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1.
莫霍面是地壳和上地幔的分界面,是个重要的密度界面,东海莫霍面的展布特征,对于研究东海深部构造具有重要意义.利用最新重力异常数据反演莫霍面深度,结合前人的莫霍面深度结果,分析东海及其邻域的壳－幔结构与展布特征.从莫霍面深度图可见东海及其邻域莫霍面起伏变化很大,深度在12～34 km之间变化,东海及其邻域地壳厚度为6～34km,东海陆架地区地壳厚度变化与大陆地区相比并不明显,显著减薄开始于冲绳海槽地区,琉球岛弧处地壳厚度明显再度增加,莫霍面呈现两凹两凸形态,认为东海及其邻域地壳自西而东从陆壳－过渡壳－洋壳逐渐过渡的. 相似文献
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本文以地质与地球物理资料作为约束条件,利用小波多尺度分析方法,对首都圈地区重力场进行了有效分离,应用Parker位场界面反演法及变密度模型对莫霍界面进行了反演分析,并构建了两条地壳密度结构剖面模型,对该区精细地壳结构进行了深入研究.研究结果表明首都圈地区受多期构造运动的改造,形成坳、隆相邻,盆、山相间,密度非均匀性,壳内结构与莫霍面埋深相差比较大的地壳分块构造格局.受华北克拉通岩石圈伸展、减薄以及岩浆的上涌底侵作用,首都圈地区莫霍面起伏比较大,莫霍面区域构造方向呈NE-NNE方向,在盆地向太行山、燕山过渡地带形成了莫霍面陡变带;盆地内部莫霍面形成东西向排列、高低起伏的框架,最大起伏约5 km,但平均地壳厚度比较小,北京、唐山地区地壳厚度最小约29 km,武清凹陷地壳厚度最大约34 km.在重力均衡调整作用下,西部太行山区地壳厚度较大,但地壳密度小于华北裂谷盆地内部;中上地壳重力场特征与地表地形及地貌特征具有很大的相关性.受新生代裂谷作用影响,首都圈中上地壳结构非常复杂,形成了NNE方向为主体的构造单元,断层多下延至中地壳;下地壳发生明显的褶曲构造,表现出高低密度异常相间排列的典型特征;首都圈地区地壳密度具有明显的非均匀性.研究认为首都圈地区地震的发生与上地幔顶部及软流层物质的上涌有一定关系. 相似文献
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给出了利用反射波走时重建地壳三维界面的方法 ,并处理了华北地区人工地震测深测线网中的PmP走时资料 ,获得了研究区莫霍界面的三维构造形态 ,确定了壳内深断裂的展布。结果表明 ,研究区莫霍界面埋深整体上由东南向西北加深 ,并在这一背景之上呈现波浪起伏 ,断陷盆地对应上地幔的隆起 ;区内存在数条延伸至莫霍面的地壳深断裂 ,其中大致沿北东走向展布的地壳厚度陡变带和沿北西西向的地壳厚度变异带是区内两条主要的深部构造带。将研究结果与本区中、强地震空间分布特征相结合 ,揭示了地震活动的深部构造背景 相似文献
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利用天然地震和工程爆破在莫霍界面上的反射波和首波测定地壳厚度的方法，求出临汾地区的地壳平均厚度为３８ｋｍ，侯马、介休地区３７ｋｍ、吕梁山区４４ｋｍ，太行山区４３．５ｋｍ。指出沿临汾盆地汾河河谷有深大断裂存在，地壳深部莫霍间断面为一上隆的条状地带与地面的ＮＮＥ向断陷盆地相对应。 相似文献
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讨论华南黑水─泉州地学断面的重磁解释。在解释中除应用常规的２．５维重磁异常反演外，还采用等密度线算法构制梯度层密度模型，用于分辨地壳密度细结构，以及计算自由地幔而深度用于分析上地幔密度的横向不均匀性。重磁模拟结果揭示了１０ｋｍ深度内的上地壳构造以及地壳与上地幔密度的分布。提出华南造山带以低密度上地幔为特征，它可能与上地幔的改造有关；四川盆地具有较高的上地幔密度，为未经改造的原始地幔。扬子克拉通与华南造山带的分界线与上地幔密度的分界线一致。根据布格异常、地表岩石密度和地形资料的综合分析，圈定出反映内生成矿作用深部标志的密度倒转区，可作为进一步找矿的远景区。 相似文献
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讨论华南黑水─泉州地学断面的重磁解释。在解释中除应用常规的２．５维重磁异常反演外，还采用等密度线算法构制梯度层密度模型，用于分辨地壳密度细结构，以及计算自由地幔而深度用于分析上地幔密度的横向不均匀性。重磁模拟结果揭示了１０ｋｍ深度内的上地壳构造以及地壳与上地幔密度的分布。提出华南造山带以低密度上地幔为特征，它可能与上地幔的改造有关；四川盆地具有较高的上地幔密度，为未经改造的原始地幔。扬子克拉通与华南造山带的分界线与上地幔密度的分界线一致。根据布格异常、地表岩石密度和地形资料的综合分析，圈定出反映内生成矿作用深部标志的密度倒转区，可作为进一步找矿的远景区。 相似文献
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重力均衡的现象证明,地壳或上地幔内部必有水平方向的物质流动,它产生重力补偿作用,并且最终达到平衡状态。上地幔的低速层（其顶面在大陆地区约为120公里,在海洋地区约为60公里）可能是产生全球范围内重力补偿作用的一个重要层。地壳内部如有重要的补偿层,莫霍界面的深度将趋一致。莫霍界面深度的变化,说明地壳内部必无较大范围的补偿层。以莫霍界面为顶面的上地幔部分,对于重力补偿是否起作用呢?这个问 相似文献
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研究龙门山及邻区地壳密度结构对于认识该地区地震活动性具有重要意义.根据龙门山及邻区( 100°～105°E,28°～33°N)的布格重力异常资料,选取了跨越龙门山断裂带的6条重力测线,在深地震测深资料约束下,使用Geosoft软件分别反演出了龙门山地区地下的沉积层、康拉德界面和莫霍面的深度分布.研究结果表明:龙门山断裂带两侧的地壳结构明显不同,西面高原地区沉积层较薄,大部分为基岩出露;而东边盆地沉积层明显较厚,多在6km以上.莫霍面和康拉德面在两侧均相对平缓,康拉德面从东部的大约24km增加到青藏高原山区的35km左右;莫霍面深度从东部盆地的大约42km增加到西部青藏高原的67km左右.龙门山断裂带整体表现为一条近SN向的陡变重力梯度带,并在其地壳内各界面均发生错断,莫霍面和康拉德面错断距离分别达6 ～ 7km和3～ 5km.该区地壳的这种陡变和不均匀性是导致地震活动性强烈的主要原因之一. 相似文献
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Studies on the crustal and upper-mantle structure in Antarctica have been one of the major contributions to Antarctic research since the International Geophysical Year of 1957–1958. Many refraction surveys with small charge size have been conducted in Antarctica, but long-range experiments were also made in 5 regions on the margin of the Antarctic continent.In 1979–1981, the scientific program of the Japanese Antarctic Research Expedition was focused on the earth sciences, and in particular, an explosion seismic experiment along a long survey line was the major item during these years. An experiment along a 300 km-long line with three shots and 27 observation stations was successfully made in the northern Mizuho Plateau, East Antarctica.From the analysis of travel times and the amplitude study of synthetic seismograms, the crustal structure of the northern Mizuho Plateau was determined. The depths of the Conrad and the Moho discontinuties were determined as 31 km and 42 km, respectively. The P-wave velocity and depth relation was determined as 6.0 km/s on the surface of the bedrock, 6.3 km/s at a depth of 2 km, 6.8 km/s at the Conrad and 7.9 km/s at the Moho. The velocity in the crust increases gradually. The crustal structure obtained is representative of East Antarctica. 相似文献
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The first P-arrival time data from local earthquakes are inverted for two-dimensional variation of the depths to the Conrad
and Moho discontinuities in the Kyushu district, southwest Japan. At the same time, earthquake hypocenters and station corrections
are determined from the data. The depths to the discontinuities are estimated by minimizing the travel time residuals of first
P-arrival phases for 608 earthquakes observed at 57 seismic stations. In the land area of Kyushu, the Conrad and Moho discontinuities
are located within the depth ranges of 16–18 and 34–40 km, respectively. The Conrad discontinuity is not as largely undulated
as the Moho discontinuity. The depth to the Moho is deep along the east coast of Kyushu, and the deepest Moho is closely related
to markedly low velocity of P wave. We regard the deepest Moho as reflecting the Kyushu–Palau ridge subducting beneath the
Kyushu district, together with the Philippine Sea slab. In western Kyushu, the shallow Moho is spreading in the north–northeast–south–southwest
direction in the Okinawa trough region. Based on the presence of low-velocity anomaly in three-dimensional velocity structure
and seismogenic stress field of shallow crustal earthquakes, the shallow Moho is interpreted as being due to lower crustal
erosion associated with a small-scale mantle upwelling in the Okinawa trough region. The velocity discontinuity undulation
basically has insignificant effect on hypocenter determination of the local earthquakes, but the Moho topography makes changes
in focal depths of some upper mantle earthquakes. The depth variation of the Moho discontinuity has a good correlation with
the Bouguer gravity anomaly map; i.e., the shallow Moho of western Kyushu and the deep Moho of eastern Kyushu closely correlate
with the positive and negative Bouguer gravity anomalies, respectively. 相似文献
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The first P-arrival-time data from 513 local earthquakes were analyzed to study lateral variation of the depth to the Conrad
and Moho discontinuities beneath the Chugoku and Shikoku districts, southwest Japan, as well as to determine earthquake hypocenters
and P-wave station corrections. The depth to the discontinuity was estimated by minimizing the travel-time residuals of more
than 8700 first P arrivals observed at 55 seismic stations. The Conrad and Moho discontinuities are located within depth ranges
of 15–25 km and 30–40 km, respectively. The Moho is deeper under the mountain area than under the Seto Inland Sea area, and
especially deep under the Pacific Coast of the Shikoku district and the mountain area in the Chugoku district. The depth variation
of the Moho is quite similar to the Bouguer gravity anomaly distribution and the lateral variations of the P-wave velocity.
The deep Moho under the southern Shikoku is located at the portion in which the continental Moho under the island arc meets
the oceanic Moho that is the boundary interface between the oceanic crust and the Philippine Sea (PHS) plate dipping toward
the back arc. Although there are high mountains in the northern and middle Shikoku, the Moho is not so deep because subduction
of the PHS plate prevents the Moho from getting deep, while the Moho is deep due to isostatic balance under the mountain area
in the Chugoku district. In addition, we indicated the possibility that the upper boundary of the oceanic crust just above
the high-velocity PHS plate is in contact with the deep Moho under the western Chugoku. The contact of the Moho with the oceanic
crust can explain the markedly negative gravity anomaly observed in the western Chugoku and the later phase that appears just
after the first P arrival from local earthquakes. 相似文献
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使用布格重力资料对郯庐断裂带的中段部分（沂沭断裂带）进行了研究. 结果表明, 郯庐断裂带莫霍面及地壳内界面均发生错断,断裂带两侧地壳各界面起伏平缓. 该结果与前人的郯庐断裂带是切穿地壳的深大断裂的认识相一致. 在郯庐断裂带两侧,地壳结构明显不同,西侧沉积层较薄,平均在5 km以下;东侧多数在6 km以上;在断裂带中央沉积物最薄,大约为3～4 km. 断裂带东侧莫霍面埋深浅,大约为33～34 km;西侧莫霍面埋深明显增加,达到36～38 km．反映了莫霍面深度在断裂带附近整体是向西增加的. 郯庐断裂带在重力场分布中则表现为一条宽度较大的线性布格重力异常梯度带. 相似文献
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Although Tanlu fault is one of the most important tectonic fault zones and active earthquake belts in eastern China, little is known about its deep structure. In this study, we use the existing Bouguer gravity data to study the middle section of the Tanlu fault zone, which is also known as the Yishu fault zone. Our gravity inversion results indicate that the Moho has an abrupt offset in depth at the Tanlu fault zone and it has a relatively smooth variation away from the fault zone. The crustal structures on both sides are different from each other. Sediment is thin on the west side with an average thickness of less than 5 km, while it is as thick as 6 km on the east side. The thinnest sediment （3-4 km） is at the fault zone. Moho depth increases from 33 to 34 km on east side and from 36 to 38 km on west side. Tanlu fault zone is shown as a wide zone of linear gradient in the Bouguer gravity anomaly. 相似文献
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本文对喜马拉雅计划二期部分台站的远震波形数据进行接收函数提取,利用接收函数共转换点叠加方法获得阿拉善地块、鄂尔多斯地块以及银川—河套盆地下方0~80 km深度的速度间断面结构.结果表明:鄂尔多斯地块成层性好,地壳厚度为38~42 km,康拉德界面为18~22 km,阿拉善地区的Moho面深度为38~45 km.河套盆地地壳厚度约52 km,银川断陷盆地和贺兰山下方的Moho面最深为~55 km.鄂尔多斯西缘构造边界下方Moho面变化明显,且黄河断裂为深大断裂直接切割莫霍界面.根据本文的间断面成像结果我们进一步确定阿拉善地块与鄂尔多斯地块分属不同的大地构造单元.与此同时,我们推测贺兰山以西70~80 km范围内和鄂尔多斯地块西缘北段存在地壳增厚变形的可能. 相似文献
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Based on the method of "two-dimensional depth structure of the crust" proposed by Horiuchi et al., about 5000 arrival times of 303 local shallow earthquakes recorded by the Beijing Seismographic Network from 1990 ~ 1993 are used to investigate the depth distribution of Moho discontinuity beneath Beijing and its adjacent area. We simultaneously determined the hypocenter parameters and P- and S-wave station corrections. The data of the North China Network were also investigated. The results are as follows: (1) The depth distribution of Moho discontinuity becomes shallower from the northwest to the southeast, i.e., in Zhangjiakou area, the Moho discontinuity is located at a depth range from 40~42 km. In the Beijing area, it is 36~39 km. However, at the eastern and southeastern part of this area, it is only 28-30 km and 30~32 km, respectively. (2) Beneath the Tangshan area, there is another elliptic interface shallower than the Moho discontinuity. Separately, its major and minor axis is approximately along 相似文献
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利用71个远震的波形资料,用接收函数方法提取了布设在长白山—镜泊湖火山区的34个宽频带流动数字地震台站的接收函数,通过对接收函数反演,获得了台站下方的S波速度结构.研究结果表明,沈阳—敦化一线莫霍面深度32～33km,向西地壳厚度加厚,到长春附近地壳厚度约为36km.在天池火山口莫霍面深度为达38km,而镜泊湖火山口森林的莫霍面深度约为39km.总体看研究区的地壳厚度是南浅北深.长白山天池火山口附近地下10km左右有一明显的低速层存在;镜泊湖火山口森林附近30km也可能有低速体存在;研究发现莫霍面上S波速度梯度在火山口附近和远离火山口有明显区别.在火山口附近其莫霍面的S波速度梯度比非火山口地区的S波速度梯度明显小,说明火山口下与一般的地壳莫霍面结构有差别.研究发现沈阳—敦化一线两侧的莫霍面深度有较大变化,其位置与地表的敦化—密山断裂基本一致,说明敦化—密山断裂是研究区的一条非常重要的地质构造带. 相似文献
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基于河北测震台网现用速度模型,利用走时方程计算得到河北地区Pb震相的盲区范围大致为70km左右,作为初至震相的起始震中距范围为90~120km,作为后续震相的起始震中距范围为135~150km;收集近年京津冀地区2.0级以上地震88条,根据Pb震相理论波形特征,以及理论波形与实际波形到时比对,最终识别到158个有效Pb震相,拟合速度为6.69km/s,康拉德界面埋深21km,并得到河北地区Pb震相实际波形特征,弥补了河北台网Pb震相空白;利用Pb震相的射线分布,分析认为康拉德界面在河北北部山区发育程度较好,南部次之,中部渤海湾盆地地区连续性最差。 相似文献