On the Application of Mwp in the Near Field and the March 11, 2011 Tohoku Earthquake     

Barry Hirshorn  Stuart Weinstein  Seiji Tsuboi 《Pure and Applied Geophysics》2013,170(6-8):975-991

Tsunami Warning Centers issue rapid and accurate tsunami warnings to coastal populations by estimating the location and size of the causative earthquake as soon as possible after rupture initiation. Both US Tsunami Warning Centers have therefore been using Mwp to issue Tsunami Warnings 5–10 min after Earthquake origin time since 2002. However, because Mwp (Tsuboi et al., Bulletin of the Seismological society of America 85:606–613, 1995) is based on the far-field approximation to the P-wave displacement due to a double couple point source, we should only very carefully apply Mwp to data obtained in the near field, at distances of less than a few wavelengths from the fault. On the other hand, the surface waves from Great Earthquakes, including those that occur just offshore of populated areas, such as the 2011 Tohoku earthquake, clip seismographs located near the fault. Because the first arriving P-waves from such large events are often on scale, Mwp should provide useful information, even for these Great Earthquakes. We therefore calculate Mwp from 18 unclipped STS-1 broadband P-wave seismograms, recorded at 2–15° distance from the Tohoku epicenter to determine if Mwp can usefully estimate Mw for this earthquake, using data obtained close to the epicenter. In this case there should be a good chance to get reliable Mwp values for stations at epicentral distances of 9–10°, since the source duration for the Tohoku earthquake is less than 200 s and the time window used to estimate Mwp is 120 s in duration. Our analysis indicates that Mwp does indeed give reliable results (Mw ~ 9.1) beginning at about 11° distance from the epicenter. The values of Mwp from seismic waveforms obtained at 11–15° epicentral distance from the Mw 9.1 off the east coast of Tohuku earthquake of March 11, 2011 fell within the range 9.1–9.3, and were available within 4–5 min after origin time. Even the Mwp values of 7.7–8.4, obtained at less than 5° epicentral distance, exceed the PTWC’s threshold of Mw 7.6 for issuing a regional tsunami warning to coastal populations within 1,000 km of the epicenter, and of Mw 6.9 for issuing a local tsunami warning to the coastal populations of Hawaii.  相似文献   

Discussion of “Effects of temporal resolution on hydrological model parameters and its impact on prediction of river discharge”     

Ian G. Littlewood  Barry F. W. Croke  Peter C. Young 《水文科学杂志》2013,58(3):521-524

Citation Littlewood, I. G., Croke, B. F. W. & Young, P. C. (2011) Discussion of “Effects of temporal resolution on hydrological model parameters and its impact on prediction of river discharge” by Y. Wang, B. He & K. Takase (2009, Hydrol. Sci. J. 54(5), 886–898). Hydrol. Sci. J. 56(3), 521–524.  相似文献   

Responses of two trophic levels to patch enrichment along a New Zealand stream continuum     

Barry J. F. Biggs  Rex L. Lowe 《新西兰海洋与淡水研究杂志》2013,47(2):119-134

We carried out a benthic survey and two experiments in runs at eight sites down the Kakanui River (South Island, New Zealand) during summer low flows, to investigate the interaction between nutrients, periphyton, and macro‐grazers. Benthic periphytic biomass was generally low (< 20 mg m^‐2 chlorophyll a) at most sites, but high densities of macro‐grazers (mainly snails) were observed at six of the eight sites. Chlorophyll a and cellular P concentrations were generally higher on artificial substrates in the first‐ to third‐order tributaries, compared with downstream. Macro‐grazer densities (mainly snails) were also highest in the second‐ and third‐order tributaries. Enrichment of patches with N and P did not translate into significant increases in chlorophyll a concentrations. Instead there was a general increase in macro‐grazers, and an increase in the relative abundance of Cocconeis placentula. In a second experiment, the chlorophyll a level was five‐fold higher on the substrates where macro‐grazers were excluded and there was no significant response of chlorophyll a to nutrient addition on these substrates. On the grazed substrates, densities of snails and caddis‐larvae were two‐fold higher with N+P enrichment. These experiments provided evidence for a tight coupling between first and second trophic levels, and strong grazer control of periphyton, in this river.  相似文献   

The variability of internal tides in the Northern South China Sea     

Barry B. Ma  Ren-Chieh Lien  Dong S. Ko 《Journal of Oceanography》2013,69(5):619-630

An array of three bottom-mounted ADCP moorings was deployed on the prevailing propagation path of strong internal tides for nearly 1 year across the continental slope in the northern South China Sea. These velocity measurements are used to study the intra-annual variability of diurnal and semidiurnal internal tidal energy in the region. A numerical model, the Luzon Strait Ocean Nowcast/Forecast System developed at the U.S. Naval Research Laboratory that covers the northern South China Sea and the Kuroshio, is used to interpret the observed variation of internal tidal energy on the Dongsha slope. Internal tides are generated primarily at the two submarine ridges in the Luzon Strait. At the western ridge generation site, the westward energy flux of the diurnal internal tide is sensitive to the stratification and isopycnal slope associated with the Kuroshio. The horizontal shear at the Kuroshio front does not modify the propagation path of either diurnal or semidiurnal tides because the relative vorticity of the Kuroshio in Luzon Strait is not strong enough to increase the effective inertial frequency to the intrinsic frequency of the internal tides. The variation of internal tidal energy on the continental slope and Dongsha plateau can be attributed to the variation in tidal beam propagation in the northern South China Sea.  相似文献   

Aspects of Rift Valley faulting and volcanicity in North Tanzania: report of a Geologists’ Association Field Meeting in 2008     

J. Barry Dawson 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(3):342-34

The African Rift Valleys results from Neogene-Recent breakup up the African Plate due to continental extension. Compared with the western sector, in the eastern or Gregory Rift Valley the fracturing is accompanied by a large amount of volcanic activity and, in northern Tanzania, the volcanic rocks are relatively young compared with those in Ethiopia and Kenya where the products of the earliest stages of mantle melting are buried beneath older, more-extensive volcanic formations. The volcanic rocks vary from Pliocene and early Pleistocene intraplate basalts and trachytes to late Pleistocene/Holocene nephelinites and carbonatites.  相似文献   

Structuring problems in sustainability science: The multi-level DPSIR framework   总被引：2，自引：0，他引：2  

Barry Ness  Stefan Anderberg  Lennart Olsson 《Geoforum》2010,41(3):479-488

Sustainability science needs approaches that allow for the integration of knowledge across disciplines and scales. This paper suggests an approach to conceptualize problems of unsustainability by embedding the Drivers-Pressure-State-Impact-Response (DPSIR) scheme within a multi-level institutional framework represented by Hägerstrand’s system of nested domains. The proposed taxonomy helps to decipher and to better understand key casual chains and societal responses at the appropriate spatial levels for particular sustainability problem areas. To illustrate the scheme more concretely the example of recent problem-solving efforts for Baltic Sea eutrophication driven by Swedish agriculture is examined. The discussion focuses on how the scheme fulfills the four research strategy requirements within the field of sustainability science and how the scheme is distinct from alternative approaches.  相似文献   

An investigation of aspects of mine waste from a kyanite mine,Central Virginia,USA     

Mark Paul Speeg Krekeler  C. Scott Allen  Lance E. Kearns  J. Barry Maynard 《Environmental Earth Sciences》2010,61(1):93-106

Kyanite Mining Corporation, located in Dillwyn, Virginia has been in operation for over 50 years and their local operation is the largest kyanite mine in the world. As part of the processing at this location, a magnetic separate is generated and a minimum estimation of 3.57 million tons of waste has accumulated. Currently no use for the magnetic separate has been identified. We investigated eight representative samples of the magnetic mine waste which varied in color from a dark tan to black, to determine if the waste could be recycled as an ore or could be used as an environmental media. Mineralogical investigations indicate the composition of the magnetic mine waste is dominated by magnetite, kyanite, lesser amounts of hematite and charcoal. Magnetite occurs as fine grained crystals and as inclusions in kyanite. Hematite occurs largely as botryoidal textures, as discrete grains, and as coatings on kyanite grains. Fe-oxide spheres ranging in diameter from approximately 5–100 μm are common and may compose up to 10% in some samples. Titanium dioxide was rarely observed as coatings on silicate mineral grains. Energy dispersive spectroscopy analysis on magnetite crystals indicates they have end-member compositions. Bulk property investigations indicate that grain size distributions of samples are primarily unimodal with 20–40% of material being between 0.600 and 0.250 mm. Hydraulic conductivity values of samples investigated vary between 0.0036 and 0.0077 cm/s and are broadly consistent with those expected of sands with similar grain size distributions. In addition to the magnetic waste stream a light blue, water soluble, amorphous Cu sulfate occurs as a coating on surfaces of boulders. The coating is composed of rounded interlocking particles 5–60 μm in diameter. This material is of some environmental concern for freshwater invertebrates, but can be managed using sorption media. Hyperspectral data were gathered of the magnetic separate, kyanite ore samples, and the light blue Cu sulfate. The signatures of the kyanite ore, the blue mineral coating, and a mixture of the two provide spectral fingerprints that an imaging spectrometer could exploit for rapid detection and subsequent environmental monitoring.  相似文献   

Comment on: ‘Multi-element signatures of stream sediments and sources under moderate to low flow conditions’ by M.I. Stutter,S.J. Langan,D.G. Lumsdon,L.M. Clark     

Barry Rawlins 《Applied Geochemistry》2010

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Mapping the archaeological soil archive of sand and gravel mineral reserves in Britain     

Ingrid Ward  Barry Smith  Russell Lawley 《Geoarchaeology》2009,24(1):1-21

Primary sand and gravel deposits in Britain play an important role in preserving our cultural heritage and are also a valuable aggregate resource. While an understanding of the extrinsic properties of the soil archive (such as pH, redox, groundwater) can provide a firstorder assessment of the potential risk to any archaeologically sensitive deposits, we have very poor definition of spatial variations in the extrinsic properties of soil that influence archaeological preservation at a regional and national scale. Developments in digital geological mapping, remote sensing, and geochemical survey data undertaken by the British Geological Survey (BGS) have, however, significantly extended capabilities in this respect and can potentially be used to provide a primary assessment of the sensitivity of the present soil archive and the potential risk from changes to the soil process on cultural material in areas earmarked for aggregate extraction. Two of the major factors affecting archaeological preservation—soil acidification and groundwater—can be mapped or predicted at scales of better than 1:50,000 across increasingly large parts of the country using a combination of regional hydrogeological, geophysical, and geochemical data. Additional data from site investigations may further refine preservation potential as a function of changes in redox potential and acidity. These data, maps and models can be used to (1) better establish a baseline for archaeological preservation at a regional and national scale and (2) improve our understanding of how the physical and chemical properties of the near surface environment can be managed to sustainably preserve archaeological materials in areas impacted by sand and gravel extraction. © 2009 Wiley Periodicals, Inc.  相似文献   

Age of the Alaşehir graben (West Turkey) and its tectonic implications     

Gürol Seyitolu  Barry C. Scott 《Geological Journal》1996,31(1):1-11

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