Event pattern analysis: Spatial clustering of sequential events and temporal change of events over time     

Yukio Sadahiro 《Transactions in GIS》2023,27(1):260-274

This article develops a method for analyzing spatial and temporal event patterns. Events in this article refer to zero-dimensional objects in the spatiotemporal dimension, which represent the occurrence of crimes, traffic accidents, earthquakes, and so forth. The spatial clustering of sequential events and the increase and decrease in events over time are discussed. These patterns are often observed and analyzed in various academic fields, such as criminology, epidemiology, and geography. However, analytical methods for these patterns have not yet been fully developed. To fill the research gap, this article proposes a new method for analyzing these event patterns. Two statistical measures are utilized, one represents the degree of the spatial clustering of sequential events, and the other evaluates the increase and decrease of events over time. The method is applied to the analysis of the spatial and temporal patterns of the openings of new shops and restaurants in Shibuya-ku, Tokyo. The results gave us interesting empirical findings and indicated the soundness of the method.  相似文献   

饱和珊瑚砂液化特性动三轴试验研究          下载免费PDF全文

郭舒洋  崔杰  吴杨  单毅  中田幸男  梶山慎太郎 《地震工程学报》2024,(1):84-94

为调查饱和珊瑚砂液化相关特性与发展规律,针对饱和Chibishi珊瑚砂,开展一系列不排水循环三轴试验,研究相对密度D_r和循环应力比CSR对饱和Chibishi珊瑚砂的超孔隙水压力Δu、轴向应变ε_a及动强度特性的影响,并分析不同地区珊瑚砂抗液化强度的差异性。结果表明,饱和Chibishi珊瑚砂的Δu发展模式根据不同的CSR水平可以分为前期均匀增长型、前期突增型和后期突增型;此外,采用一种新的孔压模型对前期均匀增长型、前期突增型的孔压比r_u进行表征,Chibishi珊瑚砂在相同的D_r条件下,双幅应变ε_DA达到5%的循环次数N随着CSR水平的增加而逐渐减小;各珊瑚砂在同一里氏震级对应的等效循环振动次数下,抗液化强度CRR的增长模式存在显著差异。研究结果可丰富对珊瑚砂液化特征的认知,同时对近岸和沿海工程的抗震设计提供参考依据。  相似文献   

A visage of early Paleozoic Japan: Geotectonic and paleobiogeographical significance of Greater South China     

Yukio Isozaki 《Island Arc》2019,28(3)

The current state of knowledge on the early Paleozoic evolution of Japan is reviewed. Although early Paleozoic Japan marked the foundation of long‐lasting subduction‐related orogenic growth throughout the Phanerozoic, details of this have not been fully revealed. Nevertheless, U‐Pb dating of zircons both in Paleozoic granitoids and sandstones is revealing several new aspects of early Paleozoic Japan. The timing of the major tectonic change, from a passive continental margin setting (Stage I) to an active one (Stage II), was constrained to the Cambrian by identifying the oldest arc granitoid, high‐P/T blueschist, and terrigenous clastics of arc‐related basins. Ages of recycled zircons in granitoids and sandstones provided critical information on the homeland of Japan, i.e. the continental margin along which proto‐Japan began to grow. The early Paleozoic continental margin that hosted the development of an arc‐trench system in proto‐Japan had cratonic basement composed mostly of Proterozoic crust with a minor Archean component. The predominant occurrence of Neoproterozoic zircons in Paleozoic rocks, as xenocrysts in arc granitoids and also as detrital grains in terrigenous clastics, indicates that the relevant continental block was a part of South China, probably forming a northeastern segment of Greater South China (GSC) together with the Khanka/Jiamsi/Bureya mega‐block in Far East Asia. GSC was probably twice as large as the present conterminous South China on mainland Asia. Paleozoic Japan formed a segment of a mature arc‐trench system along the Pacific side of GSC, where the N–S‐trending Pacific‐rim orogenic belt (Nipponides) developed with an almost perpendicular relationship with the E–W‐trending Central Asian orogenic belt. The faunal characteristics of the Permian marine fauna in Japan, both with the Tethyan and Boreal elements, can be better explained than before in good accordance with the relative position of GSC with respect to the North China block during the late Paleozoic.  相似文献