Crustal Stress in the northern North Sea as inferred from borehole breakouts and earthquake focal mechanisms     

C.D. Lindholm  H. Bungum  R.K. Bratli  B.S. Aadnøy  N. Dahl  B. Tørudbakken  K. Atakan 《地学学报》1995,7(1):51-59

The regional stress field in the northern North Sea (offshore western Norway) has been studied through the acquisition and analysis of directions of maximum horizontal compression (_H) as extracted from borehole breakouts and from earthquake focal mechanism solutions.
The results indicate that the regional stress field is dominated by NW-SE compression, with good consistency between shallow borehole breakouts (2–5 km depth) and deeper earthquakes (10–25 km depth). The broad spatial consistency in stress direction indicates that the main stress field is related to factors of primarily plate tectonic origin, and the results are in good agreement with the western Europe trend found in earlier investigations.
The Tampen Spur region in the northern North Sea has been subjected to particularly complex deformation, with two dominating fault directions trending NW-SE and NE-SW. From Tampen Spur in the west to the Sogn graben in the east an anomalous stress field is indicated, with NE-SW oriented maximum horizontal compressions. This anomaly is clearly seen both in the borehole breakout data and in the earthquake data. Possible sources for this anomaly are discussed, and include postglacial uplift and/or lateral variations in the physical properties of the crust.  相似文献   

Two types of extremely short lasting decimetric bursts and their possible relation to processes in solar magnetic traps     

Øystein Elgarøy  Ole P. Sveen 《Solar physics》1973,32(1):231-240

High resolution spectral observations between 500 MHz and 550 MHz on 1972 October 25, revealed an emission event of special interest. The main feature was bursts with a single frequency duration of about 0.09 s and with a bandwidth of the same order of magnitude as the band covered by the spectrograph. The bursts occurred in showers' which lasted for one or two minutes and which were separated by quiet intervals of roughly the same length. Frequently the activity assumed a periodic nature. Periods between 0.1 s and 0.3 s were found. The most remarkable feature of the records was a very large number of bursts with the same duration as the wide band bursts, but showing a bandwidth of a mere 1–2 MHz.The wide band bursts may be plasma waves excited by proton streams trapped in coronal magnetic fields and the narrow band bursts may possibly be explained as perpendicular electrostatic electron cyclotron waves.  相似文献   

Stable Isotope Ratios: Hurricane Olivia   总被引：1，自引：0，他引：1  

James R. Lawrence  Stanley David Gedzelman  John Gamache  Michael Black 《Journal of Atmospheric Chemistry》2002,41(1):67-82

The oxygen and hydrogen isotopic compositions of rains from HurricaneOlivia (1994) in the eastern Pacific were measured. The rains werecollected on 24 and 25 September during airplane flights conducted at anelevation of 3 km. Hurricane Olivia peaked in intensity to a category-4storm between the two dates. Isotope ratios of rains from HurricaneOlivia were markedly lower ( ¹⁸O = –13.9to –28.8) than that of rain collected from a thunderstormat an elevation of 2.3 km outside the influence of Olivia (¹⁸O = –3.8). A distinct decrease in isotoperatios from the first day to the next ( ¹⁸O =–18.4 to –21.9) in Hurricane Olivia wasattributed to decreased updraft velocities and outflow aloft. Thisshifted the isotopic water mass balance so that fewer hydrometeors werelifted and more ice descended to flight level. A decrease in the averagedeuterium excess from the first day to the next (d = 15.5 to 7.1)was attributed to an increase in the relative humidity of the watervapor `source' area. We hypothesize that the `source' region for therain was in the boundary layer near the storm center and that becausethe hurricane was at peak intensity prior to the second day the relative humidity was higher.  相似文献   

Mercury concentrations in the fur of steller sea lions and northern fur seals from Alaska     

Beckmen KB  Duffy LK  Zhang X  Pitcher KW 《Marine pollution bulletin》2002,44(10):1130-1135

We compared total mercury (THg) concentrations in the fur of northern fur seals (Callorhinus ursinus) from the depleted Pribilof Islands population with those of both declining and thriving populations of Steller sea lions (Eumetopias jubatus) from Prince William Sound (PWS) and Southeast Alaska (SEA), respectively. Relatively low wet weight concentrations (ranges) of THg were detected in the fur of Steller sea lion (SSL) pups (0.90-3.14 microg/g) and juveniles (0.56-6.75 microg/g) from both areas in 1998 and 2000 compared to northern fur seal (NFS) pups (3.15-8.14 microg/g) in 2000. The mean concentration +/- SD for SSLs sampled were 1.46 +/- 0.64 microg/g for pups (n = 22) and 2.74 +/- 2.89 microg/g for juveniles (n = 6). Analyses indicated higher THg concentrations from SSL pups from PWS compared to the SEA. Mean +/- SD. THg in the NFS pups was 4.90 +/- 1.42 microg/g (n = 34) and for post-partum dams was 7.84 +/- 1.78 microg/g (n = 12).  相似文献   

Threat level green: Conceding ecology for security in eastern Europe and the former Soviet Union   总被引：1，自引：0，他引：1  

Mark Lawrence Schrad   《Global Environmental Change》2006,16(4):400-422

Following the collapse of the Soviet Union, the predicted scenarios of Central Asian water wars and catastrophic nuclear accidents have failed to materialize. However, the Aral Sea continues to shrink apace, and dangerous Soviet-built nuclear reactors have since proliferated in the former eastern bloc. These seemingly paradoxical outcomes can in part be attributed to the framing of these environmental issues as security matters by leading international regulatory, aid and lending institutions. Integrating these environmental concerns with the realist worldview of security studies systematically emphasized security dimensions at the expense of ecological concerns even amongst organizations distant from traditional defense affairs. This article proposes that international security strategy in this period is one of environmental appeasement defined as the systematic granting of ecologically unfriendly concessions in order to reduce short-term security risks. The article presents evidence that this appeasement strategy generated seemingly impressive results in terms of ameliorating short-term security risks, while actually exacerbating the underlying ecological situation. The article argues that while the foundational environmental risks remain unaddressed, the associated security threats have likewise not been ultimately resolved.  相似文献   

The influence of human activity in the Arctic on climate and climate impacts   总被引：1，自引：0，他引：1  

Henry P. Huntington  Michelle Boyle  Gwenn E. Flowers  John W. Weatherly  Lawrence C. Hamilton  Larry Hinzman  Craig Gerlach  Rommel Zulueta  Craig Nicolson  Jonathan Overpeck 《Climatic change》2007,82(1-2):77-92

Human activities in the Arctic are often mentioned as recipients of climate-change impacts. In this paper we consider the more complicated but more likely possibility that human activities themselves can interact with climate or environmental change in ways that either mitigate or exacerbate the human impacts. Although human activities in the Arctic are generally assumed to be modest, our analysis suggests that those activities may have larger influences on the arctic system than previously thought. Moreover, human influences could increase substantially in the near future. First, we illustrate how past human activities in the Arctic have combined with climatic variations to alter biophysical systems upon which fisheries and livestock depend. Second, we describe how current and future human activities could precipitate or affect the timing of major transitions in the arctic system. Past and future analyses both point to ways in which human activities in the Arctic can substantially influence the trajectory of arctic system change.  相似文献   

Parameterisation of orographic cloud dynamics in a GCM     

S. M. Dean  J. Flowerdew  B. N. Lawrence  S. D. Eckermann 《Climate Dynamics》2007,28(6):581-597

A new parameterisation is described that predicts the temperature perturbations due to sub-grid scale orographic gravity waves in the atmosphere of the 19 level HadAM3 version of the United Kingdom Met Office Unified Model. The explicit calculation of the wave phase allows the sign of the temperature perturbation to be predicted. The scheme is used to create orographic clouds, including cirrus, that were previously absent in model simulations. A novel approach to the validation of this parameterisation makes use of both satellite observations of a case study, and a simulation in which the Unified Model is nudged towards ERA-40 assimilated winds, temperatures and humidities. It is demonstrated that this approach offers a feasible way of introducing large scale orographic cirrus clouds into GCMs.  相似文献   

A once-molten,coarse-grained,Ca-rich inclusion in Allende     

Glenn J. MacPherson  Lawrence Grossman 《Earth and Planetary Science Letters》1981,52(1):16-24

A compact, spheroidal Type B inclusion in Allende contains melilite laths that project radially inward from the inclusion edge which show interference growth textures. The combined textural and chemical features of this object cannot be explained by independent vapor-solid condensation of grains in space, followed by random aggregation of these grains into an inclusion. Rather, it probably formed from a once-molten droplet that crystallized in response to radiative cooling from its outer surface. The crystallization sequence in this and another similar inclusion in which oxygen isotopes have been measured is: melilite-spinel-anorthite-fassaite. This sequence supports the idea that oxygen isotopic heterogeneities in coarse-grained inclusions were formed after complete solidification of these objects by partial exchange with a less¹⁶O-rich gas, and not during or before a melting event.  相似文献   

Geothermal exploration in the azores: 0/0 in calcites from volcanic rocks     

J.R. Lawrence  S. Maxwell   《Journal of Volcanology and Geothermal Research》1978,4(3-4)

The oxygen isotope composition of calcite veins and vugs in basalts from a drill site on the island of Sao Miguel show near-equilibration with fresh water at observed temperatures only at a depth of 600–700 m. This is interpreted to mean that the greatest flow of hot water may be occurring in this depth interval.  相似文献   

Gypsum and halite from the Mid-Atlantic Ridge,DSDP Site 395     

James I. Drever  James R. Lawrence  Ronald C. Antweiler 《Earth and Planetary Science Letters》1979,42(1):98-102

Gypsum and halite crystals, together with saponite and phillipsite, were found in a vein in a basalt sill 625 m below the sea floor at DSDP Site 395A, located 190 km west of the crest of the Mid-Atlantic Ridge. The δ³⁴S value of the gypsum (+19.4‰) indicates a seawater source for the sulfate. The δ¹⁸O values of the saponite (+19.9‰) and phillipsite (+18.1‰) indicate either formation from normal seawater at about 55°C or formation from¹⁸O-depleted seawater at a lower temperature.The gypsum (which could be secondary after anhydrite) was formed by reaction between Ca²⁺ released from basalt and SO₄^2? in circulating seawater. The halite could have formed when water was consumed by hydration of basalt under conditions of extremely restricted circulation. A more probable mechanism is that the gypsum was originally precipitated as anhydrite at temperatures above 60°C. As the temperature dropped the anhydrite converted to gypsum. The conversion would consume water, which could cause halite precipitation, and would cause an increase in the volume of solids, which would plug the vein and prevent subsequent dissolution of the halite.  相似文献