Modelling peak accelerations from earthquakes

This paper deals with the prediction of peak horizontal accelerations with emphasis on seismic risk and insurance concerns. Non‐linear mixed effects models are used to analyse well‐known earthquake data and the consequences of mis‐specifying assumptions on the error term are quantified. A robust fit of the usual model, using recently developed robust weighted maximum likelihood estimators, is presented. Outlying data are automatically identified and subsequently investigated. A more appropriate model accounting for the extreme value nature of the responses, is also developed and implemented. The implication on acceleration predictions is demonstrated. Copyright © 2006 John Wiley & Sons, Ltd.     

Economic development,technological change,and the new international economic order

This paper examines dimensions of technological change and selected relationships between new technology and the process of economic development within the general framework of the New International Economic Order. Concepts discussed include economic growth and development, structural change, technological change, innovations, the transfer of technology, and appropriate technology. The relationships between these concepts are described and their significance with regard to the economic development of lesser-developed countries is assessed.     

Kimberlites: Their relation to mantle hotspots

Available age data support the hypothesis that kimberlite intrusions are formed by mantle hotspots. The hypothesis has been tested by inverting the volcanic traces formed by three hotspots to determine the post-Triassic motions of Africa, South America, and North America relative to these hotspots. Then, using these motions, the kimberlites intruded on these continents within the last 150 m.y. are relocated to their place of origin in the present hotspot reference frame. The result indicates that a majority of the kimberlites formed within 5° of a mantle hotspot. Statistical analysis shows that this kimberlite/hotspot correlation is significant at above the 90% level.     

Rare earth element distribution in some hydrothermal minerals: evidence for crystallographic control

Rare earth element (REE) abundances were measured by neutron activation analysis in anhydrite (CaSO₄), barite (BaSO₄), siderite (FeCO₃) and galena (PbS). A simple crystal-chemical model qualitatively describes the relative affinities for REE substitution in anhydrite, barite, and siderite. When normalized to ‘crustal’ abundances (as an approximation to the hydrothermal fluid REE pattern), log REE abundance is a surprisingly linear function of (ionic radius of major cation—ionic radius of REE)² for the three hydrothermal minerals, individually and collectively. An important exception, however, is Eu, which is anomalously enriched in barite and depleted in siderite relative to REE of neighboring atomic number and trivalent ionic radius. In principle, REE analyses of suitable pairs of co-existing hydrothermal minerals, combined with appropriate experimental data, could yield both the REE content and the temperature of the parental hydrothermal fluid.The REE have only very weak chalcophilic tendencies, and this is reflected by the very low abundances in galena—La, 0.6 ppb; Sm, 0.06 ppb; the remainder are below detection limits.     

Transmission electron microscope and rock magnetic investigations of remanence carriers in a Precambrian metadolerite

A Precambrian metadolerite dyke has two distinct types of remanence carriers; those with medium/high coercivities (unblocking fields of 20–120 mT) and those with low coercivities (unblocking fields of <15 mT). Optical examination reveals numerous submicron probably opaque inclusions in the plagioclase feldspar and also large opaque grains consisting of coarse oxidation-exsolution intergrowths of magnetite and ilmenite. All opaque phases have been examined using transmission electron microscopy together with microanalysis and electron diffraction. The submicron inclusions in the plagioclase are titanomagnetites(0 < x ≤ 0.14) with a size range between about 0.01 and 0.5 μm and axial ratios between 1 (equidimensional) and about 0.3. Many of these inclusions fall in the single-domain field but some are probably pseudo-single-domain. The large opaque grains contain almost pure magnetite and ilmenite and show no fine-scale exsolution; the magnetite regions of the intergrowths are of multidomain size and reveal multidomain structure under Lorentz electron microscopy. There are also some primary ilmenites containing very fine exsolved haematite, and there are very fine plates of ilmenite and very elongate needles of magnetite within the augite. Experiments on artificial samples containing very carefully prepared separates of plagioclase and large opaque grains show that the pure plagioclase acquires a remanence with unblocking fields of 20–140 mT and blocking temperatures of 390–590°C and the large opaque grains acquire a remanence with unblocking fields of less than 15 mT but a wide range of blocking temperatures up to about 570°C. It is concluded that the medium/high coercivity component of remanence in the rock is carried largely or possibly entirely by the submicron magnetites within the plagioclase and that the low coercivity component is carried largely or entirely by the multidomain magnetites in the large opaques. The contribution of the magnetite needles in the augite is uncertain as the rock does not contain any detectable component of remanence with the extremely high coercivities expected from their very elongate shape.     

Chemical fractionations in meteorites—IX. C3 chondrites

Four C3V chondrites (Grosnaja, Kaba, Mokoia, Vigarano) and three C3O chondrites (Felix, Kainsaz, and Lancé) were analyzed by radiochemical neutron activation for 17 trace elements. Both classes show a typical chondritic step pattern, reflecting loss of volatiles during chondrule formation. Elements condensing above 1300 K (U, Re, Ir, Ni) are present in essentially Cl chondrite proportions, while moderately volatile elements condensing between 1300 K and 800 K (Ge, Rb, Ag) are depleted by a factor of 0.44. However, elements condensing below 700 K (S, Cs, Bi, Tl, Br, Se, Te, In, Cd) are depleted to a still greater degree, and more so in the Ornans subclass (factor of 0.24, except Cd 0.007) than in the Vigarano subclass (factor of 0.29). This additional depletion may be due to a slight (less than 3-fold) dust-gas fractionation, by settling of dust to the median plane of the solar nebula. Among other chondrite classes, ordinary chondrites show a similar depletion, but C2 chondrites do not. Possibly the undepleted meteorites formed in one of the convection zones of the nebula predicted by Cameron and Pine, whereas the depleted meteorites formed in a quiescent region.The condensation of chalocophile elements as a function of H₂S partial pressure is discussed, in an attempt to explain the drastic difference in Cd abundance between the two subclasses. It appears that the $\text{H}{}_2\text{S}\text{H}{}_2$ ratio is the key variable. C3O's seem to have condensed in a region where enough metallic Fe was present to buffer the H₂S pressure, while C3V's condensed in a more oxidized region, where H₂S was in excess. Accretion temperatures, for an assumed nebular pressure of 10^?5 atm, were between 415 and 430 K for C3O's and less than 440 K for C3V's.Two slightly volatile elements, Sb and Au, show variable depletion, presumably reflecting variable loss during chondrule formation. Indeed, their depletion correlates with the abundance of iron-poor olivine, a measure of the peak temperature and time during chondrule formation.     

Heavy rare gases from Rabbit Lake (Canada) and the Oklo mine (Gabon): natural spontaneous chain reactions in old uranium deposits

Xenon isotopic studies confirm natural spontaneous chain reactions at the Oklo mine site (Republic of Gabon) with an integrated neutron flux of approximately 4 × 10²⁰n/cm² and a duration between 14,000 and 70,000 years. Similar studies for the Rabbit Lake deposit (Saskatchewan), a slightly younger site with some evidence of continued geologic activity, shows no evidence of self-supporting reactions.     

Preservation of ancient impact ages on the R chondrite parent body: 40Ar/39Ar age of hornblende‐bearing R chondrite LAP 04840

The hornblende‐ and biotite‐bearing R chondrite LAP 04840 is a rare kind of meteorite possibly containing outer solar system water stored during metamorphism or postshock annealing deep within an asteroid. Because little is known regarding its age and origin, we determined ⁴⁰Ar/³⁹Ar ages on hornblende‐rich separates of the meteorite, and obtained plateau ages of 4340(±40) to 4380(±30) Ma. These well‐defined plateau ages, coupled with evidence for postshock annealing, indicate this meteorite records an ancient shock event and subsequent annealing. The age of 4340–4380 Ma (or 4.34–4.38 Ga) for this and other previously dated R chondrites is much older than most impact events recorded by ordinary chondrites and points to an ancient event or events that predated the late heavy bombardment that is recorded in so many meteorites and lunar samples.