Influential input classification in probabilistic multimedia models

 Monte Carlo analysis is a statistical simulation method that is often used to assess and quantify the outcome variance in complex environmental fate and effects models. Total outcome variance of these models is a function of (1) the variance (uncertainty and/or variability) associated with each model input and (2) the sensitivity of the model outcome to changes in the inputs. To propagate variance through a model using Monte Carlo techniques, each variable must be assigned a probability distribution. The validity of these distributions directly influences the accuracy and reliability of the model outcome. To efficiently allocate resources for constructing distributions one should first identify the most influential set of variables in the model. Although existing sensitivity and uncertainty analysis methods can provide a relative ranking of the importance of model inputs, they fail to identify the minimum set of stochastic inputs necessary to sufficiently characterize the outcome variance. In this paper, we describe and demonstrate a novel sensitivity/uncertainty analysis method for assessing the importance of each variable in a multimedia environmental fate model. Our analyses show that for a given scenario, a relatively small number of input variables influence the central tendency of the model and an even smaller set determines the spread of the outcome distribution. For each input, the level of influence depends on the scenario under consideration. This information is useful for developing site specific models and improving our understanding of the processes that have the greatest influence on the variance in outcomes from multimedia models.     

Collision tectonics in the New Hebrides arc (Vanuatu)

Abstract The New Hebrides island arc in Vanuatu has been significantly modified by collision with several major submarine ridges and plateaux. Bathymetric sections taken at intervals along the arc, perpendicular to the trench, show that prior to collision at 3 Ma the morphology was typical of modern intraoceanic island arcs. Collision has caused uplift of the trench and forearc (up to 6000 m), subsidence around the arc volcanic edifices (up to 2500 m), forming a large intra-arc basin and uplift of the arc-backarc transition (up to 2000 m). In the transition zone between collisional and non-collisional sections of the arc, subsidence occurs in the forearc and uplift occurs around the arc volcanoes. Many of these characteristics are typical of collisions in other Western Pacific island arcs such as the Tonga–Kermadec and Izu–Bonin arcs. The pattern of uplift and subsidence has important implications for the tectonic history of the New Hebrides system. The morphology of the arc shows that collision of the West Torres Massif probably accounts for at least half the uplift. Arrival at 0.7 Ma of the West Torres Massif in the trench may have caused the slowing of subduction in the entire northern half of the arc and not just in the central segment as previously suggested. Re-equilibration of the arc following collision probably masks any evidence of collision prior to 3 Ma. For example, the Efate re-entrant, a large indentation in the arc immediately to the south of the collision zone, probably originated as a result of erosion during collision followed by subsidence after collision. The Vanuatu collision shows that the subduction of seamounts and ridges in an intraoceanic arc temporarily changes the arc morphology, allowing the development of angular unconformities and changing the pattern of sedimentation. This provides information which can be used to facilitate recognition of these events in ancient arc-related sequences.     

Wave propagation in a seven-story reinforced concrete building: II. Observed wavenumbers

This paper presents estimates of wavenumbers of propagating waves in a seven-story reinforced concrete building in Van Nuys, California, using recorded response to four earthquakes. The phase velocities inferred from these wavenumbers are consistent from one earthquake to another. They are also consistent, inside the building, with independent estimates of the shear wave velocities in the building (e.g. using ambient vibration tests), and along the base, with phase velocities of Love waves typical for San Fernando Valley.     

Local site effects and dynamic soil behavior

Amplitudes of seismic waves increase significantly as they pass through soft soil layers near the earth's surface. This phenomenon, commonly known as site amplification, is a major factor influencing the extent of damage on structures. It is crucial that site amplification is accounted for when designing structures on soft soils. The characteristics of site amplification at a given site can be estimated by analytical models, as well as field tests. Analytical models require as inputs the geometry of all soil layers from surface to bedrock, their dynamic properties (e.g. density, wave velocity, damping), and the incident bedrock motions. Field tests involve recording and analyzing the dynamic response of sites to artificial excitations, ambient forces, and actual earthquakes. The most reliable estimates of site amplification are obtained by analyzing the recorded motions of the site during strong earthquakes. This paper presents a review of the types and the generating mechanisms of site amplification, and the models and methods that are used to characterize them from earthquake records.     

细胞自动机在地震波传播研究中的应用

本文基于细胞自动机在地震波传播研究中的最近成果，阐述了其基本的研究思路与理论框架，给出了一个计算实例．在此基础上就细胞自动机方法与传统波动方程的衔接关系及复杂介质中地震波正反问题作了讨论，并对研究前景进行展望．     

反转构造与造山带研究

反转构造的研究已成为造山带构造研究的一个重要内容。反转构造模拟和实践所得出的断层组合形态和形成顺序有助于对造山带及前陆褶皱和逆冲带的正确认识。由于张性断层的控制作用，６０年代中期发展起来的薄壳构造模式在现实中并不普遍适用，构造剖面的平衡恢复因此亦需加倍谨慎。在造山带研究中，还需注意反转构造与走滑构造之间的区分。     

中国含煤盆地的聚煤规律

含煤盆地是煤系形成的基本地质构造单元，含煤盆地的形成和演化与所处的板块构造位置有关，板块构造在中国含煤盆地的演化中具有重要的作用，因为它影响着含煤盆地的古地理，古气候及古植物的变化，因此板块构造演化控制了含煤盆地的煤系的形成和分布。     

太古代脉状金矿研究的某些新进展

主要介绍了近几年来关于太古代脉状金矿的产出环境、成矿物理化学条件等方面研究取得的一些新进展，加会聚构造成矿和地壳连续成矿模式的提出等；初步讨论了我国在太古代高级变质区寻找高温脉状金矿时应注意的问题。     

应用卫星热红外异常预测地震的研究

构造型地震是现代断层突发性错动产物。在强震孕育与破裂过程中，不仅释放巨大应变能量，而且在断导对段伴随着热效应，并引起岩石和土壤中水产生汽化与低空气体电离作用，从而诱发各种波段的地光现象（包括热红外光谱异常）。在中强地震前，随着断层放与低空气体电离作用增强，将导致热红异常更加明显。