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Sample records for africa seismic experiment

  1. 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.

  2. Southern Africa seismic structure and source studies

    NASA Astrophysics Data System (ADS)

    Zhao, Ming

    1998-09-01

    The upper mantle seismic velocity structure beneath southern Africa is investigated using travel time and waveform data. Waveform and travel time data used in this study come mainly from a large mine tremor in South Africa (msb{b} 5.6) recorded on stations of the southern Africa and the Tanzania Broadband Seismic Experiment. Auxiliary data along similar profiles are obtained from other moderate events within eastern and southern Africa. The waveform data from the large tremor show upper mantle triplications for both the 400 and 670-km discontinuities between 18sp° and 27sp° distance. The most notable feature of the data is a large, late P phase that propagates to at least 27sp°. This phase is striking because of its late arrival time (as much as 15 seconds after direct P at 27sp°) and high amplitude relative to the first arrival. Travel times from all available stations are used to invert for the P wave velocity structure down to 800 km depth and S wave velocity structure down to 200 km using the Wiechert-Herglotz (W-H) inversion technique. The P wave velocities from the uppermost mantle down to 300 km are as much as 3% higher than the global average and are slightly slower than the global average between 300 and 400 km depths. The velocity gradient between 300 and 400 km is 0.0015 1/s. The S wave travel time data yield fast velocities above 200-km depth. The S wave velocity structure appears inconsistent with the P wave structure model indicating varying Poisson's ratio in the upper mantle. Little evidence is found for a pronounced upper mantle low velocity zone. Both sharp and gradual-change 400-km discontinuities are favored by the waveform data. The 670-km discontinuity appears as a gradual-change zone. The source mechanism of the mb 5.6 mining tremor itself is important for seismic discrimination and insight into mining tremor sources. Source parameters for this event as well as some other large mining tremors from the South African gold mines are studied

  3. Observational study of rock mass response to mining induced seismic events and controlled blasting experiments at deep level gold mines in South Africa

    NASA Astrophysics Data System (ADS)

    Milev, A.; Durrheim, R. J.; Nakatani, M.; Yabe, Y.; Naoi, M. M.; Ogasawara, H.

    2012-12-01

    The strong ground motion generated by mining induced seismic events was studied to characterize the rock mass response and to estimate the site effect on the surface of the underground excavations. A stand-alone instruments, especially designed for recording strong ground motions, were installed underground at a number of deep level gold mines in South Africa. The instruments were recording data at the surface of the stope hangingwalls. A maximum value of 3 m/s was measured. Therefore data were compared to the data recorded in the solid rock by the mine seismic networks to determine the site response. The site response was defined as the ratio of the peak ground velocity measured at the surface of the excavations to the peak ground velocity inferred from the mine seismic data measured in the solid rocks. The site response measured at all mines studied was found to be 9 ± 3 times larger on average. In addition a number of simulated rockbursts were conducted underground in order to estimate the rock mass response when subjected to strong ground motion. The rockbursts were simulated by means of large blasts detonated in solid rock close to the sidewall of a tunnel. The numerical models used in the design of the simulated rockbursts were calibrated by small blasts taking place at each experimental site. A dense array of shock type accelerometers was installed along the blasting wall to monitor the attenuation of the strong ground motion as a function of the distance from the source. The attenuation of peak particle velocity was found to be proportional to R-1.7. In order to improve the understanding of the rock mass behaviour around deep level mining the rate of tilt was monitor and then compare to the seismic ground motion. A good correspondence between the rate of tilt and seismic ground motion was found. The rate of coseismic and aseismic tilt, as well as seismicity recorded by the mine seismic network, are approximately constant until the daily blasting time

  4. Seismic Hazard Implication of the Seismotectonics of southern Africa

    NASA Astrophysics Data System (ADS)

    Midzi, Vunganai; Mulabisana, Thifelimbilu; Manzunzu, Brassnavy

    2014-05-01

    The work presented in this report / presentation was prepared as part of the requirements for the SIDA/IGCP Project 601 titled "Seismotectonics and Seismic Hazards in Africa" as well as part of the seismic source characterisation of the GEM-Africa Seismic hazard study. An effort was made to compile information necessary to prepare a seismotectonic map of Africa which can then be used in carrying out a seismic hazard assessment of the continent or locations within the continent. Information on major faults, fault plane solutions, geophysical data as well as stress data has so far been collected and included in a database for the southern Africa region. Reports published by several experts contributed much to the collected information. The seismicity data used are part of the earthquake catalogue being prepared for the GEM-Africa project, which includes historical and instrumental records as collected from various sources. An effort has been made to characterise the identified major faults and through further analysis investigate their possible impact on the seismic hazard of southern Africa.

  5. The Lithospheric Structure in Southwestern Africa from the Walpass - Walvis Ridge Passive-Source Seismic Experiment. Preliminary Results from Receiver Functions

    NASA Astrophysics Data System (ADS)

    Heit, B.; Yuan, X.; Weber, M. H.; Geissler, W.; Lushetile, B.

    2012-12-01

    The Etendeka continental flood-basalt province in northern Namibia, linked by the Walvis Ridge to the Tristan da Cunha hotspot, has a great importance in global plate tectonic concepts, and is an ideal place to understand the roll of the plume-lithosphere interaction during the break-up of the Southern Atlantic Ocean. Within this frame we are operating an amphibian passive-source seismic network (WALPASS) at the position, where the Walvis Ridge intersects with the continental margin of northern Namibia. The broadband seismic network is composed of 28 three-component land stations and 12 ocean-bottom stations, and will be operating for two year. This configuration of stations will allow us to map the lithospheric and deeper upper mantle structure in the ocean-continent transition beneath the passive continental margin of northern Namibia and to find seismic anomalies related to the postulated hotspot track from the continent to the ocean along the Walvis Ridge. The acquired should help us to study the velocity anomaly in the lowermost mantle caused by the Africa super plume and to improve the distribution of seismicity in this geophysically little studied region. We present here some receiver function results in the first attempt to map the lithosphere and the upper mantle in an area known to be the place of a plume/flood basalt province that has the potential to unravel the impact of a continental break-up in the lower crust and mantle lithosphere. Here we present a preliminary Moho map for the region using P reciever function data.

  6. Strong ground motion generated by controlled blasting experiments and mining induced seismic events recorded underground at deep level mines in South Africa

    NASA Astrophysics Data System (ADS)

    Milev, A.; Selllers, E.; Skorpen, L.; Scheepers, L.; Murphy, S.; Spottiswoode, S. M.

    2011-12-01

    A number of simulated rockbursts were conducted underground at deep level gold mines in South Africa in order to estimate the rock mass response when subjected to strong ground motion. The rockbursts were simulated by means of large blasts detonated in solid rock close to the sidewall of a tunnel. The simulated rockbursts involved the design of the seismic source, seismic observations in the near and far field, high-speed video filming, a study of rock mass conditions such as fractures, joints, rock strength etc. Knowledge of the site conditions before and after the simulated rockbursts was also gained. The numerical models used in the design of the simulated rockbursts were calibrated by small blasts taking place at each experimental site. A dense array of shock type accelerometers was installed along the blasting wall to monitor the attenuation of the strong ground motion as a function of the distance from the source. The attenuation of peak particle velocities, was found to be proportional to R^-1.7. Special investigations were carried out to evaluate the mechanism and the magnitude of damage, as well as the support behaviour under excessive dynamic loading. The strong ground motion generated by mining induced seismic events was studied, as part of this work, not only to characterize the rock mass response, but also to estimate the site effect on the surface of the underground excavations. A stand-alone instrument especially designed for recording strong ground motions was used to create a large database of peak particle velocities measured on stope hangingwalls. A total number of 58 sites located in stopes where the Carbon Leader Reef, Ventersdorp Contact Reef, Vaal Reef and Basal Reef are mined, were monitored. The peak particle velocities were measured at the surface of the excavations to identify the effect of the free surface and the fractures surrounding the underground mining. Based on these measurements the generally accepted velocity criterion of 3 m

  7. AfricaArray: Building science capacity and improving seismic networks in Africa

    NASA Astrophysics Data System (ADS)

    Nyblade, A.; Dirks, P.; Graham, G.

    2007-05-01

    AfricaArray is a long-term initiative to promote coupled training and research programs in geophysics for building and maintaining a scientific workforce for Africa's natural resource sector. The main goals of AfricaArray are to: 1) maintain and develop further geophysical training programs in Africa, in response to industry, government and university needs, 2) promote geophysical research in Africa, and establish an Africa-to-Africa research support system, 3) obtain geophysical data, through a network of shared observatories, to study scientific targets of economic and societal interest, as well as fundamental geological processes shaping the African continent. AfricaArray is supported by a public-private partnership consisting of many government organizations in the US and Africa, and mining and oil companies. AfricaArray has been built on existing programs and expertise within partner institutions and is being implemented in three phases over ten years. During Phase 1 (1/2005 - 12/2007), the educational program at the University of the Witwatersrand is being expanded and improved to provide B.Sc., M.Sc., and Ph.D. degree training in geophysics for students from across Africa. Seismic stations are being installed or upgraded in participating countries to form a network of shared scientific observatories, and technical personnel are being trained to operate and maintain the seismic equipment. Data from the seismic stations are being used for student thesis research projects, and the seismic network is helping to catalyze scientific community building through educational and research collaborations. During subsequent phases (2007-2014), the in-situ education and research program will grow to provide B.Sc., M.Sc. and Ph.D. training for many more African students, the network of shared scientific observatories will be expanded, temporary networks of seismic stations will be installed, sustainable centers of excellence in geophysics will be established at other

  8. Seismic hazard assessment of Sub-Saharan Africa using geodetic strain rate models

    NASA Astrophysics Data System (ADS)

    Poggi, Valerio; Pagani, Marco; Weatherill, Graeme; Garcia, Julio; Durrheim, Raymond J.; Mavonga Tuluka, Georges

    2016-04-01

    The East African Rift System (EARS) is the major active tectonic feature of the Sub-Saharan Africa (SSA) region. Although the seismicity level of such a divergent plate boundary can be described as moderate, several earthquakes have been reported in historical times causing a non-negligible level of damage, albeit mostly due to the high vulnerability of the local buildings and structures. Formulation and enforcement of national seismic codes is therefore an essential future risk mitigation strategy. Nonetheless, a reliable risk assessment cannot be done without the calibration of an updated seismic hazard model for the region. Unfortunately, the major issue in assessing seismic hazard in Sub-Saharan Africa is the lack of basic information needed to construct source and ground motion models. The historical earthquake record is largely incomplete, while instrumental catalogue is complete down to sufficient magnitude only for a relatively short time span. In addition, mapping of seimogenically active faults is still an on-going program. Recent studies have identified major seismogenic lineaments, but there is substantial lack of kinematic information for intermediate-to-small scale tectonic features, information that is essential for the proper calibration of earthquake recurrence models. To compensate this lack of information, we experiment the use of a strain rate model recently developed by Stamps et al. (2015) in the framework of a earthquake hazard and risk project along the EARS supported by USAID and jointly carried out by GEM and AfricaArray. We use the inferred geodetic strain rates to derive estimates of total scalar moment release, subsequently used to constrain earthquake recurrence relationships for both area (as distributed seismicity) and fault source models. The rates obtained indirectly from strain rates and more classically derived from the available seismic catalogues are then compared and combined into a unique mixed earthquake recurrence model

  9. 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.

  10. Middle East, North Africa and Western Eurasia Seismic Research Database

    SciTech Connect

    O'Boyle, J L; Ruppert, S D; Hauk, T F; Dodge, D A; Ganzberger, M D; Ryall, F

    2003-07-14

    The National Nuclear Security Administration (NNSA) Ground-Based Nuclear Explosion Monitoring Research and Engineering (GNEM R&E) Program at Lawrence Livermore National Laboratory (LLNL) has made significant progress populating a comprehensive Seismic Research Database (SRDB) used for deriving seismic calibration parameters for the Middle East, North Africa and Western Eurasia (ME/NA/WE) regions. In addition to an overview of select individual information products, we present an overview of our visualization, integration, validation, and organizational processes. Development of these processes and the LLNL SRDB was necessitated by both the very large amount of data and information involved (over 15 terabytes) and the varied data and research result formats utilized. The LLNL SRDB allows for the collection of raw and contextual seismic data used in research, provides an interface for researchers to access data, provides a framework to store research results and integrate datasets, and supports assembly, integration and dissemination of datasets to the NNSA Knowledge Base (KB). The LLNL SRDB is a flexible and extensible framework consisting of a relational database (RDB), Geographical Information System (GIS), and associated product/data visualization and data management tools. This framework is designed to accommodate large volumes of data in diverse formats from many sources (both in-house-derived research and integrated contractor products), in addition to maintaining detailed quality control and metadata. In order to efficiently organize information within the LLNL SRDB, it was necessary to automate procedures needed to create and update database tables, but a large effort is still required by technicians and scientists to load special datasets, review results of automated processing and resolve quality issues. The LLNL SRDB currently has 3 million reconciled event origins and arrivals from several global, regional and local seismic bulletins and 30 million

  11. Experiments on seismic metamaterials: molding surface waves.

    PubMed

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

    2014-04-04

    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.

  12. 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.

  13. Permafrost Active Layer Seismic Interferometry Experiment (PALSIE).

    SciTech Connect

    Abbott, Robert; Knox, Hunter Anne; James, Stephanie; Lee, Rebekah; Cole, Chris

    2016-01-01

    We present findings from a novel field experiment conducted at Poker Flat Research Range in Fairbanks, Alaska that was designed to monitor changes in active layer thickness in real time. Results are derived primarily from seismic data streaming from seven Nanometric Trillium Posthole seismometers directly buried in the upper section of the permafrost. The data were evaluated using two analysis methods: Horizontal to Vertical Spectral Ratio (HVSR) and ambient noise seismic interferometry. Results from the HVSR conclusively illustrated the method's effectiveness at determining the active layer's thickness with a single station. Investigations with the multi-station method (ambient noise seismic interferometry) are continuing at the University of Florida and have not yet conclusively determined active layer thickness changes. Further work continues with the Bureau of Land Management (BLM) to determine if the ground based measurements can constrain satellite imagery, which provide measurements on a much larger spatial scale.

  14. Lunar seismic profiling experiment natural activity study

    NASA Technical Reports Server (NTRS)

    Duennebier, F. K.

    1976-01-01

    The Lunar Seismic Experiment Natural Activity Study has provided a unique opportunity to study the high frequency (4-20 Hz) portion to the seismic spectrum on the moon. The data obtained from the LSPE was studied to evaluate the origin and importance of the process that generates thermal moonquakes and the characteristics of the seismic scattering zone at the lunar surface. The detection of thermal moonquakes by the LSPE array made it possible to locate the sources of many events and determine that they are definitely not generated by astronaut activities but are the result of a natural process on the moon. The propagation of seismic waves in the near-surface layers was studied in a qualitative manner. In the absence of an adequate theoretical model for the propagation of seismic waves in the moon, it is not possible to assign a depth for the scattering layer. The LSPE data does define several parameters which must be satisfied by any model developed in the future.

  15. The SEIS Experiment: A Mars Seismic Package

    NASA Technical Reports Server (NTRS)

    Schibler, P.; Lognonne, P.; Giardini, D.; Banerdt, B.; Karczewski, J. F.; Mimoun, D.; Zweifel, P.; Pike, T.; Ammann, J.; Anglade, A.

    2003-01-01

    This experiment will integrate a VBB (Very Broad Band) two axis seismometer, a three axis Short Period seismometer and a series of environmental sensors for pressure, infra-sounds and temperature. IPGP (France) has the overall responsibility of the experiment and is responsible for the VBB and environmental sensors. ETHZ (Switzerland) is responsible for the electronics of the experiment and JPL (USA) for the SP (Short Period) sensors. SEIS instrument was first proposed and accepted for NetLander mission (and will also be in charge of data acquisition for SPICE experiment). This seismic package should also be proposed for future missions.

  16. Deployment of the Oklahoma borehole seismic experiment

    SciTech Connect

    Harben, P.E.; Rock, D.W.

    1989-01-20

    This paper discusses the Oklahoma borehole seismic experiment, currently in operation, set up by members of the Lawrence Livermore National Laboratory Treaty Verification Program and the Oklahoma Geophysical Observatory to determine deep-borehole seismic characteristics in geology typical of large regions in the Soviet Union. We evaluated and logged an existing 772-m deep borehole on the Observatory site by running caliper, cement bonding, casing inspection, and hole-deviation logs. Two Teledyne Geotech borehole-clamping seismometers were placed at various depths and spacings in the deep borehole. Currently, they are deployed at 727 and 730 m. A Teledyne Geotech shallow-borehole seismometer was mounted in a 4.5-m hole, one meter from the deep borehole. The seismometers' system coherency were tested and found to be excellent to 35 Hz. We have recorded seismic noise, quarry blasts, regional earthquakes and teleseisms in the present configuration. We will begin a study of seismic noise and attenuation as a function of depth in the near future. 7 refs., 18 figs.

  17. Preliminary maps of crustal thickness and regional seismic phases for the Middle East and North Africa

    SciTech Connect

    Sweeney, J.J.

    1995-09-06

    As part of the development of regional seismic discrimination methods for the Middle East and North Africa (MENA) the author is building a database of information related to seismic propagation and crustal structure as well as associated geologic-tectonic and geophysical data. He hopes to use these data to construct and test models of regional seismic propagation and evaluate various detection/discrimination scenarios. To date, the database has been developed by building on a list of references for MENA provided by the Institute for the Study of the Continents (INSTOC) at Cornell University. To this list the author has added an equal number of references resulting from his own literature search which has emphasized papers dealing with seismicity and regional and teleseismic phase data. This paper represents an initial attempt to consolidate some of the information from the database into a form useful to researchers modeling regional seismic waveforms. The information compiled in this report is supplemental to the INSTOC database and has not been compiled anywhere else. What follows is a series of maps which illustrate the spatial variation of seismic phase velocities and crustal thickness. The text identifies the sources of information used in the map preparation. Data for the compilation of these maps has come from an initial search of the database as it presently exists and is not intended to be exhaustive. The author hopes that this initial exercise will help to identify areas and types of data that are deficient and help to focus future data gathering activities.

  18. The LaBarge Passive Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Leahy, G. M.; Schmedes, J.; Saltzer, R. L.; Roth, J. B.

    2011-12-01

    Accurate large-scale seismic velocity models provide critical support for subsurface imaging, particularly for migration and inversion. However, conventional seismic sources typically do not provide significant information below 5-10Hz. Further, alternative methods to obtain a reference velocity model such as normal move-out analysis may be ambiguous or misleading in complicated tectonic settings like fold-and-thrust belts. To address these challenges, we investigated the potential of using naturally occurring earthquakes to obtain a seismic velocity model for shallow sediment structure (above 5 km). Passive seismic data were continuously recorded at 55 stations in LaBarge, Wy for six months in early 2009. We employed two widely used techniques, relative travel-time tomography and teleseismic receiver functions, more commonly used to image deep crustal and mantle structure. The resulting structural image and velocity model compares favorably with local well control, suggesting seismic models obtained by this method would provide viable support for imaging and inversions.

  19. Crust and Upper Mantle of North Africa Using Libyan Seismic Data

    NASA Astrophysics Data System (ADS)

    Pasyanos, M. E.; Eshwehdi, A.

    2005-12-01

    We investigate the crust and upper mantle structure of North Africa using Libyan seismic data. Libya sits at the transition between the relatively aseismic continental crust of the African plate and the seismically active oceanic crust under the Mediterranean Sea which is subducting under the Eurasian Plate along the Calabrian, Hellenic, and Cyprean Arcs. The country also encompasses the Sirte Basin to the north and the smaller Murzuk and Kufra basins in the south. Broadband data from several seismic stations in Libya provide an opportunity for studying the velocity structure of the region. We have made some preliminary dispersion measurements from these stations and have found notable improvements in the group velocity tomography model by incorporating the additional measurements. We will be adding to this analysis by making dispersion measurements from regional events and receiver functions for teleseismic events. Recently, we have been employing methods to jointly invert both surface wave dispersion data and teleseismic receiver functions. The technique holds great promise in accurately estimating seismic structure, including important tectonic parameters such as basin thickness, crustal thickness, upper mantle velocity, as well as more detail about the upper mantle (lithospheric thickness and presence of anisotropy). We propose to apply this method to data from several Libyan stations where we can and, in the absence of receiver functions, invert the dispersion data only. The technique holds the promise of improving our understanding of the crust and upper mantle in Libya and how it fits into the larger tectonic picture of North Africa.

  20. Seismic anisotropy and mantle fabrics beneath eastern Africa and Arabia

    NASA Astrophysics Data System (ADS)

    Elsheikh, A. A.; Gao, S. S.; Liu, K. H.

    2013-12-01

    In spite of numerous studies, the mechanisms for the rifting, uplifting, and volcanism on the African plate remain enigmatic. The most popular hypotheses proposed to explain these tectonic phenomena involve edge-driven small-scale mantle convection and the thermal or dynamic effects of one or more mantle plumes. In particular, several recent models suggested that the rise of the African plateaus and western Arabia was due to the dynamic upwelling of an active mantle plume located beneath southern Africa, despite of the fact that most studies revealed that the mantle transition zone beneath southern Africa has a normal temperature. In this study we use continental scale shear-wave splitting measurements to provide additional constraints on the various models of rifting and uplifting of the African plate. The splitting of P-to-S converted phases at the core-mantle boundary on the receiver side (XKS including PKS, SKKS, and SKS) is one of the most effective approaches to image mantle flow, and to constrain convective mantle flow patterns. Most of the previous shear-wave splitting (SWS) studies in eastern Africa and Arabia assumed a single anisotropic layer as the source of the observed shear-wave splitting. Some studies attributed the observed anisotropy to Precambrian lithospheric fabric developed during compressional orogenic events, while others emphasized the role of mantle flow. Almost all of these studies focused on restricted geographic regions or used a limited number of stations, which led to results applicable to localized areas rather than a continent-wide scale. In addition, the results were presented as station-averages, which prevent the identification of complex anisotropy. This presentation reports preliminary results from an ongoing study using all the broadband XKS data available at the IRIS Data Management Center. The data set was recorded by more than 200 stations in east Africa and Arabia. We are in the process to produce a uniform SWS database

  1. The Northern Walker Lane Seismic Refraction Experiment

    NASA Astrophysics Data System (ADS)

    Louie, J. N.; Smith, S. B.; Thelen, W.; Scott, J. B.; Clark, M.

    2002-12-01

    We are developing a three-dimensional reference seismic velocity model for the western Great Basin region of Nevada and eastern California. The northern Walker Lane had not been characterized well by previous work. In May 2002 we collected a new crustal refraction profile from Battle Mountain, Nev. across western Nevada, the Reno area, Lake Tahoe, and the northern Sierra to Auburn, Calif. Mine blasts and earthquakes were recorded by 199 Texan instruments (loaned by the PASSCAL Instrument Center) extending across this more than 450-km-long transect. The seismic sources at the eastern end were mining blasts at Barrick's GoldStrike pit. We recorded additional blasts at the Florida Canyon and other mines between Lovelock and Battle Mountain, Nevada. The GoldStrike mine produced several ripple-fired blasts using 10,000-40,000 kg of ANFO each. First arrivals from the larger blasts are obvious to distances exceeding 250 km in the raw records. A M2.4 earthquake near Bridgeport, Calif. also produced pickable P-wave arrivals across at least half the transect, providing fan-shot data. We recorded only during working hours, and so missed an M4 earthquake that occurred at night. Events of M2 occurred during our recording to the west on the San Andreas fault near Pinnacles, Calif.; M3 events occurred near Portola and Mammoth Lakes, Calif. Arrivals from M5 events in the Mariana and Kuril Islands also appear in the records. Time-picks from these earthquakes may be possible after more work on synthetic-time modeling, data filtering, and display. We plan to record blasts at quarries in the western Sierra in future experiments, for a direct refraction reversal. We will compare our time picks against times generated from regional velocity models, to identify potential crustal and upper-mantle velocity anomalies. Such anomalies may be associated with the Battle Mountain heat-flow high, the northern Walker Lane belt, or the northern Sierran block.

  2. Shallow lunar structure determined from the passive seismic experiment

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Data relevant to the shallow structure of the moon obtained at the Apollo seismic stations are compared with previously published results of the active seismic experiments. It is concluded that the lunar surface is covered by a layer of low seismic velocity which appears to be equivalent to the lunar regolith defined previously by geological observations. This layer is underlain by a zone of distinctly higher seismic velocity at all of the Apollo landing sites. The regolith thicknesses at the Apollo 11, 12, and 15 sites are estimated from the shear-wave resonance to be 4.4, 3.7, and 4.4 m, respectively. These thicknesses and those determined at the other Apollo sites by the active seismic experiments appear to be correlated with the age determinations and the abundances of extralunar components at the sites.

  3. 2013 East Bay Seismic Experiment (EBSE): implosion data, Hayward, Calif

    USGS Publications Warehouse

    Catchings, Rufus D.; Strayer, Luther M.; Goldman, Mark R.; Criley, Coyn J.; Garcia, Susan; Sickler, Robert R.; Catchings, Marisol K.; Chan, Joanne; Gordon, Leslie C.; Haefner, Scott; Blair, James Luke; Gandhok, Gini; Johnson, Michaela R.

    2015-01-01

    In August 2013, the California State University, East Bay (CSUEB) in Hayward, California imploded a 13-story building (Warren Hall) that was deemed unsafe because of its immediate proximity to the active trace of the Hayward Fault. The U.S. Geological Survey (USGS) and the CSUEB collaborated on a program to record the seismic waves generated by the collapse of the building. We refer to this collaboration as the East Bay Seismic Experiment (EBSE). The principal objective of recording the seismic energy was to observe ground shaking as it radiated from the source, but the data also may be useful for other purposes. For example, the seismic data may be useful in evaluating the implosion process as it relates to structural engineering purposes. This report provides the metadata needed to utilize the seismic data.

  4. Mammoth Mountain, California broadband seismic experiment

    NASA Astrophysics Data System (ADS)

    Dawson, P. B.; Pitt, A. M.; Wilkinson, S. K.; Chouet, B. A.; Hill, D. P.; Mangan, M.; Prejean, S. G.; Read, C.; Shelly, D. R.

    2013-12-01

    Mammoth Mountain is a young cumulo-volcano located on the southwest rim of Long Valley caldera, California. Current volcanic processes beneath Mammoth Mountain are manifested in a wide range of seismic signals, including swarms of shallow volcano-tectonic earthquakes, upper and mid-crustal long-period earthquakes, swarms of brittle-failure earthquakes in the lower crust, and shallow (3-km depth) very-long-period earthquakes. Diffuse emissions of C02 began after a magmatic dike injection beneath the volcano in 1989, and continue to present time. These indications of volcanic unrest drive an extensive monitoring effort of the volcano by the USGS Volcano Hazards Program. As part of this effort, eleven broadband seismometers were deployed on Mammoth Mountain in November 2011. This temporary deployment is expected to run through the fall of 2013. These stations supplement the local short-period and broadband seismic stations of the Northern California Seismic Network (NCSN) and provide a combined network of eighteen broadband stations operating within 4 km of the summit of Mammoth Mountain. Data from the temporary stations are not available in real-time, requiring the merging of the data from the temporary and permanent networks, timing of phases, and relocation of seismic events to be accomplished outside of the standard NCSN processing scheme. The timing of phases is accomplished through an interactive Java-based phase-picking routine, and the relocation of seismicity is achieved using the probabilistic non-linear software package NonLinLoc, distributed under the GNU General Public License by Alomax Scientific. Several swarms of shallow volcano-tectonic earthquakes, spasmodic bursts of high-frequency earthquakes, a few long-period events located within or below the edifice of Mammoth Mountain and numerous mid-crustal long-period events have been recorded by the network. To date, about 900 of the ~2400 events occurring beneath Mammoth Mountain since November 2011 have

  5. Seismic Migration Imaging of the Lithosphere beneath the Afar Rift System, East Africa

    NASA Astrophysics Data System (ADS)

    Lee, T. T. Y.; Chen, C. W.; Rychert, C.; Harmon, N.

    2015-12-01

    The Afar Rift system in east Africa is an ideal natural laboratory for investigating the incipient continental rifting, an essential component of plate tectonics. The Afar Rift is situated at the triple junction of three rifts, namely the southern Red Sea Rift, Gulf of Aden Rift and Main Ethiopian Rift (MER). The ongoing continental rifting at Afar transitions to seafloor spreading toward the southern Red Sea. The tectonic evolution of Afar is thought to be influenced by a mantle plume, but how the plume affects and interacts with the Afar lithosphere remains elusive. In this study, we use array seismic data to produce high-resolution migration images of the Afar lithosphere from scattered teleseismic wavefields to shed light on the lithospheric structure and associated tectonic processes. Our preliminary results indicate the presence of lithospheric seismic discontinuities with depth variation across the Afar region. Beneath the MER axis, we detect a pronounced discontinuity at 55 km depth, characterized by downward fast-to-slow velocity contrast, which appears to abruptly deepen to 75 km depth to the northern flank of MER. This discontinuity may be interpreted as the lithosphere-asthenosphere boundary. Beneath the Ethiopian Plateau, on the other hand, a dipping structure with velocity increase is identified at 70-90 km depth. Further synthesis of observations from seismic tomography, receiver functions, and seismic anisotropy in the Afar region will offer better understanding of tectonic significance of the lithospheric discontinuities.

  6. Seismicity and neotectonic uplift in the Augrabies Falls National Park, Namaqualand, Northern Cape, South Africa

    NASA Astrophysics Data System (ADS)

    Madi, Kakaba

    2016-10-01

    Gneissic rocks in the Augrabies Falls National Park are part of the Proterozoic Namaqua-Natal mobile belt. Finding neotectonic evidence in old terranes is always not an easy task. In South Africa, the mid-Miocene is believed to be the beginning of neotectonics. This study investigated the occurrence and recurrence of earthquake activity, occurrence of faulting, jointing, uplift, and potholes in the gneisses cropping out around the Augrabies Falls area that may account for neotectonics. A historic seismic event obtained from the United States Geological Survey (USGS), and seismic epicenters downloaded in October 2015 from IRIS earthquake browser and overlaid on a satellite image with digitised faults and lineaments, indicates that the area is seismically active and is a zone of seismic risk. Potholes occurring today on a dry surface at approximately 613 m above sea level are a direct consequence of the Griqualand-Transvaal neotectonic uplift, which generated a major fault along which water flows continuously. It is concluded that the Augrabies Falls National Park area is a zone of neotectonics. This zone should not be considered for the storage of nuclear wastes.

  7. The Mars SEIS Experiment: A Mars Seismic Package

    NASA Technical Reports Server (NTRS)

    Mimoun, D.; Lognonne, P.; Banerdt, W. B.; Schibler, P.; Giardini, D.; Pont, G.

    2005-01-01

    The Mars SEIS experiment. The SEIS experiment was first proposed by IPGP (and accepted) for the NetLander mission. It integrates two VBB (Very Broad Band) seismometers, a three axis Short Period seismometer and a series of environmental sensors for pressure, infra-sounds and temperature. IPGP (France) has the overall responsibility of the experiment and is responsible for the seismic and environmental sensors. ETHZ (Switzerland) is responsible for the electronics of the experiment and JPL (USA) for the SP (Short Period) sensors. As NetLander mission has been cancelled (while fortunately the development still goes on), this seismic package can be proposed for future Mars missions.

  8. Northern Cascadia Seismicity From Ocean Floor Observations -- Campaign and Permanent Seismic Experiments

    NASA Astrophysics Data System (ADS)

    Heesemann, M.; Scherwath, M.; Kodaira, S.; Obana, K.; Yamamoto, Y.; Spence, G.; Riedel, M.; Rogers, G. C.; Wang, K.; McGuire, J. J.

    2013-12-01

    Continuous seismic monitoring of offshore seismicity is a challenge. Land-based networks can only detect the larger offshore earthquakes but the estimation of low-magnitude regional or local offshore seismicity requires ocean bottom seismometers (OBSs). At the Cascadia margin these challenges have been addressed with both campaign based as well as seafloor cabled OBS monitoring. The most recent campaigns in Cascadia have been the regional (70-km OBS spacing) U.S. Cascadia Initiative and the local (20-km OBS spacing) Seafloor Earthquake Array Japan-Canada Cascadia Experiment (SeaJade) offshore Vancouver Island. In addition, the Cascadia margin has two regional seafloor cabled observatories: NEPTUNE Canada from Ocean Networks Canada (ONC) and the Regional Scale Nodes (RSN) of the U.S. Ocean Observatories Initiative (OOI), both with OBS spacings of 50-100 km. We show results from the SeaJade experiment from 2010 which had the densest available station spacing. Except for the Nootka fault zone in the north, the observed seismicity was relatively low which is consistent with a fully locked megathrust. We compare the seismic data from the dense SeaJade array with the broader spaced NEPTUNE cabled data and speculate if it would be possible to detect a change in seismicity with NEPTUNE and land stations only or if a higher density of permanent seafloor stations like the 15-20 km spacing of the Japanese DONET cabled observatories is required.

  9. Results from the Apollo passive seismic experiment

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    Recent results from the Apollo Seismic Network suggest that primitive differentiation occurred in the outer shell of the moon to a depth of approximately 300 km and the central region of the moon is presently molten to a radius of between 200 and 300 km. If early melting to a depth of 300 to 400 km was a consequence of accretional energy, very short accretion times are required. It was shown that the best model for the zone of original differentiation is a crust 40 to 80 km thick, ranging in composition from anorthositic gabbro to gabbro, and overlying an ultramafic cumulate about 250 km thick. The best candidate for the molten core appears to be iron or iron sulphide. A new class of seismic signals recently were identified that may correspond to shallow moonquakes. These are rare, but much more energetic than the more numerous, deep moonquakes.

  10. Participation in the Apollo passive seismic experiment

    NASA Technical Reports Server (NTRS)

    Press, F.; Toksoez, M. N.; Dainty, A.

    1972-01-01

    Computer programs which were written to read digital tapes containing lunar seismic data were studied. Interpreting very early parts of the lunar seismogram as seismic body-wave phases enabled the determination of the structure of the outer part of the moon in the Fra Mauro region. The crust in the Fra Mauro region is 60 to 65 km-thick, overlaying a high velocity mantle. The crust is further divided into an upper part, 25 km thick, apparently made of material similar to the surficial basalts, and a lower part of seemingly different composition, possibly an anorthositic gabbro. The generation of the exceedingly long reverberating wave-train observed in lunar seismogram was also studied. This is believed to be due to an intense scattering layer with very high quality coefficient overlying a more homogeneous elastic medium. Titles and abstracts of related published papers are included.

  11. Results from the Apollo passive seismic experiment

    NASA Technical Reports Server (NTRS)

    Lathum, G.; Nakamura, Y.; Dorman, J.; Duennebier, F.; Ewing, M.; Lammlein, D.

    1974-01-01

    Recent results from the Apollo seismic network suggest that primitive differentiation occurred in the outer shell of the moon to a depth of approximately 300 km; and the central region of the moon is presently molten to a radius of between 200 and 300 km. If early melting to a depth of 300 to 400 km was a consequence of accretional energy, very short accretion times are required. The best model for the zone of original differentiation appears to be a crust 40 to 80 km thick, ranging in composition from anorthositic gabbro to gabbro; overlying an ultramafic cumulate (olivine-pyroxene) about 250 km thick. The best candidate for the molten core appears to be iron or iron sulphide. A new class of seismic signals has recently been identified that may correspond to shallow moonquakes. These are rare, but much more energetic than the more numerous, deep moonquakes.

  12. The Lusi seismic experiment: An initial study to understand the effect of seismic activity to Lusi

    SciTech Connect

    Karyono; Mazzini, Adriano; Sugiharto, Anton; Lupi, Matteo; Syafri, Ildrem; Masturyono,; Rudiyanto, Ariska; Pranata, Bayu; Muzli,; Widodo, Handi Sulistyo; Sudrajat, Ajat

    2015-04-24

    The spectacular Lumpur Sidoarjo (Lusi) eruption started in northeast Java on the 29 of May 2006 following a M6.3 earthquake striking the island [1,2]. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system [3] and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. The Lusi seismic experiment is a project aims to begin a detailed study of seismicity around the Lusi area. In this initial phase we deploy 30 seismometers strategically distributed in the area around Lusi and along the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. The purpose of the initial monitoring is to conduct a preliminary seismic campaign aiming to identify the occurrence and the location of local seismic events in east Java particularly beneath Lusi.This network will locate small event that may not be captured by the existing BMKG network. It will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-AW region and spatial and temporal variations of vp/vs ratios. The goal of this study is to understand how the seismicity occurring along the Sunda subduction zone affects to the behavior of the Lusi eruption. Our study will also provide a large dataset for a qualitative analysis of earthquake triggering studies, earthquake-volcano and earthquake-earthquake interactions. In this study, we will extract Green’s functions from ambient seismic noise data in order to image the shallow subsurface structure beneath LUSI area. The waveform cross-correlation technique will be apply to all of recordings of ambient seismic noise at 30 seismographic stations around the LUSI area. We use the dispersive behaviour of the retrieved Rayleigh waves to infer velocity structures in the shallow subsurface.

  13. The Lusi seismic experiment: An initial study to understand the effect of seismic activity to Lusi

    NASA Astrophysics Data System (ADS)

    Karyono, Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Masturyono, Rudiyanto, Ariska; Pranata, Bayu; Muzli, Widodo, Handi Sulistyo; Sudrajat, Ajat; Sugiharto, Anton

    2015-04-01

    The spectacular Lumpur Sidoarjo (Lusi) eruption started in northeast Java on the 29 of May 2006 following a M6.3 earthquake striking the island [1,2]. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system [3] and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. The Lusi seismic experiment is a project aims to begin a detailed study of seismicity around the Lusi area. In this initial phase we deploy 30 seismometers strategically distributed in the area around Lusi and along the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. The purpose of the initial monitoring is to conduct a preliminary seismic campaign aiming to identify the occurrence and the location of local seismic events in east Java particularly beneath Lusi.This network will locate small event that may not be captured by the existing BMKG network. It will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-AW region and spatial and temporal variations of vp/vs ratios. The goal of this study is to understand how the seismicity occurring along the Sunda subduction zone affects to the behavior of the Lusi eruption. Our study will also provide a large dataset for a qualitative analysis of earthquake triggering studies, earthquake-volcano and earthquake-earthquake interactions. In this study, we will extract Green's functions from ambient seismic noise data in order to image the shallow subsurface structure beneath LUSI area. The waveform cross-correlation technique will be apply to all of recordings of ambient seismic noise at 30 seismographic stations around the LUSI area. We use the dispersive behaviour of the retrieved Rayleigh waves to infer velocity structures in the shallow subsurface.

  14. The MARINER Integrated Seismic and Geophysical Mapping Experiment (Invited)

    NASA Astrophysics Data System (ADS)

    Dunn, R. A.; Canales, J.; Sohn, R. A.; Paulatto, M.; Arai, R.; Szitkar, F.

    2013-12-01

    The MARINER (Mid-Atlantic Ridge INtegrated Experiments at Rainbow) seismic and geophysical mapping experiment was designed to examine the relationship between tectonic rifting, heat/melt supply, and oceanic core complex formation at a non-transform offset (NTO) of the Mid-Atlantic Ridge, 36°N, the site of the ultramafic-hosted Rainbow hydrothermal system. We present an overview of the components of the experiment and the various projects stemming from it. The 5-week experiment was carried out aboard the R/V M. G. Langseth in April-May 2013, and consisted of a 3D active-source seismic tomography experiment, 2D multi-channel seismic profiles, an on-going nine month passive micro-seismicity study, dense acoustic mapping of the seafloor (including depth and amplitude information), gravity field mapping, and magnetic field mapping. During the tomography experiment, we deployed 46 ocean bottom seismometers (OBS) over a 35 x 80 sq. km area centered on Rainbow. Twenty-six wide-angle seismic lines were carried out using the Langseth's 36-element source, generating ~175,000 seismic records. The MCS experiment, which was also recorded on 20 OBS, consisted of twenty-one densely spaced seismic lines using an 8-km-long hydrophone streamer. Bathymetry, gravity, and magnetic surveys were carried out over a broader, 80x105 sq. km, area centered on Rainbow. Overall, the experiment extends across two segments of the Mid-Atlantic Ridge separated by the Rainbow NTO massif. MARINER multi-beam bathymetry and acoustic imagery provide a broad view of the geologic and geophysical character of the ridge system, emphasizing the strong variability of ridge morphology, tectonics, and lava emplacement. The magnetization map shows a clear central anomaly with normal polarity, flanked by regions of negative polarity, consistent with the Brunhes-Matuyama reversal (~780,000 Ma). Rainbow itself lies in a region of weaker magnetization strength, which could be linked to a decrease in the depth of the

  15. Bighorns Arch Seismic Experiment (BASE): Amplitude Response to Different Seismic Charge Configurations

    SciTech Connect

    Harder, S. H., Killer, K. C., Worthington, L. L., Snelson, C. M.

    2010-09-02

    Contrary to popular belief, charge weight is not the most important engineering parameter determining the seismic amplitudes generated by a shot. The scientific literature has long claimed that the relationship, A ~R2L1/2, where A is the seismic amplitude generated by a shot, R is the radius of the seismic charge and L is the length of that charge, holds. Assuming the coupling to the formation and the pressure generated by the explosive are constants, this relationship implies that the one should be able to increase the charge radius while decreasing the charge length and obtain more seismic amplitude with less charge weight. This has significant implications for the economics of lithospheric seismic shots, because shallower holes and small charge sizes decrease cost. During the Bighorns Array Seismic Experiment (BASE) conducted in the summer of 2010, 24 shots with charge sizes ranging from 110 to 900 kg and drill hole diameters of 300 and 450 mm were detonated and recorded by an array of up to 2000 single-channel Texan seismographs. Maximum source-receiver offset of 300 km. Five of these shots were located within a one-acre square in an effort to eliminate coupling effects due to differing geological formations. We present a quantitative comparison of the data from these five shots to experimentally test the equation above.

  16. Small Arrays for Seismic Intruder Detections: A Simulation Based Experiment

    NASA Astrophysics Data System (ADS)

    Pitarka, A.

    2014-12-01

    Seismic sensors such as geophones and fiber optic have been increasingly recognized as promising technologies for intelligence surveillance, including intruder detection and perimeter defense systems. Geophone arrays have the capability to provide cost effective intruder detection in protecting assets with large perimeters. A seismic intruder detection system uses one or multiple arrays of geophones design to record seismic signals from footsteps and ground vehicles. Using a series of real-time signal processing algorithms the system detects, classify and monitors the intruder's movement. We have carried out numerical experiments to demonstrate the capability of a seismic array to detect moving targets that generate seismic signals. The seismic source is modeled as a vertical force acting on the ground that generates continuous impulsive seismic signals with different predominant frequencies. Frequency-wave number analysis of the synthetic array data was used to demonstrate the array's capability at accurately determining intruder's movement direction. The performance of the array was also analyzed in detecting two or more objects moving at the same time. One of the drawbacks of using a single array system is its inefficiency at detecting seismic signals deflected by large underground objects. We will show simulation results of the effect of an underground concrete block at shielding the seismic signal coming from an intruder. Based on simulations we found that multiple small arrays can greatly improve the system's detection capability in the presence of underground structures. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

  17. Third Party Borehole Seismic Experiments During the Ocean Drilling Program

    NASA Astrophysics Data System (ADS)

    Swift, S. A.; Stephen, R. A.; Hoskins, H.; Bolmer, T.

    2003-12-01

    Third party borehole seismic experiments on the Ocean Drilling Program began with an oblique seismic experiment on Leg 102 at Site 418 in the Western Atlantic. Upper ocean crust here is characterized by a normal seismic layer 2 vertical velocity gradient, lateral velocity variations, azimuthal anisotropy, and azimuth dependent scattering. A normal incidence VSP was run on Leg 118 in the gabbro sequence at Hole 735B on the Southwest Indian Ridge. The vertical seismic velocity inferred from arrival times is similar to that observed horizontally by refraction in ocean layer 3, but attenuation is anomalously high, which prompted the hypothesis that the gabbro cored may not actually represent the bulk of Layer 3 material. The VSP data acquired at Hole 504B in the eastern equatorial Pacific on Legs 111 and 148 helped to constrain the P and S velocity structure at the site and showed that upper layer 3 at this site, at a depth of over 2 km into the crust, consisted of the lower portion of the sheeted dikes rather than gabbro. Both offset and normal incidence VSPs were run on Leg 164 to study the seismic velocity structure of gas hydrates on the Blake Ridge. A new innovation on ODP was the deployment of broadband seismometers in boreholes. Whereas the conventional VSPs and offset VSPs mentioned above operate in the frequency range from 1 to 100Hz, broadband seismometers are used in earthquake seismology and operate in the range from 0.001 to 10Hz. The first broadband seismometer test was carried out from the drill ship on Leg 128 in the Japan Sea. Subsequently 4 permanent broadband borehole seismic observatories were installed in the Western Pacific and Japan Trench on Legs 186, 191 and 195. The ODP era also saw the development of systems for re-entering boreholes from conventional research vessels after the drill ship left the site. Borehole seismic experiments and installations that used this wireline re-entry technology were carried out in DSDP Holes 534 (Blake

  18. The LUSI Seismic Experiment: Deployment of a Seismic Network around LUSI, East Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Karyono, Karyono; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Haryanto, Iyan; Masturyono, Masturyono; Hadi, Soffian; Rohadi, Suprianto; Suardi, Iman; Rudiyanto, Ariska; Pranata, Bayu

    2015-04-01

    The spectacular Lusi eruption started in northeast Java, Indonesia the 29 of May 2006 following a M6.3 earthquake striking the island. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. Lusi is located few kilometres to the NE of the Arjuno-Welirang volcanic complex. Lusi sits upon the Watukosek fault system. From this volcanic complex originates the Watukosek fault system that was reactivated by the M6.3 earthquake in 2006 and is still periodically reactivated by the frequent seismicity. To date Lusi is still active and erupting gas, water, mud and clasts. Gas and water data show that the Lusi plumbing system is connected with the neighbouring Arjuno-Welirang volcanic complex. This makes the Lusi eruption a "sedimentary hosted geothermal system". To verify and characterise the occurrence of seismic activity and how this perturbs the connected Watukosek fault, the Arjuno-Welirang volcanic system and the ongoing Lusi eruption, we deployed 30 seismic stations (short-period and broadband) in this region of the East Java basin. The seismic stations are more densely distributed around LUSI and the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. Fewer stations are positioned around the volcanic arc. Our study sheds light on the seismic activity along the Watukosek fault system and describes the waveforms associated to the geysering activity of Lusi. The initial network aims to locate small event that may not be captured by the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) seismic network and it will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-Arjuno Welirang region and temporal variations of vp/vs ratios. Such variations will then be ideally related to

  19. Education in Colonial Africa: The German Experience

    ERIC Educational Resources Information Center

    vanderPloeg, Arie J.

    1977-01-01

    Examines the introduction and growth of state-supported schools in two German colonies in Africa, Kamerun and Deutsch Ostafrika, describes African reaction to and utilization of them, assesses, from the colonial perspective, why such schools were introduced and what they were intended to accomplish, and examines the reasons for their differential…

  20. Deep seismic refraction experiment in northeast Brazil: New constraints for Borborema province evolution

    NASA Astrophysics Data System (ADS)

    Lima, Marcus Vinicius A. G. de; Berrocal, Jesus; Soares, José E. P.; Fuck, Reinhardt A.

    2015-03-01

    The Borborema Province of northeastern Brazil is a major Proterozoic crustal province that, until now, has never been explored using deep crustal seismic methods. Here are reported the first results obtained from a high-quality seismic refraction/wide-angle reflection profile that has defined the internal seismic velocity structure and thickness of the crust in this region. Almost 400 recording stations were deployed in the Deep Seismic Refraction (DSR) experiment through an NW-SE ca. 900 km linear array and 19 shots were exploded at every 50 km along the line. Data from the 10 southeastern most shots of the seismic profile were processed in this work. The main features and geological structures crossed by the studied portion of the profile belong to the so-called Central Sub-province of the Borborema tectonic province. The crustal model obtained is compatible with a typical structure of extended crust. The model was essentially divided into three layers: upper crust, lower crust, and a half-space represented by the shallower portion of the mantle. The Moho is an irregular interface with depth ranging between 31.7 and 34.5 km, and beneath the Central Sub-province it varies from 31.5 to 33 km depth, where its limits are related to major crustal discontinuities. The distribution of velocities within the crust is heterogeneous, varying vertically from 5.7 to 6.3 km/s in the upper crust and from 6.45 to 6.9 km/s in the lower crust. From the average crustal velocity distribution it is evident that the Central Sub-province has seismic characteristics different from neighboring domains. The crust is relatively thin and crustal thickness variations in the profile are subtle due to stretching that occurred in the Cretaceous, during the fragmentation of Pangaea, opening of the South Atlantic Ocean and separation of South America from Africa.

  1. Apollo 14 and 16 Active Seismic Experiments, and Apollo 17 Lunar Seismic Profiling

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Seismic refraction experiments were conducted on the moon by Apollo astronauts during missions 14, 16, and 17. Seismic velocities of 104, 108, 92, 114 and 100 m/sec were inferred for the lunar regolith at the Apollo 12, 14, 15, 16, and 17 landing sites, respectively. These data indicate that fragmentation and comminution caused by meteoroid impacts has produced a layer of remarkably uniform seismic properties moonwide. Brecciation and high porosity are the probable causes of the very low velocities observed in the lunar regolith. Apollo 17 seismic data revealed that the seismic velocity increases very rapidly with depth to 4.7 km/sec at a depth of 1.4 km. Such a large velocity change is suggestive of compositional and textural changes and is compatible with a model of fractured basaltic flows overlying anorthositic breccias. 'Thermal' moonquakes were also detected at the Apollo 17 site, becoming increasingly frequent after sunrise and reaching a maximum at sunset. The source of these quakes could possibly be landsliding.

  2. Seismic Analysis of Magmatism in the Galapagos Archipelago and East Africa

    NASA Astrophysics Data System (ADS)

    Tepp, Gabrielle

    Magmatism and deformation are consequences of fundamental processes shaping Earth's ˜150 km-thick continental and <125 km-thick oceanic plates. Earthquake seismology encompasses many methods to detect compositional and thermal boundaries from Earth's surface to the dynamic mantle driving plate tectonics. This work uses three different seismic methods to probe magma migration and storage and tectonism in two intraplate hotspot provinces: the Galapagos and East Africa. First, seismic body-wave tomography is used to image magma within oceanic crust of the largest Galapagos volcano, Sierra Negra. A laterally large, low-velocity region with many smaller, high-magnitude velocity anomalies is imaged at 8--15.5 km depths. No sharp seismic velocity increase is imaged within the resolvable depths, indicating that the thickened crust is at least 16 km deep. The second study involves a spectral analysis of earthquakes induced by the intrusion of thin sheets of magma rising beneath the Afar rift, East Africa. Earthquakes have varying spectral content, some with unusually large amplitude low-frequency content and enhanced surface waves. The analysis showed no clear boundaries between spectral types, suggesting that they are all primarily the result of brittle failure. Deep dike segments (tops > 3 km) induce only high-frequency volcano-tectonic earthquakes, while shallower dike segments induce the full range of spectral types. This suggests that low-frequency content is a result of shallow hypocenters, with path and site effects, surface ruptures, and dike fluid interactions all possible secondary causes. In the final study, shear-wave splitting analysis of teleseismic body-wave phases is conducted to evaluate strain and crack fabrics at the base of the continental plate as a consequence of magmatism, mantle flow, and plate stretching in the Western rift, East Africa. On average, fast directions are northeast, consistent with geodynamic models of mantle flow from the African

  3. Transformative Learning Experiences of International Graduate Students from Africa

    ERIC Educational Resources Information Center

    Kumi-Yeboah, Alex

    2014-01-01

    This article examines factors that influence transformative learning experiences of international graduate students from Africa. In general, 84.8% of the participants experienced transformative learning while 15.2% reported no transformative experiences. For those who experienced transformative learning, 26.1% of the transformative experiences…

  4. Results from the apollo-12 passive seismic experiment

    USGS Publications Warehouse

    Latham, G.

    1971-01-01

    The objective of the passive seismic experiment is to measure vibrations of the lunar surface produced by all natural and artificial sources of seismic energy and to use these data to deduce the internal structure and composition of the moon, the nature of forces which may cause deformation of the moon and moonquakes, and the numbers and masses of meteoroids striking the lunar surface. The ALSEP* seismometers can magnify lunar surface vibrations 10 million times. No instrument can operate on earth with this sensitivity, because weather and man produce too much seismic noise. To obtain answers to the above questions, seismic data must be combined with data from laboratory measurements of the physical and chemical properties of surface rocks, and many other geophyiscal and geochemical measurements. Thus far, we have had the opportunity to record data from two lunar seismic stations which were installed by the astronauts during Apollo misions  and 12. The combined recording time from the stations is presently over 12 months, but there was no overlap to permit recording of the same event at two stations. 

  5. Health care financing: recent experience in Africa.

    PubMed

    Dunlop, D W

    1983-01-01

    The economic realities of health sector development in Africa has been analyzed in this paper. Both the global and national macroeconomic context has been defined. Given the available data, it is clear that most African countries face increasingly serious economic realities, such as slow or even declining economic growth (per capita), a depressed food production situation, severe balance of payments crises, and increasing dependence on external financial assistance. Given the limited but increasingly available 1981 and 1982 data, the economic situation in many countries is more constrained than those indicated by the data contained in this paper. In this context, the potential competitive situation facing governmental health care systems was reviewed. In addition, the diversity in the sources of health expenditures between countries in Africa was highlighted. These data provide clear evidence that governments clearly do not finance the entire health care system and that individual payment for service in many countries represent an important source of revenue for many care providers in various health care systems operating in any given country. The potential for governments to finance either an expansion of or improvements to the government component of their health care systems is then reviewed. The highlights of this analysis include the following points. First, the tax structure in many African countries is highly dependent on export and import duties, which in turn creates dependency on sustained foreign demand for exports.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Seismic evidence for ultralow-velocity zones beneath Africa and eastern Atlantic

    NASA Astrophysics Data System (ADS)

    Helmberger, Don; Ni, Sidao; Wen, Lianxing; Ritsema, Jeroen

    2000-10-01

    SKS waveforms recorded at distances of about 110° are extremely useful to constrain seismic velocity structure at the base of the mantle. SKS waves near this distance develop a complicated interference pattern with the phases SPdKS and SKPdS. We report anomalous behavior of this interference in a number of recordings of deep earthquakes beneath South America from stations in Europe and Africa. We model these data with two-dimensional dome-like structures at the base of the mantle which extend laterally by a few hundred kilometers and in which the shear velocity is up to 30% lower than in the Preliminary Reference Earth Model (PREM). The spatial extent of these structures, their position with respect to the SKS core exit points, and their seismic characteristics can not be uniquely determined. However, the presence of a dipping or a concaved upper interface is a key attribute of successful models. Models that invoke flat layers are insufficiently complex to explain the most erratic waveform behavior. The most anomalous data correspond to sampling regions at the base of the mantle beneath the East African Rift and beneath the Iceland, where possibly, whole mantle upwellings form.

  7. Lithospheric geometries revealed through electromagnetic imaging: SAMTEX (Southern Africa MagnetoTelluric Experiment) observations and results

    NASA Astrophysics Data System (ADS)

    Jones, A. G.; Muller, M. R.; Evans, R. L.; Miensopust, M. P.; Khoza, D. T.; Samtex Team

    2011-12-01

    The Southern African Magnetotelluric Experiment (SAMTEX) is imaging the properties and geometries of the lithosphere below southern Africa to depths of 200+ km. Electrical conductivity is highly sensitive to ambient temperature, and to the presence of an interconnected conducting phase, such as a solid phase like graphite or sulphides, a fluid phase like partial melt, or bound water through hydrogen diffusion. Thus, primary geometrical information can be readily obtained from lithospheric-scale MT experiments about the three-dimensional variation in conductivity that can be related to formation and deformation processes. One important piece of information easily obtained from MT data is the depth to the lithosphere-asthenosphere boundary (LAB), due to the sensitivity of conductivity to small fractions (<1%) of partial melt and/or of some hundreds of ppm of bound water. SAMTEX measurements have been made at a total of more than 750 MT sites over an area in excess of a million square kilometres, making it by far the largest-ever regional MT project undertaken. One of the most significant results from SAMTEX is the mapping of the LAB beneath the Archean cratons and bounding mobile belts of Southern Africa, particularly of the previously unknown regions of Namibia and Botswana. The LAB is shallow (150 km) beneath the mobile belts, deep (250 km) in the centres of the cratons, and transitional at the edges. Diamondiferous kimberlites are located primarily where lithosphere is transitional in thickness, or where there is a change in its anisotropy properties, both of which are craton edge effects. The electrical properties of the continental mantle derived from SAMTEX data can be compared with seismic ones derived from data from the South African Seismic Experiment (SASE) of the Kaapvaal Project. Generally there is very good predictive linear agreement between seismic velocity and log(conductivity), indicative of both being influenced by the same bulk property factors

  8. Advancing drug availability-experiences from Africa.

    PubMed

    Powell, Richard A; Kaye, Richard Mugula; Ddungu, Henry; Mwangi-Powell, Faith

    2010-07-01

    International health and drug regulatory authorities acknowledge that analgesics (especially opioids) are insufficiently available for pain management in many countries. In Africa, reported morphine consumption is far below the global mean, with multiple factors hampering opioid supply. Since 2006, the African Palliative Care Association has hosted three regional drug availability workshops across the continent to address this issue. Using an interactive format, the workshops have identified country-specific barriers to opioid and other essential medication accessibility before supporting participants to develop action plans to address recognized impediments. Despite multiple challenges, a number of successes have arisen from the implementation of the plans. However, key issues remain, including the introduction of supportive policy environments, effective educational initiatives, and measures to address supply-chain obstacles impeding drug availability.

  9. A deployment of broadband seismic stations in two deep gold mines, South Africa

    USGS Publications Warehouse

    McGarr, Arthur F.; Boettcher, Margaret S.; Fletcher, Jon Peter B.; Johnston, Malcolm J.; Durrheim, R.; Spottiswoode, S.; Milev, A.

    2009-01-01

    In-mine seismic networks throughout the TauTona and Mponeng gold mines provide precise locations and seismic source parameters of earthquakes. They also support small-scale experimental projects, including NELSAM (Natural Earthquake Laboratory in South African Mines), which is intended to record, at close hand, seismic rupture of a geologic fault that traverses the project region near the deepest part of TauTona. To resolve some questions regarding the in-mine and NELSAM networks, we deployed four portable broadband seismic stations at deep sites within TauTona and Mponeng for one week during September 2007 and recorded ground acceleration. Moderately large earthquakes within our temporary network were recorded with sufficiently high signal-to-noise that we were able to integrate the acceleration to ground velocity and displacement, from which moment tensors could be determined. We resolved the questions concerning the NELSAM and in-mine networks by using these moment tensors to calculate synthetic seismograms at various network recording sites for comparison with the ground motion recorded at the same locations. We also used the peak velocity of the S wave pulse, corrected for attenuation with distance, to estimate the maximum slip within the rupture zone of an earthquake. We then combined the maximum slip and seismic moment with results from laboratory friction experiments to estimate maximum slip rates within the same high-slip patches of the rupture zone. For the four largest earthquakes recorded within our network, all with magnitudes near 2, these inferred maximum slips range from 4 to 27 mm and the corresponding maximum slip rates range from 1 to 6 m/s. These results, in conjunction with information from previous ground motion studies, indicate that underground support should be capable of withstanding peak ground velocities of at least 5 m/s.

  10. Seismic imaging of sandbox experiments - laboratory hardware setup and first reflection seismic sections

    NASA Astrophysics Data System (ADS)

    Krawczyk, C. M.; Buddensiek, M.-L.; Oncken, O.; Kukowski, N.

    2012-10-01

    With the study and technical development introduced here, we combine analogue sandbox simulation techniques with seismic physical modelling of sandbox models. For that purpose, we designed and developed a new mini-seismic facility for laboratory use, comprising a seismic tank, a PC-driven control unit, a positioning system, and piezo-electric transducers used here the first time in an array mode. To assess the possibilities and limits of seismic imaging of small-scale structures in sandbox models, different geometry setups were tested in the first experiments that also tested the proper functioning of the device and studied the seismo-elastic properties of the granular media used. Simple two-layer models of different materials and layer thicknesses as well as a more complex model comprising channels and shear zones were tested using different acquisition geometries and signal properties. We suggest using well sorted and well rounded grains with little surface roughness (glass beads). Source receiver-offsets less than 14 cm for imaging structures as small as 2.0-1.5 mm size have proven feasible. This is the best compromise between wide beam and high energy output, and being applicable with a consistent waveform. Resolution of the interfaces of layers of granular materials depends on the interface preparation rather than on the material itself. Flat grading of interfaces and powder coverage yields the clearest interface reflections. Finally, sandbox seismic sections provide images of very good quality showing constant thickness layers as well as predefined channel structures and fault traces from shear zones. Since these can be regarded in sandbox models as zones of decompaction, they behave as reflectors and can be imaged. The multiple-offset surveying introduced here improves the quality with respect to S/N-ratio and source signature even more; the maximum depth penetration in glass bead layers thereby amounts to 5 cm. Thus, the presented mini-seismic device is

  11. Creating Cultural Competence: An Outreach Immersion Experience in Southern Africa

    ERIC Educational Resources Information Center

    West-Olatunji, Cirecie; Goodman, Rachael D.; Mehta, Sejal; Templeton, Laura

    2011-01-01

    With disasters on the rise, counselors need to increase their cultural awareness, knowledge, and skills to work with affected communities. This study reports outcomes of a four-week immersion experience in southern Africa with six counselor-trainees. Data sources for this qualitative study were: daily journals and demographic forms. Outcomes…

  12. Ambient seismic noise levels: A survey of the permanent and temporary seismographic networks in Morocco, North Africa

    NASA Astrophysics Data System (ADS)

    El Fellah, Y.; Khairy Abd Ed-Aal, A.; El Moudnib, L.; Mimoun, H.; Villasenor, A.; Gallart, J.; Thomas, C.; Elouai, D.; Mimoun, C.; Himmi, M.

    2013-12-01

    Abstract The results, of a conducted study carried out to analyze variations in ambient seismic noise levels at sites of the installed broadband stations in Morocco, North Africa, are obtained. The permanent and the temporary seismic stations installed in Morocco of the Scientific Institute ( IS, Rabat, Morocco), institute de Ciencias de la Tierra Jaume almera (ICTJA, Barcelona, Spain) and Institut für Geophysik (Munster, Germany) were used in this study. In this work, we used 23 broadband seismic stations installed in different structural domains covering all Morocco from south to north. The main purposes of the current study are: 1) to present a catalog of seismic background noise spectra for Morocco obtained from recently installed broadband stations, 2) to assess the effects of experimental temporary seismic vault construction, 3) to determine the time needed for noise at sites to stabilize, 4) to establish characteristics and origin of seismic noise at those sites. We calculated power spectral densities of background noise for each component of each broadband seismometer deployed in the different investigated sites and then compared them with the high-noise model and low-noise Model of Peterson (1993). All segments from day and night local time windows were included in the calculation without parsing out earthquakes. The obtained results of the current study could be used forthcoming to evaluate permanent station quality. Moreover, this study could be considered as a first step to develop new seismic noise models in North Africa not included in Peterson (1993). Keywords Background noise; Power spectral density; Model of Peterson; Scientific Institute; Institute de Ciencias de la Tierra Jaume almera; Institut für Geophysik

  13. A Preliminary Look at the Crust and Upper Mantle of North Africa Using Libyan Seismic Data

    SciTech Connect

    Pasyanos, M

    2005-08-05

    In recent years, LLNL has been developing methods to jointly invert both surface wave dispersion data and teleseismic receiver functions. The technique holds great promise in accurately estimating seismic structure, including important tectonic parameters such as basin thickness, crustal thickness, upper mantle velocity, etc. We proposed applying this method to some recently available data from several Libyan stations, as we believe the technique has not been applied to any stations in Libya. The technique holds the promise of improving our understanding of the crust and upper mantle in Libya and North Africa. We recently requested seismic data from stations GHAR (Gharyan) and MARJ (Al Marj) in Libya for about 20 events. The events were large events at regional distances suitable for making dispersion measurements. An example of waveforms recorded at the two stations from an earthquake in Italy is shown in Figure 1. The paths traverse the Ionian Sea. Notice the slow short period group velocities of the surface waves across the Mediterranean, particularly to the easternmost station MARJ. However, because of data availability, signal-to-noise ratio, etc. we were unable to make measurements for every one of these events at both stations. Figure 2 shows a map of paths for 20 sec Rayleigh waves in the eastern Mediterranean region. Paths measured at the two Libyan stations are shown in green. Rayleigh wave dispersion measurements at 20 sec period are sensitive to velocities in the upper 20 km or so, and reveal sediment thickness, crustal velocity, and crustal thickness. Tomographic inversions reveal the sharp group velocity contrast between regions with deep sedimentary basins and those without. Figure 3, the result of an inversion made before adding the new dispersion measurements, shows slow group velocities in the Black Sea, Adriatic Sea, and Eastern Mediterranean. In general, these features correspond well with the sediment thickness model from Laske, shown in Figure

  14. Cataloguing Seismic Waveform Properties Recorded With a 3D Network in a Gold Mine in South Africa

    NASA Astrophysics Data System (ADS)

    Julia, J.; Nyblade, A. A.; Gok, R.; Walter, W. R.; Linzer, L.; Durrheim, R. J.; Dirks, P.

    2007-12-01

    The SAVUKA gold mine is located in the northwestern edge of the Witwatersrand basin, a Late Archean (3.07- 2.71~Ga) intracratonic basin in South Africa that hosts the largest known gold-uranium-pyrite ore deposits in the world. Seismic events related to the mine activity span several orders of magnitude through a variety of sources that include mine blasts, pillar collapses, and faulting events. These events are systematically recorded and catalogued through an in-mine, 3D seismic network consisting of 20, three-component, short-period stations with natural frequencies ranging between 4.5 and 28.0~Hz and deployed as deep as ~3.5 km. After 5 months of seismic monitoring of the mine, we have been able to assemble a database of over 6000 events spanning magnitudes in the -2.5 < ML < 4.4 range. The potential of this unique data set for characterizing the detailed seismic properties of the basin and studying source properties of non-double couple events is explored through simple, first-pass analysis on the recorded waveforms. Moreover, the in-mine network is complemented by a small array of 4 broadband stations interspaced ~10~km apart on the surface of the mine, and by a number of AfricaArray stations in South Africa and neighboring countries located at regional distances (50- 1000~km) from the mine. The largest mine-induced events are clearly recorded at distances as far away from the mine as 450~km and provide a unique opportunity for studying the regional propagation of seismic phases as well as the structure of the cratonic crust underlying the basin.

  15. Seismic attribute analysis to enhance detection of thin gold-bearing reefs: South Deep gold mine, Witwatersrand basin, South Africa

    NASA Astrophysics Data System (ADS)

    Manzi, M. S. D.; Hein, K. A. A.; Durrheim, R.; King, N.

    2013-11-01

    The gold-bearing Upper Elsburg Reef clastic wedge (UER) in the South Deep gold mine in the Witwatersrand basin (South Africa) hosts the highly auriferous basal conglomerate known as the Elsburg Conglomerate (EC) reef. The reef is less than 20 m thick and together with quartzite and conglomerate beds in the UER (1-120 m thick) is below the seismic tuning thickness, or the dominant quarter wavelength. They are extremely difficult to identify on migrated seismic sections using traditional amplitude interpretations. In order to enhance the detection of the EC reef and its subcrop position against the overlying Ventersdorp Contact Reef (VCR), complex-trace seismic attributes, or instantaneous attributes and volume attribute analysis were applied on prestack time migrated (PSTM) seismic sections. In particular, the instantaneous phase and paraphase allowed the clear identification of the continuity of the EC reef, and overlapping and interfering wavelets produced by the convergence of VCR and the EC reef. In addition, these attributes increased confidence in the interpretation of the EC, in particular its offsets (faults), and its depth. A high correlation between the seismically determined depth of the EC reef and borehole intersections was observed, with several depth discrepancies below the vertical seismic resolution limit (~ 25 m). This information can now be incorporated into the current mine geological model, thus improving the resource evaluation of the Upper Elsburg Reef in the South Deep gold mine.

  16. Fault Kinematics and Seismic Anisotropy Patterns in the Natron-Magadi Basins, Africa

    NASA Astrophysics Data System (ADS)

    Weinstein, A.

    2015-12-01

    Early-stage continental rift zones provide important insights into the deformation behavior of crust and mantle lithosphere, and its modification by the migration of magma and volatiles. In East Africa, lower crustal earthquakes provide opportunities to probe the deformation behavior of the entire crust. We use a catalogue of 3068 earthquakes of 1 < ML < 4.5 recorded on a 39-station seismic array spanning three 3 rift segments ( Magadi-Natron-Manyara) of the Eastern rift, Africa to determine kinematics of large offset border faults, their along-strike linkage, and their possible interactions with tomographically imaged magma conduits and reservoirs beneath active and dormant volcanoes. Earthquake focal mechanisms are predominantly NS-striking normal faults with steep dips from near surface to 25 km in the Natron and Magadi basins, whereas the strike of normal faults locally rotates to N60E at the northern tip of the Manyara border fault. This rift-oblique structure links the Manyara border fault to Gelai shield volcano via Oldoinyo Lengai volcano, and may be a zone of magma transfer. Crustal anisotropy measurements from lower crustal earthquakes provide information on the orientation of fluid-filled cracks and any strain fabric. We compare our new crustal splitting observations with the rift parallel anisotropy determined by ambient noise tomography, and with mantle anisotropy patterns determined from SKS-splitting. Initial results of SKS-splitting (> 1 s) show both the NS and NE fast directions at different stations, suggesting that aligned melt-filled cracks contribute to the observed patterns, as in more evolved rift sectors, like the Ethiopian and Afar rifts.

  17. My Fulbright Experience in South Africa

    NASA Astrophysics Data System (ADS)

    Capps, Ken

    2009-08-01

    As part of the Fulbright Scholar Program, the author lectured in general chemistry courses and assisted with curriculum development at the University of Kwa-Zulu Natal. The educational systems and the students in general are compared with the author's experiences teaching in Florida, USA.

  18. IRIS Controlled Source Seismic Experiments: Continental Structure, Instrumentation, and Education

    NASA Astrophysics Data System (ADS)

    Mooney, W. D.; Keller, G. R.

    2004-12-01

    The controlled-source seismology program of IRIS/PASSCAL has made major contributions to the study of continental structure and evolution. It has also undergone major developments in seismic instrumentation. The first PASSCAL experiments (1984/85) targeted the Basin and Range Province and the Ouachita orogenic belt. The Basin and Range study provided remarkably clear images of this thin, highly-extended crust, while the Ouachita experiment tested competing hypotheses for the deep structure of this Paleozoic orogen. However, both of these projects were limited by a lack of seismic instruments. The situation improved in the late 1980's with the benefit of a mixed array of 600 seismic recorders from the USGS, Stanford, and the Geological Survey of Canada. The resolution achieved with these instruments was revolutionary. Results include the imaging of such remarkable features as crustal-scale duplexes in the Brooks Range compressional orogen of northern Alaska, and of crustal "core complexes" in the extended crust of southwest Arizona. The 3-channel PASSCAL Jr. instrument was developed, leading to experiments in which ˜1000 instruments were deployed, including three-component recording. This complex mix of instruments served the community well for several years, but required large, complex instrument centers and lots of technical support. With input from PASSCAL and the international community, a newly designed, compact instrument (the Texan) was finalized in the spring of 1998, and the first 200 instruments was delivered to the Univ. of Texas-El Paso in late 1998. The present instrument pool of Texans exceeds 1,400 and these have been used on such projects as the high-resolution imaging of the Los Angeles and San Fernando basins (LARSE I and II experiments), where active thrust faults have been imaged. Controlled-source seismic experiments are now very numerous. During calendar year 2004 alone, portable Texan instruments have traveled from Venezuela to Denmark

  19. Seismic imaging beneath southwest Africa based on finite-frequency body wave tomography

    NASA Astrophysics Data System (ADS)

    Youssof, Mohammad; Yuan, Xiaohui; Tilmann, Frederik; Heit, Benjamin; Weber, Michael; Jokat, Wilfried; Geissler, Wolfram; Laske, Gabi

    2016-04-01

    We present a seismic model of southwest Africa from teleseismic tomographic inversion of the P- and S- wave data recorded by an amphibious temporary seismic network. The area of study is located at the intersection of the Walvis Ridge with the continental margin of northern Namibia, and extends into the Congo craton. Utilizing 3D finite-frequency sensitivity kernels, we invert traveltime residuals of the teleseismic body waves to image seismic structures in the upper mantle. To test the robustness of our tomographic imaging, we employed various resolution assessments that allow us to inspect the extent of smearing effects and to evaluate the optimum regularization weights (i.e., damping and smoothness). These tests include applying different (ir)regular parameterizations, classical checkerboard and anomaly tests and squeezing modeling. Furthermore, we performed different kinds of weighing schemes for the traveltime dataset. These schemes account for balancing between the picks data amount with their corresponding events directions. Our assessment procedure involves also a detailed investigation of the effect of the crustal correction on the final velocity image, which strongly influenced the image resolution for the mantle structures. Our model can resolve horizontal structures of 1° x 1° below the array down to 300-350 km depth. The resulting model is mainly dominated by the difference in the oceanic and continental mantle lithosphere beneath the study area, with second-order features related to their respective internal structures. The fast lithospheric keel of the Congo Craton reaches a depth of ~250 km. The orogenic Damara Belt and continental flood basalt areas are characterized by low velocity perturbations down to a depth of ~150 km, indicating a normal fertile mantle. High velocities in the oceanic lithosphere beneath the Walvis Ridge appear to show signatures of chemical depletion. A pronounced anomaly of fast velocity is imaged underneath continental NW

  20. 3D Seismic Reflection Experiment over the Galicia Deep Basin

    NASA Astrophysics Data System (ADS)

    Sawyer, D. S.; Jordan, B.; Reston, T. J.; Minshull, T. A.; Klaeschen, D.; Ranero, C.; Shillington, D. J.; Morgan, J. K.

    2014-12-01

    In June thru September, 2013, a 3D reflection and a long offset seismic experiment were conducted at the Galicia rifted margin by investigators from the US, UK, Germany, and Spain. The 3D multichannel experiment covered 64 km by 20 km (1280 km2), using the RV Marcus Langseth. Four streamers 6 km long were deployed at 12.5 m hydrophone channel spacing. The streamers were 200 m apart. Two airgun arrays, each 3300 cu in, were fired alternately every 37.5 m, to collectively yield a 400 m wide sail line consisting of 8 CMP lines at 50 m spacing. The long offset seismic experiment included 72 short period OBS's deployed below the 3D reflection survey box. Most of the instruments recorded all the shots from the airgun array shots. The 3D seismic box covered a variety of geologic features. The Peridotite Ridge (PR), is associated with the exhumation of upper mantle rocks to the seafloor during the final stage of the continental separation between the Galicia Bank and the Grand Banks of Newfoundland. The S reflector is present below most of the continental blocks under the deep Galicia basin. S is interpreted to be a low-angle detachment fault formed late in the rifting process, and a number of rotated fault block basins and ranges containing pre and syn-rift sediments. Initial observations from stacked 3D seismic data, and samples of 2D pre-stack time migrated (PSTM) 3D seismic data show that the PR is elevated above the present seafloor in the South and not exposed through the seafloor in the North. The relative smoothness of the PR surface for the entire 20 km N-S contrasts with the more complex, shorter wavelength, faulting of the continental crustal blocks to the east. The PR does not seem to show offsets or any apparent internal structure. The PSTM dip lines show substantial improvement for the structures in the deep sedimentary basin East of the PR. These seem to extend the S reflector somewhat farther to the West. The migrated data show a substantial network of

  1. Seismic tomography Technology for the Water Infiltration Experiment

    SciTech Connect

    J. Descour

    2001-04-30

    NSA Engineering, Inc., conducted seismic tomography surveys in Niche No.3 in the Exploratory Studies Facility (ESF), Yucca Mountain, Nevada, and Alcove No.8 in the Enhanced Characterization of the Repository Block (ECRB) cross drift as part of the Infiltration Experiment being conducted in Niche No.3. NSA Engineering is a direct support contractor to the Yucca Mountain Project. This report documents the work performed from August 14 through 30, 2000, prior to the beginning of the infiltration experiment. The objective of the seismic tomography survey was to investigate the flow path of water between access drifts and more specifically to (Kramer 2000): (1) Conduct a baseline seismic tomography survey prior to the infiltration experiment; (2) Produce 2-D and 3-D tomographic images of the rock volume between Alcove No.8 and Niche No.3; (3) Correlate tomography results with published structural and lithological features, and with other geophysical data such as ground penetrating radar (GPR); and (4) Results of this survey will form a baseline with which to compare subsequent changes to the rock mass. These changes may be as a result of the water infiltration tests that could be conducted in Alcove No.8 in 2001. The scope of this reported work is to use the velocity tomograms to: (a) assess the structures and lithologic features within the surveyed area and/or volume between the two access drifts; and (b) provide information on the structural state of the rock mass as inferred by the velocity signatures of the rock prior to the beginning of the infiltration experiment.

  2. Looking for seismic scatterers: summer research experience for undergraduate students

    NASA Astrophysics Data System (ADS)

    Gerasimenko, I.; Bagchi, S.; Toteva, T.; Peng, Z.

    2008-12-01

    This project was part of collaboration between Randolph College (VA) and Georgia Institute of Technology (GA). It was designed as summer research experience for undergraduate students. The duration of the project was eight weeks. The aim of this study was to search for fault zone scatterers in the Parkfield section of the San Andreas Fault, and examine the presence or absence of physical changes in the scattering intensity before and after the 2004 M6 Parkfield earthquake. The two students visited Georgia Tech for a week and were trained to manipulate seismic data in Seismic Analysis Code (SAC) format. They assembled a data base of over a thousand events that occurred before and after the M6 earthquake and were recorded by the USGS Parkfield, California, dense seismograph array (UPSAR). They manually picked the arrivals for the P and S waves. Additional signal processing such as frequency filtering and semblance analysis were applied to the records in search for isolated scatterers in the seismic coda. While the eight-week-long research was not enough for the students to complete their project, it was certainly enough to sparkle excitement for conducting seismological research. Currently both students are enrolled in a research topics class and continue to work on this project. Their past and future work will be presented at the meeting.

  3. Results of a seismic forecasting experiment for the Kamchatka region

    NASA Astrophysics Data System (ADS)

    Doda, L. N.; Natyaganov, V. L.; Shopin, S. A.

    2016-08-01

    The integral results of a seismic forecasting experiment for the powerful M > 7 earthquakes in the Kamchatka region are presented. According to the empirical scheme of the short-term earthquake prediction, since 2002 all officially recorded forecasts, including five deep-focus earthquakes in the Sea of Okhotsk, have been predicted without missing events. The specific character of the features of the earthquake preparation and the annular cloud structures that began to be observed in satellite images near the coast of Japan at the boundary of the Okhotsk plate are analyzed.

  4. Seismic amplification within the Seattle Basin, Washington State: Insights from SHIPS seismic tomography experiments

    USGS Publications Warehouse

    Snelson, C.M.; Brocher, T.M.; Miller, K.C.; Pratt, T.L.; Trehu, A.M.

    2007-01-01

    Recent observations indicate that the Seattle sedimentary basin, underlying Seattle and other urban centers in the Puget Lowland, Washington, amplifies long-period (1-5 sec) weak ground motions by factors of 10 or more. We computed east-trending P- and S-wave velocity models across the Seattle basin from Seismic Hazard Investigations of Puget Sound (SHIPS) experiments to better characterize the seismic hazard the basin poses. The 3D tomographic models, which resolve features to a depth of 10 km, for the first time define the P- and S-wave velocity structure of the eastern end of the basin. The basin, which contains sedimentary rocks of Eocene to Holocene, is broadly symmetric in east-west section and reaches a maximum thickness of 6 km along our profile beneath north Seattle. A comparison of our velocity model with coincident amplification curves for weak ground motions produced by the 1999 Chi-Chi earthquake suggests that the distribution of Quaternary deposits and reduced velocity gradients in the upper part of the basement east of Seattle have significance in forecasting variations in seismic-wave amplification across the basin. Specifically, eastward increases in the amplification of 0.2- to 5-Hz energy correlate with locally thicker unconsolidated deposits and a change from Crescent Formation basement to pre-Tertiary Cascadia basement. These models define the extent of the Seattle basin, the Seattle fault, and the geometry of the basement contact, giving insight into the tectonic evolution of the Seattle basin and its influence on ground shaking.

  5. The planning of a passive seismic experiment: the Ketzin case

    NASA Astrophysics Data System (ADS)

    Rossi, G.; Petronio, L.

    2009-04-01

    In the last years, it has been recognized the importance of using microseismic activity data to gain information on the state and dynamics of a reservoir, notwithstanding the difficulties of recording, localizing the events, interpret them correctly, in terms of developing fractures, or thermal effects. The increasing number of CO2 storage experiments, with the necessity of providing efficient, economic, and long-term monitoring methods, both in the injection and post-injection phases, further encourage the development and improvement of recording and processing techniques. Microseismic signals are typically recorded with downhole sensors. Monitoring with surface sensors is problematic due to increased noise levels and signal attenuation particularly in the near surface. The actual detection distance depends on background noise conditions, seismic attenuation and the microseismic source strength. In the frame of the European project Co2ReMoVe and of the European Network of Excellence Co2GeoNet, a passive seismic experiment was planned in the Ketzin site for geological storage of CO2, a former gas store near Potsdam, object of the CO2SINK European project and inserted also in the European project Co2ReMoVe. Aim of the survey is to complement the CO2-SINK active seismic downhole experiments, adding precious information on the microseismicity induced by stress field changes at the reservoir level and in the overburden, due to the CO2 injection. The baseline survey was done in May 2008 by the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale-OGS (Italy), with the support of the Deutsches GeoForschungsZentrum-GFZ (Germany) and the collaboration of the Institut für Geowissenschaftliche Gemeinschaftsaufgaben-GGA (Germany), shortly before the starting of the CO2 injection (June 30th 2008). A continuous monitoring (about 5 days) was performed by 2 downhole 3C geophones, and 3 surface 3C geophones located around the wells. This paper, based on the analysis of

  6. 3D Seismic Reflection Experiment Over the Galicia Deep Basin

    NASA Astrophysics Data System (ADS)

    Sawyer, Dale; Jordan, Brian; Tesi Sanjurjo, Mari; Alexanian, Ara; Morgan, Julia; Shillington, Donna; Reston, Timothy; Minshull, Timothy; Klaeschen, Dirk; Ranero, César

    2014-05-01

    In June thru September, 2013, a 3D reflection and a long offset seismic experiment were conducted at the Galicia rifted margin by investigators from the US, UK, Germany, and Spain. The 3D multichannel experiment covered 64 km by 20 km (1280 km2), using the RV Marcus Langseth. Four streamers 6 km long were deployed at 12.5 m hydrophone channel spacing. The streamers were 200 m apart. Two airgun arrays, each 3300 cu in, were fired alternately every 37.5 m, to collectively yield a 400 m wide sail line consisting of 8 CMP lines at 50 m spacing. The long offset seismic experiment included 72 short period OBS's deployed below the 3D reflection survey box. Most of the instruments recorded all the shots from the airgun array shots. The 3D seismic box covered a variety of geologic features. The Peridotite Ridge (PR), is associated with the exhumation of upper mantle rocks to the seafloor during the final stage of the continental separation between the Galicia Bank and the Grand Banks of Newfoundland. The S reflector is present below most of the continental blocks under the deep Galicia basin. S is interpreted to be a low-angle detachment fault formed late in the rifting process, and a number of rotated fault block basins and ranges containing pre and syn-rift sediments. Initial observations from stacked, but not yet migrated, 3D seismic data show that the PR is elevated above the present seafloor in the South and not exposed through the seafloor in the North. The relative smoothness of the PR surface for the entire 20 km N-S contrasts with the more complex, shorter wavelength, faulting of the continental crustal blocks to the east. The PR does not seem to show offsets or any apparent internal structure. However, migration will be required to see internal structure of the PR. Between the PR and the western most rifted continental crustal blocks, is a sedimentary basin about as wide as the PR and very different from the sedimentary basins bounded by the continental crustal

  7. The KRISP 90 seismic experiment-a technical review

    USGS Publications Warehouse

    Prodehl, C.; Mechie, J.; Achauer, U.; Keller, Gordon R.; Khan, M.A.; Mooney, W.D.; Gaciri, S.J.; Obel, J.D.

    1994-01-01

    On the basis of a preliminary experiment in 1985 (KRISP 85), a seismic refraction/wide-angle reflection survey and a teleseismic tomography experiment were jointly undertaken to study the lithospheric structure of the Kenya rift down to depths of greater than 200 km. This report serves as an introduction to a series of subsequent papers and will focus on the technical description of the seismic surveys of the main KRISP 90 effort. The seismic refraction/wide-angle reflection survey was carried out in a 4-week period in January and February 1990. It consisted of three profiles: one extending along the rift valley from Lake Turkana to Lake Magadi, one crossing the rift at Lake Baringo, and one located on the eastern flank of the rift proper. A total of 206 mobile vertical-component seismographs, with an average station interval of about 2 km, recorded the energy of underwater and borehole explosions to distances of up to about 550 km. During the teleseismic survey an array of 65 seismographs was deployed to record teleseismic, regional and local events for a period of about 7 months from October 1989 to April 1990. The elliptical array spanned the central portion of the rift, with Nakuru at its center, and covered an area about 300 ?? 200 km, with an average station spacing of 10-30 km. Major scientific goals of the project were to reveal the detailed crustal and upper-mantle structure under the Kenya rift, to study the relationship between deep crustal and mantle structure and the development of sedimentary basins and volcanic features within the rift, to understand the role of the Kenya rift within the Afro-Arabian rift system, and to answer fundamental questions such as the mode and mechanism of continental rifting. ?? 1994.

  8. Towards a Comprehensive Seismic Velocity Model for the Broader Africa-Eurasia Collision Region, to Improve Nuclear Explosion Monitoring

    SciTech Connect

    der Lee, S v; Flanagan, M P; Rodgers, A J; Pasyanos, M E; Marone, F; Romanowicz, B

    2005-07-13

    We report on progress towards a new, comprehensive three-dimensional model of seismic velocity in a broad region encompassing the Middle East, northern Africa, the Mediterranean Sea, the Levant, the Arabian Peninsula, the Turkish-Iranian Plateau, Indus Valley, and the Hindu Kush. Our model will be based on regional waveform fits, surface wave group velocity measurements, teleseismic arrival times of S and P waves, receiver functions, and published results from active source experiments. We are in the process of assembling each of these data sets and testing the joint inversion for subsets of the data. Seismograms come from a variety of permanent and temporary seismic stations in the region. Some of the data is easily accessible through, for example, IRIS, while collection of other data is more involved. This work builds on ongoing work by Schmid et al. (GJI, 2004, and manuscript in preparation). In these proceedings we highlight our data sets and their inferences, demonstrate the proposed new data-inversion modeling methodology, discuss results from preliminary inversions of subsets of the data, and demonstrate the prediction of arrival times with three-dimensional velocity models. We compare our preliminary inversion results to the results of Schmid et al., and the predicted arrival times to ground-truth data from the NNSA Knowledge Base. Our data sets are simultaneously redundant and highly complementary. The combined data coverage will ensure that our three-dimensional model comprises the crust, the upper mantle, including the transition zone, and the top of the lower mantle, with spatially varying, but useful resolution. The region of interest is one of the most structurally heterogeneous in the world. Continental collision, rifting and sea-floor spreading, back-arc spreading, oceanic subduction, rotating micro plates, continental shelf, and stable platforms, are just some of the region's characteristics. Seismicity and the distribution of seismic stations are

  9. High resolution reverse VSP and interwell seismic experiments at the Buckhorn test site in Illinois

    SciTech Connect

    Parra, J.O.; Bangs, J.H.

    1992-07-01

    Reverse Vertical Seismic Profiling VSP and interwell seismic experiments were conducted at the Western Kentucky Petroleum Buckhorn test site near Quincy, Illinois. The RVSP data were acquired using a 3-component pneumatic probe and the interwell seismic data were acquired using a 24-element hydrophone array. The experiments were conducted to analyze high resolution seismic waveforms and to perform travel time velocity inversion for mapping the Silurian Kankakee formation which is the more prolific oil producer in the Mt. Sterling area. Reverse VSP and interwell seismic measurements together with log data have yielded information on the anisotropic characteristic of the shale formation and in the compressional wave velocity distribution of the limestone formation. These results inferred that reverse VSP (using several 3-component detectors in shallow boreholes) and interwell seismic measurements integrated with log data and seismic modeling can delineate the hydrocarbon reservoir and geological structures at the Buckhorn test site.

  10. High resolution reverse VSP and interwell seismic experiments at the Buckhorn test site in Illinois

    SciTech Connect

    Parra, J.O.; Bangs, J.H.

    1992-01-01

    Reverse Vertical Seismic Profiling VSP and interwell seismic experiments were conducted at the Western Kentucky Petroleum Buckhorn test site near Quincy, Illinois. The RVSP data were acquired using a 3-component pneumatic probe and the interwell seismic data were acquired using a 24-element hydrophone array. The experiments were conducted to analyze high resolution seismic waveforms and to perform travel time velocity inversion for mapping the Silurian Kankakee formation which is the more prolific oil producer in the Mt. Sterling area. Reverse VSP and interwell seismic measurements together with log data have yielded information on the anisotropic characteristic of the shale formation and in the compressional wave velocity distribution of the limestone formation. These results inferred that reverse VSP (using several 3-component detectors in shallow boreholes) and interwell seismic measurements integrated with log data and seismic modeling can delineate the hydrocarbon reservoir and geological structures at the Buckhorn test site.

  11. Intense convection over West Africa during AMMA SOP3 experiment

    NASA Astrophysics Data System (ADS)

    Lenouo, André; Sall, Saïdou Moustapha; Badiane, Daouda; Gaye, Amadou Thierno; Kamga Mkankam, F.

    2016-11-01

    ERA-Interim product from the European Center for Medium-Range Weather Forecast (ECMWF) assimilation of African Monsoon Multidisciplinary Analysis (AMMA) resources, Meteosat satellite images, and synoptic observations were used to study local- and regional-scale environments associated with intense convective systems during the AMMA-SOP3 experiment over West Africa in the Northern Hemisphere of summer 2006. The convective system, from the 21st to 23rd of August 2006, was more active at 0000 and 1800 UTC showing diurnal cycle of deep convection over West Africa where the African easterly waves (AEWs) are developed downstream. Downstream barotropic and baroclinic energy conversions associated with strong AEWs are important for the maintenance of AEW activity in West Africa. Barotropic energy conversions dominate south of the African easterly jet (AEJ), while baroclinic energy conversions are most important north of the AEJ. From a dynamical viewpoint, the low-level vorticity presents strong positive values over the sea and Sahara zone, indicating that exists on the cyclonic shear side of the African easterly jet, which is consistent with baroclinic growth. The 925-hPa equivalent potential temperature structure show a maximum over the Sahara which corresponds to the depression observed in this region. A mosaic of three hourly infrared (IR) satellite images, depicts a very distinct signal from an initial region of convection, developing through several stages and moving off the African coast. These observations, along with those available from the World Weather Watch, provide an opportunity to carry out numerical weather prediction (NWP) studies over West Africa utilizing high resolution limited area models.

  12. Mothers' experiences of genetic counselling in Johannesburg, South Africa.

    PubMed

    Morris, Megan; Glass, Merlyn; Wessels, Tina-Marié; Kromberg, Jennifer G R

    2015-02-01

    Genetic counselling is offered in diverse settings, and patient reactions vary due to differences in personal, family and community beliefs, local healthcare settings, as well as cultural background. Together, these factors influence how individuals experience genetic counselling. This study aimed to describe and document the experiences of thirteen mothers, with children with Down syndrome, oculocutaneous albinism or haemophilia B, who had received genetic counselling at state hospitals in Johannesburg, South Africa. A qualitative research design drawing on principles of Interpretative Phenomenological Analysis was used. Four voice-recorded focus groups were conducted and the resulting data were analysed using thematic content analysis. Five themes were identified in the data: thrown into the unknown; a worthwhile experience; a break in communication; telling the family and the community; and spreading the word. It was seen that genetic counselling cannot be viewed as a singular experience, but rather as one which is influenced by mothers' lived experiences and their interactions with other healthcare services, family and community members. The results from this study showed that genetic services and conditions were poorly understood, that the experience of genetic counselling varied amongst mothers, and on-going patient support is needed particularly when addressing family and community members. Further research is needed to assess what information is valuable to individuals during genetic counselling and how to deliver this information in a contextually appropriate manner. Greater awareness of genetic conditions is also required amongst communities and healthcare professionals. Valuable insight was gained from this study which can be used to improve local training programmes and genetic counselling services in Johannesburg, and in South Africa.

  13. Seismic expression of depositional systems tracts and application to hydrocarbon exploration in Bredasdorp basin, offshore South Africa

    SciTech Connect

    Beamish, G.W.J.

    1989-03-01

    Postrift Cretaceous sequences of Bredasdorp basin, offshore South Africa, were rigorously analyzed using the unified application of the latest seismic-stratigraphic, sequence-stratigraphic, and depositional systems concepts. Using 101 seismic profiles totaling 5600 km, the authors identified ten cyclic depositional sequences bounded by nine type 1 and two type 2 unconformities. Component depositional systems tracts exhibit a distinct seismic expression and can be delineated using truncation and lap-out relationships. Lowstand systems tracts developed on type 1 unconformities, which resulted from relative sea level fall below the shelf edge. In a terrigenous clastic basin such as Bredasdorp, these tracts are interpreted as being composed of basin-floor turbidite fans, channels, and/or sheets. These features formed contemporaneously with the erosion of incised valleys and submarine canyons, followed by channelized slope fans and deltaic/coastal lowstand wedges that prograded during a relative sea level rise. Subsequent flooding of the shelf as relative sea level rise accelerated resulted in poorly defined transgressive systems tracts. With the relative sea level at a highstand, extensively developed deltaic/coastal systems prograded basinward exhibiting well-defined clinoforms. The major hydrocarbon plays in the lowstand tracts occur as mounded basin-floor turbidite fans, channel fills, and draped sheets and are found in the updip pinch-out of deltaic/coastal sandstones.

  14. Overview of Results from the Endeavour Seismic Tomography Experiment

    NASA Astrophysics Data System (ADS)

    Toomey, D. R.; Hooft, E. E.; Wilcock, W. S.; Weekly, R. T.; Wells, A. E.; Soule, D. C.

    2011-12-01

    We report on our continuing analyses of a multi-scale seismic tomography experiment of the Endeavour segment of the Juan de Fuca Ridge. In August 2009 we deployed 68 four-component ocean bottom seismometers (OBSs) at 64 sites throughout a 90x50 km2 area to record seismic energy from 5567 shots of the 36-element, 6600 in.3 airgun array of the R/V Marcus G. Langseth. The experimental geometry utilized 3 nested scales and was designed to image (1) crustal thickness variations within 25 km of the axial high (0 to 900 kyr); (2) the map view heterogeneity and anisotropy of the topmost mantle beneath the spreading axis; (3) the three-dimensional structure of the crustal magmatic system and (4) the detailed three-dimensional, shallow crustal thermal structure beneath the Endeavour vent fields. The 90-km-long Endeavour segment lies between the Cobb and Endeavour overlapping spreading centers (OSCs), which are converging and thus shortening the Endeavour segment. Previous seismic reflection studies indicate that the central Endeavour segment is on a 40-km-wide plateau of greater crustal thickness that is interpreted to have developed when the ridge overrode the mantle melt anomaly associated with the Heckle seamount chain. The central Endeavour is also underlain by an axial magma chamber (AMC) reflector that is shallowest and most prominent beneath the hydrothermal fields. Geophysical studies of Endeavour thus permit investigation of the competing effects of tectonic, magmatic and hydrothermal processes on crustal structure and architecture. Ongoing analyses include tomographic inversion of first-arriving P waves that sample the upper- and mid-crustal regions, characterization of off-axis magma bodies via travel time and amplitude anomalies of crustal phases, estimation of regional-scale crustal thickness variations from analysis of PmP arrivals and imaging of mantle structure using Pn to constrain mantle flow and melt distribution [Weekly et al.; Wells et al.; Soule et al

  15. OSI Passive Seismic Experiment at the Former Nevada Test Site

    SciTech Connect

    Sweeney, J J; Harben, P

    2010-11-11

    its effectiveness for OSI purposes has yet to be determined. For this experiment, we took a broad approach to the definition of ''resonance seismometry''; stretching it to include any means that employs passive seismic methods to infer the character of underground materials. In recent years there have been a number of advances in the use of correlation and noise analysis methods in seismology to obtain information about the subsurface. Our objective in this experiment was to use noise analysis and correlation analysis to evaluate these techniques for detecting and characterizing the underground damage zone from a nuclear explosion. The site that was chosen for the experiment was the Mackerel test in Area 4 of the former Nevada Test Site (now named the Nevada National Security Site, or NNSS). Mackerel was an underground nuclear test of less than 20 kT conducted in February of 1964 (DOENV-209-REV 15). The reason we chose this site is because there was a known apical cavity occurring at about 50 m depth above a rubble zone, and that the site had been investigated by the US Geological Survey with active seismic methods in 1965 (Watkins et al., 1967). Note that the time delay between detonation of the explosion (1964) and the time of the present survey (2010) is nearly 46 years - this would not be typical of an expected OSI under the CTBT.

  16. Digital Database Development and Seismic Characterization and Calibration for the Middle East and North Africa.

    DTIC Science & Technology

    1998-02-24

    SEISMICITY IN THE AL-HOCEIMA REGION OF NORTH MOROCCO . 124 A bstract...STUDY IN MOROCCO ................................. 152 A bstract...estimated basement depth in the northern Arabian plate, studied recordings of earthquake and chemical explosion characteristics in Morocco , and

  17. Drought Monitoring and Forecasting: Experiences from the US and Africa

    NASA Astrophysics Data System (ADS)

    Sheffield, Justin; Chaney, Nate; Yuan, Xing; Wood, Eric

    2013-04-01

    Drought has important but very different consequences regionally due to differences in vulnerability. These differences derive from variations in exposure related to climate variability and change, sensitivity of local populations, and coping capacity at all levels. Managing the risk of drought impacts relies on a variety of measures to reduce vulnerability that includes forewarning of drought development through early-warning systems. Existing systems rely on a variety of observing systems from satellites to local observers, modeling tools, and data dissemination methods. They range from sophisticated state-of-the-art systems to simple ground reports. In some regions, systems are virtually non-existent due to limited national capacity. This talk describes our experiences in developing and implementing drought monitoring and seasonal forecast systems in the US and sub-Saharan Africa as contrasting examples of the scientific challenges and user needs in developing early warning systems. In particular, early warning can help improve livelihoods based on subsistence farming in sub-Saharan Africa; whist reduction of economic impacts is generally foremost in the US. For the US, our national drought monitoring and seasonal forecast system has been operational for over 8 years and provides near real-time updates on hydrological states at ~12km resolution and hydrological forecasts out to 9 months. Output from the system contributes to national assessments such as from the NOAA Climate Prediction Center (CPC) and the US National Drought Monitor (USDM). For sub-Saharan Africa, our experimental drought monitoring system was developed as a translation of the US system but presents generally greater challenges due to, for example, lack of ground data and unique user needs. The system provides near real-time updates based on hydrological modeling and satellite based precipitation estimates, and has recently been augmented by a seasonal forecast component. We discuss the

  18. US Geological Survey begins seismic ground response experiments in Washington State

    USGS Publications Warehouse

    Tarr, A.C.; King, K.W.

    1988-01-01

    This article briefly describes the experimental monitoring of minor seismic features caused by distant nuclear explosions, mining blasts and rhythmic human pushing against wooden homes. Some means of response prediction are outlined in Washington State and some effects of seismic amplification by weak clayey sediments are described. The results of several experiments are described. -A.Scarth

  19. Africa.

    ERIC Educational Resources Information Center

    Martz, Carlton

    2001-01-01

    This publication explores issues related to Africa. It examines the U.S. response to the Barbary pirate states (Morocco, Algiers, Tunis, Tripoli) in the early 19th century; the current AIDS crisis in Africa; and 14th century Mali and other Islamic lands through the eyes of Ibn Battuta, who traveled throughout the Muslim world. Each article…

  20. Africa.

    ERIC Educational Resources Information Center

    Happel, Sue; Loeb, Joyce

    Although the activities in this unit are designed primarily for students in the intermediate grades, the document's text, illustrations, and bibliographic references are suitable for anyone interested in learning about Africa. Following a brief introduction and map work, the document is arranged into six sections. Section 1 traces Africa's history…

  1. Simulation of Seismic Tunnel Detection Experiments in Heterogeneous Geological Media

    NASA Astrophysics Data System (ADS)

    Sherman, C. S.; Glaser, S. D.; Rector, J.

    2013-12-01

    Detecting covert tunnels and other underground openings is an important yet challenging problem for geophysicists, especially where geological heterogeneity is pronounced. A number of geophysical methods have been employed to solve this problem, each with varying degrees of success. We focus on the near-surface seismic techniques of surface wave backscattering, surface wave attenuation tomography, body wave diffraction imaging, and resonant imaging. We use the elastodynamic wave propagation code E3D to simulate tunnel detection experiments completed at this site for a range of synthetic fractal velocity models. The Black Diamond mine, located near Pittsburg California, is used for the field test of our analysis. Our results show that for the relatively low-frequency surface wave attenuation and backscattering methods, the maximum detectable tunnel depth in a homogenous medium is approximately equal to the wavelength of the probing Rayleigh wave. The higher-frequency body wave diffraction and resonant imaging techniques are able to locate tunnels at greater depths, but require more sophisticated analysis and are prone to greater attenuation losses. As is expected, for large values of heterogeneity amplitude, ɛ, the percent standard deviation from the mean velocity model, the average observed surface wave attenuation signal decreases and the maximum detectable tunnel depth decreases. However, for moderate values of heterogeneity amplitude (ɛ < 3%), the average surface wave attenuation signal increases and the maximum detectable tunnel depth increases. For the body wave diffraction and resonant imaging experiments, as ɛ increases the complexity of the observed signal increases, resulting in more difficult processing and interpretation. The additional scattering attenuation tends to degrade the signals significantly due to their reliance on lower amplitude and higher frequency waves.

  2. The seismicity in Kenya (East Africa) for the period 1906-2010: A review

    NASA Astrophysics Data System (ADS)

    Mulwa, J. K.; Kimata, F.; Suzuki, S.; Kuria, Z. N.

    2014-01-01

    Kenya has had a seismic station since 1963 as part of the World Wide Standardized Seismograph Network (WWSSN). In 1990, the University of Nairobi in collaboration with GeoForschungsZentrum (GFZ) started to build up a local seismological network, the Kenya National Seismic Network (KNSN), which operated for about ten years between 1993-2002. This, however, experienced a myriad of problems ranging from equipment breakdown, vandalism and lack of spares. Kenya is seismically active since the Kenya rift valley traverses through the country from north to south bisecting the country into eastern and western regions. In the central part, the Kenya rift branches to form the NW-SE trending Kavirondo (Nyanza) rift. The Kenya rift valley and the Kavirondo (Nyanza) rift are the most seismically active where earthquakes of local magnitude (Ml) in the order of ⩽2.0-5.0 occur. Furthermore, historical records show that earthquakes of magnitudes of the order of Ml ⩾ 6.0 have occurred in Kenya. Such large magnitude earthquakes include the January 6, 1928 Subukia earthquake (Ml 7.1) and an aftershock (Ml 6.2) four days later, as well as the 1913 Turkana region earthquake (Ml 6.2). Since early 1970's, numerous seismic investigations have been undertaken in Kenya in order to understand the formation and structure of the Kenyan part of the East African rift valley. Earthquake data from these studies is, however, rather disorganized and individual datasets, including that acquired during the period 1993-2002, cannot furnish us with comprehensive information on the seismicity of Kenya for the past ∼100 years. The purpose of this paper is, therefore, to review the seismicity in Kenya for the period 1906-2010 by utilizing data and results from different sources. The general seismicity of Kenya has been evaluated using historical data, data recorded by local seismic networks, the United States Geological Survey catalogue as well as earthquake data from the numerous seismic

  3. Recent seismic activity of the Kivu Province, Western Rift Valley of Africa

    NASA Astrophysics Data System (ADS)

    Zana, N.; Kamba, M.; Katsongo, S.; Janssen, Th.

    1989-11-01

    The Kivu Province is located at the junction between the well-defined Ruzizi Valley to the south and the Lake Amin Trough to the north. In this zone, the Rift Valley is characterized by the highest uplift and by complex dislocations of the crust, accompanied by the most intensive volcanism of the East African Rift System. In this paper, we show the recent state of the seismic activity of this zone in connection with the seismic activity generated by the volcanoes Nyiragongo and Nyamuragira. The pattern of cumulative energy release by these volcanoes shows a steplike increase that is believed to be a precursor of volcanic eruptions.

  4. Evidence for bathymetric control on the distribution of body wave microseism sources from temporary seismic arrays in Africa

    NASA Astrophysics Data System (ADS)

    Euler, Garrett G.; Wiens, Douglas A.; Nyblade, Andrew A.

    2014-06-01

    Microseisms are the background seismic vibrations mostly driven by the interaction of ocean waves with the solid Earth. Locating the sources of microseisms improves our understanding of the range of conditions under which they are generated and has potential applications to seismic tomography and climate research. In this study, we detect persistent source locations of P-wave microseisms at periods of 5-10 s (0.1-0.2 Hz) using broad-band array noise correlation techniques and frequency-slowness analysis. Data include vertical component records from four temporary seismic arrays in equatorial and southern Africa with a total of 163 broad-band stations and deployed over a span of 13 yr (1994-2007). While none of the arrays were deployed contemporaneously, we find that the recorded microseismic P waves originate from common, distant oceanic bathymetric features with amplitudes that vary seasonally in proportion with extratropical cyclone activity. Our results show that the majority of the persistent microseismic P-wave source locations are within the 30-60º latitude belts of the Northern and Southern hemispheres while a substantially reduced number are found at lower latitudes. Variations in source location with frequency are also observed and indicate tomographic studies including microseismic body wave sources will benefit from analysing multiple frequency bands. We show that the distribution of these source regions in the North Atlantic as well as in the Southern Ocean correlate with variations in bathymetry and ocean wave heights and corroborate current theory on double-frequency microseism generation. The stability of the source locations over the 13-yr time span of our investigation suggests that the long-term body wave microseism source distribution is governed by variations in the bathymetry and ocean wave heights while the interaction of ocean waves has a less apparent influence.

  5. Bandung seismic experiment: Towards tomographic imaging by using ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Pranata, Bayu; Yudistira, Tedy; Saygin, Erdinc; Cummins, Phil R.; Widiyantoro, Sri; Zulfakriza, Nugraha, Andri D.

    2016-05-01

    Bandung is one of the most densely populated cities in Indonesia with vital infrastructures. On the other hand, this area is surrounded by potential sources of earthquakes that make Bandung vulnerable to earthquakes. Structure of seismic velocity and sediment thickness are crucially needed in the earthquake hazard reduction program for Bandung. Based on this consideration, we deployed 64 seismic stations over the Bandung basin to record seismic ambient noise. In this study, we employed a cross-correlation method to the simultaneously recorded data to retrieve interstation Green's functions. We measured group velocity of the retrieved Green's functions by using frequency-time analysis technique. By the end of this project, the set of interstation group velocity will be inverted to image the shallow seismic velocity structure of the Bandung basin and its surrounding areas including Mt. Tangkuban Parahu and Lembang fault. As the first stage of this work, currently we focus on Green ' s function calculation as well as the interstation group velocity measurements. The general characteristics of group velocity can be evaluated from the plot of cross-correlation function as a function of its interstation distance.

  6. Local seismic events in area of Poland based on data from PASSEQ 2006-2008 experiment

    NASA Astrophysics Data System (ADS)

    Polkowski, Marcin; Plesiewicz, Beata; Wiszniowski, Jan; Wilde-Piórko, Monika; Passeq Working Group

    2014-05-01

    PASSEQ 2006-2008 (Passive Seismic Experiment in TESZ; Wilde-Piórko et al, 2008) was the biggest so far passive seismic experiment in the area of Central Europe (Poland, Germany, Czech Republic and Lithuania). 196 seismic stations (including 49 broadband seismometers) worked simultaneously for over two years. During experiment multiple types of data recorders and seismometers were used making analysis more complex and time consuming. Dataset was unified and repaired to start the detection of local seismic events. Two different approaches for detection were applied for stations located in Poland. One used standard STA/LTA triggers (Carl Johnson's STA/LTA algorithm) and grid search to classify and locate events. Result was manually verified. Other approach used Real Time Recurrent Network (RTRN) detection (Wiszniowski et al, 2014). Both methods gave similar results showing four previously unknown seismic events located in area of Gulf Of Gdańsk in southern Baltic Sea. The investigation of local seismicity is a good opportunity for verification of new seismic models of lithosphere in the area. In this paper we discuss both detection methods with their pros and cons (accuracy, efficiency, manual work required, scalability). We also show details of all detected and previously unknown events in discussed area. This work was partially supported by NCN grant UMO-2011/01/B/ST10/06653.

  7. Risk equalisation and voluntary health insurance: The South Africa experience.

    PubMed

    McLeod, Heather; Grobler, Pieter

    2010-11-01

    South Africa intends implementing major reforms in the financing of healthcare. Free market reforms in private health insurance in the late 1980s have been reversed by the new democratic government since 1994 with the re-introduction of open enrolment, community rating and minimum benefits. A system of national health insurance with income cross-subsidies, risk-adjusted payments and mandatory membership has been envisaged in policy papers since 1994. Subsequent work has seen the design of a Risk Equalisation Fund intended to operate between competing private health insurance funds. The paper outlines the South African health system and describes the risk equalisation formula that has been developed. The risk factors are age, gender, maternity events, numbers with certain chronic diseases and numbers with multiple chronic diseases. The Risk Equalisation Fund has been operating in shadow mode since 2005 with data being collected but no money changing hands. The South African experience of risk equalisation is of wider interest as it demonstrates an attempt to introduce more solidarity into a small but highly competitive private insurance market. The measures taken to combat over-reporting of chronic disease should be useful for countries or funders considering adding chronic disease to their risk equalisation formulae.

  8. High Resolution Near Surface 3D Seismic Experiments: A Carbonate Platform vs. a Siliciclastic Sequence

    NASA Astrophysics Data System (ADS)

    Filippidou, N.; Drijkoningen, G.; Braaksma, H.; Verwer, K.; Kenter, J.

    2005-05-01

    Interest in high-resolution 3D seismic experiments for imaging shallow targets has increased over the past years. Many case studies presented, show that producing clear seismic images with this non-evasive method, is still a challenge. We use two test-sites where nearby outcrops are present so that an accurate geological model can be built and the seismic result validated. The first so-called natural field laboratory is located in Boulonnais (N. France). It is an upper Jurassic siliciclastic sequence; age equivalent of the source rock of N. Sea. The second one is located in Cap Blanc,to the southwest of the Mallorca island(Spain); depicting an excellent example of Miocene prograding reef platform (Llucmajor Platform); it is a textbook analog for carbonate reservoirs. In both cases, the multidisciplinary experiment included the use of multicomponent and quasi- or 3D seismic recordings. The target depth does not exceed 120m. Vertical and shear portable vibrators were used as source. In the center of the setups, boreholes were drilled and Vertical Seismic Profiles were shot, along with core and borehole measurements both in situ and in the laboratory. These two geologically different sites, with different seismic stratigraphy have provided us with exceptionally high resolution seismic images. In general seismic data was processed more or less following standard procedures, a few innovative techniques on the Mallorca data, as rotation of horizontal components, 3D F-K filter and addition of parallel profiles, have improved the seismic image. In this paper we discuss the basic differences as seen on the seismic sections. The Boulonnais data present highly continuous reflection patterns of extremenly high resolution. This facilitated a high resolution stratigraphic description. Results from the VSP showed substantial wave energy attenuation. However, the high-fold (330 traces ) Mallorca seismic experiment returned a rather discontinuous pattern of possible reflectors

  9. Study of Local Seismic Events in Lithuania and Adjacent Areas Using Data from the PASSEQ Experiment

    NASA Astrophysics Data System (ADS)

    Janutyte, Ilma; Kozlovskaya, Elena; Motuza, Gediminas

    2013-05-01

    The territory of Lithuania and adjacent areas of the East European Craton have always been considered a region of low seismicity. Two recent earthquakes with magnitudes of more than 5 in the Kaliningrad District (Russian Federation) on 21 September 2004 motivated re-evaluation of the seismic hazard in Lithuania and adjacent territories. A new opportunity to study seismicity in the region is provided by the PASSEQ (Pasive Seismic Experiment) project that aimed to study the lithosphere-asthenosphere structure around the Trans-European Suture Zone. Twenty-six seismic stations of the PASSEQ temporary seismic array were installed in the territory of Lithuania. The stations recorded a number of local and regional seismic events originating from Lithuania and adjacent areas. This data can be used to answer the question of whether there exist seismically active tectonic zones in Lithuania that could be potentially hazardous for critical industrial facilities. Therefore, the aim of this paper is to find any natural tectonic seismic events in Lithuania and to obtain more general view of seismicity in the region. In order to do this, we make a manual review of the continuous data recorded by the PASSEQ seismic stations in Lithuania. From the good quality data, we select and relocate 45 local seismic events using the well-known LocSAT and VELEST location algortithms. In order to discriminate between possible natural events, underwater explosions and on-shore blasts, we analyse spatial distribution of epicenters and temporal distribution of origin times and perform both visual analysis of waveforms and spectral analysis of recordings. We show that the relocated seismic events can be grouped into five clusters (groups) according to their epicenter coordinates and origin and that several seismic events might be of tectonic origin. We also show that several events from the off-shore region in the Baltic Sea (at the coasts of the Kaliningrad District of the Russian Federation) are

  10. Deep seismic exploration into the Arctic Lithosphere: Arctic-2012 Russian wide-angle seismic experiment

    NASA Astrophysics Data System (ADS)

    Kashubin, S.

    2013-12-01

    Integrated geological and geophysical studies of the Earth's crust and upper mantle (the Russian project 'Arctic-2012') were carried out in 2012 in the Mendeleev Rise, central Arctic. The set of studies included wide-angle seismic observations along the line crossing the Mendeleev Rise in its southern part. The DSS seismic survey was aimed at the determination of the Mendeleev Rise crust type. A high-power air gun (120 liters or 7320 cu.in) and ocean stations with multi-component recording (X, Y, Z geophone components and a hydrophone) were used for the DSS. The line was studied using a dense system of observation: bottom station spacing was from 10 to 20 km, excitation point spacing (seismic traces interval) was 315 m. Observation data were obtained in 27 location points of bottom stations, the distance between the first and the last stations was 480 km, the length of the excitation line was 740 km. In DSS wave fields, in the first and later arrivals, there are refracted and reflected waves associated with boundaries in the sedimentary cover, with the top of the basement, and with boundaries in the consolidated crust, including its bottom (Moho discontinuity). The waves could be traced for offsets up to 170-240 km. The DSS line coincides with the near-vertical CMP line worked out with the use of a 4500-m-long seismic streamer and with a 50 m shot point interval that allowed essential detalization of the upper part of the section and taking it into account in the construction of a deep crust model. The deep velocity model was constructed using ray-trace modeling of compressional, shear, and converted waves with the use of the SeisWide program. Estimates were obtained for Vp/Vs velocity ratios, which played an important role in determining the type of crust. The results of the interpretation show that the Mendeleev Rise section corresponds to sections of a thin continental crust of shelf seas and a thinned continental crust of submarine ridges and rises.

  11. Seismic discrimination between earthquakes and explosions in the Middle East and North Africa

    SciTech Connect

    Walter, W.R.; Harris, D.B.; Myers, S.C.

    1997-07-01

    The recently signed Comprehensive Test Ban Treaty provides for an international network of primary and auxiliary seismic monitoring stations (IMS) to verify its compliance. Calibration is required to confidently use these stations to identify and discriminate between earthquakes, mine-related events and clandestine nuclear explosions, particularly for small to moderate seismic events recorded regionally at only a few stations. Given the lack of regional recordings of underground nuclear tests in most of the world, we are making use of mining and industrial explosions to test discriminants. For example we use the Multimax compiled dataset of small earthquakes and quarry explosions in Israel to test regional discriminants at local distances with mixed results. Further complicating calibration is the fact that many INK sites have not yet been installed and others have very short operating histories. When IMS data is available, there is often a lack of independent information (ground truth ) on the seismic sources. Here we describe a procedure for calibrating stations with limited data and apply it to the IMS auxiliary station MDT in Morocco. Data was initially available for three months in 1990 when MDT was operated as part of MEDNET. An event detector was run over the continuous data and regional events identified and roughly located using S-P time and back azimuth. The procedure uses spatial and temporal clustering to identify ''known'' mine blasts. The spatial clustering is done using the waveform correlation technique of Harris (1991) to find events with similar sources and locations. Temporal clustering looks at the time of day and repetition in time of events with the mine blasts occurring during working hours and days repeatedly over a period of time. A set of ''known'' earthquakes is also determined using location, time of day, distribution in time and size criteria. With these independent libraries of identified seismic events, we evaluate promising regional

  12. The WALPASS - Walvis Ridge Passive-Source Seismic Experiment in Namibia

    NASA Astrophysics Data System (ADS)

    Heit, B.; Yuan, X.; Geissler, W.; Lushetile, B.; Weber, M.; Jokat, W.

    2012-04-01

    The Etendeka continental flood-basalt province in northern Namibia, linked by the Walvis Ridge to the Tristan da Cunha hotspot, has a great importance in global plate tectonic concepts, and is an ideal place to understand the roll of the plume-lithosphere interaction during the break-up of the Southern Atlantic Ocean. Within this frame we are operating an amphibian passive-source seismic network (WALPASS) at the position, where the Walvis Ridge intersects with the continental margin of northern Namibia. The broadband seismic network is composed of 28 three-component land stations and 12 ocean-bottom stations, and will be operating for two year. This configuration of stations will allow us to map the lithospheric and deeper upper mantle structure in the ocean-continent transition beneath the passive continental margin of northern Namibia and to find seismic anomalies related to the postulated hotspot track from the continent to the ocean along the Walvis Ridge. The acquired should help us to study the velocity anomaly in the lowermost mantle caused by the Africa super plume and to improve the distribution of seismicity in this geophysically little studied region. We present here some receiver function results in the first attempt to map the lithosphere and the upper mantle in an area known to be the place of a plume/flood basalt province that has the potential to unravel the impact of a continental break-up in the lower crust and mantle lithosphere.

  13. Integrated application of gravity and seismic methods for determining the dip angle of a fault plane: Case of Mahjouba fault (Central Tunisian Atlas Province, North Africa)

    NASA Astrophysics Data System (ADS)

    Gabtni, H.; Hajji, O.; Jallouli, C.

    2016-07-01

    A procedure for a dip angle determination of a fault plane from gravity field data is presented to constrain a seismic profile interpretation. This procedure is applied on Mahjouba normal fault at the western border of Kalaa Khesba graben (Central Tunisian Atlas Province, North Africa). Seismic and detailed gravity data, in this region, were analyzed to provide more constraints on the geometry of the fault dip angle. The Mahjouba fault is mapped as three major parallel lineaments extended for 2 km with a NW-SE to N-S trend. The dip of the Mahjouba fault is estimated from the gravity modeling data to be 45°E. This study reveals that integrating gravity and seismic data provides accurate mapping of faults geometry and such result provides useful information and constraints on the exploration of natural resources.

  14. A New Generation of Large Seismic Refraction Experiments in Central Europe (1997-2003)

    NASA Astrophysics Data System (ADS)

    Guterch, A.; Grad, M.; Spicak, A.; Brueckl, E.; Hegedus, E.; Keller, G. R.; Thybo, H.

    2003-12-01

    Beginning in 1997, Central Europe has been covered by an unprecedented network of seismic refraction experiments. These experiments (POLONAISE'97, CELEBRATION 2000, ALP 2002, SUDETES 2003) have only been possible due a massive international cooperative effort. The total length of all profiles is about 19,000 km, and over 300 explosive sources were employed. The result is a network of seismic refraction profiles that extends along the Trans-European Suture Zone region of Poland and the Bohemian massif, Pannonian basin, trough the Carpathians and Alps to the Adriatic Sea and the Dinarides. As reflected in structures within these areas, Central Europe has experienced a complex tectonic history that includes the Caledonian, Variscan, and Alpine orogenies. The related TESZ region is a broad zone of deformation that extends across Europe from British Isles to the Black Sea region that formed as Europe was assembled from a complex collage of terranes during the late Palaeozoic. For example, the Bohemian massif is mostly located in the Czech Republic and is a large, complex terrane whose origin can be traced to northern Gondwana (Africa). These terranes were accreted along the margin of Baltica that was formed during the break-up of Rodinia. The tectonic evolution of this region shares many attributes with the Appalachian/Ouachita origin and is certainly of global important to studies in terrane tectonics and continental evolution. In southern Poland, several structural blocks are located adjacent to Baltica and were probably transported laterally along it similar to the Cenozoic movement of terranes along the western margin of North America. The younger Carpathian arc and Pannonian back-arc basin were also targeted by these experiments. Thickness of the crust in the area of investigations changes from 22-25 km in the Pannonian basin to about 55 km in the Trans-European Suture Zone in SE Poland. Together, these experiments are providing an unprecedented 3-D image of the

  15. Mathematics Registers in Indigenous Languages: Experiences from South Africa

    ERIC Educational Resources Information Center

    Schafer, Marc

    2010-01-01

    Through reporting on an initiative in South Africa that aimed to provide epistemological access to teachers and learners of mathematics (and science) through translating mathematical concepts into two indigenous languages, this paper argues for the urgent development of mathematical registers in indigenous languages for mathematics and …

  16. A Comparison of Seismicity Characteristics and Fault Structure Between Stick-Slip Experiments and Nature

    NASA Astrophysics Data System (ADS)

    Goebel, T. H. W.; Sammis, C. G.; Becker, T. W.; Dresen, G.; Schorlemmer, D.

    2015-08-01

    Fault zones contain structural complexity on all scales. This complexity influences fault mechanics including the dynamics of large earthquakes as well as the spatial and temporal distribution of small seismic events. Incomplete earthquake records, unknown stresses, and unresolved fault structures within the crust complicate a quantitative assessment of the parameters that control factors affecting seismicity. To better understand the relationship between fault structure and seismicity, we examined dynamic faulting under controlled conditions in the laboratory by creating saw-cut-guided natural fractures in cylindrical granite samples. The resulting rough surfaces were triaxially loaded to produce a sequence of stick-slip events. During these experiments, we monitored stress, strain, and seismic activity. After the experiments, fault structures were imaged in thin sections and using computer tomography. The laboratory fault zones showed many structural characteristics observed in upper crustal faults, including zones of localized slip embedded in a layer of fault gouge. Laboratory faults also exhibited a several millimeter wide damage zone with decreasing micro-crack density at larger distances from the fault axis. In addition to the structural similarities, we also observed many similarities between our observed distribution of acoustic emissions (AEs) and natural seismicity. The AEs followed the Gutenberg-Richter and Omori-Utsu relationships commonly used to describe natural seismicity. Moreover, we observed a connection between along-strike fault heterogeneity and variations of the Gutenberg-Richter b value. As suggested by natural seismicity studies, areas of low b value marked the nucleation points of large slip events and were located at large asperities within the fault zone that were revealed by post-experimental tomography scans. Our results emphasize the importance of stick-slip experiments for the study of fault mechanics. The direct correlation of

  17. Large-N Seismic Deployment at the Source Physics Experiment (SPE) Site

    NASA Astrophysics Data System (ADS)

    Chen, T.; Snelson, C. M.; Mellors, R. J.; Pitarka, A.

    2015-12-01

    The Source Physics Experiment (SPE) is multi-institutional and multi-disciplinary project that consists of a series of chemical explosion experiments at the Nevada National Security Site. The goal of SPE is to understand the complicated effect of earth structures on source energy partitioning and seismic wave propagation, develop and validate physics-based monitoring, and ultimately better discriminate low-yield nuclear explosions from background seismicity. Deployment of a large number of seismic sensors is planned for SPE to image the full 3-D wavefield with about 500 three-component sensors and 500 vertical component sensors. This large-N seismic deployment will operate near the site of SPE-5 shot for about one month, recording the SPE-5 shot, ambient noise, and additional controlled-sources. This presentation focuses on the design of the large-N seismic deployment. We show how we optimized the sensor layout based on the geological structure and experiment goals with a limited number of sensors. In addition, we will also show some preliminary record sections from deployment. This work was conducted under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy.

  18. Deltas of the Lake Malawi rift, east Africa: Seismic expression and exploration implications

    SciTech Connect

    Scholz, C.A.

    1995-11-01

    High-resolution, air-gun-sourced seismic reflection surveys over the offshore regions of five river deltas in Lake Malawi in the East African rift system reveal considerable variability in acoustic facies and stratigraphic architecture. This variability can largely be attributed to the influences of different structural settings, and to a lesser degree to high-amplitude (100-400 m) and high-frequency (1000 to 100,000 yr) fluctuations in lake level. Deltas on flexural and axial margins in the rift lake show well-developed progradational geometries. In contrast, a delta on a steep, accommodation zone margin distributes coarse sediments over a broad depositional apron, rather than concentrating sediment in discrete progradational lobes as on the other deltas. A large border fault margin river delta displays the most complex tectonic and stratigraphic architecture of all the deltas studied. It contains several delta-associated facies, including prograding clinoform packages, fan deltas stacked against a boundary fault, and extensive subaqueous fans. Flexural margin lowstand deltas may be the most prospective for hydrocarbon exploration due to their large, internally well-organized, progradational lobes and their close proximity to deep-water, high total organic carbon lacustrine source facies.

  19. An induced seismicity experiment across a creeping segment of the Philippine Fault

    NASA Astrophysics Data System (ADS)

    Prioul, R.; Cornet, F. H.; Dorbath, C.; Dorbath, L.; Ogena, M.; Ramos, E.

    2000-06-01

    The location of seismicity induced by forced fluid flow provides information about domains of pore pressure variation, while changes in fluid content are identified through changes in seismic velocity. These effects have been investigated in the geothermal field of Tongonan, which lies on a creeping portion of the Philippine Fault on Ley te Island. Locally, the left-lateral strike-slip Philippine Fault branches out into three subparallel segments (Eastern, Central and Western Fault Lines). In June-July 1997, a water stimulation was undertaken in a well that intersects the Central Fault Line 1980 m below ground surface; 36,000 m3 were injected between the casing shoe at 1308 m and the well bottom at 2177 m. The seismicity was monitored with a surface station network of 18 stations. More than 400 events, induced by the injection experiment as well as by routine injections associated with the geothermal field exploitation, were recorded in the vicinity of the well. They have been located through a simultaneous three-dimensional (3-D) velocity-hypocenter inversion procedure. None of the microearthquakes are located along the Central Fault Line, they all occurred below the casing shoe to the east of the fault line, i.e., within the geothermal reservoir and mostly below the bottom of the well. Results from the injection experiment and the 18 months of seismic monitoring along the Central and West Fault Lines suggest an aseismic behavior of this major continental fault at this location. The 3-D velocity model, determined from the travel time inversion for seismic events observed during injections, is compared to that obtained from seismic monitoring conducted prior to any injection activities. An increase of P wave velocity is observed during the water injection. This velocity increase is localized within the seismicity cloud and is interpreted as an increase in liquid content within the initial liquid-vapor multiphase part of the reservoir.

  20. Seismic evidence for the layered mantle lithosphere: a comparsion between Zagros and South Africa

    NASA Astrophysics Data System (ADS)

    Sodoudi, Forough; Kind, Rainer

    2014-05-01

    Recent S receiver function studies present evidence for the existence of the layered mantle lithosphere beneath ancient cratons. However, the nature of these layers is still unclear. They can be attributed to the presence of accumulated melts, remnants of subduction interfaces, changes in anisotropic properties or fluids. Further characterization of these layers is needed to provide more insights into the assembly and evolution of cratons. Here we compare the mantle lithosphere of the ancient Kalahari craton with the relatively young mantle lithosphere of Zagros, which is assumed as the location of the future craton. We applied the S receiver function method to map the internal layering of the lithosphere and to image its lower limit. For this aim, we used teleseismic events recorded at 97 seismic stations within the Kalahari craton and those recorded at 61 permanent seismic stations in Iran. Our results reveal a thick and stratified mantle lithosphere beneath the Kalahari craton containing three significant negative velocity contrasts at 85, 150-200, and 260-280 km depth. Moreover, they imply that frozen-in anisotropy as well as notable compositional variations can lead to sharp Mid-Lithospheric Discontinuities (MLD) that can be clearly observed in the SRF data. We show that a 50 km thick anisotropic layer just below the Moho boundary with 3% S wave anisotropy may be responsible for producing a MLD at 85 km depth. The horizontal anisotropy in the upper lithosphere may be attributed to processes during the formation of the Kalahari Craton. Furthermore, significant correlation between the depths of an apparent boundary separating the depleted and metasomatised lithosphere, as inferred from chemical tomography, and those of our second layer led us to characterize it as a compositional boundary, most likely due to the modification of the cratonic mantle lithosphere by magma infiltration. The largest velocity contrast (3.6-4.7%) is observed at a boundary located at

  1. The BOrborema Deep Electromagnetic and Seismic (BODES) Experiment

    NASA Astrophysics Data System (ADS)

    Julià, J.; Garcia, X.; Medeiros, W. E.; Farias do Nascimento, A.

    2015-12-01

    The Borborema Province of NE Brazil is a large Precambrian domain of the Brazilian shield located in the Northeasternmost corner of South America. It is bounded by the Parnaíba basin to the West and by the São Francisco craton to the South. Its structuration in the Precambrian has been related to compressional processes during the Brasiliano-Pan African orogeny (600-550 Ma). In the Mesozoic, extensional stresses eventually leading to continental breakup, left a number of aborted rift basins within the Province. After continental breakup, the evolution of the Province was marked by episodes of uplift, which might have been coeval with episodes of Cenozoic volcanism. The most prominent expression of those uplift processes is the Borborema Plateau, an elliptically shaped topographic feature in the eastern half of the Province with maximum elevations of ~1200 m. The origin of uplift in the Plateau has been the focus of a number of multi-institutional and multi-disciplinary studies in the past few years, which have imaged the deep structure of the eastern Province with unprecedented detail. The origin of uplift in the western Province, which includes a superb example of basin inversion demonstrated by the ~1000 km elevations of the Chapada do Araripe, however, has been seldom investigated. With the goal of investigating the deep structure of the western Province, a temporary network of 10 collocated seismic and magnetotelluric stations was deployed in the region. The collocated stations were arranged in an approximately NS direction, with an interspation spacing of ~70 km and spanning a total length of ~600 km. The seismic stations consisted of broadband sensors (RefTek 151B-120 "Observer") sampling at 100 Hz and were deployed in January 2015; the MT stations consisted of long-period magnetotelluric (LEMI) systems, sampling at 1 Hz and 4 Hz, and were deployed in April 2015 for a period of ~2 weeks. Preliminary results based on teleseismic P-wave receiver functions

  2. Seismic structure of the Rivera subduction zone - the MARS experiment

    NASA Astrophysics Data System (ADS)

    Grand, S. P.; Yang, T.; Sudharja, S.; Wilson, D.; Guzman Speziale, M.; Gomez Gonzalez, J.; Leon-Soto, G.; Ni, J.; Dominguez Reyes, T.

    2007-05-01

    The subduction zone of western Mexico is a unique region on Earth where microplate capture and overriding plate disruption are occurring today. The small Rivera plate is subducting beneath western most Mexico primarily beneath Jalisco state while to the east it is the Cocos plate that is subducting. Above the Rivera plate the Jalisco block of Mexico is bounded by the north trending Colima Rift and the northwest trending Tepic-Chapala Rift and may form a microplate in its own right. Magmatism is present throughout the region and is unusual for a subduction zone in that geochemical analyses indicate an ocean island basalt component to some of the lavas. Also, Colima volcano is offset trenchward from other volcanoes in the Mexican Volcanic Belt. Little is known of the subducting Rivera plate geometry due to the paucity of seismicity within the plate yet the geometry of the Rivera and Cocos plates at depth are likely critical for understanding the tectonic evolution of western Mexico. The MARS (MApping the Rivera Subduction zone) project consists of the deployment of 50 broadband seismometers covering the Jalisco block from the coast to the Tepic-Chapala rift in the north and about 150 km to the west of the Colima rift. The instruments were deployed in January, 2006 and will be removed in June, 2007. The goal of the project is to seismically image the subducting Rivera and Cocos plates at depth as well as the mantle wedge above the plates. A number of different analyses of MARS data are underway including teleseismic tomography, receiver function analysis, and shear wave splitting analysis. The preliminary tomography results clearly show both subducting plates with a sharp change in dip to the east of the Colima rift probably indicating a tear between the two plates along a trend more eastward than the trend of the rift. The images also show extremely slow shallow mantle velocities beneath the Tepic-Chapala rift but not beneath the Colima rift. Receiver functions

  3. Local Knowledge and Experiences of Vaccination: Implications for HIV-Preventive Vaccine Trials in South Africa

    ERIC Educational Resources Information Center

    Lindegger, Graham; Quayle, Michael; Ndlovu, Moses

    2007-01-01

    This study forms part of the preparation of communities for HIV-preventive vaccine trials in South Africa. On the basis of the assumption that attitudes to any HIV vaccine or vaccine trials will partly be influenced by experiences of vaccination in general, this study aimed to investigate knowledge of, attitudes to, and experiences of vaccination…

  4. Unearthing White Academics' Experience of Teaching in Higher Education in South Africa

    ERIC Educational Resources Information Center

    Jawitz, Jeff

    2016-01-01

    The real and imagined racial differences and similarities between groups of students and staff have consequences in everyday experiences in South Africa. One aspect of engaging with the challenges facing higher education transformation post-Apartheid is through understanding how the racialized context interacts with the experience of teaching.…

  5. Shallow Seismic Imaging of an Oil Field Using Broadband Data: LaBarge Experiment

    NASA Astrophysics Data System (ADS)

    Biryol, C. B.; Leahy, G. M.; Zandt, G.; Beck, S. L.; Saltzer, R. L.; Lewallen, K. T.

    2011-12-01

    The frequency content of the broadband seismic records makes them a suitable candidate for frequency based analysis of the Earth's shallow crustal structure. Frequency band dependent analysis and inversion of Pg- and Pn-wave travel-time residuals from regional/local earthquakes can yield valuable information on the shallow seismic structure of the crust. Hence, we investigate the shallow crustal seismic structure beneath the LaBarge oil production field in western Wyoming. We picked and inverted Pg- and Pn-wave travel-times from regional/local earthquakes in multiple frequency bands. Our dataset is composed of travel-time observations from 55 densely spaced (250m) broadband seismic stations of the LaBarge Experiment array. These stations were deployed in LaBarge, WY, between November 2008-June 2009 and recorded continuously with a sampling rate of 100 samples-per-second. We used arrival-time residuals from approximately 90 regional earthquakes located between the distances of 1.8° - 3.5° and 120 local earthquakes located closer than 1.8° from the LaBarge array. This yielded over 35,000 observations of relative travel-time residuals summed over all of the analyzed frequency bands. The results of our analysis consistently yielded negative relative residual times (-0.05 seconds) in all frequency bands for the stations in the NW branch of the network indicating presence of seismically faster structures beneath this region. We observe that the residuals gradually increase towards the eastern branch of the array (up to 0.1 seconds) where major structural boundaries are transected. The results of various inversions consistently indicated the presence of a seismically faster structural anomaly underlying the western branch of the array at depths between 3 and 5 km. In general, our results indicate that frequency dependent analyses of broadband data can be used to resolve the shallow seismic structure of the upper-crust within a spatially limited region.

  6. Imaging the deep seismic structure beneath a mid-ocean ridge: the MELT experiment

    PubMed

    1998-05-22

    The Mantle Electromagnetic and Tomography (MELT) Experiment was designed to distinguish between competing models of magma generation beneath mid-ocean ridges. Seismological observations demonstrate that basaltic melt is present beneath the East Pacific Rise spreading center in a broad region several hundred kilometers across and extending to depths greater than 100 kilometers, not just in a narrow region of high melt concentration beneath the spreading center, as predicted by some models. The structure of the ridge system is strongly asymmetric: mantle densities and seismic velocities are lower and seismic anisotropy is stronger to the west of the rise axis.

  7. An Idea for an Active Seismic Experiment on Mars in 2008

    NASA Technical Reports Server (NTRS)

    Lognonne, Ph.; Banerdt, B.; Giardini, D.; Costard, F.

    2001-01-01

    The detection of liquid water is of prime interest and should have deep implications in the understanding of the Martian hydrological cycle and also in exobiology. In the frame of the 2007 joint CNES-NASA mission to Mars, a set of 4 NETLANDERS developed by an European consortium is expected to be launched in June 2007. We propose to use a second spacecraft going or landing to Mars to release near one of the Netlander a series of artificial metallic meteorites, in order to perform an active seismic experiment providing a seismic profile of the crust and subsurface.

  8. Impact of Petrophysical Experiments on Quantitative Interpretation of 4D Seismic Data at Ketzin, Germany

    NASA Astrophysics Data System (ADS)

    Ivanova, A.; Lueth, S.

    2015-12-01

    Petrophysical investigations for CCS concern relationships between physical properties of rocks and geophysical observations for understanding behavior of injected CO2 in a geological formation. In turn 4D seismic surveying is a proven tool for CO2 monitoring. At the Ketzin pilot site (Germany) 4D seismic data have been acquired by means of a baseline (pre-injection) survey in 2005 and monitor surveys in 2009 and 2012. At Ketzin CO2 was injected in supercritical state from 2008 to 2013 in a sandstone saline aquifer (Stuttgart Formation) at a depth of about 650 m. The 4D seismic data from Ketzin reflected a pronounced effect of this injection. Seismic forward modeling using results of petrophysical experiments on two core samples fromthe target reservoir confirmed that effects of the injected CO2 on the 4D seismic data are significant. The petrophysical data were used in that modeling in order to reflect changes due to the CO2 injection in acoustic parameters of the reservoir. These petrophysical data were further used for a successful quantitative interpretation of the 4D seismic data at Ketzin. Now logs from a well (drilled in 2012) penetrating the reservoir containing information about changes in the acoustic parameters of the reservoir due to the CO2 injection are available. These logs were used to estimate impact of the petrophysical data on the qualitative and quantitative interpretation of the 4D seismic data at Ketzin. New synthetic seismograms were computed using the same software and the same wavelet as the old ones apart from the only difference and namely the changes in the input acoustic parameters would not be affected with any petrophysical experiments anymore. Now these changes were put in computing directly from the logs. In turn the new modelled changes due to the injection in the newly computed seismograms do not include any effects of the petrophysical data anymore. Key steps of the quantitative and qualitative interpretation of the 4D seismic

  9. Pre-instrumental seismicity in Central Africa using felt seisms recorded mainly at the meteorological stations of DRC, Rwanda and Burundi during the colonial period

    NASA Astrophysics Data System (ADS)

    Mulumba, J.-L.; Delvaux, D.

    2012-04-01

    Seismic hazard assessment and mitigation of catastrophes are primarily based on the identification and characterization of seismically active zones. These tasks still rely heavily on the existing knowledge of the seismic activity over the longest possible time period. The first seismic network in Equatorial Africa (IRSAC network) was operated from the Lwiro scientific base on the western shores of Lake Kivu between 1953 and 1963. Before this installation, the historical record of seismic activity in Central Africa is sparse. Even for the relatively short period concerned, spanning only 50-60 years, the historical record is far from being complete. A first attempt has been made by Herrinckx (1959) who compiled a list 960 felt seisms recorded at the meteorological stations between 1915 and 1954 in Congo, Rwanda and Burundi. They were used to draw a density map of felt seisms per square degree. We completed this data base by exploiting the meteorological archives and any available historical report to enlarge the database which now reaches 1513 entries between 1900 and 1959. These entries have been exanimate in order to identify possible historical seismic events. Those are defined by 3 or more quasi-simultaneous records observed over a relatively short distance (a few degrees of latitude/longitude) within a short time difference (few hours). A preliminary list of 115 possible historical seisms has been obtained, identified by 3 to 15 different stations. The proposed location is taken as the average latitude and longitude of the stations where the felt seisms were recorded. Some of the most important ones are associated to aftershocks that have been felt at some stations after the main shocks. The most recent felt seisms have been also recorded instrumentally, which helps to validate the procedure followed. The main difficulties are the magnitude estimation and the possible spatial incompleteness of the recording of felt seism evidence at the margin of the observation

  10. Passive seismic monitoring of hydraulic fracture experiments at the Multiwell Experiment site

    SciTech Connect

    Thorne, B.J.; Morris, H.E.

    1988-08-01

    Redesign of hardware, software, and data-reduction techniques associated with the Sandia National Laboratories' Borehole Seismic System (BSS) have made possible better estimates of hydraulic fracture geometry at the Multiwell Experiment (MWX) site. The redesigned system now incorporates four geophones per axis and provides up to 112 dB of downhole gain, for 100 times the sensitivity of the original system. Improved signal-to-noise ratios, extended frequency response and increased digitization rates have made possible the acquisition and processing of data which were previously inaccessible. A maximum likelihood event location scheme, which incorporates an algorithm based on the use of spherical statistics, is used to compute the location of microseismic events and error estimates for these locations. Accuracy estimates for the redesigned system, based on the ability to locate perforation shots, indicates a 25 ft (7.6 m) uncertainty in the location of individual microseismic events using data from two BSS receivers. This resulted in a high level of confidence in determination of the azimuth of the November 1, 1986, hydraulic fracture in the Fluvial B sandstone. A reasonable determination of the azimuth, propped wing length and height for the September 23, 1987, hydraulic fracture in the Fluvial E sandstone was possible using data from only one BSS receiver. 15 refs., 32 figs., 6 tabs.

  11. Martian Ambient Seismic Noise: from the first modeling to the future data of the InSight Seismic experiment.

    NASA Astrophysics Data System (ADS)

    Lognonne, P. H.; Banerdt, W. B.; Mimoun, D.; Kobayashi, N.; Panning, M. P.; Pike, W. T.; Giardini, D.; Christensen, U. R.; Nishikawa, Y.; Murdoch, N.; Kawamura, T.; Kedar, S.; Spiga, A.

    2014-12-01

    The InSight NASA Discovery mission is expected to deploy a 3 axis VBB and a 3 axis SP seismometer on Mars by late september 2016. This seismic station will explore the Martian ambient noise, in addition to more classical science goals related to the detection of Marsquakes, Meteoritic Impacts and Tides. Mars, in contrast with the Earth (with both atmosphere and ocean) and the Moon (with no atmosphere nor ocean) is expected to have ambient noise only related to its atmosphere. Mars seismic data are therefore expecting to reveal the atmospheric coupling for a different atmospheric dynamics than Earth, especially in the 0.1-1 Hz bandwidth, dominated by oceanic microseisms on Earth. We rapidly present the expected performances of the SEIS experiment onboard InSight. This experiment is based on two 3 axis seismometers, one covering the tide and low seismic frequencies (up to 10 Hz) and a second one covering the high frequencies (from 0.1 Hz to 50 Hz). Both sensors are mounted on a sensors plateform, deployed by a robotic arm 1-2 meters from the lander and covered by thermal protection and a wind protection. The expected performances indicates that signal as low as 10**(-9) m/s**2/Hz**(1/2) will be detected in the 0.005-2 Hz bandwidth. We then focus on the modeling of this ambient atmospheric noise.This modeling has been done not only from constraints gathered by the atmospheric sensors of previous Mars missions (e.g. Viking and Pathfinder) but also by numerical modeling of the atmospheric perturbations, both at global scale and mesoscale. Theoretical estimation of the ambient noise has then been obtained for the pressure-correlated surface loading and the stochastic excitation of surface waves, at both long and very long period (e.g. Mars hum) and at medium or short period (e.g. regional and local generated surface waves). Results shows that most of these source of ambient noise will be detected, likely during the day for those generated locally and possibly during the

  12. The Millikan shaking experiments and high-frequency seismic wave propagation in Southern California

    NASA Astrophysics Data System (ADS)

    Tanimoto, Toshiro; Okamoto, Taro

    2014-08-01

    In order to study high-frequency seismic wave propagation, seismic wavefields generated by resonant-shaking experiments of the Millikan Library, on the campus of California Institute Technology (Pasadena, California, USA), were analysed. Because the resonant shaking frequencies are 1.12 Hz (the east-west direction) and 1.64 Hz (the north-south direction), this active-source experiment can provide opportunities for studying high-frequency seismic wave propagation in Southern California. Because they are very narrow frequency band data, the analyses must be quite different from ordinary time-domain analyses. We show, theoretically, that the signals must be dominated by surface waves. Adopting this surface wave assumption, we proceed to make two separate analyses, one on spectral amplitude and the other on phase. We present a new method to derive group velocity from phase based on the cross correlations between the station in the Millikan Library (MIK) and stations in the regional network. Our results support that an active-source experiment by resonant shaking of a building is a feasible approach for high-frequency seismic wave studies.

  13. Caregiver experience in mental illness: a perspective from a rural community in South Africa.

    PubMed

    Mavundla, Thandisizwe R; Toth, Ferenc; Mphelane, Makua L

    2009-10-01

    After the democratization of South Africa in 1994, the health-care system was reorganized in accordance with the primary health-care philosophy advocated by the World Health Organization. This was accompanied by a process of deinstitutionalization of mental health-care services, which has led families to become the main providers of care to individuals with mental illness. This study explores the experiences of informal family caregivers of persons with mental illness in a rural area in South Africa. Data were collected through eight individual semistructured interviews of informal caregivers who cared for relatives with mental illness and collect medications monthly at a community clinic in the Makhuduthamaga local municipality in Limpopo, South Africa. A qualitative research design was used, which was explorative, descriptive, and contextual. The data analysis revealed four major themes: (i) experiences of providing for physiological/physical needs; (ii) experiences of providing for emotional needs; (iii) experiences of providing for security needs; and (iv) experiences associated with the medical health-care programme. The study revealed that the experiences of family caregivers were conceptualized negatively, although the interview questions were intentionally neutral. This is believed to be due to the cultural explanatory models of mental illness prevalent in this region of South Africa. It is suggested that to increase compliance with medication, reduce relapse, and mitigate stigma associated mental illness, medical professionals need to incorporate aspects of cultural explanatory models into their explanations of the causes of illness.

  14. Capacity development for health research in Africa: experiences managing the African Doctoral Dissertation Research Fellowship Program

    PubMed Central

    2010-01-01

    Africa's progress depends on her capacity to generate, adapt, and use scientific knowledge to meet regional health and development needs. Yet, Africa's higher education institutions that are mandated to foster this capacity lack adequate resources to generate and apply knowledge, raising the need for innovative approaches to enhance research capacity. In this paper, we describe a newly-developed program to support PhD research in health and population sciences at African universities, the African Doctoral Dissertation Research Fellowship (ADDRF) Program. We also share our experiences implementing the program. As health research capacity-strengthening in Africa continues to attract attention and as the need for such programs to be African-led is emphasized, our experiences in developing and implementing the ADDRF offer invaluable lessons to other institutions undertaking similar initiatives. PMID:20587016

  15. Seismic images of the Brooks Range fold and thrust belt, Arctic Alaska, from an integrated seismic reflection/refraction experiment

    USGS Publications Warehouse

    Levander, A.; Fuis, G.S.; Wissinger, E.S.; Lutter, W.J.; Oldow, J.S.; Moore, T.E.

    1994-01-01

    We describe results of an integrated seismic reflection/refraction experiment across the Brooks Range and flanking geologic provinces in Arctic Alaska. The seismic acquisition was unusual in that reflection and refraction data were collected simultaneously with a 700 channel seismograph system deployed numerous times along a 315 km profile. Shot records show continuous Moho reflections from 0-180 km offset, as well as numerous upper- and mid-crustal wide-angle events. Single and low-fold near-vertical incidence common midpoint (CMP) reflection images show complex upper- and middle-crustal structure across the range from the unmetamorphosed Endicott Mountains allochthon (EMA) in the north, to the metamorphic belts in the south. Lower-crustal and Moho reflections are visible across the entire reflection profile. Travel-time inversion of PmP arrivals shows that the Moho, at 33 km depth beneath the North Slope foothills, deepens abruptly beneath the EMA to a maximum of 46 km, and then shallows southward to 35 km at the southern edge of the range. Two zones of upper- and middle-crustal reflections underlie the northern Brooks Range above ~ 12-15 km depth. The upper zone, interpreted as the base of the EMA, lies at a maximum depth of 6 km and extends over 50 km from the range front to the north central Brooks Range where the base of the EMA outcrops above the metasedimentary rocks exposed in the Doonerak window. We interpret the base of the lower zone, at ~ 12 km depth, to be from carbonate rocks above the master detachment upon which the Brooks Range formed. The seismic data suggest that the master detachment is connected to the faults in the EMA by several ramps. In the highly metamorphosed terranes south of the Doonerak window, the CMP section shows numerous south-dipping events which we interpret as a crustal scale duplex involving the Doonerak window rocks. The basal detachment reflections can be traced approximately 100 km, and dip southward from about 10-12 km

  16. Structure of the Crust and Mantle Lithosphere underneath NW Namibia Revealed by the WALPASS Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Yuan, X.; Jokat, W.; Weber, M. H.; Geissler, W.; Heit, B.; Eken, T.; Pandey, S.; Lushetile, B.; Hoffmann, K.

    2013-12-01

    The amphibian Walvis Ridge Passive-Source Seismic Experiment (WALPASS) have been operated for a period of two years from 2010 to 2012 in the area where the Walvis Ridge intersects the continental margin of northwestern Namibia. The deployment was intended to study the lithospheric and upper mantle structure in the ocean-continent transition area beneath the passive continental margin. The main idea is to find seismic anomalies related to the postulated hotspot track from the continent to the ocean along the Walvis Ridge that links the Etendeka continental flood-basalt province to the Tristan da Cunha hotspot in the mid Atlantic ocean. This could provide clues of the role of plume-lithosphere interaction during the continental break-up. We present here seismic structures of the crustal and mantle lithosphere in this geophysically little studied region using seismic methods including P and S receiver functions and shear wave splitting. The average crustal thickness in the continental Namibia is ~35 km with a relatively low Vp/Vs ratio of 1.7. Underneath the NE extension of the Walvis Ridge the crust is the thickest (45 km) with a high Vp/Vs ratio (>1.80). The thick crust and high Vp/Vs ratio beneath the Walvis Ridge are consistent with high Vp derived by controlled source seismics, implying a magmatic underplating. A low velocity zone in the mantle is observed at depths of 60-120 km, possibly representing the base of the lithosphere. The P-to-S converted phases at the 410 and 660 km discontinuities arrive 2-3 s earlier, indicating higher upper mantle velocities (+5%). Seismic anisotropy in the mantle derived by the SKS splitting exhibits a pattern of the plume and plate interaction.

  17. Advancing Explosion Source Theory through Experimentation: Results from Seismic Experiments Since the Moratorium on Nuclear Testing

    NASA Astrophysics Data System (ADS)

    Bonner, J. L.; Stump, B. W.

    2011-12-01

    On 23 September 1992, the United States conducted the nuclear explosion DIVIDER at the Nevada Test Site (NTS). It would become the last US nuclear test when a moratorium ended testing the following month. Many of the theoretical explosion seismic models used today were developed from observations of hundreds of nuclear tests at NTS and around the world. Since the moratorium, researchers have turned to chemical explosions as a possible surrogate for continued nuclear explosion research. This talk reviews experiments since the moratorium that have used chemical explosions to advance explosion source models. The 1993 Non-Proliferation Experiment examined single-point, fully contained chemical-nuclear equivalence by detonating over a kiloton of chemical explosive at NTS in close proximity to previous nuclear explosion tests. When compared with data from these nearby nuclear explosions, the regional and near-source seismic data were found to be essentially identical after accounting for different yield scaling factors for chemical and nuclear explosions. The relationship between contained chemical explosions and large production mining shots was studied at the Black Thunder coal mine in Wyoming in 1995. The research led to an improved source model for delay-fired mining explosions and a better understanding of mining explosion detection by the International Monitoring System (IMS). The effect of depth was examined in a 1997 Kazakhstan Depth of Burial experiment. Researchers used local and regional seismic observations to conclude that the dominant mechanism for enhanced regional shear waves was local Rg scattering. Travel-time calibration for the IMS was the focus of the 1999 Dead Sea Experiment where a 10-ton shot was recorded as far away as 5000 km. The Arizona Source Phenomenology Experiments provided a comparison of fully- and partially-contained chemical shots with mining explosions, thus quantifying the reduction in seismic amplitudes associated with partial

  18. Successful Experiences in Non-Formal Education and Alternative Approaches to Basic Education in Africa.

    ERIC Educational Resources Information Center

    Thompson, Ekundayo J. D.

    This document profiles 10 successful experiences in nonformal education (NFE) programs across Africa. Common features of the programs profiled are as follows: (1) provide educational opportunities for those who have missed out on formal education; (2) show evidence of learners' acquisition of competencies for work and survival; (3) demonstrate…

  19. Enhancing Critical Consciousness through a Cross-Cultural Immersion Experience in South Africa

    ERIC Educational Resources Information Center

    Choi, Kyoung Mi; VanVoorhis, Richard W.; Ellenwood, Audrey E.

    2015-01-01

    Using phenomenological approaches, the author explored the meanings and essences of a cross-cultural immersion experience in South Africa among counseling master's-level students. Five core themes--the meaning of being American, sociopolitical awareness, engagement with South Africans and their communities, appreciation of life, and commitment to…

  20. Experiences of School Principals with Newcomers from War-Affected Countries in Africa

    ERIC Educational Resources Information Center

    Okoko, Janet Mola

    2011-01-01

    This article is based on the results of an exploratory study of experiences of 2 urban school principals about leading schools with immigrants from war-affected countries in Africa. It examines how they perceived their preparation for multicultural leadership, and explores lessons that leadership development institutions can learn from their…

  1. Experiences of Master's Students Regarding Clinical Supervision in an Applied Psychology Programme in South Africa

    ERIC Educational Resources Information Center

    Nel, Lindi; Fouche, Paul

    2017-01-01

    This study explored and described the experiences regarding clinical supervision of master's students in professional psychology programmes in South Africa. Four participants were purposively selected from four different universities. The participants engaged in reflective writings and in-depth interviews over a one-year span. Data were analysed…

  2. What Does an Inventory of Recent Innovation Experiences Tell Us about Agricultural Innovation in Africa?

    ERIC Educational Resources Information Center

    Triomphe, Bernard; Floquet, Anne; Kamau, Geoffrey; Letty, Brigid; Vodouhe, Simplice Davo; Ng'ang'a, Teresiah; Stevens, Joe; van den Berg, Jolanda; Selemna, Nour; Bridier, Bernard; Crane, Todd; Almekinders, Cornelia; Waters-Bayer, Ann; Hocde, Henri

    2013-01-01

    Purpose: Within the context of the European-funded JOLISAA project (JOint Learning in and about Innovation Systems in African Agriculture), an inventory of agricultural innovation experiences was made in Benin, Kenya and South Africa. The objective was to assess multi-stakeholder agricultural innovation processes involving smallholders. Approach:…

  3. Indigenizing Civic Education in Africa: Experience in Madagascar and the Sahel

    ERIC Educational Resources Information Center

    Antal, Carrie; Easton, Peter

    2009-01-01

    In Africa, as in many countries of the South, democratization is sometimes perceived as a process modeled upon outside--and specifically Northern--experience. Formal civic education programs in those countries arguably reflect the same bias and have not always been notably successful. Yet there are rich patterns of civic involvement and democratic…

  4. Characterization of granular flows from seismic signal: insights from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Farin, M.; Mangeney, A.; Toussaint, R.; de Rosny, J.

    2015-12-01

    Landslides, rock avalanche and debris flows represent a major natural hazard in steep landscapes. Recent studies showed that the seismic signal generated by these events can provide quantitative information on their location and amplitude. However, owing to the lack of visual observations, the dynamics of gravitational events is still not well understood. A burning challenge is to establish relations between the characteristics of the landslide (volume, speed, runout distance,...) and that of the emitted seismic signal (maximum amplitude, seismic energy, frequencies,...) Laboratory experiments of granular columns collapse are conducted on an inclined plane. The seismic signal generated by the collapse is recorded by piezoelectric accelerometers sensitive in a wide frequency range (1 Hz - 56 kHz). The granular column is constituted with steel beads of same diameter, between 1 mm and 3 mm that are initially contained in a cylinder. The column collapses when the cylinder is removed. A layer of steel beads is glued on the surface of the plane to provide basal roughness. For horizontal granular flows, we show that it is possible to distinguish the phases of acceleration and deceleration of the flow in the emitted seismic signal. Indeed, the signal envelope is symmetrical with respect to its maximum, separating the acceleration from the deceleration. When the slope angle increases, we observe that the signal envelope looses its symmetry: it stays unchanged during the acceleration but it is significantly extended during the deceleration. In addition, we propose a semi-empirical scaling law to describe the increase of the elastic energy radiated by a granular flow when the slope angle increases. The fit of this law with the seismic data allows us to retrieve the friction angle of the granular material, which is a crucial rheological parameter. Finally, we show that the ratio of the radiated elastic energy over the potential energy lost of granular flows, i.e. their seismic

  5. Re-evaluation of Apollo 17 Lunar Seismic Profiling Experiment data

    NASA Astrophysics Data System (ADS)

    Heffels, Alexandra; Knapmeyer, Martin; Oberst, Jürgen; Haase, Isabel

    2017-01-01

    We re-analyzed Apollo 17 Lunar Seismic Profiling Experiment (LSPE) data to improve our knowledge of the subsurface structure of this landing site. We use new geometrically accurate 3-D positions of the seismic equipment deployed by the astronauts, which were previously derived using high-resolution images by Lunar Reconnaissance Orbiter (LRO) in combination with Apollo astronaut photography. These include coordinates of six Explosive Packages (EPs) and four geophone stations. Re-identified P-wave arrival times are used to calculate two- and three-layer seismic velocity models. A strong increase of seismic velocity with depth can be confirmed, in particular, we suggest a more drastic increase than previously thought. For the three-layer model the P-wave velocities were calculated to 285, 580, and 1825 m/s for the uppermost, second, and third layer, respectively, with the boundaries between the layers being at 96 and 773 m depth. When compared with results obtained with previously published coordinates, we find (1) a slightly higher velocity (+4%) for the uppermost layer, and (2) lower P-wave velocities for the second and third layers, representing a decrease of 34% and 12% for second and third layer, respectively. Using P-wave arrival time readings of previous studies, we confirm that velocities increase when changing over from old to new coordinates. In the three-layer case, this means using new coordinates alone leads to thinned layers, velocities rise slightly for the uppermost layer and decrease significantly for the layers below.

  6. Crust structure across the Rif Cordillera from 'RIFSIS' seismic refraction and wide-angle reflection experiment

    NASA Astrophysics Data System (ADS)

    Gil, Alba; Gallart, Josep; Díaz, Jordi; Carbonell, Ramon; Harnafi, Mimoun; Levander, Alan

    2013-04-01

    The Rif Cordillera, located in North Morocco forms, together with the Betic Range, the Gibraltar Arc around the Alboran Sea. This asymmetric curved mountain belt originated during a Miocene continent-continent collision as a result of the westward motion of the Alboran domain between northwest Africa and Iberia. The complexity of the area favored the proposition of diverse tectonic models, such as roll-back, accompanied and followed by lithospheric convective down-welling, and delamination. In this study, we present models of crustal structure derived from a seismic refraction and wide-angle reflection experiment which took place in October 2011 within the Spanish project RIFSIS complemented by the US-PICASSO one. Two profiles oriented N-S and E-W respectively were carried out across the Rif domains. Five shots of 1 Tn each were detonated along the lines and at the crossing point, recorded by about 900 stations from US-Iris pool deployed at an average spacing of 750 m. The N-S line was extended northwards by a 70 km long segment in Spain, in the Betic Range. Southwards, this profile connects with the one recorded in 2010 across the Atlas Mountains, within the SIMA project. The interpreted crustal structure differentiates two sedimentary layers on top of the basement, inferred from the observed first arrivals at short offsets, followed by upper, mid and lower crustal levels constrained by reflected phases visible in the record sections. The bottom of the crust is well defined from PmP phases, although the absence of Pn arrivals prevents to constrain upper mantle velocities. Average velocity values for the different layers in the models are respectively: 3.5 and 4.2 km/s for the sediments, 5.9, 6.3 and 6.6 km/s within the crust, and 8 km/s below Moho. These velocity depth models obtained at the Rif Cordillera hold major variations in crustal thickness, especially along the E-W profile, that shows a rapid change of 15-20 km in Moho depths within 30 km horizontal

  7. 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.

  8. Thermo-Mechanical Modeling of Seismic Cycle and Quaternary Deformation of the Asal Rift, Djibouti, Africa: Implication for the Rheology of the Lithosphere

    NASA Astrophysics Data System (ADS)

    Cattin, R.; de Chabalier, J.; King, G.; Vigny, C.; Avouac, J.; Ruegg, J.

    2001-12-01

    Because it is subaerial, the Asal rift in the Afar depression of Djibouti provides an exceptional opportunity to study the mechanics of active rifting. Horizontal extension and vertical displacements have been deduced from the deformation of ~ 100,000 yr old volcano that had formed across the rift zone. Over the three last decades seismic, geodetic and field observations have been performed in this region. Over this period major seismovolcanic crisis occurred in 1978. This unique set of data provides information on long term, co-seismic, post-seismic and inter-seismic deformation that might be used to infer the mechanical properties of the rift zone. In that respect the data are compared with the results of a thermo-mechanical modeling. We compute the thermal structure and deformation separately. The temperature field, computed from a finite difference scheme of heat conduction in a moving medium, is adjusted to fit data of 6 thermal wells. Deformation is computed from a two-dimensional finite element model (ADELI) that was modified for the purpose of this study. We conducted several sets of experiments, varying rheological parameters and boundary conditions, in which a section of lithosphere is submitted to 17-20 mm/yr horizontal spreading. Our modeling reconciles all data on seismic cycle and quaternary deformation. The following questions will be tackle: what is the range of viscosity associated with ductile flow in lithosphere? What is the effect of plasticity? What is the contribution of tectonics and volcanism to rifting processes?

  9. Configuration of geological domains and geodynamic evolution of the Africa-Eurasia plate boundary off SW Iberia revisited based on seismic velocity and density models

    NASA Astrophysics Data System (ADS)

    Martínez-Loriente, Sara; Sallarès, Valentí; Gràcia, Eulàlia; Bartolome, Rafael; Ranero, César

    2015-04-01

    We present a new classification of geological (basement) domains at the Africa-Eurasia plate boundary offshore SW Iberia, together with a regional geodynamic reconstruction spanning from the Mesozoic extension to the Neogene-to-present-day convergence. It is based on seismic velocity and density models along two regional wide-angle seismic transects, one running NW-SE from the Tagus to the Seine abyssal plains, and the other running N-S from S Portugal to the Seine Abyssal Plain, combined with previously available information. The seismic velocity and density structure at the Seine Abyssal Plain and the internal Gulf of Cadiz indicates the presence of a highly heterogeneous oceanic crust, similar to that described in ultra-slow spreading centers, whereas in the Horseshoe and Tagus abyssal plains, the basement structure resembles that of exhumed mantle sections identified in the Northern Atlantic margin. The integration of all this new information allows defining the presence of three oceanic domains off SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE segment of the Central Atlantic (Early Jurassic); (2) the Gulf of Cadiz domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the Seine Abyssal Plain domain and lasted up to the North Atlantic continental break-up (Late Jurassic); and (3) the Gorringe Bank domain, mainly made of rocks exhumed from the mantle with little synchronous magmatism, which formed during the first stages of North Atlantic opening (Early Cretaceous). Our models suggest that the Seine Abyssal Plain and Gulf of Cadiz domains are separated by the Lineament South strike-slip fault, whereas the Gulf of Cadiz and Gorringe Bank domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain, which coincides with the seismicity cluster nucleated in the

  10. Seismic mapping of shallow fault zones in the San Gabriel Mountains from the Los Angeles Region Seismic Experiment, southern California

    USGS Publications Warehouse

    Fuis, G.S.; Ryberg, T.; Lutter, W.J.; Ehlig, P.L.

    2001-01-01

    During the Los Angeles Region Seismic Experiment (LARSE), a reflection/refraction survey was conducted along a profile (line 1) extending from Seal Beach, California, northeastward to the Mojave Desert and crossing the Los Angeles and San Gabriel Valley basins and San Gabriel Mountains. In most shot gathers from the southern and central San Gabriel Mountains, clear secondary arrivals are seen that merge, or appear to merge, with first arrivals at three locations, including the location of the Vincent thrust fault, an exposed late Mesozoic/early Cenozoic megathrust. These secondary arrivals are interpretable as reflections in the shallow crust (<5 km depth) from a concave-upward interface that projects to the surface in the north near the Vincent thrust fault, is offset in its central part at the San Gabriel fault (an old branch of the San Andreas fault), and terminates in the south at 1 to 2 km depth at the southern mountain front. The velocity structure above and below this interface strongly suggests it is the Vincent thrust fault: intermediate velocities (6.2 km/s), consistent with mylonites overlying the Vincent thrust fault, are observed above it; lower velocities (5.8 km/s), consistent with the Pelona Schist underlying the Vincent thrust fault, are observed below it. Problems arise, however, in attempting to match this reflector to the exposed Vincent thrust fault, which is seen in outcrops east of line 1. The Vincent thrust fault is shallower than the reflector in most places. An unmapped structure (steep fault, monocline, or thrust fault) is required between line 1 and the outcrops that either drops the Vincent thrust fault down to the depths of the reflector or repeats the Vincent thrust fault beneath line 1 in the footwall of another thrust fault. An alternative interpretation of the reflector is a deep greenstone horizon within the Pelona Schist, although this alternative is not favored by the velocity structure. Copyright 2001 by the American

  11. Caracas Seismological Museum: A space to develop an interactive experience between community and Venezuelan seismic culture.

    NASA Astrophysics Data System (ADS)

    Moreno, D.; Galindo, L.; Granado, C.

    2009-05-01

    Caracas is a city with a relative high seismic hazard. The last damaged earthquake occurred in 1967. This is a fundamental fact to favor a policy that promote a scientific popularization center having as a prime mission, to spread knowledge about earth sciences, particularly seismology. Another face of this main purpose is to educate people about how to protect themselves in case of a natural seismic event occur. We present the characteristics and social impact of an effort to create in Caracas an open and alive space able to transform a visit in a meaningful experience, stimulating the interest in the natural history, the singular geological features and promoting dialogue and reflection among the visitors as a participants in a reality where awareness about the geological risks is a need to preserved live and ensure a right attitude towards decrease vulnerability among the population. One of the highlights of this project was to recover and to restore a diverse set of obsolete instruments as well as an old construction and its surrounding area, to design a playful and recreational spot to learn about seismic culture and vulnerability reduction with the community as a protagonist of their own social evolution by means of bolstering local resilience and improving earthquake preparedness.

  12. Data report for the 1985 seismic-refraction experiment at Yucca Mountain and vicinity, southwestern Nevada

    SciTech Connect

    Sutton, V.D.

    1985-12-31

    In February 1985, the US Geological Survey (USGS) conducted a seismic-refraction survey in the vicinity of Yucca Mountain, southwestern Nevada to better define the P(compressional)-wave velocity structure of the upper crust in this area. This experiment is a continuation of seismic investigations at the Nevada Test Site (NTS) by the USGS on behalf of the Nevada Nuclear Waste Storage Investigations Project (NNWSI) to assess the feasibility of a proposed nuclear waste disposal site at Yucca Mountain. The 1985 seismic-refraction survey consisted of three separate deployments: two East-West profiles, Line A and Line B, and a North-South profile (Plate 1). Thirty-one shots were recorded by 120 portable seismographs, where recorder station spacing averaged .3 km, and the shotpoints averaged 5 to 8 km apart. Additionally, off set shots were fired at shotpoints located about 7 to 15 km from the endpoints of the deployment lines. This report includes record sections from the twenty-nine shotpoints (Plates 2 to 17), a list of seismograph locations (Appendix A), a list of shotpoint locations and shot times, DKDAT data files and Tape Grade Code (Appendix B), and a list of first-arrival traveltime picks (Appendix C). Detailed interpretation of these data will be published in a subsequent report.

  13. TOMO-ETNA MED-SUV.ISES an active seismic and passive seismic experiment at Mt. Etna volcano. An integrated marine and onland geophysical survey.

    NASA Astrophysics Data System (ADS)

    Ibáñez, Jesus. M.; Patane, Domenico; Puglisi, Guisseppe; Zuccarello, Lucciano; Bianco, Francesca; Luehr, Birger; Diaz-Moreno, Alejandro; Prudencio, Janire; Koulakov, Ivan; Del Pezzo, Edoardo; Cocina, Ornella; Coltelli, Mauro; Scarfi, Lucciano; De Gori, Pascuale; Carrion, Francisco

    2014-05-01

    An active seismic experiment to study the internal structure of Etna Volcano is going to carried out on Sicily and Aeolian islands. The main objective of the TOMO-ETNA MED-SUV.ISES experiment, beginning in summer 2014, is to perform a high resolution seismic tomography, in velocity and attenuation, in Southern Italy, by using active and passive seismic data, in an area encompassing outstanding volcanoes as Mt. Etna, and Aeolian volcanoes. The achievement of this objective is based on the integration and sharing of the in-situ marine and land experiments and observations and on the implementation of new instruments and monitoring systems. For the purpose, onshore and offshore seismic stations and passive and active seismic data generated both in marine and terrestrial environment will be used. Additionally, other geophysical data, mainly magnetic and gravimetric data will be considered to obtain a joint Upper Mantle-Crust structure that could permit to make progress in the understanding of the dynamic of the region. This multinational experiment which involves institutions from Spain, Italy, Germany, United Kingdom, Ireland, France, Malta, Portugal, Russia, USA and Mexico. During the experiment more than 6.600 air gun shots performed by the Spanish Oceanographic vessel "Sarmiento de Gamboa" will be recorder on a dense local seismic network consisting of 100 on land non-permanent stations, 70 on land permanent stations and 20-25 OBSs. Contemporaneously other marine geophysical measures will be performed using a marine Gravimeter LaCoste&Romberg Air-Sea Gravity System II and a Marine Magnetometer SeaSPY. The experiments will provide a unique data set in terms of data quantity and quality, and it will provide a detailed velocity and attenuation structural image of volcano edifice. The results will be essential in the development and interpretation of future volcanic models. It is noteworthy that this project is fully transversal, multidisciplinary and crosses several

  14. Investigation of River Seismic Signal Induced by Sediment Transport and Water Flow: Controlled Dam Breaking Experiments

    NASA Astrophysics Data System (ADS)

    Chen, H. Y.; Chen, S. C.; Chao, W. A.

    2015-12-01

    Natural river's bedload often hard to measure, which leads numerous uncertainties for us to predict the landscape evolution. However, the measurement of bedload flux has its certain importance to estimate the river hazard. Thus, we use seismometer to receive the seismic signal induced by bedload for partially fill the gap of field measurement capabilities. Our research conducted a controlled dam breaking experiments at Landao River, Huisun Forest since it has advantage to well constraining the spatial and temporal variation of bedload transport. We set continuous bedload trap at downstream riverbed of dam to trap the transport bedload after dam breaking so as to analyze its grain size distribution and transport behavior. In the meantime we cooperate with two portable velocity seismometers (Guralp CMG6TD) along the river to explore the relationship between bedload transport and seismic signal. Bedload trap was divided into three layers, bottom, middle, and top respectively. After the experiment, we analyzed the grain size and found out the median particle size from bottom to top is 88.664mm, 129.601mm, and 214.801mm individually. The median particle size of top layer is similar with the upstream riverbed before the experiment which median particle size is 230.683mm. This phenomena indicated that as the river flow become stronger after dam breaking, the sediment size will thereupon become larger, which meant the sediment from upstream will be carried down by the water flow and turned into bedload. Furthermore, we may tell apart the seismic signal induced by water flow and bedload by means of two different position seismometers. Eventually, we may estimate the probable error band of bedload quantity via accurately control of water depth, time-lapse photography, 3D LiDAR and other hydrology parameters.

  15. Passive seismic experiment. [Apollo 17 flight contributions to determining lunar structure by analyzing moonquake and meteoroid impact seismic signals

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    The network of seismometers installed by the Apollo 17 and other Apollo missions is described. The effects of the impacts of lunar modules and S-4B stages on the lunar surfaces are discussed. The information concerning lunar composition which is obtained by analyzing the seismic signals generated by moonquakes and meteoroid impacts are analyzed. It is concluded that the seismic activity within the moon is extremely low compared to that with the earth. The moon is characterized by a rigid, dynamically inactive outer shell, approximately 1000 kilometers thick, surrounding a core that has markedly different elastic properties.

  16. A Gravity data along LARSE (Los Angeles Regional Seismic Experiment) Line II, Southern California

    USGS Publications Warehouse

    Wooley, R.J.; Langenheim, V.E.

    2001-01-01

    The U.S. Geological Survey conducted a detailed gravity study along part of the Los Angeles Regional Seismic Experiment (LARSE) transect across the San Fernando Basin and Transverse Ranges to help characterize the structure underlying this area. 249 gravity measurements were collected along the transect and to augment regional coverage near the profile. An isostatic gravity low of 50-60 mGal reflects the San Fernando-East Ventura basin. Another prominent isostatic gravity with an amplitude of 30 mGal marks the Antelope Valley basin. Gravity highs occur over the Santa Monica Mountains and the Transverse Ranges. The highest isostatic gravity values coincide with outcrops of Pelona schist.

  17. Exploring tsunamis with non-traditional dataset: array recordings from temporary ocean-bottom seismic experiment

    NASA Astrophysics Data System (ADS)

    Sheehan, A. F.; Yang, Z.; Nicolsky, D.; Mungov, G.; Eakins, B.

    2011-12-01

    We observe clear tsunami signals generated by the July 15, 2009 magnitude 7.8 Dusky Sound (Fiordland) New Zealand earthquake on seafloor differential pressure gauges (DPGs). The dataset was collected during the ocean-bottom seismic experiment, Marine Observations of Anisotropy Near Aotearoa (MOANA). This experiment deployed 30 broadband ocean-bottom seismometers (Trillium 240) and differential pressure gauges (DPGs) for a year (2009/01-2010/02) both in deep ocean (greater than 4000 m water depth) and on the continental shelf (550 m to 1300 m) offshore of the South Island of New Zealand. The DPGs are used in many US National Ocean Bottom Seismograph Instrument Pool (OBSIP) experiments and are designed to record seismic signals. In this study, we demonstrate that DPGs can effectively record open-ocean tsunami signals and the tsunami signals on DPG records can be used for tsunami studies. We carry out waveform and spectral analysis for DPG data recordings of the Fiordland tsunami event. The arrival times of tsunami signals on DPG recordings can be directly used to constrain tsunami wave propagation models. We calibrate the DPGs to obtain better control on the amplitude of the tsunami signals on the DPG records. Calibrations are done over frequency bands of both Rayleigh wave and tidal signals. Synthetic pressure waveforms are calculated to be compared with the DPG recorded signals.

  18. Journey to South Africa: A Cultural Experience, Grade 7. Performance-Based Instructional Task. Fulbright-Hays Summer Seminar Abroad 1996 (South Africa).

    ERIC Educational Resources Information Center

    Giampaolo, Chloe

    This interdisciplinary two-week unit simulates a trip to South Africa as part of a U.S. delegation sent to observe what is happening politically, economically, and culturally in the post-apartheid transition. Students explore and experience a number of real-life events and situations which might be encountered on an actual trip. The tasks…

  19. Sms1: Seismic Wave Velocities Variations With Tectonic Stress From Controlled Source Experiment.

    NASA Astrophysics Data System (ADS)

    Chastin, Sebastien; Crampin, Stuart; Shear-Wave Analysis Group

    -observed relaxation in seismic velocities has been observed following seismicity. This high-resolution experiment shows a sensitivity of seismic velocity to variations in stress of the order of 10-2/bar. This is over an order of magnitude higher than sensitivity measured in laboratory experiments. These results confirm that SMS technology has the sensitivity, and resolution to carry out shear-wave splitting monitoring described in paper SMS3. Make a better instrument or measure in a place where no one else has been and a great discovery will come your way." Frank Press, 1979. EOS, 60, 30, 540.

  20. Preliminary Results from the iMUSH Active Source Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Levander, Alan; Kiser, Eric; Palomeras, Imma; Zelt, Colin; Schmandt, Brandon; Hansen, Steve; Harder, Steven; Creagar, Kenneth; Vidale, John; Abers, Geoffrey

    2015-04-01

    iMUSH (imaging Magma Under Saint Helens) is a US NSF sponsored multi-disciplinary investigation of Mount Saint Helens (MSH), currently the most active volcano in the Cascades arc in the northwestern United States. The project consists of active and passive seismic experiments, extensive magnetotelluric sounding, and geological/geochemical studies involving scientists at 7 institutions in the U.S. and Europe. The long-term goal of the seismic project is to combine analysis of the active source data with that of data from the 70 element broadband seismograph operating from summer 2014 until 2016. Combining seismic and MT analyses with other data, we hope to image the MSH volcanic plumbing system from the surface to the subducting Juan de Fuca slab. Here we describe preliminary results of the iMUSH active source seismic experiment, conducted in July and August 2014. The active source experiment consisted of twenty-three 454 or 908 kg weight shots recorded by ~3500 seismographs deployed at ~6,000 locations. Of these instruments, ~900 Nodal Seismic instruments were deployed continuously for two weeks in an areal array within 10 km of the MSH summit. 2,500 PASSCAL Texan instruments were deployed twice for five days in 3 areal arrays and 2 dense orthogonal linear arrays that extended from MSH to distances > 80 km. Overall the data quality from the shots is excellent. The seismograph arrays also recorded dozens of micro-earthquakes beneath the MSH summit and along the MSH seismic zone, and numerous other local and regional earthquakes. In addition, at least one low frequency event beneath MSH was recorded during the experiment. At this point we have begun various types of analysis of the data set: We have determined an average 1D Vp structure from stacking short-term/long-term average ratios, we have determined the 2-D Vp structure from ray-trace inversions along the two orthogonal profiles (in the NW-SE and NE-SW directions), and we have made low-fold CMP stacks of the

  1. Field Report on the iMUSH Active Source Seismic Experiment

    NASA Astrophysics Data System (ADS)

    Kiser, E.; Levander, A.; Schmandt, B.; Palomeras, I.; Harder, S. H.; Creager, K. C.; Vidale, J. E.; Malone, S. D.

    2014-12-01

    In the second half of July we completed the iMUSH active source seismic experiment, one component of the Imaging Magma Under Saint Helens project. A team of ~75 volunteers deployed 3500 seismographs to ~5920 locations on and around Mount St. Helens over the course of 3 weeks. This instrument deployment was accompanied by 23 shots distributed around the volcano. Instrumentation consisted of ~2550 Reftek 125A (Texan) seismographs with 4.5 Hz geophones, and 920 Nodal Seismic recorders with 10 Hz geophones. The shots were also recorded by the permanent stations of the Pacific Northwest Seismograph Network and 70 iMUSH broadband seismographs. Fifteen of the shots, 424 kg each, formed two rings around Mount Saint Helens at 15 km and 30 km radius from the summit. Eight of the shots, 828 kg each, were fired at distances of 50 to 80 km from MSH on NW-SE and NE-SW azimuths. The deployment geometry consisted of two lines oriented NW/SE and NE/SW, and three arrays. The offset of the lines ranged from 150 km to 190 km with an average spacing of 200 m. The first array was centered on the volcano with a radius of 30 km, and required both driving and hiking to deploy. Arrays two and three were set out with, and centered on, the NW/SE line. These arrays had a distance range from MSH of 30-75 km and an azimuth range of about 100 degrees. In addition to this large-scale deployment, we set out 7 beamforming arrays approximately collocated with iMUSH broadband seismographs, and above clusters of seismicity in the region. The aperture of these arrays was about 1 km with an instrument spacing of 100 m. The final deployment ended only days before the AGU abstract deadline, so we have not yet examined all of the data. However, the preliminary indications are that signal to noise is excellent: The shots, several of which registered on PNSN as ML>2.1, carried across the entire array, and were recorded as far away as Seattle and Corvallis on permanent stations. The array also recorded a

  2. Forest productivity and drought in tropical Africa: observations from the Global Ozone Monitoring Experiment-2

    NASA Astrophysics Data System (ADS)

    Robinson, E. S.; Lee, J. E.; Yang, X.

    2014-12-01

    The impact of seasonal water stress on Africa's tropical regions has yet to be characterized despite drought's potential to cause famine and a reduction of biodiversity across the continent. Through the analysis of a new data set of sun-induced chlorophyll fluorescence (SIF) from the Global Ozone Monitoring Experiment-2, we demonstrate that fluorescence varies with water availability, particularly over regions with distinctive wet and dry seasons. Water availability was determined via both precipitation (from the Global Precipitation Climatology Project) and daytime canopy water content measurements (from the SeaWinds Scatterometer onboard the QuickSCAT satellite). Variance in SIF values was largely explained by both canopy water content and precipitation, which paralleled one-another. When viewed in the context of the previously defined relationship between fluorescence and gross primary production (GPP) - SIF scales linearly with GPP - our results suggest that photosynthetic activity in tropical Africa is limited by water availability. The characterization of this trend is critical in defining the response of tropical ecosystems to water stress and corroborating similar relationships in other tropical regions (e.g. Amazonia). Ultimately, the viability of Africa's tropical regions amidst a changing climate is rooted in its ecosystem-wide response to water stress; the future of the African tropics is limited by how well plants cope with water stress.

  3. Archiving and Exchange of a Computerized Marine Seismic Database: The ROSE (Rivera Ocean Seismic Experiment) Data Archive System

    DTIC Science & Technology

    1983-12-01

    The participating institutions provided their data to the facility where the data were catalogued and distributed. This report describes in detail ...distributed. This report describes in detail the processes and computer programs used to catalog, store and distribute the ROSE seismic data. The...of the Data Base 1 II. The Rose Storage and Exchange Format 2 A. The Tape Header File 2 B. File Header Record and Data Structure 6 C. Shot

  4. Multichannel seismic-reflection profiling on the R/V Maurice Ewing during the Los Angeles Region Seismic Experiment (LARSE), California

    USGS Publications Warehouse

    Brocher, Thomas M.; Clayton, Robert W.; Klitgord, Kim D.; Bohannon, Robert G.; Sliter, Ray; McRaney, John K.; Gardner, James V.; Keene, J.B.

    1995-01-01

    This report describes the acquisition of deep-crustal multichannel seismic-reflection data in the Inner California Borderland aboard the R/V Maurice Ewing, conducted in October 1994 as part of the Los Angeles Regional Seismic Experiment (LARSE). LARSE is a cooperative study of the crustal structure of southern California involving earth scientists from the U.S. Geological Survey, Caltech, the University of Southern California, the University of California Los Angeles, and the Southern California Earthquake Center (SCEC). During LARSE, the R/V Ewing's 20- element air gun array, totaling 137.7 liters (8470 cu. in.), was used as the primary seismic source for wide-angle recording along three main onshore-offshore lines centered on the Los Angeles basin and the epicenters of the 1933 Long Beach and 1994 Northridge earthquakes. The LARSE onshore-offshore lines were each 200-250 km long, with the offshore portions being between 90 and 150 km long. The nearly 24,000 air gun signals generated by the Ewing were recorded by an array of 170 PASSCAL REFTEK recorders deployed at 2 km intervals along all three of the onshore lines and 9 ocean bottom seismometers (OBSs) deployed along two of the lines. Separate passes over the OBS-deployment lines were performed with a long air gun repetition rate (60 and 90 seconds) to minimize acoustic-wave interference from previous shots in the OBS data. The Ewing's 4.2-km, 160-channel, digital streamer was also used to record approximately 1250 km of 40-fold multichannel seismic-reflection data. To enhance the fold of the wide-angle data recorded onshore, mitigating against cultural and wind noise in the Los Angeles basin, the entire ship track was repeated at least once resulting in fewer than about 660 km of unique trackline coverage in the Inner Borderland. Portions of the seismic-reflection lines were repeated up to 6 times. A variety of other geophysical data were also continuously recorded, including 3.5 kHz bathymetry, multi

  5. ENAM: A community seismic experiment targeting rifting processes and post-rift evolution of the Mid Atlantic US margin

    NASA Astrophysics Data System (ADS)

    Van Avendonk, H. J.; Magnani, M. B.; Shillington, D. J.; Gaherty, J. B.; Hornbach, M. J.; Dugan, B.; Long, M. D.; Lizarralde, D.; Becel, A.; Benoit, M. H.; Harder, S. H.; Wagner, L. S.; Christeson, G. L.

    2014-12-01

    The continental margins of the eastern United States formed in the Early Jurassic after the breakup of supercontinent Pangea. The relationship between the timing of this rift episode and the occurrence of offshore magmatism, which is expressed in the East Coast Magnetic Anomaly, is still unknown. The possible influence of magmatism and existing lithospheric structure on the rifting processes along margin of the eastern U.S. was one of the motivations to conduct a large-scale community seismic experiment in the Eastern North America (ENAM) GeoPRISMS focus site. In addition, there is also a clear need for better high-resolution seismic data with shallow penetration on this margin to better understand the geological setting of submarine landslides. The ENAM community seismic experiment is a project in which a team of scientists will gather both active-source and earthquake seismic data in the vicinity of Cape Hatteras on a 500 km wide section of the margin offshore North Carolina and Virginia. The timing of data acquisition in 2014 and 2015 facilitates leveraging of other geophysical data acquisition programs such as Earthscope's Transportable Array and the USGS marine seismic investigation of the continental shelf. In April of 2014, 30 broadband ocean-bottom seismometers were deployed on the shelf, slope and abyssal plain of the study site. These instruments will record earthquakes for one year, which will help future seismic imaging of the deeper lithosphere beneath the margin. In September and October of 2014, regional marine seismic reflection and refraction data will be gathered with the seismic vessel R/V Marcus Langseth, and airgun shots will also be recorded on land to provide data coverage across the shoreline. Last, in the summer of 2015, a land explosion seismic refraction study will provide constraints on the crustal structure in the adjacent coastal plain of North Carolina and Virginia. All seismic data will be distributed to the community through IRIS

  6. A comparative study of seismicity statistics in laboratory stick-slip experiments and nature: Implications for fault mechanics

    NASA Astrophysics Data System (ADS)

    Goebel, Thomas; Kwiatek, Grzegorz; Becker, Thorsten; Sammis, Charles; Dresen, Georg

    2016-04-01

    Fault properties can rarely be monitored under in-situ conditions at seismogenic depth. At these depths seismicity records are possibly the only high-resolution data that can provide insight into state of stress and mechanics of faulting. We analyze series of laboratory experiments on faults that developed during stick-slip on saw-cut and fractured surfaces under upper crustal stress conditions. Stick-slip experiments were performed on surfaces with varying roughness and fracture surfaces that evolved into fault zones with pronounced damage zones. We monitor and analyze acoustic emission events that exhibit many striking similarities to natural seismicity across all examined scales. These similarities include pronounced Gutenberg-Richter-type magnitude distributions, Omori-type aftershock decay, and off-fault seismicity distributions that decay as a power law with distance. In the laboratory, fault roughness and heterogeneity are critical in concentrating stresses that lead to local AE clustering, and differences in off-fault activities and lower b-values. Similar observations of earthquake clustering and b-value variations were made for natural faults such as the Parkfield segment of the San Andreas fault. In addition to seismicity statistics, we conducted a detailed analysis of moment tensors, focusing on relative contributions from isotropic and deviatoric components to laboratory seismicity. In contrast to natural seismicity, our results revealed a larger contribution from isotropic components. These contributions are a result of ongoing fracture processes within the evolving fault which are most pronounced after stick-slip events. Our study shows, that seismicity analyses in laboratory experiments can significantly advance our understanding of fault mechanics from the scale of single asperities to large fault zones.

  7. The lived experiences of street children in Durban, South Africa: Violence, substance use, and resilience

    PubMed Central

    Hills, Frances; Meyer-Weitz, Anna; Asante, Kwaku Oppong

    2016-01-01

    South African studies have suggested that street children are resilient but also suicidal, engage in unprotected sex and other high risk sexual behaviour as a means of survival, have high rates of substance abuse and are physically abused and stigmatized due to their state of homelessness. However, few studies have explored in a more holistic manner the lived experiences of street children in South Africa. The main purpose of this study was to explore qualitatively the lived experiences of street children living on the street of Durban, in the province of KwaZulu-Natal, South Africa. Adolescents (six males and four females) between the ages of 14 and 18 years (average age=16) were purposively selected and in-depth semi-structured interviews were conducted. An interpretative phenomenological analysis of the transcribed data revealed that incidence of violence and drug and alcohol use were common experiences of street life. Yet despite these challenges survival was made possible through personal and emotional strength, cultural values, religious beliefs, supportive peer relationships, and participation in sports activities. These protective, resilience resources should be strengthened in health promotion interventions with a focus on mental health, the prevention of violence, substance use, and daily physical activities that seems to provide meaning and hope. PMID:27291160

  8. The lived experiences of street children in Durban, South Africa: Violence, substance use, and resilience.

    PubMed

    Hills, Frances; Meyer-Weitz, Anna; Asante, Kwaku Oppong

    2016-01-01

    South African studies have suggested that street children are resilient but also suicidal, engage in unprotected sex and other high risk sexual behaviour as a means of survival, have high rates of substance abuse and are physically abused and stigmatized due to their state of homelessness. However, few studies have explored in a more holistic manner the lived experiences of street children in South Africa. The main purpose of this study was to explore qualitatively the lived experiences of street children living on the street of Durban, in the province of KwaZulu-Natal, South Africa. Adolescents (six males and four females) between the ages of 14 and 18 years (average age=16) were purposively selected and in-depth semi-structured interviews were conducted. An interpretative phenomenological analysis of the transcribed data revealed that incidence of violence and drug and alcohol use were common experiences of street life. Yet despite these challenges survival was made possible through personal and emotional strength, cultural values, religious beliefs, supportive peer relationships, and participation in sports activities. These protective, resilience resources should be strengthened in health promotion interventions with a focus on mental health, the prevention of violence, substance use, and daily physical activities that seems to provide meaning and hope.

  9. Local Seismic Events in the Area of Poland Based on Data from the PASSEQ 2006-2008 Experiment

    NASA Astrophysics Data System (ADS)

    Polkowski, Marcin; Plesiewicz, Beata; Wiszniowski, Jan; Wilde-Piórko, Monika

    2016-12-01

    PASSEQ 2006-2008 (Passive Seismic Experiment in TESZ; Wilde-Piórko et al. 2008) was the biggest passive seismic experiment carried out so far in the area of Central Europe (Poland, Germany, the Czech Republic and Lithuania). 196 seismic stations (including 49 broadband seismometers) worked simultaneously for over two years. During the experiment, multiple types of data recorders and seismometers were used, making the analysis more complex and time consuming. The dataset was unified and repaired to start the detection of local seismic events. Two different approaches for detection were applied for stations located in Poland. The first one used standard STA/LTA triggers (Carl Johnson's STA/LTA algorithm) and grid search to classify and locate the events. The result was manually verified. The second approach used Real Time Recurrent Network (RTRN) detection (Wiszniowski et al. 2014). Both methods gave similar results, showing four previously unknown seismic events located in the Gulf of Gdańsk area, situated in the southern Baltic Sea. In this paper we discuss both detection methods with their pros and cons (accuracy, efficiency, manual work required, scalability). We also show details of all detected and previously unknown events in the discussed area.

  10. A passive seismic experiment and ground penetration radar to characterize subsurface cavities in Eastern Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Asmaidi Chan, Septriandi; Ismail Kaka, SanLinn

    2014-05-01

    We have carried out a small-scale passive seismic experiment over a known shallow cavity at King Fahd University of Petroleum & Minerals in an attempt to characterize the near surface cavities. This experiment was conducted as part of a larger study to develop an integrated geophysical approach (i.e. seismic, gravity, resistivity and ground penetration radar) in detecting and characterizing shallow subsurface cavities. Characterizing shallow cavities is of particular interest in the eastern province of Saudi Arabia where many cavities were discovered during a number of construction projects. We used a Geospace passive seismic recording system to collect continuous data over a partly dolomitized limestone bed with several fractures and cavities. Systematically selected time series data at different times of the day were processed using Geopsy software developed by the SESAME (Site Effects Assessment using Ambient Excitations) project. Data from the 10 Hz geophone was used in this experiment and we extracted part of the data recorded during the night as this has been found to exclude most of the anthropologic noise that usually masks signals on data recorded during the day time. We analyzed time series data and performed spectral analysis. Horizontal-to-vertical ratio (H/V) and power spectral density (PSD) were performed as an enhancement tool to determine the resonance frequencies possibly associated with the shallow cavity. Various processing windows with 5% cosine tapers were applied to reduce spectral leakage. To retain the analysis at frequency range of interest between 0.1 to 20 Hz, a band-pass-filter with smoothing procedure described by Kamo and Omachi (1998) was applied. Moreover, the same frequency peaks were picked at each measuring point to check the stability of the H/V curve. The preliminary results (frequency peaks in the spectral H/V ambient ground motions as well as PSD plots) do not uniquely define the near surface cavity. However, further

  11. Preliminary TEX86 temperatures and a lake level record of tropical climate extremes derived from sediment cores and seismic stratigraphy from Lake Turkana, East Africa

    NASA Astrophysics Data System (ADS)

    Morrissey, A. J.; Scholz, C. A.; Russell, J. M.

    2012-12-01

    Lake Turkana is the largest lake in the Eastern Branch of the East African Rift System and records hydrologic conditions of a region spanning nearly 2.5 degrees of latitude (~2.0 - 4.5 degrees N) in the African tropics. New data suggest the Turkana region likely experienced much wetter and cooler climate over several intervals since the latest Pleistocene. Lake level was extremely low twice during the latest Pleistocene, evidenced by depositional hiatuses in high-resolution CHIRP seismic reflection data that correlate with sediments that have low water-content, abundant sand, and low total organic carbon (TOC as low as <0.7%). Lake Turkana, like many lakes in northern tropical Africa, had a wetter climate during the African Humid Period. Intervals of high lake levels (up to ~440 m amsl) are indicated by flat-lying, laterally continuous, low-amplitude reflections that correlate in sediment cores to dark, fine-grained, laminated sediment with high TOC (up to ~6%). Calcium carbonate accumulation during this time period is nearly 0%, and combined with evidence of laminated, unbioturbated sediment suggests a fresh, stratified lake with anoxic bottom waters. During the early mid-Holocene, lake level began to fall to close to present levels (~365 m amsl). Sediments deposited during this time period have low but variable organic carbon content (~0.5 - ~2%) and are much higher in inorganic carbon (from fine-grained calcite precipitation). A moderate lowstand during the late Holocene is indicated by an erosional unconformity seen down to ~40 m below the current lake surface in several seismic profiles. This record of lake level extremes suggests highly variable rainfall patterns, forced by migration of the Intertropical Convergence Zone) across tropical East Africa over the last 20,000 years. More than 50 sediment samples from 3 piston cores represent a continuous record of TEX86 temperature from ~20,000 years ago to modern. The generally low (<0.25) BIT index for the

  12. Lattice preferred orientation of olivine found in diamond-bearing garnet peridotites in Finsch, South Africa and implications for seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Lee, Jaeseok; Jung, Haemyeong

    2015-04-01

    Seismic anisotropy in the upper mantle provides important constraints on mantle dynamics, continental evolution and global tectonics and is believed to be produced by the flow-induced lattice-preferred orientation (LPO) of olivine. Recent experimental studies at high pressure and temperature have suggested that the LPO of olivine is affected by pressure in addition to water and stress. However, there has been no report yet for the pressure-induced LPO of natural olivine because samples from the deep upper mantle are rare and often unsuitable for study due to ambiguous foliation and lineation. Here we show evidence of the pressure-induced LPO of natural olivine in diamond-bearing garnet peridotites from Finsch, South Africa. We found that the [010] axes of olivine are aligned subnormal to foliation and that the [001] axes are aligned subparallel to lineation, which is known as B-type LPO of olivine. The equilibrium pressure of the samples, as estimated using geobarometer, was greater than 4 GPa, indicating that the samples originated from a depth greater than ~120 km. In addition, FTIR spectroscopy of the olivine showed that the samples are dry, with a water content of less than 90±20 ppm H/Si (5.5±1.2 ppm wt. H2O). These data suggest that the samples are the first natural examples of olivine displaying B-type LPOs produced due to high pressure under dry condition. Our data indicate that the trench-parallel seismic anisotropy observed in many subduction zones in and below subducting slabs at depths greater than ~90 km under dry condition may be attributed to the pressure-induced olivine fabrics (B-type LPO) and may be interpreted as the entrainment of the sub-lithospheric mantle in the direction of subduction rather than anomalous trench-parallel flow.

  13. Lattice-preferred orientation of olivine found in diamond-bearing garnet peridotites in Finsch, South Africa and implications for seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Lee, Jaeseok; Jung, Haemyeong

    2015-01-01

    Seismic anisotropy in the upper mantle provides important constraints on mantle dynamics, continental evolution and global tectonics and is believed to be produced by the flow-induced lattice-preferred orientation (LPO) of olivine. Recent experimental studies at high pressure and temperature have suggested that the LPO of olivine is affected by pressure in addition to water and stress. However, there has been no report yet for the pressure-induced LPO of natural olivine because samples from the deep upper mantle are rare and often unsuitable for study due to ambiguous foliation and lineation. Here we show evidence of the pressure-induced LPO of natural olivine in diamond-bearing garnet peridotites from Finsch, South Africa. We found that the [010] axes of olivine are aligned subnormal to foliation and that the [001] axes are aligned subparallel to lineation, which is known as B-type LPO of olivine. The equilibrium pressure of the samples, as estimated using geobarometer, was greater than 4 GPa, indicating that the samples originated from a depth greater than ˜120 km. In addition, FTIR spectroscopy of the olivine showed that the samples are dry, with a water content of less than 90 ± 20 ppm H/Si (5.5 ± 1.2 ppm wt. H2O). These data suggest that the samples are the first natural examples of olivine displaying B-type LPOs produced due to high pressure under dry condition. Our data indicate that the trench-parallel seismic anisotropy observed in many subduction zones in and below subducting slabs at depths greater than ˜90 km under dry condition may be attributed to the pressure-induced olivine fabrics (B-type LPO) and may be interpreted as the entrainment of the sub-lithospheric mantle in the direction of subduction rather than anomalous trench-parallel flow.

  14. Volume estimation of rift-related magmatic features using seismic interpretation and 3D inversion of gravity data on the Guinea Plateau, West Africa

    NASA Astrophysics Data System (ADS)

    Kardell, Dominik A.

    The two end-member concept of mantle plume-driven versus far field stress-driven continental rifting anticipates high volumes of magma emplaced close to the rift-initiating plume, whereas relatively low magmatic volumes are predicted at large distances from the plume where the rifting is thought to be driven by far field stresses. We test this concept at the Guinea Plateau, which represents the last area of separation between Africa and South America, by investigating for rift-related volumes of magmatism using borehole, 3D seismic, and gravity data to run structural 3D inversions in two different data areas. Despite our interpretation of igneous rocks spanning large areas of continental shelf covered by the available seismic surveys, the calculated volumes in the Guinea Plateau barely match the magmatic volumes of other magma-poor margins and thus endorse the aforementioned concept. While the volcanic units on the shelf seem to be characterized more dominantly by horizontally deposited extrusive volcanic flows distributed over larger areas, numerous paleo-seamounts pierce complexly deformed pre and syn-rift sedimentary units on the slope. As non-uniqueness is an omnipresent issue when using potential field data to model geologic features, our method faced some challenges in the areas exhibiting complicated geology. In this situation less rigid constraints were applied in the modeling process. The misfit issues were successfully addressed by filtering the frequency content of the gravity data according to the depth of the investigated geology. In this work, we classify and compare our volume estimates for rift-related magmatism between the Guinea Fracture Zone (FZ) and the Saint Paul's FZ while presenting the refinements applied to our modeling technique.

  15. Mechanisms of seismic attenuation in the crust: Scattering and anelasticity in New York state, South Africa, and southern California

    NASA Astrophysics Data System (ADS)

    Frankel, Arthur

    1991-04-01

    The envelopes of high-frequency seismograms from earthquakes in New York State, South Africa, and southern California are analyzed to determine how much of the observed attenuation of shear waves in the crust is caused by anelasticity and how much is produced by scattering from small-scale heterogeneities. For seismograms from New York and South Africa, there is a systematic enrichment of high-frequency energy that develops in the coda relative to the direct S or Lg waves. This enrichment of high frequencies in the coda grows larger with increasing source-receiver distance. This implies that high-frequency energy is scattered from the direct wave into the coda as the shear wave propagates in the crust. I use the growth with source-receiver distance of the high-frequency energy in the coda relative to the direct wave to estimate the scattering attenuation of the crust. For seismograms from New York, it is consistently observed that the time decay of high-frequency energy in the coda, when compared to the low-frequency coda decay, is less than the relative decay of high-frequency energy with travel time in the Lg wave. This observations supports the idea that the time decay of the coda is controlled mainly by the anelastic attenuation and is insensitive to the scattering attenuation, as suggested by coda models incorporating conservation of energy such as the energy flux model. I use the relative time decay of high-frequency energy in the coda to determine the anelastic attenuation. This analysis indicates that the observed attenuation of 15-Hz Lg waves in New York State (Δ = 100-400 km) is caused about equally by scattering and anelasticity. Using the estimate of Lg wave Q as a constraint, I find that the scattering Q in the crust of New York is either independent of frequency or increases with frequency ƒ slower than ƒ0.3. This implies that the one-dimensional power spectrum of spatial velocity variations in the crust of New York decays with increasing

  16. Seismic and gravity constraints on the nature of the basement in the Africa-Eurasia plate boundary: New insights for the geodynamic evolution of the SW Iberian margin

    NASA Astrophysics Data System (ADS)

    Martínez-Loriente, Sara; Sallarès, Valentí; Gràcia, Eulàlia; Bartolome, Rafael; Dañobeitia, Juan José; Zitellini, Nevio

    2014-01-01

    We present a new classification of geological domains at the Africa-Eurasia plate boundary off SW Iberia, together with a regional geodynamic reconstruction spanning from the Mesozoic extension to the Neogene-to-present-day convergence. It is based on seismic velocity and density models along a new transect running from the Horseshoe to the Seine abyssal plains, which is combined with previously available geophysical models from the region. The basement velocity structure at the Seine Abyssal Plain indicates the presence of a highly heterogeneous, thin oceanic crust with local high-velocity anomalies possibly representing zones related to the presence of ultramafic rocks. The integration of this model with previous ones reveals the presence of three oceanic domains offshore SW Iberia: (1) the Seine Abyssal Plain domain, generated during the first stages of slow seafloor spreading in the NE Central Atlantic (Early Jurassic); (2) the Gulf of Cadiz domain, made of oceanic crust generated in the Alpine-Tethys spreading system between Iberia and Africa, which was coeval with the formation of the Seine Abyssal Plain domain and lasted up to the North Atlantic continental breakup (Late Jurassic); and (3) the Gorringe Bank domain, made of exhumed mantle rocks, which formed during the first stages of North Atlantic opening. Our models suggest that the Seine Abyssal Plain and Gulf of Cadiz domains are separated by the Lineament South strike-slip fault, whereas the Gulf of Cadiz and Gorringe Bank domains appear to be limited by a deep thrust fault located at the center of the Horseshoe Abyssal Plain.

  17. Subduction processes off chile (SPOC) - results from The amphibious wide-angle seismic experiment across The chilean subduction zone

    NASA Astrophysics Data System (ADS)

    Lueth, S.; Spoc Resaerch Group

    2003-04-01

    One component of the onshore-offshore, active-passive seismic experiment SPOC (Krawczyk et al., Stiller et al., this vol.) was a 2-D wide-angle seismic experiment covering the Chilean subduction zone from the Nazca Plate to the Magmatic Arc in the main cordillera. Three W-E-profiles of 52 stations each and up to 240 km long were deployed between 36° and 39° S. These profiles recorded chemical shots at their ends and, in order to extend the onshore profiles, the airgun pulses from RV SONNE cruising simultaneously on offshore profiles. On the southernmost of the three profiles OBHs/OBSs were deployed offshore, thus providing continuous wide-angle seismic data from the Nazca Plate to the South-American continent. Data examples, correlations, and velocity models along the three transects will be presented. The Moho of the subducted oceanic crust can be constrained by PmP-reflections down to 45 km depth under the coastal cordillera. The P-wave velocity field of the crust of the upper plate is characterized by gradually increasing P-wave velocities from East to West. Low seismic velocities (Vp < ~5 km/s) indicate the location of a young accretionary complex at the western tip of the continent. The highest seismic velocities (Vp > ~6.5 km/s below 10 km depth) are observed at the eastern margin of the investigated area.

  18. Telemedicine as a Tool for Europe-Africa Cooperation: A Practical Experience

    NASA Astrophysics Data System (ADS)

    Dinis, Manuel; Santiago, Fernando; Silva, Luís; Ferreira, Ricardo; Machado, José; Castela, Eduardo

    This paper presents the experience of an Europe-Africa telemedicine network, focused on the pediatric area, and involving hospitals located in Luanda (Angola), Benguela (Angola), Praia (Cape Verde) and Coimbra (Portugal). In the scope of this network, the cooperation between these hospitals goes beyond the teleconsultation sessions. Tele-training, clinical experience exchange, patient transfer agreements and health staff training to local development of new medical capabilities are some of the involved activities. It is therefore agreed that this kind of technical and knowledge network could also be expanded to other African countries with clear benefits to the local citizens, overcoming the digital-divide and improving the cooperation between developed and developing countries.

  19. The experience of cash transfers in alleviating childhood poverty in South Africa: mothers' experiences of the Child Support Grant.

    PubMed

    Zembe-Mkabile, Wanga; Surender, Rebecca; Surrender, Rebecca; Sanders, David; Jackson, Debra; Doherty, Tanya

    2015-01-01

    Cash transfer (CT) programmes are increasingly being used as policy instruments to address child poverty and child health outcomes in developing countries. As the largest cash-transfer programme in Africa, the South African Child Support Grant (CSG) provides an important opportunity to further understand how a CT of its kind works in a developing country context. We explored the experiences and views of CSG recipients and non-recipients from four diverse settings in South Africa. Four major themes emerged from the data: barriers to accessing the CSG; how the CSG is utilised and the ways in which it makes a difference; the mechanisms for supplementing the CSG; and the impact of not receiving the grant. Findings show that administrative factors continue to be the greatest barrier to CSG receipt, pointing to the need for further improvements in managing queues, waiting times and coordination between departments for applicants trying to submit their applications. Many recipients, especially those where the grant was the only source of income, acknowledged the importance of the CSG, while also emphasising its inadequacy. To maximise their impact, CT programmes such as the CSG need to be fully funded and form part of a broader basket of poverty alleviation strategies.

  20. The experience of cash transfers in alleviating childhood poverty in South Africa: Mothers' experiences of the Child Support Grant

    PubMed Central

    Zembe-Mkabile, Wanga; Surrender, Rebecca; Sanders, David; Jackson, Debra; Doherty, Tanya

    2015-01-01

    Cash transfer (CT) programmes are increasingly being used as policy instruments to address child poverty and child health outcomes in developing countries. As the largest cash-transfer programme in Africa, the South African Child Support Grant (CSG) provides an important opportunity to further understand how a CT of its kind works in a developing country context. We explored the experiences and views of CSG recipients and non-recipients from four diverse settings in South Africa. Four major themes emerged from the data: barriers to accessing the CSG; how the CSG is utilised and the ways in which it makes a difference; the mechanisms for supplementing the CSG; and the impact of not receiving the grant. Findings show that administrative factors continue to be the greatest barrier to CSG receipt, pointing to the need for further improvements in managing queues, waiting times and coordination between departments for applicants trying to submit their applications. Many recipients, especially those where the grant was the only source of income, acknowledged the importance of the CSG, while also emphasising its inadequacy. To maximise their impact, CT programmes such as the CSG need to be fully funded and form part of a broader basket of poverty alleviation strategies. PMID:25685927

  1. Filovirus Research in Gabon and Equatorial Africa: The Experience of a Research Center in the Heart of Africa

    PubMed Central

    Leroy, Eric; Gonzalez, Jean Paul

    2012-01-01

    Health research programs targeting the population of Gabon and Equatorial Africa at the International Center for Medical Research in Franceville (CIRMF), Gabon, have evolved during the years since its inception in 1979 in accordance with emerging diseases. Since the reemergence of Ebola virus in Central Africa, the CIRMF “Emerging Viral Disease Unit” developed diagnostic tools and epidemiologic strategies and transfers of such technology to support the response of the National Public Health System and the World Health Organization to epidemics of Ebola virus disease. The Unit carries out a unique investigation program on the natural history of the filoviruses, emergence of epidemics, and Ebola virus pathogenesis. In addition, academic training is provided at all levels to regional and international students covering emerging conditions (host factors, molecular biology, genetics) that favor the spread of viral diseases. PMID:23170174

  2. Regional Initiatives in Support of Surveillance in East Africa: The East Africa Integrated Disease Surveillance Network (EAIDSNet) Experience

    PubMed Central

    Ope, Maurice; Sonoiya, Stanley; Kariuki, James; Mboera, Leonard E.G.; Gandham, Ramana N.V.; Schneidman, Miriam; Kimura, Mwihaki

    2013-01-01

    The East African Integrated Disease Surveillance Network (EAIDSNet) was formed in response to a growing frequency of cross-border malaria outbreaks in the 1990s and a growing recognition that fragmented disease interventions, coupled with weak laboratory capacity, were making it difficult to respond in a timely manner to the outbreaks of malaria and other infectious diseases. The East Africa Community (EAC) partner states, with financial support from the Rockefeller Foundation, established EAIDSNet in 2000 to develop and strengthen the communication channels necessary for integrated cross-border disease surveillance and control efforts. The objective of this paper is to review the regional EAIDSNet initiative and highlight achievements and challenges in its implementation. Major accomplishments of EAIDSNet include influencing the establishment of a Department of Health within the EAC Secretariat to support a regional health agenda; successfully completing a regional field simulation exercise in pandemic influenza preparedness; and piloting a web-based portal for linking animal and human health disease surveillance. The strategic direction of EAIDSNet was shaped, in part, by lessons learned following a visit to the more established Mekong Basin Disease Surveillance (MBDS) regional network. Looking to the future, EAIDSNet is collaborating with the East, Central and Southern Africa Health Community (ECSA-HC), EAC partner states, and the World Health Organization to implement the World Bank-funded East Africa Public Health Laboratory Networking Project (EAPHLNP). The network has also begun lobbying East African countries for funding to support EAIDSNet activities. PMID:23362409

  3. The North East Italy (NI) broadband seismic network run by OGS: experience in improving the long period performances

    NASA Astrophysics Data System (ADS)

    Pesaresi, D.

    2009-04-01

    experimented and routinely used by the world wide GEOFON seismic network and the German regional seismic network: examples and performances of a typical OGS installation will be shown.

  4. Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment

    USGS Publications Warehouse

    Beaudoin, B.C.; Godfrey, N.J.; Klemperer, S.L.; Lendl, C.; Trehu, A.M.; Henstock, T.J.; Levander, A.; Holl, J.E.; Meltzer, A.S.; Luetgert, J.H.; Mooney, W.D.

    1996-01-01

    Three seismic refraction-reflection profiles, part of the Mendocino triple junction seismic experiment, allow us to compare and contrast crust and upper mantle of the North American margin before and after it is modified by passage of the Mendocino triple junction. Upper crustal velocity models reveal an asymmetric Great Valley basin overlying Sierran or ophiolitic rocks at the latitude of Fort Bragg, California, and overlying Sierran or Klamath rocks near Redding, California. In addition, the upper crustal velocity structure indicates that Franciscan rocks underlie the Klamath terrane east of Eureka, California. The Franciscan complex is, on average, laterally homogeneous and is thickest in the triple junction region. North of the triple junction, the Gorda slab can be traced 150 km inboard from the Cascadia subduction zone. South of the triple junction, strong precritical reflections indicate partial melt and/or metamorphic fluids at the base of the crust or in the upper mantle. Breaks in these reflections are correlated with the Maacama and Bartlett Springs faults, suggesting that these faults extend at least to the mantle. We interpret our data to indicate tectonic thickening of the Franciscan complex in response to passage of the Mendocino triple junction and an associated thinning of these rocks south of the triple junction due to assimilation into melt triggered by upwelling asthenosphere. The region of thickened Franciscan complex overlies a zone of increased scattering, intrinsic attenuation, or both, resulting from mechanical mixing of lithologies and/or partial melt beneath the onshore projection of the Mendocino fracture zone. Our data reveal that we have crossed the southern edge of the Gorda slab and that this edge and/or the overlying North American crust may have fragmented because of the change in stress presented by the edge.

  5. Antiretroviral Treatment Adherence: Knowledge and Experiences among Adolescents and Young Adults in Soweto, South Africa

    PubMed Central

    Tshabalala, Celokuhle; Laher, Fatima

    2017-01-01

    Human immunodeficiency virus (HIV) management of adolescents and young adults (AYAs) is particularly pertinent to sub-Saharan Africa, where the pediatric HIV burden is marked. Antiretroviral treatment (ART) adherence is a major challenge for AYAs. This qualitative study explored knowledge and experiences of adherence amongst AYAs attending treatment at the Perinatal HIV Research Unit (PHRU), Soweto, South Africa. Four focus group discussions (FGDs) and eight in-depth interviews (IDIs) were conducted with HIV-infected 15–25-year-old ART recipients. Transcripts were coded thematically. Participants (n = 26) were aged median 18.5 years, 59.1% female and 69.2% virally suppressed <400 cp/ml. Three main themes emerged during FGDs and IDIs: (i) correct knowledge about how to be adherent, benefits, and nonadherence consequences, (ii) social, personal, and medication-related barriers to adherence, and (iii) reminder, concealment, and motivational strategies to optimize adherence. Interventions to improve AYA adherence could focus on practical strategies, including status disclosure and medication concealment.

  6. Regional Seismic Signals from Chemical Explosions, Nuclear Explosions and Earthquakes: Results from the Arizona Source Phenomenology Experiment

    SciTech Connect

    Walter, W R; Gok, R; Mayeda, K; Sicherman, A; Bonner, J; Leidig, M

    2005-09-02

    Routine industrial mining explosions play two important roles in seismic nuclear monitoring research: (1) they are a source of background events that need to be discriminated from potential nuclear explosions; (2) as some of the only explosions occurring in the current de facto global moratoria on nuclear testing, their signals should be exploited to improve the calibration of seismic m monitoring systems. A common issue monitoring arising in both of these roles is our limited physical understanding of the causes behind observed differences and similarities in the seismic signals produced by routine industrial mining blasts and small underground nuclear tests. In 2003 a consortium (Weston, SMU, LLNL, LANL and UTEP) carried out a Source Phenomenology Experiment (SPE), a series of dedicated explosions designed to improve this physical understanding, particularly as it relates to seismic methods of discriminating between signals from three different source types: earthquakes, industrial blasts, and nuclear tests. Here we very briefly review prior field experimental work that examined the seismic relationships between these source types.

  7. Healthcare experiences of lesbian and bisexual women in Cape Town, South Africa.

    PubMed

    Smith, Riley

    2015-01-01

    Understanding the health needs and experiences of South African lesbian and bisexual women is imperative for implementing effective and inclusive public health strategies. Such understanding, however, is limited due to the exclusion of these women from most existing research on healthcare access in the region. This paper bridges that gap by investigating the healthcare experiences of lesbian and bisexual women in Cape Town. Data were gathered from 22 interviews with self-identified lesbian and bisexual community members and university students in the Cape Town area. Interviews explored obstacles women face in accessing affirming services, different experiences with public and private healthcare, fear of stigma/discrimination, availability of relevant sexual health information and suggestions to improve existing programmes. Findings suggest that South African lesbians and bisexual women may have a range of both positive and negative experiences in public and private health services, that they use protective strategies when 'coming out' and that they find that sexual health information pertinent to them is largely unavailable. These discussions contribute to a more inclusive understanding of the experiences of lesbian and bisexual women accessing healthcare and other services and help to inform providers, thereby enabling them to deliver more meaningful care to lesbian, gay, bisexual and transgender persons in South Africa.

  8. Seafloor bathymetry and gravity from the ALBACORE marine seismic experiment offshore southern California

    NASA Astrophysics Data System (ADS)

    Shintaku, N.; Weeraratne, D. S.; Kohler, M. D.

    2010-12-01

    Although the North America side of the plate boundary surrounding the southern California San Andreas fault region is well studied and instrumented, the Pacific side of this active tectonic boundary is poorly understood. In order to better understand this complex plate boundary offshore, its microplate structures, deformation, and the California Borderland formation, we have recently conducted the first stage of a marine seismic experiment (ALBACORE - Asthenospheric and Lithospheric Broadband Architecture from the California Offshore Region Experiment) deploying 34 ocean bottom seismometers offshore southern California in August 2010. We present preliminary data consisting of seafloor bathymetry and free air gravity collected from this experiment. We present high-resolution maps of bathymetry and gravity from the ALBACORE experiment compiled with previous ship track data obtained from the NGDC (National Geophysical Data Center) and the USGS. We use gravity data from Smith and Sandwell and study correlations with ship track bathymetry data for the features described below. We observe new seafloor geomorphological features far offshore and within the Borderland. Steep canyon walls which line the edges of the Murray fracture zone with possible volcanic flows along the canyon floor were mapped by multibeam bathymetry for the first time. Deep crevices juxtaposed with high edifices of intensely deformed plateaus indicate high strain deformation along the arcuate boundary of the Arguello microplate. Small volcanic seamounts are mapped which straddle the Ferrelo fault (Outer Borderland) and San Pedro fault (Inner Borderland), and appear to exhibit fracture and fault displacement of a portion of the volcanic centers in a left-lateral sense. A large landslide is also imaged extending approximately 6 miles in length and 3 miles in width in the Santa Cruz basin directly south of Santa Rosa Island. Deformation associated with capture of Arguello and Patton microplates by the

  9. Evaluation and developmental studies of possible active seismic experiments during the post-Apollo period

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.

    1974-01-01

    Seismic velocity studies pertinent to the lunar crust and mantle are briefly summarized. The compressional and shear wave velocities in loose aggregates are discussed along with the effects of temperature on seismic velocity in compacted powders. Abstracts of papers concerning the lunar structure are included.

  10. The Seismic Aftershock Monitoring System (SAMS) for OSI - Experiences from IFE14

    NASA Astrophysics Data System (ADS)

    Gestermann, Nicolai; Sick, Benjamin; Häge, Martin; Blake, Thomas; Labak, Peter; Joswig, Manfred

    2016-04-01

    An on-site inspection (OSI) is the third of four elements of the verification regime of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The sole purpose of an OSI is to confirm whether a nuclear weapon test explosion or any other nuclear explosion has been carried out in violation of the treaty and to gather any facts which might assist in identifying any possible violator. It thus constitutes the final verification measure under the CTBT if all other available measures are not able to confirm the nature of a suspicious event. The Provisional Technical Secretariat (PTS) carried out the Integrated Field Exercise 2014 (IFE14) in the Dead Sea Area of Jordan from 3 November to 9. December 2014. It was a fictitious OSI whose aim was to test the inspection capabilities in an integrated manner. The technologies allowed during an OSI are listed in the Treaty. The aim of the Seismic Aftershock Monitoring System (SAMS) is to detect and localize aftershocks of low magnitudes of the triggering event or collapses of underground cavities. The locations of these events are expected in the vicinity of a possible previous explosion and help to narrow down the search area within an inspection area (IA) of an OSI. The success of SAMS depends on the main elements, hardware, software, deployment strategy, the search logic and not least the effective use of personnel. All elements of SAMS were tested and improved during the Built-Up Exercises (BUE) which took place in Austria and Hungary. IFE14 provided more realistic climatic and hazardous terrain conditions with limited resources. Significant variations in topography of the IA of IFE14 in the mountainous Dead Sea Area of Jordan led to considerable challenges which were not expected from experiences encountered during BUE. The SAMS uses mini arrays with an aperture of about 100 meters and with a total of 4 elements. The station network deployed during IFE14 and results of the data analysis will be presented. Possible aftershocks of

  11. Siting of USArray Seismic Stations in North Carolina and southern Virginia: Experience of NC-1 Team

    NASA Astrophysics Data System (ADS)

    Martin, P.; Howard, J.; Horne, T.

    2012-12-01

    The USArray component of the EarthScope, a transportable array of 400 seismometers installed in a grid about 70 km apart, is in the next two years entering its final stage with station deployment along the Atlantic coast of the United States. Here, we present the experience of the student-faculty team from North Carolina Central University (NCCU) in finding and documenting the suitable sites for the twenty five USArray stations in North Carolina and southern Virginia. The ideal sites are easily accessible yet far from traffic and other sources of noise, with good cell phone coverage, sun exposure and out of flood-prone areas. Although the initial selection of potential locations was done using geospatial mapping and analysis software provided by EarthScope, finding and finalizing the sites involved driving more then 1,000 miles each week for over two months inspecting possible site locations. Aside from driving, the majority of time was spent talking about the EarthScope project and hosting of USArray stations to mostly reluctant landowners. In addition to facing various challenges in finding appropriate sites due to land use issues, such as suburban sprawl of central North Carolina, or topography factors, such as low lying flood prone coastal areas, by far the major challenge was finding the landowners willing to host the seismic station for the necessary three years. In addition to involving students from an HBCU in seismology related project and increasing the visibility of NCCU geophysics program in the University and local community through publicity releases in local media and on university web site, the project had an important outreach component. As North Carolina is located along the seismically quiet, passive Atlantic margin, most residents are not familiar with earthquakes and seismology and the siting experience provided students an opportunity to practice explaining the earthquake research to the general public. The dialog also highlighted science

  12. Characterization and comparison of seismic signals emitted during field scale sheer box experiments and artificially induced landslides

    NASA Astrophysics Data System (ADS)

    Yfantis, Georgios; Martinez Carvajal, Hernan Eduardo; Pytharouli, Stella; Lunn, Rebecca

    2014-05-01

    The identification and detection of landslide induced seismic signals, recorded by deployed seismometers on active landslides has been the subject of many studies. The most commonly faced problem is the uncertainty in identifying which of the recorded signals are representing a movement or a failure in the landslide's body. In this paper we present two novel experimental campaigns; 1) field scale laboratory experiments of a 65cm diameter sheer box, 2) artificially induced failure of two, two-meter high vertical soil slopes. Using a field scale sheer box we recorded seismic signals emitted during soil slippage events, a phenomenon observed at a landslide's failure plain. This was implemented by displacing, a few centimeters at a time (1-10cm), a concrete cylinder filled with soil along a corridor free from vegetation. The field scale sheer box methodology allows control over a large number of parameters that affect a landslide. For example, it is possible to control soil saturation thus simulating different rain events or control the stress field on the soil's slippage surface simulating displacement events at different depths. More than 40 displacement events were induced under four different loading conditions between 472kg to 829kg. All soil slippage events were recorded above the levels of background seismic noise. Repetition of the methodology under the same experimental conditions resulted in similar seismic signals allowing us to define a 'characteristic seismic response' for soils. In the second experimental campaign, two controlled landslides were experimentally induced by increasing the vertical load on top of a 2m soil scarp. We were able to detect from 1 to 10 centimeter wide crack propagations and displacements, and approximately 20x20x10cm to 100x50x20cm block failure events based on microseismic recordings, field notes, video recordings and displacement measurements of the landslide's crown that failed during the experiments. Direct correlation

  13. Conceptual Design and Architecture of Mars Exploration Rover (MER) for Seismic Experiments Over Martian Surfaces

    NASA Astrophysics Data System (ADS)

    Garg, Akshay; Singh, Amit

    2012-07-01

    Keywords: MER, Mars, Rover, Seismometer Mars has been a subject of human interest for exploration missions for quite some time now. Both rover as well as orbiter missions have been employed to suit mission objectives. Rovers have been preferentially deployed for close range reconnaissance and detailed experimentation with highest accuracy. However, it is essential to strike a balance between the chosen science objectives and the rover operations as a whole. The objective of this proposed mechanism is to design a vehicle (MER) to carry out seismic studies over Martian surface. The conceptual design consists of three units i.e. Mother Rover as a Surrogate (Carrier) and Baby Rovers (two) as seeders for several MEMS-based accelerometer / seismometer units (Nodes). Mother Rover can carry these Baby Rovers, having individual power supply with solar cells and with individual data transmission capabilities, to suitable sites such as Chasma associated with Valles Marineris, Craters or Sand Dunes. Mother rover deploys these rovers in two opposite direction and these rovers follow a triangulation pattern to study shock waves generated through firing tungsten carbide shells into the ground. Till the time of active experiments Mother Rover would act as a guiding unit to control spatial spread of detection instruments. After active shock experimentation, the babies can still act as passive seismometer units to study and record passive shocks from thermal quakes, impact cratering & landslides. Further other experiments / payloads (XPS / GAP / APXS) can also be carried by Mother Rover. Secondary power system consisting of batteries can also be utilized for carrying out further experiments over shallow valley surfaces. The whole arrangement is conceptually expected to increase the accuracy of measurements (through concurrent readings) and prolong life cycle of overall experimentation. The proposed rover can be customised according to the associated scientific objectives and further

  14. "We Must Believe in Ourselves": Attitudes and Experiences of Adult Learners with Disabilities in Kwazulu-Natal, South Africa

    ERIC Educational Resources Information Center

    Rule, Peter; Modipa, Taadi Ruth

    2012-01-01

    Many adults with disabilities in South Africa never had a chance to attend school or dropped out at an early age because of poverty and discrimination. This article investigates the attitudes and experiences of adults with disabilities regarding education. It draws on an interactional model of disability and an embodied understanding of cognition…

  15. Performing and Defying Gender: An Exploration of the Lived Experiences of Women Higher Education Administrators in Sub-Saharan Africa

    ERIC Educational Resources Information Center

    Johnson, Ane Turner

    2014-01-01

    The purpose of this phenomenological study was to explore the life and career paths of women higher education administrators in sub-Saharan Africa. Specifically, the study sought to interpret the women's experiences and identities, through the framework of intersectionality and gender performance, as ones that contributed to advancement within…

  16. Randomized Impact Evaluation of Education Interventions: Experiences and Lessons from a Reading to Learn Intervention in East Africa

    ERIC Educational Resources Information Center

    Ngware, Moses Waithanji; Abuya, Benta; Oketch, Moses; Admassu, Kassahun; Mutisya, Maurice; Musyoka, Peter

    2015-01-01

    This paper presents the experiences and lessons learnt during the design and implementation of the randomized impact evaluation (IE) of a reading to learn (RtL) intervention in early primary grades. The study was to assess the impact of RtL on literacy and numeracy among pupils in low-performing districts in East Africa. The intervention was…

  17. Experiences and Psychosocial Impact of West Africa Ebola Deployment on US Health Care Volunteers

    PubMed Central

    Gershon, Robyn; Dernehl, Liza A.; Nwankwo, Ezinne; Zhi, Qi; Qureshi, Kristine

    2016-01-01

    Background: This qualitative study was designed to assess health care volunteers’ experiences and psychosocial impacts associated with deployment to the West Africa Ebola epidemic. Methods: In 2015, using snowball sampling, 16 US health care volunteers who had recently returned from West Africa were recruited for this study. Semi-structured interviews were conducted to collect information associated with each phase of deployment (pre, peri, and post). Results: Participants reported that they were motivated to volunteer because of a sense of responsibility and feelings of empathy and altruism. Immediately prior to deployment, most reported fear of contagion and death, as well as doubts regarding the adequacy of their training. Family members and close friends expressed high levels of concern regarding participants’ decisions to volunteer. During the deployment, participants were fearful of exposure and reported feeling emotionally and physically exhausted. They also reported feeling frustrated by extreme resource limitations, poor management of the mission, lack of clearly defined roles and responsibilities, and inability to provide high quality care. Upon return home, participants felt a sense of isolation, depression, stigmatization, interpersonal difficulties, and extreme stress. Conclusion: Preparedness of volunteers was suboptimal at each stage of deployment. All stakeholders, including volunteers, sponsoring organizations, government agencies, and professional organizations have a shared responsibility in ensuring that volunteers to medical missions are adequately prepared. This is especially critical for high risk deployments. Effective policies and practices need to be developed and implemented in order to protect the health and well-being of health care volunteers to the fullest extent possible. PMID:27803840

  18. Crustal structure beneath two seismic broadband stations revealed from teleseismic P-wave receiver function analysis in the Virunga volcanic area, Western Rift Valley of Africa

    NASA Astrophysics Data System (ADS)

    Tuluka, Georges Mavonga

    2010-12-01

    The shear velocity structure beneath the Virunga volcanic area was estimated by using an average solution in the time domain inversion of stacked teleseismic receiver functions provided by two seismic broadband stations KUNENE (KNN) and KIBUMBA (KBB). These two stations are 29 km apart and located at the eastern and western escarpment of the Western Rift Valley of Africa in the Virunga area, respectively. The velocity model was presented as P-wave velocity models. From these models, the crust mantle transition zone beneath the area sampled by KNN and KBB in the Virunga area was determined at depth from about 36 to 39 km and 30 to 41 km, respectively. A low velocity zone was observed below stations KNN and KBB at depths between 20-30 km and 18-28 km, respectively, and with average velocity 5.9 km/s and 6.0 km/s. This low velocity zone may probably related to a magma chamber or a melt-rich sill. The models show also high velocity material (6.8-7.4 km/s) lying beneath stations KNN and KBB at depths 3-20 km and 3-10 km, respectively, which is indicative of magma cumulates within the volcanic edifice. The result obtained in this study was applied to the determination of epicentres during the period prior to the 27 November 2006 Nyamuragira eruption. This eruption was preceded by a swarm of hybrid volcanic earthquakes with clear P-waves onset. Using the receiver function model was found to improve the location of events. The located events correlate well with the location of the eruptive site and data provided by the INSAR observations of surface deformation associated with eruption.

  19. Revealing the full extent of households' experiences of HIV and AIDS in rural South Africa.

    PubMed

    Hosegood, Victoria; Preston-Whyte, Eleanor; Busza, Joanna; Moitse, Sindile; Timaeus, Ian M

    2007-09-01

    Households experience HIV and AIDS in a complex and changing set of environments. These include health and welfare treatment and support services, HIV-related stigma and discrimination, and individual and household social and economic circumstances. This paper documents the experiences of 12 households directly affected by HIV and AIDS in rural KwaZulu Natal, South Africa, between 2002 and 2004. The households were observed during repeated visits over a period of more than a year by ethnographically trained researchers. Field notes were analysed using thematic content analysis to identify themes and sub-themes. This paper focuses on three dimensions of household experience of HIV and AIDS that have received little attention in HIV and AIDS impact studies. First, that experience of HIV and AIDS is cumulative. In an area where population surveys report HIV prevalence rates of over 20% in adults, many households face multiple episodes of HIV-related illness and AIDS deaths. We describe how these challenges affect perceptions and responses within and outside households. Second, while over 50% of all adult deaths are due to AIDS, households continue to face other causes of illness and death. We show how these other causes compound the impact of AIDS, particularly where the deceased was the main income earner and/or primary carer for young children. Third, HIV-related illness and AIDS deaths of household members are only part of the households' cumulative experience of HIV and AIDS. Illness and death of non-household members, for example, former partners who are parents of children within the households or relatives who provide financial support, also impact negatively on households. We also discuss how measuring multiple episodes of illness and deaths can be recorded in household surveys in order to improve quantitative assessments of the impact of HIV and AIDS.

  20. Out of (South) Africa: Pretoria`s nuclear weapons experience. Final report

    SciTech Connect

    Horton, R.E.

    1998-04-01

    The primary focus of this paper is the impact of key South African leaders on the successful developments and subsequent rollbacks of South Africa`s nuclear weapons capability. It highlights the key milestones in the development of South Africa`s nuclear weapon capability. It also relates how different groups within South Africa (scientists, politicians, military and technocrats) interacted to successfully produce South Africa`s nuclear deterrent. It emphasizes the pivotal influence of the senior political leadership to pursue nuclear rollback given the disadvantages of its nuclear means to achieve vital national interests. The conclusions drawn from flu`s effort are the South African nuclear program was an extreme response to its own identity Crisis. Nuclear weapons became a means to achieving a long term end of a closer affiliation with the West. A South Africa yearning to be identified as a Western nation and receive guarantees of its security rationalized the need for a nuclear deterrent. The deterrent was intended to draw in Western support to counter a feared total onslaught by Communist forces in the region. Two decades later, that same South Africa relinquished its nuclear deterrent and reformed its domestic policies to secure improved economic and political integration with the West.

  1. Comparison of seismic and hydrodynamic yield determinations for the Soviet joint verification experiment of 1988

    PubMed Central

    Sykes, Lynn R.; Ekström, Göran

    1989-01-01

    Seismic magnitudes determined from surface and body waves for the Soviet underground nuclear explosion of September 14, 1988, are used to calculate the yield of that event from previously derived calibration curves. The yield obtained by combining the two seismic estimates is 113 kilotons, which is very close to those obtained by hydrodynamic measurements made on-site. This comparison substantiates previous conclusions about the sizes of past Soviet weapons tests and compliance with the Threshold Test Ban Treaty. The factor of uncertainty in the combined seismic yield is 1.28 at the 68% and 1.62 at the 95% confidence levels, demonstrating that accuracies considerably better than a factor of 2 can be obtained by combining seismic determinations of yield. PMID:16594040

  2. Children's experiences of corporal punishment: A qualitative study in an urban township of South Africa.

    PubMed

    Breen, Alison; Daniels, Karen; Tomlinson, Mark

    2015-10-01

    Exposure to violence is a serious mental and public health issue. In particular, children exposed to violence are at risk for poor developmental outcomes and physical and mental health problems. One area that has been shown to increase the risk for poor outcomes is the use of corporal punishment as a discipline method. While researchers are starting to ask children directly about their experiences of violence, there is limited research with children about their perspectives on physical punishment, particularly in low-and middle-income countries (LMIC). This paper begins to address this gap by reporting on the spontaneous data that emerged during 24 qualitative interviews that were conducted with children, aged 8-12 in South Africa. The themes that emerged indicated that corporal punishment is an everyday experience, that it has negative emotional and behavioral consequences, and that it plays a role in how children resolve interpersonal conflicts. The study highlights the challenges for violence prevention interventions in under-resourced contexts.

  3. Experiments on the Brazil-nut effect due to seismic shakings

    NASA Astrophysics Data System (ADS)

    Maciel, A.; Tancredi, G.; Lluch, N.

    2014-07-01

    Size segregation processes have been identified as relevant when studying the behaviour of rocks and boulders on the surface and in the interior of a rubble-pile asteroid. The size segregation as a consequence of repeated shakings is also known as the Brazil-nut effect (BNE). These processes might be really important when studying rubble-pile -type asteroids, which may have suffered seisms as a consequence of repeated collisions; such as in the case of asteroid Itokawa. Size segregation processes can be studied using laboratory experiments as well as computational models, the first case being the one initially considered in this work. Previous studies of the BNE were performed using a sinusoidal vertical or horizontal vibration of the containers. Since we are interested in the effects of repeated seismic shakes, we have used in our experiments a sequence of repeated knocks of the container. We built a resin and polycarbonate box, which is filled with marbles of different sizes. Vacuum up to 0.5 % of ambient pressure is established inside the box. The box is subjected to repeated free-falls from heights up to 1m, with impact velocities on the ground up to 4m/s. We have chosen these low velocities since they are comparable to the escape velocities of km-size asteroids; and they are on the order of the displacement velocities of surface material as a consequence of a small impact (far from the impact point; Tancredi et al. 2012). We study the dependence of size segregation processes with the size rate among the spheres and the impact speed of the box. We observe that, when effectively occurs, size segregation mostly depends on the size rate of the particles and very little on the impact speed, even though this slight dependence has been recorded in our experiments. The laboratory experiments have been also numerically simulated using the Discrete Element Method (DEM) package known as ESyS-particle. The results of the numerical simulations are compared to the

  4. Building Geophysics Talent and Opportunity in Africa: Experience from the AfricaArray/Wits Geophysics Field School

    NASA Astrophysics Data System (ADS)

    Webb, S. J.; Manzi, M.; Scheiber-Enslin, S. E.; Durrheim, R. J.; Jones, M. Q. W.; Nyblade, A.

    2015-12-01

    There are many challenges faced by geophysics students and academic staff in Africa that make it difficult to develop effective field and research programs. Challenges to conducting field work that have been identified, and that can be tackled are: lack of training on geophysical equipment and lack of exposure to field program design and implementation. To address these challenges, the AfricaArray/Wits Geophysics field school is designed to expose participants to a wide variety of geophysical instruments and the entire workflow of a geophysical project. The AA field school was initially developed for the geophysics students at the University of the Witwatersrand. However, by increasing the number of participants, we are able to make more effective use of a large pool of equipment, while addressing challenging geophysical problems at a remote field site. These additional participants are selected partially based on the likely hood of being able start a field school at their home institution. A good candidate would have access to geophysical equipment, but may not have knowledge of how to use it or how to effectively design surveys. These are frequently junior staff members or graduate students in leadership roles. The three week program introduces participants to the full geophysical field workflow. The first week is spent designing a geophysical survey, including determining the cost. The second week is spent collecting data to address a real geophysical challenge, such as determining overburden thickness, loss of ground features due to dykes in a mine, or finding water. The third week is spent interpreting and integrating the various data sets culminating in a final presentation. Participants are given all lecture material and much of the software is open access; this is done to encourage using the material at the home institution. One innovation has been to use graduate students as instructors, thus building a pool of talent that has developed the logistic and

  5. Rock mass response to strong ground motion generated by mining induced seismic events and blasting observed at the surface of the excavations in deep level gold mines in South Africa

    NASA Astrophysics Data System (ADS)

    Milev, Alexander; Durrheim, Ray; Ogasawara, Hiroshi

    2014-05-01

    The strong ground motion generated by mining induced seismic events was studied to characterize the rock mass response and to estimate the site effect on the surface of the underground excavations. A stand-alone instruments, especially designed for recording strong ground motions, were installed underground at a number of deep level gold mines in South Africa. The instruments were recording data at the surface of the stope hangingwalls. A maximum value of 3 m/s was measured. Therefore data were compared to the data recorded in the solid rock by the mine seismic networks to determine the site response. The site response was defined as the ratio of the peak ground velocity measured at the surface of the excavations to the peak ground velocity inferred from the mine seismic data measured in the solid rocks. The site response measured at all mines studied was found to be 9 ± 3 times larger on average. A number of simulated rockbursts were conducted underground in order to estimate the rock mass response when subjected to extreme ground motion and derive the attenuation factors in near field. The rockbursts were simulated by means of large blasts detonated in solid rock close to the sidewall of a tunnel. The numerical models used in the design of the simulated rockbursts were calibrated by small blasts taking place at each experimental site. A dense array of shock type accelerometers was installed along the blasting wall to monitor the attenuation of the strong ground motion as a function of the distance from the source. The attenuation of the ground motion was found to be proportional to the distance from the source following R^-1.1 & R^-1.7 for compact rock and R^-3.1 & R^-3.4 for more fractured rock close to the surface of the tunnel. In addition the ground motion was compared to the quasi-static deformations taking place around the underground excavations. The quasi-static deformations were measured by means of strain, tilt and closure. A good correspondence

  6. 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

  7. Building on Experience: A Formative Evaluation of a Peer Education Sexual Health Project in South Africa

    ERIC Educational Resources Information Center

    Warwick, Ian; Aggleton, Peter

    2004-01-01

    In South Africa, as elsewhere in the world, the promise of peer education as a means of promoting sexual health has contributed to its increasing popularity. While structural and organisational constraints can compromise the success of peer education, many of those involved in modest local programmes in South Africa are able to address the sexual…

  8. A Pilot Near-vertical Seismic Reflection Experiment In Central Chile Landward of The Offshore Spoc Survey

    NASA Astrophysics Data System (ADS)

    Krawczyk, C. M.; Onshore Nvr Party, Spoc

    Between 36 and 39 S, the multi-disciplinary offshore project SPOC (Subduction Processes Off Chile) was extended landwards in November 2001 by different active and passive seismic experiments, with the zone of seismic coupling, generally located between 20-40 km depth, as the prime target. Here, we report the first results from the near-vertical incidence reflection (NVR) seismic experiment component that was designed to image that part of the subduction zone between the S-America and over- riding Nazca-Plate that is located in the offshore-onshore transition zone. The NVR profile was located at 37 15`S. Covering the westernmost part of a long E-W refrac- tion seismic line (one amongst three), the profile spread was 54 km long, with three sections of 18 km length each, and extended from the coast in the west to the east. 180 geophone-groups were deployed with 100 m spacing which recorded the offshore pro- file shot by the R/V SONNE with the airgun array. Furthermore, 2 small shots in the Pacific Ocean (50 kg and 25 kg charge), 11 small shots (75 kg charge) at 7 different lo- cations within the onshore reflection seismic line, and 1 shot (150 kg charge) ca. 22.5 km east of the active spread were shot. This active NVR-experiment thereby resulted in a 45 km long 2-fold CDP line, and single-fold coverage along 72 km profile length. The preliminary data processing of single shots gives an image of different reflection bands in the upper and middle crust. On the entire profile, a 1 s TWT thick strong reflection band is observed between 3 and 4 s TWT, which shows almost no dip. On the western half of the profile, prominent reflections dip eastward from ca. 6 s TWT down to ca. 8 s TWT. Finally, in the central part of the seismic reflection profile, some relatively weaker reflections are found between 10 to 14 s TWT. All theses eastward dipping reflection bands between 6 and 14 s TWT could be interpreted as indications for the downgoing plate.

  9. Student experiences of participating in five collaborative blended learning courses in Africa and Asia: a survey

    PubMed Central

    Atkins, Salla; Yan, Weirong; Meragia, Elnta; Mahomed, Hassan; Rosales-Klintz, Senia; Skinner, Donald; Zwarenstein, Merrick

    2016-01-01

    Background As blended learning (BL; a combination of face-to-face and e-learning methods) becomes more commonplace, it is important to assess whether students find it useful for their studies. ARCADE HSSR and ARCADE RSDH (African Regional Capacity Development for Health Systems and Services Research; Asian Regional Capacity Development for Research on Social Determinants of Health) were unique capacity-building projects, focusing on developing BL in Africa and Asia on issues related to global health. Objective We aimed to evaluate the student experience of participating in any of five ARCADE BL courses implemented collaboratively at institutions from Africa, Asia, and Europe. Design A post-course student survey with 118 students was conducted. The data were collected using email or through an e-learning platform. Data were analysed with SAS, using bivariate and multiple logistic regression. We focused on the associations between various demographic and experience variables and student-reported overall perceptions of the courses. Results In total, 82 students responded to the survey. In bivariate logistic regression, the course a student took [p=0.0067, odds ratio (OR)=0.192; 95% confidence interval (CI): 0.058–0.633], male gender of student (p=0.0474, OR=0.255; 95% CI: 0.066–0.985), not experiencing technical problems (p<0.001, OR=17.286; 95% CI: 4.629–64.554), and reporting the discussion forum as adequate for student needs (p=0.0036, OR=0.165; 95% CI: 0.049–0.555) were found to be associated with a more positive perception of BL, as measured by student rating of the overall helpfulness of the e-learning component to their studies. In contrast, perceiving the assessment as adequate was associated with a worse perception of overall usefulness. In a multiple regression, the course, experiencing no technical problems, and perceiving the discussion as adequate remained significantly associated with a more positively rated perception of the usefulness of the

  10. Student experiences of participating in five collaborative blended learning courses in Africa and Asia: a survey.

    PubMed

    Atkins, Salla; Yan, Weirong; Meragia, Elnta; Mahomed, Hassan; Rosales-Klintz, Senia; Skinner, Donald; Zwarenstein, Merrick

    2016-01-01

    Background As blended learning (BL; a combination of face-to-face and e-learning methods) becomes more commonplace, it is important to assess whether students find it useful for their studies. ARCADE HSSR and ARCADE RSDH (African Regional Capacity Development for Health Systems and Services Research; Asian Regional Capacity Development for Research on Social Determinants of Health) were unique capacity-building projects, focusing on developing BL in Africa and Asia on issues related to global health. Objective We aimed to evaluate the student experience of participating in any of five ARCADE BL courses implemented collaboratively at institutions from Africa, Asia, and Europe. Design A post-course student survey with 118 students was conducted. The data were collected using email or through an e-learning platform. Data were analysed with SAS, using bivariate and multiple logistic regression. We focused on the associations between various demographic and experience variables and student-reported overall perceptions of the courses. Results In total, 82 students responded to the survey. In bivariate logistic regression, the course a student took [p=0.0067, odds ratio (OR)=0.192; 95% confidence interval (CI): 0.058-0.633], male gender of student (p=0.0474, OR=0.255; 95% CI: 0.066-0.985), not experiencing technical problems (p<0.001, OR=17.286; 95% CI: 4.629-64.554), and reporting the discussion forum as adequate for student needs (p=0.0036, OR=0.165; 95% CI: 0.049-0.555) were found to be associated with a more positive perception of BL, as measured by student rating of the overall helpfulness of the e-learning component to their studies. In contrast, perceiving the assessment as adequate was associated with a worse perception of overall usefulness. In a multiple regression, the course, experiencing no technical problems, and perceiving the discussion as adequate remained significantly associated with a more positively rated perception of the usefulness of the online

  11. High-resolution shallow-seismic experiments in sand. Part 1: Water table, fluid flow, and saturation

    SciTech Connect

    Bachrach, R.; Nur, A.

    1998-07-01

    A high-resolution, very shallow seismic reflection and refraction experiment was conducted to investigate the seismic response of groundwater level changes in beach sand in situ. A fixed 10-m-long receiver array was used for repeated seismic profiling. Direct measurements of water level in a monitoring well and moisture content in the sand were taken as well. The water table in the well changed by about 1 m in slightly delayed response to the nearby ocean tides. In contrast, inversion of the seismic data yielded a totally different picture. The reflection from the water table at high tide appeared at a later time than the reflection at low tide. This unexpected discrepancy can be reconciled using Gassmann`s equation: a low-velocity layer must exist between the near-surface dry sand and the deeper and much faster fully saturated sand. This low-velocity layer coincides with the newly saturated zone and is caused by a combination of the sand`s high density (close to that of fully saturated sand), and its high compressibility (close to that of dry sand). This low-velocity zone causes a velocity pull-down for the high-frequency reflections, and causes a high-tide reflection to appear later in time than low-tide reflection. The calculated velocities in the dry layer show changes with time that correlate with sand dryness, as predicted by the temporal changes of the sand`s density due to changing water/air ratio. The results show that near-surface velocities in sand are sensitive to partial saturation in the transition zone between dry and saturated sand. The authors were able to extract the saturation of the first layer and the depth to the water table from the seismic velocities.

  12. Anatomy of a Metamorphic Core Complex: Preliminary Results of Ruby Mountains Seismic Experiment, Northeastern Nevada

    NASA Astrophysics Data System (ADS)

    Schiltz, K. K.; Litherland, M.; Klemperer, S. L.

    2010-12-01

    The Ruby Mountains Seismic Experiment is a 50-station deployment of Earthscope’s Flexible Array installed in June 2010 to study the Ruby Mountain metamorphic core complex, northeastern Nevada. Competing theories of metamorphic core complexes stress the importance of either (1) low-angle detachment faulting and lateral crustal flow, likely leading to horizontal shearing and anisotropy, or (2) vertical diapirism creating dominantly vertical shearing and anisotropy. Our experiment aims to distinguish between these two hypotheses using densely spaced (5 to 10 km) broadband seismometers along two WNW-ESE transects across the Ruby Range and one NNE-SSW transect along the axis of the range. When data acquisition is complete we will image crustal structures and measure velocity and anisotropy with a range of receiver function, shear-wave splitting and surface-wave tomographic methods. In addition to the newly acquired data, existing data can also be used to build understanding of the region. Previous regional studies have interpreted shear-wave splitting in terms of single-layer anisotropy in the mantle, related to a complex flow structure, but previous controlled source studies have identified measurable crustal anisotropy. We therefore attempted to fit existing data to a two-layer model consisting of a weakly anisotropic crustal layer and a more dominant mantle layer. We used “SplitLab” to measure apparent splitting parameters from ELK (a USGS permanent station) and 3 Earthscope Transportable Array stations. There is a clear variation in the splitting parameters with back-azimuth, but existing data do not provide a stable inversion for a two-layer model. Our best forward-model solution is a crustal layer with a fast axis orientation of 357° and 0.3 second delay time and a mantle layer with a 282° fast axis and 1.3 s delay time. Though the direction of the fast axis is consistent with previously published regional results, the 1.3 s delay time is larger than

  13. Spoc-experiment: Seismic Imaging and Bathymetry of The Central Chile Margin - First Results

    NASA Astrophysics Data System (ADS)

    Ladage, S.; Reichert, C.; Schreckenberger, B.; Block, M.; Bönnemann, C.; Canuta, J.; Damaske, D.; Diaz-Naveas, J.; Gaedicke, C.; Krawczyk, C.; Kus, J.; Urbina, O.; Sepulveda, J.

    During the RV SONNE cruise 161 Leg 1 to 5 (October 2001 to January 2002) Sub- duction Processes Off Chile (SPOC) have been investigated using a multi-disciplinary geoscientific approach. Here we report first results of multi channel seismic (MCS) experiments and high-resolution swath bathymetry data from Leg 3, south of Val- paraiso. 24 MCS profiles with a total length of 3670 km were run between 36 S to 4020' S, providing a detailed view of the structures related to the subduction of the Nazca Plate under the Chile Margin. The oceanic crust of the Nazca Plate shows at least three sets of structural trends associated with the Mocha and Valdivia Fractures Zones, the spreading lineations and subduction related horst and graben structures. In the study area the trench is filled with well stratified turbidites up to 2 seconds TWT thick. Along the trench axis a turbidite channel exceeding 80 m relief exists. Several large deep sea fan complexes are developed at the slope toe. Their distributary canyons cut deep into the slope and shelf and can be traced back to major river mouths. The deformation front is coincident with the slope toe; compressional structures of the trench fill are uncommon. The deformation front is curved and offset along strike, caused presumably by collision and indentation of structures of the Nazca Plate. The most remarkable features of the MCS - profiles, yet, are the only very rudimentary developed modern accretionary prism as well as the high variability of the lower slope angles. Lower slope angles locally exceed 10. The continental crust extends seawards to the middle slope and acts as a backstop. Several profiles reveal landward dipping reflectors above the downgoing slab, possibly depicting a subduction channel beneath the slope. Thus, the geometry of the subduction units U a young thick trench fill, only rudimental frontal accretion and a subduction channel U argues for subduction of the bulk of the sediments.

  14. Experiments on seismic behavior of back-fill gravel layer as liquefaction countermeasure of buried gas pipelines

    SciTech Connect

    Takada, Shiro; Ogawa, Yasuo; Shimizu, Kenji; Ueno, Junichi

    1995-12-31

    Experiments on seismic behavior of back-fill gravel layer as a back-fill material for buried pipelines was experimented with to investigate the effectiveness against liquefaction with a scaled model using a shaking table. A non-liquefied sandy surface layer was made with a steel mold divided into several pieces for a model. The back-fill gravel was found to be efficient for drainage but didn`t prevent liquefaction from occurring in the below layer. It was also found that the pipe doesn`t move up by buoyancy but subsides following the settlement of the back-fill gravel.

  15. Adolescent experiences of HIV and sexual health communication with parents and caregivers in Soweto, South Africa.

    PubMed

    Soon, Christine N; Kaida, Angela; Nkala, Busi; Dietrich, Janan; Cescon, Angela; Gray, Glenda; Miller, Cari L

    2013-01-01

    Communication about sexual health between parents and adolescents has been shown to have a protective influence on behaviours that reduce the risk of HIV transmission. This study explored experiences of HIV and sexual health (HSH) communication between parents and/or caregivers and adolescents in an urban HIV-endemic community in Southern Africa. Adolescents (aged 14-19 years) were recruited from the Kganya Motsha Adolescent Centre and the Kliptown community between June and August 2009. Qualitative data were collected through focus group discussions (n=10 adolescents) and semi-structured interviews (n=31 adolescents). In total, 41 adolescents (56% female, 44% male, mean age=17.2) participated in the study. Adolescent participants identified emotional, physical and sociocultural barriers to initiating HSH communication with parents and caregivers including fear of verbal warnings, threats and physical assault. Adolescents also expressed a desire for mentorship around HSH communication beyond abstinence and peer-based information. Public health interventions need to support adolescents' access to bi-directional HSH information from adult mentors that address the lived realities of adolescents beyond expectations of abstinence.

  16. Frictional Behavior of Amphibolite at Seismic Slip Rates from High-velocity Rotary Shear Experiments

    NASA Astrophysics Data System (ADS)

    Jung, S.; Ree, J.; Hirose, T.; Lee, S.

    2012-12-01

    Gabbroic rocks of oceanic crust transform into amphibolite with depth at subduction zone, and thus frictional property of amphibolite may be important for a better understanding of subduction zone earthquakes. We report preliminary results of high-velocity rotary shear experiments on amphibolite at a seismic slip rate (~1.05 m/s) and normal stresses of 2-15 MPa. Amphibolite from the Imjingang belt of South Korea is composed of hornblende (0.5-1.5 mm) and plagioclase (0.25-0.5 mm) with rare occurrence of quartz. The frictional behavior of the amphibolite is characterized by two phases of unstable slip weakening separated by strengthening, followed by a final weakening with a very low steady-state friction coefficient of 0.07. The average coefficient of the first, second and final peak frictions is 0.48, 0.36 and 0.22, respectively. The fault zone consists of a principal slip zone (PSZ, 200-300 μm thick) with molten material mantled by damage zone (1-3 mm thick). In the damage zone, the color of hornblende grains becomes darker toward the PSZ and thin, black stripes occur along cleavage planes of hornblende in plane-polarized light. Also fracture density of hornblende and plagioclase increases relative to those of wall rock. The PSZ comprises molten material and mineral clasts (25-50 μm) and the clasts tend to concentrate along the center of the PSZ. The surface temperature of the fault zones measured by a radiation thermography during experiments is about 1060°C and the internal temperature of the fault zones could be higher than the measured temperature in view of the melting of hornblende and plagioclase. The frictional behavior of amphibolite is much different from that of gabbro where the overall friction is much higher with the final peak friction of 0.84-1.09 and steady-state friction of ~0.6 (Hirose and Shimamoto, 2005 in Journal of Geophysical Research). This difference may be due to dehydration of hornblende by frictional heating and lower viscosity of

  17. Fault rupture as a series of nano-seismic events during high-velocity shear experiments

    NASA Astrophysics Data System (ADS)

    Zu, X.; Reches, Z.; Chen, X.; Chang, J. C.; Carpenter, B. M.

    2015-12-01

    The rupture process of experimental faults is investigated here by monitoring nano-seismic events (NSE) during slip in a rotary shear apparatus. Our experimental faults are made of two rock blocks with one to four miniature 3D accelerometers that are glued to the stationary block at distance of ~ 2 cm from the fault surface. Accelerations in the frequency range of 1 Hz to 200 kHz are recorded in slip-parallel (x), slip-transverse (y), and slip-vertical (z) directions. We conducted a series of 45 experiments on diorite and dolomite samples in two loading styles: classical velocity controlled loading, and power-density loading, in which the power-density (shear stress times slip velocity) is selected, and stick-slip events develop spontaneously according to the experimental fault response. The 3D accelerometer data were recorded at 106 samples/s, with acceleration resolution of 10 mV/g in recoding range of +/- 5 V. The experiments were conducted at slip-velocity of 0.001-0.8 m/s and slip distance up to 1.38 m. The accelerometer observations revealed tens to hundreds of NSEs per slip in both loading styles; peak acceleration ranged from 1g to over 500g. A typical stick-slip with tens of NSEs in Fig. 1, shows: (1) An initial NSE at ~59.72 s (green) that coincides with a small stress drop (~10%, red); (2) Simultaneous macroscopic slip initiation (blue); (3) A swarm of NSEs occur as the fault slips, each NSE lasts 1-2 milliseconds; and (4) Details of the initial NSE are shown in Fig. 2. Based on waveform cross-correlation between frequency band from 20 kHz to 70kHz, we identify several groups of NSE clusters, and apply empirical Green's function method to analyze event source spectra based on Brune-type source model. These NSEs are indicators of rupture propagation during the experimental fault slip.

  18. Legacy, legitimacy, and possibility: an exploration of community health worker experience across the generations in Khayelitsha, South Africa.

    PubMed

    Swartz, Alison

    2013-06-01

    In South Africa, the response to HIV and TB epidemics is complex, varied, and contextually defined. "Task-shifting" and a movement toward a decentralized model of care have led to an increased reliance on community health workers (CHWs) providing health care services to residents of impoverished, peri-urban areas. Public health policy tends to present CHWs as a homogeneous group, with little attention paid to the nuances of experience, motivation, and understanding, which distinguish these care workers from one another and from other kinds of health workers. An exploration of the layered meanings of providing community health care services under financially, politically, and socially difficult conditions reveals clear distinctions of experience across the generations. Many older CHWs say that ubuntu, a notion of shared African humanity, is being "killed off" by the younger generation, whereas younger CHWs often describe older women as being "jealous" of the opportunities that this younger generation has for education, training, and employment. The structure of the South African health system, past and present responses to disease epidemics, and the legacy of apartheid's structural violence have amplified these generational differences among CHWs. Using ethnographic data collected from approximately 20 CHWS in a peri-urban settlement in Cape Town, South Africa, I explore how CHWs experience and understand legitimacy in the moral economy of care. A call for closer attention to the experiences of CHWs is critical when designing public health policies for the delivery of health care services in impoverished communities in South Africa.

  19. U. S. Geological Survey begins seismic ground response experiments in Washington State

    USGS Publications Warehouse

    Tarr, A.C.; King, K.W.

    1987-01-01

    The men were Denver-based U.S Geological Survey (USGS) geophysicists working on the Urban Hazards Field Investigations project. On the previous day they had recorded two events on their seismographs-a distant nuclear explosion in Nevada and a blast at amine near Centralia, Washington. On another day, they used seismic refraction equipment to locate the depth of bedrock and seismic velocity to it at several locations in West Seattle and in the Seward Park-Brighton district of southeast Seattle. 

  20. Planning the improvement of seismic monitoring in a volcanic supersite: experience on Mt. Etna

    NASA Astrophysics Data System (ADS)

    D'Alessandro, Antonino; Scarfi, Luciano; Scaltrito, Antonio; Aiesi, Giampiero; Di Prima, Sergio; Ferrari, Ferruccio; Rapisarda, Salvatore

    2013-04-01

    Etna is one of the most active volcanoes in the world and one of the most intriguing natural laboratories for the understanding of eruptive processes and lava uprising in basalt-type volcanic environments; indeed, it is considered, by the scientific international community, together with the Vesuvius and the Hawaiian Islands, as a volcanic supersite. Its activity is continuously monitored by the Osservatorio Etneo of the Istituto Nazionale di Geofisica e Vulcanologia (INGV), by means of an array of integrated multidisciplinary techniques. In particular, Etna seismicity is recorded by a dense local seismic network (ESN- Etna Seismic Network), which, nowadays, consists of about 40 real-time seismic stations, many of which equipped with broadband velocity and accelerometer sensors. The data are analyzed routinely in detail by the Osservatorio Etneo staff, producing daily and periodic reports and bulletins of the earthquakes located in the whole Sicily and southern Calabria region. In the last decades, seismological observations provided important information on both the dynamics and internal structure of the volcano, in addition to their interaction with the regional tectonic structures. In the last year, in the framework of the VULCAMED project, an INGV workgroup has taken on the task of developing the existing seismic network through the installation of new measurement stations. By considering the spatial distribution of earthquakes in the area, the presence of structures known as seismically active and through extensive geological-geophysical surveys, ten potential new sites were identified. In the following months, some of these sites will complement the existing network. The choice of optimal sites must clearly be made through a careful analysis of environmental noise, of the possible logistics, technical and broadcast problems, but must also take into account the geometry of the existing seismic network. For this purpose, we applied the Seismic Network

  1. Ghana's experience in the establishment of a national digital seismic network observatory

    NASA Astrophysics Data System (ADS)

    Ahulu, Sylvanus; Danuor, Sylvester Kojo

    2015-07-01

    The Government of Ghana has established a National Digital Seismic Network Observatory in Ghana with the aim of monitoring events such as earthquakes, blasts from mining and quarrying, nuclear tests, etc. The Digital Observatory was commissioned on 19 December 2012, and was dedicated to Geosciences in Ghana. Previously Ghana did not have any operational, digital seismic network acquisition system with the capability of monitoring and analysing data for planning and research purposes. The Ghana Geological Survey has been monitoring seismic events with an analogue system which was not efficient and does not deliver real-time data. Hence, the importance of setting up the National Digital Seismic Network System which would enable the Geological Survey to constantly monitor, manage and coordinate both natural and man-made seismic activities in the country and around the globe, to some extent on real-time basis. The Network System is made up of six remote digital stations that transmit data via satellite to the central observatory. Sensors used are 3× Trillium Compact and 3× Trillium 120PA with Trident digitizers. The department has also acquired strong motion equipment: Titan accelerometers with Taurus digitizers from Nanometrics. Three of each of these instruments have been installed at the Akosombo and Kpong hydrodams, and also at the Weija water supply dam. These instruments are used to monitor dams. The peak ground acceleration (PGA) values established from the analysed data from the accelerometers will be used to retrofit or carry out maintenance work of the dam structures to avoid collapse. Apart from these, the observatory also assesses and analyses seismic waveforms relevant to its needs from the Global Seismographic Network (GSN) system operated by the US Geological Survey. The Ghana Geological Survey, through its Seismic Network Observatory makes data available to its stakeholder institutions for earthquake disaster mitigation; reports on all aspects of

  2. Scaling relationship between corner frequencies and seismic moments of ultra micro earthquakes estimated with coda-wave spectral ratio -the Mponeng mine in South Africa

    NASA Astrophysics Data System (ADS)

    Wada, N.; Kawakata, H.; Murakami, O.; Doi, I.; Yoshimitsu, N.; Nakatani, M.; Yabe, Y.; Naoi, M. M.; Miyakawa, K.; Miyake, H.; Ide, S.; Igarashi, T.; Morema, G.; Pinder, E.; Ogasawara, H.

    2011-12-01

    Scaling relationship between corner frequencies, fc, and seismic moments, Mo is an important clue to understand the seismic source characteristics. Aki (1967) showed that Mo is proportional to fc-3 for large earthquakes (cubic law). Iio (1986) claimed breakdown of the cubic law between fc and Mo for smaller earthquakes (Mw < 2), and Gibowicz et al. (1991) also showed the breakdown for the ultra micro and small earthquakes (Mw < -2). However, it has been reported that the cubic law holds even for micro earthquakes (-1 < Mw > 4) by using high quality data observed at a deep borehole (Abercrombie, 1995; Ogasawara et al., 2001; Hiramatsu et al., 2002; Yamada et al., 2007). In order to clarify the scaling relationship for smaller earthquakes (Mw < -1), we analyzed ultra micro earthquakes using very high sampling records (48 kHz) of borehole seismometers installed within a hard rock at the Mponeng mine in South Africa. We used 4 tri-axial accelerometers of three-component that have a flat response up to 25 kHz. They were installed to be 10 to 30 meters apart from each other at 3,300 meters deep. During the period from 2008/10/14 to 2008/10/30 (17 days), 8,927 events were recorded. We estimated fc and Mo for 60 events (-3 < Mw < -1) within 200 meters from the seismometers. Assuming the Brune's source model, we estimated fc and Mo from spectral ratios. Common practice is using direct waves from adjacent events. However, there were only 5 event pairs with the distance between them less than 20 meters and Mw difference over one. In addition, the observation array is very small (radius less than 30 m), which means that effects of directivity and radiation pattern on direct waves are similar at all stations. Hence, we used spectral ratio of coda waves, since these effects are averaged and will be effectively reduced (Mayeda et al., 2007; Somei et al., 2010). Coda analysis was attempted only for relatively large 20 events (we call "coda events" hereafter) that have coda energy

  3. Propagation of regional seismic phases (Lg and Sn) and Pn velocity structure along the Africa-Iberia plate boundary zone: tectonic implications

    NASA Astrophysics Data System (ADS)

    Calvert, Alexander; Sandvol, Eric; Seber, Dogan; Barazangi, Muawia; Vidal, Francisco; Alguacil, Gerardo; Jabour, Nacer

    2000-08-01

    We used over 1000 regional waveforms recorded by 60 seismic stations located in northwest Africa and Iberia to map the efficiency of Lg and Sn wave propagation beneath the Gulf of Cadiz, Alboran Sea and bounding Betic, Rif and Atlas mountain belts. Crustal attenuation is inferred from the tomographic inversion of Lg/Pg amplitude ratios. Upper mantle attenuation is inferred from maps of Sn propagation efficiency derived by inversion of well-defined qualitative efficiency assignments based on waveform characteristics. Regions of Lg attenuation correlate well with areas of thinned continental or oceanic crust, significant sedimentary basins, and lateral crustal variations. Comparison of the Sn efficiency results with velocities obtained from an anisotropic Pn traveltime inversion shows a fairly good correlation between regions of poor Sn efficiency and low Pn velocity. A low Pn velocity (7.6-7.8kms-1) and significant Sn attenuation in the uppermost mantle is imaged beneath the Betics in southern Spain, in sharp contrast to the relatively normal Pn velocity (8.0-8.1kms-1) and efficient Sn imaged beneath the Alboran Sea. Slow Pn velocity anomalies are also imaged beneath the Rif and Middle Atlas in Morocco. We do not identify any conclusive evidence of lithospheric-scale upper mantle attenuation beneath the Rif, although the crust in the Gibraltar region appears highly attenuating, making observations at stations in this region ambiguous. Paths crossing the Gulf of Cadiz, eastern Atlantic and the Moroccan and Iberian mesetas show very efficient Sn propagation and are imaged with high Pn velocities (8.1-8.2kms-1). The spatial distribution of attenuation and velocity anomalies lead us to conclude that some recovery of the mantle lid beneath the Alboran Sea must have occurred since the early Miocene episode of extension and volcanism. We interpret the low-velocity and attenuating regions beneath the Betics and possibly the Rif as indicating the presence of partial melt in

  4. Modelling Active Faults in Probabilistic Seismic Hazard Analysis (PSHA) with OpenQuake: Definition, Design and Experience

    NASA Astrophysics Data System (ADS)

    Weatherill, Graeme; Garcia, Julio; Poggi, Valerio; Chen, Yen-Shin; Pagani, Marco

    2016-04-01

    The Global Earthquake Model (GEM) has, since its inception in 2009, made many contributions to the practice of seismic hazard modeling in different regions of the globe. The OpenQuake-engine (hereafter referred to simply as OpenQuake), GEM's open-source software for calculation of earthquake hazard and risk, has found application in many countries, spanning a diversity of tectonic environments. GEM itself has produced a database of national and regional seismic hazard models, harmonizing into OpenQuake's own definition the varied seismogenic sources found therein. The characterization of active faults in probabilistic seismic hazard analysis (PSHA) is at the centre of this process, motivating many of the developments in OpenQuake and presenting hazard modellers with the challenge of reconciling seismological, geological and geodetic information for the different regions of the world. Faced with these challenges, and from the experience gained in the process of harmonizing existing models of seismic hazard, four critical issues are addressed. The challenge GEM has faced in the development of software is how to define a representation of an active fault (both in terms of geometry and earthquake behaviour) that is sufficiently flexible to adapt to different tectonic conditions and levels of data completeness. By exploring the different fault typologies supported by OpenQuake we illustrate how seismic hazard calculations can, and do, take into account complexities such as geometrical irregularity of faults in the prediction of ground motion, highlighting some of the potential pitfalls and inconsistencies that can arise. This exploration leads to the second main challenge in active fault modeling, what elements of the fault source model impact most upon the hazard at a site, and when does this matter? Through a series of sensitivity studies we show how different configurations of fault geometry, and the corresponding characterisation of near-fault phenomena (including

  5. Improving detection and identification of seismic signals due to landslides: a methodology based on field scale controlled experiments

    NASA Astrophysics Data System (ADS)

    Yfantis, G.; Carvajal, H. E.; Pytharouli, S.; Lunn, R. J.

    2013-12-01

    A number of published studies use seismic sensors to understand the physics involved in slope deformation. In this research we artificially induce failure to two meter scaled slopes in the field and use 12 short period 3D seismometers to monitor the failure. To our knowledge there has been no previous controlled experiments that can allow calibration and validation of the interpreted seismic signals. Inside the body of one of the artificial landslides we embed a pile of glass shards. During movement the pile deforms emitting seismic signals due to friction among the glass shards. Our aim is twofold: First we investigate whether the seismic sensors can record pre-cursory and failure signals. Secondly, we test our hypothesis that the glass shards produce seismic signals with higher amplitudes and a distinct frequency pattern, compared to those emitted by common landslide seismicity and local background noise. Two vertical faces, 2m high, were excavated 3m apart in high porous tropical clay. This highly attenuating material makes the detection of weak seismic signals challenging. Slope failure was induced by increasing the vertical load at the landslide's crown. Special care was taken in the design of all experimental procedures to not add to the area's seismic noise. Measurements took place during 18 hours (during afternoon and night) without any change in soil and weather conditions. The 3D sensors were placed on the ground surface close to the crown, forming a dense microseismic network with 5-to-10m spacing and two nanoseismic arrays, with aperture sizes of 10 and 20 m. This design allowed a direct comparison of the recorded signals emitted by the two landslides. The two faces failed for loading between 70 and 100kN and as a result the pile of glass shards was horizontally deformed allowing differential movement between the shards. After the main failure both landslides were continuing to deform due to soil compaction and horizontal displacement. We apply signal

  6. Azimuthal Seismic Anisotropy From a Multi-Component PS-wave Experiment West of Svalbard.

    NASA Astrophysics Data System (ADS)

    Haacke, R. R.; Westbrook, G. K.; Peacock, S.; Long, C.

    2005-12-01

    A high-resolution seismic experiment, using an array of closely spaced ocean-bottom seismometers, was conducted by the HYDRATECH project at a site near the intersection of the Knipovich ridge and the Molloy transform at the base of the continental slope west of Svalbard. A series of novel techniques were used to detect and characterise azimuthal anisotropy from PS waves generated on reflection to reveal the presence of horizontal transverse isotropy with depth-variable symmetry orientation. Two independent techniques for layer-stripping converted-wave data to derive the lag and orientation of the split S waves were developed, one of them an adaptation of the Alford rotation technique normally used with VSPs. The techniques were tested using synthetic anisotropic waveforms generated with the Aniseis software. These techniques were successfully applied to the experimental data, and revealed two primary anisotropic zones; an upper zone (from 30-140 mbsf) with the fast symmetry plane oriented at an azimuth of 130-140°, parallel to the local strike of the dipping seabed and which appears likely to be caused by down-slope gravitational stresses, and a lower zone (from 180 mbsf to the limit of the sampled depths) with fast symmetry plane oriented at 50-60°, near-parallel to the maximum principal stress of the tectonic regime associated with the nearby Knipovich ridge and Molloy transform zone. The shear-wave splitting accumulated at a rate of ~200 ms/km in the upper zone and at a rate of ~120 ms/km in the lower zone. Because of the nearly 90° difference in orientation of the symmetry axes of the two anisotropic layers, the net shear-wave splitting observed at the seabed increased to a peak at around 160 mbsf before decreasing again in the lower anisotropic zone as the dominant stress regime changed. A region with no azimuthal anisotropy (but which may still have VTI symmetry) centred at 160 mbsf, separates the competing stress regimes dominant in the two anisotropic

  7. Localization of short-range acoustic and seismic wideband sources: Algorithms and experiments

    NASA Astrophysics Data System (ADS)

    Stafsudd, J. Z.; Asgari, S.; Hudson, R.; Yao, K.; Taciroglu, E.

    2008-04-01

    We consider the determination of the location (source localization) of a disturbance source which emits acoustic and/or seismic signals. We devise an enhanced approximate maximum-likelihood (AML) algorithm to process data collected at acoustic sensors (microphones) belonging to an array of, non-collocated but otherwise identical, sensors. The approximate maximum-likelihood algorithm exploits the time-delay-of-arrival of acoustic signals at different sensors, and yields the source location. For processing the seismic signals, we investigate two distinct algorithms, both of which process data collected at a single measurement station comprising a triaxial accelerometer, to determine direction-of-arrival. The direction-of-arrivals determined at each sensor station are then combined using a weighted least-squares approach for source localization. The first of the direction-of-arrival estimation algorithms is based on the spectral decomposition of the covariance matrix, while the second is based on surface wave analysis. Both of the seismic source localization algorithms have their roots in seismology; and covariance matrix analysis had been successfully employed in applications where the source and the sensors (array) are typically separated by planetary distances (i.e., hundreds to thousands of kilometers). Here, we focus on very-short distances (e.g., less than one hundred meters) instead, with an outlook to applications in multi-modal surveillance, including target detection, tracking, and zone intrusion. We demonstrate the utility of the aforementioned algorithms through a series of open-field tests wherein we successfully localize wideband acoustic and/or seismic sources. We also investigate a basic strategy for fusion of results yielded by acoustic and seismic arrays.

  8. Healer shopping in Africa: new evidence from rural-urban qualitative study of Ghanaian diabetes experiences

    PubMed Central

    de-Graft Aikins, Ama

    2005-01-01

    Objectives To provide counterevidence to existing literature on healer shopping in Africa through a systematic analysis of illness practices by Ghanaians with diabetes; to outline approaches towards improving patient centred health care and policy development regarding diabetes in Ghana. Design Longitudinal qualitative study with individual interviews, group interviews, and ethnographies. Settings Two urban towns (Accra, Tema) and two rural towns (Nkoranza and Kintampo) in Ghana. Participants 26 urban people and 41 rural people with diabetes with diverse profiles (sex, age, education, socioeconomic status, diabetes status). Results Six focus groups, 20 interviews, and three ethnographical studies were conducted to explore experiences and illness practices. Analysis identified four kinds of illness practice: biomedical management, spiritual action, cure seeking (passive and active), and medical inaction. Most participants privileged biomedicine over other health systems and emphasised biomedical management as ideal self care practice. However, the psychosocial impact of diabetes and the high cost of biomedical care drove cure seeking and medical inaction. Cure seeking constituted healer shopping between biomedicine, ethnomedicine, and faith healing; medical inaction constituted passive disengagement from medical management and active engagement with faith healing. Crucially, although spiritual causal theories of diabetes existed, they were secondary to dietary, lifestyle, and physiological theories and did not constitute the primary motivation for cure seeking. Cure seeking within unregulated ethnomedical systems and non-pharmacological faith healing systems exacerbated the complications of diabetes. Conclusions To minimise inappropriate healer shopping and maximise committed biomedical and regulated ethnomedical management for Ghanaians with diabetes, the greatest challenges lie in providing affordable pharmaceutical drugs, standardised ethnomedical drugs

  9. Time-frequency-wavenumber Decomposition To Investigate Seismic Wavefield: Application To The Annot Experiment

    NASA Astrophysics Data System (ADS)

    Schissele, E.; Cansi, Y.; Gaffet, S.

    Many observations and studies as well as numerical simulations have been done in order to completely understand the whole seismogram recorded during an earthquake. At regional distances, the seismic wavefield is strongly influenced by crustal hetero- geneities. The primary wavefield constituted by Pn, Pg, Sn, Sg, Rg, Lg.... phases is diffracted and refracted by these heterogeneities and hence forms the coda of the seis- mogram. But the different mechanisms of propagation in a heterogeneous medium are not fully understood. The identification of the different phases contributing to the coda seems to be essential to progress in the comprehension of the seismic wavefield propagation. Seismic arrays are then well-adapted tools since they provide the spatio-temporal evo- lution of the wavefield. In 1998, 4 small-scales arrays were deployed for 2 months around the Annot region, located in the southern French Alps. Each array was constituted by 9 short-period seismometers, recording frequencies greater than 0.2 Hz. Its aperture was 250 meters, with a minimal distance between 2 adjacent sensors of 20 meters. That allows us to study the seismic wavefield for very low wavelength without any problem of spatial aliasing. It will be interesting to characterize in terms of wavefield deformation the signature of the different kinds of heterogeneities (fault system, topographic relief, impedance contrast...) surrounding this area. We expect the primary wavefield to be diffracted or refracted by all these heterogeneities. A time-frequency-wavenumber technique which allows us to characterize the whole coherent part of the energy which prop- agates through the seismic array has been derived. Such a characterization involves, for each coherent wavelet, an estimate of: (i) an arrival time and a frequency content and (ii) an azimuth and an apparent velocity. This way, the principal phases will be described. What will be more interesting, is the extraction of the deterministic part of the

  10. Rocky Mountain evolution: Tying Continental Dynamics of the Rocky Mountains and Deep Probe seismic experiments with receiver functions

    USGS Publications Warehouse

    Rumpfhuber, E.-M.; Keller, Gordon R.; Sandvol, E.; Velasco, A.A.; Wilson, D.C.

    2009-01-01

    In this study, we have determined the crustal structure using three different receiver function methods using data collected from the northern transect of the Continental Dynamics of the Rocky Mountains (CD-ROM) experiment. The resulting migrated image and crustal thickness determinations confirm and refine prior crustal thickness measurements based on the CD-ROM and Deep Probe experiment data sets. The new results show a very distinct and thick lower crustal layer beneath the Archean Wyoming province. In addition, we are able to show its termination at 42??N latitude, which provides a seismic tie between the CD-ROM and Deep Probe seismic experiments and thus completes a continuous north-south transect extending from New Mexico into Alberta, Canada. This new tie is particularly important because it occurs close to a major tectonic boundary, the Cheyenne belt, between an Archean craton and a Proterozoic terrane. We used two different stacking techniques, based on a similar concept but using two different ways to estimate uncertainties. Furthermore, we used receiver function migration and common conversion point (CCP) stacking techniques. The combined interpretation of all our results shows (1) crustal thinning in southern Wyoming, (2) strong northward crustal thickening beginning in central Wyoming, (3) the presence of an unusually thick and high-velocity lower crust beneath the Wyoming province, and (4) the abrupt termination of this lower crustal layer north of the Cheyenne belt at 42??N latitude. Copyright 2009 by the American Geophysical Union.

  11. HIV care and treatment experiences among female sex workers living with HIV in sub-Saharan Africa: A systematic review.

    PubMed

    Lancaster, Kathryn E; Cernigliaro, Dana; Zulliger, Rose; Fleming, Paul F

    2016-12-01

    Female sex workers (FSW) living with HIV in sub-Saharan Africa have poor engagement to HIV care and treatment. Understanding the HIV care and treatment engagement experiences of FSW has important implications for interventions to enhance care and treatment outcomes. We conducted a systematic review to examine the HIV care experiences and determinants of linkage and retention in care, antiretroviral therapy (ART) initiation, and ART adherence and viral suppression among FSW living with HIV in sub-Saharan Africa. The databases PubMed, Embase, Web of Science, SCOPUS, CINAHL, Global Health, Psycinfo, Sociological Abstracts, and Popline were searched for variations of search terms related to sex work and HIV care and treatment among sub-Saharan African populations. Ten peer-reviewed articles published between January 2000 and August 2015 met inclusion criteria and were included in this review. Despite expanded ART access, FSW in sub-Saharan Africa have sub-optimal HIV care and treatment engagement outcomes. Stigma, discrimination, poor nutrition, food insecurity, and substance use were commonly reported and associated with poor linkage to care, retention in care, and ART initiation. Included studies suggest that interventions with FSW should focus on multilevel barriers to engagement in HIV care and treatment and explore the involvement of social support from intimate male partners. Our results emphasise several critical points of intervention for FSW living with HIV, which are urgently needed to enhance linkage to HIV care, retention in care, and treatment initiation, particularly where the HIV prevalence among FSW is greatest.

  12. Passive seismic experiment - A summary of current status. [Apollo-initiated lunar surface station data

    NASA Technical Reports Server (NTRS)

    Latham, G. V.; Dorman, H. J.; Horvath, P.; Ibrahim, A. K.; Koyama, J.; Nakamura, Y.

    1978-01-01

    The data set obtained from the four-station Apollo seismic network including signals from approximately 11,800 events, is surveyed. Some refinement of the lunar model will result, but its gross features remain the same. Attention is given to the question of a small, molten lunar core, the answer to which remains dependent on analysis of signals from a far side impact. Seventy three sources of repeating, deep moonquakes have been identified, thirty nine of which have been accurately located. Concentrated at depths from 800 to 1000 km, the periodicities of these events have led to the hypothesis that they are generated by tidal stresses. Lunar seismic data has also indicated that the meteoroid population is ten times lower than originally determined from earth based observations. Lunar seismic activity is much lower and mountainous masses show no sign of sinking, in contrast to earth, as a result of the lunar crust being four times thicker. While much work remains to be done, significant correlation between terrestrial and lunar observations can be seen.

  13. The crustal structure of southern Baffin Bay: implications from a seismic refraction experiment

    NASA Astrophysics Data System (ADS)

    Suckro, Sonja K.; Gohl, Karsten; Funck, Thomas; Heyde, Ingo; Ehrhardt, Axel; Schreckenberger, Bernd; Gerlings, Joanna; Damm, Volkmar; Jokat, Wilfried

    2012-07-01

    Baffin Bay represents the northern extension of the extinct rift system in the Labrador Sea. While the extent of oceanic crust and magnetic spreading anomalies are well constrained in the Labrador Sea, no magnetic spreading anomalies have yet been identified in Baffin Bay. Thus, the nature and evolution of the Baffin Bay crust remain uncertain. To clearly characterize the crust in southern Baffin Bay, 42 ocean bottom seismographs were deployed along a 710-km-long seismic refraction line, from Baffin Island to Greenland. Multichannel seismic reflection, gravity and magnetic anomaly data were recorded along the same transect. Using forward modelling and inversion of observed traveltimes from dense airgun shots, a P-wave velocity model was obtained. The detailed morphology of the basement was constrained using the seismic reflection data. A 2-D density model supports and complements the P-wave modelling. Sediments of up to 6 km in thickness with P-wave velocities of 1.8-4.0 km s-1 are imaged in the centre of Baffin Bay. Oceanic crust underlies at least 305 km of the profile. The oceanic crust is 7.5 km thick on average and is modelled as three layers. Oceanic layer 2 ranges in P-wave velocity from 4.8 to 6.4 km s-1 and is divided into basalts and dykes. Oceanic layer 3 displays P-wave velocities of 6.4-7.2 km s-1. The Greenland continental crust is up to 25 km thick along the line and divided into an upper, middle and lower crust with P-wave velocities from 5.3 to 7.0 km s-1. The upper and middle continental crust thin over a 120-km-wide continent-ocean transition zone. We classify this margin as a volcanic continental margin as seaward dipping reflectors are imaged from the seismic reflection data and mafic intrusions in the lower crust can be inferred from the seismic refraction data. The profile did not reach continental crust on the Baffin Island margin, which implies a transition zone of 150 km length at most. The new information on the extent of oceanic crust is

  14. Fault structure, stress, or pressure control of the seismicity in shale? Insights from a controlled experiment of fluid-induced fault reactivation

    NASA Astrophysics Data System (ADS)

    De Barros, Louis; Daniel, Guillaume; Guglielmi, Yves; Rivet, Diane; Caron, Hervé; Payre, Xavier; Bergery, Guillaume; Henry, Pierre; Castilla, Raymi; Dick, Pierre; Barbieri, Ernesto; Gourlay, Maxime

    2016-06-01

    Clay formations are present in reservoirs and earthquake faults, but questions remain on their mechanical behavior, as they can vary from ductile (aseismic) to brittle (seismic). An experiment, at a scale of 10 m, aims to reactivate a natural fault by fluid pressure in shale materials. The injection area was surrounded by a dense monitoring network comprising pressure, deformation, and seismicity sensors, in a well-characterized geological setting. Thirty-two microseismic events were recorded during several injection phases in five different locations within the fault zone. Their computed magnitude ranged between -4.3 and -3.7. Their spatiotemporal distribution, compared with the measured displacement at the injection points, shows that most of the deformation induced by the injection is aseismic. Whether the seismicity is controlled by the fault architecture, mineralogy of fracture filling, fluid, and/or stress state is then discussed. The fault damage zone architecture and mineralogy are of crucial importance, as seismic slip mainly localizes on the sealed-with-calcite fractures which predominate in the fault damage zone. As no seismicity is observed in the close vicinity of the injection areas, the presence of fluid seems to prevent seismic slips. The fault core acts as an impermeable hydraulic barrier that favors fluid confinement and pressurization. Therefore, the seismic behavior seems to be strongly sensitive to the structural heterogeneity (including permeability) of the fault zone, which leads to a heterogeneous stress response to the pressurized volume.

  15. A passive and active seismic experiment near the Boso triple junction in the far northwestern part of the Pacific plate

    NASA Astrophysics Data System (ADS)

    Yamada, T.; Mochizuki, K.; Shinohara, M.; Machida, Y.; Shinbo, T.; Nakahigashi, K.; Yagi, T.; Abe, H.; Hashimoto, S.; Shoji, W.; Sato, T.; Mizuno, M.; Uehira, K.; Hino, R.; Murai, Y.; Oguma, K.

    2011-12-01

    The Pacific Plate subducts beneath northeastern Japan along the Japan Trench and beneath the Izu-Bonin-Mariana arc along the Mariana Trench. The Boso triple junction is located at between the Japan Trench and the Mariana Trench, and the southeastern end of the Sagami Trough where the Philippine Sea Plate subducts beneath northeastern Japan. It is thus a trench-trench-trench type triple junction. For the purpose of understanding the interaction between three plates and its effect to the Pacific Plate, we have performed a passive and active seismic experiment near the Boso triple junction in the far northwestern part of the Pacific plate. We deployed 10 Ocean Bottom Seismometers (OBSs) equipped with a three-componet 1Hz geophone mounted on gimbabl systems on KH09-3 cruise of R/V Hakuho-maru on July 2009, and recovered the OBSs by using M/V Shinchou-maru on October 2010.During the KH09-3 cruise, we shot by using an airgun array (6000 cubic inch in total) during 18 hours on three profiles. We obtained 442days' seismic data from July 29, 2009 to October 13, 2010 in the experiment. More than 2000 earthquakes were detected, and the foci form some clusters.

  16. Parent Participation in School Governance: A Legal Analysis of Experiences in South Africa and Kentucky

    ERIC Educational Resources Information Center

    Bathon, Justin; Beckmann, Johan; Bjork, Lars G.

    2011-01-01

    This comparative study on the educational governance systems of South Africa and the Commonwealth of Kentucky examines legal evidence from judicial decisions and administrative law to understand similarities in how school-based governance structures have been developed. We found that although school-level governance structures may provide greater…

  17. Africa Bibliographic Centre (ABC): An Experiment in African Documentation and Library Resource Sharing.

    ERIC Educational Resources Information Center

    Mascarenhas, O. C.

    This description of the Africa Bibliographic Centre (ABC) concept--which is still in a formative stage--provides brief summaries of the 12 components of the system, including an African lending library, bibliographic publishing, a commission on information and bibliographic systems, an African microfiche publications center, African abstracting…

  18. Transforming Education in South Africa: Comparative Perceptions of a South African Social Work Learning Experience

    ERIC Educational Resources Information Center

    Collins, Kathleen; Millard, Maria

    2013-01-01

    The state of tertiary education in South Africa is not adequately meeting the needs of its populace. The system in place does not effectively nor appropriately target the racial group of students which forms the democratic majority. This paper portrays the reasons why these students are not succeeding on the basis of a mismatch between their…

  19. Preliminary results of the CRISP 3D seismic experiment, offshore Costa Rica

    NASA Astrophysics Data System (ADS)

    Bangs, N. L.; McIntosh, K. D.; Silver, E. A.; Ranero, C. R.; Kluesner, J. W.; von Huene, R.; Cavanaugh, S.; Graf, S.; Cameselle, A. L.; Baracco, A. M.; Nuñez, E.

    2011-12-01

    In April and May of 2011, we acquired a new 3D seismic reflection data volume offshore Costa Rica, northwest of the Osa Peninsula. The goal of the survey was to examine the crustal structure and deformation history of this collision zone, and to clearly image the plate-boundary fault from the trench and into the seismogenic zone. These data will also help locate a deep site for riser drilling as part of the CRISP drilling program. The 3D survey covered 55 km across the upper shelf and slope, and into the trench. It extended 11 km along strike for a total survey area of 11 x 55 km. These data were acquired with the R/V Langseth using a 3300 cubic inch source shot every 50 m. We recorded the data on four 6-km-long, 468-channel streamers with 150m separation. We have preliminary results from processing 2D seismic lines extracted from the 3D volume, and from initial 3D volume processing. In the preliminary images we can trace strong seismic reflections from the plate-boundary fault down to 3 s two-way travel time (approx. 5 km depth) below the seafloor and 26 km landward from the trench. The plate-boundary fault reflection amplitudes decrease substantially with depth and are difficult to depict on these preliminary profiles. The upper plate structure shows numerous faults, many extending down to the plate-interface, and intense folding and faulting of the slope cover sequences. Currently these data are being processed by the Spanish oil company, Repsol, and should reveal far more detail with complete 3D processing.

  20. Lithology, stress or pressure control of the seismicity in shale? Insights from a controlled experiment of fluid-induced fault reactivation

    NASA Astrophysics Data System (ADS)

    Rivet, D.; De Barros, L.; Daniel, G.; Guglielmi, Y.; Castilla, R.

    2015-12-01

    Shale materials are important components in petroleum systems (e.g. sealing and source rocks) and play an important role in earthquake faults. However, their mechanical behavior is still poorly understood, as it can vary from plastic to brittle. The role of fluid pressure in seismicity triggering is also not fully understood. A unique, decametric scale experiment, which aims at reactivating a natural fault by high pressure injection, was performed in shale. The injection interval was surrounded by a dense monitoring network of pressure, deformation and seismic sensors, in a well-characterized geological setting. 37 seismic events, with very small magnitude (about -4) were recorded during five series of injections within the fault zone. The spatio-temporal distribution of these events, compared with the measured displacement at the injection points, shows that most of the induced deformation is aseismic. The locations of the microseismic events are strongly asymmetrical, with most events distributed East of the fault and South of the injection area. Focal mechanisms are predominantly consistent with shear slip on a family of calcified fractures. The shale mineralogy appears to be a critical parameter governing the seismogenic character of deformation, as only calcified structures slipped seismically. As no seismic event occurs in the close vicinity of the injection, high-fluid content seems to inhibit seismic slip. Consequently, stress changes induced by this highly-pressurized volume should more likely influence the spatial distribution of seismicity. Finally, the main fault, acting as a fluid flow and/or stress barrier, strongly modifies the stress transfer. From the monitoring point of view, this experiment reflects the difficulty in quantitatively following fluid propagation in a shale formation, as seismicity will be strongly influenced by the presence of calcified fractures and by the interaction between stress transfer and lithological heterogeneities.

  1. Effect of the surface roughness on the seismic signal generated by a single rock impact: insight from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Bachelet, Vincent; Mangeney, Anne; de Rosny, Julien; Toussaint, Renaud

    2016-04-01

    The seismic signal generated by rockfalls, landslides or avalanches is a unique tool to detect, characterize and monitor gravitational flow activity, with strong implication in terms of natural hazard monitoring. Indeed, as natural flows travel down the slope, they apply stresses on the ground, generating seismic waves in a wide frequency band. Our ultimate objective is to relate the granular flow properties to the generated signals that result from the different physical processes involved. We investigate here the more simple process: the impact of a single bead on a rough surface. Farin et al. [2015] have already shown theoretically and experimentally the existence of a link between the properties of an impacting bead (mass and velocity) on smooth surfaces, and the emitted signal (radiated elastic energy and mean frequency). This demonstrates that the single impactor properties can be deduced from the form of the emitted signal. We extend this work here by investigating the impact of single beads and gravels on rough and erodible surfaces. Experimentally, we drop glass and steel beads of diameters from 2 mm to 10 mm on a PMMA plate. The roughness of this last is obtained by gluing 3mm-diameter glass beads on one of its face. Free beads have been also added to get erodible beds. We track the dropped impactor motion, times between impacts and the generated acoustic waves using two fast cameras and 8 accelerometers. Cameras are used in addition to estimate the impactor rotation. We investigate the energy balance during the impact process, especially how the energy restitution varies as a function of the energy lost through acoustic waves. From these experiments, we clearly observe that even if more dissipative processes are involved (friction, grain reorganization, etc.), the single bead scaling laws obtained on smooth surfaces remain valid. A main result of this work is to quantify the fluctuations of the characteristic quantities such as the bounce angle, the

  2. Termination of the Batholiths marine seismic experiment: the scientific method loses to hearsay

    NASA Astrophysics Data System (ADS)

    Hollister, L. S.

    2007-12-01

    The marine seismic component of the NSF-Continental Dynamics funded project Batholiths was terminated by Canadian authorities due to environmental concerns. Socioeconomic benefits of the project were not taken into account, nor were findings by the National Research Council on effects of ocean noise on marine mammal populations. The marine seismic component of Batholiths was to have been done using sound from airguns towed behind the R/V Langseth in order to seismically image the geologic structures below the Coast Mountains of British Columbia. The project was nearly identical in timing, location, and scope to the ACCRETE project, which was successfully permitted and done in the early fall of 1994, with no detected or known damage to the environment. However, what changed in the last 13 years was a dramatic increase of concern by eNGOs (environmental non- government organizations) that airguns produced sound that might be harmful to marine species, marine mammals in particular. The marine noise concerns were amplified by eNGO agendas and campaigns to prevent oil exploration along continental margins and to shut down naval exercises involving sonar to detect submarines. Compared to these agendas, Batholiths was an easy target because the PIs (Principal Investigators) did not have the manpower or financial or legal resources (in contrast to the Navy and oil companies) to push back against an organized campaign set on stopping Batholiths. The main concern used to mobilize public opinion against Batholiths was that, if we were permitted, then oil exploration in the nearby region would be permitted; and, if oil were found, drilling would proceed: the slippery slope argument. Thus, by stopping Batholiths with the speculation that airgun noise, as used in a marine seismic study, might damage marine life, the eNGOs believe they have stopped oil exploration in British Columbia coastal waters. It is widely recognized that everything was done right to get the permits for

  3. The experience of bedaquiline implementation at a decentralised clinic in South Africa

    PubMed Central

    Cariem, R.; Cox, V.; de Azevedo, V.; Hughes, J.; Mohr, E.; Durán, L. Triviño; Ndjeka, N.

    2016-01-01

    Multidrug-resistant tuberculosis (MDR-TB) is a serious public health problem, but the new drugs bedaquiline (BDQ) and delamanid offer hope to improve outcomes and minimise toxicity. In Khayelitsha, South Africa, patients are routinely started on BDQ in the out-patient setting. This report from the field describes BDQ use in the out-patient setting at the Nolungile Clinic. The clinic staff overall report a positive experience using the drug. Challenges have been based largely on the logistics of drug supply and delivery. BDQ can be started successfully in the out-patient setting, and can be a positive experience for both patients and providers. La tuberculose multirésistante (TB-MDR) est un problème de santé publique grave, mais les nouveaux médicaments que sont la bédaquiline (BDQ) et le délamanide apportent un espoir d'améliorer les résultats tout en réduisant la toxicité. A Khayelitsha, Afrique du Sud, les patients démarrent leur traitement par BDQ en consultation externe en routine. Ce rapport du terrain décrit l'utilisation de la BDQ à la consultation externe du dispensaire Nolungile. Dans l'ensemble, le personnel du centre de santé exprime une expérience positive du médicament. Les défis ont surtout été liés à la logistique de l'approvisionnement et de la distribution du médicament. La BDQ peut être mise en route avec succès dans le cadre d'une consultation externe et peut constituer une expérience positive pour les patients et les prestataires de soins. La tuberculosis multirresistente (TB-MDR) representa un grave problema de salud pública, pero la utilización de nuevos medicamentos como la bedaquilina (BDQ) y el delamanid ofrece perspectivas de mejores desenlaces terapéuticos y disminución de la toxicidad asociada. En Khayelitsha, Suráfrica, se inicia de manera sistemática el tratamiento ambulatorio con BDQ. En el presente informe del terreno, se describe la utilización de BDQ en tratamiento antituberculoso ambulatorio en el

  4. The experience of bedaquiline implementation at a decentralised clinic in South Africa.

    PubMed

    Cariem, R; Cox, V; de Azevedo, V; Hughes, J; Mohr, E; Durán, L Triviño; Ndjeka, N; Furin, J

    2016-09-01

    Multidrug-resistant tuberculosis (MDR-TB) is a serious public health problem, but the new drugs bedaquiline (BDQ) and delamanid offer hope to improve outcomes and minimise toxicity. In Khayelitsha, South Africa, patients are routinely started on BDQ in the out-patient setting. This report from the field describes BDQ use in the out-patient setting at the Nolungile Clinic. The clinic staff overall report a positive experience using the drug. Challenges have been based largely on the logistics of drug supply and delivery. BDQ can be started successfully in the out-patient setting, and can be a positive experience for both patients and providers. La tuberculose multirésistante (TB-MDR) est un problème de santé publique grave, mais les nouveaux médicaments que sont la bédaquiline (BDQ) et le délamanide apportent un espoir d'améliorer les résultats tout en réduisant la toxicité. A Khayelitsha, Afrique du Sud, les patients démarrent leur traitement par BDQ en consultation externe en routine. Ce rapport du terrain décrit l'utilisation de la BDQ à la consultation externe du dispensaire Nolungile. Dans l'ensemble, le personnel du centre de santé exprime une expérience positive du médicament. Les défis ont surtout été liés à la logistique de l'approvisionnement et de la distribution du médicament. La BDQ peut être mise en route avec succès dans le cadre d'une consultation externe et peut constituer une expérience positive pour les patients et les prestataires de soins. La tuberculosis multirresistente (TB-MDR) representa un grave problema de salud pública, pero la utilización de nuevos medicamentos como la bedaquilina (BDQ) y el delamanid ofrece perspectivas de mejores desenlaces terapéuticos y disminución de la toxicidad asociada. En Khayelitsha, Suráfrica, se inicia de manera sistemática el tratamiento ambulatorio con BDQ. En el presente informe del terreno, se describe la utilización de BDQ en tratamiento antituberculoso ambulatorio en el

  5. Calibration formulae and values for velocity seismometers used in the 1998 Santa Clara Valley, California seismic experiment

    USGS Publications Warehouse

    Lindh, Allan G.; Eaton, Jerry P.; O'Neill Allen, Mary; Healy, John H.; Stewart, Samuel W.; Damerell, Lu

    1999-01-01

    Eaton (1975), Bakun and Dratler (1976), Eaton (1977), Healy and O’Neil (1977), Asten (1977), Stewart and O'Neill (1980), Liu and Peselnick (1986), Eaton (1991), Rodgers et al. (1995), and many others (see Asten (1977) for a list of earlier references) have presented formulae for calculating the damped generator constant (or motor constant), and the damping constant (or fractional damping ratio) for magnetically damped velocity seismometers. Unfortunately the notation varies between authors, and not all the formulae allow for some of the significant variables -- differences in input impedance of the recording system in particular. This has become particularly relevant because the USGS seismic networks in California have traditionally set up their velocity sensors for the 10K Ohm impedance of the standard USGS analog telemetry systems (Eaton, 1977), but modern digital recording systems are usually set up with high input impedances, often of a megaohm or greater. Thus the nominal calibration values valid for USGS velocity sensors in their “normal” configuration are incorrect when they are recorded on other systems. In this short note we have collected the relevant formulae needed, and computed the seismometer responses for the various velocity sensors used in the recent Santa Clara Valley Seismic Experiment (SCVSE, see Lindh et al., 1999).

  6. South Africa's early experiment in social medicine: its pioneers and politics.

    PubMed Central

    Marks, S

    1997-01-01

    The election of a democratic, nonracial government in South Africa has moved the health needs of the majority of the population to center stage. In the search for precedents, health policymakers have turned to South Africa's pioneering of health centers and social medicine in the 1940s. This paper looks at the intellectual context in which these ideas were first developed; the particular political circumstances and relationships between doctors and the state in the late 1930s, which facilitated the establishment of health centers; the role that the health centers were intended to play in South Africa's wider postwar health plans; and the reasons for the centers' failure. Contrary to conventional wisdom, it argues that the failure of the health centers and the wider health plans predated the advent of the National Party to power in 1948, and resulted mainly from the marginalization of the centers as a low-cost option for the poor, which was itself a consequence of underfunding and the vested interests of local health authorities and private practitioners. PMID:9096553

  7. Pediatric Neuropathology in Africa: Local Experience in Nigeria and Challenges and Prospects for the Continent.

    PubMed

    Olasode, Babatunde J; Onyia, Chiazor U

    2016-09-15

    The present state of pediatric neuropathology practice is in rudimentary developmental stages in most parts of sub-Saharan Africa. We sought to determine the pattern of neurosurgical lesions in children diagnosed in southwestern Nigeria and briefly address issues surrounding the practice of this aspect of pathology in Africa. We performed a retrospective review of histopathologic results of biopsies obtained from pediatric patients with neurosurgical lesions at the Department of Pathology, Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria, between January 2001 and December 2011. Demographic and clinical data were extracted from the Ife-Ijesha cancer registry and histopathological diagnoses were confirmed. A total of 111 biopsies were reviewed with a maximum of 17 in 2001 and minimum of 3 in 2005. Patient ages ranged between 1 day and 16 years with a male:female ratio of 1.02:1. There were 53 spinal lesions, 15 intracranial lesions, 36 scalp masses, 6 skull lesions and 1 muscle biopsy. Most of the specimens were from myelomeningoceles. This documentation of the major types of pediatric neurological conditions encountered in clinical practice in this relatively resource-limited setting indicate the need for collaboration with better developed centers to improve training in neurosurgery and neuropathology to enhance the quality of clinical care for young patients in Africa.

  8. Theoretical and practical considerations for the design of the iMUSH active-source seismic experiment

    NASA Astrophysics Data System (ADS)

    Kiser, E.; Levander, A.; Harder, S. H.; Abers, G. A.; Creager, K. C.; Vidale, J. E.; Moran, S. C.; Malone, S. D.

    2013-12-01

    The multi-disciplinary imaging of Magma Under St. Helens (iMUSH) experiment seeks to understand the details of the magmatic system that feeds Mount St. Helens using active- and passive-source seismic, magnetotelluric, and petrologic data. The active-source seismic component of this experiment will take place in the summer of 2014 utilizing all of the 2600 PASSCAL 'Texan' Reftek instruments which will record twenty-four 1000-2000 lb shots distributed around the Mount St. Helens region. The instruments will be deployed as two consecutive refraction profiles centered on the volcano, and a series of areal arrays. The actual number of areal arrays, as well as their locations, will depend strongly on the length of the experiment (3-4 weeks), the number of instrument deployers (50-60), and the time it will take per deployment given the available road network. The current work shows how we are balancing these practical considerations against theoretical experiment designs in order to achieve the proposed scientific goals with the available resources. One of the main goals of the active-source seismic experiment is to image the magmatic system down to the Moho (35-40 km). Calculating sensitivity kernels for multiple shot/receiver offsets shows that direct P waves should be sensitive to Moho depths at offsets of 150 km, and therefore this will likely be the length of the refraction profiles. Another primary objective of the experiment is to estimate the locations and volumes of different magma accumulation zones beneath the volcano using the areal arrays. With this in mind, the optimal locations of these arrays, as well as their associated shots, are estimated using an eigenvalue analysis of the approximate Hessian for each possible experiment design. This analysis seeks to minimize the number of small eigenvalues of the approximate Hessian that would amplify the propagation of data noise into regions of interest in the model space, such as the likely locations of magma

  9. Work Experience, Job-Fulfillment and Burnout among VMMC Providers in Kenya, South Africa, Tanzania and Zimbabwe

    PubMed Central

    Perry, Linnea; Rech, Dino; Mavhu, Webster; Frade, Sasha; Machaku, Michael D.; Onyango, Mathews; Aduda, Dickens S. Omondi.; Fimbo, Bennett; Cherutich, Peter; Castor, Delivette; Njeuhmeli, Emmanuel; Bertrand, Jane T.

    2014-01-01

    Background Human resource capacity is vital to the scale-up of voluntary medical male circumcision (VMMC) services. VMMC providers are at risk of “burnout” from performing a single task repeatedly in a high volume work environment that produces long work hours and intense work effort. Methods and findings The Systematic Monitoring of the Voluntary Medical Male Circumcision Scale-up (SYMMACS) surveyed VMMC providers in Kenya, South Africa, Tanzania, and Zimbabwe in 2011 (n = 357) and 2012 (n = 591). Providers self-reported on their training, work experience, levels of job-fulfillment and work fatigue/burnout. Data analysis included a descriptive analysis of VMMC provider characteristics, and both bivariate and multivariate analyses of factors associated with provider work fatigue/burnout. In 2012, Kenyan providers had worked in VMMC for a median of 31 months compared to South Africa (10 months), Tanzania (15 months), and Zimbabwe (11 months). More than three-quarters (78 – 99%) of providers in all countries in 2012 reported that VMMC is a personally fulfilling job. However, 67% of Kenyan providers reported starting to experience work fatigue/burnout compared to South Africa (33%), Zimbabwe (17%), and Tanzania (15%). Despite the high level of work fatigue/burnout in Kenya, none of the measured factors (i.e., gender, age, full-time versus part-time status, length of service, number of operations performed, or cadre) were significantly associated with work fatigue/burnout in 2011. In 2012, logistic regression found increases in age (p<.05) and number of months working in VMMC (p<.01) were associated with an increased likelihood of experiencing work fatigue/burnout, while higher career total VMMCs decreased the likelihood of experiencing burnout. Conclusion Given cross-country differences, further elucidation of cultural and other contextual factors that may influence provider burnout is required. Continuing to emphasize the contribution that providers

  10. Simulation of complete seismic surveys for evaluation of experiment design and processing

    SciTech Connect

    Oezdenvar, T.; McMechan, G.A.; Chaney, P.

    1996-03-01

    Synthesis of complete seismic survey data sets allows analysis and optimization of all stages in an acquisition/processing sequence. The characteristics of available survey designs, parameter choices, and processing algorithms may be evaluated prior to field acquisition to produce a composite system in which all stages have compatible performance; this maximizes the cost effectiveness for a given level of accuracy, or for targets with specific characteristics. Data sets synthesized for three salt structures provide representative comparisons of time and depth migration, post-stack and prestack processing, and illustrate effects of varying recording aperture and shot spacing, iterative focusing analysis, and the interaction of migration algorithms with recording aperture. A final example demonstrates successful simulation of both 2-D acquisition and processing of a real data line over a salt pod in the Gulf of Mexico.

  11. The Tectonic Evolution of SE Canada: Seismic Evidence from the QM-III Experiment

    NASA Astrophysics Data System (ADS)

    Bastow, I. D.; Boyce, A.; Darbyshire, F. A.; Levin, V. L.; Menke, W. H.; Ellwood, A.

    2014-12-01

    Much of the geological record can be interpreted in the context of processes operating today at plate boundaries. This works well to explain processes and products during the Phanerozoic era; during Precambrian times when the oldest rocks were forming, however, conditions on the younger, hotter, more ductile Earth were likely very different, making analogies with modern day tectonics less certain. Gathering evidence preserved deep within the plates in the shields is thus essential to improve our understanding of the early Earth. Shields are usually underlain by thick, seismically fast roots that are absent beneath younger portions of Earth's surface. The thermochemically distinct nature of cratonic roots is often associated with Archean processes such as the extraction of komatiitic magmas. However, the cratonic core of North America does not fit easily into this Archean formation paradigm: part of the Canadian shield extends beneath the Archean Superior craton, but much of it persists beneath younger Proterozoic crust as well. We present here a relative arrival-time tomographic study of mantle seismic structure using data from a new seismograph network operating in SE Canada. Our stations extend from the Archean Superior craton around the southern tip of Hudson Bay, through Proterozoic Grenville terranes, and into Paleozoic coastal Maine and Nova Scotia. Tomographic images display three broad zones of mantle wavespeed: slow in the Appalachian terranes; fast in the Grenville Province; very fast within the Superior craton. Archean lithosphere has been modified by the Great Meteor hotspot, but we find no evidence for major plate-scale underthrusting during the Grenville orogeny. The abrupt wavespeed transition from Archean to Proterozoic mantle is thus consistent with the emerging consensus that keels form in two stages: a chemically depleted layer in Archean times followed by the thermal development of a less-depleted lithosphere during Proterozoic times.

  12. Crustal structure of the SW-Moroccan margin from wide-angle and reflection seismic data (the DAKHLA experiment) Part A: Wide-angle seismic models

    NASA Astrophysics Data System (ADS)

    Klingelhoefer, F.; Labails, C.; Cosquer, E.; Rouzo, S.; Géli, L.; Aslanian, D.; Olivet, J.-L.; Sahabi, M.; Nouzé, H.; Unternehr, P.

    2009-04-01

    A total 1500 km of seismic reflection and wide-angle profiles were acquired off the southern Moroccan margin during the DAKHLA cruise, a joint project of Ifremer, the Universities of Brest, El Jadida and Lisbon and Total. The shots along two profiles parallel to the margin and two profiles perpendicular to the margin were also recorded by ocean bottom seismometers (OBS). The profiles perpendicular to the margin were additionally extended on land using 14 stations on the northern profile and 11 stations on the southern profile. Modelling of the reflection and wide-angle seismic data reveals a 10 km deep sedimentary basin including two high velocity carbonate layers. Lateral crustal thinning is observed from a 27 km thick crystalline continental crust to a 7 km thick oceanic crust occurring over less than 100 km. The crystalline continental crust can be divided into two distinct layers of 12 and 15 km thickness. The oceanic crust east of the magnetic anomaly M25 displays higher velocities in layer 3 than west of the magnetic anomaly. The change in seismic velocity suggests a possible link to changes in accretionary processes of the oceanic crust. Some regions show seismic velocities between 6.8 and 7.4 km/s which could be explained by slightly elevated mantle temperatures during accretion of the crust.

  13. An in-situ stimulation experiment in crystalline rock - assessment of induced seismicity levels during stimulation and related hazard for nearby infrastructure

    NASA Astrophysics Data System (ADS)

    Gischig, Valentin; Broccardo, Marco; Amann, Florian; Jalali, Mohammadreza; Esposito, Simona; Krietsch, Hannes; Doetsch, Joseph; Madonna, Claudio; Wiemer, Stefan; Loew, Simon; Giardini, Domenico

    2016-04-01

    A decameter in-situ stimulation experiment is currently being performed at the Grimsel Test Site in Switzerland by the Swiss Competence Center for Energy Research - Supply of Electricity (SCCER-SoE). The underground research laboratory lies in crystalline rock at a depth of 480 m, and exhibits well-documented geology that is presenting some analogies with the crystalline basement targeted for the exploitation of deep geothermal energy resources in Switzerland. The goal is to perform a series of stimulation experiments spanning from hydraulic fracturing to controlled fault-slip experiments in an experimental volume approximately 30 m in diameter. The experiments will contribute to a better understanding of hydro-mechanical phenomena and induced seismicity associated with high-pressure fluid injections. Comprehensive monitoring during stimulation will include observation of injection rate and pressure, pressure propagation in the reservoir, permeability enhancement, 3D dislocation along the faults, rock mass deformation near the fault zone, as well as micro-seismicity. The experimental volume is surrounded by other in-situ experiments (at 50 to 500 m distance) and by infrastructure of the local hydropower company (at ~100 m to several kilometres distance). Although it is generally agreed among stakeholders related to the experiments that levels of induced seismicity may be low given the small total injection volumes of less than 1 m3, detailed analysis of the potential impact of the stimulation on other experiments and surrounding infrastructure is essential to ensure operational safety. In this contribution, we present a procedure how induced seismic hazard can be estimated for an experimental situation that is untypical for injection-induced seismicity in terms of injection volumes, injection depths and proximity to affected objects. Both, deterministic and probabilistic methods are employed to estimate that maximum possible and the maximum expected induced

  14. The return of the Pholela experiment: medical history and primary health care in post-Apartheid South Africa.

    PubMed

    Phillips, Howard

    2014-10-01

    I examine why South Africa's pioneering Pholela model of primary health care, dating from the 1940s, held such appeal for the country's new policymakers after 1994, and why those policymakers have failed to make it the basis of an effective public health care system since then. In the 1940s, the innovative Pholela experiment had served as such a model, to be replicated gradually throughout the country until a new health care system in its image was finally in place. However, this vision was dashed by the hostility of the mainstream medical profession and, after 1948, even more so by the new apartheid government, causing the idea to wither and become no more than a vanishing memory. In the 1990s, the model resurfaced as part of the country's transition to democracy, eliciting great enthusiasm among a new generation of health policymakers. I conclude by looking at the fate to date of this second coming of the Pholela experiment.

  15. First results on the Experiment FESTER on optical turbulence over False Bay South Africa: dependencies and consequences

    NASA Astrophysics Data System (ADS)

    Sprung, Detlev; van Eijk, Alexander M. J.; Sucher, Erik; Eisele, Christian; Seiffer, Dirk; Stein, Karin

    2016-10-01

    The experiment FESTER (First European South African Transmission ExpeRiment) took place in 2015 to investigate the atmospheric influence on electro-optical systems performance across False Bay / South Africa on a long term basis. Several permanent stations for monitoring electro-optical propagation and atmospheric parameters were set up around the Bay. Additional intensive observation periods (IOPs) allowed for boat runs to assess the inhomogeneous atmospheric propagation conditions over water. In this paper we focus on the distribution of optical turbulence over the Bay. The different impact of water masses originating from the Indian Ocean and the Benguela current on the development of optical turbulence is discussed. The seasonal behavior of optical turbulence is presented and its effect on electro-optical system performance examined.

  16. The experience of the Antarctic Seismic Data Library System (SDLS) as a hub for researchers in antarctic crustal studies.

    NASA Astrophysics Data System (ADS)

    Diviacco, Paolo; Wardell, Nigel

    2010-05-01

    The SDLS was created in April 1991 under the auspices of the Scientific Committee on Antarctic Research to provide open access to Antarctic multichannel seismic-reflection data (MCS) for use in cooperative research projects. The SDLS operates under the mandates of the Antarctic Treaty System, by which all institutions that collect MCS data in Antarctica must submit their MCS data to the SDLS. The SDLS has library branches worldwide at which researchers may view and study the MCS data. MCS data are submitted to the SDLS within 4 years of collection and remain in the library under SDLS guidelines until 8 years after collection. Thereafter, the data go to World Data Centers or equivalents for unrestricted use. The SDLS offers a clearing house, based at Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) where data are processed when needed and georeferenced, so that the end user can be provided with usable, although basic, post-stack seismic sections. Re-processing of data is beyond the scope of the SDLS, so that if a researcher is interested in reviewing pre-stack data he/she must resort to the data owner. So far 228,000 km of seismic data have been made public in all sectors of the Antarctic region. To augment the concept of physical repositories where data can be accessed by researchers travelling to one of the branches or from where data could be copied to digital media and sent to users, in 2003 it was decided to develop a web interface where data could be searched for and accessed directly. At that moment no previous non-commercial experience was available in this data field, so that the system was designed from scratch. Several technologies were introduced, tested, and after a period of use, reviewed and tuned. Particular attention was devoted to the seismic data viewing facility, which was tailored to the needs of a community with specific practices and legacies. Seismic data are sensitive data that are very important for the E&P industry, so

  17. Wide-Angle Seismic Experiment Across the Oeste Fault Zone, Central Andes, Northern Chile.

    NASA Astrophysics Data System (ADS)

    Lorenzo, J. M.; Yáñez, G. A.; Vera, E. E.; Sepúlveda, J.

    2008-12-01

    From December 6-21, 2007, we conducted a 3-component, radio-telemetric, seismic survey along a ~ 15-km wide E-W transect in the Central Andes, at a latitude of ~ 22.41° S, centered north of the city of Calama (68.9° W), Chile. The study area is sandwiched between the Central Depression in the west and the Andean Western Cordillera of Chile. Recording stations, nominally spaced at intervals of either 125 or 250 m collected up to 3.5 s of refracted seismic arrivals at maximum source-receiver offsets exceeding 15 km. Ten shothole sources, spaced 2-6 km apart focused energy on the shallow (0-3 km), crustal, Paleogene-age structures. Preliminary, tomographic inversions of refracted first arrivals show the top of a shallow (< 1km), high- velocity (VP, ~5 km/s) crust, deepening sharply eastward to at least 2 km. At the surface, this central basement step correlates to a regionally extensive (> 600 km), strike-slip fault zone known as the Oeste fault. Turning ray densities suggest the base of the overlying velocity gradient unit (VP, 2-4 km/s) dips inwardly from both east and west directions toward the Oeste fault to depths of almost 1 km. Plate reorganization commencing at least by the latter half of the Oligocene led from oblique to more orthogonal convergence between the South American and the Nazca (Farallon) Plates. We interpret previously mapped, older, minor faults as being generated within the right-lateral, orogen-parallel, Oeste strike-slip fault zone, and postdated by Neogene, N-S striking thrust faults. In this context we also interpret that the spatial distribution of velocity units requires an period of extensional activity that may (1) postdate the transpressional strike slip fault activity of the Neogene, (2) be related to a later releasing bend through the translation and interaction of rigid blocks hidden at depth or even (3) be the consequence of inelastic failure from the result of flexural loading.

  18. Seismic velocity structure and spatial distribution of reflection intensity off the Boso Peninsula, Central Japan, revealed by an ocean bottom seismographic experiment

    NASA Astrophysics Data System (ADS)

    Kono, Akihiro; Sato, Toshinori; Shinohara, Masanao; Mochizuki, Kimihiro; Yamada, Tomoaki; Uehira, Kenji; Shinbo, Takashi; Machida, Yuuya; Hino, Ryota; Azuma, Ryosuke

    2016-04-01

    Off the Boso Peninsula, central Japan, where the Sagami Trough is in the south and the Japan Trench is in the east, there is a triple junction where the Pacific plate (PAC), the Philippine Sea plate (PHS) and the Honshu island arc (HIA) meet each other. In this region, the PAC subducts beneath the PHS and the HIA, and the PHS subducts beneath the HIA. Due to the subduction of 2 oceanic plates, numerous seismic events took place in the past. In order to understand these events, it is important to image structure of these plates. Hence, many researchers attempted to reveal the substructure from natural earthquakes and seismic experiments. Because most of the seismometers are placed inland area and the regular seismicity off Boso is inactive, it is difficult to reveal the precise substructure off Boso area using only natural earthquakes. Although several marine seismic experiments using active sources were conducted, vast area remains unclear off Boso Peninsula. In order to improve the situation, a marine seismic experiment, using airgun as an active source, was conducted from 30th July to 4th of August, 2009. The survey line has 216 km length and 20 Ocean Bottom Seismometers (OBSs) were placed on it. We estimated 2-D P-wave velocity structure from the airgun data using the PMDM (Progressive Model Development Method; Sato and Kenett, 2000) and the FAST (First Arrival Seismic Tomography ; Zelt and Barton, 1998). Furthermore, we identified the probable reflection phases from the data and estimated the location of reflectors using Travel time mapping method (Fujie et al. 2006). We found some reflection phases from the data, and the reflectors are located near the region where P-wave velocity is 5.0 km/s. We interpret that the reflectors indicate the plate boundary between the PHS and the HIA. The variation of the intensity of reflection along the upper surface of PHS seems to be consistent with the result from previous reflection seismic experiment conducted by Kimura et

  19. The Grenville Front Tectonic Zone: Results from the 1986 Great Lakes Onshore Seismic Wide-Angle Reflection and Refraction Experiment

    NASA Astrophysics Data System (ADS)

    Epili, Duryodhan; Mereu, Robert F.

    1991-09-01

    The Grenville Front, which marks the orogenic boundary between the Archean Superior Structural Province and the much younger Grenville Province to the southeast, is one of the major tectonic features of the Canadian Shield. Within Canada, it is approximately 1900 km in length extending from the north shore of Lake Huron across Ontario and Quebec to Labrador. In 1986, a major coincident onship near-vertical reflection and onshore wide-angle reflection/refraction experiment (GLIMPCE-Great Lakes International Multidisciplinary Program on Crustal Evolution) was conducted along a series of lines across the Great lakes. One of the lines, line J, ran across Georgian Bay and Lake Huron for a distance of 350 km and crossed the Grenville Front Tectonic Zone (GFTZ). The seismic signals from the air gun array source were well recorded by the onshore stations up to distances of 250 km with a seismic trace spacing of 50-62.5 m. The GFTZ had a profound effect on the nature of the reflector patterns observed on the onshore seismic sections. Data recorded by the stations on the east end of the line indicate that the crustal P phases are very complex and form a "shinglelike" pattern of reflected waves. Data recorded by stations at the center and at the western end of the line show that the Pg phases are normal and lack the shinglelike appearance. This character of arrivals was also observed on the corresponding S wave sections. A combined P and S wave forward modeling analysis shows that the GFTZ is composed of bands of reflectors dipping at angles of 20°-35° extending to the lower crust. These reflectors were also well imaged on the coincident near-vertical reflection data. Reflectors under the Britt domain to the east of the GFTZ have a shallower dip than those along the zone. The structure of the crust under the Manitoulin terrane to the west of the GFTZ is laterally homogeneous with a major intracrustal reflector at a depth of 17-20 km below the surface. Poisson's ratio is

  20. Amplitude and phase normalization of seismograms from multiple seismograph recording systems for the Yellowstone-Snake River Plain seismic refraction experiment

    SciTech Connect

    Baker, M.R.; Braile, L.W.; Smith, R.B.

    1982-04-10

    A z transform filter theory method for the normalization of the instrument responses of several seismographs is presented. In this method, an inverse filter is derived by consideration of the seismometer/recorder characteristics which may be applied to a given seismogram to convert the system frequency response to that of a reference system. Inverse filters are derived for the seismographs used on the 1978 Yellowstone-Snake River Plain seismic profiling experiment. It is shown by application to these data that the inverse filters are effective in amplitude normalization and that their use allows improvement in the amplitude and waveform character of seismic record sections.

  1. Lithospheric structure beneath Central Europe from the POLONAISE'97, CELEBRATION 2000, ALP 2002, and SUDETES 2003 seismic refraction experiments

    NASA Astrophysics Data System (ADS)

    Guterch, A.; Grad, M.; Keller, G. R.

    2005-12-01

    Beginning in 1997, Central Europe between the Baltic and Adriatic Seas, has been covered by an unprecedented network of seismic refraction experiments POLONAISE'97, CELEBRATION 2000, ALP 2002, and SUDETES 2003, have only been possible due to a massive international consortium consisted of more than 30 institutions from 16 countries in Europe and North America. The majority of recording instruments was provided by the IRIS/PASSCAL Instrument Center and the University of Texas at El Paso (USA), and several other countries also provided instrumentation. Total length of seismic profiles in all experiments is about 20,000 km. The main results of these experiments are: 1) the delineation of the deep structure of the southwestern margin of the East European Craton (southern Baltica) and its relationship to younger terranes; delineation of the major terranes and crustal blocks in the Trans European Suture Zone; determination of the structural framework of the Pannonian basin; elucidation of the deep structure and evolution of the Western Carpathian Mountains and Eastern Alps; determination of the structural relationships between the structural elements of the Bohemian massif and adjacent features; construction of 3-D models of the lithospheric structure; and evaluation and develop geodynamic models for the tectonic evolution of the region. Experiment Working Groups Members: K. Aric, M. Behm, E. Brueckl, W. Chwatal, H. Grassl, S. Hock, V. Hoeck, F. Kohlbeck, E.-M. Rumpfhuber, Ch. Schmid, R. Schmoller, C. Tomek, Ch. Ullrich, F.Weber (Austria), A.A. Belinsky (Belarus), I. Asudeh, R. Clowes, Z. Hajnal (Canada), F. Sumanova (Croatia), M. Broz , P. Hrubcova, M. Korn, O. Karousova, J. Malek, A. Spicak (Czech Republic), S.L. Jensen, P. Joergensen, H. Thybo (Denmark), K. Komminaho, U. Luosto, T. Tiira, J. Yliniemi (Finland), F. Bleibinhaus, R. Brinkmann, B. Forkmann, H. Gebrande, H. Geissler, A. Hemmann, G. Jentzsch, D. Kracke, A. Schulze, K. Schuster (Germany), T. Bodoky, T

  2. Lidar Observations of Tropospheric Aerosols Over Northeastern South Africa During the ARREX and SAFARI-2000 Dry Season Experiments

    NASA Technical Reports Server (NTRS)

    Campbell, James R.; Welton, Ellsworth J.; Spinhirne, James D.; Ji, Qiang; Tsay, Si-Chee; Piketh, Stuart J.; Barenbrug, Marguerite; Holben, Brent; Starr, David OC. (Technical Monitor)

    2002-01-01

    During the ARREX-1999 and SAFARI-2000 Dry Season experiments a micropulse lidar (523 nm) instrument was operated at the Skukuza Airport in northeastern South Africa. The Mar was collocated with a diverse array of passive radiometric equipment. For SAFARI-2000 the processed Mar data yields a daytime time-series of layer mean/derived aerosol optical properties, including extinction-to-backscatter ratios and vertical extinction cross-section profile. Combined with 523 run aerosol optical depth and spectral Angstrom exponent calculations from available CIMEL sun-photometer data and normalized broadband flux measurements the temporal evolution of the near surface aerosol layer optical properties is analyzed for climatological trends. For the densest smoke/haze events the extinction-to-backscatter ratio is found to be between 60-80/sr, and corresponding Angstrom exponent calculations near and above 1.75. The optical characteristics of an evolving smoke event from SAFARI-2000 are extensively detailed. The advecting smoke was embedded within two distinct stratified thermodynamic layers, causing the particulate mass to advect over the instrument array in an incoherent manner on the afternoon of its occurrence. Surface broadband flux forcing due to the smoke is calculated, as is the evolution in the vertical aerosol extinction profile as measured by the Han Finally, observations of persistent elevated aerosol during ARREX-1999 are presented and discussed. The lack of corroborating observations the following year makes these observation; both unique and noteworthy in the scope of regional aerosol transport over southern Africa.

  3. Lower crustal deformation beneath the central Transverse Ranges, southern California: Results from the Los Angeles Region Seismic Experiment

    USGS Publications Warehouse

    Godfrey, N.J.; Fuis, G.S.; Langenheim, V.; Okaya, D.A.

    2002-01-01

    We present a P wave velocity model derived from active source seismic data collected during the 1994 Los Angeles Region Seismic Experiment. Our model extends previously published upper crustal velocity models to mantle depths. Our model was developed by both ray tracing through a layered model and calculating travel times through a gridded model. It includes an 8-km-thick crustal root centered beneath the surface trace of the San Andreas fault, north of the highest topography in the San Gabriel Mountains. A simple mass balance calculation suggests that ???36 km of north-south shortening across the San Andreas fault in the central Transverse Ranges could have formed this root. If north-south compression began when the "Big Bend" in the San Andreas fault formed at ???5 Ma, 36 km of shortening implies a north-south contraction rate of ???7.1 mm/yr across the central Transverse Ranges. If, instead, north-south compression began when the Transverse Ranges formed at 3.4-3.9 Ma, 36 km of shortening implies a contraction rate of 9.2-10.6 mm/yr. North of the San Andreas fault, the Mojave Desert crust has a low-velocity (6.3 km/s) mid and lower crust and a 28-km-deep Moho. South of the San Andreas fault, beneath the Los Angeles and San Gabriel Valley basins, there is a fast (6.6-6.8 km/s), thick (10-12 km) lower crust with a 27-km-deep Moho. Farther south still, the lower crust of the Continental Borderland is fast (6.6-6.8 km/s) and thin (5 km) with a shallow (22 km deep) Moho.

  4. Seismicity of the Earth 1900-2013 East African Rift

    USGS Publications Warehouse

    Hayes, Gavin P.; Jones, Eric S.; Stadler, Timothy J.; Barnhart, William D.; McNamara, Daniel E.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio; Hayes, Gavin P.; Jones, Eric S.; Stadler, Timothy J.; Barnhart, William D.; McNamara, Daniel E.; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio

    2014-01-01

    Rifting in East Africa is not all coeval; volcanism and faulting have been an ongoing phenomenon on the continent since the Eocene (~45 Ma). The rifting began in northern East Africa, and led to the separation of the Nubia (Africa) and Arabia plates in the Red Sea and Gulf of Aden, and in the Lake Turkana area at the Kenya-Ethiopia border. A Paleogene mantle superplume beneath East Africa caused extension within the Nubia plate, as well as a first order topographic high known as the African superswell which now includes most of the eastern and southern sectors of the Nubia plate. Widespread volcanism erupted onto much of the rising plateau in Ethiopia during the Eocene-Oligocene (45–29 Ma), with chains of volcanoes forming along the rift separating Africa and Arabia. Since the initiation of rifting in northeastern Africa, the system has propagated over 3,000 km to the south and southwest, and it experiences seismicity as a direct result of the extension and active magmatism.

  5. Remote sensing experiment in West Africa. [drought effects on desert agriculture and vegetation in Niger

    NASA Technical Reports Server (NTRS)

    Macleod, N. H.

    1974-01-01

    There are substantial needs of the Sahelien Zone to detail the state of regional agricultural resources in the face of a sixth year of serious drought conditions. While most of the work has been done in the Republic of Niger, the principles which have emerged from the analysis seem to be applicable to much of the Sahel. The discussion relates to quite specific rehabilitation and development initiations under consideration in Niger which are based in part upon direct analysis of ERTS imagery of the country, in part on field surveys and on discussions with Nigerian officials and technicians. Again, because the entire Sahelien Zone (including Niger) has large zones of similar ecologic characteristics, modificiations of the approaches suggested for Niger are applicable to the solution of rehabilitation of the desert, the savannah and the woodlands of West Africa in general.

  6. Crustal Structure, Seismic Anisotropy and Deformations of the Ediacaran/Cambrian of the Małopolska Block in SE Poland Based on Data from Two Seismic Wide-Angle Experiments

    NASA Astrophysics Data System (ADS)

    Środa, Piotr

    2017-03-01

    The area of SE Poland represents a complex contact of tectonic units of different consolidation age—from the Precambrian East European Craton, through Palaeozoic West European Platform (including Małopolska Block) to Cenozoic Carpathians and Carpathian Foredeep. In order to investigate the anisotropic properties of the upper crust of the Małopolska Block and their relation to tectonic evolution of the area, two seismic datasets were used: seismic wide-angle off-line recordings from POLCRUST-01 deep seismic reflection profile and recordings from active deep seismic experiment CELEBRATION 2000. During acquisition of deep reflection seismic profile POLCRUST-01 in 2010, a 35-km-long line of 14 recorders (PA-14), oriented perpendicularly to the profile, was deployed to record the refractions from the upper crust (Pg) at wide range of azimuths. These data were used for an analysis of the azimuthal anisotropy of the MB with the modified delay-time inversion method. The results of modelling of the off-line refractions from the MB suggest 6% HTI anisotropy of the Cambrian/Ediacaran basement, with 130º azimuth of the fast velocity axis and mean Vp of 4.9 km/s. To compare this result with previous, independent information about anisotropy at larger depth, a subset of previously modelled data from CELEBRATION 2000 experiment, recorded in the MB area, was also analysed by inversion. The recordings of Pg phase at up to 120 km offsets were analysed using anisotropic delay-time inversion, providing information down to 12 km depth. The CELEBRATION 2000 model shows 9% HTI anisotropy with 126º orientation of the fast axis. Thus, local-scale anisotropy of this part of MB confirms the large-scale anisotropy suggested by previous studies based on data from a broader area and larger depth interval. The azimuthal anisotropy (i.e. HTI symmetry of the medium) is interpreted as a result of strong compressional deformation during the accretion of terranes to the EEC margin, leading to

  7. Results from the latest SN-4 multi-parametric benthic observatory experiment (MARsite EU project) in the Gulf of Izmit, Turkey: oceanographic, chemical and seismic monitoring

    NASA Astrophysics Data System (ADS)

    Embriaco, Davide; Marinaro, Giuditta; Frugoni, Francesco; Giovanetti, Gabriele; Monna, Stephen; Etiope, Giuseppe; Gasperini, Luca; Çağatay, Namık; Favali, Paolo

    2015-04-01

    An autonomous and long-term multiparametric benthic observatory (SN-4) was designed to study gas seepage and seismic energy release along the submerged segment of the North Anatolian Fault (NAF). Episodic gas seepage occurs at the seafloor in the Gulf of Izmit (Sea of Marmara, NW Turkey) along this submerged segment of the NAF, which ruptured during the 1999 Mw7.4 Izmit earthquake. The SN-4 observatory already operated in the Gulf of Izmit at the western end of the 1999 Izmit earthquake rupture for about one-year at 166 m water depth during the 2009-2010 experiment (EGU2014-13412-1, EGU General Assembly 2014). SN-4 was re-deployed in the same site for a new long term mission (September 2013 - April 2014) in the framework of MARsite (New Directions in Seismic Hazard assessment through Focused Earth Observation in the Marmara Supersite, http://marsite.eu/ ) EC project, which aims at evaluating seismic risk and managing of long-term monitoring activities in the Marmara Sea. A main scientific objective of the SN-4 experiment is to investigate the possible correlations between seafloor methane seepage and release of seismic energy. We used the same site of the 2009-2010 campaign to verify both the occurrence of previously observed phenomena and the reliability of results obtained in the previous experiment (Embriaco et al., 2014, doi:10.1093/gji/ggt436). In particular, we are interested in the detection of gas release at the seafloor, in the role played by oceanographic phenomena in this detection, and in the association of gas and seismic energy release. The scientific payload included, among other instruments, a three-component broad-band seismometer, and gas and oceanographic sensors. We present a technical description of the observatory, including the data acquisition and control system, results from the preliminary analysis of this new multidisciplinary data set, and a comparison with the previous experiment.

  8. How astronauts would conduct a seismic experiment on the planet Mars

    NASA Astrophysics Data System (ADS)

    Pletser, V.; Lognonne, P.; Dehant, V.

    During the Summer 2001 Flashline Mars Arctic Research Station (M.A.R.S.) campaign in Devon Island, Nunavut, Canada, the crew of the second rotation conducted a geophysics experiment aiming at assessing the feasibility of an active seismology method to detect subsurface water on Mars. A crew of three deployed a line of 24 sensors. Reflected and refracted signals produced by mini-quakes generated by a sledge hammer were recorded by a seismograph. The experiment was conducted three times, once in a dry run and twice during simulated Extra-Vehicular Activities (EVA) on the edge of the Haughton crater, allowing a three dimensional characterization of the subsurface ground to a depth of several hundred meters. Data were recorded for later detailed processing. A third EVA attempt inside the crater had to be aborted because of the poor weather and terrain conditions. Despite this failed attempt, a large amount of results were collected. Several operational lessons were learned from conducting this experiment under simulated EVA conditions. This paper presents the experiment and the methodology used, reviews the experiment performance and summarizes the results obtained and the operational lessons learned.

  9. High-Resolution Imaging of Tsunamigenic Structures in the Southwest Iberian Margin (Eurasia-Africa Convergence): Implications for Seismic Hazard Assessment

    NASA Astrophysics Data System (ADS)

    Gracia, E.; Danobeitia, J.

    2001-12-01

    The SW Iberian Margin hosts the present-day boundary between the European and African Plates. Convergence is accommodated trough a widespread active deformation zone, characterized by a significant seismic activity, source of the largest earthquakes in Western Europe (e.g. 1969 Horseshoe Earthquake of M8; 1755 Lisbon Earthquake and Tsunami of M8.5). During a recent marine geophysical project (EU-BIGSETS), we identified a 50 km long SE-dipping thrust (Marques de Pombal Fault, MPF), which based on tsunami numerical modelling has been suggested as a plausible source for the 1755 Lisbon earthquake. With the purpose to evaluate the seismic activity of the MPF and other active structures, we plan a detailed, high-resolution survey (HITS). The main objectives of the HITS cruise, to be carried out on board the Spanish RV Hesperides (September-October 2001), are: (a) to confirm the detected active faults, to identify small-scale structures and to determine their geometry using the high-resolution TOBI sidescan sonar, swath-bathymetry, 3.5 kHz sub-bottom profiler and a submarine camera; (b) to calculate the style and rate of slip of the active faults, in order to determine its recurrence interval and assess on the earthquake and tsunami hazard in SW Iberia. To achieve this we plan precise sediment sampling and dating (14C, 210Pb) of the turbiditic units associated with the seismic cycle of the fault; and (c) to investigate the seepage of fluids and heat flow regime along the active faults, which determine the nucleation and propagation of the ruptures. This project is supported by the "European Access to Seafloor Survey Systems (EASSS III)-TOBI sidescan sonar" (HPRI\\-CT\\-1999\\-00047) and Acción Especial MCYT (REN\\-2000\\-2150\\-E).

  10. Improving water use in agriculture. Experiences in the Middle East and North Africa

    SciTech Connect

    Tuijl, W.V.

    1993-08-01

    As water becomes more scarce, many countries are under pressure to conserve water, especially in the agricultural sector. This paper examines strategies that save water in river basins, irrigation projects, and on farms throughout the Middle East and North Africa. Countries elsewhere can use these suggestions in their own water conservation strategies. Improved surface irrigation techniques and micro-irrigation systems are evaluated. These systems use sprinkler, drip/trickle, or micro-spray methods. The author reviews the preliminary work that is needed to install modern irrigation technologies. He describes the role that governments must play to improve the infrastructure and institutions that affect water use. He also provides detailed case studies of efficient irrigation practices in Cyprus, Israel, and Jordan. These case studies describe the conditions that made better irrigation technology a necessity. They look at ways to plan for development, management, and utilization of water in the face of growing demand. Key topics include how to oversee water rights, adopt essential land reforms, and install a graduated system of water pricing and allocation. The study also recommends projects in water conservation and research.

  11. The Society for Women and AIDS in Africa: the experiences of a developing federation.

    PubMed

    Akinsete, I; Harris, M

    1992-01-01

    The Society for Women and AIDS in Africa (SWAA) promotes AIDS prevention (e.g. increasing awareness among African women) and strives to understand how AIDS disrupts their lives and those of their children, families, and communities. It has semiautonomous national branches in 27 countries and has held 4 annual meetings. The Sierra Leone branch has 50 members, both men and women. It has participated in various World AIDS Day activities with 7 youth groups, including preparing posters and performing drama and music. It has conducted a survey of sexual practices which found that many men had multiple partners. the Sierra Leone branch has hosted a 3-day training workshop for women's groups. It has targeted female religious leaders, other clergy, and the Rotary Club. Its chief constraints include lack of funding, civil unrest, lack of electricity, and unreliable postal services. Both the Sierra Leone and Nigeria national branches depend on volunteers. Members of the Nigeria branch represent professional women's groups. SWAA Nigeria has regional branches in 13 states. Some SWAA Nigeria activities have included interventions targeting female prostitutes in 3 states, training of trainers workshops for prostitutes, and educational materials development. It faces several obstacles, including sporadic and unreliable communications systems and insufficient finances. The main obstacle of SWAA at the federation level is lack of core funding, so it has sent a proposal to international and bilateral organizations requesting core funding which would then be used for internal planning and program development. The federation is planning a skills development training program.

  12. The Experiences and Meanings That Shape Heterosexual Fathers' Relationships With Their Gay Sons in South Africa.

    PubMed

    Livingston, Jacques; Fourie, Eduard

    2016-12-01

    Gay men's relationships with their mothers are likely to be more positive than their relationships with their fathers, and fathers are less likely to be told, less likely to be told first, and more likely to react negatively to disclosure than mothers. Drawing on an interpretivist approach, an individual in-depth interview strategy was adopted in the study as a means of gathering data from six Afrikaans-speaking White fathers, between the ages of 53 and 61 years (median: 55.5 years), residing in Gauteng, South Africa. Interviews were audio-recorded and transcribed for later coding and analysis. Through thematic network analysis, eight organizing themes emerged and were explored. For the purpose of this article only three organizing themes are discussed, namely "subliminal awareness prior to coming out," "epistemic rupture of internal systems of ideas/beliefs," and "acceptance as a complex and ongoing dialectical and reconciliatory process." The themes support the view that most parents are neither totally rejecting nor fully accepting of their gay sons. Although the fathers may have attained a level of "loving denial" in the relationships with their gay sons, most continue to struggle with the meaning and expression of same-sex sexuality. Despite these challenges, it is recognized that the fathers are adapting to changing circumstances and are trying to find ways to tolerate, accommodate, and in some ways accept their gay sons.

  13. Sickle-Cell Disease Healthcare Cost in Africa: Experience of the Congo

    PubMed Central

    Ngolet, L. O.; Moyen Engoba, M.; Kocko, Innocent; Elira Dokekias, Alexis; Mombouli, Jean-Vivien; Moyen, Georges Marius

    2016-01-01

    Background. Lack of medical coverage in Africa leads to inappropriate care that has an impact on the mortality rate. In this study, we aimed to evaluate the cost of severe acute sickle-cell related complications in Brazzaville. Methods. A retrospective study was conducted in 2014 in the Paediatric Intensive Care Unit. It concerned 94 homozygote sickle-cell children that developed severe acute sickle-cell disease related complications (average age 69 months). For each patient, we calculated the cost of care complication. Results. The household income was estimated as low (

  14. Experiences of violence and association with decreased drug abstinence among women in Cape Town, South Africa.

    PubMed

    Reed, Elizabeth; Myers, Bronwyn; Novak, Scott P; Browne, Felicia A; Wechsberg, Wendee M

    2015-01-01

    Drug abuse is a contributing factor in women's HIV risk in low-income communities in Cape Town, South Africa. This study assessed whether experiencing violence is associated with reduced drug abstinence among adult women (n = 603) participating in a randomized field trial for an HIV prevention study in Cape Town. In relation to drug abstinence at 12-month follow-up, multivariable regression models were used to assess (1) baseline partner and non-partner victimization, and (2) victimization at 12-month follow-up among participants reporting baseline victimization. Baseline partner (AOR = 0.6; 95 % CI 0.4-0.9) and non-partner victimization (AOR = 0.6; 95 % CI 0.4-0.9) were associated with a reduced likelihood of drug abstinence at follow-up. Among participants who reported victimization at baseline, those no longer reporting victimization at follow-up did not differ significantly in drug abstinence compared with those who reported victimization at follow-up. The study findings highlight the lasting impact of victimization on women's drug use outcomes, persisting regardless of whether violence was no longer reported at follow-up. Overall, the findings support the need for the primary prevention of violence to address the cycle of violence, drug use, and HIV among women in this setting.

  15. Patient Experiences following Acute HIV Infection Diagnosis and Counseling in South Africa

    PubMed Central

    Wolpaw, Benjamin J.; Mathews, Catherine; Mtshizana, Yolisa; Chopra, Mickey; Hardie, Diana; Lurie, Mark N.; De Azevedo, Virginia; Jennings, Karen

    2014-01-01

    Individuals in the acute stage of HIV infection (AHI) have an elevated potential to transmit HIV and play a critical role in the growth of the epidemic. Routine identification and counseling of individuals during AHI could decrease transmission behavior during this key period. However, diagnosis of AHI may present challenges distinct from those experienced through diagnosis of established HIV infection. A study was conducted in a public youth clinic outside of Cape Town, South Africa, to identify and counsel individuals with acute stage HIV infection. In-depth interviews were conducted with patients following diagnosis. After counseling, patients were accepting of the testing regimen used to diagnose AHI. They used the knowledge of having been recently infected to identify the source of their infection, but did not retain or place importance on information regarding the increased ability to transmit HIV during the acute stage. Future interventions directed at the reduction of HIV transmission following diagnosis with AHI will need to find ways of making this information more salient, possibly through more culturally meaningful educational approaches. PMID:25153674

  16. An integrated petrophysical approach to the sub-basalt imaging problem using well logging data to link measurements from cores and seismic experiments

    NASA Astrophysics Data System (ADS)

    Waagstein, R.; Boldreel, L. O.; Andersen, C.

    2003-04-01

    Flood basalt covered basins exist world wide along continental margins and are increasingly coming into the focus of the hydrocarbon industry as more accessible fields are being depleted. However, it has proved difficult in many places to look through the basalt cover by conventional seismic reflection methods. This stresses the need for a better understanding of the acoustic properties of basalt. The Seismic Faroes Basalt Project (SeiFaBa) was established in 2002 as an integrated study of the sub-basalt image problem. It involves 9 scientific institutions and individuals and is funded collectively by all oil companies operating in the Faroes sector (the Sindri group). The planned fieldwork includes core drilling, wire-line logging, multi-azimuth VSP and surface seismic experiments at land and sea. It is mainly centred around Glyvursnes, a relatively flat promontory near Tórshavn that allows optimal layout of seismic lines and integration of core, log and seismic data. We present the initial task of drilling and logging, which was performed in Oct.-Nov. 2002. A 700 m slim borehole was drilled on the shore of Glyvursnes with wire-line coring technique and an old 660 m borehole (Vestmanna-1) 30 km farther northwest partly blocked by calcite fillings was reopened using the same equipment. An extensive wire-line logging program was subsequently run in both holes. These two holes, together with the existing 3.65-km Lopra-1/1A hole in the southernmost island Suduroy, cover all three Faroes basalt formations and a range of lava compositions and morphologies. We show examples of the correlation of lava flow sequences and wire-logging measurements. Detailed analysis of the new logs is being planned together with laboratory studies of the petrography, rock chemistry and petrophysical properties of core samples with the aim of establishing a log stratigraphy and scale core data to seismic scales.

  17. An Irish Adult Learner in Sub-Saharan Africa: A Narrative Account of My Experience of Working with Teacher Educators in Lesotho

    ERIC Educational Resources Information Center

    Griffin, Rosarii

    2009-01-01

    This article presents a narrative account of the author's experience of working with teacher educators in Lesotho, Africa. It describes research projects developed in conjunction with the author's counterparts in Lesotho. Although the research project work is yet in its infancy, the author reflects on insights gained from working as an Irish…

  18. Adapting to climate change and disaster risk reduction through sustainable land management: Experiences in Tajikistan, East Africa, US, Argentina and Mongolia

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The special session will share and discuss experiences from different regions, namely from Tajikistan, East Africa, US, Argentina and Mongolia. Within the Pilot Program for Climate Resilience (PPCR) in Tajikistan 70 SLM technologies and approaches on how to implement SLM were documented with the Wor...

  19. Experiences and support needs of poverty-stricken people living with HIV in the Potchefstroom district in South Africa.

    PubMed

    Feitsma, Anita T; Koen, Magdalena P; Pienaar, Abel J; Minnie, Catharina S

    2007-01-01

    This study was undertaken to address the lack of support for poverty-stricken people living with HIV that was identified in the Potchefstroom district in the North-West Province in South Africa. A qualitative phenomenological design was used to explore the experience, identify the support needs, and formulate guidelines for effective support for poverty-stricken people living with HIV. A total of 25 in-depth interviews guided by two central questions resulted in the following themes: facilitative and impeding experiences of poverty-stricken people living with HIV, basic needs, psychosocial needs, cultural-spiritual needs, and self-actualization needs. The experience of poverty-stricken people living with HIV in the Potchefstroom district is closely related to their support needs. To address these needs holistically and to enhance the quality of life of poverty-stricken people living with HIV, the needs should first be addressed individually. Following that, the collective needs can be addressed by a support system.

  20. Notes on some experiments on the application of subtractive compensation to USGS seismic magnetic tape recording and playback systems

    USGS Publications Warehouse

    Eaton, Jerry P.

    1975-01-01

    The purpose of these experiments is to lay the groundwork for the implementation of subtractive compensation of the USGS seismic network tape playbacks utilizing the Develco model 6203 discriminators at a x1 playback speed. Although the Develco discriminators were designed for this application and a matching Develco compensation discriminator was purchased, effective use of this system for subtractive compensation has been blocked by the inadequate (frequency dependent) matching of the phase of the compensation signal to that of the data signal at the point compensation is carried out in the data discriminators. John Van Schaack has ameliorated the phase mismatch problem by an empirical alteration of the compensation discriminator input bandpass filter. We have selected a set (of eight) Develco discriminators and adjusted their compensation signal input levels to minimize spurious signals (noise) originating from tape speed irregularities. The sensitivity of the data discriminators was adjusted so that deviations of +125 Hz and -125 Hz produced output signals of +2.00 volts and -2.00 volts, respectively. The eight data discriminators are driven by a multiplex signal on a single tape track (subcarriers 680, 1020, 1360, 1700, 2040, 2380, 2720, and 3060 Hz). The Develco-supplied compensation discriminator requires an unmodulated 3125 Hz signal on a separate tape track.

  1. Scaling up delivery of contraceptive implants in sub-Saharan Africa: operational experiences of Marie Stopes International

    PubMed Central

    Duvall, Susan; Thurston, Sarah; Weinberger, Michelle; Nuccio, Olivia; Fuchs-Montgomery, Nomi

    2014-01-01

    Contraceptive implants offer promising opportunities for addressing the high and growing unmet need for modern contraceptives in sub-Saharan Africa. Marie Stopes International (MSI) offers implants as one of many family planning options. Between 2008 and 2012, MSI scaled up voluntary access to implants in 15 sub-Saharan African countries, from 80,041 implants in 2008 to 754,329 implants in 2012. This 9-fold increase amounted to more than 1.7 million implants delivered cumulatively over the 5-year period. High levels of client satisfaction were attained alongside service provision scale up by using existing MSI service delivery channels—mobile outreach, social franchising, and clinics—to implement strategies that broadened access for underserved clients and maintained service quality. Use of adaptive and context-specific service delivery models and attention to key operational components, including sufficient numbers of trained providers, strong supply chains, diverse financing mechanisms, and implant removal services, underpinned our service delivery efforts. Accounting for 70% of the implants delivered by MSI in 2012, mobile outreach services through dedicated MSI provider teams played a central role in scale-up efforts, fueled in part by the provision of free or heavily subsidized services. Social franchising also demonstrated promise for future program growth, along with MSI clinics. Continued high growth in implant provision between 2011 and 2012 in all sub-Saharan African countries indicates the region's capacity for further service delivery expansion. Meeting the expected rising demand for implants and ensuring long-term sustainable access to the method, as part of a comprehensive method mix, will require continued use of appropriate service delivery models, effective operations, and ongoing collaboration between the private, public, and nongovernmental sectors. MSI's experience can be instructive for future efforts to ensure contraceptive access and

  2. Scaling up delivery of contraceptive implants in sub-Saharan Africa: operational experiences of Marie Stopes International.

    PubMed

    Duvall, Susan; Thurston, Sarah; Weinberger, Michelle; Nuccio, Olivia; Fuchs-Montgomery, Nomi

    2014-02-01

    Contraceptive implants offer promising opportunities for addressing the high and growing unmet need for modern contraceptives in sub-Saharan Africa. Marie Stopes International (MSI) offers implants as one of many family planning options. Between 2008 and 2012, MSI scaled up voluntary access to implants in 15 sub-Saharan African countries, from 80,041 implants in 2008 to 754,329 implants in 2012. This 9-fold increase amounted to more than 1.7 million implants delivered cumulatively over the 5-year period. High levels of client satisfaction were attained alongside service provision scale up by using existing MSI service delivery channels-mobile outreach, social franchising, and clinics-to implement strategies that broadened access for underserved clients and maintained service quality. Use of adaptive and context-specific service delivery models and attention to key operational components, including sufficient numbers of trained providers, strong supply chains, diverse financing mechanisms, and implant removal services, underpinned our service delivery efforts. Accounting for 70% of the implants delivered by MSI in 2012, mobile outreach services through dedicated MSI provider teams played a central role in scale-up efforts, fueled in part by the provision of free or heavily subsidized services. Social franchising also demonstrated promise for future program growth, along with MSI clinics. Continued high growth in implant provision between 2011 and 2012 in all sub-Saharan African countries indicates the region's capacity for further service delivery expansion. Meeting the expected rising demand for implants and ensuring long-term sustainable access to the method, as part of a comprehensive method mix, will require continued use of appropriate service delivery models, effective operations, and ongoing collaboration between the private, public, and nongovernmental sectors. MSI's experience can be instructive for future efforts to ensure contraceptive access and choice

  3. Experience and challenges from clinical trials with malaria vaccines in Africa.

    PubMed

    Mwangoka, Grace; Ogutu, Bernhards; Msambichaka, Beverly; Mzee, Tutu; Salim, Nahya; Kafuruki, Shubis; Mpina, Maxmillian; Shekalaghe, Seif; Tanner, Marcel; Abdulla, Salim

    2013-03-04

    Malaria vaccines are considered amongst the most important modalities for potential elimination of malaria disease and transmission. Research and development in this field has been an area of intense effort by many groups over the last few decades. Despite this, there is currently no licensed malaria vaccine. Researchers, clinical trialists and vaccine developers have been working on many approached to make malaria vaccine available.African research institutions have developed and demonstrated a great capacity to undertake clinical trials in accordance to the International Conference on Harmonization-Good Clinical Practice (ICH-GCP) standards in the last decade; particularly in the field of malaria vaccines and anti-malarial drugs. This capacity is a result of networking among African scientists in collaboration with other partners; this has traversed both clinical trials and malaria control programmes as part of the Global Malaria Action Plan (GMAP). GMAP outlined and support global strategies toward the elimination and eradication of malaria in many areas, translating in reduction in public health burden, especially for African children. In the sub-Saharan region the capacity to undertake more clinical trials remains small in comparison to the actual need.However, sustainability of the already developed capacity is essential and crucial for the evaluation of different interventions and diagnostic tools/strategies for other diseases like TB, HIV, neglected tropical diseases and non-communicable diseases. There is urgent need for innovative mechanisms for the sustainability and expansion of the capacity in clinical trials in sub-Saharan Africa as the catalyst for health improvement and maintained.

  4. Discrimination between NTS explosions, earthquakes and the non-proliferation experiment at the Pinedale Seismic Research Facility

    SciTech Connect

    Carr, D.

    1994-09-01

    As the United States moves into an atmosphere of concern about the spread of nuclear weapons to non-nuclear countries, the focus on monitoring nuclear explosions is changing from looking at specific test sites and yields to looking for tests of large and small yields from anywhere in the world. Discrimination of small events then becomes important and regional seismic monitoring the best method to detect and identify suspicious events. At the Pinedale Seismic Research Facility (PSRF) in Wyoming we have the opportunity to try different regional discriminants with nuclear tests from NTS, western US (W-US) earthquakes and the Non-Proliferation Experiment (NPE). Four discriminants that gave the best results in a study by Taylor et al. were tried: m{sub b}:M{sub s}, M{sub b}:M{sub s}{sup h}, log(L{sub g}/P{sub g}) and spectral ratios. The different discriminants were applied to the data (14 NTS explosions, the NPE, one Department of Defense (DOB) explosion and 34 NWS earthquakes) regardless of signal-to-noise. When the NTS explosions and NPE were only compared to four earthquakes located on or near the Test Site, all the discriminants except log(L{sub g}/P{sub g}) worked fairly well at PSRF. When the other WUS earthquakes and DOD explosion are included, only m{sub b}:M{sub s} shows any promise. Because of frequent physical variations in the earth`s crust, regional signals are complex and easily influenced by site and path characteristics. Looking at events from one specific area reduces the effects of the path, which is why three discriminants work well when the data set is restricted to events on or near NTS. The only discriminant not adversely affected from variations in path is m{sub b}:M{sub s}. This is probably because it is believed that source dimension, source time function and/or source mechanism is the cause for the differences between earthquakes and explosions with this discriminant, rather than any path effects.

  5. South Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image of South Africa was acquired on May 14, 2000, by NASA's Moderate-resolution Imaging Spectroradiometer, or MODIS. The image was produced using a combination of the sensor's 250-m and 500-m resolution visible wavelength bands. As part of the opening ceremony to begin the joint U.S.-South Africa SAFARI Field Experiment, NASA presented print copies of this image as GIFts to Dr. Ben Ngubane, Minister of Arts, Science and Technology, and Honorable Advocate Ngoaka Ramathlodi, Premier of the Northern Province, South Africa. The area shown in this image encompasses seven capital cities and a number of the region's distinctive geological features can be seen clearly. Toward the northern (top) central part of the image, the browns and tans comprise the Kalahari Desert of southern Botswana. The Tropic of Capricorn runs right through the heart of the Kalahari and the Botswanan capital city of Gaborone sits on the Limpopo River, southeast of the Kalahari. Along the western coastline of the continent is the country of Namibia, where the Namib Desert is framed against the sea by the Kaokoveld Mountains. The Namibian capital of Windhoek is obscured by clouds. Looking closely in the center of the image, the Orange River can be seen running from east to west, demarcating the boundary between Namibia and South Africa. On the southwestern corner of the continent is the hook-like Cape of Good Hope peninsula and Cape Town, the parliamentary capital of South Africa. Running west to east away from Cape Town are the Great Karroo Mountains. The shadow in this image conveys a sense of the very steep grade of the cliffs along the southern coast of South Africa. Port Elizabeth sits on the southeasternmost point of South Africa, and a large phytoplankton bloom can be seen in the water about 100 miles east of there. Moving northward along the east coast, the Drakensberg Mountains are visible. The two small nations of Lesotho and Swaziland are in this region, completely

  6. Site Characterization of the Source Physics Experiment Phase II Location Using Seismic Reflection Data

    SciTech Connect

    Sexton, Emily; Snelson, Catherine M; Chipman, Veraun D; Emer, Dudley; White, Bob; Emmit, Ryan; Wright, Al; Drellack, Sigmund; Huckins-Gang, Heather; Mercadante, Jennifer; Floyd, Michael; McGowin, Chris; Cothrun, Chris; Bonal, Nedra

    2013-12-05

    An objective of the Source Physics Experiment (SPE) is to identify low-yield nuclear explosions from a regional distance. Low-yield nuclear explosions can often be difficult to discriminate among the clutter of natural and man-made explosive events (e.g., earthquakes and mine blasts). The SPE is broken into three phases. Phase I has provided the first of the physics-based data to test the empirical models that have been used to discriminate nuclear events. The Phase I series of tests were placed within a highly fractured granite body. The evolution of the project has led to development of Phase II, to be placed within the opposite end member of geology, an alluvium environment, thereby increasing the database of waveforms to build upon in the discrimination models. Both the granite and alluvium sites have hosted nearby nuclear tests, which provide comparisons for the chemical test data. Phase III of the SPE is yet to be determined.

  7. Children’s experiences of corporal punishment: A qualitative study in an urban township of South Africa

    PubMed Central

    Breen, Alison; Daniels, Karen; Tomlinson, Mark

    2015-01-01

    Exposure to violence is a serious mental and public health issue. In particular, children exposed to violence are at risk for poor developmental outcomes and physical and mental health problems. One area that has been shown to increase the risk for poor outcomes is the use of corporal punishment as a discipline method. While researchers are starting to ask children directly abouttheir experiences of violence, there is limited research with children about their perspectives on physical punishment, particularly in low-and middle-income countries (LMIC). This paper begins to address this gap by reporting on the spontaneous data that emerged during 24 qualitative interviews that were conducted with children, aged 8–12 in South Africa. The themes that emerged indicated that corporal punishment is an everyday experience, that it has negative emotional and behavioral consequences, and that it plays a role in how children resolve interpersonal conflicts. The study highlights the challenges for violence prevention interventions in under-resourced contexts. PMID:26094159

  8. Planning the improvement of a seismic network for monitoring active volcanic areas: the experience on Mt. Etna

    NASA Astrophysics Data System (ADS)

    D'Alessandro, A.; Scarfì, L.; Scaltrito, A.; Di Prima, S.; Rapisarda, S.

    2013-10-01

    Seismology and geodesy are generally seen as the most reliable diagnostic tools for monitoring highly active or erupting volcanoes, like Mt. Etna. From the early 1980's, seismic activity was monitored at Mt. Etna by a permanent seismic network, progressively improved in the following years. This network has been considerably enhanced since 2005 by 24-bit digital stations equipped with broad-band (40 s) sensors. Today, thanks to a configuration of 33 broad-band and 12 short-period stations, we have a good coverage of the volcanic area as well as a high quality of the collected data. In the framework of the VULCAMED project a workgroup of Istituto Nazionale di Geofisica e Vulcanologia has taken on the task of developing the seismic monitoring system, through the installation of other seismic stations. The choice of optimal sites must be clearly made through a careful analysis of the geometry of the existing seismic network. In this paper, we applied the Seismic Network Evaluation through Simulation in order to evaluate the performance of the Etna Seismic Network before and after the addition of the stations in the candidate sites. The main advantage of the adopted method is that we can evaluate the improvement of the network before the actual installation of the stations. Our analysis has permitted to identify some critical issues of the current permanent seismic network related to the lack of stations in the southern sector of the volcano, which is nevertheless affected by a number of seismogenic structures. We have showed that the addition of stations at the candidate sites would greatly extend the coverage of the network to the south by significantly reducing the errors in the hypocenter parameters estimation.

  9. Experiences of Disabled Students in South Africa: Extending the Thinking behind Disability Support

    ERIC Educational Resources Information Center

    Matshedisho, K. R.

    2010-01-01

    This article argues that even though the experiences of disabled students have programmatic implications, their needs should not be isolated from other students'. Instead they should be understood as part of the student life cycle within the pluralistic paradigm of education. In demonstrating the argument this article will: (a) outline some of the…

  10. NSF RET in Southern Africa: community and research experiences in soil science

    NASA Astrophysics Data System (ADS)

    Mladenov, N.; Pollard, A.; Wellbeloved-Stone, R.; Riffel, H.; Chavarro, D.; D'Odorico, P.

    2010-12-01

    Collaborative research on belowground carbon storage in the Kalahari Desert has provided opportunities for international research experience for US middle and high school teachers, funded by the National Science Foundation Research Experience for Teachers (RET) Program. This presentation will highlight the field research experiences, international high school visit, relationships fostered with Botswana high school teachers, and new soil science curricula developed by three US environmental science teachers. New lesson plans and activities on carbon sequestration, fine and coarse root mapping, and soil organic carbon cycling and other learning tools have been incorporated into the existing Underground Safari webpage (instaar.colorado.edu/undergroundsafari) (Figure 1). An interactive blog, undergroundsafari.edublogs.org, has been developed to allow dynamic discourse between students, teachers and researchers on this project. Lessons learned from classroom trials of curriculum and use of other RET experience-motivated activities in the classroom will be discussed. Figure 1. Screen capture of the "Videos" page from the Underground Safari website for NSF DEB project, "Collaborative Research: Distribution and dynamics of belowground carbon in savannas."

  11. Kick & cook experiments on natural dunite: simulating episodic creep below the seismogenic zone during the seismic cycle

    NASA Astrophysics Data System (ADS)

    Druiventak, A.; Trepmann, C.; Matysiak, A. K.; Renner, J.

    2010-12-01

    The microfabric development in dunite is analyzed in deformation and annealing experiments, which are designed to simulate the natural stress history in the upper mantle of the oceanic lithosphere just below the seismogenic zone during the seismic cycle. The samples are deformed in a servohydraulically-controlled solid medium deformation apparatus at 600°C, a constant strain rate of 10-4s-1 and confining pressure of 1.0 GPa and 2.0 GPa (“kick” experiment). In some experiments deformation is followed by annealing for 15 h to 70 h at zero nominal differential stress, temperatures of 700°C to 1000°C and 2.0 GPa confining pressure (“kick & cook” experiment). We use coarse-grained dunite from the Almklovdalen peridotite complex (Western Norway) as starting material. The dunite comprises ca. 90% olivine, <10% orthopyroxene and small amounts of clinopyroxene, spinel and chlorite. The “kick” experiments yield maximum differential stresses of ca. 1.2 GPa to 1.6 GPa. The resulting microfabrics are analyzed by optical and electron microscopic techniques. Shear zones and microcracks developed in the dunites during deformation. The microfabric indicates brittle and crystal-plastic deformation of olivine. Intragranular microfaults, which can be crystallographically controlled, and deformation lamellae parallel to (100) occur in deformed olivine crystals. In TEM, the optical visible deformation lamellae are represented by a high density of straight dislocations aligned parallel to [001], indicating that they are [001] screw dislocations. Thus, the deformation lamellae in (100) imply an operating glide system of (100)[001]. Cataclastically deformed olivine is characterized in TEM by domains with a high dislocation density, which are bound by poorly-ordered dislocation walls. After annealing at 1000°C, the microfabric is characterized by very fine-grained (a few µm in diameter) recrystallized olivine grains arranged along microfaults and surrounding olivine

  12. Seafloor surface processes and subsurface paleo-channel unconformities mapped using multi-channel seismic and multi-beam sonar data from the Galicia 3D seismic experiment.

    NASA Astrophysics Data System (ADS)

    Gibson, J. C.; Shillington, D. J.; Sawyer, D. S.; Jordan, B.; Morgan, J. K.; Ranero, C.; Reston, T. J.

    2015-12-01

    In this study we use geophysical methods, stratigraphic relationships, and coring/drilling leg results to assess possible controls on deep-sea channel formation in order to further constrain paleo-channel (PC) and associated unconformity timing/source processes. A series of cut and fill PC are mapped in 3D multi-channel seismic (MCS) data and compared with multi-beam (MB) sonar bathymetry/backscatter data collected during the Galicia 3D survey with the R/V Marcus G. Langseth (2013). The MCS data were collected using four 6 km streamers spaced at 200 m resulting in 25 m x 25 m common mid-point bins within the ~67 km x 20 km 3D volume. The MB data were collected at an average depth of ~4900 m with a constrained swath width of 4.5 km resulting in 11.25x overlap while enabling 25-m bathymetry and 10-m backscatter grids. The PC lie below the mouth of a submarine canyon at the edge of the Galicia abyssal plain and cut pre/syn-rift sediments; they are bound by a rift block to the north and paleo-levees to the south (maximum height of ~180m). From drilling results, the most recent PC is late Miocene in age. In this study, four PC are traced into the basin as unconformities. Several of the PC/unconformities are tentatively correlated with previously interpreted Pyrenean orogeny/compressional Miocene/Oligocene tectonic events. However, one PC/unconformity within this interval has not been previously interpreted. In order test the hypothesis that the unconformities are the result of a significant change in base level indicated by a low shale/sand (SS) ratio, we use seismic surface attributes to calculate the SS ratio and trace the horizontal extent of the unconformities. Additionally, the MB/MCS seafloor morphology reveals sedimentary waves outboard of the canyon mouth. We use backscatter data to compare the extent of recent processes (e.g., Pleistocene glaciation/de-glaciation) with the unconformities by mapping the surface/shallow subsurface SS ratio (volume scattering).

  13. The GLIMPCE seismic experiment: Onshore refraction and wide-angle reflection observations from a fan line over the Lake Superior Midcontinent Rift System

    NASA Astrophysics Data System (ADS)

    Epili, Duryodhan; Mereu, Robert F.

    The 1986 GLIMPCE experiment (Great Lakes International Multidisciplinary Program for Crustal Evolution) was a combined on-ship seismic reflection and onshore seismic refraction experiment designed to determine the structure of the crust beneath the Great Lakes. The main tectonic targets of interest were the Midcontinent Rift System, the Grenville Front, the Penokean and Huronian Fold Belts and the Michipicoten Greenstone Belt. The source of the seismic energy came from a large air gun array fired at closely spaced intervals (50-350 m) over several long lines (150-350 km) crossing the lakes. Major participants of this experiment were the Geological Survey of Canada, the United States Geological Survey and a number of universities and research institutes on both sides of the border. The University of Western Ontario (UWO) collected data at five separate land stations using portable seismic refraction instruments. In this paper we present the results of a fan profile which was recorded from a UWO station on Michipicoten Island for the N-S line A which crossed the axis of the Lake Superior Synclinal Basin. The azimuth and distance ranges for this profile were 237 to 321 degrees and 120 to 170 km respectively. Detailed observations of the record sections show that p. is not a simple arrival but forms a rather complex pattern of irregular multiple arrivals. The wide-angle PmP reflection signals from the Moho are strong and well obilerved only for the shots fired near the ends of the line. The signals from the middle of the profile arrive relatively late and form very weak complex wave trains. These results indicate that the Moho in that area is probably greatly disrupted and gives added support to the rift theory for the structure under the lake. The observations also support the results of earlier crustal studies of Lake Superior which showed that the crust under the eastern part of the lake was exceedingly thick.

  14. Caregivers’ Experiences of Pathways to Care for Seriously Ill Children in Cape Town, South Africa: A Qualitative Investigation

    PubMed Central

    Jones, Caroline H. D.; Ward, Alison; Hodkinson, Peter W.; Reid, Stephen J.; Wallis, Lee A.; Harrison, Sian; Argent, Andrew C.

    2016-01-01

    Purpose Understanding caregivers’ experiences of care can identify barriers to timely and good quality care, and support the improvement of services. We aimed to explore caregivers’ experiences and perceptions of pathways to care, from first access through various levels of health service, for seriously ill and injured children in Cape Town, South Africa, in order to identify areas for improvement. Methods Semi-structured, qualitative interviews were conducted with primary caregivers of children who were admitted to paediatric intensive care or died in the health system prior to intensive care admission. Interviews explored caregivers’ experiences from when their child first became ill, through each level of health care to paediatric intensive care or death. A maximum variation sample of transcripts was purposively sampled from a larger cohort study based on demographic characteristics, child diagnosis, and outcome at 30 days; and analysed using the method of constant comparison. Results Of the 282 caregivers who were interviewed in the larger cohort study, 45 interviews were included in this qualitative analysis. Some caregivers employed ‘tactics’ to gain quicker access to care, including bypassing lower levels of care, and negotiating or demanding to see a healthcare professional ahead of other patients. It was sometimes unclear how to access emergency care within facilities; and non-medical personnel informally judged illness severity and helped or hindered quicker access. Caregivers commonly misconceived ambulances to be slow to arrive, and were concerned when ambulance transfers were seemingly not prioritised by illness severity. Communication was often good, but some caregivers experienced language difficulties and/or criticism. Conclusions Interventions to improve child health care could be based on: reorganising the reception of seriously ill children and making the emergency route within healthcare facilities clear; promoting caregivers’ use of

  15. Emergency nursing in South Africa.

    PubMed

    Brysiewicz, Petra; Bruce, Judy

    2008-04-01

    The role of the emergency nurse in South Africa is a challenging one due to a variety of reasons. This article describes the healthcare system of South Africa with particular attention to the emergency medical system as well as the reason why most emergency clients present to the emergency departments. The actual experience of working as an emergency nurse in South Africa is highlighted.

  16. 1978 Yellowstone-eastern Snake River Plain seismic profiling experiment: Data and upper crustal structure of the Yellowstone region

    SciTech Connect

    Schilly, M.M.; Smith, R.B.; Braile, L.W.; Ansorge, J.

    1982-04-10

    Eleven in-line refraction profiles, recorded to distances of 300 km, and one azimuthal fan plot were constructed from data recorded with a 150-station array in the Yellowstone National Park area during the 1978 Yellowstone-Snake River Plain seismic experiment. Interpretations of the data suggest that the crustal P wave velocity model for the Yellowstone region is characterized by (1) an averaged 10-km-thick upper crustal layer, V/sub p/ = 6.0 km/s, (2) an average crustal velocity of 6.3 km/s, and (3) a total crustal thickness of 44 km. Velocity models are presented for profiles that emphasize the upper crust and show (1) a decrease in the depth to the top of the upper crustal crystalline basement from 5 km in southwestern Yellowstone near Island Park to 1 km at the northeast side of the Yellowstone Plateau that is interpreted as a progressive thinning of the silicic surface volcanic layer to the northeast and (2) evidence for a large lateral inhomogeneity interpreted to be a low-velocity body, with a decrease of at least 10% in P wave velocity, located beneath the northeast corner of the Yellowstone Plateau. The low-velocity zone coincides with a local -30-mgal residual gravity anomaly and is located beneath part of the Sour Creek resurgent dome and part of the Hot Springs Basin, the largest hydrothermal system in Yellowstone. The low-velocity body has a maximum depth to the top of 3 km and a minimum depth to the bottom of 9 km and may represent a zone of partial melt. In comparison to the thermally undisturbed upper crust of the surrounding Rocky Mountains the upper crust of the northeastern Yellowstone plateau appears laterally inhomogeneous in velocity and layer thickness, suggesting effects of thermal and magma intrusion, whereas the lower crust appears relatively homogeneous.

  17. The Seismotectonic Model of Southern Africa

    NASA Astrophysics Data System (ADS)

    Midzi, Vunganai; Mulabisana, Thifelimbulu; Manzunzu, Brassnavy

    2013-04-01

    Presented in this report is a summary of the major structures and seismotectonic zones in Southern Africa (Botswana, Lesotho, Namibia, South Africa and Swaziland), which includes available information on fault plane solutions and stress data. Reports published by several experts contributed much to the prepared zones. The work was prepared as part of the requirements for the SIDA/IGCP Project 601 titled "Seismotectonics and Seismic Hazards in Africa" as well as part of the seismic source characterisation of the GEM-Africa Seismic hazard study. The seismic data used are part of the earthquake catalogue being prepared for the GEM-Africa project, which includes historical and instrumental records as collected from various agencies. Seventeen seismic zones/sources were identified and demarcated using all the available information. Two of the identiied sources are faults with reliable evidence of their activity. Though more faults have been identified in unpublished material as being active, more work is being carried out to obtain information that can be used to characterise them before they are included in the seismotectonic model. Explanations for the selected boundaries of the zones are also given in the report. It should be noted that this information is the first draft of the seismic source zones of the region. Futher interpreation of the data is envisaged which might result in more than one version of the zones.

  18. Monitoring of glacial seismic events from Greenland at regional distances: experience from the POLENET/LAPNET experiment during the IPY 2007-2009

    NASA Astrophysics Data System (ADS)

    Kozlovskaya, E.; Pedersen, H.; Plomerova, J.; Achauer, U.; Kissling, E. H.; Sanina, I.; Jämsen, T.; Silvennoinen, H.; Pequegnat, C.; Hurskainen, R.; Hausmann, H.; Jedlicka, P.; Aleshine, I.; Bourova, E.; Bodvarsson, R.; Brueckl, E. P.; Eken, T.; Heikkinen, P. J.; Houseman, G. A.; Johnsen, H.; Kari, K.; Munzarova, H.; Roberts, R.; Ruzek, B.; Hosein Shomali, Z.; Schweitzer, J.; Shaumyan, A.; Vecsey, L.; Volosov, S.

    2010-12-01

    Monitoring of glacial earthquakes from Greenland was one of the major targets of the POLENET/LAPNET passive seismic experiment in northern Fennoscandia (northern parts of Finland, Sweden, Norway and Russian Karelia) during the IPY 2007-2009. The POLENET/LAPNET array, with the average spacing between stations of 70 km, was designed to solve specific tasks of polar seismology. The collected POLENET/LAPNET dataset includes high-frequency continuous data (sampling rate from 50 to 100 sps) of 37 temporary stations, which were in operation during the time frame from 01.05.2008 to 31.09.2009, and of 21 stations of selected permanent networks in Fennoscandia. The first results of the experiment have shown that the POLENET/LAPNET array, located at regional distances from Greenland, recorded more such events than it has been recorded by the Global Seismographic Network during the same observation period. The waveforms of events recorded by the array differ from both long-period waveforms of glacial earthquakes recorded at teleseismic distances and from short-period glacial rumblings recorded at local distances. Recordings of glacial earthquakes obtained by the array contain the long-period energy only. In many cases the events were recorded in groups within the time interval of up to 1 hour. Generally, the waveforms of events within the same group are different and the events not always originate from the same location. For some of the events it was possible to recognize not only dispersed long-period surface wave, but also the first arrival of a long-period P-wave. This suggests that source duration of these events was long. Diversity of the waveforms of glacial events recorded by the POLENET/LAPNET array can be considered as evidence for diversity of source mechanisms of these events.

  19. Experiences of families caring for an HIV-infected child in KwaZulu-Natal, South Africa: An exploratory study

    PubMed Central

    Demmer, Craig

    2011-01-01

    In South Africa, 2.5% of children are living with HIV. KwaZulu-Natal is the province most affected by the epidemic and has the highest number of pregnant women living with HIV. This study reports on a qualitative study to assess the views and experiences of those involved in caring for a child with HIV/AIDS. In-depth interviews were conducted in KwaZulu-Natal with 13 women who were the primary caregivers of a child with HIV/AIDS and 12 key informants who worked with children and families living with HIV/AIDS. The combination of widespread poverty and HIV-related stigma was perceived to compromise the health of a child with HIV/AIDS. Caregivers’ primary focus was on economic survival and there was little income to meet basic human needs including the child’s. Stigmatizing attitudes caused some caregivers to keep their child’s sickness a secret and symptoms were sometimes ignored or treatment delayed. Little material and emotional support was available to caregivers who were overwhelmed by multiple stresses in this context. Support group interventions for caregivers of children with HIV/AIDS can be a useful resource provided that they jointly address the economic and psychological needs of caregivers. A stronger commitment at the national level to reduce poverty and HIV-related stigma is needed to strengthen the capacity of families who are caring for children with HIV/AIDS. PMID:21400305

  20. Passive seismic experiment and receiver functions analysis to determine crustal structure at the contact of the northern Dinarides and southwestern Pannonian Basin

    NASA Astrophysics Data System (ADS)

    Šumanovac, Franjo; Hegedűs, Endre; Orešković, Jasna; Kolar, Saša; Kovács, Attila C.; Dudjak, Darko; Kovács, István J.

    2016-06-01

    Passive seismic experiment was carried out at the SW contact of the Dinarides and Pannonian basin to determine the crustal structure and velocity discontinuities. The aim of the experiment was to define the relationship between the Adriatic microplate and the Pannonian segment as a part of the European plate. Most of the temporary seismic stations were deployed in Croatia along the Alp07 profile-a part of the active-source ALP 2002 project. About 300-km-long profile stretches from Istra peninsula to the Drava river, in a WSW-ESE direction. Teleseismic events recorded on 13 temporary seismic stations along the profile were analysed by P-receiver function method. Two types of characteristic receiver functions (RF) have been identified, belonging to Dinaridic and Pannonian crusts as defined on the Alp07 profile, while in transitional zone there are both types. Three major crustal discontinuities can be identified for the Dinaridic type: sedimentary basement, intracrustal discontinuity and Mohorovičić discontinuity, whereas the Pannonian type revealed only two discontinuities. The intracrustal discontinuity was not observed in the Pannonian type, thus pointing to a single-layered crust in the Pannonian basin. Two interpretation methods were applied: forward modelling of the receiver functions and H-κ stacking method, and the results were compared with the active-source seismic data at deep refraction profile Alp07. The receiver function modelling has given reliable results of the Moho depths that are in accordance with the seismic refraction results at the end of the Alp07 profile, that is in the area of Pannonian crust characterized by simple crustal structure and low seismic velocities (Vp between 5.9 and 6.2 km s-1). In the Dinarides and its peripheral parts, receiver function modelling regularly gives greater Moho depths, up to +15 per cent, due to more complex crustal structure. The depths of the Moho calculated by the H-κ stacking method vary within wide

  1. Cardiac surgery in Africa: a thirty-five year experience on open heart surgery in Cote d’Ivoire

    PubMed Central

    Meneas, Christophe; Diby, Florent; Diomande, Manga; Adoubi, Anicet; Tanauh, Yves

    2016-01-01

    Background Few centers for open heart surgery (OHS) are in Sub-Saharan Africa. Lack of OHS results is also noted. By reporting our African experience on OHS, the aim of this study was to fill the gap. Methods It is a retrospective study on 2,612 patients who were subject to an OHS between 1978 and 2013. Data were collected from demographical, clinical, investigative studies, surgical and outcomes parameters. Results There were 1,475 cases of rheumatic heart diseases (RHD), 126 endomyocardial fibrosis (EMF), 741 congenital heart diseases (CHDs) and 270 various affections. Related to rheumatic valvular surgery we enumerated 1,175 monovalvular (mitral n=778, aortic n=336, tricuspid n=61); 280 bivalvular (mitral + aortic n=150, mitral + tricuspid n=130) and 20 trivalvular. For RHD, average age was 26±10.1 years (4–69 years) and 60% of our patients presented a functional class III or IV according to New York Heart Association (NYHA) classification. A total of 1,481 valvular replacements (bioprostheses n=489, mechanical prostheses n=992) and 445 valvular repair were carried out with a global and late mortality surgery respectively at 7% and 8%. One hundred and twenty-six [126] cases of EMF with right sided form 39, left sided form 40, and bilateral form 47 were colligated. Average age was 12±0.6 years (2–15 years). All patients with EMF underwent surgery; an endocardectomy in all patients combined with valvular reconstruction (n=36) or valvular replacement (n=90) was carried out with a hospital mortality at 16% (n=20). Concerning CHD, the most frequent were ventricular septal defect (VSD) (n=240), atrial septal defect (ASD) (n=200), partial atrio-ventricular sepal defect (n=30) and tetralogy of Fallot (T4F) (n=220), a total correction was performed for those CHD with an early mortality at 6.4% (n=44). Conclusions OHS in Cote d’Ivoire was successfully performed in most of our patients, the spectrum of acquired valvular heart diseases and CHDs in our country is

  2. Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), Southern California; Part II, Data tables and plots

    USGS Publications Warehouse

    Murphy, Janice M.; Fuis, Gary S.; Okaya, D.A.; Thygesen, Kristina; Baher, Shirley A.; Rybert, Trond; Kaip, Galen; Fort, Michael D.; Asudeh, Isa; Sell, Russell

    2002-01-01

    The Los Angeles Region Seismic Experiment (LARSE), a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC), was conducted to produce seismic images of the subsurface in the Los Angeles region. Primary targets were major fault systems and sedimentary basins; the goal of the project was to address the earthquake hazard posed by these geologic features. The first phase of data collection (LARSE 1) was completed in 1994; the second phase (LARSE 2) was completed in 1999. A description of the 1999 survey and an overview of both phase I and II is given in Fuis and others (2001). In this report, we present the technical details for the explosion data collected in 1999.

  3. The derivation of an anisotropic velocity model from combined surface and borehole seismic experiments at the COSC-1 borehole, central Sweden

    NASA Astrophysics Data System (ADS)

    Simon, Helge; Krauß, Felix; Hedin, Peter; Buske, Stefan; Giese, Rüdiger; Juhlin, Christopher

    2016-04-01

    The Scandinavian Caledonides provide a well preserved example of a Paleozoic continent-continent collision, where the surface geology in combination with geophysical data provide control of the geometry of parts of the Caledonian structure. The project COSC (Collisional Orogeny in the Scandinavian Caledonides) investigates the structure and physical conditions of the orogen units and the underlying basement with two approximately 2.5 km deep fully cored boreholes in western Jämtland, central Sweden. In 2014 the COSC-1 borehole was successfully drilled through the Seve Nappe Complex. This unit, mainly consisting of gneisses, belongs to the so-called Middle Allochthons and has been ductilely deformed and transported during collisional orogeny. A major seismic survey was conducted in and around the COSC-1 borehole which comprised both seismic reflection and transmission experiments. Combined with core analysis and downhole logging, the survey will allow extrapolation of the structures away from the borehole. The survey consisted of three parts: 1) a high-resolution zero-offset Vertical Seismic Profile (VSP), 2) a multi-azimuthal walkaway VSP in combination with three long offset surface receiver lines, and 3) a limited 3D seismic survey. Data from the multi-azimuthal walkaway VSP experiment and the long offset surface lines were used to derive a detailed velocity model around the borehole from the inversion of first arrival traveltimes. The comparison of velocities from these tomography results with a velocity function calculated from the zero-offset VSP revealed clear differences in velocities for mainly horizontally and vertically traveling waves. Therefore, an anisotropic VTI model was constructed, using the P-wave velocity function from zero-offset VSP and the Thomson parameters ɛ and δ. The latter were partly derived from ultrasonic lab measurements on COSC-1 core samples. Traveltimes were calculated with an anisotropic eikonal solver and serve as the basis

  4. Research-policy partnerships - experiences of the Mental Health and Poverty Project in Ghana, South Africa, Uganda and Zambia

    PubMed Central

    2012-01-01

    Background Partnerships are increasingly common in conducting research. However, there is little published evidence about processes in research-policy partnerships in different contexts. This paper contributes to filling this gap by analysing experiences of research-policy partnerships between Ministries of Health and research organisations for the implementation of the Mental Health and Poverty Project in Ghana, South Africa, Uganda and Zambia. Methods A conceptual framework for understanding and assessing research-policy partnerships was developed and guided this study. The data collection methods for this qualitative study included semi-structured interviews with Ministry of Health Partners (MOHPs) and Research Partners (RPs) in each country. Results The term partnership was perceived by the partners as a collaboration involving mutually-agreed goals and objectives. The principles of trust, openness, equality and mutual respect were identified as constituting the core of partnerships. The MOHPs and RPs had clearly defined roles, with the MOHPs largely providing political support and RPs leading the research agenda. Different influences affected partnerships. At the individual level, personal relationships and ability to compromise within partnerships were seen as important. At the organisational level, the main influences included the degree of formalisation of roles and responsibilities and the internal structures and procedures affecting decision-making. At the contextual level, political environment and the degree of health system decentralisation affected partnerships. Conclusions Several lessons can be learned from these experiences. Taking account of influences on the partnership at individual, organisation and contextual/system levels can increase its effectiveness. A common understanding of mutually-agreed goals and objectives of the partnership is essential. It is important to give attention to the processes of initiating and maintaining partnerships

  5. Does identity shape leadership and management practice? Experiences of PHC facility managers in Cape Town, South Africa.

    PubMed

    Daire, Judith; Gilson, Lucy

    2014-09-01

    In South Africa, as elsewhere, Primary Health Care (PHC) facilities are managed by professional nurses. Little is known about the dimensions and challenges of their job, or what influences their managerial practice. Drawing on leadership and organizational theory, this study explored what the job of being a PHC manager entails, and what factors influence their managerial practice. We specifically considered whether the appointment of professional nurses as facility managers leads to an identity transition, from nurse to manager. The overall intention was to generate ideas about how to support leadership development among PHC facility managers. Adopting case study methodology, the primary researcher facilitated in-depth discussions (about their personal history and managerial experiences) with eight participating facility managers from one geographical area. Other data were collected through in-depth interviews with key informants, document review and researcher field notes/journaling. Analysis involved data triangulation, respondent and peer review and cross-case analysis. The experiences show that the PHC facility manager's job is dominated by a range of tasks and procedures focused on clinical service management, but is expected to encompass action to address the population and public health needs of the surrounding community. Managing with and through others, and in a complex system, requiring self-management, are critical aspects of the job. A range of personal, professional and contextual factors influence managerial practice, including professional identity. The current largely facility-focused management practice reflects the strong nursing identity of managers and broader organizational influences. However, three of the eight managers appear to self-identify an emerging leadership identity and demonstrate related managerial practices. Nonetheless, there is currently limited support for an identity transition towards leadership in this context. Better

  6. Microbicide trials for preventing HIV/AIDS in South Africa: phase II trial partricipants' experiences and psychological needs.

    PubMed

    Pistorius, A G; van de Wijgert, J H H M; Sebola, M; Friedland, B; Nagel, E; Bokaba, C; Hoosen, A A

    2004-08-01

    The Microbicide Division of the Department of Medical Microbiology at MEDUNSA, South Africa, recently completed a phase II expanded safety trial of the candidate microbicide Carraguard. A microbicide is a vaginal product that women might use, if proven safe and effective, to protect themselves from HIV and possibly other sexually transmitted infections (STIs). The study participants were from Ga-Rankuwa and its neighbouring areas, an historically disadvantaged residential township near Pretoria. We conducted six focus group discussions with phase II trial participants to evaluate their experiences with trial participation and their psychological needs. Participants spontaneously talked about their experiences with the study gel and speculum examinations. They felt that they had received high quality medical care. They indicated that their personal hygiene and knowledge of the female reproductive system, HIV and other STIs had improved, which helped their familie and empowered them as women. Participants valued being able to discuss their anxiety about HIV/AIDS wit study staff. They felt that the study provided them with a supportive environment in which their personal problems (not necessarily restricted to HIV/AIDS) could be addressed. Some recommended that the study staf improve their professionalism and punctuality. They suggested the formation of participant support groups, an expressed a preference to remain involved in the trial. Some participants appeared to have become dependent o services provided during the trial. We have taken the results of these focus group discussions into account during planning for a phase III efficacy trial of Carraguard to be conducted in the same and other similar communities.

  7. Perceptions and experiences of allopathic health practitioners on collaboration with traditional health practitioners in post-apartheid South Africa

    PubMed Central

    Hendricks, Stephen J.; Mulaudzi, Mavis F.

    2016-01-01

    Background The indigenous health system was perceived to be a threat to the allopathic health system. It was associated with ‘witchcraft’, and actively discouraged, and repressed through prohibition laws. The introduction of the Traditional Health Practitioners Act No 22 of 2007 brought hope that those centuries of disrespect for traditional health systems would change. The study examined the perceptions and experiences of allopathic health practitioners on collaboration with traditional health practitioners in post-apartheid South Africa. Methods Qualitative descriptive research methodology was used to collect data from allopathic health practitioners employed by Limpopo’s Department of Health. In-depth focus group discussions and meetings were conducted between January and August 2014. Perceptions and experiences of working with traditional health practitioners were explored. Ethical clearance was obtained from the University of Pretoria and approval from the Department’s Research Committee. Results Dominant views were that the two health systems were not compatible with respect to the science involved and the source of knowledge. Overall, quality of health care will be compromised if traditional health practitioners are allowed to work in public health facilities. Conclusion Allopathic health practitioners do not appear ready to work with traditional health practitioners, citing challenges of quality of health care, differences regarding concept of sciences and source of knowledge; and lack of policy on collaboration. Lack of exposure to traditional medicine seems to impede opportunities to accept and work with traditional healers. Exposure and training at undergraduate level regarding the traditional health system is recommended. Policy guidelines on collaborations are urgently required. PMID:27380856

  8. Does identity shape leadership and management practice? Experiences of PHC facility managers in Cape Town, South Africa

    PubMed Central

    Daire, Judith; Gilson, Lucy

    2014-01-01

    In South Africa, as elsewhere, Primary Health Care (PHC) facilities are managed by professional nurses. Little is known about the dimensions and challenges of their job, or what influences their managerial practice. Drawing on leadership and organizational theory, this study explored what the job of being a PHC manager entails, and what factors influence their managerial practice. We specifically considered whether the appointment of professional nurses as facility managers leads to an identity transition, from nurse to manager. The overall intention was to generate ideas about how to support leadership development among PHC facility managers. Adopting case study methodology, the primary researcher facilitated in-depth discussions (about their personal history and managerial experiences) with eight participating facility managers from one geographical area. Other data were collected through in-depth interviews with key informants, document review and researcher field notes/journaling. Analysis involved data triangulation, respondent and peer review and cross-case analysis. The experiences show that the PHC facility manager’s job is dominated by a range of tasks and procedures focused on clinical service management, but is expected to encompass action to address the population and public health needs of the surrounding community. Managing with and through others, and in a complex system, requiring self-management, are critical aspects of the job. A range of personal, professional and contextual factors influence managerial practice, including professional identity. The current largely facility-focused management practice reflects the strong nursing identity of managers and broader organizational influences. However, three of the eight managers appear to self-identify an emerging leadership identity and demonstrate related managerial practices. Nonetheless, there is currently limited support for an identity transition towards leadership in this context. Better

  9. Accessing Sexual and Reproductive Health Information and Services: A Mixed Methods Study of Young Women's Needs and Experiences in Soweto, South Africa.

    PubMed

    Lince-Deroche, Naomi; Hargey, Adila; Holt, Kelsey; Shochet, Tara

    2015-03-01

    Young women and girls in South Africa are at high risk of unintended pregnancy and HIV. Previous studies have reported barriers to contraceptive and other sexual and reproductive health (SRH) services among young women in this context. We aimed to assess young women's SRH knowledge and experiences and to determine how they get SRH information and services in Soweto, South Africa using quantitative and qualitative methods. Young women, aged 18-24, recruited from primary health clinics and a shopping mall, reported that they have access to SRH information and know where to obtain services. However there are challenges to accessing and utilizing information and services including providers' unsupportive attitudes, uneven power dynamics in relationships and communication issues with parents and community members. There is a need to assist young women in understanding the significance of SRH information. They need access to age-appropriate, youth-friendly services in order to have healthy sexual experiences.

  10. Tropical forest recovery from logging: a 24 year silvicultural experiment from Central Africa.

    PubMed

    Gourlet-Fleury, Sylvie; Mortier, Frédéric; Fayolle, Adeline; Baya, Fidèle; Ouédraogo, Dakis; Bénédet, Fabrice; Picard, Nicolas

    2013-01-01

    Large areas of African moist forests are being logged in the context of supposedly sustainable management plans. It remains however controversial whether harvesting a few trees per hectare can be maintained in the long term while preserving other forest services as well. We used a unique 24 year silvicultural experiment, encompassing 10 4 ha plots established in the Central African Republic, to assess the effect of disturbance linked to logging (two to nine trees ha⁻¹ greater than or equal to 80 cm DBH) and thinning (11-41 trees ha⁻¹ greater than or equal to 50 cm DBH) on the structure and dynamics of the forest. Before silvicultural treatments, above-ground biomass (AGB) and timber stock (i.e. the volume of commercial trees greater than or equal to 80 cm DBH) in the plots amounted 374.5 ± 58.2 Mg ha⁻¹ and 79.7 ± 45.9 m³ ha⁻¹, respectively. We found that (i) natural control forest was increasing in AGB (2.58 ± 1.73 Mg dry mass ha⁻¹ yr⁻¹) and decreasing in timber stock (-0.33 ± 1.57 m³ ha⁻¹ yr⁻¹); (ii) the AGB recovered very quickly after logging and thinning, at a rate proportional to the disturbance intensity (mean recovery after 24 years: 144%). Compared with controls, the gain almost doubled in the logged plots (4.82 ± 1.22 Mg ha⁻¹ yr⁻¹) and tripled in the logged + thinned plots (8.03 ± 1.41 Mg ha⁻¹ yr⁻¹); (iii) the timber stock recovered slowly (mean recovery after 24 years: 41%), at a rate of 0.75 ± 0.51 m³ ha⁻¹ yr⁻¹ in the logged plots, and 0.81 ± 0.74 m³ ha⁻¹ yr⁻¹ in the logged + thinned plots. Although thinning significantly increased the gain in biomass, it had no effect on the gain in timber stock. However, thinning did foster the growth and survival of small- and medium-sized timber trees and should have a positive effect over the next felling cycle.

  11. Tropical forest recovery from logging: a 24 year silvicultural experiment from Central Africa

    PubMed Central

    Gourlet-Fleury, Sylvie; Mortier, Frédéric; Fayolle, Adeline; Baya, Fidèle; Ouédraogo, Dakis; Bénédet, Fabrice; Picard, Nicolas

    2013-01-01

    Large areas of African moist forests are being logged in the context of supposedly sustainable management plans. It remains however controversial whether harvesting a few trees per hectare can be maintained in the long term while preserving other forest services as well. We used a unique 24 year silvicultural experiment, encompassing 10 4 ha plots established in the Central African Republic, to assess the effect of disturbance linked to logging (two to nine trees ha−1 greater than or equal to 80 cm DBH) and thinning (11–41 trees ha−1 greater than or equal to 50 cm DBH) on the structure and dynamics of the forest. Before silvicultural treatments, above-ground biomass (AGB) and timber stock (i.e. the volume of commercial trees greater than or equal to 80 cm DBH) in the plots amounted 374.5 ± 58.2 Mg ha−1 and 79.7 ± 45.9 m3 ha−1, respectively. We found that (i) natural control forest was increasing in AGB (2.58 ± 1.73 Mg dry mass ha−1 yr−1) and decreasing in timber stock (−0.33 ± 1.57 m3 ha−1 yr−1); (ii) the AGB recovered very quickly after logging and thinning, at a rate proportional to the disturbance intensity (mean recovery after 24 years: 144%). Compared with controls, the gain almost doubled in the logged plots (4.82 ± 1.22 Mg ha−1 yr−1) and tripled in the logged + thinned plots (8.03 ± 1.41 Mg ha−1 yr−1); (iii) the timber stock recovered slowly (mean recovery after 24 years: 41%), at a rate of 0.75 ± 0.51 m3 ha−1 yr−1 in the logged plots, and 0.81 ± 0.74 m3 ha−1 yr−1 in the logged + thinned plots. Although thinning significantly increased the gain in biomass, it had no effect on the gain in timber stock. However, thinning did foster the growth and survival of small- and medium-sized timber trees and should have a positive effect over the next felling cycle. PMID:23878332

  12. SEG Advances in Rotational Seismic Measurements

    SciTech Connect

    Pierson, Robert; Laughlin, Darren; Brune, Bob

    2016-10-17

    Significant advancements in the development of sensors to enable rotational seismic measurements have been achieved. Prototypes are available now to support experiments that help validate the utility of rotational seismic measurements.

  13. Various Approaches to Forward and Inverse Wide-Angle Seismic Modelling Tested on Data from DOBRE-4 Experiment

    NASA Astrophysics Data System (ADS)

    Janik, Tomasz; Środa, Piotr; Czuba, Wojciech; Lysynchuk, Dmytro

    2016-12-01

    The interpretation of seismic refraction and wide angle reflection data usually involves the creation of a velocity model based on an inverse or forward modelling of the travel times of crustal and mantle phases using the ray theory approach. The modelling codes differ in terms of model parameterization, data used for modelling, regularization of the result, etc. It is helpful to know the capabilities, advantages and limitations of the code used compared to others. This work compares some popular 2D seismic modelling codes using the dataset collected along the seismic wide-angle profile DOBRE-4, where quite peculiar/uncommon reflected phases were observed in the wavefield. The 505 km long profile was realized in southern Ukraine in 2009, using 13 shot points and 230 recording stations. Double PMP phases with a different reduced time (7.5-11 s) and a different apparent velocity, intersecting each other, are observed in the seismic wavefield. This is the most striking feature of the data. They are interpreted as reflections from strongly dipping Moho segments with an opposite dip. Two steps were used for the modelling. In the previous work by Starostenko et al. (2013), the trial-and-error forward model based on refracted and reflected phases (SEIS83 code) was published. The interesting feature is the high-amplitude (8-17 km) variability of the Moho depth in the form of downward and upward bends. This model is compared with results from other seismic inversion methods: the first arrivals tomography package FAST based on first arrivals; the JIVE3D code, which can also use later refracted arrivals and reflections; and the forward and inversion code RAYINVR using both refracted and reflected phases. Modelling with all the codes tested showed substantial variability of the Moho depth along the DOBRE-4 profile. However, SEIS83 and RAYINVR packages seem to give the most coincident results.

  14. A Case-Study of Dust Aerosol Uplift Mechanisms in North Africa during the Saharan Mineral Dust Experiment

    NASA Astrophysics Data System (ADS)

    Stenchikov, Georgiy; Weinzierl, Bernadett; Khan, Basit Ali; Kalenderski, Stoitchko

    2013-04-01

    Dust particles mixed in the free troposphere have longer lifetimes than airborne particles near the surface, suggesting that they could have strong cumulative radiative impact on the earth's radiative balance. One example is the elevated Saharan dust layer over equatorial North Atlantic, which cools the sea surface and likely suppresses hurricane activity. However, the uplift mechanisms of dust are complex and not well understood. In this study, we combined model simulations and dust observations collected during the Saharan Mineral Dust Experiment (SAMUM) to study the formation mechanisms of the Saharan elevated dust layer. SAMUM aimed to investigate the microphysical, optical, chemical, and radiative properties of Saharan mineral dust. Here, we focus on data from SAMUM-1, the first field experiment. During SAMUM-1, three large-scale dust events that extended from Morocco to Portugal occurred. Whereas the dust layers close to the source region of the dust were found to extend across the entire boundary layer from the surface to altitudes of about 4-6 km above sea level, in Casablanca situated on the Atlantic coast of Morocco, only elevated dust layers were observed. We employed the Weather Research Forecast model coupled with the Chemistry/Aerosol module (WRF-Chem) to interpret the observations. We configured WRF-Chem with the RADM2 (Regional Acid Deposition Model 2) photochemical mechanism, the Fast-J photolysis scheme, and the MADE/SORGAM (Modal Aerosol Dynamics Model for Europe (MADE) and Secondary Organic Aerosol Model (SORGAM) aerosol model. The GOCART dust emission scheme was coupled with the MADE/SORGAM aerosol model to account for the dust emission processes. The experimental domain covered northwest Africa including the southern Sahara, Morocco and part of the Atlantic Ocean, an area from 15°N to 36.5°N and 16°W to 11°E, with 550x484 grid points, 5 km horizontal grid spacing, and 51 vertical layers. To study convective processes in the region

  15. Building the Capacity to Build Capacity in e-Health in Sub-Saharan Africa: The KwaZulu-Natal Experience

    PubMed Central

    2012-01-01

    Abstract Background: Sub-Saharan Africa has a disproportionate burden of disease and an extreme shortage of health workers. There are already too few doctors to train doctors in specialities and sub-specialties. E-health is seen as a possible solution through distance education, telemedicine, and computerized health information systems but there are few people trained in e-health. We describe 12 years of experience at the University of KwaZulu-Natal (UKZ-N) in education and training in postgraduate medical disciplines, medical informatics, and telemedicine. Medical Education: Videoconferencing of seminars and grand rounds to regional training hospitals commenced in 2001 and has grown to 40 h of interactive conferencing taking place weekly during academic terms involving over 33,000 participants in 2010. Videoconferenced sessions are directly recorded to DVD and DVDs are sent to other medical schools in Africa that do not have the infrastructure to directly connect. E-health Education: Students and academic staff were initially sent to the United States for training in medical informatics and workshops were held in South Africa for people from sub-Saharan Africa. This led to the development of postgraduate academic programs in medical informatics and telemedicine at UKZ-N. African students were then brought to UKZ-N for training. The model was changed from UKZ-N to students and staff based at their home universities with the aim of building capacity in the staff at partner institutions so that they can in time offer their own e-health academic programs. Conclusions: The need for capacity development in all aspects of e-health in sub-Saharan Africa is great and innovative solutions are required. PMID:22150714

  16. On the ability of surface model to reproduce Soil moisture dependencies over West Africa: The ALMIP experiments

    NASA Astrophysics Data System (ADS)

    Cohard, J. M.; Boone, A. A.; Cappelaere, B.; Demarty, J.; Galle, S.; Manuela, G.; Guichard, F.; Kergoat, L.; Lohou, F.; Mamadou, O.; Peugeot, C.; Séguis, L.; Seghieri, J.

    2014-12-01

    From the AMMA-CATCH Observatory located in West Africa, a complete data set of surface exchanges over various vegetation landcovers is analysed. It is shown these exchanges, especially the Evapo-transpiration (ETR), primarily rely on surface soil moisture at annual time scales because of the seasonal cycle of the West African monsoon and the corresponding precipitation. However, at finer time scales, soil moisture dependencies are much more complex and no simple relation exists between ETR and soil moisture, especially when vegetation has developed. If the presence of adequate soil moisture is a prerequisite for any ETR rate, the interactions between all surface processes render the use of simple models inadequate. Several illustrations will be presented based on data analysis and ALMIP experiments. One of them concerns the surface model response at daily time step after a rain event. It is shown that, for all the experimental sites, the immediate surface response is mainly dependent on the soil moisture content especially for bare soil conditions. The ALMIP model ensemble broadly reproduce the ETR annual cycle but depicts a broad range of relationships between Evaporative Fraction and soil moisture, with the worst results for the driest sites. The second illustration concerns a comparison of local modelling results with in situ data. It is shown that the CLM model parameterisations are able to reproduce surface conductances. For bare soil conditions, the soil moisture dependency follows the Sakagushi law. During the vegetated period (over fallow), the evaporation rate is no longer controlled by soil moisture but by the radiative budget of the canopy and the amount of energy that reaches the ground. Finally, the Ball & Berry conductance model is able to reproduce transpiration rate reasonably well. This model is a function of incoming radiation and soil moisture, but also leaf temperature which impacts all of the surface energy exchanges.

  17. Women's experiences with cervical cancer screening in a colposcopy referral clinic in Cape Town, South Africa: a qualitative analysis

    PubMed Central

    Momberg, Mariette; Botha, Matthys H; Van der Merwe, Frederick H; Moodley, Jennifer

    2017-01-01

    Objective The aim of this study was to explore and understand women's experience with cervical cancer screening and with the referral pathways for abnormal Papanicolau (Pap) smears. Design and setting Focus group discussions were conducted with first time colposcopy clinic attendees at a tertiary hospital colposcopy clinic in Cape Town, South Africa during November 2014. A thematic analysis was conducted to identify key themes. Initial coding categories were drawn from the interview guide. Participants 27 women participated in 4 focus group discussions. Results Participants mean age was 34 years, most did not complete secondary level education and were unemployed. Negative community opinions relating to Pap smears and colposcopy referral might deter women from seeking treatment. Having a gynaecological symptom was the most commonly cited reason for having a Pap smear. Fear of having a HIV test performed at the same time as Pap smear and low encouragement from peers, were factors identified as potential access barriers. Participants commented on insufficient or lack of information from primary providers on referral to the colposcopy clinic and concerns and apprehension during waiting periods between receiving results and the colposcopy appointment were discussed. Conclusions There is a strong and urgent need to improve current knowledge about cervical cancer and Pap smears and the necessity and benefits of timely access to screening programmes, results and treatment. Strategies such as community health education programmes and mass media interventions could be employed to disseminate cervical cancer information and address negative community perceptions. Better training and support mechanisms to equip healthcare providers with the skills to convey cervical cancer information to women are needed. The use of short message service (SMS) to deliver Pap smear results and provide patients with more information should be considered to improve waiting times for results

  18. Mother's perceptions and experiences of infant feeding within a community-based peer counselling intervention in South Africa.

    PubMed

    Nor, Barni; Ahlberg, Beth Maina; Doherty, Tanya; Zembe, Yanga; Jackson, Debra; Ekström, Eva-Charlotte

    2012-10-01

    Exclusive breastfeeding (EBF) has the potential to significantly reduce infant mortality, but is frequently not practiced in low-income settings where infants are vulnerable to malnutrition and infections including human immunodeficiency virus (HIV). This study explores mothers' experiences of infant feeding after receiving peer counselling promoting exclusive breast or formula feeding. This qualitative study was embedded in a cluster randomized peer counselling intervention trial in South Africa that aimed to evaluate the effect of peer counselling on EBF. Participants were selected from the three districts that were part of the trial reflecting different socio-economic conditions, rural-urban locations and HIV prevalence rates. Seventeen HIV-positive and -negative mothers allocated to intervention clusters were recruited. Despite perceived health and economic benefits of breastfeeding, several barriers to EBF remained, which contributed to a preference for mixed feeding. The understanding of the promotional message of 'exclusive' feeding was limited to 'not mixing two milks': breast or formula and did not address early introduction of foods and other liquids. Further, a crying infant or an infant who did not sleep at night were given as strong reasons for introducing semi-solid foods as early as 1 month. In addition, the need to adhere to the cultural practice of 'cleansing' and the knowledge that this practice is not compatible with EBF appeared to promote the decision to formula feed in HIV-positive mothers. Efforts to reduce barriers to EBF need to be intensified and further take into account the strong cultural beliefs that promote mixed feeding.

  19. SOAR Telescope seismic performance II: seismic mitigation

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  20. Post-Gondwana geomorphic evolution of southwestern Africa: Implications for hte controls on landscape development from observations and numerical experiments

    NASA Technical Reports Server (NTRS)

    Gilchrist, Alan R.; Kooi, Henk; Beaumont, Christopher

    1994-01-01

    The relationship between morphology and surficial geology is used to quantify the denudation that has occurred across southwestern Africa sicne the fragmentation of Gondwana during the Early Mesozoic. Two main points emerge. Signficant denudation, of the order of kilometers, is widespread except in the Kalahari region of the continental interior. The denudation is systematically distributed so that the continental exterior catchment, draining directly to the Cape basin, is denuded to a greater depth than the interior catchment inland of the Great Escarpment. The analysis also implies tha the majority of the denudation occurred before the beginning of the Cenozoic for both teh exerior and interior catchments. Existing models of landscape development are reviewed, and implications of the denudation chronology are incorporated into a revised conceptual model. This revision implies tha thte primary effect of rifting on the subsequent landscape evolution is that it generates two distinct drainage regimes. A marginal upwarp, or rift flank uplift, separates rejuvenated rivers that drain into the subsiding rift from rivers in the continetal interior that are deflected but not rejuvenated. The two catchments evolve independently unless they are integrated by breaching of hte marginal upwarp. If this occurs, the exterior baselevel is communicated to the interior catchment that is denuded accordingly. Denudation rates generally decrease as the margin evolves, and this decrease is reinforced by the exposure of substrate that is resistant to denudation and/or a change to a more arid climate. The observations do not reveal a particular style of smaller-scale landscape evolution, sucha s escarpment retreat, that is responsible for the differential denudation across the region. It is proposed that numerical model experiments, which reflect the observational insights at the large scale, may identify the smaller-scale controls on escarpment development if the model and natural

  1. North Africa

    SciTech Connect

    Nicod, M.A.

    1981-10-01

    The total area covered by petroleum rights in the six countries described in this paper increased by more than 17% in 1980 compared to 1979. Joint venture agreements were finalized for 19 blocks over 94,000 km/sup 2/ in the Algerian venture. Although official information is scarce for Algeria and Libya, seismic activity probably increased in 1980 compared to 1979. Exploration drilling activity increased with 121 wildcats drilled compared to 93 during the previous year. This effort led to 40 discoveries, a 34.5% success ratio. Chevron was especially successful in wildcatting, with 6 oil discoveries for 8 wells drilled in the interior basins of Sudan. One Moroccan discovery can be considered as a highlight: the BRPM Meskala 101 well in the Essaouira basin found an apparently large amount of gas in Triassic sandstones. This discovery deserves special attention, since the gas has been found in Triassic pays rather than in the usual Jurassic pays in the Essaouira basin. Oil production in North Africa decreased from about 13.5% in 1980, with about 3,405,000 barrels of oil per day compared to 3,939,500 barrels of oil per day in 1979. When oil output strongly decreased in Algeria (-16.4%) and Libya (-15.6%), Tunisian production peaked at 116,287 barrels of oil per day and Egypt production also peaked at 584,148 barrels of oil per day. Total gas production in 1980 strongly declined from 44%, mostly due to the decline of the Algerian gas production. 8 figures, 40 tables.

  2. Seismic reflection data imaging and interpretation from Braniewo2014 experiment using additional wide-angle refraction and reflection and well-logs data

    NASA Astrophysics Data System (ADS)

    Trzeciak, Maciej; Majdański, Mariusz; Białas, Sebastian; Gaczyński, Edward; Maksym, Andrzej

    2015-04-01

    Braniewo2014 reflection and refraction experiment was realized in cooperation between Polish Oil and Gas Company (PGNiG) and the Institute of Geophysics (IGF), Polish Academy of Sciences, near the locality of Braniewo in northern Poland. PGNiG realized a 20-km-long reflection profile, using vibroseis and dynamite shooting; the aim of the reflection survey was to characterise Silurian shale gas reservoir. IGF deployed 59 seismic stations along this profile and registered additional full-spread wide-angle refraction and reflection data, with offsets up to 12 km; maximum offsets from the seismic reflection survey was 3 km. To improve the velocity information two velocity logs from near deep boreholes were used. The main goal of the joint reflection-refraction interpretation was to find relations between velocity field from reflection velocity analysis and refraction tomography, and to build a velocity model which would be consistent for both, reflection and refraction, datasets. In this paper we present imaging results and velocity models from Braniewo2014 experiment and the methodology we used.

  3. Emergency preparedness activities during an ongoing seismic swarm: the experience of the 2011-2012 Pollino (Southern Italy) sequence

    NASA Astrophysics Data System (ADS)

    Masi, A.; Mucciarelli, M.; Chiauzzi, L.; De Costanzo, G.; Loperte, G.

    2012-04-01

    Facing natural disasters effects can be a very difficult task lacking suitable activities and tools to preventively prepare the involved community (people, authorities, professionals, …) to the expected events. Therefore, a suite of preventive actions should be carried out to mitigate natural risks, in particular working to reduce the territorial vulnerability with respect to the specific natural hazard at hand, and to increase people response capacity. In fact, building social capacity helps to increase the risk perception and the people capacity to adapt to and cope with natural hazards. Since October 2011 a seismic swarm is affecting the Pollino mountain range, Southern Italy. At present the sequence is still ongoing, with more than 500 events with M>1, at least 40 well perceived by the population and a maximum magnitude at 3.6. The area mainly affected by the seismic sequence includes 12 villages, with a total population of about 50.000 inhabitants and, according to the current seismic hazard map it has high seismicity level. Such area was hit by a magnitude Ml=5.7 event in 1998 that produced macroseismic intensity not higher that VII-VIII degree of MCS scale and caused one dead, some injured and widespread damage in at least six municipalities. During the sequence, the National Department of Civil Protection (DPC) and the Civil Protection of Basilicata Region decided to put in action some measures aimed at verifying and enhancing emergency preparedness. These actions have been carried out with a constant and fruitful collaboration among the main stakeholders involved (scientific community, local and national governmental agencies, civil protection volunteers, etc) trough the following main activities: 1. collaboration between scientific community and the local and national offices of Civil Protection especially in the relationship with local authorities (e.g. mayors, which are civil protection authorities in their municipality); 2. interaction between DPC

  4. Recent Seismicity in Southern Illinois and Southern Missouri: Initial Results from the EarthScope OIINK Flexible Array Experiment

    NASA Astrophysics Data System (ADS)

    Yang, X.; Pavlis, G. L.; Hamburger, M. W.; Gilbert, H. J.; Marshak, S.; Rupp, J.; Larson, T. H.

    2012-12-01

    We examined 175 days' continuous seismic records, from July 29, 2011 through January 20, 2012, from stations in a study area encompassing the eastern Ozark Plateau in Missouri and the southern Illinois Basin. The records came from 23 flexible-array stations of the OIINK (Ozark, Illinois, INdiana and Kentucky) network, 21 transportable array stations of USArray, 7 New Madrid array stations, and 1 GSN station. These records yielded thousands of events, of which, 44 earthquakes with mb ≥ 2.0 occurred within the study area. Active quarries and coal mines dominate the catalog. To focus primarily on earthquakes, we generally ignored events that happened during the hours of 16:00 to 23:00 UTC, the time interval during which most blasting takes place. Of the remaining events, 443 events were classified as blasts because their records displayed relatively large amplitude, low frequency Rg waves compared to those of unambiguous earthquakes. About 25 of the 44 earthquakes were located within the New Madrid seismic zone, south of the array. A significant number of the remaining events cluster along the boundary between the Ozark Plateau and the Illinois Basin. Notably, these events occur at depths of between 10 and 20 km, the transition zone from upper to middle crust. This depth range is greater than that of the earthquakes elsewhere in and around the Ozark Plateau, where foci generally lie at depths of < 5 km. Our preliminary results indicate that the character of seismicity varies across the study area, and that the boundary between Ozark Plateau and the Illinois Basin, which has served as a significant tectonic boundary throughout the Phanerozoic, remains active.

  5. Next-generation seismic experiments: wide-angle, multi-azimuth, three-dimensional, full-waveform inversion

    NASA Astrophysics Data System (ADS)

    Morgan, Joanna; Warner, Michael; Bell, Rebecca; Ashley, Jack; Barnes, Danielle; Little, Rachel; Roele, Katarina; Jones, Charles

    2013-12-01

    Full-waveform inversion (FWI) is an advanced seismic imaging technique that has recently become computationally feasible in three dimensions, and that is being widely adopted and applied by the oil and gas industry. Here we explore the potential for 3-D FWI, when combined with appropriate marine seismic acquisition, to recover high-resolution high-fidelity P-wave velocity models for subsedimentary targets within the crystalline crust and uppermost mantle. We demonstrate that FWI is able to recover detailed 3-D structural information within a radially faulted dome using a field data set acquired with a standard 3-D petroleum-industry marine acquisition system. Acquiring low-frequency seismic data is important for successful FWI; we show that current acquisition techniques can routinely acquire field data from airguns at frequencies as low as 2 Hz, and that 1 Hz acquisition is likely to be achievable using ocean-bottom hydrophones in deep water. Using existing geological and geophysical models, we construct P-wave velocity models over three potential subsedimentary targets: the Soufrière Hills Volcano on Montserrat and its associated crustal magmatic system, the crust and uppermost mantle across the continent-ocean transition beneath the Campos Basin offshore Brazil, and the oceanic crust and uppermost mantle beneath the East Pacific Rise mid-ocean ridge. We use these models to generate realistic multi-azimuth 3-D synthetic seismic data, and attempt to invert these data to recover the original models. We explore resolution and accuracy, sensitivity to noise and acquisition geometry, ability to invert elastic data using acoustic inversion codes, and the trade-off between low frequencies and starting velocity model accuracy. We show that FWI applied to multi-azimuth, refracted, wide-angle, low-frequency data can resolve features in the deep crust and uppermost mantle on scales that are significantly better than can be achieved by any other geophysical technique, and

  6. Seismic Reflection Imaging of the Lithosphere-asthenosphere Boundary Across the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Singh, S. C.; Marjanovic, M.; Audhkhasi, P.; Mehouachi, F.

    2015-12-01

    Until now, the nature of the lithosphere-asthenosphere boundary (LAB) has been constrained by teleseismic data, which has resolution of tens of kilometres and sample the LAB sparsely. Seismic reflection imaging technique, in contrast, can provide both lateral and vertical resolution of a few hundred meters, but has not been used for imaging deep structures, thus so far. In March-April 2015, we acquired over 2,750 km of ultra-deep seismic reflection data in the Atlantic Ocean. To image LAB variations as a function of age one of our profiles extends continuously starting from 75 Ma old oceanic lithosphere off the margin of Africa, crosses the Mid-Atlantic Ridge at zero age, to up to 25 Ma old South America lithosphere. To image large differences in the LAB depth we also cross three major fracture zones in the equatorial Atlantic. For imaging deep structures, we used a very large energy source, 10,170 cubic inches, rich in low frequencies and a 12 km long multi-component streamer allowing to record low frequency energy reflected from deep earth and remove reverberation in the water column. Initial results show reflected seismic energy from 50-60 km depth. The seismic reflection experiment will be complemented by seismic refraction study to determine the crustal and upper mantle P-wave velocity, magnetotelluric study to determine resistivity, and broadband ocean bottom seismometer experiment for teleseismic study, collocated with our seismic reflection profiles. In this paper, we will present the design of the seismic reflection experiment and preliminary results from the onboard processed data.

  7. High-resolution seismic imaging in deep sea from a joint deep-towed/OBH reflection experiment: application to a Mass Transport Complex offshore Nigeria

    NASA Astrophysics Data System (ADS)

    Ker, S.; Marsset, B.; Garziglia, S.; Le Gonidec, Y.; Gibert, D.; Voisset, M.; Adamy, J.

    2010-09-01

    We assess the feasibility of high-resolution seismic depth imaging in deep water based on a new geophysical approach involving the joint use of a deep-towed seismic device (SYSIF) and ocean bottom hydrophones (OBHs). Source signature measurement enables signature deconvolution to be used to improve the vertical resolution and signal-to-noise ratio. The source signature was also used to precisely determine direct traveltimes that were inverted to relocate source and receiver positions. The very high accuracy of the positioning that was obtained enabled depth imaging and a stack of the OBH data to be performed. The determination of the P-wave velocity distribution was realized by the adaptation of an iterative focusing approach to the specific acquisition geometry. This innovative experiment combined with advanced processing succeeded in reaching lateral and vertical resolution (2.5 and 1 m) in accordance with the objectives of imaging fine scale structures and correlation with in situ measurements. To illustrate the technological and processing advances of the approach, we present a first application performed during the ERIG3D cruise offshore Nigeria with the seismic data acquired over NG1, a buried Mass Transport Complex (MTC) interpreted as a debris flow by conventional data. Evidence for a slide nature of a part of the MTC was provided by the high resolution of the OBH depth images. Rigid behaviour may be inferred from movement of coherent material inside the MTC and thrust structures at the base of the MTC. Furthermore, a silt layer that was disrupted during emplacement but has maintained its stratigraphic position supports a short transport distance.

  8. Investigating the lithospheric structure of Queen Maud Land, East-Antarctica: a year-round seismic experiment

    NASA Astrophysics Data System (ADS)

    Lombardi, Denis; Camelbeeck, Thierry; Rapagnani, Giovanni

    2014-05-01

    The recently launched LISSA project is dedicated to imaging the lithospheric structure of East-Antarctica in relation with the past geodynamics of Gondwana by probing the Sør Rondane Mountains, Queen Maud Land, a belt formed from various metamorphosed terranes mobilized during the Proterozoic Pan-African orogeny. The project benefits from the establishment in 2009 of the Belgian Princess Elisabeth base built at the northern tip of the mountain chain. Our aim is to investigate the deep lithospheric structure of the region by setting up in January 2014 6 broadband seismic stations along a 100 km long North-South profile through the mountain belt striking perpendicular to the various geological terranes. All stations are set up to be year-round autonomously powered, all but one being on rock outcrops and only one being remotely accessible. We describe the technical developpment for year-round operation and the installation site conditions. Then we present the first collected data by analyzing the background seismic noise providing data quality and finally we provide a first inventory of a 1 month event dataset.

  9. Seismotectonics and crustal deformation in Africa

    NASA Astrophysics Data System (ADS)

    Ayadi, Abdelhakim

    2016-04-01

    We present the Seismotectonic Map of Africa based on a geological, geophysical and geodetic database including the instrumental seismicity and re-appraisal of large historical events, and harmonization and homogenization of earthquake parameters in catalogues. Although the seismotectonic framework of the African continent is a difficult task, several previous and ongoing projects provide a wealth of data and outstanding results. The database of large and moderate earthquakes in different geological domains includes the coseismic and Quaternary faulting that reveals the complex nature of the active tectonics in Africa. The map benefits from previous works on local and regional seismotectonic maps that needed to be integrated with the lithospheric and upper mantle structures, seismic anisotropy tomography and gravity anomaly, into a continental framework. The synthesis of earthquake and volcanic studies obtained from the analysis of late Quaternary faulting and geodetic data will serve as a basis for hazard calculations and the reduction of seismic risks. The map will be useful for the seismic hazard assessment and earthquake risk mitigation for significant infrastructures and their socio-economic implications in Africa. The constant population increase and infrastructure growth in the continent that exacerbate the earthquake risk justify the necessity for a continuous updating of this map. The database and related map are prepared in the framework of the IGC Project-601 "Seismotectonics and Seismic Hazards in Africa" of UNESCO-IUGS, funded by the Swedish International Development Agency and UNESCO-Nairobi for a period of 4 years (2011 - 2014, now extended to 2016).

  10. Health policy for sickle cell disease in Africa: experience from Tanzania on interventions to reduce under-five mortality

    PubMed Central

    Makani, Julie; Soka, Deogratias; Rwezaula, Stella; Krag, Marlene; Mghamba, Janneth; Ramaiya, Kaushik; Cox, Sharon E.; Grosse, Scott D.

    2015-01-01

    Tanzania has made considerable progress towards reducing childhood mortality, achieving a 57% decrease between 1980 and 2011. This epidemiological transition will cause a reduction in the contribution of infectious diseases to childhood mortality and increase in contribution from noncommunicable diseases (NCDs). Haemoglobinopathies are amongst the most common childhood NCDs, with sickle cell disease (SCD) being the commonest haemoglobinopathy in Africa. In Tanzania, 10 313 children with SCD under 5 years of age (U5) are estimated to die every year, contributing an estimated 7% of overall deaths in U5 children. Key policies that governments in Africa are able to implement would reduce mortality in SCD, focusing on newborn screening and comprehensive SCD care programmes. Such programmes would ensure that interventions such as prevention of infections using penicillin plus prompt diagnosis and treatment of complications are provided to all individuals with SCD. PMID:25365928

  11. Health policy for sickle cell disease in Africa: experience from Tanzania on interventions to reduce under-five mortality.

    PubMed

    Makani, Julie; Soka, Deogratias; Rwezaula, Stella; Krag, Marlene; Mghamba, Janneth; Ramaiya, Kaushik; Cox, Sharon E; Grosse, Scott D

    2015-02-01

    Tanzania has made considerable progress towards reducing childhood mortality, achieving a 57% decrease between 1980 and 2011. This epidemiological transition will cause a reduction in the contribution of infectious diseases to childhood mortality and increase in contribution from non-communicable diseases (NCDs). Haemoglobinopathies are amongst the most common childhood NCDs, with sickle cell disease (SCD) being the commonest haemoglobinopathy in Africa. In Tanzania, 10,313 children with SCD under 5 years of age (U5) are estimated to die every year, contributing an estimated 7% of overall deaths in U5 children. Key policies that governments in Africa are able to implement would reduce mortality in SCD, focusing on newborn screening and comprehensive SCD care programmes. Such programmes would ensure that interventions such as prevention of infections using penicillin plus prompt diagnosis and treatment of complications are provided to all individuals with SCD.

  12. Crustal structures from the Wuyi-Yunkai orogen to the Taiwan orogen: The onshore-offshore wide-angle seismic experiments of the TAIGER and ATSEE projects

    NASA Astrophysics Data System (ADS)

    Kuo, Yao-Wen; Wang, Chien-Ying; Kuo-Chen, Hao; Jin, Xin; Cai, Hui-Teng; Lin, Jing-Yi; Wu, Francis T.; Yen, Horng-Yuan; Huang, Bor-Shouh; Liang, Wen-Tzong; Okaya, David; Brown, Larry

    2016-12-01

    Knowledge of the crustal structure is important for understanding the tectonic framework and geological evolution of southeastern China and adjacent areas. In this study, we integrated the datasets from the TAIGER (TAiwan Integrated GEodynamic Research) and ATSEE (Across Taiwan Strait Explosion Experiment) projects to resolve onshore-offshore deep crustal seismic profiles from the Wuyi-Yunkai orogen to the Taiwan orogen in southeastern China. Three seismic profiles were resolved, and the longest profile was 850 km. Unlike 2D and 3D first arrival travel-time tomography from previous studies, we used both refracted and reflected phases (Pg, Pn, PcP, and PmP) to model the crustal structures and the crustal reflectors. In total, data from 40 shots, 2 earthquakes, and approximately 1,950 stations were used; 15,612 arrivals were selected among three transects. Using these data, we determined the complex crustal evolution since the Paleozoic era , involving the closed Paleozoic rift basin in central Fujian, the Cenozoic extension due to the South China Sea opening beneath the coastline of southern Fujian, and the on-going collision of the Taiwan orogen. The shape of the Moho, which also reflects the crustal evolution, can be summarized as follows: 30 km deep to the west of Fujian, deepening toward central Fujian ( 35 km), becoming shallower toward the Taiwan Strait ( 28 km), deepening again toward the mountain belt of Taiwan ( 42 km), and becoming shallower toward the Pacific Ocean ( 10 km).

  13. Dynamic Assessment of Seismic Risk (DASR) by Multi-parametric Observations: Preliminary Results of PRIME experiment within the PRE-EARTHQUAKES EU-FP7 Project

    NASA Astrophysics Data System (ADS)

    Tramutoli, V.; Inan, S.; Jakowski, N.; Pulinets, S. A.; Romanov, A.; Filizzola, C.; Shagimuratov, I.; Pergola, N.; Ouzounov, D. P.; Papadopoulos, G. A.; Parrot, M.; Genzano, N.; Lisi, M.; Alparlsan, E.; Wilken, V.; Tsybukia, K.; Romanov, A.; Paciello, R.; Zakharenkova, I.; Romano, G.

    2012-12-01

    The integration of different observations together with the refinement of data analysis methods, is generally expected to improve our present knowledge of preparatory phases of earthquakes and of their possible precursors. This is also the main goal of PRE-EARTHQUAKES (Processing Russian and European EARTH observations for earthQUAKE precursors Studies) the FP7 Project which, to this aim, committed together, different international expertise and observational capabilities, in the last 2 years. In the learning phase of the project, different parameters (e.g. thermal anomalies, total electron content, radon concentration, etc.), measured from ground and satellite systems and analyzed by using different data analysis approaches, have been studied for selected geographic areas and specific seismic events in the past. Since July 2012 the PRIME (PRE-EARTHQUAKES Real-time Integration and Monitoring Experiment) started attempting to perform, on the base of independent observations collected and integrated in real-time through the PEG (PRE-EARTHQUAKES Geo-portal), a Dynamic Assessment of Seismic Risk (DASR) on selected geographic areas of Europe (Italy-Greece-Turkey) and Asia (Kamchatka, Sakhalin, Japan). In this paper, results so far achieved as well as the potential and opportunities they open for a worldwide Earthquake Observation System (EQuOS) - as a dedicated component of GEOSS (Global Earth Observation System of Systems) - will be presented.

  14. 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.

  15. Next-generation seismic experiments: wide-angle, multi-azimuth, three-dimensional, full-waveform inversion

    NASA Astrophysics Data System (ADS)

    Bell, Rebecca; Morgan, Joanna; Warner, Michael

    2016-04-01

    There are many outstanding plate-tectonic scale questions that require us to know information about sub-surface physical properties, for example ascertaining the geometry and location of magma chambers and estimating the effective stress along plate boundary faults. These important scientific targets are often too deep, impractical and expensive for extensive academic drilling. Full-waveform inversion (FWI) is an advanced seismic imaging technique that has recently become feasible in three dimensions, and has been widely adopted by the oil and gas industry to image reservoir-scale targets at shallow-to-moderate depths. In this presentation we explore the potential for 3-D FWI, when combined with appropriate marine seismic acquisition, to recover high-resolution high-fidelity P-wave velocity models for sub-sedimentary targets within the crystalline crust and uppermost mantle. Using existing geological and geophysical models, we construct P-wave velocity models over three potential sub-sedimentary targets: the Soufrière Hills Volcano on Montserrat and its associated crustal magmatic system, the downgoing oceanic plate beneath the Nankai subduction margin, and the oceanic crust-uppermost mantle beneath the East Pacific Rise mid-ocean ridge. We use these models to generate realistic multi-azimuth 3-D synthetic seismic data, and attempt to invert these data to recover the original models. We explore the resolution and accuracy, sensitivity to noise and acquisition geometry, ability to invert elastic data using acoustic inversion codes, and the trade-off between low frequencies and starting velocity model accuracy. We will show that FWI applied to multi-azimuth, refracted, wide-angle, low-frequency data can resolve features in the deep crust and uppermost mantle on scales that are significantly better than can be achieved by any other geophysical technique, and that these results can be obtained using relatively small numbers (60-90) of ocean-bottom receivers combined

  16. Seismic Discrimination

    DTIC Science & Technology

    1981-03-31

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

  17. Seismic seiches

    USGS Publications Warehouse

    McGarr, Arthur; Gupta, Harsh K.

    2011-01-01

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

  18. High-Frequency Seismic Waves generated by Building-Shaking Experiments and Surface Wave Group Velocity Estimates from the Cross-Correlation of Data

    NASA Astrophysics Data System (ADS)

    Tanimoto, T.; Okamoto, T.

    2013-12-01

    Modeling high-frequency (>1 Hz) seismic waves is known to be difficult but it is extremely important for earthquake hazard mitigation as many buildings have resonant frequencies above 1 Hz. In this study, we examine high-frequency waves at 1.64 Hz, generated by building-shaking experiments in California. The specific data we will examine are seismic data generated by shaking experiments of the Millikan Library between 2000 and 2002, located on the campus of California Institute of Technology in Pasadena, California. The excited wavefields were recorded by the broadband seismic network in the region (~150 stations), Southern California Seismic Network (SCSN). There were about 60 stations with good signal-to-noise ratios among SCSN stations. The maximum distance for signal detection was 323 km (station GRA). Based on numerical calculations for a regional seismic structure model (SCEC Community Velocity Model 11.9), we can show that the signals are dominated by surface waves (at 1.11 Hz and 1.64 Hz), whose energy is confined to shallow depths. The focus of this report will be on the cross-correlated signals between a station in the building (station MIK) and other stations. This cross-correlation may be viewed as a source deconvolution process and will let us focus on propagation in the medium. This cross-correlated phase can be expressed as a line integral of wavenumber along a propagation path for a direct (ballistic) phase, although it may contain complexity from the caustics (the Maslov index). Somewhat to our surprise, despite the fact that we are dealing with high frequency waves (1.64 Hz), we observe well-defined constant phase in many cross-correlated seismograms. If we knew the number of cycles between the source (Millikan) and a station, we could estimate phase velocity in principle but this is not possible and seems extremely hard because the number of cycles is about 50-100 or more. However, our signals do show frequency-dependence within a narrow (signal

  19. Increasing diversity in the geosciences through the AfricaArray geophysics field course

    NASA Astrophysics Data System (ADS)

    Vallejo, G.; Emry, E.; Galindo, B. L.; Carranza, V.; Gomez, C. D.; Ortiz, K.; Castro, J. G.; Guandique, J.; Falzone, C.; Webb, S. J.; Manzi, M.; Mngadi, S. B.; Stephens, K.; Chinamora, B.; Whitehead, R.; de Villiers, D. P.; Tshitlho, K.; Delhaye, R. P.; Smith, J. A.; Nyblade, A.

    2014-12-01

    For the past nine years, the AfricaArray diversity program, sponsored by industry, the National Science Foundation, and several partnering universities have supported outstanding U.S. STEM underrepresented minority undergraduates to gain field experience in near-surface geophysical techniques during an 8-week summer program at Penn State University and the University of Witwatersrand (Wits). The AfricaArray geophysics field school, which is run by Wits, has been teaching field-based geophysics to African students for over a decade. In the first 2-3 weeks of the program, the U.S. students are given basic instruction in near-surface geophysics, South African geology, and South African history and culture. The students then join the Wits AfricaArray geophysics field school - working alongside Wits students and students from several other African universities to map the shallow subsurface in prospective areas of South Africa for platinum mining. In addition to the primary goals of collecting and interpreting gravity, magnetic, resistivity, seismic refraction, seismic reflection, and EM data, students spend time mapping geologic units and gathering information on the physical properties of the rocks in the region (i.e. seismic velocity, density, and magnetic susceptibility). Subsurface targets include mafic dikes, faults, the water table, and overburden thickness. Upon returning to the U.S., students spend 2-3 weeks finalizing their project reports and presentations. The program has been effective at not only providing students with fundamental skills in applied geophysics, but also in fostering multicultural relationships, preparing students for graduate work in the geosciences, and attracting STEM students into the geosciences. Student presenters will discuss their experiences gained through the field school and give their impressions about how the program works towards the goal of increasing diversity in the geosciences in the U.S.

  20. The international seismological observing period in Africa

    USGS Publications Warehouse

    Engdahl, E.R.; Bergman, Eric A.

    1992-01-01

    The International Seismological Observing Period (ISOP) is a specific time interval designated for enhanced international cooperation in the collection and dissemination of observatory measurements from the global seismographic network. The primary purpose of the ISOP is to strengthen the international infrastructure that supports current seismological practice and increase the cooperation among nations that operate seismological observatories. Measurements, reported by the existing global network and compiled by agencies such as the International Seismological Centre (ISC), are providing new information about earthquakes and the structure of the Earth of fundamental importance to the Earth sciences. However, these data represent but a small fraction of the information contained in the seismograms. One of the goals of the ISOP is to collect improved sets of data. In particular, the measurement and reporting of later-arriving phases, during a fixed ISOP period, from earthquakes selected for detailed observation by the cooperating stations will be encouraged. The use of advanced, digital instrumentation provides an unprecedented opportunity for enhancing the methods of seismogram interpretation and seismic parameter extraction, by the implementation of digital processing methods at seismic observatories worldwide. It must be ensured that this new information will be available to the entire seismological community. It is believed that this purpose is best served with an ISOP that promotes increased on-site processing at digital stations in Africa and elsewhere. Improvements in seismology require truly international cooperation and the educational aspects of seismological practice form one of the goals of the ISOP. Thus, workshops will be needed in Africa to train analysts in ISOP procedures and to introduce them to modern techniques and applications of the data. Participants will, thus, benefit from theoretical results and practical experience that are of direct

  1. Juan de Fuca Plate Ridge-to-Trench Experiment: initial results from active source seismic imaging of the Juan de Fuca plate and Cascadia fore-arc (Invited)

    NASA Astrophysics Data System (ADS)

    Carbotte, S. M.; Canales, J.; Carton, H. D.; Han, S.; Gibson, J. C.; Janiszewski, H. A.; Horning, G.; Nedimovic, M. R.; Abers, G. A.; Trehu, A. M.

    2013-12-01

    Active source seismic data were acquired during the Juan de Fuca Ridge-to-Trench experiment (June-July 2012) to characterize the evolution and structure of the Juan de Fuca plate from formation at the ridge, through evolution in the plate interior, to subduction at the Cascadia trench. The survey provides plate-scale images of the sediments, crust, and shallowest mantle along two ridge-perpendicular transects, one extending from Axial seamount to the Oregon margin near Hydrate Ridge and the other from near Endeavour segment to Grays Harbor offshore Washington. In addition, a 450 km long trench-parallel line ~10 km seaward of the Cascadia deformation front was acquired to characterize variations in plate structure along the margin. Coincident long-streamer (8 km) multi-channel seismic (MCS) and wide-angle ocean bottom seismometer (OBS) data were collected along each transect. Using these data, our current investigations focus on the properties of the thick sediment blanket covering the Juan de Fuca plate and evidence for fluid flow at the deformation front, crustal structure within the plate interior and near the deformation front, and tracking the downgoing plate beneath the margin. Highlights include the discovery of numerous pockmarks on the seafloor providing evidence of active fluid flow up to 60 km west of the deformation front. Along the Oregon transect, a bright decollement horizon is imaged at ~1sec twtt above basement whereas at the Washington margin, protothrusts of the deformation front reach to the top of the oceanic crust. Variations in sediment properties are documented within the margin-parallel transect with changes in the stratigraphic level of decollement. While crustal thickness is quite uniform along the margin (~ 6 km), variations in crustal reflectivity and in shallowest mantle velocities are observed over ~30-50 km length scales that could be related to structural variations in the Cascadia subduction zone. Further landward, the top of the

  2. Topography and tectonics of the central New Madrid seismic zone: Results of numerical experiements using a three-dimensional boundary element program

    NASA Technical Reports Server (NTRS)

    Gomberg, Joan; Ellis, Michael

    1994-01-01

    We present results of a series of numerical experiments designed to test hypothetical mechanisms that derive deformation in the New Madrid seismic zone. Experiments are constrained by subtle topography and the distribution of seismicity in the region. We use a new boundary element algorithm that permits calcuation of the three-dimensional deformation field. Surface displacement fields are calculated for the New Madrid zone under both far-field (plate tectonics scale) and locally derived driving strains. Results demonstrate that surface displacement fields cannot distinguish between either a far-field simple or pure shear strain field or one that involves a deep shear zone beneath the upper crustal faults. Thus, neither geomorphic nor geodetic studies alone are expected to reveal the ultimate driving mechanism behind the present-day deformation. We have also tested hypotheses about strain accommodation within the New Madrid contractional step-over by including linking faults, two southwest dipping and one vertical, recently inferred from microearthquake data. Only those models with step-over faults are able to predict the observed topography. Surface displacement fields for long-term, relaxed deformation predict the distribution of uplift and subsidence in the contractional step-over remarkably well. Generation of these displacement fields appear to require slip on both the two northeast trending vertical faults and the two dipping faults in the step-over region, with very minor displacements occurring during the interseismic period when the northeast trending vertical faults are locked. These models suggest that the gently dippling central step-over fault is a reverse fault and that the steeper fault, extending to the southeast of the step-over, acts as a normal fault over the long term.

  3. Southern Africa

    Atmospheric Science Data Center

    2013-04-16

    ... tip of South Africa is at the bottom of the image, and Zambia is at the top. Distinctive features about a third of the way from the ... MISR Team. Aug 25, 2000 - South Africa to Zambia including the Okavango Delta. project:  MISR ...

  4. Experience from a multi-country initiative to improve the monitoring of selected reproductive health indicators in Africa.

    PubMed

    Barreix, Maria; Tunçalp, Özge; Mutombo, Namuunda; Adegboyega, Ayotunde A; Say, Lale

    2017-01-21

    Universal access to sexual and reproductive health remains part of the unfinished business of global development in Africa. To achieve it, health interventions should be monitored using programmatic indicators. WHO's Strengthening Measurement of Reproductive Health Indicators in Africa initiative, implemented in Ghana, Nigeria, Kenya, Uganda, and Zimbabwe, aimed to improve national information systems for routine monitoring of reproductive health indicators. Participating countries developed action plans employing a two-pronged strategy: (1) revising, standardizing, and harmonizing existing reproductive health indicators captured through routine information-systems; and (2) building data-collection capacity through training and supervision at select pilot sites. Country teams evaluated existing and new indicators, and outlined barriers to strengthening routine measurement. Activities included updating abortion-care guidelines (spontaneous and induced abortions), providing training on laws surrounding induced abortions, and improving feedback mechanisms. The country teams updated monitoring and evaluation frameworks, and attempted to build recording/reporting capacity in selected pilot areas. Barriers to implementing the initiative that were encountered included restrictive induced-abortion laws, staff turn-over, and administrative delays, including low capacity among healthcare staff and competing priorities for staff time. The areas identified for further improvement were up-scaling programs to a national level, creating scorecards to record data, increasing collaborations with the private sector, conducting related costing exercises, and performing ex-post evaluations.

  5. Strengthening public health education in population and reproductive health through an innovative academic partnership in Africa: the Gates partners experience.

    PubMed

    Oni, Gbolahan; Fatusi, Adesegun; Tsui, Amy; Enquselassie, Fikre; Ojengbede, Oladosu; Agbenyega, Tsiri; Ojofeitimi, Ebenezer; Taulo, Frank; Quakyi, Isabella

    2011-01-01

    Poor reproductive health constitutes one of the leading public health problems in the world, particularly in sub-Saharan Africa (SSA). We report here an academic partnership that commenced in 2003 between a US institution and six universities in SSA. The partnership addresses the human resources development challenge in Africa by strengthening public health education and research capacity to improve population and reproductive health (PRH) outcomes in low-resource settings. The partnership's core activities focused on increasing access to quality education, strengthening health research capacity and translating scholarship and science into policy and practices. Partnership programmes focused on the educational dimension of the human resources equation provide students with improved learning facilities and enhanced work environments and also provide faculty with opportunities for professional development and an enhanced capacity for curriculum delivery. By 2007, 48 faculty members from the six universities in SSA attended PRH courses at Johns Hopkins University, 93 PRH courses were offered across the six universities, 625 of their master's students elected PRH concentrations and 158 had graduated. With the graduation of these and future student cohorts, the universities in SSA will systematically be expanding the number of public health practitioners and strengthening programme effectiveness to resolve reproductive health needs. Some challenges facing the partnership are described in this article.

  6. The potential impact of pneumococcal conjugate vaccine in Africa: Considerations and early lessons learned from the South African experience.

    PubMed

    Madhi, Shabir A; Nunes, Marta C

    2016-01-01

    The introduction of pneumococcal conjugate vaccine (PCV) into the South African public immunization program since 2009 adopted a novel vaccination schedule of 3 doses at 6, 14 and 40 weeks of age. Over the past 5 y it has been shown that infant PCV immunization in South Africa is effective in reducing the burden of invasive pneumococcal disease (IPD) among HIV-infected and HIV-uninfected children. Furthermore, indirect protection of unvaccinated age-groups (including high risk groups such as HIV-infected adults) against IPD was demonstrated despite the absence of any substantial catch-up campaign of older children. This indirect effect against IPD is corroborated by the temporal reduction in vaccine-serotype colonization among age-groups targeted for PCV immunization as well as unvaccinated HIV-infected and HIV-uninfected adults, which was evident within 2 y of PCV introduction into the immunization program. Vaccine effectiveness has also been demonstrated in children against presumed bacterial pneumonia. The evaluation of the impact of PCV in South Africa, however, remains incomplete. The knowledge gaps remaining include the evaluation of PCV on the incidence of all-cause pneumonia hospitalization among vaccinated and unvaccinated age-groups. Furthermore, ongoing surveillance is required to determine whether there is ongoing replacement disease by non-vaccine serotypes, which could offset the early gains associated with the immunization program in the country.

  7. The cost implications of participatory research. Experience of a health services review in a rural region in South Africa

    PubMed

    Doherty; Price

    1998-03-01

    OBJECTIVES: The study objectives were to estimate the total costs incurred by a comprehensive review of primary health care services in a rural region in South Africa, and to determine which of these costs were incurred because of the participatory research techniques employed by the review. DESIGN: The costing study estimated the direct and indirect costs of each component of the review in order to determine total costs. Costs that were linked to participatory research activities were aggregated separately. SETTING: The review that was costed was conducted in an area that included the former 'homeland' KaNgwane and the adjacent areas of 'white' South Africa, in part of what is now known as Mpumalanga Province. SUBJECTS: Not relevant. OUTCOME MEASURES: Direct, indirect, total, research and participation costs were used as outcome measures. RESULTS: Expenditure generated by participatory research techniques was estimated to be almost 14% of the total (direct and indirect) costs. CONCLUSIONS: Despite these costs, participatory research techniques are invaluable in terms of the many benefits they have for a research project. However, because of these costs, it is important that the financing of participatory research should be carefully planned. Projects must budget for the direct costs of participatory techniques, participating organisations and individuals must be committed to bearing the indirect costs of participation, and, increasingly, funders must consider funding these indirect costs. This is important in the South African situation, where public health research relies increasingly on the participation of relevant stakeholders.

  8. Some aspect of seismicity prior to the 27 November 2006 eruption of Nyamuragira volcano and its implication for volcano monitoring and risk mitigation in the Virunga area, Western Rift Valley of Africa

    NASA Astrophysics Data System (ADS)

    Mavonga, Tuluka; Kavotha, Sadaka K.; Lukaya, Nyombo; Etoy, Osodundu; Mifundu, Wafula; Bizimungu, Rusangiza K.; Durieux, Jacques

    2010-12-01

    The temporal variation in the seismicity in the Nyamuragira area was investigated for the period 1 July 2004-27 November 2006, prior to the 27 November 2006 eruptions of Nyamuragira. It is found that this eruption was preceded by 11 months by progressive increase in number of long-period earthquakes. This pattern of seismicity, integrated with other geophysical, geological and geochemistry data, is useful for volcano monitoring and risk mitigation.

  9. The Tanami deep seismic reflection experiment: An insight into gold mineralization and Paleoproterozoic collision in the North Australian Craton

    NASA Astrophysics Data System (ADS)

    Goleby, Bruce R.; Huston, David L.; Lyons, Patrick; Vandenberg, Leon; Bagas, Leon; Davies, Brett M.; Jones, Leonie E. A.; Gebre-Mariam, Musie; Johnson, Wade; Smith, Tim; English, Luc

    2009-07-01

    Imaging of a major collision zone between the Tanami region and Aileron Province of the Arunta Orogen in Northern Australia, and recognition that several of the major gold deposits within the Tanami region are within near-surface antiformal stacks or uplifted and exhumed crustal sections associated with major crustal-penetrating shear zones, are fundamental results from the 2005 Tanami Seismic Collaborative Research Project. The suture, which is interpreted to have resulted from collision, separates the northwest-dipping structural grain of the Aileron Province crust in the south from the southeast-dipping structural grain of the Tanami crust in the northwest. The collision between the Tanami region and the Aileron Province is interpreted to have occurred prior to ca. 1840 Ma. The correlation between the surface extension of crustal-penetrating shear zones that extend to the Moho boundary and the locations of known gold-rich mineral fields is significant and has implications for minerals explorers within the Tanami region, and elsewhere. In the near-surface, where the crustal-penetrating structures cut relatively shallow upper crustal Tanami Group rocks, there is a significant increase in the degree of local deformation and results in through-going thrust faults, associated pop-up structures, ramp anticlines and antiformal stacking. All known ore deposits appear to be located within these more complexly deformed zones and therefore have a direct association with larger-scale structures.

  10. 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

  11. Addiction and treatment experiences among active methamphetamine users recruited from a township community in Cape Town, South Africa: a mixed-methods study

    PubMed Central

    Meade, Christina S.; Towe, Sheri L.; Watt, Melissa H.; Lion, Ryan R.; Myers, Bronwyn; Skinner, Donald; Kimani, Stephen; Pieterse, Desiree

    2015-01-01

    Background Since 2000, there has been a dramatic increase in methamphetamine use in South Africa, but little is known about the experiences of out-of-treatment users. This mixed-methods study describes the substance use histories, addiction symptoms, and treatment experiences of a community-recruited sample of methamphetamine users in Cape Town. Methods Using respondent driven sampling, 360 methamphetamine users (44% female) completed structured clinical interviews to assess substance abuse and treatment history and computerized surveys to assess drug-related risks. A sub-sample of 30 participants completed in-depth interviews to qualitatively explore experiences with methamphetamine use and drug treatment. Results Participants had used methamphetamine for an average of 7.06 years (SD=3.64). They reported using methamphetamine on an average of 23.49 of the past 30 days (SD=8.90); 60% used daily. The majority (90%) met ICD-10 criteria for dependence, and many reported severe social, financial, and legal consequences. While only 10% had ever received drug treatment, 90% reported that they wanted treatment. In the qualitative interviews, participants reported multiple barriers to treatment, including beliefs that treatment is ineffective and relapse is inevitable in their social context. They also identified important motivators, including desires to be drug free and improve family functioning. Conclusion This study yields valuable information to more effectively respond to emerging methamphetamine epidemics in South Africa and other low- and middle-income countries. Interventions to increase uptake of evidence-based services must actively seek out drug users and build motivation for treatment, and offer continuing care services to prevent relapse. Community education campaigns are also needed. PMID:25977205

  12. Next-generation seismic experiments - II: wide-angle, multi-azimuth, 3-D, full-waveform inversion of sparse field data

    NASA Astrophysics Data System (ADS)

    Morgan, Joanna; Warner, Michael; Arnoux, Gillean; Hooft, Emilie; Toomey, Douglas; VanderBeek, Brandon; Wilcock, William

    2016-02-01

    3-D full-waveform inversion (FWI) is an advanced seismic imaging technique that has been widely adopted by the oil and gas industry to obtain high-fidelity models of P-wave velocity that lead to improvements in migrated images of the reservoir. Most industrial applications of 3-D FWI model the acoustic wavefield, often account for the kinematic effect of anisotropy, and focus on matching the low-frequency component of the early arriving refractions that are most sensitive to P-wave velocity structure. Here, we have adopted the same approach in an application of 3-D acoustic, anisotropic FWI to an ocean-bottom-seismometer (OBS) field data set acquired across the Endeavour oceanic spreading centre in the northeastern Pacific. Starting models for P-wave velocity and anisotropy were obtained from traveltime tomography; during FWI, velocity is updated whereas anisotropy is kept fixed. We demonstrate that, for the Endeavour field data set, 3-D FWI is able to recover fine-scale velocity structure with a resolution that is 2-4 times better than conventional traveltime tomography. Quality assurance procedures have been employed to monitor each step of the workflow; these are time consuming but critical to the development of a successful inversion strategy. Finally, a suite of checkerboard tests has been performed which shows that the full potential resolution of FWI can be obtained if we acquire a 3-D survey with a slightly denser shot and receiver spacing than is usual for an academic experiment. We anticipate that this exciting development will encourage future seismic investigations of earth science targets that would benefit from the superior resolution offered by 3-D FWI.

  13. Drill-rig noise suppression using the Karhunen-Loéve transform for seismic-while-drilling experiment at Brukunga, South Australia

    NASA Astrophysics Data System (ADS)

    Sun, Baichun; Bóna, Andrej; Zhou, Binzhong; King, Andrew; Dupuis, Christian; Kepic, Anton

    2016-02-01

    Diamond-impregnated drill bits are known to be low energy vibration seismic sources. With the strong interference from the drill rig, it is difficult to obtain the drill-bit wavefield with a surface receiver array. To overcome the challenge of surface wave interference generated from the rig for seismic-while-drilling (SWD), we need to separate the rig- and bit-generated signals. To this end, we apply two wavefield separation methods, the Karhunen-Loéve (KL) transform and the f - k filter, and compare their performance. The applicability of these methods is based on the drill rig and drill bit having different spatial positions. While the drill-bit spatial position changes during the process of drilling, the drill rig remains stationary. This results in the source wavefields from the drill rig and the drill-bit having different characteristics, and allows us to separate and extract the drill-bit signal. We use a synthetic model to compare the KL transform and f - k filter. Both techniques are robust when the noise wavefield has consistent amplitude moveout. However, for changing amplitudes, such as the rig noise, which has an unrepeatable wavefield due to power amplitude variation, we show that the KL transform performs better in such situations. We also show the results of signal analysis of the SWD experiment data acquired from Brukunga, South Australia. We demonstrate the feasibility of the KL transform in separating the coherent noises from the stationary drill rig in a hard rock drilling environment, particularly emphasising the suppression of the surface and direct waves from the rig. The results show that drill-rig noise can be effectively suppressed in the correlation domain.

  14. How can community health programmes build enabling environments for transformative communication? Experiences from India and South Africa.

    PubMed

    Campbell, Catherine; Cornish, Flora

    2012-05-01

    Much research has examined how to empower the poor to articulate demands for health-enabling living conditions. Less is known about creating receptive social environments where the powerful heed the voices of the poor. We explore the potential for 'transformative communication' between the poor and the powerful, through comparing two well-documented case studies of HIV/AIDS management. The Entabeni Project in South Africa sought to empower impoverished women to deliver home-based nursing to people with AIDS. It successfully provided short-term welfare, but did not achieve local leadership or sustainability. The Sonagachi Project in India, an HIV-prevention programme targeting female sex workers, became locally led and sustainable. We highlight the strategies through which Sonagachi, but not Entabeni, altered the material, symbolic and relational contexts of participants' lives, enabling transformative communication and opportunities for sexual health-enabling social change.

  15. Impediments to media communication of social change in family planning and reproductive health: experiences from East Africa.

    PubMed

    Kagurusi, Patrick T

    2013-09-01

    The media has been employed to increase uptake of Family Planning through behaviour change communication (BCC). Understanding the barriers encountered in effectively undertaking this function would increase the strategy's effectiveness. Sixty journalists from East Africa participated in trainings to enhance their BCC skills for Family Planning in which a qualitative study was nested to identify barriers to effective Family Planning BCC in the region's media. The barriers were observed to be insufficient BCC skills, journalists' conflict of interest, interests of media houses, inaccessible sources of family planning information, editorial ideologies and absence of commercially beneficial demand. Coupled with the historical ideologies of the media in the region, the observed barriers have precipitated ineffective family planning BCC in the regions media. Effective BCC for family planning in the regions media requires capacity building among practitioners and alignment of the concept to the media's and consumers' aspirations.

  16. [Ebola virus disease in West Africa and Germany : clinical presentation, management and practical experience with medevacuated patients in Germany].

    PubMed

    Schmiedel, Stefan; Kreuels, B

    2015-07-01

    Ebolaviruses are the causative pathogens of a severe form of viral haemorrhagic fever with cytokine induced shock and multi-organ failure and a high case fatality rate in humans (50-90 %, more than 70 % in the beginning of the current outbreak), designated Ebola haemorrhagic fever or Ebola virus disease (EVD). Ebola is endemic in regions of Central and West Africa. Ebolavirus Zaire (EBOV) is the most aggressive Ebola virus species and is causing the current epidemic. Currently, beginning in late 2013, an unprecedented epidemic with several thousand cases and deaths (as per WHO report 24.12.2014: 19,497 documented cases, 7588 death, 2352 cases in past 3 weeks) is unfolding in Guinea, Liberia and Sierra Leone, and spreading to other countries in Africa, Europe and the USA, where isolated cases have occurred. Ebola transmission occurs exclusively through direct contact with body fluids through mucosal surfaces, skin abrasions, or by parenteral introduction-an aerolised transmission has not been reported so far. Infections in healthcare personnel have not only occurred after needle stick injuries but also after unsafe doffing procedures of personal protection equipment (PPE). The protection of healthcare personnel caring for Ebola patients, therefore, requires that high standards in the use of PPE are mandatory. In high-income countries the management and treatment of EVD patients in specialized centres is recommended. Using negative pressure rooms and positive pressure suits may provide additional safety. Due to the high degree of training and monitoring needed to prevent occupational risks, treatment of EVD patients in non-specialized hospitals should not take place.

  17. Underthrusting of Tarim beneath the Tien Shan and deep structure of their junction zone: Main results of seismic experiment along MANAS Profile Kashgar-Song-Köl

    NASA Astrophysics Data System (ADS)

    Makarov, V. I.; Alekseev, D. V.; Batalev, V. Yu.; Bataleva, E. A.; Belyaev, I. V.; Bragin, V. D.; Dergunov, N. T.; Efimova, N. N.; Leonov, M. G.; Munirova, L. M.; Pavlenkin, A. D.; Roecker, S.; Roslov, Yu. V.; Rybin, A. K.; Shchelochkov, G. G.

    2010-03-01

    The results of reflection CMP seismic profiling of the Central Tien Shan in the meridional tract 75-76° E from Lake Song-Köl in Kyrgyzstan to the town of Kashgar in China are considered. The seismic section demonstrating complex heterogeneous structure of the Earth’s crust and reflecting its near-horizontal delamination with vertical and inclined zones of compositional and structural differentiation was constructed from processing of initial data of reflection CMP seismic profiling, earthquake converted-wave method (ECWM), and seismic tomography. The most important is the large zone of underthrusting of the Tarim Massif beneath the Tien Shan.

  18. Developing Ethical Practices for Public Health Research Data Sharing in South Africa: The Views and Experiences From a Diverse Sample of Research Stakeholders.

    PubMed

    Denny, Spencer G; Silaigwana, Blessing; Wassenaar, Douglas; Bull, Susan; Parker, Michael

    2015-07-01

    The abundance of South African clinical and public health research data has the potential to unlock important and valuable future advances in biomedical science. Amid increasing calls for more effective sharing of individual-level data, commitment to promote access to research data is evident within South Africa's public research sector, but national guidance and regulation are absent. This qualitative study examined the perceptions, experiences and concerns of 32 research stakeholders about data-sharing practices. There was consensus about the utility of data sharing in publicly funded health research. However, disparate views emerged about the possible harms and benefits of sharing data and how these should be weighed. The relative dearth of policies governing data-sharing practices needs to be addressed and a framework of support developed that incentivizes data-sharing practices for researchers that are both ethical and effective.

  19. Seismic Discrimination

    DTIC Science & Technology

    1975-12-31

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

  20. Seismic Tomography.

    ERIC Educational Resources Information Center

    Anderson, Don L.; Dziewonski, Adam M.

    1984-01-01

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

  1. Seismic 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

  2. Report for borehole explosion data acquired in the 1999 Los Angeles Region Seismic Experiment (LARSE II), Southern California: Part I, description of the survey

    USGS Publications Warehouse

    Fuis, Gary S.; Murphy, Janice M.; Okaya, David A.; Clayton, Robert W.; Davis, Paul M.; Thygesen, Kristina; Baher, Shirley A.; Ryberg, Trond; Benthien, Mark L.; Simila, Gerry; Perron, J. Taylor; Yong, Alan K.; Reusser, Luke; Lutter, William J.; Kaip, Galen; Fort, Michael D.; Asudeh, Isa; Sell, Russell; Van Schaack, John R.; Criley, Edward E.; Kaderabek, Ronald; Kohler, Will M.; Magnuski, Nickolas H.

    2001-01-01

    The Los Angeles Region Seismic Experiment (LARSE) is a joint project of the U.S. Geological Survey (USGS) and the Southern California Earthquake Center (SCEC). The purpose of this project is to produce seismic images of the subsurface of the Los Angeles region down to the depths at which earthquakes occur, and deeper, in order to remedy a deficit in our knowledge of the deep structure of this region. This deficit in knowledge has persisted despite over a century of oil exploration and nearly 70 years of recording earthquakes in southern California. Understanding the deep crustal structure and tectonics of southern California is important to earthquake hazard assessment. Specific imaging targets of LARSE include (a) faults, especially blind thrust faults, which cannot be reliably detected any other way; and (b) the depths and configurations of sedimentary basins. Imaging of faults is important in both earthquake hazard assessment but also in modeling earthquake occurrence. Earthquake occurrence cannot be understood unless the earthquake-producing "machinery" (tectonics) is known (Fuis and others, 2001). Imaging the depths and configurations of sedimentary basins is important because earthquake shaking at the surface is enhanced by basin depth and by the presence of sharp basin edges (Wald and Graves, 1998, Working Group on California Earthquake Probabilities, 1995; Field and others, 2001). (Sedimentary basins are large former valleys now filled with sediment eroded from nearby mountains.) Sedimentary basins in the Los Angeles region that have been investigated by LARSE include the Los Angeles, San Gabriel Valley, San Fernando Valley, and Santa Clarita Valley basins. The seismic imaging surveys of LARSE include recording of earthquakes (both local and distant earthquakes) along several corridors (or transects) through the Los Angeles region and also recording of man-made sources along these same corridors. Man-made sources have included airguns offshore and borehole

  3. Social solidarity and willingness to tolerate risk- and income-related cross-subsidies within health insurance: experiences from Ghana, Tanzania and South Africa.

    PubMed

    Goudge, Jane; Akazili, James; Ataguba, John; Kuwawenaruwa, August; Borghi, Josephine; Harris, Bronwyn; Mills, Anne

    2012-03-01

    The importance of ill-health in perpetuating poverty is well recognized. In order to prevent the damaging downward spiral of poverty and illness, there is a need for a greater level of social protection, with greater cross-subsidization between the poor and wealthy, and the healthy and those with ill-health. The aim of this paper is to examine individual preferences for willingness to pre-pay for health care and willingness to cross-subsidize the sick and the poor in Ghana, South Africa and Tanzania. Household surveys in the three countries elicited views on cross-subsidization within health care financing. The paper examines how these preferences varied by socio-economic status, other respondent characteristics, and the extent and type of experience of health insurance in the light of country context. In South Africa and Ghana, 62% and 55% of total respondents, respectively, were in favour of a progressive financing system in which richer groups would pay a higher proportion of income than poorer groups, rather than a system where individuals pay the same proportion of income irrespective of their wealth (proportional). In Tanzania, 45% of the total sample were willing to pay for the health care of the poor. However, in all three countries, a progressive system was favoured by a smaller proportion of the most well off than of less well off groups. Solidarity has been considered to be a collective property of a specific socio-political culture, based on shared expectations and developed as part of a communal, historical learning process. The three countries had different experiences of health insurance and this may have contributed to the above differences in expressed willingness to pay between countries. Building and 'living with' institutions that provide affordable universal coverage is likely to be an essential part of the learning process which supports the development of social solidarity.

  4. Initial constraints on crustal structure across the Suwanee Suture and South Georgia Basin from the SUGAR seismic refraction experiment

    NASA Astrophysics Data System (ADS)

    Shillington, D. J.; Lizarralde, D.; Harder, S. H.

    2014-12-01

    Some of the most important unresolved questions in plate tectonics concern the formation and rupture of continents. How does the accretion of terranes contribute to the construction of continental lithosphere, and what processes enable continental lithosphere to rupture? The South Georgia Basin was at the center of the most recent sequence of continental collision and rifting events to shape eastern North America. It is the largest of the failed Mesozoic rift basins that formed during the breakup of Pangea. It straddles the Suwannee Suture, the only well-defined remnant of the Alleghenian suture that joined North America and Gondwana, forming Pangea. The South Georgia Basin also lies at the center of the Central Atlantic Magmatic Province (CAMP). Here we present initial results from the first phase of the SUwanee Suture and GA Rift basin (SUGAR) project, an active-source seismic refraction project to image the crustal structure across these features. During March 2014, we acquired data along a ~325-km-long, NW-SE oriented profile that crossed the Suwanne Suture and western part of South Georgia Basin, extending from north of Columbus, GA to northernmost Florida east of Jasper, FL. The profile was densely instrumented with single-channel RekTek 125A seismometers ("Texans") spaced at ~250 m and deployed along state and country roads, yielding a total of 1193 seismometers along the profile. Thirty-three students and young scientists were involved in the deployment and recovery. The sources were 100 to 1800 lb shots spaced at ~20-50 km. The data are of exceptionally high quality. On nearly all shots, we observe arrivals out to the largest shot-receiver offsets. Within the basin, refractions through the sedimentary section with apparent velocities of ~3-4 km/s are observed to maximum offsets of 7 km. Crustal refractions are observed at a wide-range of offsets with apparent velocities increasing from ~5.5 km/s to as high as ~7.25 km/s. At offsets greater than 150-180 km

  5. Extension and magmatism across the Suwanee Suture and South Georgia Basin from the SUGAR seismic refraction experiment

    NASA Astrophysics Data System (ADS)

    Shillington, D. J.; Lizarralde, D.; Harder, S. H.; Marzen, R.; Kaip, G.; Accardo, N. J.; Gibson, J. C.; Nauer, A.

    2015-12-01

    The South Georgia Basin was at the center of the most recent sequence of continental collision and rifting events to shape eastern North America. It is the largest of the failed Mesozoic rift basins that formed during the breakup of Pangea, and it straddles the Suwannee Suture, the only well-defined remnant of the Alleghenian suture that joined North America and Gondwana. The South Georgia Basin also lies at the center of the Central Atlantic Magmatic Province (CAMP). It is thus an excellent location to examine the importance of magmatism and pre-existing structures on continental extension. Here we present preliminary results from the SUwanee Suture and GA Rift basin (SUGAR) project, an active-source seismic refraction project to image the crustal structure across these features. In March 2014, we acquired data along SUGAR Line 1, a ~325-km-long, NW-SE oriented profile that crossed the Suwanee Suture and western part of South Georgia Basin. The profile was densely instrumented with 1193 single-channel RekTek 125A seismographs ("Texans") spaced at ~250 m. The sources were 100 to 1800 lb shots spaced at ~20-50 km. In August 2015, we will acquire data along SUGAR Lines 2 and 3. SUGAR Line 2 is a ~450-km-long profile spanning the eastern part of the South Georgia Basin and two possible locations for the Suwanee Suture. We will deploy 1983 "Texans" spaced at 250 m and detonate seventeen 400 to 1600 lb shots spaced at ~16-50 km. SUGAR Line 3 targets the Brunswick magnetic anomaly; we plan to instrument a 100-km-long profile with 700 Texans spaced at 150 m and eleven 200 lb shots spaced at ~10 km. Over 68 students participated in field work for SUGAR. Preliminary models of SUGAR Line 1 indicate that the crust thins to ~33 km beneath the South Georgia Basin. Anomalously high lower crustal velocities occur beneath the basin in the area of the greatest crustal thinning and may represent mafic intrusions from CAMP/synrift magmatism. We will present initial velocity models of

  6. The Farmer Life School: experience from an innovative approach to HIV education among farmers in South Africa.

    PubMed

    Swaans, K; Broerse, J E W; Salomon, M; Mudhara, M; Mweli, M; Bunders, J F G

    2008-07-01

    The Farmer Life School (FLS) is an innovative approach to integrating HIV education into life skills and technical training for farmers. This study aims to gain insight into the strengths and weaknesses of this relatively new approach, through the implementation of an adapted version in South Africa. The results are presented of a pilot with three groups of community gardeners, predominantly women, attending weekly sessions. Impact was assessed in terms of three key elements: participation, learning, and empowerment. Data were collected through extensive session reports, follow-up interviews, and reflection exercises with facilitators and participating groups and individuals. The results suggest that a group-based discovery learning approach such as the FLS has great potential to improve food security and wellbeing, while allowing participants to explore issues around HIV/AIDS. However, the analysis also shows that HIV/AIDS-related illness and death, and the factors that drive the epidemic and its impact, undermine farmers' ability to participate, the safety and trust required for learning, and the empowerment process. Participatory approaches such as the FLS require a thorough understanding of and adaptation to the context.

  7. Work schedule and client characteristics associated with workplace violence experience among nurses and midwives in sub-Saharan Africa.

    PubMed

    El Ghaziri, Mazen; Zhu, Shijun; Lipscomb, Jane; Smith, Barbara A

    2014-01-01

    Violence against health care workers perpetrated by clients and/or their friends and family (Type II) is a growing problem that can severely impact health care delivery. We examined the prevalence of Type II workplace violence among nurses and midwives in sub-Saharan Africa and its association with work status, schedule, and client characteristics. Nurses and midwives (n = 712) completed an anonymous survey while attending nursing meetings. Generalized estimating equation models, accounting for clustering within residing countries, were employed. Participants who were exposed to risky client characteristics (aOR = 1.39-1.78, p < .001), and those who worked more than 40 hours a week were more likely to have experienced Type II workplace violence (aOR = 1.72-2.15, p < .05). Findings will inform policy and organization level interventions needed to minimize nurses' and midwives' exposure to Type II workplace violence by identifying risky clients and addressing long work hours.

  8. Experiences of alcohol consumption and taking antiretroviral medication among men living with HIV in Tshwane, South Africa.

    PubMed

    Nkosi, Sebenzile; Rich, Eileen P; Kekwaletswe, Connie T; Morojele, Neo K

    2016-12-01

    Hazardous alcohol consumption may compromise optimal antiretroviral therapy (ART) adherence among patients. Adoption of hegemonic notions of masculinity may encourage health-risk behaviours, such as alcohol consumption, and discourage health-enhancing behaviours, such as ART adherence among men. This study aimed to explore linkages between masculinity, alcohol consumption, and taking ART medication among male ART recipients in South Africa. Male facilitators conducted five focus group discussions with 27 black male ART recipients aged between 28 and 65 years at five ART clinics. Eligibility criteria were: 18 years or older, at least three months on ART, and alcohol consumption in the past three months. Data were analysed inductively using thematic content analysis. The men demonstrated a masculinity that fostered commitment to taking ART. However, normative notions of masculinity in the men's social circles often compromised their timeous taking of medication. Fears of alcohol-ART interactions often led to intentional non-adherence to ART when drinking. Finally, healthcare provider-patient power dynamics seemed to prevent the men from discussing their challenges regarding alcohol use and ART adherence with their healthcare providers. Interventions that focus on addressing harmful hegemonic notions of masculinity among men are needed in community settings such as drinking establishments where men tend to socialise. Patient-centred approaches which enhance men's sense of involvement in their treatment are needed in healthcare settings.

  9. Analysis of the seismic signals generated by controlled single-block rockfalls on soft clay shales sediments: the Rioux Bourdoux slope experiment (French Alps).

    NASA Astrophysics Data System (ADS)

    Hibert, Clément; Provost, Floriane; Malet, Jean-Philippe; Bourrier, Franck; Berger, Frédéric; Bornemann, Pierrick; Borgniet, Laurent; Tardif, Pascal; Mermin, Eric

    2016-04-01

    Understanding the dynamics of rockfalls is critical to mitigate the associated hazards but is made very difficult by the nature of these natural disasters that makes them hard to observe directly. Recent advances in seismology allow to determine the dynamics of the largest landslides on Earth from the very low-frequency seismic waves they generate. However, the vast majority of rockfalls that occur worldwide are too small to generate such low-frequency seismic waves and thus these methods cannot be used to reconstruct their dynamics. However, if seismic sensors are close enough, these events will generate high-frequency seismic signals. Unfortunately we cannot yet use these high-frequency seismic records to infer parameters synthetizing the rockfall dynamics as the source of these waves is not well understood. One of the first steps towards understanding the physical processes involved in the generation of high-frequency seismic waves by rockfalls is to study the link between the dynamics of a single block propagating along a well-known path and the features of the seismic signal generated. We conducted controlled releases of single blocks of limestones in a gully of clay-shales (e.g. black marls) in the Rioux Bourdoux torrent (French Alps). 28 blocks, with masses ranging from 76 kg to 472 kg, were released. A monitoring network combining high-velocity cameras, a broadband seismometer and an array of 4 high-frequency seismometers was deployed near the release area and along the travel path. The high-velocity cameras allow to reconstruct the 3D trajectories of the blocks, to estimate their velocities and the position of the different impacts with the slope surface. These data are compared to the seismic signals recorded. As the distance between the block and the seismic sensors at the time of each impact is known, we can determine the associated seismic signal amplitude corrected from propagation and attenuation effects. We can further compare the velocity, the

  10. Engaging media in communicating research on sexual and reproductive health and rights in sub-Saharan Africa: experiences and lessons learned

    PubMed Central

    2011-01-01

    Background The mass media have excellent potential to promote good sexual and reproductive health outcomes, but around the world, media often fail to prioritize sexual and reproductive health and rights issues or report them in an accurate manner. In sub-Saharan Africa media coverage of reproductive health issues is poor due to the weak capacity and motivation for reporting these issues by media practitioners. This paper describes the experiences of the African Population and Health Research Center and its partners in cultivating the interest and building the capacity of the media in evidence-based reporting of reproductive health issues in sub-Saharan Africa. Methods The paper utilizes a case study approach based primarily on the personal experiences and reflections of the authors (who played a central role in developing and implementing the Center’s communication and policy engagement strategies), a survey that the Center carried out with science journalists in Kenya, and literature review. Results The African Population and Health Research Center’s media strategy evolved over the years, moving beyond conventional ways of communicating research through the media via news releases and newspaper stories, to varying approaches that sought to inspire and build the capacity of journalists to do evidence-based reporting of reproductive health issues. Specifically, the approach included 1) enhancing journalists’ interest in and motivation for reporting on reproductive health issues through training and competitive grants for outstanding reporting ; 2) building the capacity of journalists to report reproductive health research and the capacity of reproductive health researchers to communicate their research to media through training for both parties and providing technical assistance to journalists in obtaining and interpreting evidence; and 3) establishing and maintaining trust and mutual relationships between journalists and researchers through regular informal

  11. Seismic Discrimination

    DTIC Science & Technology

    1977-03-31

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

  12. Seismic testing

    SciTech Connect

    Knott, S.

    1981-10-01

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

  13. Assessing participatory practices in community-based natural resource management: experiences in community engagement from southern Africa.

    PubMed

    Dyer, J; Stringer, L C; Dougill, A J; Leventon, J; Nshimbi, M; Chama, F; Kafwifwi, A; Muledi, J I; Kaumbu, J-M K; Falcao, M; Muhorro, S; Munyemba, F; Kalaba, G M; Syampungani, S

    2014-05-01

    The emphasis on participatory environmental management within international development has started to overcome critiques of traditional exclusionary environmental policy, aligning with shifts towards decentralisation and community empowerment. However, questions are raised regarding the extent to which participation in project design and implementation is meaningful and really engages communities in the process. Calls have been made for further local-level (project and community-scale) research to identify practices that can increase the likelihood of meaningful community engagement within externally initiated projects. This paper presents data from three community-based natural resource management (CBNRM) project case studies from southern Africa, which promote Joint Forest Management (JFM), tree planting for carbon and conservation agriculture. Data collection was carried out through semi-structured interviews with key stakeholders, community-level meetings, focus groups and interviews. We find that an important first step for a meaningful community engagement process is to define 'community' in an open and participatory manner. Two-way communication at all stages of the community engagement process is shown to be critical, and charismatic leadership based on mutual respect and clarity of roles and responsibilities is vital to improve the likelihood of participants developing understanding of project aims and philosophy. This can lead to successful project outcomes through community ownership of the project goals and empowerment in project implementation. Specific engagement methods are found to be less important than the contextual and environmental factors associated with each project, but consideration should be given to identifying appropriate methods to ensure community representation. Our findings extend current thinking on the evaluation of participation by making explicit links between the community engagement process and project outcomes, and by

  14. 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

  15. Salt Tectonics of the Abenaki Graben and Central Sable Subbasin: Insights from Regional Seismic Interpretation and Four-Dimensional Scaled Physical Experiments

    NASA Astrophysics Data System (ADS)

    Campbell, Clarke

    The tectono-stratigraphic evolution of the Abenaki graben and central Sable Subbasin of the north-central Scotian margin has been highly influenced by salt deformation. Shimeld (2004) has identified five salt subprovinces defined by varying salt structural styles across the margin. Although it has been hypothesized these varying structural styles are the result of complex salt basin morphologies and variable Mesozoic post-rift sedimentation patterns, there is still a lack of understanding of how these first order controlling factors specifically controlled the tectono-stratigraphic evolution across the margin. Disappointing petroleum exploration results from the last round of deepwater drilling supports the further need to investigate how variable salt basin morphologies, and depositional rates and patterns controlled salt deformation as well as the evolution of the margin. The purpose of this project is to integrate regional 2D seismic reflection data including the ION-GXT NovaSPAN dataset, with 4D scaled physical experiments to better understand the tectono-stratigraphic evolution of the Abenaki Graben and central Sable Subbasin. The study area is located in Shimeld's salt Subprovince III that comprises an extensive salt tongue-canopy system that has spread upwards of 80 km on the secondary detachment level. Seismic interpretation indicates an original salt basin characterized by a landward tapering wedge representing the Abenaki Graben, an intermediate high referred to as the North Sable High (NSH), and a symmetric graben with basin step representing the Sable Subbasin. The geometry of the salt basin floor is composed of rifted basement blocks and syn-rift fill that was originally been infilled with upwards of 2 km of Argo salt. Scaled 4D physical experiments simulating the study area indicate the presence of 4 kinematic domains from the shelf to slope including a: (1) Salt Weld and Pillow, (2) Normal Fault and Reactive Diapir, (3) Passive Diapir and Expulsion

  16. Upper crustal structure from the Santa Monica Mountains to the Sierra Nevada, Southern California: Tomographic results from the Los Angeles Regional Seismic Experiment, Phase II (LARSE II)

    USGS Publications Warehouse

    Lutter, W.J.; Fuis, G.S.; Ryberg, T.; Okaya, D.A.; Clayton, R.W.; Davis, P.M.; Prodehl, C.; Murphy, J.M.; Langenheim, V.E.; Benthien, M.L.; Godfrey, N.J.; Christensen, N.I.; Thygesen, K.; Thurber, C.H.; Simila, G.; Keller, Gordon R.

    2004-01-01

    In 1999, the U.S. Geological Survey and the Southern California Earthquake Center (SCEC) collected refraction and low-fold reflection data along a 150-km-long corridor extending from the Santa Monica Mountains northward to the Sierra Nevada. This profile was part of the second phase of the Los Angeles Region Seismic Experiment (LARSE II). Chief imaging targets included sedimentary basins beneath the San Fernando and Santa Clarita Valleys and the deep structure of major faults along the transect, including causative faults for the 1971 M 6.7 San Fernando and 1994 M 6.7 Northridge earthquakes, the San Gabriel Fault, and the San Andreas Fault. Tomographic modeling of first arrivals using the methods of Hole (1992) and Lutter et al. (1999) produces velocity models that are similar to each other and are well resolved to depths of 5-7.5 km. These models, together with oil-test well data and independent forward modeling of LARSE II refraction data, suggest that regions of relatively low velocity and high velocity gradient in the San Fernando Valley and the northern Santa Clarita Valley (north of the San Gabriel Fault) correspond to Cenozoic sedimentary basin fill and reach maximum depths along the profile of ???4.3 km and >3 km , respectively. The Antelope Valley, within the western Mojave Desert, is also underlain by low-velocity, high-gradient sedimentary fill to an interpreted maximum depth of ???2.4 km. Below depths of ???2 km, velocities of basement rocks in the Santa Monica Mountains and the central Transverse Ranges vary between 5.5 and 6.0 km/sec, but in the Mojave Desert, basement rocks vary in velocity between 5.25 and 6.25 km/sec. The San Andreas Fault separates differing velocity structures of the central Transverse Ranges and Mojave Desert. A weak low-velocity zone is centered approximately on the north-dipping aftershock zone of the 1971 San Fernando earthquake and possibly along the deep projection of the San Gabriel Fault. Modeling of gravity data, using

  17. A regional and multi-faceted approach to postgraduate water education - the WaterNet experience in Southern Africa

    NASA Astrophysics Data System (ADS)

    Jonker, L.; van der Zaag, P.; Gumbo, B.; Rockström, J.; Love, D.; Savenije, H. H. G.

    2012-11-01

    This paper reports the experience of a regional network of academic departments involved in water education that started as a project and evolved, over a period of 12 yr, into an independent network organisation. The paper pursues three objectives. First, it argues that it makes good sense to organise postgraduate education and research on water resources on a regional scale and presents the WaterNet experience as an example that a regional approach can work. Second, it presents preliminary findings and conclusions that the regional approach presented by WaterNet did make a contribution to the capacity needs of the region both in terms of management and research capacity. Third, it draws two generalised lessons from the WaterNet experience. Lesson one pertains to the importance of legitimate ownership and an accountability structure for network effectiveness. Lesson two is related to the financial and intellectual resources required to jointly developing educational programmes through shared experience.

  18. Clinical Outcomes and Women’s Experiences before and after the Introduction of Mifepristone into Second-Trimester Medical Abortion Services in South Africa

    PubMed Central

    Harries, Jane; Malaba, Thokozile; Myer, Landon; Patel, Malika; Petro, Gregory; Grossman, Daniel

    2016-01-01

    Objective To document clinical outcomes and women’s experiences following the introduction of mifepristone into South African public sector second-trimester medical abortion services, and compare with historic cohorts receiving misoprostol-only. Methods Repeated cross-sectional observational studies documented service delivery and experiences of women undergoing second-trimester medical abortion in public sector hospitals in the Western Cape, South Africa. Women recruited to the study in 2008 (n = 84) and 2010 (n = 58) received misoprostol only. Those recruited in 2014 (n = 208) received mifepristone and misoprostol. Consenting women were interviewed during hospitalization by study fieldworkers with respect to socio-demographic information, reproductive history, and their experiences with the abortion. Clinical details were extracted from medical charts following discharge. Telephone follow-up interviews to record delayed complications were conducted 2–4 weeks after discharge for the 2014 cohort. Results The 2014 cohort received 200 mg mifepristone, which was self-administered 24–48 hours prior to admission. For all cohorts, following hospital admission, initial misoprostol doses were generally administered vaginally: 800 mcg in the 2014 cohort and 600 mcg in the earlier cohorts. Women received subsequent doses of misoprostol 400 mcg orally every 3–4 hours until fetal expulsion. Thereafter, uterine evacuation of placental tissue was performed as needed. With one exception, all women in all cohorts expelled the fetus. Median time-to-fetal expulsion was reduced to 8.0 hours from 14.5 hours (p<0.001) in the mifepristone compared to the 2010 misoprostol-only cohort (time of fetal expulsion was not recorded in 2008). Uterine evacuation of placental tissue using curettage or vacuum aspiration was more often performed (76% vs. 58%, p<0.001) for those receiving mifepristone; major complication rates were unchanged. Hospitalization duration and extreme pain levels

  19. The boundary conditions for simulations of a shake-table experiment on the seismic response of 3D slope

    NASA Astrophysics Data System (ADS)

    Tang, Liang; Cong, Shengyi; Ling, Xianzhang; Ju, Nengpan

    2017-01-01

    Boundary conditions can significantly affect a slope's behavior under strong earthquakes. To evaluate the importance of boundary conditions for finite element (FE) simulations of a shake-table experiment on the slope response, a validated three-dimensional (3D) nonlinear FE model is presented, and the numerical and experimental results are compared. For that purpose, the robust graphical user-interface "SlopeSAR", based on the open-source computational platform OpenSees, is employed, which simplifies the effort-intensive pre- and post-processing phases. The mesh resolution effect is also addressed. A parametric study is performed to evaluate the influence of boundary conditions on the FE model involving the boundary extent and three types of boundary conditions at the end faces. Generally, variations in the boundary extent produce inconsistent slope deformations. For the two end faces, fixing the y-direction displacement is not appropriate to simulate the shake-table experiment, in which the end walls are rigid and rough. In addition, the influence of the length of the 3D slope's top face and the width of the slope play an important role in the difference between two types of boundary conditions at the end faces (fixing the y-direction displacement and fixing the ( y, z) direction displacement). Overall, this study highlights that the assessment of a comparison between a simulation and an experimental result should be performed with due consideration to the effect of the boundary conditions.

  20. Increasing Use of Postpartum Family Planning and the Postpartum IUD: Early Experiences in West and Central Africa

    PubMed Central

    Pleah, Tsigue; Hyjazi, Yolande; Austin, Suzanne; Diallo, Abdoulaye; Dao, Blami; Waxman, Rachel; Karna, Priya

    2016-01-01

    ABSTRACT A global resurgence of interest in the intrauterine device (IUD) as an effective long-acting reversible contraceptive and in improving access to a wide range of contraceptive methods, as well as an emphasis on encouraging women to give birth in health care facilities, has led programs to introduce postpartum IUD (PPIUD) services into postpartum family planning (PPFP) programs. We describe strategic, organizational, and technical elements that contributed to early successes of a regional initiative in West and Central Africa to train antenatal, maternity, and postnatal care providers in PPFP counseling for the full range of available methods and in PPIUD service delivery. In November 2013, the initiative provided competency-based training in Guinea for providers from the main public teaching hospital in 5 selected countries (Benin, Chad, Côte d’Ivoire, Niger, and Senegal) with no prior PPFP counseling or PPIUD capacity. The training was followed by a transfer-of-learning visit and monitoring to support the trained providers. One additional country, Togo, replicated the initiative’s model in 2014. Although nascent, this initiative has introduced high-quality PPFP and PPIUD services to the region, where less than 1% of married women of reproductive age use the IUD. In total, 21 providers were trained in PPFP counseling, 18 of whom were also trained in PPIUD insertion. From 2014 to 2015, more than 15,000 women were counseled about PPFP, and 2,269 women chose and received the PPIUD in Benin, Côte d’Ivoire, Niger, Senegal, and Togo. (Introduction of PPIUD services in Chad has been delayed.) South–South collaboration has been central to the initiative’s accomplishments: Guinea’s clinical centers of excellence and qualified trainers provided a culturally resonant example of a PPFP/PPIUD program, and trainings are creating a network of regional trainers to facilitate expansion. Two of the selected countries (Benin and Niger) have expanded their PPFP

  1. Deformation experiments under conditions of the blueschist- to eclogite-facies transition: implications for the upper Wadati-Benioff plane of seismicity

    NASA Astrophysics Data System (ADS)

    Incel, S.; Schubnel, A.; Hilairet, N.; Labrousse, L.; Chopin, C.; Renner, J.; Wang, Y.; Ferrand, T. P.; John, T.

    2015-12-01

    Blueschist samples were experimented on a Griggs, a piston-cylinder (PC) and a D-DIA apparatus. Starting materials were sieved powders (<30 μm) from a natural sample collected on Alpine Corsica which initially contained approx. 60 % glaucophane and 40 % lawsonite. After mineral separation, we produced powders with a high (80 % glaucophane, 20 % lawsonite) and a low (30 % glaucophane, 70 % lawsonite) glaucophane content. Samples of cold-pressed powders of the two compositions were deformed in the Griggs and D-DIA apparatus at low temperatures (<550 °C) at which lawsonite is stable but glaucophane should decompose into jadeite and talc, and at high temperatures (up to 850 °C) at which lawsonite dehydrates. Powders were also isostatically annealed at comparable experimental conditions in the PC-apparatus to provide a microstructural reference. The use of synchrotron X-rays during the D-DIA experiments enables us to follow the strain evolution (radiography) while deforming the sample, but also to monitor phase changes in-situ using X-ray diffraction. We also monitored acoustic emissions (AE). Depending on the sample mineralogy and the applied pressure, AEs were either observed at low temperature around 380-420 °C or in a range from 610-850 °C. In some samples AEs were triggered in both ranges. Microstructural observations (SEM, Raman, Microprobe, X-ray tomography) on retrieved samples reveal that samples deformed under deviatoric stress exhibit faults almost exclusively, whereas those under hydrostatic conditions do not. Our preliminary interpretation of stress, strain, microstructural and mineralogical evolution during deformation, is that the two temperature ranges of AE activity correspond to transformational faulting due to the glaucophane breakdown into jadeite and talc and lawsonite dehydration. We interpret these micro-earthquakes as possible laboratory analogs of intermediate depth earthquakes occurring within the upper Wadati-Benioff plane of seismicity

  2. Non-Linear Seismic Velocity Estimation from Multiple Waveform Functionals and Formal Assessment of Constraints

    DTIC Science & Technology

    2011-09-01

    for Lithospheric Structure Beneath Asia and North Africa, 27th Seismic Research Review: Ground-Based Nuclear Explosion Monitoring Technologies, LA...Tomography for Lithospheric Structure Beneath the Middle East and North Africa, in Proceedings of the 26th Seismic Research , Review - Trends in Nuclear...dispersion and teleseismic receiver functions: Implications for lithospheric structure of the Arabian Peninsula. J. Geophys. Res., 111(B11311): 10.1029

  3. A little bit of Africa in Brazil: ethnobiology experiences in the field of Afro-Brazilian religions

    PubMed Central

    2014-01-01

    This essay, which is the fourth in the series “Recollections, Reflections, and Revelations: Ethnobiologists and Their First Time in the Field”, is a personal reflection by the researcher on his first field experience with ethnobiology of so called Afro-brazilian cults. The author recounts his feelings and concerns associated with initial fieldwork. PMID:24467714

  4. Chronicling Educator Practices and Experiences in the Context of Democratic Schooling and Quality Education in South Africa

    ERIC Educational Resources Information Center

    Mncube, Vusi; Harber, Clive

    2010-01-01

    An interview-based qualitative study was undertaken to explore the experiences and practices of educators in providing democratic schooling as a way of delivering quality education for learners in schools. The exploration looked at educators' understandings of the concept of democracy in schools, their understanding of the concept quality…

  5. Gender and sexual vulnerability of young women in Africa: experiences of young girls in secondary schools in Uganda.

    PubMed

    Muhanguzi, Florence Kyoheirwe

    2011-06-01

    Sexuality is part and parcel of students' experiences of schooling manifested in personal friendships, relations and social interaction. These encounters constitute sites within which sexual identities are developed, practiced and actively produced through processes of negotiation. Drawing on qualitative research conducted in 14 selected secondary schools in Central and Western Uganda, the study illuminates gendered sexual vulnerability within patterns of social interaction and young girls gendered experiences and negotiation of their sexuality. The study reveals that through social and discursive practices, students construct complex gendered relations of domination and subordination that position boys and girls differently, often creating gender inequalities and sexual vulnerability for those gendered as girls. Girls' vulnerability is characterised by confusing and traumatic experiences fraught with double standards and silences. Typical of these experiences are complex tensions and contradictions surrounding constructions of sexuality that are predicated upon unequal power and gender relations characterised by homophobia, misogyny, control of female sexuality and sexual abuse and exploitation, all which work against girls' expression of sexuality. Gender sensitive sexuality education is identified as a valuable site of intervention to address such vulnerabilities and promote gender equality and equity in society.

  6. Using ICT at an Open Distance Learning (ODL) Institution in South Africa: The Learning Experiences of Students with Visual Impairments

    ERIC Educational Resources Information Center

    Mokiwa, S. A.; Phasha, T. N.

    2012-01-01

    For students with visual impairments, Information and Communication Technology (ICT) has become an important means through which they can learn and access learning materials at various levels of education. However, their learning experiences in using such form of technologies have been rarely documented, thus suggests society's lack of…

  7. A little bit of Africa in Brazil: ethnobiology experiences in the field of Afro-Brazilian religions.

    PubMed

    Albuquerque, Ulysses Paulino

    2014-01-27

    This essay, which is the fourth in the series "Recollections, Reflections, and Revelations: Ethnobiologists and Their First Time in the Field", is a personal reflection by the researcher on his first field experience with ethnobiology of so called Afro-Brazilian cults. The author recounts his feelings and concerns associated with initial fieldwork.

  8. The role of fluid pressure in induced vs. triggered seismicity: insights from rock deformation experiments on carbonates.

    PubMed

    Scuderi, Marco M; Collettini, Cristiano

    2016-04-26

    Fluid overpressure is one of the primary mechanisms for tectonic fault slip, because fluids lubricate the fault and fluid pressure reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction laws, imply that stable sliding is favoured by the increase of pore fluid pressure. Despite this controversy, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, to show that the rate- and state- friction parameters do change with increasing fluid pressure. We tested carbonate gouges from sub hydrostatic to near lithostatic fluid pressure conditions, and show that the friction rate parameter (a - b) evolves from velocity strengthening to velocity neutral behaviour. Furthermore, the critical slip distance, Dc, decreases from about 90 to 10 μm. Our data suggest that fluid overpressure plays an important role in controlling the mode of fault slip. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes.

  9. The role of fluid pressure in induced vs. triggered seismicity: insights from rock deformation experiments on carbonates

    NASA Astrophysics Data System (ADS)

    Scuderi, Marco M.; Collettini, Cristiano

    2016-04-01

    Fluid overpressure is one of the primary mechanisms for tectonic fault slip, because fluids lubricate the fault and fluid pressure reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction laws, imply that stable sliding is favoured by the increase of pore fluid pressure. Despite this controversy, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, to show that the rate- and state- friction parameters do change with increasing fluid pressure. We tested carbonate gouges from sub hydrostatic to near lithostatic fluid pressure conditions, and show that the friction rate parameter (a ‑ b) evolves from velocity strengthening to velocity neutral behaviour. Furthermore, the critical slip distance, Dc, decreases from about 90 to 10 μm. Our data suggest that fluid overpressure plays an important role in controlling the mode of fault slip. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes.

  10. The role of fluid pressure in induced vs. triggered seismicity: insights from rock deformation experiments on carbonates

    PubMed Central

    Scuderi, Marco M.; Collettini, Cristiano

    2016-01-01

    Fluid overpressure is one of the primary mechanisms for tectonic fault slip, because fluids lubricate the fault and fluid pressure reduces the effective normal stress that holds the fault in place. However, current models of earthquake nucleation, based on rate- and state- friction laws, imply that stable sliding is favoured by the increase of pore fluid pressure. Despite this controversy, currently, there are only a few studies on the role of fluid pressure under controlled, laboratory conditions. Here, we use laboratory experiments, to show that the rate- and state- friction parameters do change with increasing fluid pressure. We tested carbonate gouges from sub hydrostatic to near lithostatic fluid pressure conditions, and show that the friction rate parameter (a − b) evolves from velocity strengthening to velocity neutral behaviour. Furthermore, the critical slip distance, Dc, decreases from about 90 to 10 μm. Our data suggest that fluid overpressure plays an important role in controlling the mode of fault slip. Since fault rheology and fault stability parameters change with fluid pressure, we suggest that a comprehensive characterization of these parameters is fundamental for better assessing the role of fluid pressure in natural and human induced earthquakes. PMID:27112408

  11. Evaluating computerized health information systems: hardware, software and human ware: experiences from the Northern Province, South Africa.

    PubMed

    Herbst, K; Littlejohns, P; Rawlinson, J; Collinson, M; Wyatt, J C

    1999-09-01

    Despite enormous investment world-wide in computerized health information systems their overall benefits and costs have rarely been fully assessed. A major new initiative in South Africa provides the opportunity to evaluate the introduction of information technology from a global perspective and assess its impact on public health. The Northern Province is implementing a comprehensive integrated hospital information system (HIS) in all of its 42 hospitals. These include two mental health institutions, eight regional hospitals (two acting as a tertiary complex with teaching responsibilities) and 32 district hospitals. The overall goal of the HIS is to improve the efficiency and effectiveness of health (and welfare) services through the creation and use of information, for clinical, administrative and monitoring purposes. This multi-site implementation is being undertaken as a single project at a cost of R130 million (which represents 2.5 per cent of the health and welfare budget on an annual basis). The implementation process commenced on 1 September 1998 with the introduction of the system into Mankweng Hospital as the pilot site and is to be completed in the year 2001. An evaluation programme has been designed to maximize the likelihood of success of the implementation phase (formative evaluation) as well as providing an overall assessment of its benefits and costs (summative evaluation). The evaluation was designed as a form of health technology assessment; the system will have to prove its worth (in terms of cost-effectiveness) relative to other interventions. This is more extensive than the traditional form of technical assessment of hardware and software functionality, and moves into assessing the day-to-day utility of the system, the clinical and managerial environment in which it is situated (humanware), and ultimately its effects on the quality of patient care and public health. In keeping with new South African legislation the evaluation process sought to

  12. The Seismotectonic Map of Africa

    NASA Astrophysics Data System (ADS)

    Meghraoui, Mustapha

    2015-04-01

    We present the Seismotectonic Map of Africa based on a geological, geophysical and geodetic database including the instrumental seismicity and re-appraisal of large historical events with harmonization and homogenization of earthquake parameters in catalogues. Although the seismotectonic framework and mapping of the African continent is a difficult task, several previous and ongoing projects provide a wealth of data and outstanding results. The database of large and moderate earthquakes in different geological domains includes the coseismic and Quaternary faulting that reveals the complex nature of the active tectonics in Africa. The map also benefits from previous works on local and regional seismotectonic maps that needed to be integrated with the lithospheric and upper mantle structures from tomographic anisotropy and gravity anomaly into a continental framework. The synthesis of earthquake and volcanic studies with the analysis of long-term (late Quaternary) and short-term (last decades and centuries) active deformation observed with geodetic and other approaches presented along with the seismotectonic map serves as a basis for hazard calculations and the reduction of seismic risks. The map may also be very useful in the assessment of seismic hazard and mitigation of earthquake risk for significant infrastructures and their implications in the socio-economic impact in Africa. In addition, the constant population increase and infrastructure growth in the continent that exacerbate the earthquake risk justify the necessity for a continuous updating of the seismotectonic map. The database and related map are prepared in the framework of the IGC Project-601 "Seismotectonics and Seismic Hazards in Africa" of UNESCO-IUGS, funded by the Swedish International Development Agency and UNESCO-Nairobi for a period of 4 years (2011 - 2014), extended to 2016. * Mustapha Meghraoui (Coordinator) EOST - IPG Strasbourg CNRS-UMR 7516 m.meghraoui@unistra.fr corresponding author

  13. 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.

  14. 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.

  15. South Africa's Unintended Experiment in School Choice: How the National Education Policy Act, the South Africa Schools Act and the Employment of Educators Act Create the Enabling Conditions for Quasi-Markets in Schools

    ERIC Educational Resources Information Center

    Woolman, Stuart; Fleisch, Brahm

    2006-01-01

    School choice is often identified with right-leaning, voucher-happy, market-oriented public school systems like those found in the United States. Thus, the proposition that a social democratic state such as South Africa will offer many primary and secondary school learners far greater choice strikes many as counter-intuitive and implausible. The…

  16. Seismic velocity anisotropy and heterogeneity beneath the Mantle Electromagnetic and Tomography Experiment (MELT) region of the East Pacific Rise from analysis of P and S body waves

    USGS Publications Warehouse

    Hammond, W.C.; Toomey, D.R.

    2003-01-01

    We use teleseismic P and S delay times and shear wave splitting measurements to constrain isotropic and anisotropic heterogeneity in the mantle beneath the southern East Pacific Rise (SEPR). The data comprise 462 P and S delay times and 18 shear wave splitting observations recorded during the Mantle Electromagnetic and Tomography (MELT) Experiment. We estimate the mantle melt content (F) and temperature (T) variation from the isotropic velocity variation. Our results indicate that the maximum variation in F beneath our array is between zero and ???1.2%, and maximum variation in T is between zero and ???100 K. We favor an explanation having partial contributions from both T and F. We approximate the seismic anisotropy of the upper mantle with hexagonal symmetry, consistent with the assumption of two dimensionality of mantle flow. Our new tomographic technique uses a nonlinear inversion of P and slow S polarization delay times to simultaneously solve for coupled VP and VS heterogeneity throughout the model and for the magnitude of anisotropy within discrete domains. The domain dimensions and the dip of the anisotropy are fixed for each inversion but are varied in a grid search, obtaining the misfit of the models to the body wave delay data and to split times of vertically propagating S waves. The data misfit and the isotropic heterogeneity are sensitive to domain dimensions and dip of anisotropy. In a region centered beneath the SEPR the best average dip of the hexagonal symmetry axis is horizontal or dipping shallowly (<30??) west. Given the resolution of our data, a subaxial region characterized by vertically aligned symmetry axes may exist but is limited to be <80 km deep. We infer that the mantle flow beneath the SEPR is consistent with shallow asthenospheric return flow from the direction of the South Pacific superswell.

  17. Seismic anisotropy of the lithosphere around the Trans-European Suture Zone (TESZ) based on teleseismic body-wave data of the TOR experiment

    NASA Astrophysics Data System (ADS)

    Plomerová, J.; Babuška, V.; Vecsey, L.; Kouba, D.; TOR Working Group

    2002-12-01

    A passive teleseismic experiment (TOR), traversing the northern part of the Trans-European Suture Zone (TESZ) in Germany, Denmark and Sweden, recorded data for tomography of the upper mantle with a lateral resolution of few tens of kilometers as well as for a detailed study of seismic anisotropy. A joint inversion of teleseismic P-residual spheres and shear-wave splitting parameters allows us to retrieve the 3D orientation of dipping anisotropic structures in different domains of the sub-crustal lithosphere. We distinguish three major domains of different large-scale fabric divided by first-order sutures cutting the whole lithosphere thickness. The Baltic Shield north of the Sorgenfrei-Tornquist Zone (STZ) is characterised by lithosphere thickness around 175 km and the anisotropy is modelled by olivine aggregate of hexagonal symmetry with the high-velocity (ac) foliation plane striking NW-SE and dipping to NE. Southward of the STZ, beneath the Norwegian-Danish Basin, the lithosphere thins abruptly to about 75 km. In this domain, between the STZ and the so-called Caledonian Deformation Front (CDF), the anisotropic structures strike NE-SW and the high-velocity (ac) foliation dips to NW. To the south of the CDF, beneath northern Germany, we observe a heterogeneous lithosphere with variable thickness and anisotropic structures with high velocity dipping predominantly to SW. Most of the anisotropy observed at TOR stations can be explained by a preferred olivine orientation frozen in the sub-crustal lithosphere. Beneath northern Germany, a part of the shear-wave splitting is probably caused by a present-day flow in the asthenosphere.

  18. Our experience with smartphone and spherical lens for the eye fundus examination during humanitarian project in Africa

    PubMed Central

    Furdova, Alena; Furdova, Adriana; Krcmery, Vladimir

    2017-01-01

    To present the experience of eye fundus photo documentation by using the plus 20 diopters spherical Volk lens and a smartphone with 4.2 Mpix camera and LED flash within the screening project of eye disorders in countries where the standard ophthalmology equipment is not available. Totally 241 patients underwent ophthalmology screening examination. The documentation of the eye fundus included patients with Burkitt lymphoma, Kala Azar, malnutrition with unknown etiology, tuberculosis, HIV positive patients, Usher syndrome and hypertension. This technique as an alternative way of screening will become a standard within examination of patients with eye disorders in outfield regions of developing countries. PMID:28149793

  19. The Return of the Pholela Experiment: Medical History and Primary Health Care in Post-Apartheid South Africa

    PubMed Central

    2014-01-01

    I examine why South Africa’s pioneering Pholela model of primary health care, dating from the 1940s, held such appeal for the country’s new policymakers after 1994, and why those policymakers have failed to make it the basis of an effective public health care system since then. In the 1940s, the innovative Pholela experiment had served as such a model, to be replicated gradually throughout the country until a new health care system in its image was finally in place. However, this vision was dashed by the hostility of the mainstream medical profession and, after 1948, even more so by the new apartheid government, causing the idea to wither and become no more than a vanishing memory. In the 1990s, the model resurfaced as part of the country’s transition to democracy, eliciting great enthusiasm among a new generation of health policymakers. I conclude by looking at the fate to date of this second coming of the Pholela experiment. PMID:25208002

  20. A global approach to the management of EMR (Electronic Medical Records) of patients with HIV/AIDS in Sub-Saharan Africa: the experience of DREAM Software

    PubMed Central

    2009-01-01

    Background The DREAM Project operates within the framework of the national health systems of several sub-Saharan African countries and aims to introduce the essential components of an integrated strategy for the prevention and treatment of HIV/AIDS. The project is intended to serve as a model for a wide-ranging scale-up in the response to the epidemic. This paper aims to show DREAM's challenges and the solutions adopted. One of the solutions is the efficient management of the clinical data regarding the treatment of the patients and epidemiological analyses. Methods Specific software for the management of the patients' EMR has been created within the DREAM programme in order to deal with the challenges deriving from the context in which DREAM operates. Setting up a computer infrastructure in health centres, providing a power supply, as well as managing the data and the project resources efficiently and reliably, are some of the questions that have been analysed in this study. Results Over the years this software has proved that it is able to respond to the need for efficient management of the clinical data and organization of the health centres. Today it is used in 10 countries in sub-Saharan Africa by thousands of professionals and by now it has reached its fourth version. The medical files of over 73,000 assisted patients are managed by this software and the data collected with it have become essential for the epidemiological research that is carried out to improve the effectiveness of the therapy. Conclusion Sub-Saharan Africa is the region hardest hit by HIV and AIDS in the world. However, the resources and responses adopted so far, to confront the epidemic, have at times been rather minimalist. The DREAM project has faced the battle against the epidemic by equipping itself with qualitative standards comparable to Western ones. The experience of DREAM has revealed that it is indeed possible to guarantee levels of excellence in developing countries, also in the

  1. High resolution seismic data coupled to Multibeam bathymetry of Stromboli island collected in the frame of the Stromboli geophysical experiment: implications with the marine geophysics and volcanology of the Aeolian Arc volcanic complex (Sicily, Southern Tyrrhenian sea, Italy).

    PubMed

    Aiello, Gemma; Di Fiore, Vincenzo; Marsella, Ennio; Passaro, Salvatore

    2014-01-01

    New high resolution seismic data (Subbottom Chirp) coupled to high resolution Multibeam bathymetry collected in the frame of the Stromboli geophysical experiment aimed at recording active seismic data and tomography of the Stromboli Island are here presented. The Stromboli geophysical experiment has been already carried out based on onshore and offshore data acquisition in order to investigate the deep structure and the location of the magma chambers of the Stromboli volcano. A new detailed swath bathymetry of Stromboli Island is here shown and discussed to reconstruct an up-to-date morpho-bathymetry and marine geology of the area compared to the volcanologic setting of the Aeolian Arc volcanic complex. Due to its high resolution the new Digital Terrain Model of the Stromboli Island gives interesting information about the submerged structure of the volcano, particularly about the volcano-tectonic and gravitational processes involving the submarine flanks of the edifice. Several seismic units have been identified based on the geologic interpretation of Subbottom Chirp profiles recorded around the volcanic edifice and interpreted as volcanic acoustic basement pertaining to the volcano and overlying slide chaotic bodies emplaced during its complex volcano-tectonic evolution. They are related to the eruptive activity of Stromboli, mainly poliphasic and to regional geological processes involving the intriguing geology of the Aeolian Arc, a volcanic area still in activity and needing improved research interest.

  2. 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.

  3. A three-dimensional tomographic velocity model above Mid Atlantic magma chamber from simulated seafloor multi-channel seismic refraction experiment

    NASA Astrophysics Data System (ADS)

    Arnulf, A. F.; Harding, A. J.; Kent, G.; Singh, S. C.

    2009-12-01

    With multi-channel seismic (MCS) data recorded on the sea surface, refraction arrivals from the upper crust typically arrive as secondary arrivals after the seafloor reflection, and therefore they do not contain any information on near seafloor velocity. Here we use a Synthetic On Bottom Experiment (SOBE) method to downward continue both shots and receivers to a depth close to the seafloor, which causes refraction arrivals from the upper crust to become first arrivals that can be followed to close to zero source receiver offsets, providing information about near surface velocity. Moreover, the high density of shots and receivers in MCS-based travel-time tomography produces a multiplicity of ray paths never reached by classical travel time tomography methods based on OBS datasets, and hence providing a high-resolution velocity of the sub-surface. We have applied this new technique to the MCS data from the SISMOMAR 3D seismic reflection survey carried out in 2005 over the Lucky Strike Segment of the Mid-Atlantic Ridge. The survey area was 18.55 km by 3.8 km, with a shot spacing of 37.5 m, receiver spacing of 12.5 m and the line spacing of 100 m. It has been the first segment of the MAR to be shown to have a quasi-steady state magma chamber, and we are creating now a high resolution velocity model to investigate in detail the links between magmatism, hydrothermal circulation and faulting in this segment. First, the data was downward continued to 1.0-1.7 km below the sea surface. Then a highly efficient algorithm was used to pick ~800,000 travel times. Because of the the high density of ray paths (up to 7 million), the first arrivals of every fifth shots was picked. To control the picking consistency along a line, picks from the preceding shot was used to guide the current one. Travel time residuals, ~10 ms, and chi-squared of the final 2D model testify to excellent picking accuracy. A 3D velocity cube was then interpolated using ten equi-spaced 2D velocity models

  4. Gambian-British and Nigerian-British Children's and Families' Experiences of Migration "Back" to West Africa. Research Briefing No. 13

    ERIC Educational Resources Information Center

    Roberts-Holmes, Guy

    2013-01-01

    This research looks at the factors motivating Gambian-British and Nigerian-British parents to send their children "back" to West Africa and what this means for parents, children and families on both continents.

  5. Surveying World Heritage Islamic Monuments in North Africa: Experiences with Simple Photogrammetric Tools and no Previous Planning

    NASA Astrophysics Data System (ADS)

    Almagro, A.

    2013-07-01

    Different experiences of surveys of Islamic monuments from different sites of Tunisia, Algeria and Morocco are presented. They have been made with simple tools: one photographic camera and a laser meter, without a previous planning or prevision for the survey, profiting from visits organized during scientific meetings to which the author was invited. Some of these monuments belong to sites included in the World Heritage List, but no metric documents or only low quality information is available. Monumental Almohad gates from Rabat and Marrakech, the al-Badi palace of Marrakech, the minarets of Mansura and the Qala of Beni Hammad, the dome in front of the mihrab of the mosque of Tlemcen are some of the examples to be presented. The methodology applied is based on ideas and tools acquired in CIPA meetings proving the usefulness of these encounters but supporting the idea that "providers" should provide tools and methods and "users" should be responsible for documentation, never missing the opportunity of acquiring knowledge from the heritage during the survey process.

  6. The experiences of Batswana families regarding hospice care of AIDS patients in the Bophirima district, North West province, South Africa.

    PubMed

    Makhele, M F; Mulaudzi, F M

    2012-01-01

    The HIV/AIDS pandemic put significant strain on healthcare services in the country. Hospitals were no longer coping with the escalating number of AIDS patients. This resulted in the early discharge of patients, with some patients, too ill to be nursed at home, being sent to hospices for continued care. The Batswana had mixed feelings about hospice care, because their beliefs on patient care are based on the ubuntu philosophy, which emphasises the principle of caring for one another. The purpose of this study was to explore and describe the experiences of Batswana families regarding hospice care for patients in the Thlabane township in the province of the North West as well as to make recommendations to policy-makers to ensure that hospices are accepted by community members and utilised effectively. A qualitative, explorative, descriptive research design was applied. Purposive sampling was applied to select study participants with whom in-depth unstructured interviews were conducted. A qualitative data analysis was done by categorising, ordering, and summarising the data, and describing the findings. The findings indicated that families of patients in hospice care experienced such care as foreign to their culture. These families also experienced stigmatisation, firstly owing to the stigma associated with AIDS and secondly because they opted for hospice care. However, they also observed the high quality of care provided by the hospice and understood its benefits for AIDS patients. The study concluded that hospice care relieved families of terminally ill AIDS patients of the burden of care and enabled them to keep on working and earning a living. Recommendations to policy-makers included enhancing hospice care and ensuring the provisioning of culturally safe hospice care.

  7. New Methodology for Rapid Seismic Risk Assessment

    NASA Astrophysics Data System (ADS)

    Melikyan, A. E.; Balassanian, S. Y.

    2002-05-01

    Seismic risk is growing worldwide and is, increasingly, a problem of developing countries. Along with growing urbanization future earthquakes will have more disastrous social and economic consequences. Seismic risk assessment and reduction are important goals for each country located in seismically active zone. For Armenia these goals are of primary importance because the results of studies carried out by Armenian NSSP for assessment of the losses caused by various types of disasters in Armenia had shown that earthquakes are the most disastrous hazard for Armenia. The strategy for seismic risk reduction in 1999 was adopted by the Government of Armenia as a high priority state program. The world experience demonstrates that for efficient response the rapid assessment of seismic losses is necessary. There are several state-of-the-art approaches for seismic risk assessment (Radius, Hazus, etc.). All of them required large amount of various input data, which is impossible to collect in many developing countries, in particular in Armenia. Taking into account this very serious problem existing for developing countries, as well as rapid seismic risk assessment need immediately after strong earthquake the author undertake the attempt to contribute into a new approach for rapid seismic risk assessment under the supervision of Prof. S. Balassanian. The analysis of numerous factors influencing seismic risk in Armenia shows that the following elements contribute most significantly to the possible losses: seismic hazard; density of population; vulnerability of structures. Proposed approach for rapid seismic risk assessment based on these three factors has been tested for several seismic events. These tests have shown that such approach might represent from 80 to 90 percent of real losses.

  8. Systematic literature review of integrated community case management and the private sector in Africa: Relevant experiences and potential next steps

    PubMed Central

    Awor, Phyllis; Miller, Jane; Peterson, Stefan

    2014-01-01

    Background Despite substantial investments made over the past 40 years in low income countries, governments cannot be viewed as the principal health care provider in many countries. Evidence on the role of the private sector in the delivery of health services is becoming increasingly available. In this study, we set out to determine the extent to which the private sector has been utilized in providing integrated care for sick children under 5 years of age with community–acquired malaria, pneumonia or diarrhoea. Methods We reviewed the published literature for integrated community case management (iCCM) related experiences within both the public and private sector. We searched PubMed and Google/Google Scholar for all relevant literature until July 2014. The search terms used were “malaria”, “pneumonia”, “diarrhoea”, “private sector” and “community case management”. Results A total of 383 articles referred to malaria, pneumonia or diarrhoea in the private sector. The large majority of these studies (290) were only malaria related. Most of the iCCM–related studies evaluated introduction of only malaria drugs and/or diagnostics into the private sector. Only one study evaluated the introduction of drugs and diagnostics for malaria, pneumonia and diarrhoea in the private sector. In contrast, most iCCM–related studies in the public sector directly reported on community case management of 2 or more of the illnesses. Conclusions While the private sector is an important source of care for children in low income countries, little has been done to harness the potential of this sector in improving access to care for non–malaria–associated fever in children within the community. It would be logical for iCCM programs to expand their activities to include the private sector to achieve higher population coverage. An implementation research agenda for private sector integrated care of febrile childhood illness needs to be developed and implemented in

  9. The ENAM Explosive Seismic Source Test

    NASA Astrophysics Data System (ADS)

    Harder, S. H.; Magnani, M. B.

    2013-12-01

    We present the results of the pilot study conducted as part of the eastern North American margin (ENAM) community seismic experiment (CSE) to test an innovative design of land explosive seismic source for crustal-scale seismic surveys. The ENAM CSE is a community based onshore-offshore controlled- and passive-source seismic experiment spanning a 400 km-wide section of the mid-Atlantic East Coast margin around Cape Hatteras. The experiment was designed to address prominent research questions such as the role of the pre-existing lithospheric grain on the structure and evolution of the ENAM margin, the distribution of magmatism, and the along-strike segmentation of the margin. In addition to a broadband OBS deployment, the CSE will acquire multichannel marine seismic data and two major onshore-offshore controlled-source seismic profiles recording both marine sources (airguns) and land explosions. The data acquired as part of the ENAM CSE will be available to the community immediately upon completion of QC procedures required for archiving purposes. The ENAM CSE provides an opportunity to test a radically new and more economical design for land explosive seismic sources used for crustal-scale seismic surveys. Over the years we have incrementally improved the performance and reduced the cost of shooting crustal seismic shots. These improvements have come from better explosives and more efficient configuration of those explosives. These improvements are largely intuitive, using higher velocity explosives and shorter, but larger diameter explosive configurations. However, recently theoretical advances now allow us to model not only these incremental improvements, but to move to more radical shot designs, which further enhance performance and reduce costs. Because some of these designs are so radical, they need experimental verification. To better engineer the shots for the ENAM experiment we are conducting an explosives test in the region of the ENAM CSE. The results of

  10. Design of the IPIRG-2 simulated seismic forcing function

    SciTech Connect

    Olson, R.; Scott, P.; Wilkowski, G.

    1996-02-01

    A series of pipe system experiments was conducted in IPIRG-2 that used a realistic seismic forcing function. Because the seismic forcing function was more complex than the single-frequency increasing-amplitude sinusoidal forcing function used in the IPIRG-1 pipe system experiments, considerable effort went into designing the function. This report documents the design process for the seismic forcing function used in the IPIRG-2 pipe system experiments.

  11. 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

  12. Midget Seismic in Sandbox Models

    NASA Astrophysics Data System (ADS)

    Krawczyk, C. M.; Buddensiek, M. L.; Philipp, J.; Kukowski, N.; Oncken, O.

    2008-12-01

    Analog sandbox simulation has been applied to study geological processes to provide qualitative and quantitative insights into specific geological problems. In nature, the structures, which are simulated in those sandbox models, are often inferred from seismic data. With the study introduced here, we want to combine the analog sandbox simulation techniques with seismic physical modeling of those sandbox models. The long-term objectives of this approach are (1) imaging of seismic and seismological events of actively deforming and static 3D analogue models, and (2) assessment of the transferability of the model data to field data in order to improve field data acquisition and interpretation according to the addressed geological problem. To achieve this objective, a new midget-seismic facility for laboratory use was designed and developed, comprising a seismic tank, a PC control unit including piezo-electric transducers, and a positioning system. The first experiments are aimed at studying the wave field properties of the piezo- transducers in order to investigate their feasibility for seismic profiling. The properties investigated are their directionality and the change of waveform due to their size (5-12 mm) compared to the wavelengths (< 1.5 mm). The best quality signals and least directionality and waveform change are achieved when the center source frequency is between 350-500 kHz, and the offset is less than 8 cm for a reflector depth of 10 cm. With respect to the technical hardware reflection processing on such a small scale is feasible as long as the offset does not exceed a certain value, which is dependent on the reflector depth and frequency. The next steps will include a study of material properties and the effects of wave propagation in an-/isotropic media by physical studies, before we finally start using different seismic imaging and processing techniques on static and actively deforming 3D analog models.

  13. What device would be best for early infant male circumcision in east and southern Africa? Provider experiences and opinions with three different devices in Kenya

    PubMed Central

    Nyaboke, Irene; Otieno, Fredrick O.

    2017-01-01

    Voluntary medical male circumcision (VMMC) reduces risk of HIV acquisition in heterosexual men by approximately 60%. As some countries approach targets for proportions of adolescents and adults circumcised, some are considering early infant male circumcision (EIMC) as a means to achieve sustainability of VMMC for long term reduction of HIV incidence. Evaluations of specialized devices for EIMC are important to provide programs with information required to make informed decisions about how to design safe, effective EIMC programs. We provide assessments by 11 providers with experience in Kenya employing all three of the devices most likely to be considered by various EIMC programs in east and Southern Africa. There was no one device that was seen to be clearly superior to the others. Each had its own advantages and disadvantages. Provider preferences were situation-specific. Most preferred the Mogen Clamp if they themselves were performing the procedure. However, most were concerned that not everyone will have the skills necessary for optimal safety. If someone else were circumcising their son, most would opt for the AccuCirc because of the risk of severing the glans when using the Mogen. A minority preferred the PrePex, but only if the baby received local anesthesia, not EMLA cream (a eutectic mixture of lidocaine 2.5% and prilocaine 2.5%), as presently prescribed by the manufacturer. In the context of a national EIMC program, all participants agreed that AccuCirc would be the device they would recommend due to protection of the glans from laceration and to the provision of a pre-assembled sterile kit that overcomes the need for additional supplies or autoclaving. All agreed that scaling up EIMC, integrating it with existing maternal child health services, will face significant challenges, not least of which is persuading already over-burdened providers to take on additional workload. These results will be useful to programmers considering introduction of EIMC

  14. "It is better to die": experiences of traditional health practitioners within the HIV treatment as prevention trial communities in rural South Africa (ANRS 12249 TasP trial).

    PubMed

    Moshabela, Mosa; Zuma, Thembelihle; Orne-Gliemann, Joanna; Iwuji, Collins; Larmarange, Joseph; McGrath, Nuala

    2016-01-01

    The ANRS 12249 Treatment-as-Prevention (TasP) cluster-randomized trial in rural South Africa uses a "test and treat" approach. Home-based testing services and antiretroviral treatment initiation satellite clinics were implemented in every cluster as part of the trial. A social science research agenda was nested within TasP with the aim of understanding the social, economic and contextual factors that affect individuals, households, communities and health systems with respect to TasP. Considering the rural nature of the trial setting, we sought to understand community perceptions and experiences of the TasP Trial interventions as seen through the eyes of traditional health practitioners (THPs). A qualitative study design was adopted using four repeat focus group discussions conducted with nine THPs, combined with community walks and photo-voice techniques, over a period of 18 months. A descriptive, interpretive and explanatory approach to analysis was adopted. Findings indicate that THPs engaged with the home-based testing services and HIV clinics established for TasP. Specifically, home-based testing services were perceived as relatively successful in increasing access to HIV testing. A major gap observed by THPs was linkage to HIV clinics. Most of their clients, and some of the THPs themselves, found it difficult to use HIV clinics due to fear of labelling, stigma and discrimination, and the ensuing personal implications of unsolicited disclosure. On the one hand, a growing number of patients diagnosed with HIV have found sanctuary with THPs as alternatives to clinics. On the other hand, THPs in turn have been struggling to channel patients suspected of HIV into clinics through referrals. Therefore, acceptability of the TasP test and treat approach by THPs is a major boost to the intervention, but further success can be achieved through strengthened ties with communities to combat stigma and effectively link patients into HIV care, including partnerships with THPs

  15. The Impact of Inventory Management on Stock-Outs of Essential Drugs in Sub-Saharan Africa: Secondary Analysis of a Field Experiment in Zambia

    PubMed Central

    Leung, Ngai-Hang Z.; Chen, Ana; Yadav, Prashant; Gallien, Jérémie

    2016-01-01

    Objective To characterize the impact of widespread inventory management policies on stock-outs of essential drugs in Zambia’s health clinics and develop related recommendations. Methods Daily clinic storeroom stock levels of artemether-lumefantrine (AL) products in 2009–2010 were captured in 145 facilities through photography and manual transcription of paper forms, then used to determine historical stock-out levels and estimate demand patterns. Delivery lead-times and estimates of monthly facility accessibility were obtained through worker surveys. A simulation model was constructed and validated for predictive accuracy against historical stock-outs, then used to evaluate various changes potentially affecting product availability. Findings While almost no stock-outs of AL products were observed during Q4 2009 consistent with primary analysis, up to 30% of surveyed facilities stocked out of some AL product during Q1 2010 despite ample inventory being simultaneously available at the national warehouse. Simulation experiments closely reproduced these results and linked them to the use of average past monthly issues and failure to capture lead-time variability in current inventory control policies. Several inventory policy enhancements currently recommended by USAID | DELIVER were found to have limited impact on product availability. Conclusions Inventory control policies widely recommended and used for distributing medicines in sub-Saharan Africa directly account for a substantial fraction of stock-outs observed in common situations involving demand seasonality and facility access interruptions. Developing central capabilities in peripheral demand forecasting and inventory control is critical. More rigorous independent peer-reviewed research on pharmaceutical supply chain management in low-income countries is needed. PMID:27227412

  16. Somalian Earthquakes of May, 1980, East Africa

    SciTech Connect

    Ruegg, J.C.; Lepine, J.C.; Tarantola, A.; Leveque, J.J.

    1981-04-01

    A seismic crisis, with a m/sub b/ = 5.3 main shock, occured in the Somali Republic East Africa (10 /sup 0/N, 43 /sup 0/E) from April to November 1980. Up to 2000 earthquakes with M/sub L/>2 have been recorded during this period. This earthquake sequence is of particular interest because it occurred in a seismically inactive zone and include a rather long aftershock sequence. Two groups of epicenters were identified using a relative location procedure. Aftershocks observed during the first two weeks fall very close to the Borama City, while latter shocks are situated 10km west. This may suggest that the second group of earthquakes has been induced continental margin between the Somalian Plateau shield and the quasi-oceanic crust of the Afar-Gulf of Aden region, remains active to day and is relevant to intraplate seismicity.

  17. West Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    With its vast expanses of sand, framed by mountain ranges and exposed rock, northwestern Africa makes a pretty picture when viewed from above. This image was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra spacecraft. The Canary Islands can be seen on the left side of the image just off Africa's Atlantic shore. The light brown expanse running through the northern two thirds of the image is the Sahara Desert. The desert runs up against the dark brown Haut Atlas mountain range of Morocco in the northwest, the Atlantic Ocean to the west and the semi-arid (light brown pixels) Sahelian region in the South. The Sahara, however, isn't staying put. Since the 1960s, the desert has been expanding into the Sahelian region at a rate of up to 6 kilometers per year. In the 1980s this desert expansion, combined with over cultivation of the Sahel, caused a major famine across west Africa. Over the summer months, strong winds pick up sands from the Sahara and blow them across the Atlantic as far west as North America, causing air pollution in Miami and damaging coral reefs in the Bahamas and the Florida Keys. The white outlines on the map represent country borders. Starting at the top-most portion of the map and working clockwise, the countries shown are Morocco, Western Sahara, Mauritania, Senegal, Mali, Burkina Fasso, Nigeria, Mali (again), and Algeria. Image by Reto Stockli, Robert Simmon, and Brian Montgomery, NASA Earth Observatory, based on data from MODIS

  18. 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.

  19. Monitoring seismic wave speed by an active seismic source

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  20. 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.

  1. Otrag rocket experiments in Africa

    NASA Technical Reports Server (NTRS)

    1978-01-01

    West German rocket manufacturers are testing their products in Zaire. Hundreds of pipes (12 m x 80 cm) are bundled together inside the test missiles, which are fired into Zaire's prairie. The reactions of neighboring nations, as well as leading countries of the world, are presented concerning the rocket tests.

  2. Automating Shallow Seismic Imaging

    SciTech Connect

    Steeples, Don W.

    2004-12-09

    make SSR surveying considerably more efficient and less expensive, particularly when geophone intervals of 25 cm or less are required. The most recent research analyzed the difference in seismic response of the geophones with variable geophone spike length and geophones attached to various steel media. Experiments investigated the azimuthal dependence of the quality of data relative to the orientation of the rigidly attached geophones. Other experiments designed to test the hypothesis that the data are being amplified in much the same way that an organ pipe amplifies sound have so far proved inconclusive. Taken together, the positive results show that SSR imaging within a few meters of the earth's surface is possible if the geology is suitable, that SSR imaging can complement GPR imaging, and that SSR imaging could be made significantly more cost effective, at least in areas where the topography and the geology are favorable. Increased knowledge of the Earth's shallow subsurface through non-intrusive techniques is of potential benefit to management of DOE facilities. Among the most significant problems facing hydrologists today is the delineation of preferential permeability paths in sufficient detail to make a quantitative analysis possible. Aquifer systems dominated by fracture flow have a reputation of being particularly difficult to characterize and model. At chemically contaminated sites, including U.S. Department of Energy (DOE) facilities and others at Department of Defense (DOD) installations worldwide, establishing the spatial extent of the contamination, along with the fate of the contaminants and their transport-flow directions, is essential to the development of effective cleanup strategies. Detailed characterization of the shallow subsurface is important not only in environmental, groundwater, and geotechnical engineering applications, but also in neotectonics, mining geology, and the analysis of petroleum reservoir analogs. Near-surface seismology is in

  3. [Epidemic typhus in Africa].

    PubMed

    Ndihokubwayo, J B; Raoult, D

    1999-01-01

    Epidemic typhus is caused by a small strictly intracellular virus named Rickettsia prowazekii, a member of the Rickettsial family. It is transmitted to man by the body louse, Pediculus humanus. Although now rare in Western countries, exanthematic typhus remains common in the Southern hemisphere due to poverty, inadequate clothing hygiene, and poor socioeconomic conditions. In Africa, outbreaks have historically occurred in Burundi, Rwanda, southwest Ouganda, and Ethiopia. The largest outbreak of epidemic typhus since the World War II was reported in Burundi where ongoing civil war since October 1993 has forced 10 p. 100 of the population of Burundi to live in cold, promiscuity, and malnutrition of makeshift refugee camps. The purpose of this report based on our two-year experience working with this unfortunate population is to describe the characteristics of this disease in Africa where the epidemic form had become rare until recently. Indeed political unrest as well as numerous civil wars are now epidmiological factors favorizing outbreaks of epidemic typhus at any time. This overview also provides an opportunity to recall epidemiological, bacteriological, and clinical aspects of typhus as well as diagnosis and treatment of the disease in the context of Africa.

  4. An evaluation of methodology for seismic qualification of equipment, cable trays, and ducts in ALWR plants by use of experience data

    SciTech Connect

    Bandyopadhyay, K.K.; Kana, D.D.; Kennedy, R.P.; Schiff, A.J.

    1997-07-01

    Advanced Reactor Corporation (ARC) has developed a methodology for seismic qualification of equipment, cable trays and ducts in Advanced Light Water Reactor plants. A Panel (members of which acted as individuals) supported by the Office of Nuclear Regulatory Research of the Nuclear Regulatory Commission has evaluated this methodology. The review approach and observations are included in this report. In general, the Panel supports the ARC methodology with some exceptions and provides recommendations for further improvements. 26 refs., 10 figs., 1 tab.

  5. Tectonic deformation of the Andes and the configuration of the subducted slab in central Peru: Results from a micro-seismic experiment

    NASA Technical Reports Server (NTRS)

    Suarez, G.; Gagnepain, J. J.; Cisternas, A.; Hatzfeld, D.; Molnar, P.; Ocola, L.; Roecker, S. W.; Viode, J. P.

    1983-01-01

    The vast majority of the microearthquakes recorded occurred to the east: on the Huaytapallana fault in the Eastern Cordillera or in the western margin of the sub-Andes. The sub-Andes appear to be the physiographic province subjected to the most intense seismic deformation. Focal depths for the crustal events here are as deep as 50 km, and the fault plane solutions, show thrust faulting on steep planes oriented roughly north-south. The Huaytapallana fault in the Cordillera Oriental also shows relatively high seismicity along a northeast-southwest trend that agrees with the fault scarp and the east dipping nodal plane of two large earthquakes that occurred on this fault in 1969. The recorded microearthquakes of intermediate depth show a flat seismic zone about 25 km thick at a depth of about 100 km. This agrees with the suggestion that beneath Peru the slab first dips at an angle of 30 deg to a depth of 100 km and then flattens following a quasi-horizontal trajectory. Fault plane solutions of intermediate depth microearthquakes have horizontal T axes oriented east-west.

  6. Separation of site effects and structural focusing in Santa Monica, California: A study of high-frequency weak motions from earthquakes and blasts recorded during the Los Angeles Region Seismic Experiment

    USGS Publications Warehouse

    Baher, S.; Davis, P.M.; Fuis, G.

    2002-01-01

    Near-surface site factors and the effects of deep structural focusing were estimated in the Santa Monica Mountains and Santa Monica, California, from a portable array of 75 seismic stations deployed during the Los Angeles Region Seismic Experiment, Phase II (LARSE II). The objective was to examine further the origin of seismic wave amplification in the region of intense damage south of the Santa Monica Fault from the Northridge earthquake. The analysis used normalized spectral amplitudes in the 4- to 8- and 8- to 12-Hz range in direct and coda waves from local earthquakes in Santa Paula, Northridge, Redlands, and Hector Mine. Coda waves indicated that site factor amplifications are larger south of the Santa Monica fault relative to the north. Spectral ratios of direct S waves, corrected for site effects, show additional amplificaton south of, and adjacent to, the Santa Monica fault, attributable to focusing by a deeper structure. Gao et al. (1996) concluded that localized focusing effects contributed to anomalous P- and S-wave amplification in the Santa Monica damage zone for Northridge aftershocks within a specified range of azimuths. In an attempt to reproduce the hypothesized focusing from the Northridge earthquake, two shots (4000 and 3750 lb.) were detonated, one at Pyramid Lake, a distance of about 69 km to the north-northwest of central Santa Monica, and the other near Fort Tejon, a distance of 91 km. The azimuth of the shots was chosen to be that expected to give anomalous amplification. At these distance steeply incident seismic energy from Pg/PmP waves are expected to pass through the underground focusing structure and be selectively amplified. After the local site factors are removed, the waveforms from the Fort Tejon shot exhibited localized amplification adjacent to and south of the fault, 2-3 times larger than that of the surrounding area. The effect is less for waves from the Pyramid Lake shot, which could be due to their higher angle of incidence

  7. 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.

  8. 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

  9. Water harvesting experience in sub-Saharan Africa - lessons for sustainable intensification of rainfed agriculture and the influence of available soils and rainfall data

    NASA Astrophysics Data System (ADS)

    Gowin, John; Bunclark, Lisa

    2013-04-01

    Africa is seen by many as the continent with the greatest potential for agricultural growth, but land degradation and environmental change threaten the African soil resource more severely than in many other regions of the planet. Achieving future food security will depend mainly on increasing production from rainfed agriculture. The challenge of delivering the required sustainable intensification in rainfed agriculture is most acute in the drylands - the semi-arid and dry sub-humid climatic regions. There are two broad strategies for increasing yields under these circumstances: (1) capturing more rainwater and storing it (increasing water availability), and (2) using the available water more effectively by increasing the plant growth and/or reducing non-productive soil evaporation (increasing water productivity). We focus on the first of these options - water harvesting, which is defined as, "the collection and concentration of rainfall runoff, or floodwaters, for plant production". The benefits of water harvesting have been documented from small scale experimental plot studies, but evidence of successful adoption and impact is weak. As a contribution to improving the evidence base, we present results from an investigation conducted in SSA to gather information on progress with efforts to promote adoption of water harvesting. The intention was to investigate in detail the processes and outcomes on a large enough sample area to draw some common conclusions. This was not a comprehensive analysis of all that is happening in each country, nor was it a random sample; this was a purposive sample guided by available baseline information to permit comparative analysis. Water harvesting seems to have made the most progress where techniques can be adopted by individual farmers: in Burkina Faso and Niger micro- scale zaï /tassa and demi-lune systems; in Sudan and Tanzania meso-scale majaruba and teras systems. Macro-scale systems requiring social organisation may offer

  10. Deep seismic sounding in northern Eurasia

    USGS Publications Warehouse

    Benz, H.M.; Unger, J.D.; Leith, W.S.; Mooney, W.D.; Solodilov, L.; Egorkin, A.V.; Ryaboy, V.Z.

    1992-01-01

    For nearly 40 years, the former Soviet Union has carried out an extensive program of seismic studies of the Earth's crust and upper mantle, known as “Deep Seismic Sounding” or DSS [Piwinskii, 1979; Zverev and Kosminskaya, 1980; Egorkin and Pavlenkova, 1981; Egorkin and Chernyshov, 1983; Scheimer and Borg, 1985]. Beginning in 1939–1940 with a series of small-scale seismic experiments near Moscow, DSS profiling has broadened into a national multiinstitutional exploration effort that has completed almost 150,000 km of profiles covering all major geological provinces of northern Eurasia [Ryaboy, 1989].

  11. Laboratory simulation of volcano seismicity.

    PubMed

    Benson, Philip M; Vinciguerra, Sergio; Meredith, Philip G; Young, R Paul

    2008-10-10

    The physical processes generating seismicity within volcanic edifices are highly complex and not fully understood. We report results from a laboratory experiment in which basalt from Mount Etna volcano (Italy) was deformed and fractured. The experiment was monitored with an array of transducers around the sample to permit full-waveform capture, location, and analysis of microseismic events. Rapid post-failure decompression of the water-filled pore volume and damage zone triggered many low-frequency events, analogous to volcanic long-period seismicity. The low frequencies were associated with pore fluid decompression and were located in the damage zone in the fractured sample; these events exhibited a weak component of shear (double-couple) slip, consistent with fluid-driven events occurring beneath active volcanoes.

  12. Seismic Imaging of Sandbox Models

    NASA Astrophysics Data System (ADS)

    Buddensiek, M. L.; Krawczyk, C. M.; Kukowski, N.; Oncken, O.

    2009-04-01

    Analog sandbox simulations have been applied to study structural geological processes to provide qualitative and quantitative insights into the evolution of mountain belts and basins. These sandbox simulations provide either two-dimensional and dynamic or pseudo-three-dimensional and static information. To extend the dynamic simulations to three dimensions, we combine the analog sandbox simulation techniques with seismic physical modeling of these sandbox models. The long-term objective of this approach is to image seismic and seismological events of static and actively deforming 3D analog models. To achieve this objective, a small-scale seismic apparatus, composed of a water tank, a PC control unit including piezo-electric transducers, and a positioning system, was built for laboratory use. For the models, we use granular material such as sand and glass beads, so that the simulations can evolve dynamically. The granular models are required to be completely water saturated so that the sources and receivers are directly and well coupled to the propagating medium. Ultrasonic source frequencies (˜500 kHz) corresponding to wavelengths ˜5 times the grain diameter are necessary to be able to resolve small scale structures. In three experiments of different two-layer models, we show that (1) interfaces of layers of granular materials can be resolved depending on the interface preparation more than on the material itself. Secondly, we show that the dilation between the sand grains caused by a string that has been pulled through the grains, simulating a shear zone, causes a reflection that can be detected in the seismic data. In the third model, we perform a seismic reflection survey across a model that contains both the prepared interface and a shear zone, and apply 2D-seismic reflection processing to improve the resolution. Especially for more complex models, the clarity and penetration depth need to be improved to study the evolution of geological structures in dynamic

  13. 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.

  14. The time lapse experiment in Al Wasse water pumping field in Saudi Arabia by an ultra-stable seismic source (ACROSS)

    NASA Astrophysics Data System (ADS)

    AlAnezi, Ghunaim; Kasahara, Junzo; AlDamegh, Khaled S.; Lafouza, Omar; AlYousef, Khaled; Almalki, Fahad; Nishiyama, Eichiro

    2015-04-01

    We have developed the time lapse technology for EOR (enhanced oil recovery) and CCS (Carbon Capture and Storage) using a very stable and continuous seismic source called ACROSS (Accurately Controlled Routinely Operated Signal System) with multi-geophones. Since 2011, we have tested this technology in the context of carbonate rocks in Saudi Arabia. The Al Wasee water pumping site approximately 120 km east of Riyadh city has been selected as a trail-site. The intention is to observe the changes in aquifers induced by pumping operations. One ACROSS source unit was installed at the Al Wasee site in December 2011 and we are continuing the field test. The instrument has been operated from 10 to 50 Hz with 40 tons-f at 50 Hz. Using alternatively clockwise and counter-clockwise rotations we can synthesize vertical and horizontal forces, respectively. 31 3C-geophones in 2 km x 3 km area and four nearby 3Cgeophones have been used to monitor the seismic changes from pumping the water. The one and half month data between December 2012 and February 2013 show continuous and clear change of observed waveforms for all 31 stations while the source signature did not change. The change is closest and fastest at the station #42. The cause of continuous change with time is interpreted as pumping of water by 64 wells located in this field.

  15. 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.

  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. The seismicity of Ethiopia; active plate tectonics

    USGS Publications Warehouse

    Mohr, P.

    1981-01-01

    Ethiopia, descended from the semimythical Kingdom of Punt, lies at the strategic intersection of Schmidt's jigsaw puzzle where the Red Sea, Gulf of Aden, and the African Rift System meet. Because of geologically recent uplift combined with rapid downcutting erosion by rivers, notably the Blue Nile (Abbay), Ethiopia is the most mountainous country in Africa. It is also the most volcanically active, while its historical seismicity matches that of the midocean ridges. And, in a sense, Ethiopia is host to an evoloving ocean ridge system. 

  18. 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

  19. The critical angle in seismic interferometry

    USGS Publications Warehouse

    Van Wijk, K.; Calvert, A.; Haney, M.; Mikesell, D.; Snieder, R.

    2008-01-01

    Limitations with respect to the characteristics and distribution of sources are inherent to any field seismic experiment, but in seismic interferometry these lead to spurious waves. Instead of trying to eliminate, filter or otherwise suppress spurious waves, crosscorrelation of receivers in a refraction experiment indicate we can take advantage of spurious events for near-surface parameter extraction for static corrections or near-surface imaging. We illustrate this with numerical examples and a field experiment from the CSM/Boise State University Geophysics Field Camp.

  20. Central and southern Africa

    SciTech Connect

    McGrew, H.J.

    1981-10-01

    Exploration in central and southern Africa continued to expand during 1980. The greatest concentration of activity was in Nigeria. However, there was considerable increase in the level of exploratory work in Cameroon and Congo. Significant new finds have been made in Ivory Coast. Geological and geophysical activity was carried out in 18 of the countries, with those in the western part having the largest share. Seismic work involved 225 party months of operation. Most of this time was spent on land, but marine operations accounted for 73,389 km of new control. Gravity and magnetic data were recorded during the marine surveys, and several large aeromagnetic projects were undertaken to obtain a total of 164,498 line km of data. Exploratory and development drilling accounted for a total of 304 wells and 2,605,044 ft (794,212 m) of hole. The 92 exploratory wells that were drilled resulted in 47 oil and gas discoveries. In development drilling 89% of the 212 wells were successful. At the end of the year, 27 exploratory wells were underway, and 34 development wells were being drilled for a total of 61. Oil production from the countries that this review covers was 918,747,009 bbl in 1980, a drop of about 9% from the previous year. Countries showing a decline in production were Nigeria, Gabon, Cabinda, and Zaire. Increases were recorded in Cameroon, Congo, and Ghana. A new country was added to the list of producers when production from the Belier field in Ivory Coast came on stream. 33 figures, 15 tables.

  1. Seismic hazard impact of the Lower Tagus Valley Fault Zone (SW Iberia)

    NASA Astrophysics Data System (ADS)

    Vilanova, Susana P.; Fonseca, Joao F. B. D.

    The seismic hazard of SW Iberia is composed of two contributions: offshore, large to very large events on the plate boundary between Africa and Eurasia such as the Lisbon earthquake of 1755 or the Gorringe Bank earthquake of 1969; and onshore, moderate to strong intraplate earthquakes on inherited crustal fractures. One of these zones of crustal weakness is the Lower Tagus Valley (LTV) fault zone, which displays the highest level of seismic hazard in Western Iberia. In this paper we review the active tectonics and seismicity of the LTV, integrating previous geophysical data with recent results of paleoseismological investigations, and discuss its impact on the seismic hazard of SW Iberia. We conclude that the seismic zonation for hazard assessment currently in force in the building code is biased towards the scenario of distant offshore rupture, and does not take adequately into account the LTV seismic source.

  2. Crust structure of the Northern Margin of North China Craton and adjacent region from Sinoprobe-02 North China seismic WAR/R experiment

    NASA Astrophysics Data System (ADS)

    Li, W.; Gao, R.; Keller, G. R.; Li, Q.; Cox, C. M.; Hou, H.; Guan, Y.

    2011-12-01

    The Central Asian Orogen Belt (CAOB) or Altaids, situated between the Siberian craton(SC) to the north and north China craton (NCC) with tarim to the south, is one of the world's largest accretionary orogens formed by subduction and accretion of juvenile material from the Neoproterozoic through the Paleozoic. The NCC is the oldest craton in China, which suffered Yanshan intercontinental orogenic process and lithosphere thinning in Mesozoic. In the past 20 years, remarkable studies about this region have been carried out and different tectonic models were proposed, however, some crucial geologic problems remain controversial. In order to obtain better knowledge of deep structure and properties of crust on the northern margin of north China craton, a 450 km long WAR/R section was completed jointly by Institute of Geology, CAGS and University of Oklahoma. Our 450 km long NW-SE WAR/R line extends from west end of the Yanshan orogen, across the Bainaimiao arc, Ondor sum subduction accretion complex to the Solonker suture zone. The recording of seismic waves from 8 explorations was conducted in 4 deployments of 300 reftek-125A records and single-channel 4.5Hz geophones with station spacing of 1km. The shooting procedure was employ 500 or 1500kg explosives in 4-5 or 15-23 boreholes at 40-45m depth. The sampling rate was 100 HZ, and recording time window was 1200s. The P wave field on the sections got high quality data for most part of the profile, but have low signal-to-noise for the south end, where closed to Beijing with a lot of ambient noise from traffic, industry and human activity. Arrivals from of refracted and reflected waves from sediments and basement (Pg), intracrust (Pcp, Plp) and Moho (Pmp) were typically observed, but Pn phase through the upper most mantle was only observed for 2 shots. Identification and correlation of seismic phases was done manually on computer screen Zplot software. Each trace has been bandpass filtered (1-20Hz) and normalized with AGC

  3. The lunar seismic tomography and internal heterogeneity

    NASA Astrophysics Data System (ADS)

    Zhao, N.; Zhu, P.; Yuan, Y.; Zhang, J.

    2012-12-01

    A seismic tomography is presented to show the internal lateral heterogeneities of moon. The lunar seismic tomography is made from the moonquake arrival-time data acquired by the Apollo program during 1971 to 1977. The seismic records obtained from the four seismic station of Apollo Lunar Surface Experiments Package on the moon. The research target covers the surround of Apollo-12, 14, 15 and 16 landing sites. A preliminary image of three-dimensional P- and S-wave velocity structures of lunar interior have been calculated using hundreds of arrival-times of moonquake events from surface to deep mantle. These results show that some evidences of lateral heterogeneities in the lunar mantle and crust, which implies the existence of complex structure inside the moon.

  4. Seismicity of the Earth 1900‒2013 Mediterranean Sea and vicinity

    USGS Publications Warehouse

    Herman, Matthew W.; Hayes, Gavin P.; Smoczyk, Gregory M.; Turner, Rebecca; Turner, Bethan; Jenkins, Jennifer; Davies, Sian; Parker, Amy; Sinclair, Allison; Benz, Harley M.; Furlong, Kevin P.; Villaseñor, Antonio

    2015-09-08

    The Mediterranean region is seismically active due to the convergence of the Africa Plate with the Eurasia plate. Present day Africa-Eurasia motion ranges from ~4 millimeters per year (mm/yr) in a northwest-southeast direction in the western Mediterranean to ~10 mm/yr (north-south) in the eastern Mediterranean. The Africa-Eurasia plate boundary is complex, and includes extensional and translational zones in addition to the dominant convergent regimes characterized by subduction and continental collision. This convergence began at approximately 50 million years ago and was associated with the closure of the Tethys Sea; the Mediterranean Sea is all that remains of the Tethys. The highest rates of seismicity in the Mediterranean region are found along the Hellenic subduction zone of southern Greece and the North Anatolian Fault Zone of northwestern Turkey, but significant rates of current seismicity and large historical earthquakes have occurred throughout the region spanning the Mediterranean Sea.

  5. New Madrid Seismic Zone

    DTIC Science & Technology

    2007-11-02

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

  6. Africa: Prosperous times

    SciTech Connect

    1996-08-01

    Political instability and corruption is the rule, rather than the exception, in Africa`s main producing regions, but exploration and production prospects there are bright and attractive to foreign operators. The paper discusses exploration, drilling, resource development, and production in Nigeria, Libya, Algeria, Egypt, Angola, Congo, Gabon, and Tunisia. The other countries of Africa are briefly mentioned, i.e., Cameroon, Cote D`Ivoire, South Africa, Sudan, Namibia, Equatorial Guinea, Eritrea, Zaire, Mozambique, Ghana, Niger, and Seychelles.

  7. Impact of infectious disease epidemics on tuberculosis diagnostic, management, and prevention services: experiences and lessons from the 2014-2015 Ebola virus disease outbreak in West Africa.

    PubMed

    Ansumana, Rashid; Keitell, Samuel; Roberts, Gregory M T; Ntoumi, Francine; Petersen, Eskild; Ippolito, Giuseppe; Zumla, Alimuddin

    2017-03-01

    The World Health Organization (WHO) Global Tuberculosis Report 2015 states that 28% of the world's 9.6 million new tuberculosis (TB) cases are in the WHO Africa Region. The Mano River Union (MRU) countries of West Africa-Guinea, Sierra Leone, and Liberia-have made incremental sustained investments into TB control programmes over the past two decades. The devastating Ebola virus disease (EVD) outbreak of 2014-2015 in West Africa impacted significantly on all sectors of the healthcare systems in the MRU countries, including the TB prevention and control programmes. The EVD outbreak also had an adverse impact on the healthcare workforce and healthcare service delivery. At the height of the EVD outbreak, numerous staff members in all MRU countries contracted EBV at the Ebola treatment units and died. Many healthcare workers were also infected in healthcare facilities that were not Ebola treatment units but were national hospitals and peripheral health units that were unprepared for receiving patients with EVD. In all three MRU countries, the disruption to TB services due to the EVD epidemic will no doubt have increased Mycobacterium tuberculosis transmission, TB morbidity and mortality, and decreased patient adherence to TB treatment, and the likely impact will not be known for several years to come. In this viewpoint, the impact that the EVD outbreak had on TB diagnostic, management, and prevention services is described. Vaccination against TB with BCG in children under 5 years of age was affected adversely by the EVD epidemic. The EVD outbreak was a result of global failure and represents yet another 'wake-up call' to the international community, and particularly to African governments, to reach a consensus on new ways of thinking at the national, regional, and global levels for building healthcare systems that can sustain their function during outbreaks. This is necessary so that other disease control programmes (like those for TB, malaria, and HIV) are not

  8. Seismic Waveguide of Metamaterials

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Hoon; Das, Mukunda P.

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

  9. 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.

  10. Peer-to-Peer Consultations: Ancillary Services Peer Exchange with India: Experience from South Africa, Europe & the United States (Fact Sheet)

    SciTech Connect

    Not Available

    2014-05-01

    In support of national and subnational decision makers, the 21st Century Power Partnership regularly works with country partners to organize peer-to-peer consultations on critical issues. In March 2014, 21CPP collaborated with the Regulatory Assistance Project - India to host two peer-to-peer exchanges among experts from India, South Africa, Europe, and the United States to discuss the provision of ancillary services, particularly in the context of added variability and uncertainty from renewable energy. This factsheet provides a high level summary of the peer-to-peer consultation.

  11. A seismotectonic model from the strain field of Africa

    NASA Astrophysics Data System (ADS)

    Fernandes, Rui; Meghraoui, Mustapha; Radwan, Ali

    2013-04-01

    Using ~100 available permanent GNSS stations we compute a velocity field to obtain the current strain field in Africa. GPS stations with short data span (>2.5 years data span) and monument/equipment instability are excluded for the estimated velocity field. Although significant gaps of geodetic stations still exist, particularly on the Central and North (include Sahara) Africa, the aim is to produce reliable velocity solutions and evaluate the strain velocity field across the African continent with respect to the latest global reference frame (ITRF2008). We consider in our geodetic data analysis the uncertainties related with the temporal correlations between the daily solutions of stations (computed using HECTOR). The geodynamic characteristics of the African plate and its complex sub-plate distribution are better constrained with the increasing number of GNSS permanent stations in Africa (our latest angular velocity model for the three major tectonic units uses a total of 37 solutions: NUBI: 25; SMLA: 07; VICT: 05). The occurrence of recent large intraplate and interplate earthquakes and volcanic activity in Nubia and Somalia combined with the results of geodetic networks contribute to a better constraint of the kinematics along plate boundaries. The comparison between the geodetic strain rate with the seismic strain release along seismically active plate boundaries permit us to observe the existence of zones of localized active deformation with geodetic rate larger than seismic moment rate. Regional studies also show negligible seismic activity in zones with active faults and where the internal plate deformation estimated with geodetic strain fields is significant. This work is prepared in the framework of the IGCP Project 601 - "Seismotectonics and Seismic Hazards in Africa".

  12. Seismic Constraints on Geometry, Seismic Velocity and Anisotropy of the "African Anomaly"

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Wen, L.

    2006-05-01

    Seismic evidence shows that the "African Anomaly", a prominent low-velocity structure in the lower mantle beneath Africa, has a broad base near the core-mantle boundary (CMB) and extends at least 1000 km upward into the mid-lower mantle. Waveform modeling results indicate that its base is a very-low velocity province (VLVP) in the lowermost 200-300 km of the Earth's mantle with rapidly varying geometries and a strong Vs reduction gradient of -2% - -12% from top to bottom. These features unambiguously indicate the VLVP is compositionally distinct and can be best explained by partial melting driven by a compositional change produced in the early Earth's history [Wen, 2001; Wen et. al, 2001; Wang and Wen, 2004]. Seismic structure for the mid-lower mantle portion of the "African Anomaly" and the anisotropic behavior related to the VLVP remain unclear. In this presentation, we will present seismic data to constrain geometry and both P- and S- velocity perturbations for the "African Anomaly" along the great arc from the East Pacific Rise to the Japan Sea, and discuss seismic anisotropic behavior inside the VLVP and in the surrounding areas. We collected direct S, ScS, SKS, and SKKS waveforms data sets for 9 earthquakes recorded at the temporary broadband Kaapvaal, Tanzania, and Ethiopia/Kenya seismic arrays in Africa. These seismic data provide reasonably good coverage for the "African Anomaly" along a great circle path in opposite directions. We corrected for the effects of the earthquake mislocation and the seismic heterogeneities outside the anomaly. Seismic data suggest that the "African Anomaly" exhibits a "cusp-like" shape along the great arc and continuously extends from the CMB to about 1300 km above the CMB with both sides tilting toward its center beneath southern Africa. The magnitude of these travel time residuals can be best explained by a shear velocity structure with average Vs reductions of -5% for the basal layer and -2% - -3% for the portion in the

  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. 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

  16. Seismic spatial wavefield gradient and rotational rate measurements as new observables in land seismic exploration

    NASA Astrophysics Data System (ADS)

    Schmelzbach, Cedric; Sollberger, David; Van Renterghem, Cédéric; Häusler, Mauro; Robertsson, Johan; Greenhalgh, Stewart

    2016-04-01

    Traditionally, land-seismic data acquisition is conducted using vertical-component sensors. A more complete representation of the seismic wavefield can be obtained by employing multicomponent sensors recording the full vector wavefield. If groups of multicomponent sensors are deployed, then spatial seismic wavefield gradients and rotational rates can be estimated by differencing the outputs of closely spaced sensors. Such data capture all six degrees of freedom of a rigid body (three components of translation and three components of rotation), and hence allow an even more complete representation of the seismic wavefield compared to single station triaxial data. Seismic gradient and rotation data open up new possibilities to process land-seismic data. Potential benefits and applications of wavefield gradient data include local slowness estimation, improved arrival identification, wavefield separation and noise suppression. Using synthetic and field data, we explored the reliability and sensitivity of various multicomponent sensor layouts to estimate seismic wavefield gradients and rotational rates. Due to the wavelength and incidence-angle dependence of sensor-group reception patterns as a function of the number of sensors, station spacing and layout, one has to counterbalance the impacts of truncation errors, random noise attenuation, and sensitivity to perturbations such as amplitude variations and positioning errors when searching for optimum receiver configurations. Field experiments with special rotational rate sensors were used to verify array-based rotational-rate estimates. Seismic wavefield gradient estimates and inferred wavefield attributes such as instantaneous slowness enable improved arrival identification, e.g. wave type and path. Under favorable conditions, seismic-wavefield gradient attributes can be extracted from conventional vertical-component data and used to, for example, enhance the identification of shear waves. A further promising

  17. Seismic Absorption and Modulus Measurements in Porous Rocks in Lab and Field: Physical, Chemical, and Biological Effects of Fluids (Detecting a Biosurfactant Additive in a Field Irrigation Experiment)

    SciTech Connect

    Spetzler, Hartmut

    2006-05-01

    We have been exploring a new technology that is based on using low-frequency seismic attenuation data to monitor changes in fluid saturation conditions in two-fluid phase porous materials. The seismic attenuation mechanism is related to the loss of energy due to the hysteresis of resistance to meniscus movement (changes in surface tension, wettability) when a pore containing two fluids is stressed at very low frequencies (< 10 Hz). This technology has potential applications to monitoring changes in (1) leakage at buried waste sites, (2) contaminant remediation, and (3) flooding during enhanced petroleum recovery. We have concluded a three year field study at the Maricopa Agricultural Center site of the University of Arizona. Three sets of instruments were installed along an East-West line perpendicular to the 50m by 50m inigation site. Each set of instruments consisted of one three component seismometer and one tiltmeter. Microseisms and solid Earth-tides served as strain sources. The former have a power peak at a period of about 6 seconds and the tides have about two cycles per day. Installation of instruments commenced in late summer of 2002. The instruments operated nearly continuously until April 2005. During the fall of 2003 the site was irrigated with water and one year later with water containing 150 ppm of a biosurfactant additive. This biodegradable additive served to mimic a class of contaminants that change the surface tension of the inigation fluid. Tilt data clearly show tidal tilts superimposed on local tilts due to agricultural irrigation and field work. When the observed signals were correlated with site specific theoretical tilt signals we saw no anomalies for the water irrigation in 2003, but large anomalies on two stations for the surfactant irrigation in 2004. Occasional failures of seismometers as well as data acquisition systems contributed to less than continuous coverage. These data are noisier than the tilt data, but do also show possible

  18. Basic space sciences in Africa

    NASA Astrophysics Data System (ADS)

    Abiodun, Adigun Ade; Odingo, Richard S.

    Through space applications, a number of social and economic programmes in education, communications, agro-climatology, weather forecasting and remote sensing are being realized within the African continent. Regional and international organizations and agencies such as the African Remote Sensing Council, the Pan-African Telecommunication Union and the United Nations system have been instrumental in making Africa conscious of the impact and implications of space science and technology on its peoples. The above notwithstanding, discernible interests in space research, to date, in Africa, have been limited to the work on the solar system and on interplanetary matters including satellite tracking, and to the joint African-Indian proposal for the establishment of an International Institute for Space Sciences and Electronics (INISSE) and the construction, in Kenya, of a Giant Equatorial Radio Telescope (GERT). During this ``Transport and Communications Decade in Africa,'' Africa's basic space research efforts would need to initially focus on the appropriateness, modification and adaptation of existing technologies for African conditions with a view to providing economic, reliable and functional services for the continent. These should include elements of electronics, communications, structural and tooling industries, and upper-atmosphere research. The experience of and collaborative work with India, Brazil and Argentina, as well as the roles of African scientists, are examined.

  19. Monitoring of low-energy seismic activity in Elbrus volcanic area with the use of underground seismic array

    NASA Astrophysics Data System (ADS)

    Kovalevsky, V.; Sobisevitch, A.

    2012-04-01

    Results of experiment with underground seismic array for studying low-energy seismic activity in the Elbrus volcanic area are presented. Linear seismic array of 2.5 km aperture is created in the tunnel of Baksan neutrino observatory. Horizontal tunnel of 4.3 km length is drilled in the mount Andyrchi at a distance of 20 km from Elbrus volcano. Array includes 6 three-component seismic sensors with 24-byte recorders installed with 500 m interval one from another along the tunnel. Underground seismic array is the new instrument of geophysical observatory organized for studies of geophysical processes in the Elbrus volcanic area. The observatory equipped with modern geophysical instruments including broadband tri-axial seismometers, quartz tilt-meters, magnetic variometers, geo-acoustic sensors, hi-precision distributed thermal sensors and gravimeters. The initial analysis of seismic signals recorded by seismic array allows us to detect low-energy seismic activity in the Elbrus volcanic area beginning from the distance of 3-5 km (the faults in a vicinity of mount Andyrchi) up to 15-25 km (area of Elbrus volcano). The regional micro-earthquakes with magnitude 1-2 at the distances 50-100 km was also recorded. 2.5 km aperture of the underground linear seismic array make it possible to determine with high accuracy hypocenters of local seismic events associated with geodynamic of volcanic magmatic structures and to realize seismo-emission tomography of the active zones of Elbrus volcano.

  20. Seismic Waveform Characterization at LLNL: Analyst Guidelines and Issues

    SciTech Connect

    Ryall, F; Schultz, C A

    2001-11-01

    In the first section of this paper we present an overview of general set of procedures that we have followed in seismic waveform analysis. In the second section we discuss a number of issues and complexities that we have encountered in analysis of events in the Middle East, North Africa, Europe, and parts of the European Arctic. To illustrate these complexities we can include examples of waveforms recorded over a variety of paths in these regions.