Prediction of the number of equivalent cycles for earthquake motion

This paper addresses new prediction models for computing the number of equivalent cycles in liquefaction analyses. Three models are presented for the Italian seismicity as a function of synthetic ground motion parameters that are often available from earthquake data web-sites immediately after events. In particular, it is observed that the number of earthquake cycles can be best estimated from the five following parameters: peak ground acceleration; epicentral distance; Arias Intensity; the mean period; and, the frequency of zero crossings. However, strong estimations can be obtained from the first three parameters only. We use statistical indicators to determine the goodness of the models and the usefulness of the selected independent variables, and we present a comparative analysis to validate our predictive equations. Moreover, this paper describes the existing correlation between magnitude and cycle numbers. The study is primarily based on Italian acceleration records, even if the database is also expanded to recorded European, Japanese and American events to amplify the magnitude values range. These simplified models are useful in addressing practical earthquake engineering problems which require the knowledge of number of equivalent cycles.     

RegCM3对全球变暖背景下中国东部季风降水和雨型变化的模拟

The authors investigate possible changes of monsoon rainfall and associated seasonal (June-JulyAugust) anomaly patterns over eastern China in the late 21st century under the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 emission scenario as simulated by a high-resolution regional climate model (RegCM3) nested in a general circulation model (FvGCM/CCM3).Two sets of multi-decadal simulations are performed at 20-km grid spacing for present day and future climate conditions.Results show that the RegCM3 reproduces the mean rainfall distribution;however the evolution of the monsoon rain belt from South China to North China is not well simulated.Concerning the rain pattern classifications,RegCM3 overestimates the occurrence of Pattern 1 (excessive rainfall in northern China) and underestimates that of Pattern 2 (increased rainfall over the Huai River basin).Under future climate conditions,RegCM3 projects less occurrence of Pattern 1,more of Pattern 2,and little change of Pattern 3 (rainfall increase along the Yangtze River).These results indicate that there might be increased rainfall over the Huai-Yellow River area and reduced rainfall over North China in the future,while rainfall over the lower reaches of the Yangtze River basin is not modified significantly.Uncertainties exist in the present study are also discussed.     

CLIMATE CHANGE DUE TO GREENHOUSE EFFECTS IN CHINA AS SIMULATED BY A REGIONAL CLIMATE MODEL—PART Ⅱ:CLIMATE CHANGE*

Impacts of greenhouse effects(2×CO₂) on climate change over China as simulated by a regional climate model have been investigated.The model was based on RegCM2 and is nested in one-way mode within a global coupled atmosphere-ocean model(CSIRO R21L9 AOGCM).Two multi-year simulations,the control run with normal CO₂ concentration and sensitivity run with doubled CO₂ concentration are conducted. As Part II of the publications,with a brief analysis of the 2×CO₂ experiment by CSIRO R21Lg,results of the 2×CO₂ simulation by RegCM2 are analyzed in detail. Results of the RegCM show a remarkably warming over China with an increment ranging from 2.2℃ in southern China to 2.8℃ in northern due to greenhouse effect.The regional averaged annual temperature increase is 2.5℃.The warming is greater in winter and spring.Daily maximum and minimum temperatures increase also over China which lead to much more hot spell days in summer and less cold spell days in winter. Precipitation increases in all seasons of the year,with the greatest found in summer.Annual mean precipitation increases significantly in western China,parts of the area in south of the Yangtze River and northern part of the Northeast.while a decrease in the area from southern part of the Northeast to North China is simulated.The regional averaged annual increase of precipitation is 12%.More heavy rain events are found noticeably in southern China.The simulated tropical storms affecting and landing over China tend to increase.Analysis on the simulation of circulation pattern showed that the 500 hPa height in East Asia might rise significantly.     

引发意大利托斯卡纳区滑坡的区域降水阈值体系的定义——统计与环境分析(英文)

The aim of this work is the determination of regional-scale rainfall thresholds for the triggering of landslides in the Tuscany Region(Italy).The critical rainfall events related to the occurrence of 593 past landslides were characterized in terms of duration(D) and intensity(I).I and D values were plotted in a log-log diagram and a lower boundary was clearly noticeable:it was interpreted as a threshold representing the rainfall conditions associated to landsliding.That was also confirmed by a comparison with many literature thresholds,but at the same time it was clear that a similar threshold would be affected by a too large approximation to be effectively used for a regional warning system.Therefore,further analyses were performed differentiating the events on the basis of seasonality,magnitude,location,land use and lithology.None of these criteria led to discriminate among all the events different groups to be characterized by a specific and more effective threshold.This outcome could be interpreted as the demonstration that at regional scale the best results are obtained by the simplest ap-proach,in our case an empirical black box model which accounts only for two rainfall pa-rameters(I and D).So a set of thresholds could be conveniently defined using a statistical approach:four thresholds corresponding to four severity levels were defined by means of the prediction interval technique and we developed a prototype warning system based on rainfall recordings or weather forecasts.     

Spatial Statistical Properties of Pressure Solution Seams in Clastic Rocks in Southwest Ireland

Length, height, thickness and spacing measurements of pressure solution seams at outcrop, hand sample and thin section scale were taken from clastic rocks located in the southwest of Ireland. The lengths and spacings of pressure solution seams have similarly shaped (approximately log-hyperbolic) distributions at the observed scales suggesting that length and spacing distributions are scale-independent over the scales studied with a fractal dimension in the range of 1.4 to 1.6. Pressure solution seam lengths and thicknesses are related by a power-law and their spacings have a linear relationship to bed thickness. Although pressure solution seams are often considered as anticracks (forming under the same remote stresses as joints, but with opposite sign) we describe how the mechanism of pressure solution differs substantially from that of jointing. We use an existing mechanical model to show that stresses around pressure solution seam tips are much lower than those for joints under equal but opposite loading conditions. Pressure solution seams also have a decreasing tendency to lengthen as they grow, which is reflected in their length distributions. We propose that pressure solution seams, unlike joints, do not reach fracture saturation spacing because of transverse coalescence.     

温室效应引起的中国区域气候变化的数值模拟Ⅰ:模式对中国气候模拟能力的检验

使用RegCM2区域气候模式单向嵌套澳大利亚CSIRO R21L9全球海-气耦合模式,进行了CO2加倍对中国区域气候变化影响的数值试验研究,分析了控制试验(1×CO2)即模式对中国当代气候的模拟情况.首先给出了全球模式控制试验在中国地区的结果,分析表明它对中国区域的地面气温和降水具有一定的模拟能力,其结果可以用来制作驱动区域气候模式的初始场和侧边界.对RegCM2 5 a时间长度控制试验积分结果的分析与检验表明,区域气候模式由于具有较高的分辨率和较完善的物理过程,它对中国区域地面气温和降水的模拟效果较全球模式有了较大提高,如它模拟的各月气温与实况的相关系数全年12个月的平均由全球模式的0.83提高到0.92,降水由0.48提高到0.65.