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1.
Body tides on an elliptical, rotating, elastic and oceanless earth 总被引：17，自引：0，他引：17
John M. Wahr 《Geophysical Journal International》1981,64(3):677-703
Summary. The Earth's deformation caused by the luni-solar tidal force is defined as the 'body tide'. We compute the effects of the Earth's rotation and elliptical stratification on the body tide for a number of modern elastic structural models. Rotation and ellipticity within the mantle are found to affect tidal observations by about 1 per cent. A consequence is an improved estimate for the fluid core resonance in the diurnal tidal band. Agreement between results for the different structural models is very good. As a result, the results computed here can be used to model the tidal effects of a globally averaged, oceanless, rotating, elliptical and elastic earth to an accuracy of at least one part in 300. 相似文献
2.
冰芯钻取后，样品截取原则和环境记录的初步解释要求对年代－深度剖面有一初步了解，即要求建立冰体随深度变化的时间尺度。根据柯林斯冰帽一年多野外实测资料所揭示的小冰穹运动状况、温度分布、物质平衡和动力学特征，本文采用Ｄａｎｓｇａｒｒｄ－Ｊｏｈｎｓｅｎ模型和等温冰体流动模型（ｎ＝３），分别对一支８０．２ｍ冰芯的时间尺度进行初步估算。结果表明两种模型断代结果非常接近，在距冰床１０ｍ深度处，两模型分别给出１８９７年和１８５４年的冰龄。对比指出两种模型计算出的冰帽各深度冰龄最大误差不大于２％。与冰芯中上部含深褐色火山灰冰层的历史记录年代相比误差小于３％。 相似文献
3.
矿物和结构分析揭示了南极洲乔治王岛柯林斯冰帽一支 80 .2 m冰芯中的 9层深褐色沉积物的火山灰特征。本文从冰川处于稳定状态的假定出发 ,根据 Dansgaard- Johnsen流动模式断代结果 ,建立了南设得兰群岛火山喷发序列。依冰芯记录判断 ,该区 1 650年以来的 340年间 ,共有 7轮火山喷发。1 875～ 1 92 5年间似为火山活跃期 ,喷发地点可能主要在欺骗岛 ;1 650～ 1 80 0年间为一相对平静期 ;此后一个世纪不太稳定 ;而过去的 1 0 0年间基本平静 ,只是世纪初和 50～ 70年代间各有一段动荡期。冰芯中记载的大多数火山喷发可在该区有关文献中找到记录。没有记录在案的几例喷发事件需进一步调查。冰芯中缺失 1 967～ 1 970年欺骗岛火山灰层位表明 ,研究得到的火山序列仍未包含所有的喷发事件。但本文展示的该区过去 340年间火山活动基本趋势并不因此而改变。 相似文献
4.
A. Jackson C. G. Constable M. R. Walker R. L. Parker 《Geophysical Journal International》2007,171(1):133-144
We describe a new technique for implementing the constraints on magnetic fields arising from two hypotheses about the fluid core of the Earth, namely the frozen-flux hypothesis and the hypothesis that the core is in magnetostrophic force balance with negligible leakage of current into the mantle. These hypotheses lead to time-independence of the integrated flux through certain 'null-flux patches' on the core surface, and to time-independence of their radial vorticity. Although the frozen-flux hypothesis has received attention before, constraining the radial vorticity has not previously been attempted. We describe a parametrization and an algorithm for preserving topology of radial magnetic fields at the core surface while allowing morphological changes. The parametrization is a spherical triangle tesselation of the core surface. Topology with respect to a reference model (based on data from the Oersted satellite) is preserved as models at different epochs are perturbed to optimize the fit to the data; the topology preservation is achieved by the imposition of inequality constraints on the model, and the optimization at each iteration is cast as a bounded value least-squares problem. For epochs 2000, 1980, 1945, 1915 and 1882 we are able to produce models of the core field which are consistent with flux and radial vorticity conservation, thus providing no observational evidence for the failure of the underlying assumptions. These models are a step towards the production of models which are optimal for the retrieval of frozen-flux velocity fields at the core surface. 相似文献
5.
We investigate the importance of wide-band coupling of normal modes due to inner core anisotropy. We compare four different seismic models of inner core anisotropy, which were obtained by others using the splitting of Earth's normal modes. These models have been developed using a self-coupling (SC) approximation, which assumes that coupling between nearby modes through anisotropic inner core structure is negligible. We test the SC approximation by comparing the frequencies and quality factors of 90 inner core sensitive modes, computed for these models using either the SC approximation or full-coupling (FC) among large groups of modes. We find significant shifts in the quality factors and frequencies for some modes. Groups of modes which significantly couple together are constructed for six target modes. These groups are model dependent and in some cases contain large numbers of modes. Synthetic seismograms are calculated to show that the difference between SC and FC is observable on the scale of seismograms and of the same order of magnitude as the difference between synthetic and observed seismograms. Thus, future models of inner core anisotropy should take cross-coupling between large groups of modes into account. 相似文献
6.
Summary. The method of stochastic inversion, previously applied to secular variation data, is applied to main field data. Adaptations to the method are required: non-linear, as well as linear, data are used; allowance is made for crustal components in the observatory data; and the prior information is specified differently. The requirement that the models should satisfy a finite lower bound on the Ohmic heating in the core provides strong prior information and gives finite error estimates at the core—mantle boundary.
The new method is applied to data from the epochs 1969.5 and 1980.0. The resulting field models are very much more complex than other models, such as the IGRF models extrapolated to the core, and show considerable small-scale detail which, on the basis of the error analysis, can be believed.
The flux integral over the northern hemisphere is computed at each epoch; the difference between the two epochs is approximately one standard deviation, suggesting that the question as to whether the decay of the dipole is consistent with the frozen-flux hypothesis has been resolved in favour of the hypothesis. 相似文献
The new method is applied to data from the epochs 1969.5 and 1980.0. The resulting field models are very much more complex than other models, such as the IGRF models extrapolated to the core, and show considerable small-scale detail which, on the basis of the error analysis, can be believed.
The flux integral over the northern hemisphere is computed at each epoch; the difference between the two epochs is approximately one standard deviation, suggesting that the question as to whether the decay of the dipole is consistent with the frozen-flux hypothesis has been resolved in favour of the hypothesis. 相似文献
7.
This paper investigates regional inequality and development in China's Guangdong province by employing the multi-scale and multi-mechanism framework. The study further examines the relationship between space, scale, and regional inequality by applying a spatial filtering method that eliminates spatial dependence of the data and quantifies the extent to which spatial effects have contributed to regional inequality at multiple scales. The results suggest that over 90% of the divide between the core of the Pearl River Delta (PRD) and the periphery areas of Guangdong province can be explained by the effect of strengthening spatial dependence. By incorporating spatial filters in space-time models, we also reveal the space-time and core-periphery heterogeneities of development mechanisms. Our study confirms that the integration of a multi-scale and multi-mechanism framework and rigorous spatial analysis methods, such as spatial filtering and space-time modeling, helps better understand the complexity of regional development in China. 相似文献
8.
通达性被认为是评价交通网络的方法中一项综合的、直观的评价指标,并越来越多地被应用到城市规划、区域空间结构与区域经济发展等多种领域。以山东半岛蓝色经济区陆域范围为研究区,通过运用空间句法模型和网络分析算法,获取路网集成度和等时圈数据并进行GIS可视化表达,定量分析研究区路网发育的空间结构性规律。研究结果表明：①蓝色经济区内路网体系发育较为成熟,路网线段集聚明显;线段式空间分布格局呈“点-轴”状发散,轴线式空间分布格局呈“干-枝”状发散,形成了区域内部的核心圈与外围圈的互连互通;②城镇区域可达性在较大程度上取决于区域中心性和周边路网发达程度,而青岛市和潍坊市位于区域的核心位置,通达性好且对整个区域路网的控制作用较为突出。 相似文献
9.
农业产业集群创新通道及溢出效应——以山东寿光蔬菜产业集群为例 总被引：1，自引：0，他引：1
农业产业集群创新是多种关系集聚作用的过程,而现代农业集群发展离不开地方与全球背景下的前后联系,因此研究地方与全球联系下的农业集群创新及其溢出效应具有重要的理论与现实意义。论文以山东寿光蔬菜产业集群为例,利用实地调研数据,运用社会网络分析法和空间计量模型分析集群创新联系的作用通道及溢出效应,研究表明：① 集群地方联系包含强关系的本地企业网络和弱关系的官产学研网络,其中本地企业网络集聚现象较突出,企业间联系紧密,两关系网络中核心企业对资源信息均具有较强控制作用;② 全球通道作为集群外部弱联系,网络联系密度较低,其网络整体显示出结构洞特征,且网络核心节点企业对海外异质性资源表现出较强控制性。在测度集群创新溢出效应方面,空间误差模型较其他模型更优,其中集群本地企业联系、企业间空间邻近、全球关系通道在集群创新中均会起到一定促进作用。进一步机理分析表明,地方联系和全球关系通道在集群创新中发挥着不同的作用,其强弱关系互动是异质性创新资源扩散、吸收与利用的关键。 相似文献
10.
Iñaki Prieto Jose Luis Izkara Rubén Béjar 《International journal of geographical information science》2018,32(2):282-301
Georeferenced 3D models are an increasingly common choice to store and display urban data in many application areas. CityGML is an open and standardized data model, and exchange format that provides common semantics for 3D city entities and their relations and one of the most common options for this kind of information. Currently, creating and maintaining CityGML models is costly and difficult. This is in part because both the creation of the geometries and the semantic annotation can be complex processes that require at least some manual work. In fact, many publicly available CityGML models have errors. This paper proposes a method to facilitate the regular maintenance of correct city models in CityGML. This method is based on the continuous deployment strategy and tools used in software development, but adapted to the problem of creating, maintaining and deploying CityGML models, even when several people are working on them at the same time. The method requires designing and implementing CityGML deployment pipelines. These pipelines are automatic implementations of the process of building, testing and deploying CityGML models. These pipelines must be run by the maintainers of the models when they make changes that are intended to be shared with others. The pipelines execute increasingly complex automatic tests in order to detect errors as soon as possible, and can even automate the deployment step, where the CityGML models are made available to their end users. In order to demonstrate the feasibility of this method, and as an example of its application, a CityGML deployment pipeline has been developed for an example scenario where three actors maintain the same city model. This scenario is representative of the kind of problems that this method intends to solve, and it is based on real work in progress. The main benefits of this method are the automation of model testing, every change to the model is tested in a repeatable way; the automation of the model deployment, every change to the model can reach its end users as fast as possible; the systematic approach to integrating changes made by different people working together on the models, including the possibility of keeping parallel versions with a common core; an automatic record of every change made to the models (who did what and when) and the possibility of undoing some of those changes at any time. 相似文献
11.
论文以高科技园区如何促进智慧产业集聚为研究导向,总结智慧产业集群演化、集聚模式等的研究进展,先基于信息产业的已有分类标准,界定高科技园区智慧产业集群的概念和产业分类;然后基于中关村科技园智慧产业2002—2016年的统计数据,分析中关村科技园智慧产业的空间布局演化和产业增长格局,以波特经典钻石模型为理论框架,细化分析演化过程背后的动力因素,得出高科技园区智慧产业集群的细分动力因素模型,继而以主要动力因素为依据,提炼中关村科技园智慧产业集群演化的主要集聚模式,得出结论:① 中关村科技园区智慧产业集群的演化呈现“一核多园”的先政策引导、后自然溢出的协同发展格局,从海淀核心区向周边园区先辐射集聚,然后基于各园区间的交通、楼宇等生产要素,逐步在非园区范围连贯成片;② 海淀作为核心区集聚了各细分智慧产业,其他各分园则主要在个别细分智慧产业形成集聚优势;③ 中关村科技园区智慧产业的演化主要受生产要素、政府影响变数、相关及支持产业等3大因素影响;④ 中关村科技园区智慧产业集群有生产要素驱动、产业平台驱动、商业地产企业驱动等3种集聚模式。 相似文献
12.
《Geomorphology》1988,1(2):87-109
A model of denudation processes leading to relief inversion is developed for a section of the plunging anticline at Monte Nerone, in the Umbro-Marchean Apennines of central Italy. This model differs from previous schemes, as it applies to an anticline in which only the core consists of resistant rock. Furthermore, erosion, a combination of gullying and mass movement, is concentrated on the flanks rather than the crest of the fold, as strata dip steeply on the former yet are shallow on the latter. Whereas in most models of the geomorphic evolution of anticlines the crest is first to be eroded away, in the case of Monte Nerone it is preserved by scarp retreat from the upper flanks. Cuestas and flatirons have formed on the lower flanks and are in some cases affected by gravitational deformation. Phases of talus production, debris flowage and gullying have occurred in the valleys between the flatirons, thus dissecting the Cretaceous and Tertiary strata on the limbs of the anticline.The denudation of Monte Nerone shows similarities to and differences from other models of the geomorphic evolution of anticlines, and is related in this article to general neotectonic processes and Quaternary sedimentation. 相似文献
13.
Siliceous microfossil assemblage succession was analyzed in a 100 m sediment core from Lake Baikal, Siberia. The core was recovered from the lake's central basin at a water depth of 365 m. Microfossil abundance varied greatly within the intervals sampled, ranging from samples devoid of siliceous microfossils to samples with up to 3.49 × 1011 microfossils g-1 sediment. Fluctuations in abundance appear to reflect trends in the marine 18O record, with peak microfossil levels generally representing climate optima. Microfossil taxa present in sampled intervals changed considerably with core depth. Within each sample a small number of endemic diatom species dominated the assemblage. Changes in dominant endemic taxa between sampled intervals ranged from extirpation of some taxa, to shifts in quantitative abundance. Differences in microfossil composition and the association of variations in abundance with climate fluctuations suggest rapid speciation in response to major climatic excursions. 相似文献
14.
The fjord landscape of South America, stretching ~ 1500 km between Golfo Corcovado (~ 43°S) and Tierra del Fuego (~ 56°S), is the largest continuous fjord landscape on Earth. This paper presents the results of new structural geological and geomorphological mapping of this landscape using optical satellite images and digital elevation models. First-order geological structures are represented by strike-slip faults forming lineaments up to hundreds of kilometres long. The strike-slip faulting has been active since Late Cretaceous times and is responsible for the presence of a conspicuous structural cleavage visible as lineaments up to ~ 10 km long. A detailed analysis of these second-order lineaments from digital image data was carried out in three sectors. In Sector 1, located northwest of the North Patagonian Icefield, there are three distinct mean orientations, characterized by a main nearly orogen-parallel orientation (az. ~ 145°) and two orogen-oblique secondary orientations (az. ~ 20° and az. ~ 65°). In Sector 2, located west of the South Patagonian Icefield, there are also three separate mean orientations, with most of the lineaments concentrated between azimuths 0° and 80° (mean at ~ 36°); and two other orogen-oblique means at azimuth ~ 122° and ~ 163°. In Sector 3, around the Cordillera Darwin, there is a single main orogen-parallel mean at ~ 100–115°. In all three sectors, mapped fjord orientations bear a striking similarity to the structural data, with fjords orientated preferentially in the same direction as structural lineaments. We infer that successive glaciations followed the same ice-discharge routes, widening and deepening pre-existing geological structures at the expense of the surrounding terrain to create the fjord landscape. This study has broader implications for ice sheet reconstructions and landscape evolution beneath ice sheets because we demonstrate that the primary control on fjord development in glaciated areas is geological and not glaciological. 相似文献
15.
Archana Bhattacharyya 《Geophysical Journal International》1998,132(1):181-190
A region of enhanced conductivity at the base of the mantle is modelled by an infinitesimally thin sheet of uniform effective conductance adjacent to the core–mantle boundary. Currents induced in this sheet by the temporally varying magnetic field produced by the geodynamo give rise to a discontinuity in the horizontal components of the poloidal magnetic field on crossing the sheet, while the radial component is continuous across the sheet. Treating the rest of the mantle as an insulator, the horizontal components of the poloidal magnetic field and their secular variation at the top of the core are determined from geomagnetic field, secular variation and secular acceleration models. It is seen that for an assumed effective conductance of the sheet of 108 S, which may be not unrealistic, the changes produced in the horizontal components of the poloidal field at the top of the core are usually ≤10 per cent, but corrections to the secular variation in these components at the top of the core are typically 40 per cent, which is greater than the differences that exist between different secular variation models for the same epoch. Given the assumption that all the conductivity of the mantle is concentrated into a thin shell, the present method is not restricted to a weakly conducting mantle. Results obtained are compared with perturbation solutions. 相似文献
16.
Summary. We present a model of the magnetic field at the core–mantle boundary, for epoch 1959.5, based on a large set of observatory and survey measurements. Formal error estimates for the radial field at the core are 50 μT, compared with 30 and 40 μT for our previous MAGSAT (1980) and POGO (1970) models.
Current work on the determination of the velocity of the core fluid relies on the assumption that the core behaves as a perfect conductor, so that the field lines remain frozen to the fluid at the core surface. This frozen-flux condition requires that the integrated flux over patches of the core surface bounded by contours of zero radial field remain constant in time. A new method is presented for constructing core fields that satisfy these frozen-flux constraints. The constraints are non-linear when applied to main field data, unlike the case of secular variation which was considered in an earlier paper. The method is applied to datasets from epochs 1969.5 and 1959.5 to produce fields with the same flux integrals as the 1980 model.
The frozen-flux hypothesis is tested by comparing the changes in the flux integrals between 1980/1969.5, 1969.5/1959.5 and 1980/1959.5 with their errors. We find that the hypothesis can be rejected with 95 per cent confidence. The main evidence for flux diffusion is in the South Atlantic region, where a new null flux curve appears between 1960 and 1970, and continues to grow at a rapid rate from 1970 to 1980. However, the statistical result depends critically on our error estimates for the field at the core surface, which are difficult to assess with any certainty; indeed, doubling the error estimates negates the statistical argument. The conclusion is therefore, at this stage, tentative, and requires further evidence, either from older data, if good enough, or from future satellite measurements. 相似文献
Current work on the determination of the velocity of the core fluid relies on the assumption that the core behaves as a perfect conductor, so that the field lines remain frozen to the fluid at the core surface. This frozen-flux condition requires that the integrated flux over patches of the core surface bounded by contours of zero radial field remain constant in time. A new method is presented for constructing core fields that satisfy these frozen-flux constraints. The constraints are non-linear when applied to main field data, unlike the case of secular variation which was considered in an earlier paper. The method is applied to datasets from epochs 1969.5 and 1959.5 to produce fields with the same flux integrals as the 1980 model.
The frozen-flux hypothesis is tested by comparing the changes in the flux integrals between 1980/1969.5, 1969.5/1959.5 and 1980/1959.5 with their errors. We find that the hypothesis can be rejected with 95 per cent confidence. The main evidence for flux diffusion is in the South Atlantic region, where a new null flux curve appears between 1960 and 1970, and continues to grow at a rapid rate from 1970 to 1980. However, the statistical result depends critically on our error estimates for the field at the core surface, which are difficult to assess with any certainty; indeed, doubling the error estimates negates the statistical argument. The conclusion is therefore, at this stage, tentative, and requires further evidence, either from older data, if good enough, or from future satellite measurements. 相似文献
17.
Geoffrey F. Davies 《Geophysical Journal International》1986,84(1):153-183
Summary. Numerical convection models are presented in which plates are simulated by imposing piecewise constant horizontal velocities on the upper boundary. A 4 × 1 box of constant viscosity fluid and two-dimensional (2-D) flow is assumed. Four heating modes are compared: the four combinations of internal or bottom heating and prescribed bottom temperature or heat flux. The case with internal heating and an isothermal base is relevant to lower mantle or whole mantle convection, and it yields a lower thermal boundary layer which is laterally variable and can be locally reversed, corresponding to heat flowing back into the core locally. When scaled to the whole mantle, the surface deflections and gravity and geoid perturbations calculated from the models are comparable to those observed at the Earth's surface. For models with migrating ridges and trenches, the flow structure lags well behind the changing surface 'plate'configurations. This may help to explain the poor correlation between the main geoid features and plate boundaries. Trench migration substantially affects the dip of the cool descending fluid because of induced horizontal shear in the vicinity of the trench. Such shear is small for whole mantle convection, but is large for upper mantle convection, and would probably result in the Tonga Benioff zone dipping to the SE, opposite to the observed dip, for the case of upper mantle convection. 相似文献
18.
A 2-D time-dependent finite-difference numerical model is used to investigate the thermal character and evolution of a convecting layer which is cooling as it convects. Two basic cooling modes are considered: in the first, both upper and lower boundaries are cooled at the same rate, while maintaining the same temperature difference across the layer; in the second, the lower boundary temperature decreases with time while the upper boundary temperature is fixed at 0°C. The first cooling mode simulates the effects of internal heating while the second simulates planetary cooling as mantle convection extracts heat from, and thereby cools, the Earth's core. The mathematical analogue between the effects of cooling and internal heating is verified for finite-amplitude convection. It is found that after an initial transient period the central core of a steady but vigorous convection cell cools at a constant rate which is governed by the rate of cooling of the boundaries and the viscosity structure of the layer. For upper-mantle models the transient stage lasts for about 30 per cent of the age of the Earth, while for the whole mantle it lasts for longer than the age of the Earth. Consequently, in our models the bulk cooling of the mantle lags behind the cooling of the core-mantle boundary. Models with temperature-dependent viscosity are found to cool in the same manner as models with depth-dependent viscosity; the rate of cooling is controlled primarily by the horizontally averaged variation of viscosity with depth. If the Earth's mantle cools in a similar fashion, secular cooling of the planet may be insensitive to lateral variations of viscosity. 相似文献
19.
Eric P. Nelson Katherine A. Connors Claudio Suárez S. 《Natural Resources Research》2007,16(2):171-190
The risk of slope failure in the Chuquicamata open-pit mine was analyzed using Geographic Information System (GIS) software
and modeling techniques. Models incorporated various component layers at a relatively large map scale (1:5000): alteration,
geotechnical unit, proximity to major faults (VIF), GSI (geological strength index), slope (from digital elevation model),
proximity to watertable (difference grid between topography and modeled watertable), and composite structural density grid
(VIF, smaller faults, and fracture frequency); not all layers were used in all models. Three modeling techniques were used:
fuzzy logic, in which parameters in each component layer were ranked by mine geotechnical experts according to their influence
in promoting slope failure, and two data-driven techniques, weights-of-evidence and logistic regression, in which statistical
correlation of training points (known failures) with parameters were used to derive a relative probability of failure. Because
most slope failures are controlled by structure, VIF and smaller faults were divided by orientation into subsets with dip
direction parallel, opposite, and normal to slope aspect; these orientations promote circular and planar, toppling, and wedge-type
failures, respectively. Density grids of these subsets show high-risk areas for individual failure types.
The models demonstrate sensitivity of the analysis to (1) selection of component layers, (2) selection of training points,
(3) classification and ranking of categorical parameters, and (4) data problems in certain layers. Predicted high-risk zones
in the final models show a high degree of correspondence with recent, post-model failures. Such models can be used to anticipate
future pit design concerns. The results presented here illustrate how vast amounts of data, in multiple geo-referenced layers,
can be analyzed and modeled using GIS techniques for predictive studies at relatively large map scales. Such modeling techniques
could provide a powerful tool for predictive modeling in a vast array of large-map-scale applications requiring similar data
integration and evaluation. 相似文献
20.
Apatite fission‐track (FT) and (U–Th)/He analyses are used to constrain the low‐temperature thermal history of the San Gabriel and San Bernardino Mountains (SGM and SBM), which are part of the southern California Transverse Ranges. FT ages from 33 SGM samples range from 3 to 64 Ma. Helium ages, ranging from 3 to 43 Ma, were obtained from 13 of these samples: all of the He ages are the same or younger than their respective FT ages. FT ages from 10 SBM samples were older, ranging from 45 to 90 Ma. The FT and He data document at least three phases of cooling in the SGM, but only two in the SBM. Prior to ~7 Ma, the thermal history of the SGM appears to have been nearly identical to many of the core complexes in the Basin and Range of south‐eastern California: a major phase of cooling is indicated from ~60 to 40 Ma, with a more recent phase beginning at ~23 Ma and continuing until ~10 Ma. The similarity of this timing to that of core complexes suggests that the SGM also originated as a core complex, when the rocks were adjacent to the Chocolate–Orocopia Mountains, and that some of the range‐bounding faults were initially extensional. In the SBM, the two phases of cooling documented by the FT data occurred from ~65 to 55 Ma, and from ~18 Ma to the present. The timing on the second phase is very poorly constrained and, therefore, we do not speculate on the origin of the SBM. The most recent phase of cooling appears to have begun at ~7 Ma in the SGM, as the result of the onset of contractional deformation. A more accelerated phase of cooling may have begun at ~3 Ma. Distinct variations in the total amounts and rates of cooling between different fault‐bounded blocks within the SGM are documented since 7 Ma. We use these variations in cooling rates to calculate denudation rates, which are then compared to topographic characteristics for each structural block. These comparisons suggest that more rapid bedrock uplift in the eastern and southern part of the range has strongly affected the present‐day physiography. Despite a higher mean elevation, the SBM are much less dissected than the SGM, suggesting that the most recent phase of cooling and bedrock uplift began in the last 3 Myr, much later than the initiation of recent bedrock uplift in the SGM. 相似文献