Crystal size distributions and other quantitative textural measurements in lavas and tuff from Egmont volcano (Mt. Taranaki), New Zealand

 The size, shape and orientation of plagioclase crystals have been quantified in a tuff and series of andesite lavas from the active Egmont volcano (Mt. Taranaki), New Zealand. Linear crystal size distributions (CSDs) show that if the magma had several components, then only one provided the crystals. The slope of the CSD indicates that the earliest lavas measured had a residence time of ∼50 years in the magma chamber for a growth rate of 10^–11 cm/s. Subsequent lavas had slightly longer residence times (50–75 years), but the following series returned to 50-year residence times. The youngest magmas, from both Egmont summit and the parasitic Fantham's Peak, have the shortest residence times of ∼30 years. Variations in residence time may reflect changes in the magma chamber shape or depth, or the temperature of the surrounding rocks. Crystal shapes and zonation suggest that crystallization occurred in a bottle-shape magma chamber, and not in a narrow conduit. If future eruptions use the same magma chamber as the most recent eruptions, then a delay of approximately 30 years can be expected between refilling and eruption. Received: 25 October 1995 / Accepted: 19 April 1996     

大同－阳高地震的地磁异常研究

对大同－阳高地震的地磁场△Ｆ时、空变化做了分析。认为６．１级地震前８个月山西北部地磁场△Ｆ出现异常，同年９月达高潮。６．１级地震后的１９９０年３月地磁场活动又出现了第２次高潮。２次高潮的异常幅度分别为１３．０ｎＴ和１３．２ｎＴ。大同－阳高地震的地磁异常具有时段长，连续性好，空间分布广的特点。     

最大主应力σ1等值线分布与唐山7.8级地震的关系

对唐山大震前最大主应力σ１的等值线平面图进行分析，可以看出：从１９７６年４月前后开始，所圈定的等值线图的椭圆长轴的方向由北北东方向转为北东东方向。震中区的高值应力σ１值达到５×９８．０６６５ｋＰａ以上。异常面积区域可达１×１０＾６ｋｍ＾２以上。     

模拟深井条件下的PDC钻头破岩试验研究

利用深井破岩试验装置模拟不同井深压力条件下对泥岩进行了ＰＤＣ钻头破岩试验，试验结果表明，随着井深的增加，岩石强度增加，破碎岩石的切削力增加，同时，ＰＤＣ钻头齿形和结构对破岩效率影响较大，因此必须按深井条件和岩石特点进行ＰＤＣ钻头齿形和结构设计，以达到提高机械钻速的目的。     

矿物晶体形态数据管理模型的研究

根据数据库管理系统原理，在矿物晶体形态计算机绘图的基础上，建立了一种适合于矿物晶体形态数据特征并具有一般数据库功能的数据输入与管理模型。该模型可以有效地管理矿物晶体形态数据（存储、查询、索引、编辑、分类等），并且可根据其有关信息计算晶体结晶要素、面角、绘晶体图等。     

基于有限元模型和模态参数的损伤识别

本文从特征值问题出发 ,结合结构系统的有限单元模型并引入单元损伤因子 ,导出了求解单元损伤因子的方程 ,从而可以确定结构的损伤位置和损伤程度。利用简支梁进行了数值模拟 ,建立了简支梁的有限单元模型 ,用不同单元弹性模量的降低来模拟各种不同的损伤工况 ,并对每种工况进行了损伤位置和损伤程度识别 ,数值模拟结果同实际情况吻合很好。     

An investigation of breaker heights, shapes and pressures

The shape of breaking waves has a significant effect on wave impact pressures on vertical sea walls. In order to refine the results of previous researchers, a systematic study of breaker shapes and wave impact pressures on a vertical wall using a newly developed experimental technique, sequential flash photography, was conducted at Queen's University of Belfast. Assumptions, like the existence of a vertical flip-through jet or a parallel face impact, could not be confirmed. The maximum pressure was found to occur for plunging breakers and at Still Water Level (SWL), although high pressures can also occur for other breaker types above or below SWL.     

水化地震异常变化速率分析与综合预测方法新探索

水化群体异常的演化趋势与地震活动密切相关。中强地震前,水化异常变化速率值呈现“增长－地震”的普遍规律。在月、旬和五日等不同时间尺度上的水化群体异常演化图式,具有显著的自相似性和可重复的特征,并可分别作为地震的短期、短临和临震前兆标志与发震的判别依据。     

New insight into the evolution of large-volume turbidity currents: comparison of turbidite shape and previous modelling results

The Marnoso Arenacea Formation provides the most extensive correlation of individual flow deposits (beds) yet documented in an ancient turbidite system. These correlations provide unusually detailed constraints on bed shape, which is used to deduce flow evolution and assess the validity of numerical and laboratory models. Bed volumes have an approximately log‐normal frequency distribution; a small number of flows dominated sediment supply to this non‐channelized basin plain. Turbidite sandstone within small‐volume (<0·7 km³) beds thins downflow in an approximately exponential fashion. This shape is a property of spatially depletive flows, and has been reproduced by previous mathematical models and laboratory experiments. Sandstone intervals in larger‐volume (0·7–7 km³) beds have a broad thickness maximum in their proximal part. Grain‐size trends within this broad thickness maximum indicate spatially near‐uniform flow for distances of ∼30 km, although the flow was temporally unsteady. Previous mathematical models and laboratory experiments have not reproduced this type of deposit shape. This may be because models fail to simulate the way in which near bed sediment concentration tends towards a constant value (saturates) in powerful flows. Alternatively, the discrepancy may be the result of relatively high ratios of flow thickness and sediment settling velocity in submarine flows, together with very gradual changes in sea‐floor gradient. Intra‐bed erosion, temporally varying discharge, and reworking of suspension fallout as bedload could also help to explain the discrepancy in deposit shape. Most large‐volume beds contain an internal erosion surface underlain by inversely graded sandstone, recording waxing and waning flow. It has been inferred previously that these characteristics are diagnostic of turbidites generated by hyperpycnal flood discharge. These turbidites are too voluminous to have been formed by hyperpycnal flows, unless such flows are capable of eroding cubic kilometres of sea‐floor sediment. It is more likely that these flows originated from submarine slope failure. Two beds comprise multiple sandstone intervals separated only by turbidite mudstone. These features suggest that the submarine slope failures occurred as either a waxing and waning event, or in a number of stages.