1961-2010年中国400mm和800mm等雨量线时空变化

以中国1961-2010年逐日降水数据为基础,利用等值线加权平均位置的方式对400 mm和800 mm等雨量线的空间位置进行定量化处理。采用Kendall 秩次相关检验法、Morlet小波分析法、滑动t-检验法和Yamamoto法时间序列分析方法,对全国50年来 400 mm和800 mm等雨量线的空间位移特征进行了系统揭示:1961-2010年期间,400 mm和800 mm等雨量线加权平均位置坐标分别为（106°07'12"E,39°25'13"N）和（110°16'31"E,34°12'04"N）。趋势性结果表明,全国400 mm和800 mm等雨量线有向西和向南发生移动的趋势,其中400 mm等雨量线向西移动明显,800 mm等雨量线向南移动明显;周期性结果表明,全国400 mm等雨量线在经向和纬向上发生迁移的主周期分别为9年和 12年,800 mm等雨量线在经向和纬向变化均存在7年的主周期;突变性结果表明,400 mm等雨量线空间位置的突变年为1995-1996年（纬度）,800 mm等雨量线空间位置的突变年为1975年、2002年（经度）和1980年、1982年和1987年（纬度）。     

2013年南斯科舍海岭MW7.8地震的多点震源机制反演

2013年11月17日,在南极南奥克尼群岛北、南极板块与斯科舍板块之间发生了一次M_W7.8级地震(2013年南斯科舍海岭M_W7.8地震),我们利用全球分布的长周期和宽频带地震记录反演确定了这次地震随时间和空间变化的震源机制,验证了提出的一种多点震源机制反演的新方法.首先利用长周期记录的W震相反演了这次地震的矩心矩张量解并利用体波提取了视震源时间函数,同时利用台阵反投影技术从宽频带记录中获得了这次地震的高频源的时空分布,然后基于矩心矩张量解、视震源时间函数以及高频源的时空分布,实现了采用新方法对2013年南斯科舍海岭M_W7.8地震的多点震源机制反演.矩心矩张量解表明,地震矩心在44.50°W/60.18°S,矩心深度19 km,半持续时间49 s,释放标量地震矩4.71×10²⁰ N·m,发震断层走向104°,倾角54°,滑动角8°.视震源时间函数清楚地揭示了地震矩随时间变化的方位依赖性,总体上可以将时间过程分为前60 s和后50 s两个阶段,但前60 s可细分为两次子事件.根据台阵反投影结果,这次地震为沿海沟从西到东的单侧破裂,破裂长度达311 km,可以分为5次子事件,能量释放的峰值点依次为13 s、30 s、51 s、64 s和84 s,平均破裂速度分别为0.6 km·s^-1、2.6 km·s^-1、2.3 km·s^-1、2.8 km·s^-1和3 km·s^-1.多点震源机制反演显示,5次子事件的矩震级分别为M_W7.57,M_W7.48,M_W6.80,M_W7.53和M_W7.08,半持续时间依次为21 s,17 s,6 s,16 s和8 s,走向分别为95°,105°,81°,98°和98°,倾角依次为57°,49°,86°,46°和64°,滑动角-9°,1°,-17°,13°和-4°.这些在震源机制、能量释放以及持续时间方面的变化都是当地构造和应力环境复杂性的反映.

     

GLONASS/BDS单历元单频RTK定位研究

天空中导航卫星的可见数不断增加对整周模糊度的解算带来了有利的影响,极大改善了GNSS单历元单频RTK定位的精度和可靠性。针对GLONASS/BDS组合定位时的时空基准统一问题进行了分析;并针对GLONASS信号频分多址的特点,对GLONASS/BDS单历元单频RTK定位的数学模型进行了研究;最后通过实测数据对模型可行性进行了验证。结果表明,GLONASS/BDS单历元单频RTK定位是可行的,并且在北向上的定位精度要优于BDS单历元双频RTK定位。     

Estimation of transit trip production using Factorial Kriging with External Drift: an aggregated data case study

Studies in transportation planning routinely use data in which location attributes are an important source of information. Thus, using spatial attributes in urban travel forecasting models seems reasonable. The main objective of this paper is to estimate transit trip production using Factorial Kriging with External Drift (FKED) through an aggregated data case study of Traffic Analysis Zones in São Paulo city, Brazil. The method consists of a sequential application of Principal Components Analysis (PCA) and Kriging with External Drift (KED). The traditional Linear Regression (LR) model was adopted with the aim of validating the proposed method. The results show that PCA summarizes and combines 23 socioeconomic variables using 4 components. The first component is introduced in KED, as secondary information, to estimate transit trip production by public transport in geographic coordinates where there is no prior knowledge of the values. Cross-validation for the FKED model presented high values of the correlation coefficient between estimated and observed values. Moreover, low error values were observed. The accuracy of the LR model was similar to FKED. However, the proposed method is able to map the transit trip production in several geographical coordinates of non-sampled values.     

河流形态的分维及与洪水关系的探讨--以长江中下游为例

河流水系形态特征可以通过河流的分形特征来反映,分形维数则是河流分形特征的量化表示,其与河流洪水之间存在着一定的关系。以长江中下游为例,利用网格覆盖法计算出长江中下游河流分维,分析了长江中下游河流的分形特性,并在此基础上结合长江中下游洪水分析不同水系特征下洪水的特点。研究结果表明,一般来说河道分维越大、河网分维越小,洪水发生可能性则越高。     

试论未来极端气候事件发展趋势的不确定性

极端气候事件是在一定时间尺度上发生的不同于气候系统平均状态的气候突变.早第三纪的最热事件（PETM）,第四纪中国黄土高原古土壤S4、S5记录的暖湿事件,砂黄土L9、L15记录的干冷事件等都是在轨道时间尺度上发生的极端气候事件.末次冰消期的YD冷事件、全新世9次冷事件是在千—百年尺度上发生的极端气候事件.这些极端气候事件出现于地球气候系统不同的冷暖背景下,它们的成因机制和表现形式有很多不确定性.20世纪以来发生的干旱、洪水、飓风、雪灾、沙尘暴等极端气候事件,无法用持续增加的温室气体的变化来解释.关于极端气候事件发生频率和强度随＂全球变暖＂而增加的结论也存在一定程度的不确定性.因此,简单地将现代极端气候事件统统归因于＂气候变暖＂既不科学也不合理.深入研究各个时间尺度上发生的极端气候事件的波动性、周期性和不确定性特征,有助于科学预测未来气候变化背景下极端气候事件的发展趋势.     

Task-oriented information value measurement based on space-time prisms

Recent years have witnessed a large increase in the amount of information available from the Web and many other sources. Such an information deluge presents a challenge for individuals who have to identify useful information items to complete particular tasks in hand. Information value theory (IVT) from economics and artificial intelligence has provided some guidance on this issue. However, existing IVT studies often focus on monetary values, while ignoring the spatiotemporal properties which can play important roles in everyday tasks. In this paper, we propose a theoretical framework for task-oriented information value measurement. This framework integrates IVT with the space-time prism from time geography and measures the value of information based on its impact on an individual’s space-time prisms and its capability of improving task planning. We develop and formalize this framework by extending the utility function from space-time accessibility studies and elaborate it using a simplified example from time geography. We conduct a simulation on a real-world transportation network using the proposed framework. Our research could be applied to improving information display on small-screen mobile devices (e.g., smartwatches) by assigning priorities to different information items.     

Residence, Resorption and Recycling of Zircons in Devils Kitchen Rhyolite, Coso Volcanic Field, California

Zircons from the Devils Kitchen rhyolite in the PleistoceneCoso Volcanic field, California have been analyzed by in situPb/U ion microprobe (SHRIMP-RG) and by detailed cathodoluminescenceimaging. The zircons yield common-Pb-corrected and disequilibrium-corrected²⁰⁶Pb/²³⁸U ages that predate a previously reported K–Arsanidine age by up to 200 kyr, and the range of ages exhibitedby the zircons is also approximately 200 kyr. Cathodoluminescenceimaging indicates that zircons formed in contrasting environments.Most zircons are euhedral, and a majority of the zircons areweakly zoned, but many also have anhedral, embayed cores, witheuhedral overgrowths and multiple internal surfaces that aretruncated by later crystal zones. Concentrations of U and Thvary by two orders of magnitude within the zircon population,and by 10–20 times between zones within some zircon crystals,indicating that zircons were transferred between contrastingchemical environments. A zircon saturation temperature of 750°Coverlaps within error a previously reported phenocryst equilibrationtemperature of 740 ± 25°C. Textures in zircons indicativeof repeated dissolution and subsequent regrowth are probablycaused by punctuated heating by mafic magma input into rhyolite.The overall span of ages and large variation in U and Th concentrations,combined with calculated zircon saturation temperatures andresorption times, are most compatible with crystallization inmagma bodies that were emplaced piecemeal in the crust at Cosoover 200 kyr prior to eruption, and that were periodically rejuvenatedor melted by subsequent basaltic injections. KEY WORDS: zircon geochronology; residence time; rhyolite; ion microprobe; California     

分形理论用于洪水分期的初步探讨

用分形理论对洪峰散点序列进行了分析,发现洪峰散点序列在一定尺度范围内表现出了自相似性,初步证明洪峰散点序列是一种分形。提出了用分形理论划分洪水分期的方法,并以雅垄江小得石站洪水分期研究为例。结果显示,用分形法划分的洪水分期和传统的经验方法划分的洪水分期基本一致,但和传统方法相比,新方法的优点较为客观。     

Site effects at Euroseistest—I. Determination of the valley structure and confrontation of observations with 1D analysis

This paper describes the process of construction of the 2D model of Volvi's geological structure and results of empirical and theoretical approaches to the evaluation of site response at Euroseistest. The construction of the 2D model is based on a re-interpretation of the available geophysical and geotechnical data in an effort to improve the definition of the subsoil structure at Euroseistest in terms of the most important parameters needed to model site response. The results of this re-interpretation are compared with a previous published 2D model of the same alluvial valley. Different analysis of the measurements and different criteria in the synthesis of data have led to a different model, even if both studies had access to the same field measurements. This underscores the fact that a model results of an interpretation and is not uniquely determined by the data, no matter how detailed they are. The well known subsoil structure opened the possibility to correlate the geometry and the dynamic properties of the 2D model with the results of site response determined from a detailed analysis of two events in frequency and time domains and 1D numerical modeling. The study of site response shows the important effect of the lateral variations on the ground motion and suggests that the contribution of locally generated surface waves to the resonant peak may be important. In the case of Volvi's graben, the limitations of the 1D approximation to simulate ground motion under complex soil conditions in both frequency and time domains are also shown. This paper lays the ground for a companion article dealing with 2D site effects in this basin.