珊溪水库震群的地震定位     

李金龙  邹振轩  张震峰 《地震地磁观测与研究》2007,28(1):14-18

2006年2月,位于浙江文成与泰顺交界的珊溪水库发生了最大震级为ML4.6的震群.我们分别利用浙江省区域数字地震台网和珊溪水库现场数字监测网的观测数据,运用不同的定位方法,对震群进行了定位.通过比较分析,讨论了不同的定位方法与不同观测数据的定位效果.  相似文献   

Structure and emplacement of the Nandurbar–Dhule mafic dyke swarm,Deccan Traps,and the tectonomagmatic evolution of flood basalts     

Ranjini Ray  Hetu C. Sheth  Jyotirmoy Mallik 《Bulletin of Volcanology》2007,69(5):537-551

Flood basalts, such as the Deccan Traps of India, represent huge, typically fissure-fed volcanic provinces. We discuss the structural attributes and emplacement mechanics of a large, linear, tholeiitic dyke swarm exposed in the Nandurbar–Dhule area of the Deccan province. The swarm contains 210 dykes of dolerite and basalt >1 km in length, exposed over an area of 14,500 km². The dykes intrude an exclusively basaltic lava pile, largely composed of highly weathered and zeolitized compound pahoehoe flows. The dykes range in length from <1 km to 79 km, and in thickness from 3 to 62 m. Almost all dykes are vertical, with the others nearly so. They show a strong preferred orientation, with a mean strike of N88°. Because they are not emplaced along faults or fractures, they indicate the regional minimum horizontal compressive stress (σ ₃) to have been aligned ~N–S during swarm emplacement. The dykes have a negative power law length distribution but an irregular thickness distribution; the latter is uncommon among the other dyke swarms described worldwide. Dyke length is not correlated with dyke width. Using the aspect ratios (length/thickness) of several dykes, we calculate magmatic overpressures required for dyke emplacement, and depths to source magma chambers that are consistent with results of previous petrological and gravity modelling. The anomalously high source depths calculated for a few dykes may be an artifact of underestimated aspect ratios due to incomplete along-strike exposure. However, thermal erosion is a mechanism that can also explain this. Whereas several of the Nandurbar–Dhule dykes may be vertically injected dykes from shallow magma chambers, others, particularly the long ones, must have been formed by lateral injection from such chambers. The larger dykes could well have fed substantial (≥1,000 km³) and quickly emplaced (a few years) flood basalt lava flows. This work highlights some interesting and significant similarities, and contrasts, between the Nandurbar–Dhule dyke swarm and regional tholeiitic dyke swarms in Iceland, Sudan, and elsewhere. Editorial responsibility: J. White  相似文献   

Analysis of State of Stress During The 1997 Earthquake Swarm In Western Bohemia     

Slancová  Alice  Horálek  Josef 《Studia Geophysica et Geodaetica》2000,44(2):272-291

Focal mechanisms of 70 events of the January 1997 earthquake swarm were analysed using the Gephart and Forsyth method to determine the state of stress in the West Bohemia/Vogtland region and to reveal possible stress variations during the swarm activity. The method was applied to the whole set of 70 focal mechanisms and to several subsets distinguishing magnitudes of events and the spatial and temporal distribution of the swarm. The three representative stress models A ( ₁ ,A: 0/45 (az/dip), ₂ A: 134/35, ₃ A: 243/25), B ( ₁ ,B: 162/38, ₂ B: 263/14, ₃ B: 10/49), and C ( ₁ C: 135/30, ₂ C: 1/50, ₃ C: 239/23) which could characterise the state of stress in the region were found. Model C can be considered to be the most probable stress model because of its consistency with the European stress field. The results of the stress analysis applied to the individual subsets of focal mechanisms indicate that the state of stress was more uniform during the first phase of the swarm. To distinguish between the fault plane and the auxiliary plane of fault plane solutions a statistical approach was used. The results showed that the fault planes striking NW-SE and dipping 45° to NE were activated during the swarm.  相似文献   

Relocation of microearthquake swarms in the Peloritani mountains – implications on the interpretation of seismotectonic patterns in NE Sicily, Italy     

L. Scarfî  H. Langer  A. Scaltrito 《Geophysical Journal International》2005,163(1):225-237

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Subsurface Temperature Changes Due to the Crustal Magmatic Activity – Numerical Simulation     

SŠafanda  Jan  Čermák  Vladimír 《Studia Geophysica et Geodaetica》2000,44(2):327-335

Geothermal aspects of the hypothesis, relating the earthquake swarms in the West Bohemia/Vogtland seismoactive region to magmatic activity, are addressed. A simple 1-D geothermal model of the crust was used to assess the upper limit of the subsurface heating caused by magma intrusion at the assumed focal depth of 9 km. We simulated the process by solving the transient heat conduction equation numerically, considering the heat of magma crystallization to be gradually released in the temperature interval 1100°C to 900°C. The temperature field prior to the intrusion was in steady-state with a surface temperature of 10°C and heat flow of 80 mWm ^–2 , the temperature at the 9 km depth was 270°C. The results suggest that the temperature and heat flow in the uppermost 1 km of the crust begin to grow 100 ka after the intrusion emplacement only, and that the amplitudes of the changes for the realistic lateral extent (a few kilometres) of the intrusion are very small. It was also found that the rate of magma solidification depends strongly on the thickness of the intrusion. It takes about 100 years for a 50 m thick sill to cool down from 1100°C to 600°C, which value represents the lower limit of the solidus temperature. The same cooling takes only 60 days if the sill is 2 m thick. If the nature of the strongly reflected boundaries, interpreted from the January 1997 Nový Kostel seismograms, is connected with the fresh emplacement of magma, the calculated cooling rates have a predictive potential for the temporal changes of the waveforms.  相似文献   

津巴布韦哈特利(Hartley)铂矿床地质特征及成因          下载免费PDF全文

龚鹏辉  刘晓阳  王杰  任军平  许康康  左立波  孙凯  刘宇 《地质找矿论丛》2015,30(S1):98-103

文章对产于津巴布韦大岩墙内的哈特利(Hartley)铂矿床的地质特征和成因进行研究。津巴布韦大岩墙于新太古代侵入,在津巴布韦克拉通内形成南北段次级岩浆房格局。哈特利铂矿的铂族元素主要分布在杂岩体的中下部,与硫化物密切相关,主要含矿矿物为铋、碲矿物。在岩浆侵位的过程中发生结晶分异,形成了铂族元素和硫化物的垂向分带。哈特利矿床与中国金川等铂族元素矿床相比,其成岩成矿时代早,矿床特征、成矿元素组合方面均有明显不同。  相似文献   

The Relation between Tectonic Movement and Climatic Change     

Xuexiang Yang  Qiyuan Qiao  Dianyou Chen 《世界地质(英文版)》2003,6(1)

Climate and tectonics are two interactive factors in the earth's system. They are controlled by astronomical cycles. It has been unheeded for a long time that large-scale material motion caused by global climatic change is one of the powers for tectonic movement. Tectonic movement makes the distributional pattern of continent and ocean change and makes global climate type change strongly in large scale. It is a good example that the change of the sea-ice around Antarctic Continent and in the Drake Passage has the switch process for global climatic changes. Tide makes the oceanic crust of the East Pacific Ocean and the West Pacific Ocean rise or fall 60 cm oppositely. Before and after El Nino events,the oceanic level of the East Pacific Ocean and the West Pacific Ocean may rise or fall 40 cm oppositely. Because of isostasy, oceanic crust may fall or rise 13 or 20 cm. They are the reasons why El Nino events are interrelated with the earthquakes and volcanoes. This is so called seesaw phenomenon of oceanic crust.  相似文献   

Graben-fissure systems in Guinevere Planitia and Beta Regio (264°-312°E, 24°-60°N), Venus, and implications for regional stratigraphy and mantle plumes     

R.E Ernst  D.W Desnoyers  E.B Grosfils 《Icarus》2003,164(2):282-316

Detailed mapping in a 14,000,000 km² area of northwestern Guinevere Planitia and northern Beta Regio bounded by 264°-312°E, 24°-60°N has revealed thousands of long extensional lineaments (graben, fissures and related fractures). These can be grouped into radiating, circumferential and linear systems. Thirty four radiating systems have been identified, of which 16 have radii greater than 300 km and eight have radii greater than 1000 km. Twenty six linear (straight) systems with a length greater than 300 km have been distinguished of which six have a length greater than 1000 km. Linear systems are generally associated with rifts, although some may represent distal portions of radiating systems. In addition, 19 circumferential systems, some associated with coronae, have been identified. The distribution of each system is compared with the host geology in order to place the graben-fissure systems in a regional stratigraphic framework. The majority of systems are: (1) younger than tesserae, ridge belts and densely fractured plains, (2) coeval with, and in many cases, define fracture belts, (3) partially flooded by wrinkle-ridged plains units, and (4) older than smooth and lobate plains units and young rifts. The inventory of radiating graben-fissure systems that we catalogue represents a database of tectono-magmatic centers that complements the centers defined using other criteria, e.g., large volcanoes, coronae, and shield fields. We have attempted to identify those systems that are underlain by dike swarms in order to evaluate their relationship to mantle plumes. At least 11 of the radiating systems extend well beyond any central topographic uplift and are therefore interpreted to be underlain by dike swarms.  相似文献   

新疆库鲁克塔格地区构造应力场解析   总被引：1，自引：0，他引：1       下载免费PDF全文

张鹏  侯贵廷  潘文庆  齐英敏  孟庆峰 《地质科学》2014,(1):69-80

通过对库鲁克塔格地区的构造地质演化分析,将该地区震旦系以来较强构造变形的构造应力场分4个时期：早古生代、晚古生代、中生代和新生代。根据节理、褶皱和岩墙等应力感构造的测量分析,得出库鲁克塔格地区及其周缘的4个时期构造应力场的最大主压应力方向分别为北北东向、北西西-北西向、北东向和北北东-近南北向。基于对新近纪以来库鲁克塔格地区构造应力场的二维有限元模拟,进一步对该地区应力场的分布特征、边界几何形态对应力场的影响等问题进行了讨论与分析。  相似文献   

岩墙群的岩石学、地球化学和几何学特征及其大地构造意义   总被引：2，自引：0，他引：2  

李宏博  张招崇  吕林素  汪云峰  寇彩化  廖宝丽  李永生 《岩石矿物学杂志》2012,31(1):91-103

对近几十年来岩墙群在构造环境、侵位模式、形成机制、岩相学、地球化学、同位素地质年代学、几何学和比较行星学等方面的研究成果进行了总结,为岩墙群的深入研究提供重要信息。岩墙群主要与伸展构造环境有关,是岩浆侵位事件(如地幔柱)造成上覆地壳形成裂隙系统,岩浆随后灌入而形成的。岩墙群的侵位模式主要有垂向和侧向两种,也可能是两种模式共同作用的结果。岩墙群的岩性多样,但主要是超基性-基性岩,说明其与深部岩浆作用密切相关。对岩墙群的地球化学研究可揭示岩浆事件的构造环境、岩浆演化过程以及源区特征。放射性岩墙群的几何学特征有重要的指示意义,其收敛中心被认为是地幔柱的中心位置。岩墙群是古陆重建十分重要的"契合点",对古陆重建研究十分有帮助。类地行星(金星)巨型放射状系统很可能是岩墙群系统,暗示了地球上也存在过这种完整的巨型放射状岩墙群系统。岩墙群对于古陆重建、地幔柱中心的指示、地幔源区示踪、火山机构以及区域岩浆演化的研究都有十分重要的意义,并将对地球科学的发展产生重要影响。  相似文献