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This paper assesses the key contributions made by Piers Blaikie to the field of political ecology. Those contributions relate to the way in which this scholar has sought to dismantle barriers to thought by: (1) integrating the insights of political economy with those from environmental science, (2) opening up theoretical space in political ecology by engaging fruitfully with post-structural critiques, (3) moving beyond a narrow area-studies and development studies focus, and (4) helping to internationalise the research field beyond its core American base. The paper also highlights ambiguity in the role played by Blaikie in political ecology, as stances that he has taken in his work have provoked wider debate over the field’s purpose and coherence. Ensuing tensions over theory and practice as well as single versus multiple truths persist yet, pace Blaikie and others (e.g. Robbins), a robust political ecology is nonetheless able to consider what people ‘do’ from a healthy diversity of theoretical positions. The multiple contributions of Piers Blaikie underpin a reputation for having produced a pioneering body of work that has inspired scholars across theoretical, empirical and disciplinary boundaries, thereby ensuring that his will be a reputation that is interpreted and re-interpreted for many years to come. 相似文献
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大同晚期强余震前震源机制解的一致性特征 总被引：6，自引：0，他引：6
取层状介质中一点源位错模型，由计算综合地震图得到P、S各自最大振幅，通过其最大振幅比值与观测资料拟合的方式来确定震源机制。大同遥测地震台网较好地记录了大同地震序列的大量小震。经系统地查阅台网和周围其他台站1990-2002年的全部记录，读取垂直向的P、S最大振幅数据，反演计算得到620个小地震的震源机制解。这些解的优势取向和华北构造应力场的方向相同。定义各个震源机制解的P、N、T轴和构造应力场的3个应力主轴在3维空间的夹角之和为一致性参数，发现在1991年和1999年发生的晚期强余震前2-8个月，一致性参数出现显著的下降。我们认为，这是具有短期预测意义的现象。 相似文献
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将多通道相关分析方法用于宽频带地震仪的自噪声检测,测量分析了Reftek 130、130 B和130 S三种地震数据采集器的自噪声检测结果以及14套Reftek 130 S连接Guralp CMG-3T地震计的自噪声一致性检测结果,同时给出了地震计的三轴正交性估计.结果表明:Reftek数据采集器设置为普通增益时在0.3 Hz以上频段自噪声高于Guralp CMG-3T地震计自噪声,设置为32倍高增益时在测量频段远低于地震计自噪声;测量的多台Guralp CMG-3T地震计自噪声结果在不同频段一致性差异较大,垂直向分量0.3 Hz以下频段可作为一致性比对参考频段,采集配置选择普通增益时0.3~2 Hz频段可作为数据采集器一致性比对参考频段;Guralp CMG-3T地震计三轴正交性误差估计平均在0.5°以内. 相似文献
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突出地震数据振幅空间不连续性的断层增强属性体是断层自动解释的基础,而如何压制噪声、地层残余响应、角度不整合接触等伪断层的影响是断层自动检测的关键问题之一.在指纹图像边缘检测处理中,一致性是对指示局部方向场信息各向异性强度的一个度量,本文将其作为一种新的断层增强属性引入到地震数据处理中.为了更有效地压制噪声,本文通过对一致性进行加权处理,再结合蚁群算法,提出了新的断层自动检测方法——基于加权一致性的蚁群算法.理论地震模型和实际地震数据的处理结果表明,对于相同的断层检测过程,对比常规的基于方差属性的蚁群算法和基于C3相干属性的蚁群算法,本文所提方法不仅更有效地压制了噪声和地层残余响应产生的伪断层信息,而且更完整地展现了断层的延伸长度,同时具有更高的稳定性和计算效率. 相似文献
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The effective elastic thickness, Te, has been calculated in the collision zone between Arabia and Eurasia in Iran from the wavelet coherence. The wavelet coherence is calculated from Bouguer anomalies and topography data using the isotropic fan wavelet method, and gives Te values between 14.2 and 62.2 km. The lower value is found in the Central Iranian Blocks and the East Iranian Belt which are bounded by several large strike-slip faults with lithospheric origin. The higher value occurs in the east of the South Caspian Sea Basin. The resulting Te map shows positive and negative correlation with shear wave velocity and surface heat flow, respectively. A comparison between the seismogenic thickness (Ts) and Te in Iran suggests that Te > Ts. Results of the load ratio in Iran indicate that in most of the study area surface loads are much more prevalent than subsurface loads, except in the Central Iranian Blocks and NW of Iran. Intermediate to low Te values in Iran were inherited from multiple rifting and orogenic activities from Late Precambrian (∼650 Ma) to present day which are not only reflected in thin and warm lithosphere but also an increasing seismicity rate. 相似文献
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The spatial properties of events in the 1997 Colfiorito–Sellano seismic sequence (Northern Apennines, Italy) were investigated using coherence, a parameter derived from seismic moment tensors that quantifies the kinematic similarity between focal mechanisms. The 1997 Colfiorito–Sellano seismic sequence predominantly consists of normal faulting earthquakes, with a few strike-slip and reverse faulting episodes. This kinematic heterogeneity is possibly related to the contemporaneous activity of two different sets of faults: NW–SE normal faults and NNE–SSW sub-vertical faults, the latter inherited from the previous Miocene compressional phase. The study used two independently-derived data sets of the same seismic sequence characterized by a different number of events and by different precision of spatial localisation. Their statistical significances, assessed through a reshuffling procedure, reveal that data sets with at least some hundreds of events and good positional precision are required to obtain significant results through coherence analysis. Results from the better quality data set indicate that this seismic sequence is characterized by a rapid decrease in the kinematic similarity between earthquake pairs within 2 km of separation, particularly along directions sub-perpendicular to the normal fault strike. The decrease rate seems to be controlled by the geometric characteristics of the normal faults, given that the mean along-dip distance between fault segments is 2 km. In proximity to pre-existing tectonic lineaments the relative abundance of strike-slip and reverse faults tends to decrease the kinematic similarity between events but does not influence the coherence decrease rate. The presence of mixed focal mechanisms (normal, reverse and strike-slip) in a single seismic phase implies that mixed fault types are not restricted to polyphase tectonic histories: such heterogeneous kinematics during a single phase may be induced by the presence of inherited discontinuities. 相似文献
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合成孔径雷达干涉测量(InSAR)是雷达微波遥感技术的一个新研究领域.以往InSAR遥感应用研究主要集中在通过利用雷达回波信号所携带的相位信息来获取地表高程信息方面.随着InSAR研究的不断深入,干涉相位相关性中所包含的丰富信息越来越受到人们的重视,其应用领域也在不断扩大.本文所提出的基于合成孔径雷达影像干涉相位相关性信息的SAR彩色图像合成方法就是在这一新兴领域上的一个研究尝试.它能将不同类型的地物以不同的颜色直观地显示在图像上,弥补了SAR图像在遥感应用上的不足.该方法非常适合林业资源监测等方面的遥感应用研究. 相似文献
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In practical applications of area-to-point spatial interpolation, inequality constraints, such as non-negativity or more general constraints on the maximum and/or minimum attribute value, should be taken into account. The geostatistical framework proposed in this paper deals with the spatial interpolation problem of downscaling areal data under such constraints, while: (1) explicitly accounting for support differences between sample data and unknown values, (2) guaranteeing coherent (mass-preserving) predictions, and (3) providing a measure of reliability (uncertainty) for the resulting predictions. The formal equivalence between Kriging and spline interpolation allows solving constrained area-to-point interpolation problems via quadratic programming (QP) algorithms, after accounting for the support differences between various constraints involved in the problem formulation. In addition, if inequality constraints are enforced on the entire set of points discretizing the study domain, the numerical algorithms for QP problems are applied only to selected locations where the corresponding predictions violate such constraints. The application of the proposed method of area-to-point spatial interpolation with inequality constraints in one and two dimension is demonstrated using realistically simulated data. 相似文献