Aftershock Statistics

The statistical properties of aftershock sequences are associated with three empirical scaling relations: (1) Gutenberg-Richter frequency-magnitude scaling, (2) Båths law for the magnitude of the largest aftershock, and (3) the modified Omoris law for the temporal decay of aftershocks. In this paper these three laws are combined to give a relation for the aftershock decay rate that depends on only a few parameters. This result is used to study the temporal properties of aftershock sequences of several large California earthquakes. A review of different mechanisms and models of aftershocks are also given. The scale invariance of the process of stress transfer caused by a main shock and the heterogeneous medium in which aftershocks occur are responsible for the occurrence of scaling laws. We suggest that the observed partitioning of energy could play a crucial role in explaining the physical origin of Båths law. We also study the stress relaxation process in a simple model of damage mechanics and find that the rate of energy release in this model is identical to the rate of aftershock occurrence described by the modified Omoris law.     

Melt inclusion analysis of the Unzen 1991–1995 dacite: implications for crystallization processes of dacite magma

Dacitic magma, a mixture of high-temperature (T) aphyric magma and low-T crystal-rich magma, was erupted during the 1991–1995 Mount Unzen eruptive cycle. Here, the crystallization processes of the low-T magma were examined on the basis of melt inclusion analysis and phase relationships. Variation in water content of the melt inclusions (5.1–7.2 wt% H₂O) reflected the degassing history of the low-T magma ascending from deeper levels (250 MPa) to a shallow magma chamber (140 MPa). The ascent rate of the low-T magma decreased markedly towards the emplacement level as crystal content increased. Cooling of magma as well as degassing-induced undercooling drove crystallization. With the decreasing ascent rate, degassing-induced undercooling decreased in importance, and cooling became more instrumental in crystallization, causing local and rapid crystallization along the margin of the magma body. Some crystals contain scores of melt inclusions, whereas there are some crystals without any inclusions. This heterogeneous distribution suggests the variation in the crystallization rate within the magma body; it also suggests that cooling was dominant cause for melt entrapment. Numerical calculations of the cooling magma body suggest that cooling caused rapid crystal growth and enhanced melt entrapment once the magma became a crystal-rich mush with evolved interstitial melt. The rhyolitic composition of melt inclusions is consistent with this model.Editorial responsibility: H Shinohara     

Bayesian Discovery Process Modeling of the Lower and Middle Jurassic Play of the Halten Terrace,Offshore Norway,as Compared with the Previous Modeling

A Bayesian version of the discovery process model was applied to the pre-rift Lower and Middle Jurassic play of the Halten Terrace, Mid-Norway. The Bayesian approach estimates the lognormal parameters, the discoverability parameter, and the distribution of sizes of the undiscovered fields as well as the play potential, conditioned on a discovery sequence averaging for all possible prior choices weighted by their likelihood. This approach avoids the problem of having to make arbitrary choices for the parameters. The estimates of parameters and play potential based upon the present methodology compares well with previous estimates, if the play is divided into two sub-plays representing the overpressured and normally pressured zones. These sub-plays have been estimated independently and aggregated in order to get the total undiscovered resource potential. This study estimates that the expected remaining play potential is 100 × 10⁶Sm³ o.e., about 9% of the total resources in the play. There is however a 90% chance that the remaining potential ranges from 13 to 282× 10⁶ Sm³ o.e. and a 5% possibility of exceeding this value.     

The aeolian sedimentation record of the Thar desert

A review of the aeolian sedimentary record of the Thar desert is presented. This includes a regional survey of the major dune forms, their genesis and their relationship to climate and other regional landforms. A key aspect of this work is the chronometry of the dunes using luminescence methods. Luminescence dating of sand has enabled quantification of the duration of the phases of sand aggradation and quiescence, time scales of dune migration and the dating of pedogenic carbonates. We demonstrate that the conventional wisdom of synchronicity of dune aggradation with glacial epoch is not true in the context of Thar sands and here only a short durationwindow of opportunity existed for dune aggradation. Luminescence ages further suggest that this window occurred during a transitional climatic regime from glacial to interglacial about 4–10 ka after the glacial epoch. Other inferences included are that:

城市3维模型构建方法研究与实现

3维模型的构建是城市3维地理信息系统建设的核心。介绍了基于现有数据资料制作城市3维模型的工艺流程,重点研究了利用城市大比例尺3维DLG数据批量获取建筑物高度的新方法和贴图制作过程。按照上述制作工艺和方法较好地解决了大面积城市3维建模这一问题,生成的模型具有很高的精度,完全满足城市3维建模的精度要求。     

探讨3维地物模型制作过程

自第一台计算机诞生以来,计算机技术迅速发展,并在各行各业中得到广泛应用。3维显示技术是随着计算机软硬件的快速发展而兴起的一个新的应用方向。它能在计算机中为用户提供一个3维的直观环境,通过视觉提高真实感。随着地理信息产业的快速发展,人们对3维地理空间支撑的需求越来越强烈,"数字城市"项目在各大城市如火如荼的发展,3维GIS进入了高速发展和广泛应用的新时期。这里探讨了综合运用3dsMax,Arc Map,creator,CAD,PhotoShop等软件制作3维地物模型的过程。     

测绘产品监督检验视角下城市测绘工程质量控制技术探讨

以测绘产品监督检验的视角,将城市测绘工程质量管理与质量控制思路为研究对象,探讨了质量管理的内涵及质量的系统化控制管理方法。全文以质量检查点为线索,探讨了整个流程中的数据检查方法。     

偏硼酸锂溶液物种分布和物化性质

测量了不同浓度LiBO2溶液分别在298.15和323.15 K的密度、电导和pH,通过测得的pH和硼酸根离子化学平衡常数计算得到溶液中硼酸根离子的物种分布。根据获得的物种分布结果,推测溶液中各硼酸根离子之间的相互转化过程,并分别用偏摩尔体积公式和Onsager方程对溶液偏摩尔体积及摩尔电导率进行计算并拟合。对计算得到偏摩尔体积值和极限摩尔电导率值与文献报道的数据进行对比,计算结果与文献报道值吻合较好。     

黄河三角洲湿地柽柳林生长动态密度结构的响应特征

为了阐明滨海湿地不同密度柽柳(Tamarix chinensis)林的生长动态,探索滨海湿地柽柳林的密度合理性,在黄河三角洲莱州湾南岸的山东昌邑海洋生态特别保护区内,利用标准木树干解析法,对10a生的3种密度(2400株/hm2、3 600株/hm2和4400株/hm2)的柽柳林地上生物量、林木生长动态和基径分布特征进行研究.结果表明,3种密度林分的地上生物量、树高生长量和林木基径生长过程差别较大.随着林分密度增大,林木单株生物量和基径减小,但单位面积林分生物量增加;树高、基径的速生期都出现滞后现象.3种密度林分基径分布的偏度系数(SK)差别较大;密度为3 600株/hm2林分的SK值为0.085,接近正态分布,林分密度结构和基径分布较为合理;密度为2 400株/hm2和4 400株/hm2林分的SK值分别为-0.842和0.303,偏离正态分布,林分密度结构不合理.密度为2 400株/hm2林分的峰度系数(K)为0.017,林木生长相对整齐;密度为3 600株/hm2和4 400株/hm2林分的K值相差不大;密度因素对林木分化作用较小.若不考虑10a间的林木间伐利用,该区柽柳人工造林合理的初植密度建议为3 600株/hm2(株行距约2.0 m×2.0 m).