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利用布设于兴蒙造山带诺敏河火山群地区的宽频带流动地震台站资料,基于接收函数方法,获取了该地区的地壳厚度与波速比值.研究结果显示,该地区的地壳厚度介于32~38 km,莫霍面深度在空间上分布特征与五大连池为中心的火山带分布具有较好的一致性：沿着火山带延展方向地壳较薄.该地区的波速比介于1.74~1.84,波速比在空间上与地壳厚度变化具有一致性：高波速比主要集中于靠近五大连池火山带地区,向诺敏河火山和小古里河火山延展.研究认为：诺敏河火山与五大连池火山带可能具有相同的岩浆来源,可能与富钾岩石圈地幔拆沉作用造成的地幔热物质上涌有关.研究区地壳厚度与波速比呈现负相关关系,暗示该地区可能发生过岩浆底侵作用. 相似文献
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腾冲是青藏高原东南缘重要的第四纪火山活动区域,全新世以来的火山主要集中在腾冲盆地的中央,由北向南形成一个串珠状的火山链.为了深入探索这一火山区的深部结构和岩浆活动特征,我们在腾冲北部开展了为期一年的流动地震观测,利用接收函数方法计算了台站下方的地壳厚度、平均波速比和泊松比,研究结果揭示出测线下方地壳结构与岩浆活动及火山分布的对应关系.测线北部7个台站的地壳厚度在35.4~37.6 km之间,平均波速比为1.82~1.92、泊松比为0.28~0.31,其中马站附近莫霍面抬升幅度最大,与相邻地区莫霍面深度相差1~2 km,平均波速比和泊松比也达到最大值.相比之下,测线南端两个台站的地壳厚度接近40 km,平均波速比和泊松比仅为1.61~1.64和0.18~0.20,与测线北部7个台站的地壳结构相差甚大.分析表明地幔上涌对火山区莫霍面的局部抬升产生了一定影响,火山湖、黑空山、大-小空山和打鹰山下方应该存在一个相互联通的壳内岩浆囊.该岩浆囊在南北方向上的尺度约为20 km,热流活动以及幔源物质的侵入是地壳平均波速比和泊松比偏高的主要原因,它与热海附近的地温异常区分属两个不同的壳内岩浆存储系统. 相似文献
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滇西地区壳幔解耦与腾冲火山区岩浆活动的深部构造研究 总被引：4，自引：0，他引：4
根据青藏东部边缘的深部地球物理资料,分析了滇西地区壳幔耦合和腾冲火山区岩浆活动的深部构造特征,确认了地幔各向异性与上地幔速度结构(包括P波速度和S波速度)的内在联系,指出产生这一结果的原因与以腾冲火山区为中心的地幔热物质上涌有关:上地幔顶部平均温度升高导致介质强度降低,在印支块体的侧向挤压或印缅块体的向东俯冲作用下发生韧性变形,造成滇西地区地幔各向异性的快波方向与青藏东部地壳块体的旋转方向不一致.此外,鉴于中下地壳低速层的横向非均匀性,估计韧性流动并非贯通青藏高原的东部边缘,而是被不同的构造块体和边界断裂限定在局部地区.总体而言,滇西地区下地壳的地震波速度和电阻率偏低,具备发生韧性变形的构造条件.作为地壳和上地幔之间的解耦层,它使得青藏东部地壳块体旋转产生的构造应力未能传输至上地幔.腾冲火山区的地壳结构与不同时期的岩浆活动有关,火山区东侧的高速结构代表了上新世时期火山通道内冷凝固结的岩浆侵入体或难以挥发的高密度残留物质,火山区西侧的低速结构反映了更新世以来持续至今的岩浆活动,壳内岩浆源主要分布在10～20km的深度范围内,横向尺度约为15～20km,有可能通过地壳深部的断裂与上地幔岩浆源区相连,估计腾冲火山区下方的岩浆活动将持续进行. 相似文献
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利用架设在我国东北地区阿尔山火山区的宽频带流动地震台站记录的远震波形数据,采用P波接收函数H-κ叠加扫描方法,得到了阿尔山火山区的地壳厚度和平均波速比。结果显示:阿尔山地区的地壳厚度范围为33.9—37.9 km,整体呈西北厚东南薄的特点,火山带附近地壳较薄;地壳平均波速比范围为1.73—1.83,主要有柴河镇—明水河镇、伊敏德仁北部和天池镇三处高波速比区。结合前人研究结果推断, 阿尔山火山区薄的地壳和高波速比值可能是由地幔物质上涌、玄武岩浆底侵下地壳所致。 相似文献
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对长白-敦化深地震测深剖面资料利用二维射线追踪程序包进行走时拟合及地震图计算,得到了长白山天池火山区及邻近地区地壳上地幔速度结构和深部构造. 结果表明,以C2界面为标志,研究区地壳可分为上部地壳和下部地壳. 上部地壳厚1-23km,P波速度为6.00-6.25km/s;下部地壳厚12-17km,它是由一个较均匀的速度层和一个厚6-km的壳幔过渡层构成. 地壳厚度由敦化一带31-33km向东南逐渐增厚,至天池火山区最深达3km. 在天池火山区地壳存在低速体,其速度较周围介质低约为0.15km/s. 利用地震剖面探测、地震CT和大地电磁测深等结果显示,在天池火山区地壳内存在低速、低密度及低阻异常体,该异常体可能表明壳内岩浆囊的存在. 相似文献
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Introduction The Tengchong volcanic-geothermal area is located on the northeast edge of the collision zone between Indian and Eurasian plates, and belongs to Eurasian volcanic zone (the MediterraneanHimalayanSoutheast Asia volcanic zone). In Tengchong area, the Quaternary volcanic, geothermal and seismic activities are all intensive. These phenomena have been drawing the attention of many geoscientists in the world. Their studies are concerned with geology, geophysics, geochemistry, and cr… 相似文献
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Deep seismic sounding investigation into the deep structure of the magma system in Changbaishan-Tianchi volcanic region 总被引：6，自引：0，他引：6
IntroductionThe Changbaishan-Tianchi volcano, located in Jilin Province, northeast of China, is one of the well-known active volcanoes in China. In the year 1 215(15, the volcano underwent an eruption that is believed to be one of the greatest explosive eruptions on earth in the past 2000 years with regard to its scale and violence. The eruption amounted to over 100 km3, and the eruption cylinder reached a height of more than 30 km, the volcanic ashes floated and fell south of Hokkaido, Jap… 相似文献
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The Yellowstone volcano is one of the largest active volcanoes in the world, and its potential hazards demand detailed seismological and geodetic studies. Previous studies with travel time tomography and receiver functions have revealed a low-velocity layer in the crust beneath the Yellowstone volcano, suggesting the presence of a magma chamber at depth. We use ambient seismic noise from regional seismic stations to retrieve short-period surface waves and then study the shallow shear velocity structure of the Yellowstone region by surface wave dispersion analysis. We first obtained a crustal model of the area outside of the Yellowstone volcano and then constructed an absolute shear wave velocity structure in combination with receiver function results for the crust beneath the Yellowstone volcano. The velocity model shows a low-velocity layer with shear velocity at around 1.3 km/s, suggesting that a large-scale magma chamber exists at shallow levels within the crust of the Yellowstone volcanic region. 相似文献
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Robert W. Decker 《Bulletin of Volcanology》1965,28(1):231-256
Active volcanoes occur in at least two fundamentally different tectonic settings. Taphrogenic volcanoes are aligned along the mid-ocean fracture system which is characterized by a broad ridge of rugged relief, «tensional» horizontal stress components perpendicular to the ridge, shallow earthquakes in a zone vertically beneath the ridge crest, thin to normal occanic crust and low to normal seismic velocities in the uppermost mantle, positive free-air gravity anomalies, and high heat flow. Orogenic volcanoes are aligned along the mobile Pacific rim and Indonesian archipelago which are characterized by double or single arcuate ridges with a deep oceanic trench on the convex side, compressional horizontal stress components perpendicular to the arcs, shallow to deep earthquakes in a zone dipping from the trench to beneath the volcanoes and beyond, transitional crustal thicknesses and seismic velocities, parallel belts of negative and positive free-air gravity anomalies from the trench to the volcanic arc, and low heat flow from the trench. The diverse nature of most geophysical lineaments associated with volcanism suggests that magma generation is independent of these phenomena. The remaining correlation of shallow earthquakes with taphrogenic volcanocs and intermediate depth earthquakes with orogenic volcanoes suggests that active fracture systems reaching these depths can tap latent magma sources. Seismic evidence for a low velocity layer beginning 100 km beneath continents and 60 km beneath oceans gives independent support to this hypothesis. 相似文献
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利用加拿大凤凰公司在夏威夷大岛地区布设的长期大地电磁观测台站,选取2018年5月至2019年4月的观测数据,反演并获得了该台站下方大岛深部的电性构造及其随时间变化的特征,并将反演结果与前人探测结果进行对比。研究结果表明:在观测点下方2—3 km处存在一个明显的低阻薄层,电阻率大约为20 Ω·m,推测其可能是地表浅部发育的岩浆囊;100 km深处电阻率变化范围在20—70 Ω·m,推测该深度下可能为活跃的复杂岩浆储层,反演结果与前人在邻近地区的探测结果具有可比性。 相似文献
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《震灾防御技术》2022,17(4):710-718
吉林龙岗火山区是第四纪活动火山,具有潜在喷发危险。通过GNSS和水准资料分析区域三维地壳运动,得出2011—2019年相对欧亚板块水平运动以东南向为主,速度＜10 mm/a。敦化-密山断裂以东受日本2011年“3·11地震”影响强烈,现以拉张运动为主;近年来水准资料揭示火山区垂直运动以隆升为主。2014—2019年的InSAR资料显示隆升集中在靖宇一带。结合MT剖面反演得到的深部电性结构,龙岗火山区西侧高阻体分布在深度18 km以上,金龙顶子火山下方最浅。中部为早期喷发形成的火山,下方高阻体分布在深度40 km以上,东侧抚松一带分布在深度约20 km以上,地壳范围内的高阻结构表明岩浆已固结。高阻结构层可分辨出断层两侧电阻的差异性。高阻体下方存在大规模低阻结构,推测为中下地壳岩浆系统。金龙顶子火山深度10 km以下的低阻结构可能为岩浆通道,并与中下地壳岩浆系统相连。东侧区域岩浆平均深度约30 km,相对较浅。龙岗火山区幔源物质的上涌及间断性的向上运移引起地壳隆升及地震活动。 相似文献
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沿盈江一姚安布置了一条长约350 km的长周期大地电磁剖面,共观测宽频大地电磁测深点53个,长周期大地电磁测深点26个;利用多种数据处理方法对观测资料进行了预处理、定性分析和二维反演,得到沿剖面的地壳和上地幔电性结构模型.对主要地块和断裂带的电性结构进行了分析,电性结构模型揭示滇西三江地区广泛存在壳内低阻层,但沿剖面方向即东西向埋深和厚度不一,在保山地块和滇中地块地下存在较大规模的壳幔低阻带;腾冲地块地下埋深13~20 km,厚约10~17 km的壳内低阻层可能是岩浆囊的反映;初步将保山壳幔韧性剪切带作为印支地块挤出的深部东边界. 相似文献
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DEEP “ARCH-BRIDGE” MAGMATIC SYSTEM OF THE AERSHAN VOLCANIC GROUP AND ITS STABILITY ANALYSIS 
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下载免费PDF全文 The Aershan volcanic group has been active since the Pleistocene to the modern and has potential to erupt, so it is of great significance to strengthen the study on the Aershan volcano group and evaluate its activity. The magmatism is characterized by low resistivity in electrical properties. The electrical structure obtained by magnetotelluric sounding can be used to study the magmatic occurrence and volcanic activity. It is an effective method to detect the deep structure of volcanic area. Based on the magnetotelluric sounding data of the Aershan volcanic group, the two-dimensional nonlinear conjugate gradient inversion is obtained after the normalization of the data and the two-dimensional electrical structure of the Aershan volcanic group is obtained. It is found that there is a large-scale "arch-bridge" low-resistivity anomaly (resistivity less than 320Ω·m) and there are obvious high-conductivity anomalies (resistivity less than 40Ω·m) respectively on the west of the town of Ershi and the east of Chaihe town, the former is relatively small in sizes, buried at the depth of 40~60km, and the size of the latter is larger, buried at the depth of 60~90km, or even deeper. Combined with geological and geochemical data, it is inferred that the "arch bridge" anomaly is the channel of the basaltic magma transport from the epithermal basins on its both sides. The two high-conductivity anomalies it contains are probably the uncondensed or gathering magma chamber, so the Aershan magma system consists of "arch bridge" channel and asthenosphere-derived basaltic magma, the volcanic group has a unified magmatic system. Further analysis shows that the melting percentage of the "arch bridge" channel material is not less than 0.5%, and the lithosphere structure tends to be stable. The melting degree of the two magma chambers it contains is 2.5%~11.5%, and the grain boundary may all be wetted by the melt, rock flow intensity is relatively low, lithosphere structural stability is poor. In addition, the regional seismic distribution and the formation of hot springs also have a certain correlation to the Aershan volcanic group magma system. There are indications that the Aershan volcano group is in dormancy, rather than an extinct volcano, there is the possibility of eruption, so it should be closely monitored. 相似文献
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利用流动台网和固定台站的地震观测数据,采用有限差分层析成像方法反演了腾冲及邻近地区的地壳P波速度结构,分析了腾冲火山区的岩浆活动和龙陵七级地震的深部构造成因.研究结果表明,腾冲火山区的地壳结构具有明显的非均匀性,浅表层偏低的速度主要为盆地内部的松散沉积层、新生代火山堆积及断裂附近的流体裂隙和热泉活动所致;5～15 km之间的高速体可能代表了早期火山通道内冷却固结的岩浆侵入体或难挥发的超铁镁质残留体;地壳深部的低速体则反映了熔融或半熔融的岩浆体,推断火山区下方的岩浆活动与龙陵七级地震震源区地壳深部的岩浆侵入来自同一源区--现今壳内岩浆活动的主要区域.龙陵震源区的地壳速度结构横向变化较大,怒江断裂东侧和龙陵断裂西侧为高速特征,介质应变强度较大,为应力积累的主要载体;两断裂之间的低速区向下延伸至下地壳,可能与地壳深部的岩浆侵入有关;龙陵断裂和怒江断裂明显控制了这一区域的岩浆活动,七级地震正是发生在断裂下方的速度边界附近.地壳介质强度的横向变化导致了震源区应力积累的不均一性,深部岩浆的聚集和动力作用是龙陵地区发生强震的主要原因. 相似文献
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海南岛曾发生1605年琼山7.5级大震,现今小震多分布在东北缘的南北向地震条带及九所—陵水断裂中东段,马鞍岭—雷虎岭火山群具有潜在喷发危险.新构造运动包括垂直与水平运动.本文采用2009—2014年多期GNSS观测资料及1970 s、1990 s、2013年精密水准资料揭示现今地壳运动特征及断裂活动性,结果表明水平运动以SEE向为主,与华南地块运动一致;南北向小震条带附近以左旋拉张为主,基线变化表明运动具间歇性.岛北部垂直运动在1970 s表现为以海口—屯昌为界的东升西降,以王五—文教断裂为界的南北两侧分段性差异运动.1970 s—1990 s年环岛水准资料揭示相对秀英港水准基点,点位以上升运动为主,且西南相对东北上升,地壳以继承性运动为主.其中琼北垂直运动与1970 s相反.1990 s—2013年资料揭示点位运动趋势与上一时段相反,主要为文昌—琼海—万宁一带上升和其他测点的相对下沉.由形变及地球物理等研究结果推测东北缘小震由铺前—博鳌断裂活动引起.马袅—铺前断裂以北盘下降为主;九所—陵水断裂东段活动大于西段.地震、形变等资料表明现今火山活动平静. 相似文献
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使用云南腾冲火山监测台网9个宽频带地震台站的远震数据,采用P波和S波接收函数的方法研究了腾冲火山区的地壳厚度、泊松比值以及岩石圈和软流圈分界面(LAB)深度.研究结果表明:1)云南腾冲火山区的地壳厚度约在33.5~38.0km之间;2)火山区的泊松比主要集中范围为0.26~0.32,其中6个台站均大于0.29,推测与地壳镁铁质成分的增加有关并且可能存有2个岩浆囊;3)火山区的岩石圈厚度在78.2~88.0km,较周边地区明显隆起且横向差异较大.腾冲火山区岩石圈的明显穹隆,由软流圈上涌(地幔热物质上升)引起岩石圈的拉张与减薄所致. 相似文献