Sequential radiocarbon measurement of bulk peat for high-precision dating of tsunami deposits     

《Quaternary Geochronology》2017

Dates of tsunami deposits have been used to estimate paleotsunami recurrence intervals in areas affected by these natural events. The depositional age of tsunami deposits is commonly constrained by the radiocarbon (¹⁴C) dating of sediments above and below the geological event. However, because of calibration curve fluctuations, the depositional age sometimes has a wide error range. In this study, we conducted millimeter-scale high-resolution radiocarbon measurements of tsunami deposits at Urahoro in southern Hokkaido, Japan. The site faces the Pacific Ocean along the Kuril Trench. Eight event deposits were identified within peat at this site. We took sequential measurements for ¹⁴C dating using bulk peat samples. The results were validated based on comparison with the absolute and radiometric ages of tephra layers. Dating results were further constrained by stratigraphic order using statistical methods. We constrained the depositional age of the paleotsunami deposits better using this method than we did when using conventional methods. We proposed an efficient measurement strategy with respect to the radiocarbon calibration curve. This method is also applicable for other deposits formed by any natural hazard if bulk peat is obtainable so it can contribute to better hazard assessment worldwide.  相似文献   

太山龙泉寺舍利塔边坡地震稳定性研究          下载免费PDF全文

丁学文  李国珍  丁志平  李申  冯凯宇 《地震工程学报》2020,42(6):1632-1640,1722

为了研究太原市太山龙泉寺拟建舍利塔边坡稳定性,对所在场地及外围地形地貌、地层、地质构造、水文条件进行了调查。结合7个探井,确定了塔址所在场地的土质边坡体可能失稳的模式,进行了边坡稳定性分析、计算。结果表明,场地在自然状态下边坡稳定系数为1.37,在烈度为Ⅷ、Ⅸ度地震影响下边坡稳定系数分别为1.24、1.15。根据《建筑边坡工程技术规范》（GB50330-2013）,塔址所在边坡是稳定的,不必对边坡进行处理;其次结合3个探槽揭露,发现场地北侧基岩边坡曾发生过滑动,据其滑动面倾角、滑动量及错断地层特征,认为是一种特殊边坡变形破坏-岩体错落,为崩塌与滑坡之间的中间类型,从现存的地形地貌特征分析,现阶段错落体已趋于基本稳定状态,稳定性较好;最后给出了预防边坡滑动的建议和措施,研究结果可为其他类似边坡场地地震稳定性研究提供参考借鉴。  相似文献   

大口径嵌岩钻进技术发展与展望          下载免费PDF全文

甘行平 《探矿工程》1998,(6):5-7

分析了大口径嵌岩钻进面临的主要技术难点,并对目前国内常用的３种大口径嵌岩钻进方法－牙轮／滚刀钻进法、冲击钻进法（包括无循环和反循环）和气动／液动潜孔锤钻进法的技术现状作了介绍,提出了提高我国大口径嵌岩钻进技术水平的建议。  相似文献   

马尼拉海沟几何形态特征的构造演化意义   总被引：4，自引：0，他引：4  

陈志豪  李家彪  吴自银  吴振利  尚继宏 《海洋地质与第四纪地质》2009,(2)

通过对马尼拉海沟海底地形地貌、构造特征及其相关地震等数据资料的分析,结合俯冲带动力学数值模拟成果,尤其是Schellart等的模式,详细讨论了马尼拉海沟几何形态、海沟南北段俯冲角度突变等构造特征。分析认为,南海中代表古扩张脊的黄岩海山链的俯冲挤入对马尼拉俯冲带的几何形态没有造成较大的影响,其几何形态较符合中等长度(2000～3000km)的海沟模型。由海沟后退和板片反转引起的平行于马尼拉海沟方向的地幔流加剧了海沟南北段俯冲角度的突变。  相似文献   

高速铁路运行引发场地振动的空沟隔振分析          下载免费PDF全文

肖慧娟  董尘 《地震工程学报》2021,43(6):1419-1428

为研究高速列车作用下,层状地基中空沟对场地振动的隔振效果,基于车辆-轨道耦合动力学理论及有限元法,对建立完善高速车辆-无砟轨道-地基耦合系统动力学模型进行仿真计算,分析设置空沟对场地振动的影响,并探讨了空沟的深度、位置、宽度以及列车速度的影响。结果表明：设置空沟加强了沟前场地的振动,但可使空沟后方地基的竖向和水平振动水平大幅减小,但在特定位置存在振动放大区,引起隔振效果减弱;过浅或过深的空沟均不能达到最优隔振效果;对于在线路旁需要特殊隔振的场地,存在一个适用于其本身的空沟最佳位置;空沟的宽度对隔振效果无明显影响;空沟对更高速度运行列车引起场地竖向和横向振动的隔振效果更明显。  相似文献   

Bathymetric patterns of meiofaunal abundance and biomass associated with the Kuril and Ryukyu trenches, western North Pacific Ocean   总被引：2，自引：0，他引：2  

Makoto Itoh  Kiichiro KawamuraTomo Kitahashi  Shigeaki KojimaHideki Katagiri  Motohiro Shimanaga 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):86-97

The abundance and biomass of metazoan meiofauna and their relationships with environmental factors [chloroplastic pigment equivalents (CPE) and sediment characteristics] were studied quantitatively around and within the Kuril Trench (560-7090 m) and the Ryukyu Trench (1290-7150 m), which are located in eutrophic and oligotrophic regions, respectively, of the western North Pacific. Faunal abundance and biomass, as well as the CPE content of sediments, were considerably higher in the Kuril region than in the Ryukyu region. In both cases, CPE tended to decrease with water depth, but relatively high values were found in the deepest areas, suggesting that organic matter has accumulated in both trenches. Meiofaunal abundance and biomass were lower than expected from sediment CPE values at hadal stations below 6000 m. Differences in the density and biomass of meiofauna between these two trenches appeared to reflect differences in overall ocean productivity above them. When the analysis was restricted to each region, however, no association was found between the abundance and biomass of meiofauna and food availability. Furthermore, the factors regulating the bathymetric patterns in these meiofaunal parameters appeared to differ between the two trenches.  相似文献   

印尼8.7级地震对川滇地区地震活动的影响   总被引：2，自引：2，他引：0  

焦青  范国胜  戴梁焕 《大地测量与地球动力学》2005,25(3):100-104

对1900年以来印尼爪哇海沟地区发生的8.0级以上地震与川滇地区5.0级以上地震作了统计、对比和分析,并利用跨断层位移流动观测资料,对2004年12月26日印尼苏门答腊西部海域8.7级地震前后,川滇地区的区域构造活动变化进行了分析研究,初步认为:印尼8.7级地震后,川滇地区1~3年内发生7.0级以上地震的可能性不大;1~2年内发生6~7级地震的可能性较大;1年内发生5级以上地震至少两次;纬度27°以南地区可能是未来1年内发震的危险地区,地球自转速度减慢,可能预示川滇地区强震活跃期即将到来。  相似文献   

计算机辅助计算修正正前角成形铣刀的重磨角度     

钟罗杰 《广东海洋大学学报》1997,(1)

采用计算机辅助计算修正重磨前角，能解决正前角成形铣刀重磨后加工零件廓形误差大的问题。改变正前角成形铣刀只能用作粗加工的观念，可将正前角成形铣刀用于成形面的精加工。  相似文献   

北祁连西段早古生代构造演化史   总被引：21，自引：2，他引：21  

左国朝  毛景文 《甘肃地质》1999,8(1):6-13

北祁连西段与北祁连中段构造带之间被一条平行于阿尔金断裂带的宗宾大坂古转换断裂所隔，东西两段在早古生代构造演化史上有明显差异。北祁连西段早古生代构造是在前震旦系陆壳基底上，在震旦纪再一次开裂演变为裂陷槽，寒武—奥陶纪为裂谷—海沟—火山弧多元构造的格局  相似文献   

综合管沟竣工测量数据处理的技术     

樊惠萍  张汉春 《地理空间信息》2011,(4):16-18

综合管沟近年来在广州得到越来越多的推广应用,因而研究综合管沟的数据信息系统显得十分必要。介绍了广州大学城、广州亚运城的综合管沟的基本情况,管沟类型,沟内管线分布,内业成图的图层设计、数据库设计,重点探讨了新出现的立交型综合管沟处理技术,实现了综合管沟数据库的科学管理。  相似文献