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1.
I. Kayane Dr. 《GeoJournal》1980,4(2):173-181
Japan is very rich in active volcanoes, so that the surveillance and prediction of volcanic activities are indespensable in order to protect human life and properties from catastrophic volcanic eruptions. The author intends here to review the volcanic activities in Japan and the history and status quo of the volcanological observation and research by the Japan Meteorological Agency (JMA), universities, etc. for that purpose. Needless to say, in Japan, volcanoes are studied from various view points such as geophysical, geochemical, geological and geographical. However, the observations for the purpose of detecting of reliable premonitory symptoms of volcanic eruptions are mainly based on geophysical and geochemical methods. In this country, there are permanent observatories at 18 active volcanoes, and there are also several mobile teams of volcanologists. It must be noticed that almost all the volcanic activities including very slight volcanic extraordinary phenomena are nowadays detected in Japan, and unexpected eruptions are very scarce, because the information on the actual state of activities of Japanese volcanoes are made public frequently. 相似文献
2.
Dr. A. Suwa 《GeoJournal》1980,4(2):153-159
Japan is very rich in active volcanoes, so that the surveillance and prediction of volcanic activities are indespensable in order to protect human life and properties from catastrophic volcanic eruptions. The author intends here to review the volcanic activities in Japan and the history and status quo of the volcanological observation and research by the Japan Meteorological Agency (JMA), universities, etc. for that purpose. Needless to say, in Japan, volcanoes are studied from various view points such as geophysical, geochemical, geological and geographical. However, the observations for the purpose of detecting of reliable premonitory symptoms of volcanic eruptions are mainly based on geophysical and geochemical methods. In this country, there are permanent observatories at 18 active volcanoes, and there are also several mobile teams of volcanologists. It must be noticed that almost all the volcanic activities including very slight volcanic extraordinary phenomena are nowadays detected in Japan, and unexpected eruptions are very scarce, because the information on the actual state of activities of Japanese volcanoes are made public frequently. 相似文献
3.
As the regions around active volcanoes succumb to large increases in population, particularly in the developing world where most of the high-risk volcanoes are located, the threat posed by eruptions becomes increasingly serious. Improvements in eruption forecasting are critical to combat this situation, for reducing injury and loss of life, and for minimizing the detrimental effects to local economies and to the fabric of society. Better-constrained forecasts are strongly dependent on geophysical and other data gathered during a program of volcano surveillance, and we reveal how, if interpreted in terms of static rock fracturing, analysis of changes in volcanic seismicity and ground deformation may be used to forecast more accurately the onset of eruptive activity. As illustrated by recent events at several volcanoes, studies of previous activity, increased levels of monitoring, and improved training of scientists are also all crucial to improving forecasts of impending eruptions. 相似文献
4.
In order to identify the mud diapirs and mud volcanoes off SW Taiwan, we have examined ∼1500 km long MCS profiles and related marine geophysical data. Our results show ten quasi-linear mud diapirs, oriented NNE–SSW to N–S directions. Thirteen mud volcanoes are identified from the multibeam bathymetric data. These mud volcanoes generally occur on tops of the diapiric structures. Moreover, the active mud flow tracks out of mud volcanoes MV1, MV3 and MV6 are observed through the high backscatter intensity stripes on the sidescan sonar images. The heights of the cone-shaped mud volcanoes range from 65 m to 345 m, and the diameters at base from 680 m to 4100 m. These mud volcanoes have abrupt slopes between 5.3° and 13.6°, implying the mudflow is active and highly viscous. In contrast, the flat crests of mud volcanoes are due to relative lower-viscosity flows. The larger cone-shaped mud volcanoes located at deeper water depths could be related to a longer eruption history. The formation of mud diapirs and volcanoes in the study area are ascribed to the overpressure in sedimentary layers, compressional tectonic forces and gas-bearing fluids. Especially, the gas-bearing fluid plays an important role in enhancing the intrusion after the diapirism as a large amount of gas expulsions is observed. The morphology of the upper Kaoping Slope is mainly controlled by mud diapiric intrusions. 相似文献
5.
《International Geology Review》2012,54(6):661-664
Using geophysical data, we studied the mechanism of deep-seated magmatic and volcanic activity in the region of the island arcs and associated structures. Data on magmatic activity below the volcanic belt of East Kamchatka, obtained during geophysical investigations, mainly during detailed seismological investigations and deep seismic sounding, provide evidence for an association between the volcanoes and the processes in the Pacific Ocean focal layer of earthquakes, and for the accumulation of magmas below the volcanic belt at depths less than 60 km. We found anomalous columnar bodies more than 5 to 7 km across, linking the volcanoes with the focal layer, and a very large concentration of convective heat flow and volatiles in the magma columns feeding the volcanoes. As to the role of different forces in the uprise of magmas into the volcanoes, hydrostatic forces probably predominate in the asthenosphere, supplemented by tectonic pressure in the lithosphere and forces associated with boiling of magmas during release of volatiles in the crust, especially in its upper layers.—Author. 相似文献
6.
Liquefied vs stratified sediment mobilization processes: Insight from the South of the Barbados accretionary prism 总被引：3，自引：1，他引：3
Eric Deville Sophie-Hlne Guerlais Yannick Callec Roger Griboulard Pascale Huyghe Siegfried Lallemant Alain Mascle Mark Noble Julien Schmitz the collaboration of the Caramba working group 《Tectonophysics》2006,428(1-4):33-47
This paper discusses the nature and origin of subsurface sediment mobilization processes in deep marine clay-rich environments. In the studied area of the southern Barbados accretionary prism, new geophysical acquisitions have emphasized the spectacular widespread development of mud volcanoes that are well-developed along ramp anticlines and along sigmoidal rises with trends that are oblique to the axes of the main folds of the accretionary wedge. On some active mud volcanoes, heat-flow measurements show high positive anomalies related to high fluxes of mud transfer. The mobilized solid fraction expelled by the mud volcanoes does not originate from a unique source bed but from various formations pierced by the mud conduits and is driven by the water phase. The area studied also exhibits trends of structures corresponding to sub-circular massive local uplifts of deformed but well-preserved stratified sediments (turbidites and hemipelagics). No piercing shale diapirs have been encountered in this area. Some of these local uplift structures are complicated by the development of collapses, calderas, and superimposed mud volcanoes. Mud volcanism corresponds fundamentally to fluid displacement (water and gas), whereas massive sedimentary uplift corresponds to large vertical displacements of stratified solid levels but for which the deep cause could be partly the intrusion of mud plugs. Both are dynamic phenomena controlled by the development of overpressure at depth, contributing to sedimentary mobilizations. 相似文献
7.
火山学研究有了长足的进步。笔者总结近些年全球火山学研究各个方面的成果,包括对火山基本概念的新的认识、火山机构、火山的各种分类、火山岩石学和地球化学、火山岩相学、评估火山爆发大小的火山爆发指数、岩石和地球化学分类、各种常量和微量元素区分图、活火山分布与板块构造理论的关系、活火山给人类带来的灾害与利益和活火山的监测、曾经的火山活动与生物毁灭、单成因火山研究等。火山—构造是未来火山学研究的一个方向,通过火山与构造关系的研究以揭示火山的分布和地球的演化。火山喷出的岩浆是其通过地下以岩墙或管道形式为通道运移到地表的结果。中朝边境上的长白山的位置是个特例,应当值得深入的研究。中国分布有许多新生代火山,它们是否为单成因火山、这些火山在成分上是否有演化规律、它们的分布与大地构造的关系等都有待深入和系统的研究。 相似文献
8.
Analysis of radial, centripetal and gutter drainage in the volcanic region of northern Viti Levu, Fiji, enabled the delineation of several distinct volcanoes, despite the early Pliocene age and considerable later erosion. Three main shields with calderas and several smaller volcanoes are mapped. The results are consistent with some other geological and geophysical facts, but do not support the idea that these volcanoes were dominantly submarine eruptions. The method picks out known centres of gold mineralisation and may be applicable, in conjunction with other techniques, in mineral exploration. 相似文献
9.
Newly discovered mud volcanoes in the Coastal Belt of Makran,Pakistan—tectonic implications 总被引：1，自引：1，他引：0
Akhtar M. Kassi Shuhab D. Khan Huseyin Bayraktar Aimal K. Kasi 《Arabian Journal of Geosciences》2014,7(11):4899-4909
The Makran accretionary wedge has a much larger number of mud volcanoes then those reported earlier. Using high-resolution satellite images, over 70 active mud volcanoes were identified. These mud volcanoes occur within a well-defined zone; we call it the Makran zone of active mud volcanoes (MZAMV), which is parallel to the regional trend of the accretionary wedge. Mud volcanoes within the zone occur as clusters, which form linear belts parallel to the regional thrusts associated with anticlines. The MZAMV zone also includes the offshore mud volcanoes occurring in the shallow shelf area, including the recurrently emerging mud islands. Several occurrences of thick deposits of old mud volcanoes (Pleistocene or even older) are also present within this zone, which also display recognizable features that are characteristic of the fossil mud volcanoes. We propose that the MZAMV developed and evolved in response to the continued compression within the Makran accretionary wedge, which in turn, is a response of the subduction process. Mud diapirism has been an ongoing phenomena since Pleistocene or even earlier. The events of enhanced mud extrusion in mud volcanoes and/or emergence of island(s) have relevance with seismic phenomena and, therefore, may be closely monitored. 相似文献
10.
D.A. Budd V.R. Troll D.R. Hilton C. Freda E.M. Jolis S.A. Halldorsson 《Geology Today》2012,28(2):64-70
The Indonesian island of Sumatra, located in one of the most active zones of the Pacific Ring of Fire, is characterized by a chain of subduction‐zone volcanoes which extend the entire length of the island. As a group of volcanic geochemists, we embarked upon a five‐week sampling expedition to these exotic, remote, and in part explosive volcanoes (SAGE 2010; Sumatran Arc Geochemical Expedition). We set out to collect rock and gas samples from 17 volcanic centres from the Sumatran segment of the Sunda arc system, with the aim of obtaining a regionally significant sample set that will allow quantification of the respective roles of mantle versus crustal sources to magma genesis along the strike of the arc. Here we document our geological journey through Sumatra's unpredictable terrain, including the many challenges faced when working on active volcanoes in pristine tropical climes. 相似文献
11.
基于地下电性结构探讨中国东北活动火山形成机制 总被引：14，自引：2，他引：14
东北地区是我国现代火山活动最强烈的地区之一，也是许多学者十分关注的地区。本文回顾了前人提出的关于该地区火山成因的研究成果；通过分析在东北活动火山区大地电磁观测研究的地壳上地幔结构和采用大地电磁网观测研究的地幔1000km以上的电性结构成果，发现长白山天池火山区存在地壳岩浆囊，其它活动火山没有发现地壳岩浆囊，但都存在通往地幔的岩浆通道；东北地区在80～120km左右和200～250km可能存在与地幔岩浆囊相关的地幔高温流体。基于电性结构的研究成果，作者提出了一种东北地区可能的活动火山成因假说。认为东北火山的成因可能与西太平洋板块俯冲到中国东北地区的地幔过渡带后产生脱水有密切关系。这种水以矿物组分或流体方式向上运移，在地幔200-250km和80～120km左右聚集，80～120km的聚集区可能是火山喷发的物质来源。 相似文献
12.
我国从20世纪90年代起开展了活动火山的监测与研究,21世纪初以来开展了中国部分第四纪火山区的活动火山调查工作。本文概述了最近几年我国在活动火山地质学、年代学和岩石地球化学研究方面的新进展。 相似文献
13.
《Earth》2007,80(1-2):1-46
Information on the physical and chemical properties of the lithosphere–asthenosphere system (LAS) can be obtained by geophysical investigation and by studies of petrology–geochemistry of magmatic rocks and entrained xenoliths. Integration of petrological and geophysical studies is particularly useful in geodynamically complex areas characterised by abundant and compositionally variable young magmatism, such as in the Tyrrhenian Sea and surroundings.A thin crust, less than 10 km, overlying a soft mantle (where partial melting can reach about 10%) is observed for Magnaghi, Vavilov and Marsili, which belong to the Central Tyrrhenian Sea backarc volcanism where subalkaline rocks dominate. Similar characteristics are seen for the uppermost crust of Ischia. A crust about 20 km thick is observed for the majority of the continental volcanoes, including Amiata–Vulsini, Roccamonfina, Phlegraean Fields–Vesuvius, Vulture, Stromboli, Vulcano–Lipari, Etna and Ustica. A thicker crust is present at Albani – about 25 km – and at Cimino–Vico–Sabatini — about 30 km. The structure of the upper mantle, in contrast, shows striking differences among various volcanic provinces.Volcanoes of the Roman region (Vulsini–Sabatini–Alban Hills) sit over an upper mantle characterised by Vs mostly ranging from about 4.2 to 4.4 km/s. At the Alban Hills, however, slightly lower Vs values of about 4.1 km/s are detected between 60 and 120 km of depth. This parallels the similar and rather homogeneous compositional features of the Roman volcanoes, whereas the lower Vs values detected at the Alban Hills may reflect the occurrence of small amounts of melts within the mantle, in agreement with the younger age of this volcano.The axial zone of the Apennines, where ultrapotassic kamafugitic volcanoes are present, has a mantle structure with high-velocity lid (Vs ∼ 4.5 km/s) occurring at the base of a 40-km-thick crust. Beneath the Campanian volcanoes of Vesuvius and Phlegraean Fields, the mantle structure shows a rigid body dipping westward, a feature that continues southward, up to the eastern Aeolian arc. In contrast, at Ischia the upper mantle contains a shallow low-velocity layer (Vs = 3.5–4.0 km/s) just beneath a thin but complex crust. The western Aeolian arc and Ustica sit over an upper mantle with Vs ∼ 4.2–4.4 km/s, although a rigid layer (Vs = 4.55 km/s) from about 80 to 150 km occurs beneath the western Aeolian arc. In Sardinia, no significant differences in the LAS structure are detected from north to south.The petrological–geochemical signatures of Italian volcanoes show strong variations that allow us to distinguish several magmatic provinces. These often coincide with mantle sectors identified by Vs tomography. For instance, the Roman volcanoes show remarkable similar petrological and geochemical characteristics, mirroring similar structure of the LAS. The structure and geochemical-isotopic composition of the upper mantle change significantly when we move to the Stromboli–Campanian volcanoes. The geochemical signatures of Ischia and Procida volcanoes are similar to other Campanian centres, but Sr–Pb isotopic ratios are lower marking a transition to the backarc mantle of the Central Tyrrhenian Sea. The structural variations from Stromboli to the central (Vulcano and Lipari) and western Aeolian arc are accompanied by strong variations of geochemical signatures, such as a decrease of Sr-isotope ratios and an increase of Nd-, Pb-isotope and LILE/HFSE ratios. The dominance of mafic subalkaline magmatism in the Tyrrhenian Sea basin denotes large degrees of partial melting, well in agreement with the soft characteristics of the uppermost mantle in this area. In contrast, striking isotopic differences of Plio-Quaternary volcanic rocks from southern to northern Sardinia does not find a match in the LAS geophysical characteristics.The combination of petrological and geophysical constraints allows us to propose a 3D schematic geodynamic model of the Tyrrhenian basin and bordering volcanic areas, including the subduction of the Ionian–Adria lithosphere in the southern Tyrrhenian Sea, and to place constraints on the geodynamic evolution of the whole region. 相似文献
14.
活火山是指1万年来有过喷发历史的全新世火山。火山的高分辨年代学对火山灾害评估和火山分类具有重要意义。对于缺乏历史记载的全新世火山,直接对火山岩进行同位素定年很困难。本文利用具有高时间分辨率的镭-钍-铀非平衡确定中国东部年轻火山的年龄。根据镭-钍-铀同位素,海南岛的马鞍岭和雷虎岭是全新世火山(马鞍岭:4.3ka;雷虎岭:4.7ka);镜泊湖火山(4.9ka)也是全新世火山;龙岗火山存在晚更新世和全新世活动(7.0ka,15.0ka);大兴安岭阿尔山和诺敏河Ra/Th非平衡消失但~(230)Th/~(238)U非平衡显著,属于晚更新世喷发(阿尔山:63ka;诺敏河:71ka)。海南岛的马鞍岭火山、雷虎岭火山和东北地区的龙岗火山、镜泊湖火山,是4座活火山。至于东北地区的阿尔山和诺敏河火山是否是活火山,有待测试更多样品的Ra/Th同位素。五大连池老黑山和火烧山有历史喷发记录,这与它们都存在显著Ra/Th非平衡一致。五大连池老黑山和火烧山的岩浆滞留年龄分别小于4.2ka和3.2ka,岩浆上升速率 18～23m/y。 相似文献
15.
在开展城市活动断层探测工作时,奥维地图可有效提高地质地貌调查、地球物理勘探、钻探等野外工作及数据管理的效率。在地质地貌调查中可对地质调查点进行记录描述、查看宏观地貌特征、定位及导航等;地球物理勘探中可借助卫星影像进行测线设计、测线信息记录等;钻探中可用于钻孔编录信息的保存。奥维提供了备注模版功能,用户可自定义备注格式及内容用于记录各种信息。可将地质调查点、物探测线、钻孔等叠加于Google卫星图之上进行展示,分类管理城市活动断层探测野外调查数据。 相似文献
16.
Cindy Mora-Stock Martin Thorwart Tina Wunderlich Stefan Bredemeyer Thor H. Hansteen Wolfgang Rabbel 《International Journal of Earth Sciences》2014,103(7):2015-2028
Llaima and Villarrica are two of the most active volcanoes in the Chilean Southern Volcanic Zone and presently show contrasting types of activity. Llaima is a closed vent edifice with fumarolic activity, while Villarrica has an open vent with a lava lake, continuous degassing and tremor activity. This study is focused on characterizing the relationships between volcanic and seismic activity in the months before and after the 2010 M8.8 Maule earthquake, which was located in NNW direction from the volcanoes. Time series for tremors, long-period and volcano-tectonic events were obtained from the catalogue of the Volcanic Observatory of the Southern Andes (OVDAS) and from the SFB 574 temporary volcanic network. An increase in the amount of tremor activity, long-period events and degassing rates was observed at Villarrica weeks before the mainshock and continued at a high level also after it. This increase in activity is interpreted to be caused by enhanced magma influx at depth and may be unrelated to the Maule event. In Llaima, an increase in the volcano-tectonic activity was observed directly after the earthquake. The simultaneous post-earthquake activity at both volcanoes is consistent with a structural adjustment response. Since this enhanced activity lasted for more than a year, we suggest that it is related to a medium-term change in the static stress. Thus, the Maule earthquake may have affected both volcanoes, but did not trigger eruptions, from which we assume that none of the volcanoes were in a critical state. 相似文献
17.
《International Geology Review》2012,54(2):170-177
Reinterpretation, using methods developed by the authors, of three seismic sounding-correlation refraction profiles that pass under active volcanoes of Kamchatka clearly show zones of reduced seismic velocity, 0.4-0.5 km/sec lower than the surrounding rock. The deeper zones, at about 8 km, appear to represent primary magma chambers that feed clusters of volcanoes and the shallower zones, secondary magma chambers that feed individual volcanoes. 相似文献
18.
大功率激电在吉林某铜矿新一轮找矿中的应用 总被引：9，自引：0，他引：9
以电法勘探理论为基础,介绍了运用大功率激电方法在吉林通化二密铜矿新一轮找矿中发现新矿体的工作过程,指出在新的成矿理论指导下,充分研究工作区地质、地球物理条件,恰当地选用物探方法,合理进行工作部署,一定能够取得好的找矿效果。 相似文献
19.
Paul T. Robinson Department of Earth Sciences Dalhousie University Canada 《Continental Dynamics》2000,(1)
1. Introduction to surface processesThe shape or morphology of Earth's surface is basically the result of the interplay between two competing forces - mountain building and erosion. Tectonic forces, driven by thermal energy from Earth's interior, cause the rocks of the crust to be folded, faulted and uplifted into high plateaus and mountain belts. As soon as uplift begins, the processes of erosion, driven by gravity, start to wear away the rocks. Masses of weathered rock move downhill under t… 相似文献
20.
南海北部深水区油气勘探的关键地质问题 总被引：1，自引：0，他引：1
南海北部深水区已经获得了重大的天然气发现,正逐渐成为全球深水勘探的热点区之一。通过与相邻陆架区以及世界上典型深水盆地的类比发现,南海北部深水区具有独特的石油地质特征。南海北部大陆边缘经历了从燕山期主动陆缘向新生代边缘海被动陆缘的转变,其演化过程和成盆机制复杂;陆坡深水区具“热盆”特征,凹陷普遍发育超压,其生烃机制不明;深水区距离物源区较远,缺乏世界级大河系的注入,具远源沉积特征,未发现盐层及其相关构造,其油气成藏条件具有特殊性。此外,南海北部深水区海底地形崎岖、多火山,还面临着地震采集、处理等地球物理难题。因此,南海北部深水油气勘探需要在借鉴相邻陆架区和世界其他深水区成功经验的基础上,一方面深入研究其独特的油气地质特征,另一方面研发适应于我国深水环境的地球物理新技术,切实推动深水勘探的进程。 相似文献