Distribution of Ca in highly fractionated peralkaline magmas     

Julian S. Marsh 《Earth and Planetary Science Letters》1976,31(1):153-160

Many peralkaline rhyolites and granites contain less than 0.15 wt.% CaO. In contrast, strongly fractionated peralkaline nepheline syenites and phonolites usually contain greater than 0.5 wt.% CaO. Consideration of known distributions of Ca between crystals and liquid in conjunction with crystal fractionation does not provide an adequate explanation of the contrasting levels of Ca depletion observed. Examination of the suites of late-crystallizing accessory phases in peralkaline rocks suggests that Ca is more soluble in undersaturated magmas than in over-saturated magmas. Activities for CaO in silicic and phonolitic rocks are calculated and the latter have higher CaO activities than the former and this may manifest itself in the different suites of accessory phases and levels of Ca depletion noted in natural rocks.  相似文献   

Comparing Loss Estimation with Observed Damage: A Study of the 1999 Kocaeli Earthquake in Turkey   总被引：4，自引：0，他引：4  

Robin Spence  Julian Bommer  Domenico del Re  Juliet Bird  Nuray Aydinoğlu  Shigeko Tabuchi 《Bulletin of Earthquake Engineering》2003,1(1):83-113

Loss estimation from future earthquakes is of growing importance in planning earthquake protection strategies in high-risk areas. Loss models based on the spectral displacement approach are now widely used because of generally acknowledged deficiencies in earlier approaches using macroseismic intensity or peak ground-motion parameters. However, there has been to date rather little earthquake damage data by which the new generation of models can be assessed and which can be used to calibrate the parameters involved. The availability of several detailed damage surveys carried out following the 1999 Kocaeli earthquake in Turkey, provides a rare opportunity for such an assessment. In this paper the losses which would be predicted from two different approaches to loss assessment – one using predicted macroseismic intensity, the other using the spectral displacement method – are compared with actual observed losses in the Kocaeli event at two different locations where surveys were carried out. One of these sites was very close to the surface fault rupture (< 3 km distance), the other at a distance of about 4.5 km. It is shown that the predictive methods available generally overestimated the losses at these distances, and a number of possible reasons for these discrepancies are considered. The sensitivity of loss estimates to variations in the key parameters governing the estimation in each case are explored, in particular with respect to modifications in the parameters of the attenuation relationships and the vulnerability parameters. The implications of these results for estimating future losses are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Style-of-Faulting in Ground-Motion Prediction Equations   总被引：8，自引：6，他引：8  

Julian J. Bommer  John Douglas  Fleur O. Strasser 《Bulletin of Earthquake Engineering》2003,1(2):171-203

Equations for the prediction of response spectral ordinates invariably include magnitude, distance and site classification as independent variables. A few equations also include style-of-faulting as a fourth variable, although this has an almost negligible effect on the standard deviation of the equation. Nonetheless, style-of-faulting is a useful parameter to include in ground-motion prediction equations since the rupture mechanism of future earthquakes in a particular seismic source zone can usually be defined with some confidence. Current equations including style-of-faulting use different schemes to classify fault ruptures into various categories, which leads to uncertainty and ambiguity regarding the nature and extent of the effect of focal mechanism on ground motions. European equations for spectral ordinates do not currently include style-of-faulting factors, and seismic hazard assessments in Europe often combine, in logic-tree formulations, these equations with those from western North America that do include style-of-faulting coefficients. In this article, a simple scheme is provided to allow style-of-faulting adjustments to be made for those equations that do not include coefficients for rupture mechanism, so that style-of-faulting can be fully incorporated into the hazard calculations. This also considers the case of normal fault ruptures, not modelled in any of the current Californian equations, but which are the dominant mechanism in many parts of Europe. The scheme is validated by performing new regressions on a widely used European attenuation relationship with additional terms for style-of-faulting. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Sensitivity of PSHA results to ground motion prediction relations and logic-tree weights   总被引：7，自引：0，他引：7  

Fabio Sabetta  Antonio Lucantoni  Hilmar Bungum  Julian J. Bommer 《Soil Dynamics and Earthquake Engineering》2005,25(4):317-329

Epistemic uncertainty in ground motion prediction relations is recognized as an important factor to be considered in probabilistic seismic hazard analysis (PSHA), together with the aleatory variability that is incorporated directly into the hazard calculations through integration across the log-normal scatter in the ground motion relations. The epistemic uncertainty, which is revealed by the differences in median values of ground motion parameters obtained from relations derived for different regions, is accounted for by the inclusion of two or more ground motion prediction relations in a logic-tree formalism. The sensitivity of the hazard results to the relative weights assigned to the branches of the logic-tree, is explored through hazard analyses for two sites in Europe, in areas of high and moderate seismicity, respectively. The analyses reveal a strong influence of the ground motion models on the results of PSHA, particularly for low annual exceedance frequencies (long return periods) and higher confidence levels. The results also show, however, that as soon as four or more relations are included in the logic-tree, the relative weights, unless strongly biased towards one or two relations, do not significantly affect the hazard. The selection of appropriate prediction relations to include in the analysis, therefore, has a greater impact than the expert judgment applied in assigning relative weights to the branches of the logic-tree.  相似文献   

Voting and borderland minorities: Recent Italian elections and the Slovene minority in eastern Fiuli-Venezia Giulia     

Julian V. Minghi 《GeoJournal》1997,43(3):263-271

This article seeks to link electoral behavior and borderland ethnic minority patterns. Results of the November 1993 mayoral election in Trieste, and the March 1994 and April 1996 national elections in Italy are studied in reference to the distribution of the Slovene minority in Northeastern Italy, specifically in the eastern part of the Region of Friuli-Venezia Giulia adjoining the boundary with Slovenia. The history of this borderland is rampant with conflict and territorial sovereignty changes. Recent events – the end of the Cold War, the breakup of Yugoslavia and independence of Slovenia, and the collapse of the Italian political party system – have served both to ease traditional tensions but also to exacerbate ethnic relations between Italians and the Slovene minority. The impact of Italian electoral reform and political party reformulation on the region is examined. Specifically, Mayor Illy's election in the city of Trieste in 1993 and voting patterns in the borderland Goriziano district of the Italian Senate for both the 1994 and 1996 elections are studied in some detail. The article concludes that while electoral campaigns and election results are marked with ethnic confrontation and contrasts, evidence suggests that, despite continuing nationalist tendencies, greater understanding and cooperation between Italians and Slovenes are emerging.  相似文献   

Oxygen isotope geochemistry of the Mesozoic volcanics of the Etendeka Formation,Namibia     

Chris Harris  H. Stuart Smith  Simon C. Milner  Anthony J. Erlank  Andrew R. Duncan  Julian S. Marsh  Nicholas P. Ikin 《Contributions to Mineralogy and Petrology》1989,102(4):454-461

The Etendeka Formation volcanics consist of a bimodal association of basalts and quartz latites. Forty three new whole rock oxygen isotope analyses are reported for all the major magma types. All the rocks except a minor suite of dolerites have higher ¹⁸O values than normal mantle. The basic rocks (average of 29=8.8) have significantly different ¹⁸O to the acid rocks (average of 10=14.4) These data are apparently consistent with previously published petrogenetic models, which propose that the basalts were affected by crustal contamination and that the quartz latites are crustally derived. However, mineral oxygen data show that there is significant oxygen isotopic disequilibrium between phenocryst and whole rock, the latter being significantly higher in most cases. One of the basic magma types (the Tafelberg basalts) shows mutual positive correlations between ¹⁸O, SiO₂ and _Sr. If these correlations are due to crustal contamination, then as much as 45% contamination is required by material having a ¹⁸O value of 15 which is the maximum observed value in the Damaran basement rocks. In the absence of pyroxene phenocryst ¹⁸O data for the high _Sr Tafelberg basalts (they are aphyric), it is not possible to confirm that contamination has taken place. An alternative explanation is that the correlation between _Sr and SiO₂ resulted from assimilation coupled with fractional crystallization (AFC) (before emplacement). Post-eruption alteration resulted in a correlation between SiO₂ ¹⁸O because the material with the most Si-O bonds was able to concentrate ¹⁸O more effectively. The limited mineral data for the quartz latites suggests that there is some source heterogeneity. A pyroxene ¹⁸O value of 10% for a southern Etendeka quartz latite is consistent with a crustal source.  相似文献   

Oxygen and carbon stable isotopes in otoliths record spatial isolation of Patagonian toothfish (Dissostichus eleginoides)     

Julian Ashford  Cynthia Jones 《Geochimica et cosmochimica acta》2007,71(1):87-94

Strong contrasts in ambient isotope ratios and in diet suggest stable isotopes in the otoliths of oceanic fish can resolve water masses and geographic areas, promising a powerful multivariate approach for examining population structure and provenance. To test this, whole otoliths were taken from Patagonian toothfish (Dissostichus eleginoides) sampled off the Patagonian Shelf and South Georgia, on either side of a population boundary, and otolith δ¹⁸O and δ¹³C values were measured to see if they could distinguish South American-caught fish from those taken in the Antarctic. Values of otolith δ¹⁸O and δ¹³C predicted capture area with 100% success, validating their use for distinguishing provenance and corroborating the prior evidence of population isolation. Values of δ¹⁸O in the otoliths reflected ambient values as well as seawater temperature: low values in Patagonian Shelf fish were consistent with exposure to Antarctic Intermediate Water (AAIW), and high values in South Georgia fish were consistent with exposure to Circumpolar Deep Water (CDW). In contrast, differences in otolith δ¹³C appeared to reflect diet: relative depletion of otolith δ¹³C at South Georgia compared to the Patagonian Shelf were most likely linked to differences in sources of metabolic carbon, as well as δ¹³C in dissolved inorganic carbon (DIC) of seawater. These contrasting properties strongly suggest that stable isotopes can resolve the provenance of toothfish from Antarctic sampling areas that hitherto have been difficult to separate. These results show that, by using the chemistry recorded in otoliths, researchers can exploit biogeochemical variation in fully marine environments to examine the spatial ecology of oceanic fish.  相似文献   

Winter-spring precipitation reconstructions from tree rings for northeast Mexico     

Jose Villanueva-Diaz  David W. Stahle  Brian H. Luckman  Julian Cerano-Paredes  Mathew D. Therrell  Malcom K. Cleaveland  Eladio Cornejo-Oviedo 《Climatic change》2007,83(1-2):117-131

The understanding of historic hydroclimatic variability is basic for planning proper management of limited water resources in northeastern Mexico. The objective of this study was to develop a network of tree-ring chronologies to reconstruct hydroclimate variability in northeastern Mexico and to analyze the influence of large-scale circulation patterns, such as ENSO. Precipitation sensitive tree-ring chronologies of Douglas-fir were developed in mountain ranges of the Sierra Madre Oriental and used to produce winter-spring precipitation reconstructions for central and southern Nuevo Leon, and southeastern Coahuila. The seasonal winter-spring precipitation reconstructions are 342 years long (1659–2001) for Saltillo, Coahuila and 602 years long (1400–2002) for central and southern Nuevo Leon. Both reconstructions show droughts in the 1810s, 1870s, 1890s, 1910s, and 1970s, and wet periods in the 1770s, 1930s, 1960s, and 1980s. Prior to 1800s the reconstructions are less similar. The impact of ENSO in northeastern Mexico (as measured by the Tropical Rainfall Index) indicated long-term instability of the Pacific equatorial teleconnection. Atmospheric circulation systems coming from higher latitudes (cold fronts or `nortes’) and others developed in the Gulf of Mexico (tropical storms, hurricanes) also influence the climatic conditions characterizing this region. The recent development of new and longer tree-ring chronologies for the region will contribute to a better understanding of the interannual and multidecadal climatic variability of northeastern Mexico.  相似文献   

Quantifying the impact of chemicals on stable carbon and oxygen isotope values of raw pollen     

Carolina Müller  Julian Hennig  Frank Riedel  Gerhard Helle 《第四纪科学杂志》2021,36(3):441-449

Purification protocols to extract pollen from lake sediments contain chemicals that alter the carbon and oxygen pollen-isotope values according to pollen characteristics and family affiliation. Modern (raw) pollen of broad-leaved (Alnus glutinosa, Betula pendula, Carpinus betulus, Corylus avellana, Fagus sylvatica and Quercus robur) and coniferous tree species (Picea abies and Pinus sylvestris) were treated with potassium hydroxide (KOH), hydrofluoric acid (HF), sodium hypochlorite (NaClO) and sulphuric acid (H₂SO₄) to test the impact on δ¹³C_pollen and δ¹⁸O_pollen and assess the applicability in purification protocols. Pollen of broad-leaved and coniferous trees reacted differently to chemical exposure, but response patterns are generally alike. Alterations of δ¹³C_pollen values vary between + 1.0‰ (B. pendula, NaClO-treatment) and −5.0‰ (P. sylvestris, H₂SO₄-treatment). The δ¹³C_pollen values of raw and chemically treated samples seem to be related after treatments with KOH, NaClO and HF, whereas the application of H₂SO₄ led to inconsistent changes among species. The impact of chemicals on δ¹⁸O_pollen are more diverse and offsets range between +1.1‰ (C. avellana, NaClO-treatment) and −17.9‰ (P. sylvestris, H₂SO₄-treatment). In general, the use of isotope-altering chemicals in purification protocols should be brought to a minimum, but the application of KOH and NaClO seems mostly unproblematic before δ¹³C_pollen and δ¹⁸O_pollen analysis.  相似文献   

The oxygen isotope composition of Karoo and Etendeka picrites: High δ18O mantle or crustal contamination?     

Chris Harris  Petrus le Roux  Ryan Cochrane  Laure Martin  Andrew R. Duncan  Julian S. Marsh  Anton P. le Roex  Cornelia Class 《Contributions to Mineralogy and Petrology》2015,170(1):1-24

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