东平台分量应变与体应变可靠性分析及特殊事件影响对比

本文通过四分量自检、相对标定内精度分析对东平地震台YRY-4钻孔分量应变观测资料进行可靠性分析,并结合滑动相关性计算、潮汐因子内精度对2套仪器数据进行了对比,证明YRY-4钻孔分量应变2面应变相关性高,相关系数接近1,相对标定内精度高,与体应变数据整体趋势一致。2套仪器观测环境一致,运行稳定,数据正常可靠,但也存在降雨、场地干扰特殊时段曲线表现不一致的情况。针对2种特殊情况结合相关性计算、S变换进行了对比分析。结果表明,降雨时段,因钻孔条件差别较大,2套仪器数据相关性较差,接近0;场地干扰时段,2套仪器观测系统均受到影响,频率域同步出现干扰信号,影响数据曲线形态及潮汐因子精度,但2套仪器面应变相关性达0.91。综合分析,东平台钻孔应变仪与体应变2套仪器观测系统是可靠稳定的。      

江宁地震台YRY-4型四分量钻孔应变仪可靠性检验

江宁地震台YRY-4型四分量钻孔应变仪于2006年12月安装运行,多年来积累了大量应变观测数据。采用Venedikov调和及相对标定等方法,从观测数据年变幅度、连续率及稳定性等方面,检验该台钻孔应变可靠性,结果表明,2009年以来,江宁地震台分量钻孔应变观测变仪器运行稳定、可靠,观测资料连续,符合地壳形变观测技术规范要求。     

YRY-4型钻孔应变仪观测的P波剪应变

传统地震仪观测的是一个点的位移随时间的变化, 而应变仪观测的是位移的空间导数随时间的变化。 在四川姑咱台用YRY-4型四分量钻孔应变仪进行的每秒100次采样观测实验, 记录到三次地方震。 在这样高的采样率下, YRY-4型四分量应变仪观测数据保持了令人满意的自洽和足够高的信度。 观测表明, P波的应变不仅有面应变成分, 而且有剪应变成分。 这为澄清P波的性质, 给出了直接的观测证据。 根据弹性波理论, P波无旋转, 可以有体应变和剪应变成分。     

徐州地震台2016年11月—2017年YRY-4分量钻孔应变仪异常核实

2016年11月-2017年,徐州地震台YRY-4分量钻孔应变曲线出现"漏斗"状向下凹陷的压性变化,从场地环境、观测环境、观测系统进行现场核实,并对异常期间的观测数据进行对比分析,排除外界干扰及仪器自身问题,认为此次数据畸变可能反映了地下应力的真实变化,应为地下地质构造发生变化所致。     

山西忻州地区YRY-4分量钻孔应变仪典型干扰因素分析

YRY-4分量钻孔应变仪具有高分辨力特点,在实际运行过程中能够记录到多种类型的外界干扰,表现为观测曲线突变或趋势异常。选取山西忻州地区5套四分量钻孔应变仪自运行以来的观测资料,基于各类干扰因素特征进行分析,结果表明：在日常运行中,影响钻孔应变观测的典型干扰因素主要有观测系统、自然环境、场地环境、人为干扰等;观测系统运行稳定,映震效能良好。     

泸州台钻孔应变观测的环境干扰分析

通过对泸州台YRY-4型分量式钻孔应变仪观测资料分析,总结了典型的环境干扰特征,得到了附近长江和沱江水位干扰、雷电降雨干扰、水井抽水活动干扰、城建施工干扰等在应变观测记录曲线上的对应变化。初步弄清了台站附近长江和沱江水位干扰、雷电降雨干扰、水井抽水活动干扰、城建施工干扰等是数据发生变化的主要原因,在应变观测记录曲线上存在对应变化关系。     

青海钻孔应变强震前异常特征分析

选取2007年以来青海省6套YRY-4分量钻孔应变仪观测资料,采用非潮汐和潮汐分析方法,对观测资料进行分析处理。结果发现:1格尔木地震台钻孔应变差应变曲线显示中短期速率异常,而德令哈地震台则显示超2倍标准差异常;2乐都地震台钻孔应变振幅因子显示突跳型异常,且异常时间短,而潮汐因子表现为下降—恢复型异常。     

青海地区钻孔应变观测及资料分析

介绍了青海地区"十五"期间架设的6个YRY-4型分量钻孔应变仪台站和仪器基本情况,对产出的数字化钻孔应变观测资料的动态特征进行了分析,总结出了同震变化的记录特征;探讨了地震时应力应变运动与构造断层间的微弱错动现象.     

易县地震台分量钻孔应变观测数据分析

选取易县地震台YRY-4型分量式钻孔应变仪2012—2020年观测数据,进行Venedikov调和分析,并对2015—2020年四分量数据S₁、S₂、S₃、S₄进行自洽检验,发现应变观测数据连续性、可靠性较高。选取该台2018—2019年钻孔应变原始数据S₁、S₂、S₃、S₄,利用面应变S₁ + S₃、S₂ + S₄相关系数,分析河北省3次M_L≥4.0地震前数据异常变化,并利用剪应变S₁ - S₃、S₂ - S₄的大小,分析受抽水干扰的NE分量主应力方位角,判断干扰源方位,结果发现：①面应变与剪应变在地震发生前均会出现异常变化,且剪应变异常变化幅度较大,应与震中相对于观测井的位置有关;②对于受抽水干扰的钻孔应变NE分量,利用剪应变固体潮数据推算主应力方位角,可得干扰源在钻孔应变观测室NW80.96°方位,与实际位置存在一定偏差。     

基于分量钻孔应变资料分析测区构造应变变

根据“双衬套”理论模型和应变理论, 以易县台分量钻孔应变观测资料为例解算测区构造应变变化。 由于易县台分量钻孔应变元件灵敏度不一致, 首先进行相对实地标定, 数据信度由0.7557升高到0.9344; 其次, 应用理论固体潮对易县台分量钻孔应变进行绝对标定, 得到耦合系数; 最后, 通过应变换算得到易县台观测点附近的应变参数, 面应变ε_a每年以2440 ns的速度变化, 最大剪应变ε_s以每年230 ns的速度变化, 应变主方向为138°。 综合结果表明, 易县台测区附近的构造应变呈稳定拉伸的状态。     

Using diatoms to assess geographical patterns of change in high-altitude European lakes from pre-industrial times to the present day

No Abstract. .This is the corrected version of the Acknowledgments and some references of the above mentioned article that appeared electronically Online First on April 1, 2005 (this issue, pp. 224–236).     

Rate of floodplain reworking in response to increasing storm‐induced floods,Squamish River,south‐western British Columbia,Canada

Relations among hydroclimatic and channel planform changes on Squamish River are presented for the period 1956–2007. Squamish River basin occupies 3600 km² of mountainous terrain in south‐western British Columbia, about 50 km north of Vancouver. The magnitude, volume and duration of extreme floods (Q ≥ 1500 m³/s) exhibit respective temporal increases of 50, 450 and 300%. The increase in extreme floods is attributed to the intensification of late‐season (August–December) Pacific storms that have produced increases in precipitation amounts, intensity and duration of respectively 340, 200 and 200% over the same period. Changes in floodplain‐surface area calculated from the geographic information system (GIS) differencing of sequential large‐scale aerial photographs indicate that the rate of geomorphic change in Squamish River has accelerated during the 1980s to the mid‐1990s. Among four study reaches of varying planform, erosional, depositional and cumulative changes in floodplain surface‐area have rapidly increased. Channel‐change activity after 1980 has increased by a factor of two to six compared with the period prior to 1980. Erosion is currently outpacing deposition in the majority of study reaches. Although channel geometry generally exhibits no uniform pattern of response to the increase in extreme floods, the meandering reaches have straightened over the duration of the study period. The increase in the magnitude and duration of the annual flood appears to be the principal cause of this recent acceleration of channel change. Copyright © 2010 John Wiley & Sons, Ltd.     

气压变化对SS-Y伸缩仪观测日变曲线的干扰分析

根据SS-Y伸缩仪的原理,从理论和实际观测分析了气压变化对伸缩应变观测日变曲线的影响及两者间的相关性。分析表明,应变观测值波动与气压变化呈正比例关系,也就是说两者之间是正相关。因此认为气压变化是伸缩仪观测日变曲线畸变的主要因素之一。为减小气压变化对观测的影响还对台站仪器架设提出了几点改进建议。     

Bootstrap Pettitt test for detecting change points in hydroclimatological data: case study of Itaipu Hydroelectric Plant,Brazil

ABSTRACT

The Pettitt test is widely used in climate change and hydrological analyses. However, studies show difficulties of this test in detecting change points, especially in small samples. This study presents a bootstrap application of the Pettitt test, and compares it numerically with the classical Pettitt test by an extensive Monte Carlo simulation. The proposed test outperforms the classical test in all simulated scenarios. An application of the tests is conducted on the historical series of naturalized flows of the Itaipu Hydroelectric Plant in Brazil, for which several studies have shown a change point in the 1970s. When the series is split into shorter sub-series, to simulate actual situations of small samples, the proposed test is more powerful than the classical Pettitt test in detecting the change point. The proposed test can be an important tool for detecting abrupt changes in water availability, in support of hydroclimatological resources decision making.     

Sensitivity of the river Rhine discharge to environmental change,a first tentative assessment

Changes in climatic conditions may have great impact on the distribution of available water in space and time. However the results of models that describe future climate conditions are still insufficient to be used in regional hydrological simulation studies. This article describes a first tentative estimation of the sensitivity of discharge of the river Rhine to two environmental changes. Firstly, to a change in snow covered area due to a rise of 4°C in winter temperature in the upland part (Alps) of the drainage area and, secondly, to a large land use change in the lowland area (Federal Republic of Germany/France). ‘Worst case’ scenarios for discharge of the river Rhine under warmer conditions give a reduction of 10 percent for the summer discharge at Rees (Dutch/German border). The results of the estimations indicate that the reduction of the summer discharge in a warmer world could be larger.     

Testing the robustness of the physically-based ECOMAG model with respect to changing conditions

Abstract

The robustness of the physically-based, semi-distributed hydrological model ECOMAG with respect to changing (climatic or land-use) conditions was evaluated for two basins, considered within the modelling workshop held in the frame of the 2013 IAHS conference in Göteborg, Sweden. The first basin, the Garonne River basin, France, is characterized mostly by changes in climatic conditions, while the second, Obyån Creek, Sweden, was exposed to drastic land cover change due to deforestation. Tests were conducted to evaluate the model’s ability to simulate with acceptable accuracy the changing hydrological regime of each basin and to retain, in the process, relatively stable values of the parameters. Acceptable performance of the ECOMAG model was obtained under the different combinations of the calibration/evaluation periods, including, importantly, the periods of hydrological regime changes in both basins.     

Climatic and environmental changes at southeastern coast of Lake Biwa over past 3000 years, inferred from borehole temperature data

In order to infer past climatic change in central Japan, we measured temperatures in a borehole at the Karasuma site, on the southeastern coast of Lake Biwa, and reconstructed sediment surface temperature history during the last 3000 years. The reconstructed temperature history shows apparent Medieval Warm Period, Little Ice Age, and contemporary temperature warming. However, the large amplitude of the temperature changes up to 4-5 K cannot be explained by past climatic change only, suggesting that there was some other cause of the larger amplitude temperature changes. The onsets of temperature decrease in the late 12th century a.d. and temperature increase in the mid 17th century a.d. appear to coincide with occurrences of two destructive earthquakes (1185 and 1662 a.d.) that caused water level changes of Lake Biwa. It suggests that the reconstructed sediment surface temperature history reflects the environmental change due to tectonically induced water level changes of the lake. If the annual mean of the ground surface temperature was higher than that of the bottom water temperature in a shallow part of the lake, which is consistent with the present-day data, the large amplitude of the sediment surface temperature change may be attributed to a combined effect of past climatic and environmental changes. Thus, we suggest that the borehole temperature at the Karasuma site preserves information not only on past climate changes but also on environmental changes due to tectonically induced water level changes.     

洞庭湖流域气候变化特征(1961-2003年)

以22个气象站1961-2003年的气象观测数据为基础,对洞庭湖流域的气温、降水和参照蒸散量进行趋势与突变分析．从1970年开始,洞庭湖流域经历了一个缓慢而稳定的增温过程,1990s发生突变进入快速增温时期;尤其是是在春、冬季节,这种突变式的增温特征非常显著;秋季持续而稳定增温,而夏季气温并无明显变化．进入1990s,洞庭湖流域降水有明显增多,尤其是夏季降水突变式增加;与此同时,夏季暴雨频率也突变式增大,但是暴雨强度并无明显变化．1900s迄今,参照蒸散量持续而稳定的减少,夏季减少量尤为显著．全球变暖的区域响应,驱动洞庭湖流域水循环速度加快,夏季降水增多,而蒸发能力减弱,这是1990s洞庭湖流域洪水频发的主要气候因子．     

Testing the robustness of the physically-based ECOMAG model with respect to changing conditions

Abstract

The robustness of the physically-based, semi-distributed hydrological model ECOMAG with respect to changing (climatic or land-use) conditions was evaluated for two basins, considered within the modelling workshop held in the frame of the 2013 IAHS conference in Göteborg, Sweden. The first basin, the Garonne River basin, France, is characterized mostly by changes in climatic conditions, while the second, Obyån Creek, Sweden, was exposed to drastic land cover change due to deforestation. Tests were conducted to evaluate the model’s ability to simulate with acceptable accuracy the changing hydrological regime of each basin and to retain, in the process, relatively stable values of the parameters. Acceptable performance of the ECOMAG model was obtained under the different combinations of the calibration/evaluation periods, including, importantly, the periods of hydrological regime changes in both basins.