The geological evolution of southern McMurdo Sound — new evidence from a high-resolution aeromagnetic survey     

G. Wilson  D. Damaske  H.-D. Möller  K. Tinto  T. Jordan 《Geophysical Journal International》2007,170(1):93-100

Magnetic anomaly data are presented from a new helicopter-borne high-resolution aeromagnetic survey in southern McMurdo Sound. Anomaly data have been acquired at a common 305 m elevation above the McMurdo and southern McMurdo ice shelves and draped over the volcanic islands that pin them. The resulting anomaly patterns provide a significant advance in the understanding of the rift related geology beneath the floating ice shelves. More extensive Erebus Volcanic Province (McMurdo Volcanic Group) rocks are indicated along with a significant blanket of glaci-volcaniclastic sediment on the seafloor between the volcanic islands in southern McMurdo Sound. These glaci-volcaniclastic sediments are inferred to originate from former grounding of the southern McMurdo Ice Shelf as a marine ice sheet. A strong N–S fabric is also observed in the anomaly data suggesting that the rift structure observed in the Victoria Land basin persists to the south beneath the McMurdo and southern McMurdo ice shelves. W–N–W transfer faults identified within the Transantarctic Mountain rift flank to the west are not obvious in the aeromagnetic data set, implying that the 'Discovery Accommodation Zone' may be restricted to the region between a southward extension of the range bounding fault that marks the limit of the Victoria Land Basin and the right lateral offset in the Transantarctic Mountain front in southern Victoria Land.  相似文献   

Spatial variability and non-linearity of strong ground motion near a fault     

Hayrullah Karabulut  Michel Bouchon 《Geophysical Journal International》2007,170(1):262-274

We present observations of ground accelerations recorded at a small array close to the fault during the Düzce earthquake and its early aftershocks. The records show the strong spatial variability of ground acceleration over distances of only a few hundred metres. During the main shock, the peak horizontal acceleration values ranged from 0.3 to about 1.0 g at stations distant of 1.5 km only. We attribute this spatial variability to a fault zone site effect as peak ground acceleration steadily increases as the distance to the fault trace decreases. The spectral ratio between the ground motion recorded near the fault and the one outside the fault zone shows a shift of the spectral peak to lower frequencies with increasing peak accelerations. Such an observation suggests a non-linear behaviour of the fault zone due to the strong ground shaking. As much as a 45 per cent reduction in the shear wave velocity is necessary for the observed shifts. The opening of pre-existing cracks throughout the fault zone is the proposed mechanism to account for the observed shear wave reductions. The observation that elastic fault zone properties are soon recovered following episodes of large strains shows that cracks and fissures close rapidly after the strong shaking is over.  相似文献   

Seismic hazard on the French Riviera: observations, interpretations and simulations     

F. Courboulex  C. Larroque  A. Deschamps  C. Kohrs-Sansorny  C. Gélis  J. L. Got  J. Charreau  J. F. Stéphan  N. Béthoux  J. Virieux  D. Brunel  C. Maron  A. M. Duval  J-L. Perez  P. Mondielli 《Geophysical Journal International》2007,170(1):387-400

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Emplacement, growth, and gravitational deformation of serpentinite seamounts on the Mariana forearc     

A. J. Oakley  B. Taylor  P. Fryer  G. F. Moore  A. M. Goodliffe  J. K. Morgan 《Geophysical Journal International》2007,170(2):615-634

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Statistical properties of seismicity of fault zones at different evolutionary stages     

G. Hillers  P. M. Mai  Y. Ben-Zion  J.-P. Ampuero 《Geophysical Journal International》2007,169(2):515-533

We perform a systematic parameter space study of the seismic response of a large fault with different levels of heterogeneity, using a 3-D elastic framework within the continuum limit. The fault is governed by rate-and-state friction and simulations are performed for model realizations with frictional and large scale properties characterized by different ranges of size scales. We use a number of seismicity and stress functions to characterize different types of seismic responses and test the correlation between hypocenter locations and the employed distributions of model parameters. The simulated hypocenters are found to correlate significantly with small L values of the rate-and-state friction. The final sizes of earthquakes are correlated with physical properties at their nucleation sites. The obtained stacked scaling relations are overall self-similar and have good correspondence with properties of natural earthquakes.  相似文献   

Fault induced permanent ground deformations: Experimental verification of wet and dry soil, numerical findings’ relation to field observations of tunnel damage and implications for design     

Jrgen Johansson  Kazuo Konagai 《Soil Dynamics and Earthquake Engineering》2007,27(10):938-956

Few building codes contains provisions fault surface ruptures and accompanying soil deformations which constitutes a great risk to human lives, buildings and infrastructure. A numerical and experimental comparison show a fair agreement of result. Analysis of “real” scale show the how water increases the incompressibility of wet soil causing shear deformations to become larger and conjugate ruptures to appear for reverse faults. Field observations and numerical analysis indicates that horizontal compression of soil surrounding underground structures should be taken into account in design.  相似文献   

Comprehensive Multi-Level Exploration of Buried Active Faults： an Example of the Yinchuan Buried Active Fault     

Chai Chizhang 《中国地震研究》2007,21(3):225-235

The paper introduces the steps and methods of multi-approach,multi-level exploration of buried faults in thick Quaternary sediment regions by taking the test exploration of the Yinchuan active fault as example.Based on the comprehensive analyses of previous data,we choose the Xinqushao Village of Xingqing District of Yinchuan City as the test site for the comprehensive exploration.Firstly,we adopted shallow seismic investigation with group intervals of 10m,5m and 1m to gradually trace layer by layer the master fault of the Yinchuan buried fault from a deep depth to a shallow depth where drilling could be used.Then,with composite geological profile drilling,we determined the precise location and dip angle of the fault.The drilling show the buried depth of the upper offset point is 8.3m.Finally,large-scale trenching revealed that the actual buried depth of the upper offset point of the fault is 1.5m from the ground surface and there are paleoearthquake events of 5 stages.Combined with the preliminary result of corresponding sample age,we conclude the Yinchuan buried fault is a mid to late Holocene active fault.  相似文献   

高分辨率浅层人工地震勘探探测隐伏断裂实例   总被引：1，自引：4，他引：1       下载免费PDF全文

连玉平  张锦福  林松建  陈伟 《地震工程学报》2007,29(3):260-263

利用高分辨率浅层地震勘探反射波法探测了福建某火电厂场址内的隐伏断裂。结果表明断裂显示清楚,为一走向NE40~55°,上断点埋深为11 m和31 m,断距2~4 m的正断层,为工程避让提供较可靠的依据。  相似文献   

Geochemistry and spatial distribution of OIB and MORB in A’nyemaqen ophiolite zone: Evidence of Majixueshan ancient ridge-centered hotspot   总被引：2，自引：0，他引：2  

Guo AnLin  Zhang GuoWei  Sun YanGui  Zheng JianKang  Liu Ye  Wang JianQi 《中国科学D辑(英文版)》2007,50(2):197-208

The mafic volcanic association is made up of OIB, E-MORB and N-MORB in the A'nyemaqen Paleozoic ophiolites. Compared with the same type rocks in the world, the mafic rocks generally display lower Nb/U and Ce/Pb ratios and some have Nb depletion and Pb enrichment. The OIB are LREE-enriched with (La/Yb)N =5―20, N-MORB are LREE-depleted with (La/Yb)N = 0.41―0.5. The OIB are featured by incompatible element enrichment and the N-MORB are obviously depleted with some metasomatic effect, and E-MORB are geochemically intermediated. These rocks are distributed around the Majixueshan OIB and gabbros in a thickness greater than a thousand meters and transitionally change along the ophiolite extension in a west-east direction, showing a symmetric distribution pattern as centered by the Majixueshan OIB, that is, from N-MORB, OIB and E-MORB association in the Dur'ngoi area to OIB in the Majixueshan area and then to N-MORB, OIB and E-MORB assemblage again in the Buqingshan area. By consideration of the rock association, the rock spatial distribution and the thickness of the mafic rocks in the Majixueshan, coupled with the metasomatic relationship between the OIB and MORB sources, it can be argued that the Majixueshan probably corresponds to an ancient hotspot or an ocean island formed by mantle plume on the A'nyemaqeh ocean ridge, that is the ridge-centered hotspot, tectonically similar to the present-day Iceland hotspot.  相似文献   

Geology and geochemistry of the Bingdaban ophiolitic mélange in the boundary fault zone on the northern Central Tianshan Belt,and its tectonic implications     

Dong YunPeng  Zhang GuoWei  Zhou DingWu  Luo JinHai  Zhang ChengLi  Xia LinQi  Xu XueYi  Li XiangMin 《中国科学D辑(英文版)》2007,50(1):17-24

The properties and tectonic significance of the fault bound zone on the northern margin of the Central Tianshan belt are key issues to understand the tectonic framework and evolutionary history of the Tianshan Orogenic Belt. Based on the geological and geochemical studies in the Tianshan orogenic belt, it is suggested that the ophiolitic slices found in the Bingdaban area represent the remaining oceanic crust of the Early Paleozoic ocean between the Hazakstan and Zhungaer blocks. Mainly composed of basalts, gabbros and diabases, the ophiolites were overthrust onto the boundary fault between the Northern Tianshan and Central Tianshan belts. The major element geochemistry is characterized by high TiO₂ (1.50%–2.25%) and MgO (6.64%–9.35%), low K₂O (0.06%–0.41%) and P₂O₅ (0.1%–0.2%), and Na₂O>K₂O as well. Low ΣREE and depletion in LREE indicate that the original magma was derived from a depleted mantle source. Compared with a primitive mantle, the geochemistry of the basalts from the Bingdaban area is featureded by depletion in Th, U, Nb, La, Ce and Pr, and unfractionated in HFS elements. The ratios of Zr/Nb, Nb/La, Hf/Ta, Th/Yb and Hf/Th are similar to those of the typical N-MORB. It can be interpreted that the basalts in the Bingdaban area were derived from a depleted mantle source, and formed in a matured mid-oceanic ridge setting during the matured evolutionary stage of the Northern Tianshan ocean. In comparison with the basalts, the diabases from the Bingdaban area show higher contents of Al₂O₃, ΣREE and HFS elements as well as unfractionated incompatible elements except Cs, Rb and Ba, and about 10 times the values of the primitive mantle. Thus, the diabases are thought to be derived from a primitive mantle and similar to the typical E-MORB. The diabases also have slight Nb depletion accompanying no apparent Th enrichment compared with N-MORB. From studies of the regional geology and all above evidence, it can be suggested that the diabases from the Bingdaban area were formed in the mid-oceanic ridge of the Northern Tianshan ocean during the initial spreading stage. Supported by the Major State Research Program of PRC (Grant No. 2001CB409801), the National Natural Science Foundation of China (Grant Nos. 40472115 and 40234041) and the State Research Program of China Geological Survey (Grant No. 2001130000-22)  相似文献