断裂带震源机制节面聚类确定断裂带产状方法及在2021年漾濞地震序列中的应用

一条断裂带上发生地震的破裂面通常与断裂带形状接近,同一地震破裂带上大量震源机制节面中应该有集中于断层面形状的一个集合,求出此集合的节面中心就可以得到断裂带的几何形状.根据这个原理,本研究给出了震源机制节面之间距离的方法,将带有噪声、基于密度的空间聚类方法(DBSCAN)应用于震源机制的节面聚类分析,并应用于2021年云...     

新源、和静交界ML6.8级地震序列应力降和震源机制研究

Based on the digital waveform data recorded by Xinjiang Digital Seismic Network for the Xinyuan-Hejing M_L6.8 earthquake sequences of June 30,2012,this paper analyzes the stress drops of earthquake sequences and the correlation coefficients of focal mechanisms significant for strong aftershocks.Firstly,the source parameters of the Xinyuan-Hejing M_L6.8 earthquake sequences are obtained by applying the spectrum analysis and the Brunes source model.Then,the correlation coefficients of spectral amplitudes are calculated using the low-frequency spectral amplitude recorded by the same station for the different events.Finally,based on the results of the correlation coefficients of spectral amplitudes,the events with similar focal mechanisms are grouped using the clustering method.The results show that:(1)The stress drop values show a steady trend in the aftershock sequence calm period and the stress drop values show a rise-fall in strong aftershocks.(2)The moving average correlation coefficient of amplitude spectrum begins to spread after the main shock.It shows that the correlation decreases between the main shock and the aftershocks in mechanisms.(3)The results of focal mechanism groups show that the earthquake sequences are mainly strike slips.The stress distribution of the main pressure axis is nearly NS,which is the same as the structural stress field.(4)The magnitude and mechanism show that there is an agreement before the strong aftershock,which shows that the regional stress field is enhanced.     

企业创新网络与多维邻近性关系研究述评

创新是引领经济发展的第一动力,企业创新网络相关研究近来受到经济地理学者的高度关注,纵观当前国内外企业创新网络相关研究文献,企业创新网络研究经历了从定性研究向定量研究转变的过程,尤其是基于专利或论文数据刻画创新网络结构特征成为当前研究的热点,然而企业创新网络结构形成的内在机制仍不够深入,不少学者引入多维邻近性框架用于解析企业创新网络形成的重要视角。本文正是基于这一背景,从企业创新网络的影响因素、演化动力及机理、典型案例企业创新网络三个方面梳理了当前经济地理学者的研究热点,并重点基于多维邻近性视角评述了企业创新网络运行机理。研究发现,众多邻近性中,地理、认知和组织邻近对企业创新合作具有较为重要的促进作用,在未来研究中还需加强最佳邻近尺度、不同邻近性替代或互补作用和重要性排序等问题的相关研究。     

基于密度峰值聚类的中尺度涡轨迹自动追踪方法

中尺度涡信息的提取包括涡旋的识别和轨迹追踪,其自动识别与追踪对于基于海量数据的中尺度涡分析十分重要。传统涡旋轨迹自动追踪方法一般需要预先设定搜索半径的阈值,存在一定的主观性。针对传统中尺度涡轨迹追踪方法存在的问题,论文从聚类的角度出发,提出基于密度峰值聚类算法实现对涡旋轨迹的自动追踪,并以南海中尺度涡追踪为例,将基于聚类的追踪算法与传统的相似度追踪算法进行比较分析。结果表明:（1）基于密度峰值聚类算法,可实现对海洋中尺度涡的自动追踪,该算法涡旋追踪准确率优于传统相似度算法;（2）该涡旋追踪算法对资料的完整性依赖度较低,特别是对于存在部分缺损数据的情况仍能较准确追踪;（3）该追踪算法克服了传统涡旋追踪算法需要预先设定搜索半径阈值的问题,自适应性更强。     

关于上海地质资料信息服务集群化和产业化探索与实践

实施地质资料信息服务集群化和产业化战略,是促进地质工作更加紧密地与经济社会发展相结合,更加主动地为经济社会发展服务,构建以社会需求为导向的地质工作服务新机制的重要战略部署。通过加强地质资料汇交制度和社会共享机制建设,扩大了地质资料信息源,地质资料信息集群化初见成效;围绕地质资料信息服务的社会需求,梳理了规划和国土资源管理流程,通过应用示范,进一步探索地质资料信息服务管理制度和技术标准体系完善,努力实现地质资料信息服务多元化。     

Relational networks of knowledge production in transnational law firms

For geographers, debates surrounding the knowledge economy have reinvigorated interest in the geographies of learning and knowledge production. Particularly topical are discussions of the possibility of spatially stretched (global) learning, something especially relevant to professional service firms where the production and management of knowledge across transnational organizational networks is essential. Taking this as its starting point, the paper explores the way knowledge is produced and circulated in transnational legal professional service firms. Drawing on the ideas of relational economic geography to analyse original empirical material, it highlights the way relational networks are socially constructed to allow learning to be stretched across space. The paper then goes on to identify the ‘politics’ of inclusion in these networks and the exclusivity of membership. It also highlights the geographies of power that influence the nature and effect of the knowledge produced and circulated. It does this by examining the role of relational knowledge networks in the ‘Americanization’ of legal practice in Europe and the impacts of such changes on national institutional and regulatory contexts. It is, therefore, argued that transnational corporate networks need to be viewed as heterogeneous and ‘embedded spaces of social practice’. It is shown that studying the actors and their interactions across relational networks is vital to fully understand how global relational forms are constructed and to understand their structuring effects on the global economy.     

Geographic clustering of firms and urban form: a multivariate analysis

This paper provides an empirical framework that applies spatial statistics methods to assess the relation between the change in the geographical clustering of firms and the emergence of urban form. We contend that where firms locate and eventually cluster give rise to the way commercial and industrial land uses are organized over space, which in turn defines the shape of urban form. Accordingly, the objectives of our work are twofold: (1) to identify the extent and shape of firm clustering and co-location at the intra-metropolitan level, and (2) examine how the change in the geographic clustering of different industries contributes to decentralization and the evolution of urban form. Spatial statistics methods and tools were vital and helped to fulfill these objectives.      

中国企业赴新加坡上市格局的演变

企业海外上市的地点选择是金融地理学关注的重要问题。中国有大量的企业在海外上市,其中新加坡是最重要的海外上市地点之一,但是近几年其吸引力有所下降。本文首先分析中国企业在新加坡上市的时间、空间以及行业结构变化历程,在此基础上探讨新加坡成为我国企业海外上市重要目的地以及近期地位下降的原因。凭借与中国在地理、文化和语言等方面的邻近性及产业上的相似性、较为宽松的上市条件、证券交易所积极的市场营销、来自新加坡的风险投资机构的推动以及地方企业集群的模仿领袖效应,新加坡在很长一段时间都是我国企业海外上市的重要目的地之一。2007年以后,新加坡证券交易所对中国企业的吸引力明显下降,主要是由全球金融危机造成资本市场低迷、全球各大交易所间竞争加剧和中国概念股在新加坡金融市场融资不畅等原因造成。结论部分指出,新加坡原有的吸引中国企业前去上市的优势已逐步丧失,企业应理性对待上市。此外,海外上市对全球金融地理格局有深远影响,值得更多国内地理学者进行研究。     

Biogeography and phenology of satellite-measured phytoplankton seasonality in the California current

Thirteen years (1998–2010) of satellite-measured chlorophyll a are used to establish spatial patterns in climatological phytoplankton biomass seasonality across the California Current System (CCS) and its interannual variability. Multivariate clustering based on the shape of the local climatological seasonal cycle divides the study area into four groups: two with spring-summer maxima representing the northern and southern coastal upwelling zones, one with a summer minimum offshore in mid-latitudes and a fourth with very weak seasonality in between. Multivariate clustering on the seasonal cycles from all 13 years produces the same four seasonal cycle types and provides a view of the interannual variability in seasonal biogeography. Over the study period these seasonal cycles generally appear in similar locations as the climatological clusters. However, considerable interannual variability in the geography of the seasonal cycles is evident across the CCS, the most spatially extensive of which are associated with the 1997–1999 El Niño-Southern Oscillation (ENSO) signal and the 2005 delayed spring transition off the Oregon and northern and central California coasts. We quantify linear trends over the study period in the seasonal timing of the two seasonal cycles that represent the biologically productive coastal upwelling zones using four different metrics of phenology. In the northern upwelling region, the date of the spring maximum is delaying (1.34 days yr⁻¹) and the central tendency of the summer elevated chlorophyll period is advancing (0.63 days yr⁻¹). In the southern coastal upwelling region, both the initiation and cessation of the spring maximum are delaying (1.78 days yr⁻¹ and 2.44 days yr⁻¹, respectively) and the peak is increasing in duration over the study period. Connections between observed interannual shifts in phytoplankton seasonality and physical forcing, expressed as either basin-scale climate signals or local forcing, show phytoplankton seasonality in the CCS to be influenced by changes in the seasonality of the wind mixing power offshore, coastal upwelling in the near-shore regions and basin-scale signals such as ENSO across the study area.     

Multi-period calibration of a semi-distributed hydrological model based on hydroclimatic clustering

Changing climatic conditions contribute to a time varying nature of hydrological responses over different temporal scales. The temporal dynamics of hydrological systems bring uncertainties into hydrological simulation which are different to uncertainties from spatial heterogeneity of soil and land use. This study develops a new approach to improve the calibration of hydrological based on hydroclimatic similarities. Six climatic indexes are integrated using Principal Component Analysis and Fuzzy C-mean Clustering methods to transform hydrological years into hydroclimatic periods. Parameter sets of SWAT model are calibrated independently for each period and used together to generate continuous simulation for a prairie watershed in southern Canada. Results indicate that the multi-period model exhibits comprehensive advantages over the traditional single-period model under various flow conditions. The simulation ability of the model is improved through using period-specific parameter sets in fitting the observations to compensate for deficiencies in the model structure or input data.