estimated which is expected on Mars through time from slip on faults visible on the planets surface. These estimates of martian seismicity must be considered a lower limit as only structures produced by shear faulting visible at the surface today are included (i.e., no provision is made for buried structures or non-shear structures); in addition, the estimate does not include seismic events that do not produce surface displacement (e.g., activity associated with hidden faults, deep lithospheric processes or volcanism) or events produced by tidal triggering or meteorite impacts. Calibration of these estimates suggests that Mars may be many times more seismically active than the Moon.

  12. Experiments on seismic metamaterials: molding surface waves.

    PubMed

    Brûlé, S; Javelaud, E H; Enoch, S; Guenneau, S

    2014-04-01

    Materials engineered at the micro- and nanometer scales have had a tremendous and lasting impact in photonics and phononics. At much larger scales, natural soils civil engineered at decimeter to meter scales may interact with seismic waves when the global properties of the medium are modified, or alternatively thanks to a seismic metamaterial constituted of a mesh of vertical empty inclusions bored in the initial soil. Here, we show the experimental results of a seismic test carried out using seismic waves generated by a monochromatic vibrocompaction probe. Measurements of the particles' velocities show a modification of the seismic energy distribution in the presence of the metamaterial in agreement with numerical simulations using an approximate plate model. For complex natural materials such as soils, this large-scale experiment was needed to show the practical feasibility of seismic metamaterials and to stress their importance for applications in civil engineering. We anticipate this experiment to be a starting point for smart devices for anthropic and natural vibrations. PMID:24745420

  13. Field site evaluation for seismic mine detection

    NASA Astrophysics Data System (ADS)

    Martin, James S.; Larson, Gregg D.; Rogers, Peter H.; Scott, Waymond R., Jr.; McCall, George S., II

    2002-11-01

    A system has been developed that uses audio-frequency surface seismic waves for the detection and imaging of buried landmines. The system is based on the measurement of seismic displacements immediately above buried mines using noncontacting vibrometers that interrogate the surface motion with either radar or ultrasonic signals. In laboratory tests and limited field tests the system has demonstrated the ability to detect a variety of inert antipersonnel and antitank mines with background contrast in excess of 20 dB. Current work on the system is focused on the transition from the laboratory into the field. To facilitate this, a series of experiments has been undertaken to measure the characteristics of several field test sites. The tradeoff between image contrast and scanning speed is of primary concern in evaluating the features of these sites. The field experiments have investigated the nature of ambient seismic noise, input impedance at the seismic source (a ground contacting shaker), modal content of the seismic interrogation signal, and the nature of the nonlinearities in the soil. Observed nonlinear phenomena have included harmonic generation, phase speed slowing, dispersion and spall. Although interesting, the differences between the field sites and the laboratory model do not appear to pose problems for seismic mine detection.

  14. The Berkeley Digital Seismic Network

    NASA Astrophysics Data System (ADS)

    Romanowicz, B.; Dreger, D.; Neuhauser, D.; Karavas, W.; Hellweg, M.; Uhrhammer, R.; Lombard, P.; Friday, J.; Lellinger, R.; Gardner, J.; McKenzie, M. R.; Bresloff, C.

    2007-05-01

    Since it began monitoring earthquakes in northern California 120 years ago, the Berkeley Seismological Laboratory (BSL) has been striving to produce the highest quality and most complete seismic data possible in the most modern way. This goal has influenced choices in instrumentation, installation and telemetry, as well as the investment in expertise and manpower. Since the transition to broadband (BB) instrumentation in the mid- 1980s and to a fully digitally telemetered network in the early 1990s, we have continued these efforts. Each of our 25 BB installations includes three component BB seismometers (STS-1s or STS-2) and digital accelerometers to capture the full range of ground motion from distant teleseisms to large, nearby earthquakes (almost 250 dB). The ground motion is recorded on-site by 24 bit dataloggers. Additional environmental parameters, such as temperature and pressure, are also monitored continuously. Many stations record also C-GPS data that is transmitted continuously to the BSL via shared real-time telemetry. The BDSN's first stations were installed in abandoned mines. In the last 15 years, we developed installations using buried shipping containers to reduce environmental noise and provide security and easy access to the equipment. Data are transmitted in real-time at several sampling rates to one or more processing centers, using frame relay, radio, microwave, and/or satellite. Each site has 7-30 days of onsite data storage to guard against data loss during telemetry outages. Each station is supplied with backup batteries to provide power for 3 days. The BDSN real-time data acquisition, earthquake analysis and archiving computers are housed in a building built to "emergency grade" seismic standards, with air conditioning and power backed up by a UPS and a large generator. Data latency and power are monitored by automated processes that alert staff via pager and email. Data completeness and timing quality are automatically assessed on a daily

  15. GSAC - Generic Seismic Application Computing

    NASA Astrophysics Data System (ADS)

    Herrmann, R. B.; Ammon, C. J.; Koper, K. D.

    2004-12-01

    With the success of the IRIS data management center, the use of large data sets in seismological research has become common. Such data sets, and especially the significantly larger data sets expected from EarthScope, present challenges for analysis with existing tools developed over the last 30 years. For much of the community, the primary format for data analysis is the Seismic Analysis Code (SAC) format developed by Lawrence Livermore National Laboratory. Although somewhat restrictive in meta-data storage, the simplicity and stability of the format has established it as an important component of seismological research. Tools for working with SAC files fall into two categories - custom research quality processing codes and shared display - processing tools such as SAC2000, MatSeis,etc., which were developed primarily for the needs of individual seismic research groups. While the current graphics display and platform dependence of SAC2000 may be resolved if the source code is released, the code complexity and the lack of large-data set analysis or even introductory tutorials could preclude code improvements and development of expertise in its use. We believe that there is a place for new, especially open source, tools. The GSAC effort is an approach that focuses on ease of use, computational speed, transportability, rapid addition of new features and openness so that new and advanced students, researchers and instructors can quickly browse and process large data sets. We highlight several approaches toward data processing under this model. gsac - part of the Computer Programs in Seismology 3.30 distribution has much of the functionality of SAC2000 and works on UNIX/LINUX/MacOS-X/Windows (CYGWIN). This is completely programmed in C from scratch, is small, fast, and easy to maintain and extend. It is command line based and is easily included within shell processing scripts. PySAC is a set of Python functions that allow easy access to SAC files and enable efficient

  16. Acoustic and Seismic Modalities for Unattended Ground Sensors

    SciTech Connect

    Elbring, G.J.; Ladd, M.D.; McDonald, T.S.; Sleefe, G.E.

    1999-03-31

    In this paper, we have presented the relative advantages and complementary aspects of acoustic and seismic ground sensors. A detailed description of both acoustic and seismic ground sensing methods has been provided. Acoustic and seismic phenomenology including source mechanisms, propagation paths, attenuation, and sensing have been discussed in detail. The effects of seismo-acoustic and acousto-seismic interactions as well as recommendations for minimizing seismic/acoustic cross talk have been highlighted. We have shown representative acoustic and seismic ground sensor data to illustrate the advantages and complementary aspects of the two modalities. The data illustrate that seismic transducers often respond to acoustic excitation through acousto-seismic coupling. Based on these results, we discussed the implications of this phenomenology on the detection, identification, and localization objectives of unattended ground sensors. We have concluded with a methodology for selecting the preferred modality (acoustic and/or seismic) for a particular application.

  17. Final Report: Seismic Hazard Assessment at the PGDP

    SciTech Connect

    Wang, Zhinmeng

    2007-06-01

    Selecting a level of seismic hazard at the Paducah Gaseous Diffusion Plant for policy considerations and engineering design is not an easy task because it not only depends on seismic hazard, but also on seismic risk and other related environmental, social, and economic issues. Seismic hazard is the main focus. There is no question that there are seismic hazards at the Paducah Gaseous Diffusion Plant because of its proximity to several known seismic zones, particularly the New Madrid Seismic Zone. The issues in estimating seismic hazard are (1) the methods being used and (2) difficulty in characterizing the uncertainties of seismic sources, earthquake occurrence frequencies, and ground-motion attenuation relationships. This report summarizes how input data were derived, which methodologies were used, and what the hazard estimates at the Paducah Gaseous Diffusion Plant are.

  18. GRAIL Refinements to Lunar Seismic Structure

    NASA Technical Reports Server (NTRS)

    Weber, Renee C.; Schmerr, Nicholas C.

    2014-01-01

    Joint interpretation of disparate geophysical datasets helps reduce drawbacks that can result from analyzing them individually. The Apollo seismic network was situated on the lunar nearside surface in a roughly equilateral triangle having sides approximately 1000 km long, with stations 12/14 nearly co-located at one corner. Due to this limited geographical extent, near-surface ray coverage from moonquakes is low, but increases with depth. In comparison, gravity surveys and their resulting gravity anomaly maps have traditionally offered optimal resolution at crustal depths. Gravimetric maps and seismic data sets are therefore well suited to joint inversion, since the complementary information reduces inherent model ambiguity. Previous joint inversions of the Apollo seismic data (seismic phase arrival times) and Clementine- or Lunar Prospector-derived gravity data (mass and moment of inertia) attempted to recover the subsurface structure of the Moon by focusing on hypothetical lunar compositions that explored the density/velocity relationship. These efforts typically searched for the best fitting thermodynamically calculated velocity/density model, and allowed variables like core size, velocity, and/or composition to vary freely. Seismic velocity profiles derived from the Apollo seismic data through travel time inversion vary both in the depth of the crust and mantle layers, and the seismic velocities and densities assigned to those layers. The lunar mass and moment of inertia likewise only constrain gross variations in the density profile beyond that of a uniform density sphere. As a result, composition and structure models previously obtained by jointly inverting these data retain the original uncertainties inherent in the input data sets. We perform a joint inversion of Apollo seismic delay times and gravity data collected by the GRAIL lunar gravity mission, in order to recover seismic velocity and density as a function of latitude, longitude, and depth within the

  19. GRAIL Refinements to Lunar Seismic Structure

    NASA Technical Reports Server (NTRS)

    Weber, Renee C.; Schmerr, Nicholas C.

    2013-01-01

    Joint interpretation of disparate geophysical datasets helps to reduce drawbacks that can result from analyzing them individually. The Apollo seismic network was situated on the lunar nearside surface in a roughly equilateral triangle having sides approximately 1000 km long, with stations 12/14 nearly co-located at one corner. Due to this limited geographical extent, near-surface ray coverage from moonquakes is low, but increases with depth. In comparison, gravity surveys and their resulting gravity anomaly maps have traditionally offered optimal resolution at crustal depths. Gravimetric maps and seismic data sets are therefore well suited to joint inversion, since the complementary information reduces inherent model ambiguity. Previous joint inversions of the Apollo seismic data (seismic phase arrival times) and Clementine- or Lunar Prospector-derived gravity data (mass and moment of inertia) attempted to recover the subsurface structure of the Moon by focusing on hypothetical lunar compositions that explore the density/velocity relationship. These efforts typically search for the best fitting thermodynamically calculated velocity/density model, allowing variables like core size, velocity, and/or composition to vary freely. Seismic velocity profiles previously derived from the Apollo seismic data through inversion of travel times vary both in the depth of the crust and mantle layers, and the seismic velocities and densities assigned to those layers. The lunar mass and moment of inertia likewise only constrain gross variations in the density profile beyond that of a uniform density sphere. As a result, composition and structure models previously obtained by jointly inverting these data retain the original uncertainties inherent in the input data sets. We will perform a joint inversion of Apollo seismic delay times and gravity data collected by the GRAIL lunar gravity mission, in order to recover seismic velocities and density as a function of latitude, longitude

  20. Astor Pass Seismic Surveys Preliminary Report

    SciTech Connect

    Louie, John; Pullammanappallil, Satish; Faulds, James; Eisses, Amy; Kell, Annie; Frary, Roxanna; Kent, Graham

    2011-08-05

    In collaboration with the Pyramid Lake Paiute Tribe (PLPT), the University of Nevada, Reno (UNR) and Optim re-processed, or collected and processed, over 24 miles of 2d seismic-reflection data near the northwest corner of Pyramid Lake, Nevada. The network of 2d land surveys achieved a near-3d density at the Astor Pass geothermal prospect that the PLPT drilled during Nov. 2010 to Feb. 2011. The Bureau of Indian Affairs funded additional seismic work around the Lake, and an extensive, detailed single-channel marine survey producing more than 300 miles of section, imaging more than 120 ft below the Lake bottom. Optim’s land data collection utilized multiple heavy vibrators and recorded over 200 channels live, providing a state-of-the-art reflection-refraction data set. After advanced seismic analysis including first-arrival velocity optimization and prestack depth migration, the 2d sections show clear fault-plane reflections, in some areas as deep as 4000 ft, tying to distinct terminations of the mostly volcanic stratigraphy. Some lines achieved velocity control to 3000 ft depth; all lines show reflections and terminations to 5000 ft depth. Three separate sets of normal faults appear in an initial interpretation of fault reflections and stratigraphic terminations, after loading the data into the OpendTect 3d seismic visualization system. Each preliminary fault set includes a continuous trace more than 3000 ft long, and a swarm of short fault strands. The three preliminary normal-fault sets strike northerly with westward dip, northwesterly with northeast dip, and easterly with north dip. An intersection of all three fault systems documented in the seismic sections at the end of Phase I helped to locate the APS-2 and APS-3 slimholes. The seismic sections do not show the faults connected to the Astor Pass tufa spire, suggesting that we have imaged mostly Tertiary-aged faults. We hypothesize that the Recent, active faults that produced the tufa through hotspring

  1. Ischia Island: Historical Seismicity and Dynamics

    NASA Astrophysics Data System (ADS)

    Carlino, S.; Cubellis, E.; Iannuzzi, R.; Luongo, G.; Obrizzo, F.

    2003-04-01

    The seismic energy release in volcanic areas is a complex process and the island of Ischia provides a significant scenario of historical seismicity. This is characterized by the occurence of earthquakes with low energy and high intensity. Information on the seismicity of the island spans about eight centuries, starting from 1228. With regard to effects, the most recent earthquake of 1883 is extensively documented both in the literature and unpublished sources. The earthquake caused 2333 deaths and the destruction of the historical and environmental heritage of some areas of the island. The most severe damage occurred in Casamicciola. This event, which was the first great catastrophe after the unification of Italy in the 1860s (Imax = XI degree MCS), represents an important date in the prevention of natural disasters, in that it was after this earthquake that the first Seismic Safety Act in Italy was passed by which lower risk zones were identified for new settlements. Thanks to such detailed analysis, reliable modelling of the seismic source was also obtained. The historical data onwards makes it possible to identify the area of the epicenter of all known earthquakes as the northern slope of Monte Epomeo, while analysis of the effects of earthquakes and the geological structures allows us to evaluate the stress fields that generate the earthquakes. In a volcanic area, interpretation of the mechanisms of release and propagation of seismic energy is made even more complex as the stress field that acts at a regional level is compounded by that generated from migration of magmatic masses towards the surface, as well as the rheologic properties of the rocks dependent on the high geothermic gradient. Such structural and dynamic conditions make the island of Ischia a seismic area of considerable interest. It would appear necessary to evaluate the expected damage caused by a new event linked to the renewal of dynamics of the island, where high population density and the

  2. GRAIL Refinements to Lunar Seismic Structure

    NASA Astrophysics Data System (ADS)

    Weber, R. C.; Schmerr, N. C.

    2013-12-01

    Joint interpretation of disparate geophysical datasets helps to reduce drawbacks that can result from analyzing them individually. The Apollo seismic network was situated on the lunar nearside surface in a roughly equilateral triangle having sides approximately 1000 km long, with stations 12/14 nearly co-located at one corner. Due to this limited geographical extent, near-surface ray coverage from moonquakes is low, but increases with depth. In comparison, gravity surveys and their resulting gravity anomaly maps have traditionally offered optimal resolution at crustal depths. Gravimetric maps and seismic data sets are therefore well suited to joint inversion, since the complementary information reduces inherent model ambiguity. Previous joint inversions of the Apollo seismic data (seismic phase arrival times) and Clementine- or Lunar Prospector-derived gravity data (mass and moment of inertia) attempted to recover the subsurface structure of the Moon by focusing on hypothetical lunar compositions that explored the density/velocity relationship. These efforts typically searched for the best fitting thermodynamically calculated velocity/density model, and allowed variables like core size, velocity, and/or composition to vary freely. Seismic velocity profiles previously derived from the Apollo seismic data through inversion of travel times vary both in the depth of the crust and mantle layers, and the seismic velocities and densities assigned to those layers. The lunar mass and moment of inertia likewise only constrain gross variations in the density profile beyond that of a uniform density sphere. As a result, composition and structure models previously obtained by jointly inverting these data retain the original uncertainties inherent in the input data sets. We will perform a joint inversion of Apollo seismic delay times and gravity data collected by the GRAIL lunar gravity mission, in order to recover seismic velocities and density as a function of latitude

  3. Distinguishing induced seismicity from natural seismicity in Ohio: Demonstrating the utility of waveform template matching

    NASA Astrophysics Data System (ADS)

    Skoumal, Robert J.; Brudzinski, Michael R.; Currie, Brian S.

    2015-09-01

    This study investigated the utility of multistation waveform cross correlation to help discern induced seismicity. Template matching was applied to all Ohio earthquakes cataloged since the arrival of nearby EarthScope TA stations in late 2010. Earthquakes that were within 5 km of fluid injection activities in regions that lacked previously documented seismicity were found to be swarmy. Moreover, the larger number of events produced by template matching for these swarmy sequences made it easier to establish more detailed temporal and spatial relationships between the seismicity and fluid injection activities, which is typically required for an earthquake to be considered induced. Study results detected three previously documented induced sequences (Youngstown, Poland Township, and Harrison County) and provided evidence that suggests two additional cases of induced seismicity (Belmont/Guernsey County and Washington County). Evidence for these cases suggested that unusual swarm-like behaviors in regions that lack previously documented seismicity can be used to help distinguish induced seismicity, complementing the traditional identification of an anthropogenic source spatially and temporally correlated with the seismicity. In support of this finding, we identified 17 additional cataloged earthquakes in regions of previously documented seismicity and away from disposal wells or hydraulic fracturing that returned very few template matches. The lack of swarminess helps to indicate that these events are most likely naturally occurring.

  4. A seismic hazard uncertainty analysis for the New Madrid seismic zone

    USGS Publications Warehouse

    Cramer, C.H.

    2001-01-01

    A review of the scientific issues relevant to characterizing earthquake sources in the New Madrid seismic zone has led to the development of a logic tree of possible alternative parameters. A variability analysis, using Monte Carlo sampling of this consensus logic tree, is presented and discussed. The analysis shows that for 2%-exceedence-in-50-year hazard, the best-estimate seismic hazard map is similar to previously published seismic hazard maps for the area. For peak ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 s (0.2 and 1.0 s Sa), the coefficient of variation (COV) representing the knowledge-based uncertainty in seismic hazard can exceed 0.6 over the New Madrid seismic zone and diminishes to about 0.1 away from areas of seismic activity. Sensitivity analyses show that the largest contributor to PGA, 0.2 and 1.0 s Sa seismic hazard variability is the uncertainty in the location of future 1811-1812 New Madrid sized earthquakes. This is followed by the variability due to the choice of ground motion attenuation relation, the magnitude for the 1811-1812 New Madrid earthquakes, and the recurrence interval for M>6.5 events. Seismic hazard is not very sensitive to the variability in seismogenic width and length. Published by Elsevier Science B.V.

  5. MSNoise: a Python Package for Monitoring Seismic Velocity Changes using Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Lecocq, T.; Caudron, C.; Brenguier, F.

    2013-12-01

    Earthquakes occur every day all around the world and are recorded by thousands of seismic stations. In between earthquakes, stations are recording "noise". In the last 10 years, the understanding of this noise and its potential usage have been increasing rapidly. The method, called "seismic interferometry", uses the principle that seismic waves travel between two recorders and are multiple-scattered in the medium. By cross-correlating the two records, one gets an information on the medium below/between the stations. The cross-correlation function (CCF) is a proxy to the Green Function of the medium. Recent developments of the technique have shown those CCF can be used to image the earth at depth (3D seismic tomography) or study the medium changes with time. We present MSNoise, a complete software suite to compute relative seismic velocity changes under a seismic network, using ambient seismic noise. The whole is written in Python, from the monitoring of data archives, to the production of high quality figures. All steps have been optimized to only compute the necessary steps and to use 'job'-based processing. We present a validation of the software on a dataset acquired during the UnderVolc[1] project on the Piton de la Fournaise Volcano, La Réunion Island, France, for which precursory relative changes of seismic velocity are visible for three eruptions betwee 2009 and 2011.

  6. Vibrator for seismic geophysical prospecting

    SciTech Connect

    Bird, J.M.

    1987-04-21

    An improved vibrator system is described for seismic geophysical prospecting, comprising: a vibrator comprising a first part, or dynamic vibrator part (VD) attached to a base plate in contact with the earth and a second part or vibrator stationary part (VS). Sound attenuating ear protection apparatus is described comprising: a pair of air evacuated, sealed chamber members disposably covering the ears of a user to lie between the user eardrums and an ear external source of undesirable sound energy; the air evacuated sealed chamber members each including first and second smooth surface portions with each surface portion having a spherical segment terminated by an annular flange lip shape and being disposable over one external ear of the user with one spherical segment, adjacent the ear being of different, higher mechanical resonance frequency with respect to the other spherical segment distal of the ear; the surface segment distal of the ear; the annular flange lips of the first and second surface portions being joined together in a junction disposed intermediate of the first and second spherical surface portions and perpendicular of the flange lips; resilient suspension m