Some relationships between VAN Seismic Electric Signals (SES) and earthquake parameters: Study for the 1995–2007 period     

Elisabeth Dologlou 《Acta Geophysica》2008,56(4):1015-1024

A 12-year period experimental data, from 1 January 1995, to 20 August 2007, have been examined for possible correlations between Seismic Electric Signals (SES) of the VAN method and source parameters of the corresponding earthquakes in Western Greece. During that period 13 earthquakes of magnitude M _W ≥ 5 with epicenters in the area 19–24°E, 36–41°N and available the CMT solutions (Centroid Moment Tensor focal mechanism solutions) have been found to be preceded by a SES each time at one of the three VAN stations of IOA, PIR or PAT. The results of IOA and PIR stations are compared to those reported by Uyeda et al. 1999, for the previous period 1983–1994. The IOA station seems to be sensitive to earthquakes with thrust type mechanisms being mainly consistent to its past behavior. The PIR station, which is moved from its previous position by few kilometers, exhibits some changes. It detects now both strike slip and thrust type earthquakes and becomes sensitive to new areas indicating probably the strong dependence of the SES station detection ability upon its location.  相似文献   

Dispersal,survival and delayed growth of benthic foraminiferal propagules     

Elisabeth Alve  Susan T. Goldstein 《Journal of Sea Research》2010,63(1):36-51

New data support our previously published propagule dispersal hypothesis and show that propagules of some benthic foraminiferal species can survive for two years before growth commences. Following exposure to simulated shallow-water conditions, shallow-water species of benthic foraminifera appeared and grew in large numbers (commonly >100 ind/12 ml sediment) in the <32 µm-size sediment fraction collected from 320 m water depth in the Skagerrak basin (North Sea). None of the shallow-water species that grew abundantly (Planorbulina mediterranensis, Morulaeplecta bulbosa, Bolivina pseudoplicata, Cuneata arctica, Eggerelloides scaber, Gavelinopsis praegeri) seem to grow or reproduce at or in the vicinity of the sampling site. Consequently, they must have been transported there as <32 µm-sized individuals. Their sudden appearance when exposed to shallow-water conditions suggests that they had been transported to the sampling site as propagules and that they could survive in the sediments until conditions became suitable for growth and, for some, reproduction. The lack of agglutination on the proloculi of the agglutinated taxa that appeared in the growth-chambers may enhance their passive transport via currents and, thereby, dispersal. Of all the indigenous foraminiferal species that occur at the sampling site, only Textularia earlandi and Bolivinellina pseudopunctata continued to grow and reproduce when transferred from bathyal (320 m) to simulated shallow-water (0 m) conditions. The former is considered a highly opportunistic species. According to the literature, most of the morphospecies which grew in the experiments are cosmopolitan. Our results indicate substantial inter-specific differences in dispersal potential and support previous suggestions that among free-living species, some serial forms have the potential for long-distance dispersal. Still, oceanographic, physical and ecological boundaries and barriers constrain the distribution of most species. In addition to benthic foraminifera, Gromia spp. (rhizarian protists related to the foraminifera) grew in >60% of the experimental growth-chambers.  相似文献   

Length of phytoplankton species patches on the Southern California Shelf     

Richard W. Eppley  Freda M.H. Reid  Elisabeth Stewart 《Continental Shelf Research》1984,3(3):259-266

Study of a longshore transect off Southern California suggests that the length scales (22 to 27 km) of phytoplankton species patches may be related to those of low-frequency currents. The patch boundaries were independent of shelf width but they were probably not independent of changes in chlorophyll fluorescence, temperature, and bottom topography.  相似文献   

Preliminary Archaeomagnetic Results from a Floor Sequence of a Bread Kiln in Lübeck (Germany)     

Schnepp  Elisabeth  Pucher  Rudolf 《Studia Geophysica et Geodaetica》1998,42(1):1-11

A sequence of 25 bread-kiln floors was sampled for archaeomagnetic measurements in a bakehouse in the old town of Lübeck, Germany. Due to archaeological dating this kiln floor sequence has been built up presumably from the late 13 ^th to the 18 ^th century. The primary magnetisation component is carried by magnetite (maghemite) and is very stable. Small viscous magnetisation components could be removed easily. The preliminary results of characteristic remanent magnetisation for 23 of the kiln-floor layers show clearly the trend of the geomagnetic secular variation expected for that time interval. By comparison with French and British master curves, the kiln-floor sequence started around 1425 and lasted until 1775 AD. Presently, confidence circles are relatively large and need refineing by measuring more samples, which have already been collected. Together with ¹⁴ C dating that can be determined from the charcoals found in the lowest layers and thermoluminescence dating of the layers, we expect to obtain, for the first time, a secular variation curve for Northern Germany covering the time interval from 1400 to 1800 years AD.  相似文献   

Reducing climate risk for micro-insurance providers in Africa: A case study of Ethiopia     

Elisabeth Meze-Hausken  Anthony Patt  Steffen Fritz 《Global Environmental Change》2009,19(1):66-73

Recurrent climate hazards challenge subsistence farmers in developing countries. Reliance on various diversification strategies and traditional risk sharing among kin and families has serious limitations, such as the problem of covariate risk within such networks. Index-based crop insurance could help to reduce people's climate-related risk, but raising the necessary capital to make insurance schemes financially secure is difficult for micro-insurance providers. We examine the extent to which spatial pooling of micro-insurance schemes could reduce these capital requirements. We simulate a hypothetical insurance market operating in Ethiopia, using rainfall data and yield estimates for 15 stations. By performing a Monte Carlo analysis, risk capital required to keep the probability of financial ruin below a threshold value is identified. We investigate the marginal benefits of pooling increasing numbers of sites, as well as the relationship between the benefits of pooling and the spatial covariance of rainfall. We find spatial diversification to offer considerable savings in required capitalization with as few as three sites pooled, as well as a weak but significant relationship between rainfall covariance and those benefits. The results suggest that spatial pooling may be an attractive option for micro-insurers, worthy of a detailed case-by-case analysis when designing index-insurance schemes.  相似文献   

Space observations of Transient Luminous Events and associated emissions in the upper atmosphere above thunderstorm areas     

Elisabeth Blanc 《Comptes Rendus Geoscience》2010,342(4-5):312-322

Sprites, jets and elves called Transient Luminous Events (TLE), observed in the middle and upper atmosphere above thunderstorms, are the manifestation of intense energy exchanges between the troposphere, stratosphere and mesosphere. Different types of luminous emissions have been identified by ground-based observations, showing the complexity of these phenomena. Space missions showed that transient emissions in the Earth atmosphere are very broad including Radio Frequency (RF), IR to FUV radiations and X-gamma ray emissions called Terrestrial Gamma Flashes (TGF) with energies reaching 30 Mev. However, there are no global observations of these events together. This paper reviews space observations performed up to now and emphasizes the challenges of the future space missions in global measurements of all possible emissions together for the understanding of the physical mechanisms at the origin of these phenomena and their effects on the Earth environment.  相似文献   

Performance of the ensemble Kalman filter outside of existing wells for a channelized reservoir     

Elisabeth Peters 《Computational Geosciences》2011,15(2):345-358

The ensemble Kalman filter (EnKF) appears to give good results for matching production data at existing wells. However, the predictive power of these models outside of the existing wells is much more uncertain. In this paper, for a channelized reservoir for five different cases with different levels of information the production history is matched using the EnKF. The predictive power of the resulting model is tested for the existing wells and for new wells. The results show a consistent improvement for the predictions at the existing wells after assimilation of the production data, but not for prediction of production at new well locations. The latter depended on the settings of the problem and prior information used. The results also showed that the fit during the history match was not always a good predictor for predictive capabilities of the history match model. This suggests that some form of validation outside of observed wells is essential.  相似文献   

Ten guiding principles for the delineation of priority habitat for endangered small cetaceans     

Peter S. Ross  Jay Barlow  Thomas A. Jefferson  Brendan E. Hickie  Tatiana Lee  Christina MacFarquhar  E. Christien Parsons  Kimberly N. Riehl  Naomi A. Rose  Elisabeth Slooten  Chia-Yang Tsai  John Y. Wang  Andrew J. Wright  Shih Chu Yang 《Marine Policy》2011

The adoption of endangered species laws in various nations has intensified efforts to better understand, and protect, at-risk species or populations, and their habitats. In many countries, delineating a portion of a species' habitat as particularly worthy of protection has become a mantra of these laws. Unfortunately, the laws themselves often provide scientists and managers with few, if any, guidelines for how to define such habitat. Conservationists and scientists may view protecting part of the habitat of an endangered species as an ineffectual compromise, while managers may be under pressure to allow a range of human activities within the species' habitat. In the case of small cetaceans, establishing boundaries for such areas can also be complicated by their mobility, the fluid nature of their environment, and the often ephemeral nature of their habitat features. The convergence of multiple human impacts in coastal waters around the world is impacting many small cetaceans (and other species) that rely on these areas for feeding, reproducing, and resting. The ten guiding principles presented here provide a means to characterize the habitat needs of small, at-risk cetaceans, and serve as a basis for the delineation of ‘priority habitat’ boundaries. This conceptual approach should facilitate a constructive discourse between scientists and managers engaged in efforts to recover endangered species. The degree to which the recovery of an at-risk species can be reconciled with sustainable economic activity will depend in part on how well these principles are incorporated into the delineation of priority habitat.  相似文献   

Possible evidence for on-going volcanism on Mars as suggested by thin, elliptical sheets of low-albedo particulate material around pits and fissures close to Cerberus Fossae     

Gerald Patrick Roberts  Ian A. Crawford  David Peacock  Joyce Vetterlein  Elisabeth Parfitt  Louise Bishop 《Earth, Moon, and Planets》2007,100(1-2):1-16

High quality CCD images obtained at two different observatories in North Italy allowed the identification of four morphological structures near the nuclear region of the comet Ikeya-Zhang (I-Z): haloes, jets, shells and spirals. The interpretation of the nature of these structures has been attempted by means of a comparison of different up-to-date image processing techniques, which led to a single common estimate of the rotation period (p=1.48±0.20 days).  相似文献   

Interpretation of Na–Cl–Br Systematics in Sedimentary Basin Brines: Comparison of Concentration, Element Ratio, and Isometric Log-ratio Approaches     

Mark A. Engle  Elisabeth L. Rowan 《Mathematical Geosciences》2013,45(1):87-101

Mathematicians and geochemists have long realized that compositional data intrinsically exhibit a structure prone to spurious and induced correlations. This paper demonstrates, using the Na–Cl–Br system, that these mathematical problems are exacerbated in the study of sedimentary basin brines by such processes as the evaporation or dissolution of salts owing to their high salinities. Using two published datasets of Na–Cl–Br data for fluids from the Appalachian Basin, it is shown that log concentration and Na/Br versus Cl/Br methods for displaying solute chemistry may lead to misinterpretation of mixing trends between meteoric waters (for example shallow drinking water aquifers) and basinal brines, partially due to spurious mathematical relationships. An alternative approach, based on the isometric log-ratio transformation of molar concentration data, is developed and presented as an alternative method, free from potential numerical problems of the traditional methods. The utility, intuitiveness, and potential for mathematical problems of the three methods are compared and contrasted. Because the Na–Cl–Br system is a useful tool for sourcing solutes and investigating the evolution of basinal brines, results from this research may impact such critical topics as evaluating sources of brine contamination in the environment (possibly related to oil and gas production), evaluating the behavior of fluids in the reservoir during hydraulic fracturing, and tracking movement of fluids as a result of geologic CO₂ sequestration.  相似文献