Controls on Rayleigh wave amplitudes: attenuation and focusing

A large data set of amplitude measurements of minor and major arc Rayleigh waves in the period range 73–171 s is collected. By comparing these amplitudes with the amplitudes of synthetic waveforms calculated by mode summation, maps of lateral variations in the apparent attenuation structure of the Earth are constructed. An existing formalism for predicting the effects of focusing is employed to calculate amplitude perturbations for the same data set. These perturbations are used to construct 'pseudo‐attenuation' maps and these results are compared with the apparent attenuation maps calculated from the data. It is shown that variations in Rayleigh wave amplitude perturbations in the Earth are dominated by attenuation at long wavelengths (below about degree 8) and by elastic structure at shorter wavelengths. It is also shown that the linear approximation for focusing is successful at predicting Rayleigh wave amplitudes using existing phase velocity maps. These results indicate that future attempts to model the velocity structure of the Earth would be assisted by incorporating amplitude data and by jointly inverting for Q structure.     

Strengthening conceptual foundations: Analysing frameworks for ecosystem services and poverty alleviation research

A research agenda is currently developing around the linkages between ecosystem services and poverty alleviation. It is therefore timely to consider which conceptual frameworks can best support research at this nexus. Our review of frameworks synthesises existing research on poverty/environment linkages that should not be overlooked with the adoption of the topical language of ecosystem services. A total of nine conceptual frameworks were selected on the basis of relevance. These were reviewed and compared to assess their ability to illuminate the provision of ecosystem services, the condition, determinants and dynamics of poverty, and political economy factors that mediate the relationship between poverty and ecosystem services. The paper synthesises the key contributions of each of these frameworks, and the gaps they expose in one another, drawing out lessons that can inform emerging research. Research on poverty alleviation must recognize social differentiation, and be able to distinguish between constraints of access and constraints of aggregate availability of ecosystem services. Different frameworks also highlight important differences between categories of services, their pathways of production, and their contribution to poverty alleviation. Furthermore, we highlight that it is important to acknowledge the limits of ecosystem services for poverty alleviation, given evidence that ecosystem services tend to be more associated with poverty prevention than reduction. We conclude by reflecting on the relative merits of dynamic Social–Ecological Systems frameworks versus more static checklists, and suggest that research on ecosystem services and poverty alleviation would be well served by a new framework distilling insights from the frameworks we review.     

Surface waves and free oscillations in a regionalized earth model

Summary. The linearized equation is derived which relates observed long-period seismic waveforms to the aspherical perturbations of a spherically symmetric earth model. This is accomplished by formulating the theory of spectral splitting in the time domain. It is shown to be possible greatly to simplify the resulting equations in a way which makes it apparent that for each modal multiplet the 'scattered' field depends only upon three local functional of earth structure. The effect of regional structural variations may then be quantified in a manner analogous to that assumed in the 'pure path technique', but without making the usual asymptotic approximations. These results are used to investigate the validity of the asymptotic result for the locations of the centroids of spectral peaks in individual recordings, for a regionalized model of the Earth. A technique is suggested for retrieving information about geographical structural variations from low-frequency waveform data.     

The effects of source,rate and placement of nitrogen and phosphorus fertilizers on growth of Spartina alterniflora transplats in North Carolina

The effects of rate of N and P fertilizer, type of fertilizer material and application method on establishment, growth and tissue nutrient concentrations of Spartina alterniflora were evaluated on an eroding estuarine shoreline. Both N and P were growth limiting factors at the test site. Biomass increased with increasing rates of N and P up to 224 kg per ha N and 49 kg per ha P when ammonium sulfate and concentrated superphosphate were banded at planting. There were only slight increases in growth when either N or P were applied alone. Placement of fertilizer below ground was necessary; there was no growth response to surface application at transplanting time. The slow-release fertilizers, Mag Amp and Osmocote, supplied N over a longer period of time and produced more growth than the other sources of N which were tested. Urea and urea-formaldehyde were ineffective sources of N. Concentrated superphosphate was as effective as the slow-release fertilizers as a source of P. Nitrogen concentrations in fertilized plants which produced more biomass were lower than in those plants stunted by lack of N or P except where near optimum amounts of N were supplied by the slow-release fertilizers. Residual effects of the fertilizer were evident the second growing season but top-dressing with N and P was necessary to maintain a vigorous stand. Accumulation of up to 28 cm of sand in 2 years was evidence of reduction of shoreline erosion.     

准噶尔盆地滴西地区石炭系火山岩识别与预测

准噶尔盆地腹部滴西地区石炭系火山岩储层中已获重要的工业气流。然而由于成岩环境复杂,岩性多变,火山机构受后期风化剥蚀和构造作用的影响,保存不完整,使得该区火山岩研究难度大,认识程度较低。本文对滴西地区石炭系巴塔玛依内山组火山岩特征进行了研究,分析了该区典型岩性的岩心、岩石薄片及测井响应特征,提出了一套火山岩测井识别的方法。在此基础上,总结了典型岩性组合的地震反射特征,并对岩性的展布情况进行了预测。最后,对火山岩形成的环境进行了探讨。研究结果显示,滴西地区巴塔玛依内山组顶面的火山岩分布具有一定的分段特征,可以分为东部、中部、西部三段: 从成分上看,东部以酸性岩为主,西部以基性岩为主,中部则酸性岩、中性岩和基性岩皆较发育; 从火山岩产状上看,东部和西部以喷出产状为主,中部则侵入产状和喷出产状皆发育。巴塔玛依内山组火山岩体具有多期次的特点,各火山机构彼此叠置,时间和空间上具有一定的相关性。层状火山机构发育。本文的研究方法对准噶尔盆地内石炭系火山岩研究及火山机构的解剖具有借鉴意义,同时也为该区的油气勘探和开发提供一定的依据。