北部湾6．1、6．2级地震序列特征

通过对北部湾６．１、６．２级地震的时空分布及地震类型的分析，认为北部湾地震属双主震型序列。６．１级地震的余震序列表现出鲜明的主余震型序列特征，而６．２级地震的余震序列震群型特征较为突出。６．２级地震前，地震序列活动显示出应变释放加速、低ｂ值、加卸载响应比跃升等异常现象。     

地震活动时序谱的涨落统计特征与地震活跃期

为寻求地震活动演化的统计判据，本文采用多项式拟合法展示地震时序谱之涨落谱，以分维函数法判断最小邻间距（NNS）分布的Poisson性，然后采用MKS无参量法判别涨落谱之统计稳定性，确定NNS分布的转变区，具体研讨了四川、云南若干震区地震活动时序谱的涨落统计分布，发现地震活跃期到来时NNS分布表现出非Poisson化的特征。进一步通过改变和调节时序数据样本集之震级下限，并逐段前推进行统计计算的方式进一步验证结果的可靠性，客观地确定了这些震区地震活动时序涨落谱统计特征的转变期，使根据该统计法判断地震活跃期的方法论渐趋完善。     

山东苍山5.2级地震活动背景及震前地震活动

分析了山东苍山５２级地震前的历史地震活动、现今中小地震活动的时空分布及地震活动的异常特征。表明,苍山５２级地震强度和空间分布与历史地震活动强度和空间分布特征相一致,并具有某些大震的异常特征,震前出现了长达１２ａ的背景空区,出现了“信号震”和孕震空区,出现了多种测震学指标异常等。     

临汾盆地地震危险性浅析

本文通过强震地震穴的地震序列分析，华北地震迁移、汾渭地震带地震丛式分布，和地震丛的强度分析以及汾渭地震带分段及强弱段相间分布特征，与本活动期地震丛活动空间分布等论述了临汾地震的危险性。     

2019年地震活动综述

回顾总结了2019年地震活动,从全球到局部,呈现了全球、中国和四川的地震活动概况;分析了全球、中国和四川地震活动的特征;记叙了2019年四川区域内发生的突出地震事件;追踪了2008年汶川8.0级地震以来四川区域内发生的3次7级以上地震的余震活动。结果显示:2019年全球M≥7.0地震活动特征呈现低频次、低强度,主体地区为环太平洋地震带;我国周边未发生M≥7.0地震,表明影响我国地震活动的动力边界地震活动偏弱,我国大陆和邻区地震活动表现出频次低、强度弱的特点,我国大陆地震分布总体显示强度西强东弱,区域上显示M≥5级地震分布于青藏地块、西域地块和华南地块;台湾及其附近海域地震活动频次和强度也偏低;四川区域地震活动强度呈现东强西弱特征,四川区域突出地震事件全部集中在川东南区域;2008年以来,四川区域的汶川8.0级、芦山7.0级和九寨沟7.0级地震的余震持续活动。     

2014年云南鲁甸6.5级地震序列跟踪分析研究

从云南鲁甸6.5级地震序列活动特征、序列参数、历史地震活动类比、余震精定位、较大地震震源机制、发震构造分析等方面分析了鲁甸地震序列的序列类型及后续强余震预测问题.分析认为,鲁甸地震序列余震活动表现出明显的阶段性.鲁甸地震序列M≥4.0地震时间间隔遵从线性关系、精定位结果显示余震呈共轭分布、地震震源机制结果显示震源机制一致性程度较低、历史地震序列类比表明鲁甸地震序列与1974年大关7.1级地震序列活动特征类似,这些均表明鲁甸地震序列类型为主—余型.     

新疆天山地震灾害的初步分析

利用新疆天山地区丰富的地震资料，通过天山地区灾害性地震的空间分布、历史地震烈度分布、地震地表破坏特征、地震灾害损失论述了新疆天山地震灾害特征，分析了灾害成因。     

福建及邻区地震序列类型分布特征分析

整理和分析了1971～2009年发生在福建及邻区的46组地震序列.结果显示:福建地区具有较明显的地震序列类型分区特征:东部沿海地区以孤立型或主余震型地震活动为主,而西部内陆地区多发生震群型地震;地震序列类型分布特征可能与福建地区地震动力作用、构造应力场及地震断层运动性质、地层岩性分布特征有关,同时地震序列类型分布特征也...     

2009年乌什-阿图什地震危险区异常跟踪

分析了乌什-阿图什地震危险区所处的柯坪块体地震时空活动特点:6级以上地震均沿块体边缘分布;6级地震时序分布不均匀,空间分布表现出轮回特征;6级地震前4级地震平静较为普遍,相关构造带以增强-平静为主要特征;响应地震的地点指示意义较为明确。文中还对危险区异常判定及2009年块体3次5级地震异常跟踪进行了总结。     

2008年3月30日甘肃肃南5.0级地震特征

2008年3月30日在甘肃省肃南县皇城镇一带发生了一次MS5.0地震。本文归纳总结了本次地震的基本地震参数、序列特征,利用P波资料计算了震源机制解,根据地震现场考察结果分析了烈度分布特征。综合本次地震的地质构造和历史地震活动背景、震源机制、余震分布、极震区长轴方向分析了本次地震的发震构造,结果显示本次地震的发震构造不清晰。     

Role of dykes in induced seismicity at Bhatsa reservoir,Maharashtra, India

The geological and hydrological conditions near the reservoir site play an important role in the generation or absence of seismic activity. Near Bhatsa reservoir, along the west coast of India intense seismic activity occurred during August–September 1983, after a lag of six years of initial impounding. From July 1983 to September 1990, 15,388 earthquakes (mostlyM ₁<3.0) were recorded, the largest being of magnitude 4.9. The spatial distribution of well located 172 earthquakes suggest a strong correlation between the epicenters and the disposition of dykes and faults around the Bhatsa region. It is inferred that these dykes have acted as barriers for the diffusion of water from the reservoir, thereby becoming zones of instability due to increased pore pressure not only along them but also over the volume they bound.     

Use of an Artificial Sweetener to Identify Sources of Groundwater Nitrate Contamination

The artificial sweetener acesulfame (ACE) is a potentially useful tracer of waste water contamination in groundwater. In this study, ACE concentrations were measured in waste water and impacted groundwater at 12 septic system sites in Ontario, Canada. All samples of septic tank effluent (n = 37) had ACE >6 µg/L, all samples of groundwater from the proximal plume zones (n = 93) had ACE >1 µg/L and, almost all samples from the distal plume zones had ACE >2 µg/L. Mean mass ratios of total inorganic nitrogen/ACE at the 12 sites ranged from 680 to 3500 for the tank and proximal plume samples. At five sites, decreasing ratio values in the distal zones indicated nitrogen attenuation. These ratios were applied to three aquifers in Canada that are nitrate‐stressed and an urban stream where septic systems are present nearby to estimate the amount of waste water nitrate contamination. At the three aquifer locations that are agricultural, low ACE values (<0.02‐0.15 µg/L) indicated that waste water contributed <15% of the nitrate in most samples. In groundwater discharging to the urban stream, much higher ACE values (0.2‐11 µg/L) indicated that waste water was the likely source of >50% of the nitrate in most samples. This study confirms that ACE is a powerful tracer and demonstrates its use as a diagnostic tool for establishing whether waste water is a significant contributor to groundwater contamination or not.     

地壳中的CO2及其释放与地震短临预测

该文通过对地壳中二氧化碳（ＣＯ２）的分布及其与多震层的关系,以及地壳中ＣＯ２的释放与地震活动关系的分析,探讨了断层带ＣＯ２监测在强震短临预测阶段对时间判定的作用,提出应进一步加强对断层带ＣＯ２释放的监测与研究。     

Seismotectonic and refraction seismic investigations in the border region between the Eastern Alps and the Pannonian Basin

Focal solutions of four strong earthquakes and P signals of twenty-four smaller shocks of the active Mur-Mürz Valley, the Semmering Pass and the Vienna Basin. An equivalent slip rate of 0.03 This feature agrees with the model of a subsiding Pannonian Basin. An equivalent slip rate of 0.03 cm/year is roughly estimated from earthquake data 1903–1978. This rate does not include the creep rate, but it gives an idea of the magnitude of speed of geological processes in this area.Refraction seismic data from the Alpine Longitudinal Profile 75 shows a low velocity zone in the upper crust of the seismic active East Alpine area but not in the aseismic part of the Pannonian Basin.The eastern margin of the Eastern Alps and the Carpathians limits the Pannonian Basin, which has a special and interesting geological history. Many authors (Szadezky-Kardoss, 1966;Stegena, Ceszy andHorvàth, 1975) presented models of the genesis of the Pannonian Basin. They apply the concept of the mantle diapirs to explain the following facts:subsiding of the Pannonian Plate in comparison to the Alps, high terrestrial heat flow within the Pannonian Plate, decrease of the Moho depth from 40 km below the Eastern border of the Alps to 27 km below the Pannonian Basin. They claim that the Alpine-Carpathian interarc and basin represent the final stage of an orogenetic system where subcrustal erosion leads to a thinning of the crust. Consequently the surface subsides and is covered by young sediments. They proved that this subsidence and sedimentation is more or less in isostatic equilibrium. The aim of this paper is to provide new arguments using focal solutions and refraction seismic investigations.     

川滇块体边界断裂的CO2释放及其来源

川滇块体边界断裂沿线及附近地区有大量的CO_2泉出露,其分布与1900年以来强震震中的分布大体一致,这表明该区CO_2释放可能与现代地震活动有直接关联。稳定碳、氧同位素证据表明,现代活动断裂释放的CO_2绝大部分来自地壳深部,并有两种主要的释放机制。现代活动断裂既可以直接产生大量的热动力变质成因CO_2,又可以作为通道释放来自下地壳甚至上地慢的CO_2组分。连续监测深源CO_2的释放动态有可能获得反映震源物理化学变化的地震前兆信息。     

First Order Seismic Microzonation of Haldia, Bengal Basin (India) Using a GIS Platform

The seismic microzonation of the Bengal Basin, Haldia region, India is carried out using the Analytical Hierarchy Process (AHP) on the Geographic Information System (GIS). Three themes are used for the seismic microzonation, namely Peak Ground Acceleration (PGA), predominant frequency and elevation map. An analysis of the maximum magnitude (m _max) and the b value is carried out after preparing the earthquake catalogue from various sources. On the basis of the tectonic set up and seismicity of the region, five seismic zones are delineated which can be a threat to Haldia. They are broadly classified as Zone 1: Arakan-Yoma Zone (AYZ), Zone 2: Himalayan Zone (HZ), Zone 3: Shillong Plateau Zone (SPZ), Zone 4: Bay of Bengal Zone (BBZ) and Zone 5: Shield Zone (SZ). The m _max for Zones 1, 2, 3, 4 and 5 are 8.30 ± 0.51, 9.09 ± 0.58, 9.20 ± 0.51, 6.62 ± 0.43 and 6.61 ± 0.43, respectively. The PGA value is computed for Haldia following the attenuation relationship taking the m _max of each source zone. The expected PGA at Haldia varies from 0.09–0.19 g. The predominant frequency of Haldia is also calculated using the H/V ratio with a frequency ranging from 0.1–3.0 Hz. The elevation map of Haldia is also generated using the Shuttle Radar Topography Mission (STRM) data. A first-order seismic microzonation map of Haldia is prepared in which four zones of hazard have been broadly classified for Haldia as very high seismic hazard zone, high seismic hazard zone, moderate seismic hazard zone and less seismic hazard zone. The very high seismic hazard zone is observed along the southern part of Haldia where there are major industrial and port facilities. The PGA for the four hazard zones are: 0.09–0.13 g for low hazard zone, > 0.13–0.15 g for moderate hazard zone, > 0.15–0.16 g for high hazard zone and > 0.16–0.19 g for very high hazard zone.     

中国大陆科学钻探工程主孔地下流体特征及与地震活动的关系初步研究

收集了中国大陆科学钻探主孔工程(CCSD)主孔中117～2045 m深度地下流体某些组分(He、 Ar、 CO₂、 CH₄)的浓度资料和2001年7月1日至2002年4月30日时间段内钻孔周围500 km范围内震级M_L≥1.0地震目录资料, 对其流体资料进行日均值处理、 差分分析和最大相关系数处理。 由日均值浓度看出地震前后He、 Ar、 CO₂、 CH₄浓度存在明显异常; 最大相关系数分析表明, CH₄和CO₂组分两者相关性好, 最大相关系数平均值为0.95, 均方差为0.08, 说明两者可能具有相同的来源。 CH₄和CO₂浓度日均值最大相关系数在地震前后出现明显的异常波动。 主孔中的地下流体特征及与周围地震活动的对应关系揭示大陆科学钻探主孔中的地下流体异常与区内地震活动可能存在一定关系。     

Transmissivity variations in mudstones

Many people in sub-Saharan Africa have to rely on meager water resources within mudstones for their only water supply. Although mudstones have been extensively researched for their low permeability behavior, little research has been undertaken to examine their ability to provide sustainable water supplies. To investigate the factors controlling the occurrence of usable ground water in mudstone environments, an area of Cretaceous mudstones in southeastern Nigeria was studied over a 3 yr period. Transmissivity (T) variations in a range of mudstone environments were studied. The investigations demonstrate that within the top 40 m of mudstones, transmissivity can be sufficient to develop village water supplies (T > 1 m2/d). Transmissivity is controlled by two factors: low-grade metamorphism and the presence of other, subordinate, lithologies within the mudstones. Largely unaltered mudstones (early diagenetic zone), comprising mainly smectite clays, are mostly unfractured and have a low T of < 0.1 m2/d. Mudstones that have undergone limited metamorphism (late diagenetic zone) comprise mixed layered illite/smectite clays, and ground water is found in widely spaced fracture zones (T > 1 m2/d in large fracture zones; T < 0.1 m2/d away from fracture zones). Mudstones that have been further altered and approach the anchizone comprise illite clays, are pervasively fractured, and have the highest transmissivity values (T > 4 m2/d). Dolerite intrusions in unaltered, smectitic mudstones are highly fractured with transmissivity in the range of 1 < T < 60 m2/d. Thin limestone and sandstone layers can also enhance transmissivity sufficiently to provide community water supplies.     

Perch larvae (Perca fluviatilis L.) survive better in dilute sea water

Larvae of perch (Perca fluviatilis L.) reared in tanks for 27 days survived better in lake water to which 2% of artificial sea water had been added (46.6% average survival rate) than in lake water only (13.5% survival). One week after hatching, over 90% of the larvae had their guts filled in all tanks. During the following week the populations divided into floaters (fish with an inflated swimbladder) and sinkers (fish apparently lacking a functional swim-bladder). Although they continued feeding, sinkers remained smaller than floaters and most of them died.     

Evaluation of the seismic performance of a three‐story ordinary moment‐resisting concrete frame

This study focuses on the seismic performance of Ordinary Moment‐Resisting Concrete Frames (OMRCF) designed only for gravity loads. For this purpose, a 3‐story OMRCF was designed in compliance with the minimum design requirements in the American Concrete Institute Building Code ACI 318 (1999). This model frame was a regular structure with flexure‐dominated response. A 1/3‐scale 3‐story model was constructed and tested under quasi‐static reversed cyclic lateral loading. The overall behavior of the OMRCF was quite stable without abrupt strength degradation. The measured base shear strength was larger than the design base shear force for seismic zones 1, 2A and 2B calculated using UBC 1997. Moreover, this study used the capacity spectrum method to evaluate the seismic performance of the frame. The capacity curve was obtained from the experimental results for the specimen and the demand curve was established using the earthquake ground motions recorded at various stations with different soil conditions. Evaluation of the test results shows that the 3‐story OMRCF can resist design seismic loads of zones 1, 2A, 2B, 3 and 4 with soil types S_A and S_B . For soil type S_C , the specimen was satisfactory in seismic zones 1, 2A, 2B and 3. For soil type S_D , the OMRCF was only satisfactory for seismic zones 1 and 2A. Copyright © 2004 John Wiley & Sons, Ltd.