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91.
The trends in annual maximum rainfall (AMR) intensity data in New South Wales, Australia, were examined. Data from 60 stations were used covering three study periods, 1955–2010, 1965–2010 and 1978–2010. Mann-Kendall (MK) and Spearman’s rho (SR) tests were applied to assess trends at local stations. Pre-whitening (PW), trend-free pre-whitening (TFPW) and the variance correction (VC) tests were used to assess the effects of serial correlation on trend results. For regional trend analysis, the regional MK test was employed. The impacts of climatic variability modes on the observed trends in AMR intensity and seasonal maximum rainfall data were investigated. It was found that positive trends were more frequent than the negative ones. The PW, TFPW and VC tests resulted in a slight reduction in the count of stations exhibiting significant positive trends. The number of stations exhibiting significant trends decreased when the impact of climate variability modes was considered. 相似文献
92.
An excavation primarily intended to investigate the Bronze Age deposits at Hautrive‐Champréveyres, Neuchâtel, Switzerland, encountered beneath the Bronze Age levels a sequence of Late‐glacial sediments that were deposited between about 13000 yr BP and 11800 yr BP. Within these deposits Upper Palaeolithic hearths, bones and flint implements were found in a context that left no doubt that they accumulated on the actual living floors. Two separate cultures were involved; an earlier Magdalenian one overlain by a rather later Azilian assemblage. Coleoptera from the associated organic silts and sands provide detailed ecological and climatic information about the time when these people lived in the area. Radiocarbon dates indicate that the Magdalenians lived in the area at about 13000 yr BP. The Coleoptera show that the mean July temperature at this time was about 9°C and mean temperature of the coldest month was about −25°C. The landscape was bare of trees with an open patchy vegetation. Shortly after the area was abandoned by the Magdalenian hunters, the climate became suddenly warmer and mean July temperatures rose abruptly to at least 16°C and winter temperatures rose to levels not much different from those of the present day. There is evidence that at this time, intense slope instability and mud flows may have rendered the locality unsuitable for human occupation. About seven centuries after the episode of sudden climatic warming, namely at about 12300 yr BP, palaeolithic Azilian hunters occupied the area at a time when the climate was thoroughly temperate and the landscape was clothed in birch and willow woodland. This was gradually replaced by pine forest at the top of the sequence and Late‐glacial deposition ceased by about 11800 yr BP. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
93.
Geotectonics - The Low Folded Zone in Iraq is an active tectonic area witnessing different evidences for Neotectonic activities, among them are the lateral growth of Jambour, Pulkhana, and Qumar... 相似文献
94.
A probabilistic approach for the classification of earthquakes as ��triggered�� or ��not triggered��
Luigi Passarelli Francesco Maccaferri Eleonora Rivalta Torsten Dahm Elias Abebe Boku 《Journal of Seismology》2013,17(1):165-187
The occurrence time of earthquakes can be anticipated or delayed by external phenomena that induce strain energy changes on the faults. ??Anticipated?? earthquakes are generally called ??triggered??; however, it can be controversial to label a specific earthquake as such, mostly because of the stochastic nature of earthquake occurrence and of the large uncertainties usually associated to stress modelling. Here we introduce a combined statistical and physical approach to quantify the probability that a given earthquake was triggered by a given stress-inducing phenomenon. As an example, we consider an earthquake that was likely triggered by a natural event: the M?=?6.2 13 Jan 1976 Kópasker earthquake on the Grímsey lineament (Tj?rnes Fracture Zone, Iceland), which occurred about 3?weeks after a large dike injection in the nearby Krafla fissure swarm. By using Coulomb stress calculations and the rate-and-state earthquake nucleation theory, we calculate the likelihood of the earthquake in a scenario that contains only the tectonic background and excludes the dike and in a scenario that includes the dike but excludes the background. Applying the Bayes?? theorem, we obtain that the probability that the earthquake was indeed triggered by the dike, rather than purely due to the accumulation of tectonic strain, is about 60 to 90?%. This methodology allows us to assign quantitative probabilities to different scenarios and can help in classifying earthquakes as triggered or not triggered by natural or human-induced changes of stress in the crust. 相似文献
95.
96.
Fen ecosystem responses to water‐level fluctuations during the early and middle Holocene in central Europe: a case study from Wilczków,Poland 下载免费PDF全文
Mateusz Płóciennik Andrzej Kruk Jacek Forysiak Dominik Pawłowski Kamila Mianowicz Scott Elias Ryszard K. Borówka Marek Kloss Milena Obremska Marek Krąpiec Piotr Kittel Sławomir Żurek 《Boreas: An International Journal of Quaternary Research》2015,44(4):721-740
This paper presents a palaeoenvironmental reconstruction of the Wilczków fen (central Poland). The fen developed in an inactive valley at the onset of the Holocene (~11 ka BP) and peat accumulation lasted until 5.7 ka BP. Multi‐proxy reconstructions were made on the basis of palaeobotanical, cladoceran, chironomid, beetle and geochemical analyses. A Kohonen self‐organizing map (SOM, unsupervised artificial neural network) of the biotic sequence distinguished four stages of fen history. Stage X1 (11.0–10.7 ka BP) was relatively wet and cool. Organic matter started to accumulate but the habitat conditions remained unstable. Moss, sedge and fern communities then developed. Sedimentary changes reveal an intensive groundwater supply at that time. Numerous and diverse chironomid and cladoceran subfossils indicate nearly permanent aquatic conditions. During stage Y1 (10.6–9.2 ka BP) conditions were dry and the upper peat layer desiccated. Cladocera nearly disappeared whereas chironomids were represented by semi‐terrestrial and predatory (Tanypodinae) species. Conditions started to be more reducing. All the remaining samples belonged to the interweaving stages X2 and Y2. Stage Y2 (mostly 9.1–7.3 and 6.0–5.7 ka BP) was also dry but humidity increased towards the top. Oxidizing conditions occurred and the pH became more alkaline, favouring Cladium mariscus. The basin received mostly allochthonous matter input at that time. Stage X2 (mostly 6.8–6.1 ka BP) was humid and warm. The groundwater supply remained low but there was an increase in precipitation, changing local conditions to ombrotrophic. Species‐rich chironomid and cladoceran communities were associated with temporary pools. Finally, conditions returned to those characteristic of stage Y2. The presented reconstruction documents long‐term abiotic and biotic changes determined by water supply, including groundwater outflow, which have rarely been detected at a multi‐proxy scale. We show that inactivated valley fens are sensitive to climate‐driven hydrological fluctuations. Kohonen neural networks appear to be a promising method for analysing variability in multi‐proxy data. 相似文献
97.
Isotopic fingerprints of Milankovitch cycles in Pennsylvanian carbonate platform‐top deposits: the Valdorria record,Northern Spain 下载免费PDF全文
Valentin Chesnel Óscar Merino‐Tomé Luis Pedro Fernández Elisa Villa Elias Samankassou 《地学学报》2016,28(5):364-373
Sedimentary cyclic sequences deposited during the Late Palaeozoic Ice Age are widespread. Glacio‐eustatic control of the cyclic patterns is commonly accepted, and the durations of the cyclothems generally match the short‐ and long‐eccentricity Milankovitch orbital parameters. Nevertheless, geochemical fingerprints of orbital parameters are poorly documented in deep‐time sedimentary records. Here, we report on well‐exposed Bashkirian cyclothems of c. 123 ka and c. 400 ka durations from the Valdorria platform. The shorter‐term cyclothems can be grouped into longer‐term composite sequences that are consistent with generally accepted durations of c. 125 ka and c. 400 ka for Milankovitch eccentricity cycles. The stratigraphic pattern is mirrored by the isotope geochemical signals, which show distinct recurring trends. These trends are confirmed by statistical tests. Whereas intrinsic factors and/or subaerial exposure related to sea‐level lowstands might have truncated cycle patterns in tectonically stable basins, rapid subsidence of the Valdorria platform's foreland basin appears to have contributed to a faithful recording of cyclothems of different orders. The patterns and biostratigraphic constraint revealed in this study demonstrate the power of orbital forcing in imprinting sedimentary and geochemical signals in the rock record. 相似文献
98.
Predictability of the Meteorological Conditions Favourable to Radiative Fog Formation During the 2011 ParisFog Campaign 总被引:1,自引:1,他引:0
Laurent Menut Sylvain Mailler Jean-Charles Dupont Martial Haeffelin Thierry Elias 《Boundary-Layer Meteorology》2014,150(2):277-297
Radiative fog formation is a complex phenomenon involving local physical and microphysical processes that take place when particular meteorological conditions occur. This study aims at quantifying the ability of a regional numerical weather model to analyze and forecast the conditions favourable to radiative fog formation at an instrumental site in the Paris area. Data from the ParisFog campaign have been used in order to quantify the meteorological conditions favorable to radiative fog formation (pre-fog conditions) by setting threshold values on the key meteorological variables driving this process: 2-m temperature tendency, 10-m wind speed, 2-m relative humidity and net infrared flux. Data from the ParisFog observation periods of November 2011 indicate that use of these thresholds leads to the detection of 87 % of cases in which radiative fog formation was observed. In order to evaluate the ability of a regional weather model to reproduce adequately these conditions, the same thresholds are applied to meteorological model fields in both analysis and forecast mode. It is shown that, with this simple methodology, the model detects 74 % of the meteorological conditions finally leading to observed radiative fog, and 48 % 2 days in advance. Finally, sensitivity tests are conducted in order to evaluate the impact of using larger time or space windows on the forecasting skills. 相似文献
99.
Land use change scenarios and associated groundwater impacts in a protected peri-urban area 总被引:1,自引:1,他引:0
Land use changes in peri-urban areas are usually associated with significant impacts on groundwater resources due to alteration
of the recharge regime as well as through the establishment of pollution sources. Quantifying the aforementioned impacts and
assessing the vulnerability of the groundwater resources is an important step for the better management and protection of
the aquifers. In the present study, a physically based, distributed hydrologic model has been used to identify the impacts
from specific land use change scenarios in the protected area of Loutraki catchment. A vulnerability assessment method has
been also implemented to provide a decision support tool to the land planning authorities and also hydrologic mitigation measures
for the sustainable development of the area have been proposed. The hydrologic impacts of the land use scenarios include a
5% reduction in the annual recharge of the study aquifer for scenario 1 (doubling of the current urban areas) and 7% decrease
for scenario 2 (tripling of the current urban areas). Nevertheless, these impacts can be minimised if small-scale artificial
recharge infrastructure is developed and the land planning measures suggested through the vulnerability and recharge maps
will be followed. 相似文献
100.
Till Heinrichs Elias Salameh Hani Khouri 《International Journal of Earth Sciences》2014,103(1):233-252
The deeply eroded Waqf as Suwwan ring structure was recently discovered to be a large impact, the first identified in the near east. Large-scale reflection seismic structure shows the impact situated high on the northeastern flank of the Jordan Uplift sloping into Wadi Sirhan Basin. If exhumation is linked to the Arabia–Eurasia collision, a likely time window for the impact event may be latest Eocene to Late Oligocene. Impact into a shallow sea seems an optional scenario. Old reflection seismic lines offer limited insight into the deep structure of the rim and part of the central uplift of the complex crater. An important structural clue is provided by a well-resolved seismic horizon of a yet tentative correlation with a Paleozoic black shale. The central gravity high is compatible with a mass surplus by the uplift of denser Paleozoic basement below the central uplift. The gravity model further indicates a ring of dense Paleozoic sediments rising from below into the ring syncline. Seismics show presumably radial synclines in the central uplift which are interpreted by centripetal constrictional flow during crater collapse. Beneath the final crater’s outer boundary, a shallow-dip normal fault zone, subtle seismic structure in uncollapsed footwall segments reveal an asymmetry of strain. The asymmetry is attributed to the cratering flow by an oblique impact directed toward NE. The finding provides independent support to an earlier suggestion of impact obliquity based on vergency of folds exposed on the central uplift. 相似文献