Data report: Seismic structure beneath the North Cascadia drilling transect of IODP Expedition 311

Between 1999 and 2004, new seismic data became available for the study of gas hydrates on the northern Cascadia margin. These data consist of multi- and single-channel data with two- and partly three-dimensional subsurface coverage and were acquired and used in support of the proposal for Integrated Ocean Drilling Program (IODP) Expedition 311 carried out in 2005. The working area lies across the continental slope off the coast of central Vancouver Island, British Columbia, Canada, with water depths ranging from 2600 m in the trench to 500 m on the upper slope, where it is well above the minimum depth for gas hydrate stability. This paper gives the details of the data acquisition and conventional processing and then focuses on describing the new data at six individual sites along a transect across the gas hydrate zone. Five of the sites were drilled during the Expedition 311. The transect of sites commences at the almost undeformed incoming sediments seaward of the region where gas hydrates are observed; these ocean basin sediments were drilled at a site 40 km southeast during Ocean Drilling Program (ODP) Leg 146. The transect continues up the continental slope into the area of hydrate stability, with a site on top of the frontal accretionary ridge where normal faulting indicates margin parallel extension; a site in the first slope basin overlying a buried ridge near a reflectivity wipe-out zone; a site adjacent to Site 889 of Leg 146 and therefore acting as a tie hole; the most landward site at the shallowest end of the hydrate stability field; and a cold vent site at one of several blank zones close to a bright spot region in the seismic records

Gas hydrate concentration estimates from chlorinity, electrical resistivity and seismic velocity

Gas hydrate beneath the N. Cascadia continental slope off Vancouver Island occurs as a regional diffuse layer above the BSR and as local high concentrations in large vent or upwelling structures. Regional concentrations of gas hydrate beneath the N. Cascadia continental slope off Vancouver Island have been estimated earlier using multichannel seismic, seafloor electrical, and IODP Leg 146 downhole data. The concentrations of between 15 and 30% of pore saturation in a 100 m thick layer above the BSR are much higher than estimated elsewhere where there is good data, especially the Blake Ridge and central Cascadia off Oregon on ODP Leg 204. Although both of these other studies involved different sediment environments, a careful re-evaluation of the N. Cascadia estimates seemed desirable. We have re-evaluated the methods used to calculate the gas hydrate concentrations from pore-water chlorinity (salinity), electrical resistivity, and seismic velocity, describing in detail the assumptions and uncertainties. Use of the pore-water chlorinity/salinity and electrical resistivity directly have low reliability because of the effect on the no-hydrate reference of hydrate formation and dissociation, and the effect of pore fluid freshening by clay dehydration. At ODP Site 889/890 hydrate concentrations range from 5–10% to 30–40%, depending on the no-hydrate reference salinity used. Use of core salinity data along with the downhole and seafloor electrical resistivity data allows calculation of both the in situ reference salinity and the hydrate concentrations. The most important uncertainty in this method is the relation between resistivity and porosity, i.e., Archie’s Law parameters. Significantly different relations were determined from the ODP Leg 146 core and downhole log data, the log data resistivity-porosity relation giving much lower concentrations. Finally, seismic velocities from sonic-logs and multichannel data can be used to calculate gas hydrate concentrations, if an appropriate no-hydrate velocity-depth profile can be estimated. A velocity-hydrate concentration relation is also required. Depending on which no-hydrate/no-gas velocity baseline is used, estimated hydrate concentrations range from as low as 5% to above 25% saturation. In spite of having three nearly independent methods of estimating hydrate concentrations, it is concluded that the data allow regional concentrations in the 100 m layer above the BSR from less than 5% to over 25% saturation (3-13% of sediment volume). ODP drilling in the region scheduled for the fall of 2005 should help resolve the uncertainties

Wide angle seismic recordings from the 2002 Georgia Basin Geohazards Initiative, Northwestern Washington and British Columbia

This report describes the acquisition and processing of shallow-crustal wide-angle seismicreflection and refraction data obtained during a collaborative study in the Georgia Strait, western Washington and southwestern British Columbia. The study, the 2002 Georgia Strait Geohazards Initiative, was conducted in May 2002 by the Pacific Geoscience Centre, the U.S. Geological Survey, and the University of Victoria. The wide-angle recordings were designed to image shallow crustal faults and Cenozoic sedimentary basins crossing the International Border in southern Georgia basin and to add to existing wide-angle recordings there made during the 1998 SHIPS experiment. We recorded, at wide-angle, 800 km of shallow penetration multichannel seismic-reflection profiles acquired by the Canadian Coast Guard Ship (CCGS) Tully using an air gun with a volume of 1.967 liters (120 cu. in.). Prior to this reflection survey, we deployed 48 Refteks onshore to record the airgun signals at wide offsets. Three components of an oriented, 4.5 Hz seismometer were digitally recorded at all stations. Nearly 160,300 individual air gun shots were recorded along 180 short seismic reflection lines. In this report, we illustrate the wide-angle profiles acquired using the CCGS Tully, describe the land recording of the air gun signals, and summarize the processing of the land recorder data into common-receiver gathers. We also describe the format and content of the archival tapes containing the SEGY-formated, common-receiver gathers for the Reftek data. Data quality is variable but the experiment provided useful data from 42 of the 48 stations deployed. Three-fourths of all stations yielded useful first-arrivals to source-receiver offsets beyond 10 km: the average maximum source-receiver offset for first arrivals was 17 km. Six stations yielded no useful data and useful firstarrivals were limited to offsets less than 10 km at five stations. We separately archived our recordings of 86 local and regional earthquakes ranging in magnitude from 0.2 to 4.3 and 16 teleseisms ranging in magnitude 5.5 to 6.5

Data report: A downhole electrical resistivity study of northern Cascadia marine gas hydrate

Downhole electrical resistivity measurements can be exploited for gas hydrate concentration estimates. However, to do so requires that several assumptions be made, in particular about in situ pore water salinity and porosity. During Integrated Ocean Drilling Program Expedition 311, electrical resistivity was measured in four boreholes along a transect across the northern Cascadia margin, offshore Vancouver Island, Canada. Logging-while-rilling and conventional wireline logging data of resistivity, density, and neutron-porosity are used together with measurements of porosity and pore water salinity of the recovered core to systematically estimate gas hydrate concentrations at these four sites. Using Ar- chie’s law, empirical parameters a and m are determined from gas hydrate–free zones by means of a Pickett plot. The in situ salinity baseline trend for each site was estimated directly from the measured pore water salinity values, as well as indirectly by calculating the trend using Archie’s law and simultaneously solving for gas hydrate saturation and in situ salinity. Results showed that the in situ salinities at Sites U1325, U1326, and U1329 were well determined from a smooth trend through the highest measured salinity values of the recovered core. Only Site U1327 exhibitsstrongly decreasing pore water salinity, reaching 22‰ at the base of the gas hydrate stability field. This regional low salinity requires special analyses to estimate gas hydrate concentration from resistivity and introduces a large uncertainty. It is suggested that the decreased salinity results largely (90%) from a deeper fresh water source with the remaining freshening being the result of dissociation of pervasive gas hydrate (~3% of the pore space). Considering estimates from density porosity to be the most accurate, gas hydrate saturations average ~9% ± 7% at Site U1326, ~10% ± 7% at Site U1325, and 11% ± 7% at Site U1327 over the entire range of gas hydrate occurrence. No significant gas hydrate is inferred at Site U1329, although small am ounts may be present just above the bottom-simulating reflector. In two localized zones at Site U1326 (60–100 mbsf [meters below seafloor]) and Site U1327 (120–150 mbsf), significantly higher gas hydrate concentrations of >30% of the pore space were encountered

Open TURNS: An industrial software for uncertainty quantification in simulation

The needs to assess robust performances for complex systems and to answer tighter regulatory processes (security, safety, environmental control, and health impacts, etc.) have led to the emergence of a new industrial simulation challenge: to take uncertainties into account when dealing with complex numerical simulation frameworks. Therefore, a generic methodology has emerged from the joint effort of several industrial companies and academic institutions. EDF R&D, Airbus Group and Phimeca Engineering started a collaboration at the beginning of 2005, joined by IMACS in 2014, for the development of an Open Source software platform dedicated to uncertainty propagation by probabilistic methods, named OpenTURNS for Open source Treatment of Uncertainty, Risk 'N Statistics. OpenTURNS addresses the specific industrial challenges attached to uncertainties, which are transparency, genericity, modularity and multi-accessibility. This paper focuses on OpenTURNS and presents its main features: openTURNS is an open source software under the LGPL license, that presents itself as a C++ library and a Python TUI, and which works under Linux and Windows environment. All the methodological tools are described in the different sections of this paper: uncertainty quantification, uncertainty propagation, sensitivity analysis and metamodeling. A section also explains the generic wrappers way to link openTURNS to any external code. The paper illustrates as much as possible the methodological tools on an educational example that simulates the height of a river and compares it to the height of a dyke that protects industrial facilities. At last, it gives an overview of the main developments planned for the next few years

Gas hydrate on the northern Cascadia margin: regional geophysics and structural framework

Integrated Ocean Drilling Program Expedition 311 is based on extensive site survey data and historic research at the northern Cascadia margin since 1985. This research includes various regional geophysical surveys using a broad spectrum of seismic techniques, coring and logging by the Ocean Drilling Program Leg 146, heat flow measurements, shallow piston coring, and bottom video observations across a cold-vent field, as well as novel controlled-source electromagnetic and seafloor compliance surveying techniques. The wealth of data available allowed construction of structural cross-sections of the margin, development of models for the formation of gas hydrate in an accretionary prism, and estimation of gas hydrate and free gas concentrations. Expedition 311 established for the first time a transect of drill sites across the northern Cascadia margin to study the evolution of gas hydrate formation over the entire gas hydrate stability field of the accretionary complex. This paper reviews the tectonic framework at the northern Cascadia margin and summarizes the scientific studies that led to the drilling objectives of Expedition 311 Cascadia gas hydrate

Inside the tent: Community and government in refugee camps

Refugee camps are increasingly managed through a liberal rationality of government similar to that of many industrialized societies, with security mechanisms being used to optimize the life of particular refugee populations. This governmentality has encompassed programmes introduced by the United Nations High Commissioner for Refugees (UNHCR) and various non-governmental organizations (NGOs) to build and empower communities through the spatial technology of the camp. The present article argues that such attempts to ‘govern through community’ have been too easily dismissed or ignored. It therefore examines how such programmes work to produce, manage and conduct refugees through the use of a highly instrumentalized understanding of community in the spatial and statistical management of displaced people in camps. However, community is always both more and less than what is claimed of it, and therefore undermines attempts to use it as a governing tactic. By shifting to a more ontological understanding of community as unavoidable coexistence, inspired by Jean-Luc Nancy, we can see how the scripting of and government through community in camps is continually exceeded, redirected and resisted. Ethnographies of specific camps in Africa and the Middle East enable us both to see how the necessary sociality of being resists its own instrumentalization and to view the camp as a spatial security technology. Such resistance does not necessarily lead to greater security, but it redirects our attention to how community is used to conduct the behaviour of refugees, while also producing counter-conducts that offer greater agency, meaning and mobility to those displaced in camps

Multiple shades of grey: Opening the black box of public sector executives' hybrid role identities

Public sector reforms of recent decades in Europe have promoted managerialism and aimed at introducing private sector thinking and practices. However, with regard to public sector executives' self-understanding, managerial role identities have not replaced bureaucratic ones; rather, components from both paradigms have combined. In this article, we introduce a bi-dimensional approach (attitudes and practices) that allows for different combinations and forms of hybridity. Empirically, we explore the role identities of public sector executives across Europe, building on survey data from over 7,000 top public officials in 19 countries (COCOPS survey). We identify country-level profiles, as well as patterns across countries, and find that administrative traditions can account for these profiles and patterns only to a limited extent. Rather, they have to be complemented by factors such as stability of the institutional environment (indicating lower shares of hybrid combinations) or extent of reform pressures (indicating higher shares of hybrid combinations)