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1.
华南东部地区上地幔P波速度结构研究 总被引：1，自引：0，他引：1
基于华南东部宽频地震流动台阵的观测资料,采用三维有限差分走时成像法(FDtomo),开展了华南东部地区地壳-上地幔三维P波速度结构成像研究,结果显示华南东部地区水平面内速度分布差异较大,约163 km以上的地壳到上地幔下扬子地块存在近EW向的相对低速异常,而华夏地块则为高速异常,约163 km以下的上地幔下扬子地块和华夏板块速度异常发生反转,且两者大致以江山—绍兴断裂带为界呈反对称,对比显著。笔者认为该结构特征反映了晚中生代扬子克拉通岩石圈的拆沉过程。这一成果对理解中国东部中生代以来的构造演化以及壳幔的动力学过程提供了新的证据。 相似文献
2.
了解华南各岩石圈块体壳幔结构和各向异性方面的差异是揭示华南深部构造演化的基础。本文利用布设于华南的两条宽频地震测线观测数据,采用多种地震学方法对华南的地壳上地幔结构和各向异性进行了研究。接收函数结果表明,华南地区地壳厚度和岩石圈厚度都较薄,地壳厚度自东南沿海向西北内陆增厚,扬子克拉通的泊松比(波速比)低于华夏块体,表明扬子克拉通地壳较华夏块体更偏长英质。约北纬29°以北的扬子克拉通地幔转换带厚度明显增厚,可能是由地幔转换带底部停滞的冷的古太平洋板片或中生代克拉通碰撞残留造成的。层析成像结果显示华南上地幔具有很强的横向差异性,上地幔中的强烈低速异常体可能对应了晚中生代发生广泛岩浆作用时的岩浆房和岩浆通道。台湾下方的上地幔存在南北横向差异明显的高速异常,分别对应台湾南部向东俯冲的欧亚板块及台湾北部向北俯冲的菲律宾海板块。俯冲的欧亚板块在台湾南部是连续的,而在台湾中北部,由于与菲律宾海板块的相互作用,俯冲的欧亚板块被折断。剪切波分裂结果显示,以江绍断裂为界,华夏块体与扬子克拉通的岩石圈地幔各向异性存在明显的横向变化,表明两者的构造演化过程有显著差异。 相似文献
3.
华南大陆主要由扬子与华夏两大古陆块拼合而成,复杂的构造演化过程使得该区不仅具有多样的几何结构与变形特征,也发育成为中国南部重要的多金属成矿区域,其中包括长江中下游、钦州—杭州、武夷山、南岭、等多个重要成矿带。针对华南东南部及位于该区内的长江中下游、武夷山和南岭成矿带的深部结构与成矿背景,本文利用国家地震台网在该区固定地震台站的远震事件记录信息,通过对各个台站的远震接收函数开展H-κ扫描研究,获得了各台站下方的地壳厚度和波速比。对地壳厚度和波速比的相关性与地壳流变学构造模式进行了对比分析,研究结果显示,华南东南部的Moho面起伏整体较为平缓,自东向西逐渐增厚,波速比分布与成矿带和构造格局有明显相关性,在扬子与华夏块体之间的华南陆内复合造山区呈现明显的低波速比特征;结合该区已有的地质构造等研究分析,认为华南地区地壳减薄与燕山期的强烈岩浆活动和成矿过程密切相关,太平洋板块俯冲以及岩石圈和下地壳拆沉所造成的上地幔热物质扰动上涌或是该区矿产资源集中爆发的驱动力源;本研究所得地壳厚度与波速比分布特征与重力学多尺度边缘检测所刻画的构造界限一致性较好,支持其对扬子与华夏块体南界的划分方案。 相似文献
4.
华南地壳及上地幔三维速度结构成像 总被引：2，自引：0，他引：2
利用国家地震科学数据共享中心的地震目录及临时台网资料,挑选出11 113个区域地震的77 093条P波走时和93 541条S波走时,采用1°×1°的经纬度网格划分,反演获得了深至60km的华南南部地区的地壳及上地幔三维P波和S波的速度结构。研究结果表明,纵波速度结构与横波速度结构从整体来看具有较好的一致性,说明该研究获得的深部速度结果具有较高的可信性,但是在50km的深度纵、横波速度结构的一致性较差,可能是由于该深度的纵横波走时数据存在着较大的差异所导致的。本研究显示了研究区域内的速度结构存在着明显的横向不均匀性,东南沿海地区的地壳中出现了大规模的低速异常,可能与该区地幔物质的上涌有关;而在珠江三角洲、雷州半岛、北部湾及海南岛等地区莫霍面下方出现的低速异常,则与该区的热运动有关。经分析认为,华南南部地壳及上地幔的速度不均匀性和华南板块与扬子地块的相互作用有关,因此开展进一步研究能为探索和分析华南再造以及中国南海北部的构造演化提供重要信息。 相似文献
5.
福建地区地壳上地幔S波速度结构与泊松比 总被引：8，自引：0，他引：8
利用在福建地区布置的 12 个宽频带数字地震流动台站和 8 个固定台站记录的远震 P 波波形数据进行接收函数计算,
运用H-k 搜索叠加方法得到了研究区的平均地壳厚度H 与波速比k（=VP/VS）,并运用接收函数反演方法得到了 0~80 km 范
围内的地壳和上地幔 S 波速度结构。H-k 叠加结果表明,福建地区地壳厚度在 28.4~32.8 km 范围内,从内陆到沿海变薄,
从南到北变厚;沿着 NW-SE 方向,泊松比分布有分带特征,沿海地区泊松比高于内陆地区;同时表明,该地区地壳可分
为上、中、下地壳,地壳结构横向差异较明显,多个台站下方可发现壳内低速层,沿海地区上地幔顶部平均速度相对低,
可能暗示了深部存在热异常区域。 相似文献
6.
华南大陆历经长期复杂的构造演化,其浅部复杂而多样的构造形态与深部壳幔结构及其动力学机制有着密切联系,但当前的深部探测资料有限,深部构造并不明确。为了研究华南的深部岩石圈结构状态,布设了多条宽频长周期大地电磁联合探测剖面。通过对景德镇-温州剖面的数据处理,获得了该剖面的岩石圈电性结构模型。分析表明:华夏地块与扬子地块东部的江南造山带以江绍断裂为界;华夏地块整体呈现高阻特征,可能具有深部岩石圈背景的上虞-政和-大浦断裂将其分为华夏褶皱带与东南沿海岩浆岩带;扬子地块东部的江南造山带整体电阻率较低,结构更破碎,受到深部改造明显,岩石圈底界约为110 km;剖面发现3处低阻带通道,可能与软流圈上涌相关;江绍断裂呈喇叭状向深部张开,华夏地块与扬子地块的裂解拼合可能与断裂深部的高导体活动有关。华夏地块与扬子地块的接触状态呈现为双向汇聚,华夏地块在上地幔挤入扬子地块,深部接触边界可能越过江绍断裂带。 相似文献
7.
根据龙门山及其周边地区(26°～35°N,98°～109°E)的132个台站的宽频带远震记录,使用H-k叠加方法计算地壳厚度和波速比.结果表明该区域的地壳厚度总体变化是:从东向西增加,东部的最小厚度为37.8km,西部的最大厚度是68.1 km,其中横跨龙门山断裂带的地壳厚度变化最大,从东南的41.5km增加到西北的52.5km.根据Airy均衡理论,用台站的高程和观测地壳厚度数据求得最小二乘意义下的壳幔密度差为0.649g/cm3,平均地壳厚度为37.9km.龙门山及其邻近地区基本上处于均衡状态.松潘-甘孜地体北部和西秦岭造山带具有低泊松比(v<0.26),扬子地台的西南部具有低一中泊松比(v<0.27),松潘-甘孜地体南部、三江褶皱带和四川盆地具有中一高泊松比(0.26≤P≤0.29).该地区的泊松比空间分布不支持青藏高原东部广泛分布的下地壳流的假说.龙门山断裂带南段及其附近地区的高泊松比(v≥0.30)可以看成是地壳具有较高的铁镁质组分和/或存在部分熔融.该地区下地壳可能是处于富含流体和温度较高的部分熔融状态.松潘-甘孜块体南部的上地壳物质向东运动,受刚性强度较大的扬子地台的阻挡,导致沿龙门山断裂带产生应变积累.当断层被地壳流体弱化,积累的应变能量快速释放,产生汶川Ms8.0地震. 相似文献
8.
中国东南地区地质演化复杂,中—新生代构造变形强烈,岩石圈深部热力学状态及其对构造活动的影响有待深入。文章结合最新的大地热流数据与地壳结构Crust 1.0模型,利用稳态热传导方程,以岩石捕虏体温压数据和地震学观测为约束,构建了华南地区扬子克拉通、华夏地块以及南海北缘等不同单元的岩石圈热结构。结果表明该区岩石圈热结构存在强烈的不均一性：除了上扬子地区（四川盆地）为“温壳温幔”的热结构,华南其他大部分地区都表现为“热壳热幔”的特征;同一深度下,华夏地块与南海北缘的深部温度显著高于扬子克拉通;热岩石圈厚度从克拉通内部向沿海地区（NWSE）逐渐降低,也即由四川盆地的~200 km减少到华夏地块的~110 km,再到南海的~70 km。此外,我们还发现陆内地震的分布与岩石圈温度密切相关,地震活动集中分布于600℃等温线以内。总体而言,扬子克拉通中西部岩石圈热结构具有冷而厚的特征,而华夏地块和南海北缘受古太平洋平板俯冲和新生代大陆边缘构造—岩浆作用的改造,表现为热且薄的特征,岩石圈的热弱化进而加速了华南大陆边缘的裂解及随后的南海扩张过程。 相似文献
9.
为了更好地研究吉林前郭地区的地震活动性,本文利用2013年10月至2015年2月吉林前郭5.8级震群周围17个地震台站记录到的405个地震事件资料,共获得2 218条P波走时数据和2 166条S波走时数据,采用地震双差层析成像技术,获取吉林前郭震区上地壳三维P波、S波速度精细结构。结果显示,震区上地壳速度分层明显,P波速度变化范围为5.8~7.2km/s,S波速度变化范围为3.4~4.0km/s,波速比(vP/vS)变化较小。震区有低速带穿过,低速带走向为北东向,倾角较大(近直立),纵向延伸至15km深度;震群主要位于低P波和S波速度区,对应较低的波速比。吉林前郭震区构造强度较低,受西太平洋板块俯冲产生应力场的影响,易于发生地震。 相似文献
10.
华南陆块受多阶段超大陆聚合、裂解, 碰撞、陆内造山, 及伸展等作用影响, 造成其深部结构和构造极其复杂。岩石圈有效弹性厚度(Te)是表征地质时间尺度上岩石圈力学强度的定量指标, 可为深入认识岩石圈力学结构及演化提供有效约束。本文基于导纳和相关函数联合方法对地壳布格重力异常和地形数据进行计算, 获得华南陆块Te的空间分布。Te高值(>20 km)区域主要分布于扬子地块的四川盆地周边区域, 而Te低值(<20 km)区域集中于华夏地块和江南造山带区域。由于Te分布特征与地热场、地震关系密切。通过分析研究区Te与地热场(地表热流、居里面深度)、地震之间的关系, 本文得到如下认识: (1)Te与地热场参数具有较好的相关性, 但受浅部地壳被破坏, 深部仍为克拉通地壳影响, 导致龙门山断裂带和江南造山带区域的Te与地表热流或居里面深度之间的部分对应关系相反。(2)Te与地震关系复杂, Te较薄区域并不代表着地震频发区域, 地震活动性与其所处的深部环境相关。龙门山断裂带强震频发的原因是受周边两块体中上地壳刚性地层长期相互作用, 致使应力和能量积累较强; 华夏地块区域地震较少是因为深部热物质上涌对华夏地块的壳幔进行强烈改造, 且地壳中存在横向不均匀分布的软弱地层对应力吸收, 造成能量和应力不易积累; 扬子地块的岩石圈力学强度较强是该区较少发生地震的重要原因。 相似文献
11.
We have developed a simple semblance-weighted stacking technique to estimate crustal thickness and average VP/VS ratio using teleseismic receiver functions. We have applied our method to data from 32 broadband seismograph stations that cover a 700 × 400 km2 region of the Grenville orogen, a 1.2–0.98 Ga Himalayan-scale collisional belt in eastern North America. Our seismograph network partly overlaps with Lithoprobe and other crustal refraction surveys. In 8 out of 9 cases where a crustal-refraction profile passes within 30 km of a seismograph station, the two independent crustal thickness estimates agree to within 7%. Our regional crustal-thickness model, constructed using both teleseismic and refraction observations, ranges between 34.0 and 52.4 km. Crustal-thickness trends show a strong correlation with geological belts, but do not correlate with surface topography and are far in excess of relief required to maintain local isostatic equilibrium. The thickest crust (52.4 ± 1.7 km) was found at a station located within the 1.1 Ga mid-continent (failed) rift. The Central Gneiss Belt, which contains rocks exhumed from deep levels of the crust, is characterized by VP/VS ranging from 1.78 to 1.85. In other parts of the Grenville orogen, VP/VS is found to be generally less than 1.80. The thinnest crust (34.5–37.0 km) occurs northeast of the 0.7 Ga Ottawa–Bonnechere graben and correlates with areas of high intraplate seismicity. 相似文献
12.
Crustal transect from the North Atlantic Knipovich Ridge to the Svalbard Margin west of Hornsund 总被引：1，自引：0，他引：1
Frode Ljones Asako Kuwano Rolf Mjelde Asbjrn Breivik Hideki Shimamura Yoshio Murai Yuichi Nishimura 《Tectonophysics》2004,378(1-2):17-41
The crustal structure along a 312 km transect, stretching from the axial mountains of the North Atlantic Knipovich Ridge to the continental shelf of Svalbard, has been obtained using seismic reflection data and wide angle OBS data. The resulting seismic Vp and Vs models are further constrained by a 2-D-gravity model. The principal objective of this study is to describe and resolve the physical and compositional properties of the crust in order to understand the processes and creation of oceanic crust in this extremely slow-spreading counterpart of the North Atlantic Ridge Systems. Vp is estimated to be 3.50–6.05 km/s for the upper oceanic crust (oceanic layer 2), with a marked increase away from the ridge. The measured Vp of 6.55–6.95 km/s for oceanic layer 3A and 7.10–7.25 km/s for layer 3B, both with a Vp/Vs ratio of 1.81, except for slightly higher values at the ridge axis, does not allow a clear distinction between gabbro and mantle-derived peridotite (10–40% serpentized). The thickness of the oceanic crust varies a lot along the transect from the minimum of 5.6 km to a maximum of 8.1 km. The mean thickness of 6.7 km for the oceanic crust is well above the average thickness for slow-spreading ridges (<10 mm/year half-spreading rate). The areas of increased thickness could be explained by large magma production-rates found in the zones of axial highs at the ridge axis, which also have generated the off-axial highs adjacent the ridge. We suggest that these axial and off-axial highs along the ridge control the lithological composition of the oceanic crust. This approach suggests normal gabbroic oceanic crust to be found in the areas bound by the active magma segments (the axial and off-axial highs) and mantle-derived peridotite outside these zone. 相似文献
13.
R. Mjelde T. Raum P. Digranes H. Shimamura H. Shiobara S. Kodaira 《Tectonophysics》2003,369(3-4):175-197
A total of 13 regional Ocean Bottom Seismograph (OBS) profiles with an accumulated length of 2207 km acquired on the Vøring Margin, NE Atlantic have been travel time modelled with regards to S-waves. The Vp/Vs ratios are found to decrease with depth through the Tertiary layers, which is attributed to increased compaction and consolidation of the rocks. The Vp/Vs ratio in the intra-Campanian to mid-Campanian layer (1.75–1.8) in the central Vøring Basin is significantly lower than for the layers above and beneath, suggesting higher sand/shale ratio. This layer was confirmed by drilling to represent a layer of sandstone. This mid-Cretaceous ‘anomaly’ is also present in the northern Vøring Basin, as well as on the southern Lofoten Margin further north. The Vp/Vs ratio in the extrusive rocks on the Vøring Plateau is estimated to be 1.85, conformable with mafic (basaltic) rocks. Landward of the continent/ocean transition (COT), the Vp/Vs ratio in the layer beneath the volcanics is estimated to be 1.67–1.75. These low values suggest that this layer represents sedimentary rocks, and that the sand/shale ratio might be relatively high here. The Vp/Vs ratio in the crystalline basement is estimated to be 1.67–1.75 in the basin and on the landward part of the Vøring Plateau, indicating the presence of granitic/granodioritic continental crust. In the lower crust, the Vp/Vs ratio in the basin decreases uniformly from southwest to northeast, from 1.85–1.9 to 1.68–1.73, suggesting a gradual change from mafic (gabbroic) to felsic (granodioritic) lower crust. Significant (3–5%) azimuthal S-wave anisotropy is observed for several sedimentary layers, as well as in the lower crust. All these observations can be explained by invoking the presence of liquid-filled microcracks aligned vertically along the direction of the present day maximum compressive stress (NW–SE). 相似文献
14.
As a part of the MONTBLEX-90 observational programme, Kytoon and Doppler sodar observations were taken at Kharagpur. These
data are analysed to study the turbulent characteristics of the atmospheric boundary layer in terms of stability, temperature
structure function (C
T
2
) and velocity structure function (C
v
2
).C
T
2
follows aZ
−4/3 law on most of the days, whereas the variation ofC
V
2
is not systematic.C
V
2
andC
T
2
values are found to vary between 10−5−10−1 m4/3s−2 and 10−5−10−2°C2 m−2/3 respectively. 相似文献
15.
Nadia Curetti Davide Levy Alessandro Pavese Gabriella Ivaldi 《Physics and Chemistry of Minerals》2006,32(10):670-678
The elastic properties of coexisting natural 3T and 2M
1 phengite samples (Cima Pal, Sesia Zone; Val Savenca; Western Alps, Italy) with similar chemical compositions have been studied by room temperature–high pressure powder diffraction, using synchrotron radiation on the ID9A beam-line at ESRF (Grenoble, France). The P–V curves have been modelled by the Birch–Murnaghan model; a third-order expansion fitted to the experimental data yields for 3T and 2M
1 K
0=60.4(±0.7) GPa, K′=5.79(±0.11) at V
0=703.8851 Å3, and K
0=57.3(±1.0) GPa, K′=6.97(±0.24) at V
0=938.8815 Å3, respectively. The relative stability of 3T vs. 2M
1 has been explored as a function of pressure and temperature in terms of configuration and deformation contributions to the Gibbs energy, using the elastic properties determined here and other thermodynamic parameters from earlier investigations. The results presented agree with the hypothesis of stability of the 3T polytype in the high pressure regime. 相似文献
16.
Gui Zhen Men 《Mathematical Geology》1991,23(1):71-76
Hundreds of samples and 17 variables collected from coalfields of major coal-bearing strata over China except for Tibet and Taiwan, were used in this study. The dry, ash-free basis volatile matter (V
r) and caking index (G
(RI)) were chosen by means of correlation analysis and stepwise discriminatory analysis as major indices of a new classification. By means of the optimum section, the boundary value of the axis of ordinate (G
(RI)) and axis of abscissas (V
r) can be determined in the classification system. Thus, aV
r –G
(RI) classification scheme diagram was formed and bituminous coal was divided into nine classes. Use of correspondence analysis reduced dimensions of sample-expressive space without losing initial information. The trend on the factor surface of samples shows that the classification obtained from correspondence analysis conforms to theV
r –G
(RI) classification result and further verified the dependability of classification by two indices. At the same time, a certain relationship between the properties of a great variety of coal and their attributes can be explained. Hence, bituminous coal classification becomes more scientific, reasonable, and practical than before. 相似文献
17.
Lithospheric structure of the Tornquist Zone resolved by nonlinear P and S teleseismic tomography along the TOR array 总被引：1，自引：1，他引：1
Z. Hossein Shomali Roland G. Roberts Laust B. Pedersen the TOR Working Group 《Tectonophysics》2006,416(1-4):133
The main aim of the TOR project is to study the lithospheric–asthenospheric boundary structure under the Sorgenfrei–Tornquist Zone, across northern Germany, Denmark and southern Sweden. Relative arrival-time residuals of teleseismic P and S phases from 51 earthquakes, recorded by 150 seismic stations along the TOR array, were used to delineate the transition zone in the studied area. The effects of crustal structures were investigated by correcting the teleseismic residuals for travel-time variations in the crust based on a 3D crustal model derived from other data. The inversion was carried out for S phases. The results were then compared with the corresponding P-wave models. As expected, the derived models show that the relatively old and cold Baltic Shield has higher velocity at depth than the younger lithosphere farther South. The models show two sharp and distinct increases in depth to velocities which are low compared to our reference model, as we move from South to North. The location and sharpness of these boundaries suggests that the features resolved are, at least partially, compositional in origin, presumably related to mantle depletion. A sharp and steep subcrustal boundary is found roughly coincident with the southern edge of Sweden. This is below where the edge of the Baltic Shield is usually placed, based on surface geological evidence (the Sorgenfrei–Tornquist Zone). Another less significant transition is recognised more or less beneath the Elbe-lineament. Relatively high d(Vp / Vs) ratios under the central part of the profile (Denmark) indicate relatively low S-velocity in an area where a gravity high supports the hypothesis of extensive mafic intrusions. 相似文献
18.
Claudio Territo Philippe Vieillard Dominique Righi Sabine Petit Riccardo Scalenghe 《Journal of Geochemical Exploration》2006,88(1-3):345
The aim of this study is to characterize the pedogenic clay minerals by using simple approach: mixing mineralogical and geochemical findings.The fine clay fractions (< 0.1 μm) of a Vertic Cambisol profile were studied by means of X-ray diffraction (XRD), infrared spectroscopy (FTIR) and cation exchange capacity (CEC).Qualitative and quantitative mineralogical compositions of the clay mixture were determined.Moreover, chemical equilibria and thermodynamic stabilities of minerals (calcite, gypsum, kaolinite, smectites and illites) were studied using results of ionic activities obtained from total concentration of various aqueous species in water extracts from soil-saturated pastes.XRD analysis shows a good homogeneity in the mineralogical composition of the soil material, with depth of soil profiles. The identified clay minerals are mainly illite–smectite mixed layers (I/S) and kaolinite. The chemical analysis of saturated paste extracts with clay minerals shows a slight undersaturation of the illitic phase while smectites and also calcite and gypsum reach the thermodynamic equilibrium along the soil profile. 相似文献
19.
20.
P. Pal Roy 《Geotechnical and Geological Engineering》1995,13(2):79-92
Summary This paper substantiates, through three different case studies, that the breakage assessment of opencast bench blasting can be made scientifically through the analysis of joint set orientations of different exposed benches in association with the corresponding face direction. Joint orientations, dip and strike of bedding planes have a significant influence on rock breakage. They can have decelerating effects on blasting performance, which may be rectified by geological mapping, and subsequently modifying the blast design parameters. 相似文献