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News Article | April 19, 2017
Site: www.eurekalert.org

Despite broad understanding of volcanoes, our ability to predict the timing, duration, type, size, and consequences of volcanic eruptions is limited, says a new report by the National Academies of Sciences, Engineering, and Medicine WASHINGTON - Despite broad understanding of volcanoes, our ability to predict the timing, duration, type, size, and consequences of volcanic eruptions is limited, says a new report by the National Academies of Sciences, Engineering, and Medicine. To improve eruption forecasting and warnings to save lives, the report identifies research priorities for better monitoring of volcanic eruptions and three grand challenges facing the volcano science community. Volcano monitoring is critical for forecasting eruptions and mitigating risks of their hazards. However, few volcanoes are adequately observed, and many are not monitored at all. For example, fewer than half of the 169 potentially active volcanoes in the U.S. have any seismometers -- an instrument to detect small earthquakes that signal underground magma movement. And only three have continuous gas measurements, which are crucial because the composition and quantity of dissolved gases in magma drive eruptions. Enhanced monitoring combined with advances in experimental and mathematical models of volcanic processes can improve the understanding and forecasting of eruptions, the report says. The committee that conducted the study and wrote the report also highlighted the need for satellite measurements of ground deformation and gas emissions, drone observations, advanced seismic monitoring, and real-time high-speed acquisition of data during eruptions. New approaches in analytical capabilities to decipher magma history, and conceptual and experimental models of magmatic and volcanic phenomena, will provide new insights on the processes that explain how magma is generated and erupts. "There have been great improvements in conceptual models of volcanic phenomena, compared with those used a few decades ago, but the volcano science community is not yet adequately prepared for the next large eruption," said Michael Manga, professor in the department of earth and planetary science at the University of California, Berkeley, and chair of the committee. "There are fundamental challenges that need to be addressed and require a sustained effort from across disciplines. By working toward these grand challenges, the volcano science community can help quantify the global effect of eruptions and mitigate hazards, ultimately benefiting millions of people living in volcanically active areas." The committee outlined several key questions and research priorities in areas such as the processes that move and store magma beneath volcanoes; how eruptions begin, evolve, and end; how a volcano erupts; forecasting eruptions; the response of landscapes, oceans, and the atmosphere to volcanic eruptions; and the response of volcanoes to changes on Earth's surface. Based on these research priorities, the committee identified three overarching grand challenges for advancing volcano science and monitoring: Forecasting the size, duration, and hazard of eruptions by integrating observations with models Current forecasts are based on recognizing patterns in monitoring data. These approaches have had mixed success because monitoring data do not capture the diversity of volcanoes or their evolution over time. An approach based on models of physical and chemical processes, informed by monitoring data, as is done in weather forecasting, could improve the accuracy of eruption forecasts. Such an approach requires integrating data and methodologies from multiple disciplines, the report says. Quantifying the life cycles of volcanoes and overcoming our current biased understanding Current understanding of a volcano's life cycle is skewed because only a small number of volcanoes are studied. Extended monitoring from the ground, sea, and space can overcome some of these observational biases, the report says. Expanding and maintaining monitoring capabilities and supporting the infrastructure to make historical and monitoring data available are critical for advancing understanding of volcanic processes and assessing volcanic hazards. The committee noted that emerging technologies such as inexpensive sensors, drones, and new micro-analytical geochemical methods are promising tools to provide new insights into volcanic activity. Close to 100 volcanoes erupt somewhere on Earth each year. Strengthening multidisciplinary research, domestic and international research and monitoring partnerships, and training networks can help the research community maximize scientific advances that result from the study of eruptions around the world, the committee said. The report cites the ongoing eruption at Bogoslof volcano in Alaska as an example that highlights these three challenges. A remote, initially submarine volcano in the Aleutian Island arc, the eruption started in late December 2016 and the activity has been continuing as of February 2017. In just one month, the volcano produced numerous explosions with plumes rising 20,000-35,000 feet, posing a significant hazard to North Pacific aviation. The U.S. Geological Survey Alaska Volcano Observatory (AVO) has been relying on distant seismometers, satellite data, infrasound, and lightning detection to monitor the activity because there are no ground-based instruments on the volcano. The committee said AVO has been able to provide early warning for only some of these hazardous events. This eruption also underscores the limited understanding of magma eruption. In more than 20 discrete events, the emerging volcano has reshaped its coastlines repeatedly, providing snapshots of volcano-landscape interactions. The study was sponsored by the National Science Foundation, NASA, the U.S. Geological Survey, and the National Academies of Sciences, Engineering, and Medicine. The National Academies are private, nonprofit institutions that provide independent, objective analysis and advice to the nation to solve complex problems and inform public policy decisions related to science, technology, and medicine. They operate under an 1863 congressional charter to the National Academy of Sciences, signed by President Lincoln. For more information, visit http://national-academies. . A roster follows. Riya V. Anandwala, Media Relations Officer Joshua Blatt, Media Relations Assistant Office of News and Public Information 202-334-2138; e-mail news@nas.edu national-academies.org/newsroom Follow us on Twitter @theNASEM Copies of Volcanic Eruptions and Their Repose, Unrest, Precursors, and Timing are available at http://www. or by calling 202-334-3313 or 1-800-624-6242. Reporters may obtain a copy from the Office of News and Public Information (contacts listed above). THE NATIONAL ACADEMIES OF SCIENCES, ENGINEERING, AND MEDICINE Michael Manga (chair) Professor of Earth and Planetary Science Department of Earth and Planetary Science University of California Berkeley Simon A. Carn Associate Professor Department of Geological and Mining Engineering and Sciences Michigan Technological University Houghton Katharine V. Cashman* Professor of Volcanology School of Earth Sciences University of Bristol Bristol, United Kingdom Kari M. Cooper Professor Department of Earth and Planetary Sciences University of California Davis Tobias Fischer Professor Department of Earth and Planetary Sciences University of New Mexico Albuquerque Bruce Houghton Gordon A. Macdonald Professor of Volcanology and Science Director National Disaster Preparedness Training Center School of Ocean and Earth Science and Technology University of Hawai'i Manoa Diana C. Roman Staff Scientist Department of Terrestrial Magnetism Carnegie Institution for Science Washington, D.C. Paul Segall* Professor of Geophysics School of Earth, Energy, and Environmental Sciences Stanford University Stanford, Calif.

Miquel B.,Geological and Mining Engineering | Bouaanani N.,Geological and Mining Engineering
Engineering Structures | Year: 2010

This paper proposes a practical procedure for a simplified evaluation of the fundamental vibration period of damwater systems, and corresponding added damping, force and mass, all key parameters to assess the seismic behavior. The proposed technique includes the effects of dam geometry and flexibility, damreservoir interaction, water compressibility and varying reservoir level. The mathematical derivations of the method are provided considering both incompressible and compressible water assumptions. In the former case, we propose a closed-form expression for the fundamental vibration period of a damreservoir system. When water compressibility is included, we show that the fundamental vibration period can be obtained by simply solving a cubic equation. The proposed procedure is validated against classical Westergaard added mass formulation as well as other more advanced analytical and finite element techniques. Gravity dam monoliths with various geometries and rigidities impounding reservoirs with different heights are investigated. The new approach yields results in excellent agreement with those obtained when the reservoir is modeled analytically, or numerically using potential-based finite elements. The analytical expressions developed and the procedure steps are presented in a manner so that calculations can be easily implemented in a spreadsheet or program for simplified and practical seismic analysis of gravity dams. © 2010 Elsevier Ltd.

Tfaily R.,Geological and Mining Engineering | Papineau I.,Geological and Mining Engineering | Andrews R.C.,University of Toronto | Barbeau B.,Geological and Mining Engineering
Journal - American Water Works Association | Year: 2015

A quantitative microbial risk assessment model developed by Health Canada was applied at 17 water treatment plants (WTPs) located throughout Ontario and Quebec, Canada. Four source water characterization methods were compared that considered Escherichia coli, Giardia, and Cryptosporidium. In addition, three strategies to evaluate chemical disinfection performances were compared (median disinfectant exposure [CT50], regulatory disinfectant exposure [CT10], and continuous-stirred tank reactors in-series [N-CSTR, where N is the number of CSTRs in the series]). The N-CSTR approach provides more reliable risk estimates because it is less sensitive to high inactivation conditions (when compared with use of CT10 or CT50). Predicted risk estimates for the 17 WTPs revealed that only two did not comply with the 10â€"6 disability-adjusted life years (World Health Organization) and 10â€"4 risk of infection (US Environmental Protection Agency) reference levels because of the poor performance of direct filtration without coagulation. This publically available quantitative microbial risk assessment model could help WTP managers assess overall treatment performance via a systematic evaluation process. © 2015 American Water Works Association.

Papineau I.,Geological and Mining Engineering | Tufenkji N.,McGill University | Barbeau B.,Geological and Mining Engineering
Water Science and Technology: Water Supply | Year: 2013

Granular filtration remains a key barrier for Cryptosporidium removal in water treatment plants without UV irradiation. To assess the impact of clay particles in source water on Cryptosporidium removal efficiency by granular filtration, this study investigated the co-transport of Cryptosporidiumsized microspheres and kaolinite particles in sand columns. To investigate the influence of clay load on microsphere transport and deposition, varying influent kaolinite concentrations (0-106 particles/mL) and microsphere concentrations (102-106 microspheres/mL) were tested. The spatial distribution of retained microspheres was examined subsequent to experiments via filter coring. Results demonstrate that increasing the influent microsphere concentration impaired filter performance due to a blocking mechanism whereby previously retained particles repel incoming particles. In contrast, when the particulate load was dominated by kaolinite (for an equivalent particulate load), filter performance improved as a result of filter ripening whereby previously deposited particles act as additional collectors. Thus, microsphere-kaolinite interactions proved to be favorable although both particles possessed negative zeta potentials in the tested conditions. This study demonstrates that granular filter performance is vulnerable to peak events of microbial contamination. Conversely, Cryptosporidium-sized microsphere removal by granular filtration is enhanced in the presence of kaolinite in source water.© IWA Publishing 2013 Water Science and Technology: Water Supply.

Lachance F.,Geological and Mining Engineering | Charron J.-P.,Geological and Mining Engineering | Charron J.-P.,Ecole Polytechnique de Montréal | Massicotte B.,Geological and Mining Engineering | Massicotte B.,Ecole Polytechnique de Montréal
ACI Structural Journal | Year: 2016

In this study, the mechanical behavior of cast-in-place (CIP) and precast bridge slabs in transverse bending was established with static and fatigue tests simulating truck loading. The three selected slab configurations include a high-performance concrete (HPC) CIP slab, and two fiber-reinforced concrete (FRC) precast slabs: one hybrid design using high-performance fiber-reinforced concrete (HPFRC) and ultra-high-performance fiber-reinforced concrete (UHPFRC), and one using only UHPFRC. The structural behavior of the three slabs is analyzed and compared in terms of stiffness, deflection, crack opening, and ultimate strength. The static tests demonstrated that all three slab configurations largely exceeded the design criterion of ultimate strength, even after the application of cyclic loadings. The hybrid and UHPFRC slabs showed minor crack widths in service and fatigue conditions, whereas the reference HPC slab presented crack widths superior to the 0.25 mm (0.010 in.) criterion under the same conditions. Copyright © 2016, American Concrete Institute. All rights reserved.

Erochko J.,University of Toronto | Christopoulos C.,University of Toronto | Tremblay R.,Geological and Mining Engineering | Choi H.,Sungkyunkwan University
Journal of Structural Engineering | Year: 2011

A recent study has shown that residual drifts after earthquakes that are greater than 0.5% in buildings may represent a complete loss of the structure from an economic perspective. To study the comparative residual drift response of special moment-resisting frames (SMRFs) and buckling-restrained braced (BRB) frames, buildings between 2 and 12 stories in height are designed according to ASCE 7-05 and investigated numerically. This investigation includes pushover analyses as well as two-dimensional nonlinear time-history analyses for two ground motion hazard levels. The two systems show similar peak drifts and drift concentration factors. The BRB frames experience larger residual drifts than the SMRFs; however, the scatter in the residual drift results is large. Expressions are proposed to estimate the residual drifts of these systems as a function of the expected peak drifts, the initial recoverable elastic drift, and the drift concentration factor of each system. When subjected to a second identical earthquake, both framing systems experienced larger-than-expected drifts when an initial drift greater than 0.5% was present. © 2011 American Society of Civil Engineers.

Moreau R.,McGill University | Rogers C.,McGill University | Tremblay R.,Geological and Mining Engineering
Proceedings, Annual Conference - Canadian Society for Civil Engineering | Year: 2013

Steel concentrically braced frames (CBFs) are popular seismic-force-resisting systems for low-to medium-rise buildings in Canada. Hollow structural section (HSS) members are commonly used for the lateral braces of these CBFs. HSS braces are often connected to the bracing-bent frames by using a slotted tube-to-gusset plate or knife-plate connection. This connection creates the potential under seismic loading for fracture of the tube through the net section, which can be further affected by shear lag. Shear lag factors calculated according to CSA S16 are quite penalizing, and can lead to expensive connection reinforcements when seismic capacity design methods must be applied. Furthermore, it is known that the yield stress of steel increases with strain rate; this places additional demand on the connection since it must be designed for the expected yield strength of the brace under seismic loading. However, strain-rate effects are typically ignored in design. This paper describes the testing of four HSS brace connections for HSS 152 × 152 × 9.5 and HSS 203 × 203 × 13.0 members under monotonic tensile loading. For each tube size, one brace was tested under a static rate, while the other brace was tested using a strain rate consistent with that which would occur during a design level earthquake. This paper reports on the applicability of existing design shear lag factors for square HSS sections, as well as the effect of strain rate on HSS brace connection behaviour.

Boudreault J.-P.,École de Technologie Supérieure of Montreal | Dube J.-S.,École de Technologie Supérieure of Montreal | Marcotte D.,Geological and Mining Engineering
Geoderma | Year: 2016

The remediation of contaminated sites is recognized as a means towards the sustainable development of an expanding urban space on the global scale. However, it is often hindered by financial and environmental risks caused by undetected contamination or unreliable site characterization. Uncertainty in site characterization studies is suspected to be a cause of this problem. Therefore, there is a need for formally defining and quantifying the uncertainty linked to estimates of the spatial distribution of contamination and the volume of contaminated soils at polluted sites. The objective of this study was to develop a geostatistical procedure for the 3-D analysis of a multi-element contamination in order to: 1) optimize the location and the number of sampling stations during a complementary sampling campaign, 2) estimate the volume of contaminated soil for a given data set and 3) quantify the uncertainty of this estimate. This procedure is innovative because it takes into account, by a transformation in pollution indices, the presence of a multi-element contamination and applies to a set of 3-D data. Furthermore, this procedure offers a formal framework that adapts the decisional bounds to the study site to help the decision-maker. The proposed procedure was applied to an urban site characterized by the presence of a strongly heterogeneous fill. From a subset initially constituted of 8 sampling stations, supplemental sampling stations were selected within a complementary data set and added one by one to the iterative geostatistical simulations. The completeness of the sampling plan was determined upon reaching stability in the relative differences of both global uncertainty and global variance between two successive steps of the optimization. According to the procedure presented, a sampling plan could be considered optimized and complete with 19 sampling stations for this study site (comparatively to 38 sampling stations for the total set obtained by systematic sampling). For 19 sampling stations, the global uncertainty was determined to be 20% (comparatively to 16% for the total set). © 2015 Elsevier B.V.

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