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991.
Chen Kuang-Jung Chiu Bonbbon Wang Jee-Shiang Lee Cheng-Yu Lin Cheng-Horng Chao Kevin 《Natural Hazards》2011,58(3):1233-1252
A strong earthquake with a magnitude of 7.6 (M
L
= 7.3) occurred on September 21, 1999, in central Taiwan. In order to discern any potential precursors before this earthquake,
geomagnetic data at Lunping (LNP), Taiwan, Geomagnetic Observatory situated 100 km from the epicenter are examined using two
methods, i.e., the traditional induction arrows and complex demodulation. Our results show that the remarkable temporal variation
of real induction arrows appear to be strong prior to the great earthquake over the previous 24 months. After the great earthquake,
the magnitudes of induction arrows decreased to the normal (mean of 8 years) levels. In other words, the direction of real
induction arrows of the periods 30 and 20 min rotated 85° and 40° anticlockwise, respectively, before the Chi-Chi earthquake
and returned to mean direction of last 10 years after the earthquake. A horizontal source field model using the finite difference
method for 3-D shows that the variation of the real induction arrows might be ascribed to the conductivity variation body,
which is 5 km buried at the epicenter area of the Chi-Chi earthquake, changing its conductivity from 0.002S/m to 0.06 S/m.
The ratios of modulus (demodulated by using the complex demodulation method) over a period 12, and 8 h relative to the period
of 24 h reveal a remarkable change that appeared 4–5 months prior to this strong earthquake. They increased gradually from
the beginning of 1999 to August 1999 and decreased again to a (8 years) mean level after the strong earthquake occurrence.
We consider that the variation of the induction arrow might be ascribed to the conductivity anomaly, which is buried 5 km
at the south-east side of LNP with a conductivity change of 0.06 S/m. We propose that this elevation might be related to the
preparation process of the great earthquake. 相似文献
992.
Kevin P. Norton Friedhelm von Blanckenburg Roman DiBiase Fritz Schlunegger Peter W. Kubik 《International Journal of Earth Sciences》2011,100(5):1163-1179
Denudation rates from cosmogenic 10Be measured in quartz from recent river sediment have previously been used in the Central Alps to argue that rock uplift occurs
through isostatic response to erosion in the absence of ongoing convergence. We present new basin-averaged denudation rates
from large rivers in the Eastern and Southern European Alps together with a detailed topographic analysis in order to infer
the forces driving erosion. Denudation rates in the Eastern and Southern Alps of 170–1,400 mm ky−1 are within a similar range to those in the Central Alps for similar lithologies. However, these denudation rates vary considerably
with lithology, and their variability generally increases with steeper landscapes, where correlations with topographic metrics
also become poorer. Tertiary igneous rocks are associated with steep hillslopes and channels and low denudation rates, whereas
pre-Alpine gneisses usually exhibit steep hillslopes and higher denudation rates. Molasse, flysch, and schists display lower
mean basin slopes and channel gradients, and, despite their high erodibility, low erosion rates. Exceptionally low denudation
rates are also measured in Permian rhyolite, which has high mean basin slopes. We invoke geomorphic inheritance as a major
factor controlling erosion, such that large erosive glaciers in the late Quaternary cold periods were more effective in priming
landscapes in the Central Alps for erosion than in the interior Eastern Alps. However, the difference in tectonic evolution
of the Eastern and Central Alps potentially adds to differences in their geomorphic response; their deep structures differ
significantly and, unlike the Central Alps, the Eastern Alps are affected by ongoing tectonic influx due to the slow motion
and rotation of Adria. The result is a complex pattern of high mountain erosion in the Eastern Alps, which has evolved from
one confined to the narrow belt of the Tauern Window in late Tertiary time to one affecting the entire underthrust basement,
orogenic lid, and parts of the Southern Alps today. 相似文献
993.
Extensive, large-scale pervasive cementation in the form of cement bodies within fluvial strata has rarely been documented although fluvial strata commonly act as important hydrocarbon reservoirs, as well as groundwater aquifers. Here, we present outcrop, petrographic and geochemical data for pervasive ferroan dolomite cement bodies up to 250 m in size from Upper Cretaceous Desert Member and Castlegate Sandstone fluvial strata exposed in the Book Cliffs in Utah. These cement bodies are present with coastal plain fluvial strata within both the Desert and Castlegate lowstand sandstones and are most abundant in the thin, distal fluvial strata. Cement bodies are almost entirely absent in updip, thicker, fluvial strata. Petrographic observations suggest a predominantly early diagenetic timing to the mildly ferroan dolomite, with a component of later burial origin. δ13C values for the cement (+4.8 to −5.7‰ V-PDB) suggest a marine-derived source for the earliest phase with a burial organic matter source for later cement. δ18O data (−6.3 to −11.8‰ V-PDB) suggest precipitation from freshwater dominated fluids. It is proposed here that dolomite was derived from leaching of detrital dolomite under lowstand coals and cementation took place in coastal aquifers experiencing mixed meteoric-marine fluids as a result of base-level fluctuations. This data presented here shows that large cement bodies can be an important component within fluvial sandstones with a potentially significant impact upon both reservoir quality and fluid flow within reservoirs, especially at the marine-non-marine interface. 相似文献
994.
Anne-Carlijn Alderkamp Véronique GarconHein J.W. de Baar Kevin R. Arrigo 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(9):943-955
We assessed whether short-term photoacclimation responses of natural phytoplankton populations in the Drake Passage (Southern Ocean) were affecting protection from photodamage as cells are mixed up to the surface from depth. To this end, we measured phytoplankton fluorescence characteristics and their ratio of xanthophyll cycle pigment to photosynthetic pigments within the upper mixed layer (UML) and in short-term deck incubation experiments. Phytoplankton within the UML photoacclimated by increasing their ratio of xanthophyll cycle (diadinoxanthin [dd] and diatoxanthin [dt]) pigments to chlorophyll a. The photoacclimation processes observed within the UML did, however, not influence the protection of phytoplankton from photodamage during short-term near-surface irradiance experiments. Exposure to near-surface irradiance resulted in photodamage in all experiments, regardless of the phytoplankton community composition and irradiance levels. Incubating phytoplankton for six hours at either 2% or 50% of surface irradiance prior to exposure to near-surface irradiance did not alter the photodamage characteristics. This suggests that short-term photoacclimation processes within the UML are not adequate to protect phytoplankton from photodamage when cells are mixed up to the surface from depth, and that repair of damaged photosystems is crucial for maintaining photosynthesis under fluctuating irradiance conditions, even at very low mean irradiance levels. Likely, continuously operating photoacclimation processes offset to some extent the negative effects of photodamage on photosynthetic performance, albeit with increased metabolic costs. 相似文献
995.
Laura?CunninghamEmail author Kevin?Bishop Eva?Mett?vainio Peter?Rosén 《Journal of Paleolimnology》2011,45(4):507-518
A decade of widespread increases in surface water concentrations of total organic carbon (TOC) in some regions has raised
questions about longer term patterns in this important constituent of water chemistry. This study uses near-infrared spectroscopy
(NIRS) to infer lake water TOC far beyond the decade or two of observational data generally available. An expanded calibration
dataset of 140 lakes across Sweden covering a TOC gradient from 0.7 to 24.7 mg L−1 was used to establish a relationship between the NIRS signal from surface sediments (0–0.5 cm) and the TOC concentration
of the water mass. Internal cross-validation of the model resulted in an R
2 of 0.72 with a root mean squared error of calibration (RMSECV) of 2.6 mg L−1. The TOC concentrations reconstructed from surface sediments in four Swedish lakes were typically within the range of concentrations
observed in the monitoring data during the period represented by each sediment layer. TOC reconstructions from the full sediment
cores of four lakes indicated that TOC concentrations were approximately twice as high a century ago. 相似文献
996.
As a consequence of changing immigration policy over the past 50 years, contemporary Australia has a culturally diverse population. Focusing on Brisbane, one of Australia's smaller immigrant-receiving cities but where some 19 per cent of the population is born overseas, this study examines attitudes to and perceptions of culturally different ethnic (non-Anglo) immigrant groups. Emphasis is placed on patterns of tolerance and intolerance for the city as a whole, both in areas of contact and in areas of minimal contact. Findings show that variations in attitudes vary somewhat from commonly accepted socio-economic and age-based correlations (the lower the status or the older people are the less tolerant), depending on the particular mix of ethnic birthplace groups present. They also show levels of intolerance in areas of minimal contact, which is implicitly attributed to mass media influences. In light of these findings, a concluding plea is made for anti-intolerance strategies to be developed for cities that pay regard to the geography of attitude-forming contexts. 相似文献
997.
Horsburgh Kevin Haigh Ivan D. Williams Jane De Dominicis Michela Wolf Judith Inayatillah Addina Byrne David 《Ocean Dynamics》2021,71(6-7):715-730
Ocean Dynamics - In this paper, we show that over the next few decades, the natural variability of mid-latitude storm systems is likely to be a more important driver of coastal extreme sea levels... 相似文献
998.
Stéphane Le Mouélic Pascal Rannou Sébastien Rodriguez Christophe Sotin Caitlin A. Griffith Lucille Le Corre Jason W. Barnes Robert H. Brown Kevin H. Baines Bonnie J. Buratti Roger N. Clark Philip D. Nicholson Gabriel Tobie 《Planetary and Space Science》2012,60(1):86-92
Saturn's Moon Titan has a thick atmosphere with a meteorological cycle. We report on the evolution of the giant cloud system covering its north pole using observations acquired by the Visual and Infrared Mapping Spectrometer onboard the Cassini spacecraft. A radiative transfer model in spherical geometry shows that the clouds are found at an altitude between 30 and 65 km. We also show that the polar cloud system vanished progressively as Titan approached equinox in August 2009, revealing at optical wavelengths the underlying sea known as Kraken Mare. This decrease of activity suggests that the north-polar downwelling has begun to shut off. Such a scenario is compared with the Titan global circulation model of Rannou et al. (2006), which predicts a decrease of cloud coverage in northern latitudes at the same period of time. 相似文献
999.
1000.
Community readiness for a new tsunami warning system: quasi-experimental and benchmarking evaluation of a school education component 总被引:2,自引:2,他引:0
Youth preparedness for disasters is a growing area of research. However, studies to date have relied on cross-sectional, correlational
research designs. The current study replicated aspects of the one other study to date that has used a quasi-experimental strategy
to evaluate youth preparedness for disasters. This study evaluated whether children were more knowledgeable and prepared for
hazards generally but also in more specific relation to the rollout of a new tsunami warning system. Using a pretest–posttest
with benchmarking design, the study found that following a brief school education program, supplementing a larger community-wide
effort, children reported significant gains in preparedness indicators including increased knowledge as well as increases
in physical and psychosocial preparedness. Within group effect sizes compared favorably with those from the previous experimental
study in this area used to benchmark current intervention-produced findings and produced hints that combining school education
programs with larger community preparedness efforts can enhance preparedness. Given that this is only one of two experimentally-based
studies in an area of research largely dominated by cross-sectional designs, future research should consider the use of experimental
designs, including those that are pragmatic and fit with needs of the school. The current approach has limitations that need
to be considered. However, it also has some real advantages, including being used more extensively in fieldwork studies that
evaluate various types of interventions. Through increased use of experimental design strategies, researchers can then also
have increased confidence that educational programs are the source of increases in disaster resilience in youth and their
families. 相似文献