The Melting Relations of Iron, and Temperatures in the Earth's Core     

Francis Birch 《Geophysical Journal International》1972,29(4):373-387

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Bedrock Depth Estimates from Ground Magnetometer Profiles     

F. S. Birch 《Ground water》1984,22(4):427-432

Bedrock depths can be calculated readily from ground magnetic profiles using either Werner deconvolution or Fourier spectral analysis. For crystalline basement rocks of New England and eastern Canada, a vertical dike is a useful magnetic source model. Formulae for these methods are presented along with some practical guidelines for implementing them. Six field examples from metamorphic and igneous areas in New Hampshire show that bedrock depths from spectral analysis agree well with estimates from seismic refraction, from wells and from outcrops. The Werner estimates are much more variable but commonly bracket the others. At several of these sites, measurements by other geophysical methods would be impractical, more expensive, or restricted to certain times of the year.  相似文献   

The chemistry of suspended particulate material in a highly contaminated embayment of Port Jackson (Australia) under quiescent,high-wind and heavy-rainfall conditions   总被引：1，自引：0，他引：1  

Gavin Birch  Laura O’Hea 《Environmental Geology》2007,53(3):501-516

This study investigated physico-chemical characteristics of the water column and chemistry of suspended particulate material (SPM) under quiescent, high-wind and high-wind/heavy-rainfall conditions in Homebush Bay, a highly contaminated embayment of Port Jackson (Australia) to distinguish source and possible adverse effects to benthic and pelagic animals. Mean concentrations in surficial sediment were <1, 14, 181, 141, 37, 290 and 685 μg g⁻¹ for Cd, Co, Cr, Cu, Ni, Pb and Zn, respectively. Sediment chemistry indicated these metals had multiple sources, i.e. the estuary, stormwater and industry. Mean total suspended solids (TSS) were 7, 17 and 20 mg L⁻¹ during quiescent, high-rainfall and heavy rainfall/high wind conditions, respectively, whereas SPM Cd, Co, Cr, Cu, Ni, Pb and Zn concentrations varied between 13–25, 166–259, 127–198, 38–82, 236–305 and 605–865 μg g⁻¹, respectively under these conditions. TSS and total water metal concentrations were lowest during quiescent conditions. High TSS and metal loads in surface water characterised high-rainfall events. Wind-induced resuspension contributed the greatest mass of SPM and metals to the water column. Benthic animals may be adversely affected by Pb and Zn in sediment. Total water Cu and Zn concentrations may pose a risk to filter-feeding animals in the water column due to resuspension of contaminated sediment.  相似文献   

Lead distribution on a public shotgun range   总被引：1，自引：0，他引：1  

James R. Craig  David Edwards  Donald J. Rimstidt  Patrick F. Scanlon  Thomas K. Collins  Oliver Schabenberger  Jeffrey B. Birch 《Environmental Geology》2002,41(8):873-882

. A detailed study has been made of the distribution of lead on a public shotgun range in the George Washington – Jefferson National Forests in southwestern Virginia. Sampling of more than 100 sites has yielded data on the distribution pattern of the lead shot. Since opening in 1993 through 2000, 11.1 metric tons (t) of lead have been accumulated over an area 220쑼 m (66,000 m²) with an average rate of accumulation of 1.4 t/year. More than 85% of the total dispersed lead lies scattered in the forest that surrounds the approximately 60Ꮔ-m cleared shooting surface. Lead is irregularly distributed because of the use of stationary targets and the general trajectory of launched clay targets. Maximum concentrations occur at distances of ~28, ~80, and ~180 m, and reach a maximum value of more than 5,000 g/m². Significant amounts of fine particulate lead, generated during shooting and as a result of impact occur close to the shooting box, but are absent at distances beyond 50 m.  相似文献   

Surface-Focused Seismic Holography of Sunspots: I. Observations     

D. C. Braun  A. C. Birch 《Solar physics》2008,251(1-2):267-289

We present a comprehensive set of observations of the interaction of p-mode oscillations with sunspots using surface-focused seismic holography. Maps of travel-time shifts, relative to quiet-Sun travel times, are shown for incoming and outgoing p modes as well as their mean and difference. We compare results using phase-speed filters with results obtained with filters that isolate single p-mode ridges, and we further divide the data into multiple temporal frequency bandpasses. The f mode is removed from the data. The variations of the resulting travel-time shifts with magnetic-field strength and with the filter parameters are explored. We find that spatial averages of these shifts within sunspot umbrae, penumbrae, and surrounding plage often show strong frequency variations at fixed phase speed. In addition, we find that positive values of the mean and difference travel-time shifts appear exclusively in waves observed with phase-speed filters that are dominated by power in the low-frequency wing of the p ₁ ridge. We assess the ratio of incoming to outgoing p-mode power using the ridge filters and compare surface-focused holography measurements with the results of earlier published p-mode scattering measurements using Fourier?–?Hankel decomposition.  相似文献   

Surficial sediments on the continental margin off the west coast of South Africa     

G.F. Birch 《Marine Geology》1977,23(4):305-337

A combination of climatic and oceanic factors has resulted in slow sedimentation rates on the continental shelf off the west coast of South Africa since Tertiary times. This has enabled a study to be made of the residual Late Tertiary, relict Pleistocene and Holocene sediments.Sediments on the continental shelf form rough belts parallel to the coast. Most of the coarse sediment is confined to the littoral zone and Holocene mud is concentrated at the base of a rocky nearshore platform. A veneer of Quaternary quartzitic sand seawards of the Recent mud belt wedges out onto a Tertiary erosion surface on the mid shelf. Residual glauconite and phosphorite sands derived by erosion during Tertiary sea-level fluctuations cover large parts of the mid shelf in the south. Most of the slope and parts of the outer shelf in the north are draped by Recent foraminiferal and coccolithophorid debris.  相似文献   

Erratum: Linear sensitivity of helioseismic travel times to local flows     

A. C. Birch  L. Gizon  R. Burston 《Astronomische Nachrichten》2011,332(6):658-658

We fix three typographical errors in “Linear Sensitivity of Helioseismic Travel Times to Local Flows” (Astronomische Nachrichten, Vol. 328, Issue 3, p. 228) (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献