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71.
Elisabeth A. Parfitt Tracy K. P. Gregg Deborah K. Smith 《Journal of Volcanology and Geothermal Research》2002,113(1-2)
Eruption styles on the subaerial East Rift Zone (ERZ) of Kilauea volcano are reviewed and a classification scheme for the different types of eruption is proposed. The various eruption types are produced by differing thermal and driving pressure behaviour in the feeder dikes. Existing evidence is reviewed and new evidence presented of the types and volumes of eruptions on the Puna Ridge, which is the submarine extension of the ERZ. Eruptions on the Puna Ridge fall into the same five classes as, and are of comparable volume to, those on the subaerial ERZ. Evidence is presented which suggests that feeder dikes for Puna Ridge eruptions are more thermally viable than those feeding subaerial eruptions, and this difference causes long-lived, large-volume eruptions to be more common on the Puna Ridge than on the subaerial ERZ. This systematic variation in thermal viability may be due to increased dike width for Puna Ridge dikes or increased pressure gradients driving magma flow. Lateral dike emplacement is common to many basaltic systems including on other Hawaiian volcanoes, in Iceland and at mid-ocean ridges. The systematic trend inferred for the ERZ of Kilauea implies that in the other systems large-volume eruptions may also be more common at great distances than they are close to the magma centre. 相似文献
72.
Sebastiano Foti Fabrice Hollender Flora Garofalo Dario Albarello Michael Asten Pierre-Yves Bard Cesare Comina Cécile Cornou Brady Cox Giuseppe Di Giulio Thomas Forbriger Koichi Hayashi Enrico Lunedei Antony Martin Diego Mercerat Matthias Ohrnberger Valerio Poggi Florence Renalier Deborah Sicilia Valentina Socco 《Bulletin of Earthquake Engineering》2018,16(6):2367-2420
Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the VS,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data. 相似文献
73.
This paper investigates the transferability of calibrated HBV model parameters under stable and contrasting conditions in terms of flood seasonality and flood generating processes (FGP) in five Norwegian catchments with mixed snowmelt/rainfall regimes. We apply a series of generalized (differential) split-sample tests using a 6-year moving window over (i) the entire runoff observation periods, and (ii) two subsets of runoff observations distinguished by the seasonal occurrence of annual maximum floods during either spring or autumn. The results indicate a general model performance loss due to the transfer of calibrated parameters to independent validation periods of ?5 to ?17%, on average. However, there is no indication that contrasting flood seasonality exacerbates performance losses, which contradicts the assumption that optimized parameter sets for snowmelt-dominated floods (during spring) perform particularly poorly on validation periods with rainfall-dominated floods (during autumn) and vice versa. 相似文献
74.
Li-Shan?HuangEmail authorView authors OrcID profile Deborah?A.?Cory-Slechta Christopher?Cox Sally?W.?Thurston Conrad?F.?Shamlaye Gene?E.?Watson Edwin?van Wijngaarden Grazyna?Zareba J.?J.?Strain Gary?J.?Myers Philip?W.?Davidson 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(4):893-904
The Seychelles Child Development Study has been examining the relationship between prenatal methylmercury (MeHg) exposure from consuming fish during pregnancy and child development. This study re-analyzes seven outcomes in the 17 year Main Cohort data to determine if there are nonlinear or non-homogeneous (subgroup) associations that were not identified in the linear analysis. We adopted two statistical approaches. First, we carried out an additive nonlinear analysis assuming homogeneous prenatal MeHg-outcome relationships to explore overall associations. Second, we applied the regression tree to the Woodcock–Johnson Calculation subtest (it was significantly associated in earlier analyses) and identified 4 clusters based on covariates. Then we used additive models to assess the prenatal MeHg association in each of the four clusters for all seven outcomes. This approach assumes nonlinear associations in each cluster and non-homogeneous associations between clusters. The additive nonlinear analysis yielded prenatal MeHg curves similar to the linear analysis. For the regression tree analysis, the curves relating prenatal MeHg to outcomes between the 4 clusters differed and some crossed at higher prenatal MeHg levels, suggesting non-homogeneity in the upper range of exposure. Additionally, some of the curves suggested a possible non-linear relationship within the range of exposure we studied. This non-linear analysis supports the findings from the linear analysis. It shows little evidence to support an adverse association of prenatal MeHg exposure through maternal consumption of fish contaminated with natural background levels. However, the tree analysis suggests that the prenatal exposure/outcome relationship may not be homogeneous across all individuals and that some subpopulations may have an adverse association in the upper range of the exposures studied. More robust data in the higher levels of exposure in this cohort are needed to confirm this finding. 相似文献
75.
76.
A regional climate model is used to investigate the mechanism of interdecadal rainfall variability, specifically the drought
of the 1970s and 1980s, in the Sahel region of Africa. The model is the National Center for Environmental Prediction’s (NCEPs)
Regional Spectral Model (RSM97), with a horizontal resolution of approximately equivalent to a grid spacing of 50 km, nested
within the ECHAM4.5 atmospheric general circulation model (AGCM), which in turn was forced by observed sea surface temperature
(SST). Simulations for the July–September season of the individual years 1955 and 1986 produced wet conditions in 1955 and
dry conditions in 1986 in the Sahel, as observed. Additional July–September simulations were run forced by SSTs averaged for
each month over the periods 1950–1959 and the 1978–1987. These simulations yielded wet conditions in the 1950–1959 case and
dry conditions in the 1978–1987 case, confirming the role of SST forcing in decadal variability in particular. To test the
hypothesis that the SST influences Sahel rainfall via stabilization of the tropospheric sounding, simulations were performed
in which the temperature field from the AGCM was artificially modified before it was used to force the regional model. We
modified the original 1955 ECHAM4.5 temperature profiles by adding a horizontally uniform, vertically varying temperature
increase, taken from the 1986–1955 tropical mean warming in either the AGCM or the NCEP/National Center for Atmospheric Research
Reanalysis. When compared to the 1955 simulations without the added tropospheric warming, these simulations show a drying
in the Sahel similar to that in the 1986–1955 difference and to the decadal difference between the 1980s and 1950s. This suggests
that the tropospheric warming may have been, at least in part, the agent by which the SST increases led to the Sahel drought
of the 1970s and 1980s. 相似文献
77.
Climate change and population history in the Pacific Lowlands of Southern Mesoamerica 总被引:1,自引:0,他引:1
Hector Neff Deborah M. Pearsall John G. Jones Brbara Arroyo de Pieters Dorothy E. Freidel 《Quaternary Research》2006,65(3):390-400
Core MAN015 from Pacific coastal Guatemala contains sediments accumulated in a mangrove setting over the past 6500 yr. Chemical, pollen, and phytolith data, which indicate conditions of estuarine deposition and terrigenous inputs from adjacent dry land, document Holocene climate variability that parallels the Maya lowlands and other New World tropical locations. Human population history in this region may be driven partly by climate variation: sedentary human populations spread rapidly through the estuarine zone of the lower coast during a dry and variable 4th millennium B.P. Population growth and cultural florescence during a long, relatively moist period (2800–1200 B.P.) ended around 1200 B.P., a drying event that coincided with the Classic Maya collapse. 相似文献
78.
Michael?W.?LomasEmail author T.?Mark Trice Patricia?M.?Glibert Deborah?A.?Bronk James?J.?McCarthy 《Estuaries and Coasts》2002,25(3):469-482
We examined the temporal and spatial variability of urea concentrations and urea uptake and regeneration rates collected on cruises along the longitudinal axis of the Chesapeake Bay between 1972 and 1998. Interannually, mean Bay-wide surface urea concentrations ranged between 0.49 and 0.91 μg-at N l?1 with a nearly 50% decrease in surface concentrations observed between 1988 and 1998. Concentrations of urea from samples collected within ~1 m of the bottom were generally higher and much more varable than surface samples. Seasonally, two different patterns were observed in mean Bay-wide surface urea concentrations. Urea concentrations from near surface waters exhibited a clear summer peak for 1988 through 1994, while for 1973 and 1996 to 1998 a distinct winter-spring peak in concentration was observed. Urea concentrations from deeper waters showed a similar seasonal trend each year with peak concentrations measured in spring. Spatially, urea concentrations in the surface waters decreased in a conservative-type pattern from 0.91 μg-at N I?1 at the freshwater end member to 0.46 μg-at N I?1 at the ocean end member. Mean Bay-wide surface urea uptake rates displayed a seasonal pattern throughout the data set with maximum uptake rates (up to 0.33 μg-at N I?1 h?1) consistently observed during summer. Mean Bay-wide surface regeneration rates were highest but most variable during fall (1.63±0.82 μg-at N I?1 h?1). Mean urea uptake and regeneration rates displayed opposing spatial trends along the axis of the Bay with uptake rates being lowest in the North Bay where regeneration rates were highest. The average temporal and spatial patterns of urea concentration in Chesapeake Bay appear to reflect a balance between external inputs and internal biological recycling. 相似文献
79.
For qualitative researchers, selecting appropriate sites in which to conduct interviews may seem to be a relatively simple research design issue. In fact it is a complicated decision with wide‐reaching implications. In this paper, we argue that the interview site itself embodies and constitutes multiple scales of spatial relations and meaning, which construct the power and positionality of participants in relation to the people, places, and interactions discussed in the interview. We illustrate how observation and analysis of interview sites can offer new insights with respect to research questions, help researchers understand and interpret interview material, and highlight particular ethical considerations that researchers need to address. 相似文献
80.
Morgan T. Jones Deborah J. Hembury Martin R. Palmer Bill Tonge W. George Darling Susan C. Loughlin 《Bulletin of Volcanology》2011,73(3):207-222
The eruptions of the Soufrière Hills volcano on Montserrat (Lesser Antilles) from 1995 to present have draped parts of the
island in fresh volcaniclastic deposits. Volcanic islands such as Montserrat are an important component of global weathering
fluxes, due to high relief and runoff and high chemical and physical weathering rates of fresh volcaniclastic material. We
examine the impact of the recent volcanism on the geochemistry of pre-existing hydrological systems and demonstrate that the
initial chemical weathering yield of fresh volcanic material is higher than that from older deposits within the Lesser Antilles
arc. The silicate weathering may have consumed 1.3% of the early CO2 emissions from the Soufrière Hills volcano. In contrast, extinct volcanic edifices such as the Centre Hills in central Montserrat
are a net sink for atmospheric CO2 due to continued elevated weathering rates relative to continental silicate rock weathering. The role of an arc volcano as
a source or sink for atmospheric CO2 is therefore critically dependent on the stage it occupies in its life cycle, changing from a net source to a net sink as
the eruptive activity wanes. While the onset of the eruption has had a profound effect on the groundwater around the Soufrière
Hills center, the geochemistry of springs in the Centre Hills 5 km to the north appear unaffected by the recent volcanism.
This has implications for the potential risk, or lack thereof, of contamination of potable water supplies for the island’s
inhabitants. 相似文献