Benjamin Edwards

Bio: Benjamin Edwards is an academic researcher from University of Liverpool. The author has contributed to research in topics: Volcano & Lava. The author has an hindex of 34, co-authored 131 publications receiving 3348 citations. Previous affiliations of Benjamin Edwards include Dickinson College & ETH Zurich.

Petrogenesis of the 1.43 Ga Sherman Batholith, SE Wyoming, USA: a Reduced, Rapakivi-type Anorogenic Granite

Abstract: The 1·43 Ga Sherman batholith, southeastern Wyoming, USA, origin that are found throughout the Proterozoic ‘anorogenic’ granite provinces of the southwestern USA, Adirshows extreme A-type petrochemical characteristics compared with other Mid-Proterozoic granite batholiths of North America. It ondacks, eastern Canada, southern Greenland and the Fennoscandian Shield (Anderson, 1983). Phanerozoic consists of: (1) the Sherman granite, a coarse-grained biotite hornblende granite that locally contains fayalite and pyroxenes; (2) examples include Paleozoic granites of southeastern Australia (Collins et al., 1982) and of Corsica (Poitrasson et the Lincoln granite, a medium-grained biotite granite; (3) a porphyritic biotite hornblende granite that probably formed by interaction al., 1995), and the Mesozoic Nigerian Younger granites ( Jacobsen et al., 1958) and the White Mountain Magma of granitic and mafic magmas; and (4) iron-enriched mafic dikes and pods. The ilmenite-series, metaluminous Sherman granite Series (Foland & Allen, 1991). ‘Anorogenic granite’ refers to plutons that are not associated with compressional exhibits extreme values of FeO/(FeO + MgO) and is rich in structures, and that were emplaced long after any known K, REE, Nb and Y. It crystallized at temperatures exceeding orogenic event. Anorogenic, or ‘A-type’ granites (Loiselle 900°C and a pressure of ~2·5 kbar, with water activity of 0·7 & Wones, 1979) are characterized by low H2O and O2 and Dlog fO2 of –0·1 to –0·5. The Lincoln granite, which is fugacities along with high FeO/(FeO + MgO), K2O/ peraluminous and has less extreme A-type geochemical characteristics, Na2O and K2O contents. A-type granites typically are rich crystallized at temperatures as low as 750°C and Dlog fO2 of in incompatible elements, including rare earth elements around 0·5 units above FMQ (fayalite–magnetite–quartz). The (REE), Zr, Nb and Ta, but poor in Co, Sc, Cr, Ni, Ba, rocks of the Sherman batholith are chemically equivalent to lavas Sr, and Eu. Minimum magma liquidus temperatures are from the Yellowstone hotspot. Like the Yellowstone magmas, the 900–1000°C (Clemens et al., 1986; Creaser & White, Sherman batholith probably originated by partial melting of under1991). Some workers suggest these rocks are derived plated, mantle-derived mafic rocks. from melting of tonalitic or more felsic crust (Anderson & Cullers, 1978; Collins et al., 1982; Clemens et al., 1986; Creaser et al., 1991), whereas others relate the granites

ECOS-09 Earthquake Catalogue of Switzerland Release 2011 Report and Database

Abstract: ECOS-09 (Earthquake Catalog of Switzerland 2009) is the current earthquake catalog of Switzerland. It integrates the following basic information: The Macroseismic Earthquake Catalog of Switzerland, with events from AD 250, revised and supplemented to 2008; Yearly reports of the Swiss earthquake commission since 1879; Earthquake locations of the instrumental networks of the SED since 1975; Supplemented by 12 earthquake catalogs from neighboring and international agencies. The macro-seismic part of the catalog is based on the analysis of observed and historical impacts of earthquakes on people and the environment. The epicenters and earthquake magnitudes are estimated from this information. The instrumental part of the catalog is based on the analysis of measured ground-motion, from which the location of the epicenter and the magnitude can be directly computed. ECOS-09 covers the period AD 250 to the end of 2008. The available data covers Switzerland and bordering regions (Swiss coordinates (km): 460-882 / 20-350; geographical coordinates approx.: 5.6-11.1E / 45.4-48.3N). Hours are given in UTC (Coordinated Universal Time).

Attenuation of seismic shear wave energy in Switzerland

Abstract: SUMMARY Modelling the attenuation of shear wave energy is an important component of seismic hazard analysis. Previous studies have shown how attenuation, particularly in the uppermost layers of the crust, is regionally dependent. The impact of this is that the decay of energy radiating from an earthquake will vary from place to place. To quantify the regional attenuation in Switzerland we model the Fourier spectral amplitude of small-to-moderate earthquakes, recorded on the local seismic networks. High-frequency decay is parametrized by Q and κ, while apparent geometrical spreading models account for the frequency-independent decay of energy. We analyse ground motion encompassing the significant duration of shaking to provide models that are useful for the purpose of seismic hazard analysis. Two methods are used to estimate the whole path attenuation parameter, t*: first, a simultaneous fit of the source model and attenuation effects across the entire spectral bandwidth for earthquakes with M > 2; and secondly, a linear fit of an attenuation model to the high-frequency part of the spectrum for earthquakes with M > 3.5. The t* parameter is found to vary with hypocentral distance consistent with a weakly attenuating crust and strongly attenuating uppermost layer. 1-D tomographic inversions indicate a profile of increasing Q with depth down to the Moho. Frequency-independent decay is parametrized using a three-part model which allows for the inclusion of Moho reflection phases in the spectrum in the range of 20–140 km in the Swiss Foreland and from 70 to 140 km in the Swiss Alps.

Thinking fast and slow.

Abstract: In 1974 an article appeared in Science magazine with the dry-sounding title “Judgment Under Uncertainty: Heuristics and Biases” by a pair of psychologists who were not well known outside their discipline of decision theory. In it Amos Tversky and Daniel Kahneman introduced the world to Prospect Theory, which mapped out how humans actually behave when faced with decisions about gains and losses, in contrast to how economists assumed that people behave. Prospect Theory turned Economics on its head by demonstrating through a series of ingenious experiments that people are much more concerned with losses than they are with gains, and that framing a choice from one perspective or the other will result in decisions that are exactly the opposite of each other, even if the outcomes are monetarily the same. Prospect Theory led cognitive psychology in a new direction that began to uncover other human biases in thinking that are probably not learned but are part of our brain’s wiring.

A geochemical classification for granitic rocks

Abstract: This geochemical classification of granitic rocks is based upon three INTRODUCTION variables. These are FeO/(FeO + MgO) = Fe-number [or Although granitoids are the most abundant rock types FeO/(FeO + MgO) = Fe∗], the modified alkali–lime index in the continental crust, no single classification scheme (MALI) (Na2O + K2O – CaO) and the aluminum saturation has achieved widespread use. Part of the problem in index (ASI) [Al/(Ca – 1·67P + Na + K)]. The Fe-number granite classification is that the same mineral assemblage, (or Fe∗) distinguishes ferroan granitoids, which manifest strong iron quartz and feldspars with a variety of ferromagnesian enrichment, from magnesian granitoids, which do not. The ferroan minerals, can be achieved by a number of processes. and magnesian granitoids can further be classified into alkalic, Granitoids can form from differentiation of any hyalkali–calcic, calc-alkalic, and calcic on the basis of the MALI persthene-normative melt and from partial melting of and subdivided on the basis of the ASI into peraluminous, metamany rock types. Furthermore, granitic melts may be luminous or peralkaline. Because alkalic rocks are not likely to be derived solely from crustal components, may form from peraluminous and calcic and calc-alkalic rocks are not likely to be evolved mantle-derived melts, or may be a mixture peralkaline, this classification leads to 16 possible groups of granitic of crustal and mantle-derived melts. Because of this rocks. In this classification most Cordilleran granitoids are magnesian complexity, petrologists have relied upon geochemical and calc-alkalic or calcic; both metaluminous and peraluminous classifications to distinguish between various types of types are present. A-type granitoids are ferroan alkali–calcic, although granitoids. Approximately 20 different schemes have evolved over the past 30 years [see Barbarin (1990, 1999) some are ferroan alkalic. Most are metaluminous although some are for a summary thereof]. Most of these schemes are either peraluminous. Caledonian post-orogenic granites are predominantly genetic or tectonic in nature. This paper is an attempt magnesian alkali–calcic. Those with <70 wt % SiO2 are domto present a non-genetic, non-tectonic geochemical clasinantly metaluminous, whereas more silica-rich varieties are comsification scheme that incorporates the best qualities of monly peraluminous. Peraluminous leucogranites may be either the previous schemes, and to explain the petrologic magnesian or ferroan and have a MALI that ranges from calcic to processes that makes this scheme work. alkalic.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

Abstract: The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

NGA-West2 Equations for Predicting PGA, PGV, and 5% Damped PSA for Shallow Crustal Earthquakes:

Abstract: We provide ground motion prediction equations for computing medians and standard deviations of average horizontal component intensity measures (IMs) for shallow crustal earthquakes in active tecton...