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Lombardi M.A.,U.S. National Institute of Standards and Technology | Levine J.,U.S. National Institute of Standards and Technology | Bernard J.,National Research Council Canada | Gertsvolf M.,National Research Council Canada | And 6 more authors.
Proceedings of the Annual Precise Time and Time Interval Systems and Applications Meeting, PTTI | Year: 2014

This paper describes a recently designed system that measures the time transmitted by network time protocol (NTP) servers located in North, Central, and South America. Direct measurements of the time transmitted by each server are obtained by comparing the received time stamps to the Cordinated Universal Time scale, UTC(NIST), located at the National Institute of Standards and Technology (NIST) in Boulder, Colorado. International comparisons of the time differences between servers are obtained by utilizing UTC(NIST) as a common-view observation signal. Results of both direct and common-view measurements are published in real time via the web site of the Sistema Interamericano de Metrologia (SIM) Time and Frequency Metrology Working Group, providing verification of a given server's accuracy. The paper describes the NTP measurement system, and presents results from direct comparison and common-view measurements. It also discusses factors that contribute uncertainty to NTP measurements; in particular network asymmetry caused by inconsistent routing and/or network congestion.


Lombardi M.A.,U.S. National Institute of Standards and Technology | Novick A.N.,U.S. National Institute of Standards and Technology | Boulanger J.-S.,National Research Council Canada | Pelletier R.,National Research Council Canada | And 11 more authors.
Journal of Research of the National Institute of Standards and Technology | Year: 2011

The Sistema Interamericano de Metrologia (SIM) is a regional metrology organization (RMO) whose members are the national metrology institutes (NMIs) located in the 34 nations of the Organization of American States (OAS). The SIM/OAS region extends throughout North, Central, and South America and the Caribbean Islands. About half of the SIM NMIs maintain national standards of time and frequency and must participate in international comparisons in order to establish metrological traceability to the International System (SI) of units. The SIM time network (SIMTN) was developed as a practical, cost effective, and technically sound way to automate these comparisons. The SIMTN continuously compares the time standards of SIM NMIs and produces measurement results in near real-time by utilizing the Internet and the Global Positioning System (GPS). Fifteen SIM NMIs have joined the network as of December 2010. This paper provides a brief overview of SIM and a technical description of the SIMTN. It presents international comparison results and examines the measurement uncertainties. It also discusses the metrological benefits that the network provides to its participants.


PubMed | Saint Lucia Bureau of Standards SLBS, Instituto Costarricense Of Electricidad Ice, National Observatory ONRJ, U.S. National Institute of Standards and Technology and 9 more.
Type: Journal Article | Journal: Journal of research of the National Institute of Standards and Technology | Year: 2016

The Sistema Interamericano de Metrologia (SIM) is a regional metrology organization (RMO) whose members are the national metrology institutes (NMIs) located in the 34 nations of the Organization of American States (OAS). The SIM/OAS region extends throughout North, Central, and South America and the Caribbean Islands. About half of the SIM NMIs maintain national standards of time and frequency and must participate in international comparisons in order to establish metrological traceability to the International System (SI) of units. The SIM time network (SIMTN) was developed as a practical, cost effective, and technically sound way to automate these comparisons. The SIMTN continuously compares the time standards of SIM NMIs and produces measurement results in near real-time by utilizing the Internet and the Global Positioning System (GPS). Fifteen SIM NMIs have joined the network as of December 2010. This paper provides a brief overview of SIM and a technical description of the SIMTN. It presents international comparison results and examines the measurement uncertainties. It also discusses the metrological benefits that the network provides to its participants.


Mora M.M.,University of Costa Rica | Lesage P.,University of Savoy | Albino F.,Royal Museum for Central Africa | Soto G.J.,Instituto Costarricense Of Electricidad Ice | Alvarado G.E.,Instituto Costarricense Of Electricidad Ice
Special Paper of the Geological Society of America | Year: 2013

Arenal Volcano is a small (~1750 m above sea level, ~10 km3) stratovolcano that continuously erupted between July 1968 and October 2010. During this longlasting eruption (over 42 yr), a large volume of material-~5.6 × 108 m3 of dense rock equivalent-has been extruded and has produced a thick and extended lava field, mainly on the western fl ank of the edifi ce. Measurements of ground deformation obtained using a network of dry-tilt stations are presented for the period 1986-2000. They show a continuous subsidence of the volcano with maximal amplitude on the western side. The load effect of the lava field is calculated and explains the largest part of the observed tilts. Once the data are corrected by this load effect, pressure source models are not supported by the observations and by quality criteria on the models. Although the dry-tilt data from Arenal Volcano give limited constraints onthe deformation models, they are representative of a long period of activity that cannot be recovered by other means. Moreover, the corresponding interpretative model is consistent with results obtained by geotechnical studies and modern ground deformation methods like interferometric syntheticaperture radar (InSAR). © 2013 The Geological Society of America. All rights reserved.


Benito M.B.,Polytechnic University of Mozambique | Lindholm C.,NORSAR | Camacho E.,University of Panamá | Climent A.,Instituto Costarricense Of Electricidad Ice | And 7 more authors.
Bulletin of the Seismological Society of America | Year: 2012

A new evaluation of seismic hazard in Central America has been carried out as part of the cooperation project named RESIS II under the auspices of the Norway Cooperation Agency (NORAD). Several seismic-hazard experts from Costa Rica, Guatemala, Honduras, Nicaragua, El Salvador, Panamá, Norway, and Spain participated in the study, which was aimed at obtaining results suitable for seismic design purposes. The analysis started with a thorough revision of the national seismic catalogs from which a catalog for Central America has been compiled and homogenized to moment magnitude, M w. Seismotectonic models proposed for the region were revised, and a new regional zonation was proposed, taking into account seismotectonic data, seismicity, focal mechanisms, and GPS observations. Besides, ground-motion prediction equations (GMPEs) for subduction, volcanic, and crustal zones were revised, and the most suitable ones were calibrated with Central American strongmotion data. Subsequently, a seismic-hazard analysis was developed in terms of peak ground acceleration (PGA) and spectral accelerations SA (T) for periods of 0.1, 0.2, 0.5, 1, and 2 s, by means of the probabilistic seismic-hazard assessment (PSHA) approach. As a result, different hazard maps were obtained for the quoted parameters, together with uniform hazard spectra (UHS) for six of the capital cities of Central America. Disaggregation was also carried out in these capitals for the target motion given by the PGA and SA (1 s) and obtained for return periods of 500 years and 2500 years. Therefore, the control earthquakes for motions of short and long periods were derived. This is the first study developed in Central America at a regional scale after 10 years.


Eyre T.S.,University College Dublin | Bean C.J.,University College Dublin | De Barros L.,University College Dublin | O'Brien G.S.,University College Dublin | And 5 more authors.
Journal of Volcanology and Geothermal Research | Year: 2013

Long-period (LP) seismic events were recorded during the temporary installation of a broadband seismic network of 13 stations from March to September 2009 on Turrialba volcano, Costa Rica. Over 6000 LPs were extracted using a modified STA/LTA method and a family consisting of 435 similar LP events has been identified. For the first time at Turrialba volcano, full-waveform moment tensor inversion is performed to jointly determine the location and source mechanism of the events. The LPs in the family are likely to be caused by crack mechanisms dipping towards the southwest at angles of approximately 10 to 20°, located at shallow depths (< 800 m) below the active Southwest and Central craters. As the locations are so shallow, the most probable causes of crack mechanisms are hydrothermal fluids resonating within or "pulsing" through a crack. The waveforms observed at the summit stations suggest a "pulsing" mechanism, but source resonance with a high degree of damping is also possible. © 2013 Elsevier B.V.


Umana Villalobos G.,University of Costa Rica | Acuna Gonzalez J.,University of Costa Rica | Garcia Cespedes J.,University of Costa Rica | Aguero Alfaro G.,Municipalidad de Mora | And 3 more authors.
Revista de Biologia Tropical | Year: 2015

Phytoplankton primary production (PP) was determined in a broad sector of the Térraba-Sierpe National Wetland, Costa Rica, from September to November 2008 in the rainy season and from January to March 2009 in the dry season. Six sampling stations were located at the Northern and Central zone of the wetland, according to the main expected flux of Río Grande de Térraba. Additionally other environmental parameters such as Secchi disk depth, suspended solid matter concentration, chlorophyll-α concentration, salinity, temperature, dissolved oxygen concentration, dissolved inorganic nutrients concentrations (phosphate, nitrate, ammonium and silicate), specific conductivity were also measured and a principal components analysis was performed. The PP in the Terraba-Sierpe National Wetland (HNTS by its Spanish name) was generally low, with a maximum value of 8.16gC/m2·d of Net Primary Productivity (NPP), which was recorded in the dry season, in March 2009, at Loros island. Sites that had a greater riverine influence showed lower PP values, while sites with greater marine influence presented higher PP values. These latter had an average and standard deviation of 0.79±0.50gC/m2·d (n=12). This difference is the result of the high input of freshwater and suspended solids from the Río Grande de Térraba which limits the development of marine phytoplankton in the wetland. © 2015, Universidad de Costa Rica. All rights reserved.


Rojas W.,University of Costa Rica | Alvarado G.E.,Instituto Costarricense Of Electricidad Ice | Alvarado G.E.,University of Costa Rica
Revista de Biologia Tropical | Year: 2012

The Isla del Coco (also known as Cocos Island), in the Eastern Pacific Ocean, has a rough topography, an area of 24km2, and is the only sub-aerial topographic height of the summit of a volcano located in the margin of the Cordillera Volcánica del Coco (also known as Cocos Ridge). The Cocos Ridge is a well defined linear bathymetric height, issued from the active volcanism of the Galápagos hotspot during the last 15 million years (Ma); it is the largest geographic feature of Costa Rica, as a volcanic range of 780km long in its territorial seawaters. Isla del Coco is part of a submarine shield volcano of complex evolution, which erupted several times above sea level during the Lower Pleistocene (2.2-1.5Ma). The island and other seamounts are the result from a mantle thermal anomaly that erupted through volcano-tectonic fissures in the oceanic crust. The rocks consist mainly of alkali basaltic lava flows (aa, pahoehoe, blocky lavas) and dikes, minor trachyte lava flows, volcanic domes and dikes, with subordinate pyroclastic and epivolcanic rocks. Colluvial, soils and local littoral deposits such as sand and gravel beaches are also present. The island has a juvenile erosive stadium, but their submarine erosive arcs and platforms (90-110m and 183m depth) are probably the result of the erosion occurred during last two glacial maxima, besides slow subsidence events of the island due the thermal cooling of the volcanic shield and its oceanic crust. The most important current external geodynamic hazards are landslides, tsunamis and rare seismic events, Mw ≤ 5.8 in a 300km radio associated to N-S right lateral strike slip faults. However, the limited seismic data available, and geomorphological alignments, indicates that there is some seismic activity related to local faults oriented N-S, ENE and in a lesser extend NW trend. Seismicity and rainfall have triggered landslides; liquefaction is restricted to Chatham and Wafer bays’ beaches. Moderate historical and prehistorical tsunamis were related to regional seismic events. The relative young age of Isla del Coco makes it an interesting place to study the evolution and migration of species, and their genetic features. More detailed studies related to tephrostratigraphy, neotectonics, marine geomorphology, evolution of seamounts, lava flow morphology, and submarine hydrothermal activity, are still necessary to understand the expression of internal geodynamic processes in this region. © 2012, Universidad de Costa Rica. All rights reserved.


Perez A.A.,Instituto Costarricense Of Electricidad Ice | Vogt T.,Carl von Ossietzky University
EPJ Web of Conferences | Year: 2014

This study estimates the total storage capacity for renewable energies in European salt caverns up to the year 2030 in order to deal with the fluctuation of renewable energies. The round-trip efficiencies and the CO2 equivalent direct emissions of the different storage process stages are taken into account. These are transmission, electricity to gas conversion, storage and re-electrification from gas to electricity, of three different energy carriers, namely compressed air, hydrogen and renewable methane. © Owned by the authors, published by EDP Sciences, 2014.

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