Some Problems Concerning Geologic Structure with Double Layers in Urban Underground Lifeline Engineering     

Peng Yimin Sun Jinzhong China University of Geosciences  Beijing 《中国地质大学学报(英文版)》1991,(1)

Underground lifeline engineering(ULE for short)in modern city demands the ap-preciation of an active fault in buried bedrock.Generally speaking,a large numberof urban geological textures of a basement may all be simplified into a dual geologicaltexture model,i.e.,the upper part of the basement consists of loose covering layerand the lower part consists of bedrock.The study of an active fault should includethree parts of contents,i.e.,to determine the lower time limit of activity of thefault,and the time limit must be recognized by both of designing engineers and geolo-gists;on the basis of the studies of repetition periods of earthquake occurrence to deter-mine whether the fault moves or not during the allowed time of efficacy of buildingsand constructions;for the sake of engineering practice,the active rate of the faultmust be given.The fault with different active mechanism has different effects on theULE.The authors studied the effect of lateral non-uniform overburden site on theULE by means of the su  相似文献   

Active normal faulting during the 1997 seismic sequence in Colfiorito,Umbria: Did slip propagate to the surface?     

《Journal of Structural Geology》2016

In order to determine whether slip during an earthquake on the 26th September 1997 propagated to the surface, structural data have been collected along a bedrock fault scarp in Umbria, Italy. These collected data are used to investigate the relationship between the throw associated with a debated surface rupture (observed as a pale unweathered stripe at the base of the bedrock fault scarp) and the strike, dip and slip-vector. Previous studies have suggested that the surface rupture was produced either by primary surface slip or secondary compaction of hangingwall sediments. Some authors favour the latter because sparse surface fault dip measurements do not match nodal plane dips at depth. It is demonstrated herein that the strike, dip and height of the surface rupture, represented by a pale unweathered stripe at the base of the bedrock scarp, shows a systematic relationship with respect to the geometry and kinematics of faulting in the bedrock. The strike and dip co-vary and the throw is greatest where the strike is oblique to the slip-vector azimuth where the highest dip values are recorded. This implies that the throw values vary to accommodate spatial variation in the strike and dip of the fault across fault plane corrugations, a feature that is predicted by theory describing conservation of strain along faults, but not by compaction. Furthermore, published earthquake locations and reported fault dips are consistent with the analysed surface scarps when natural variation for surface dips and uncertainty for nodal plane dips at depth are taken into account. This implies that the fresh stripe is indeed a primary coseismic surface rupture whose slip is connected to the seismogenic fault at depth. We discuss how this knowledge of the locations and geometry of the active faults can be used as an input for seismic hazard assessment.  相似文献   

塔里木盆地西部的新生代断裂活动   总被引：1，自引：0，他引：1  

张强  黄太柱  李慧莉  李曰俊  蒋华山  马庆佑  蔡习尧  文磊 《岩石学报》2016,32(3):833-846

研究区以塔里木盆地西部的巴楚隆起为核心,包括其南侧的麦盖提斜坡和北侧的北部坳陷(阿瓦提凹陷)。这里新生代断裂异常发育。以鸟山-古董山地区为重点,通过精细的地震剖面解释,在塔里木盆地西部识别出5期新生代断裂活动,分别发生于:白垩纪末-古近纪初(ca.65Ma)、中新世末-上新世初(ca.5Ma)、上新世末-更新世中期(ca.3~1.5Ma)、更新世中-晚期(ca.1~0.1Ma)和全新世(ca.0.01Ma)。中寒武统和古近系膏盐层构成了研究区的2个主滑脱面。ca.65Ma的冲断受控于基墨里中间大陆与亚洲大陆碰撞的远程效应;ca.5Ma、ca.3~1.5Ma、ca.1~0.1Ma和ca.0.01Ma的断裂活动(包括滑脱断层、冲断层、走滑断层和正断层)均受控于印度-亚洲碰撞的远程效应。晚新生代(中新世以来)的断裂活动以脉动式冲断为特征,两次相邻脉动式冲断之间为时间不等的短暂的构造间歇期;间歇期构造平静,甚至可以形成正断层。  相似文献   

Neotectonics of the Eastern Margin of the Tibetan Plateau: New Geological Evidence for the Change from Early Pleistocene Transpression to Late Pleistocene-Holocene Strike-slip Faulting   总被引：1，自引：0，他引：1  

ZHANG Yueqiao  LI Hailong  and LI Jian 《《地质学报》英文版》2016,90(2):467-485

We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred during the Early Pleistocene, evidenced by eastward thrusting of Mesozoic carbonates on the Pliocene lacustrine deposits along the Minjiang upstream fault zone and by development of the transpressional ridges of basement rocks along the Anninghe river valley. The Middle Pleistocene seems to be a relaxant stage with local development of the intra-mountain basins particularly prominent along the Minjiang Upstream and along the southern segment of the Anninghe River Valley. This relaxation may have been duo to a local collapse of the thickened crust attained during the late Neogene to early Pleistocene across this marginal zone. Fault kinematics has been changed since the late Pleistocene, and was predominated by reverse sinistral strike-slip along the Minshan Uplift, reverse dextral strike-slip on the Longmenshan fault zone and pure sinistral strike-slip on the Anninghe fault. This change in fault kinematics during the Quaternary allows a better understanding of the mechanism by which the marginal ranges of the plateau has been built through episodic activities.  相似文献   

南冲绳海槽地震反射波特征及其地质解释     

刘建华 《海洋学研究》2001,19(1):19-26

对南冲绳海槽进行反射地震调查 ,结果表明 :(1 )海槽盖层主要由反射层组 (时代相当于第四纪 )和反射层组 (时代相当于上新世 )组成 ,推测槽底局部存在中新统。槽底沉积物主要源自中国大陆。轴部目前仍处在裂陷作用阶段 ;(2 )断裂极为发育 ,可分 NE— SW向(西南端转为近 E— W向 )和 NW— SE向两组 ,分别属张性及张扭性断裂 ,后者切割前者 ;(3)岩浆活动十分强烈 ,东南缘岩浆活动尤甚 ,推测其岩性以中、基性岩为主  相似文献   

Mechanics of seismic instabilities induced by the recovery of hydrocarbons     

J. -R. Grasso 《Pure and Applied Geophysics》1992,139(3-4):507-534

We review earthquake distributions associated with hydrocarbon fields in the context of pore pressure diffusion models, poroelastic stress transfer and isostasy theory. These three mechanisms trigger or induce seismic instabilities at both local scale (D5 km) and at regional scale (D20 km). The modeled changes in stress are small (1 MPa), whatever the tectonic setting. Each mechanism corresponds to different production processes. (1) Local hydraulic fracturing due to fluid injection induces seismic-slip on cracks (M _L3) within the injected reservoir through decreasing the effective stress. (2) Pure fluid withdrawal causes pore pressure to decrease within the reservoir. It triggers adjustments of the geological structure to perturbations related to the reservoir response to depletion. Poroelastic mechanisms transfer this stress change from the reservoir to the surrounding levels whereM _L5 seismic instabilities occur either above or below the reservoir. (3) Massive hydrocarbon recovery induces crustal readjustments due to the removal of load from the upper crust. It can induce larger earthquakes (M _L6) at greater distance from the hydrocarbon fields than the two other mechanisms.Due to the mechanical properties of the shallow rock matrices involved, seismic slip triggered either by mechanism (1) or (2), is a second-order process of the main elastoplastic deformation. for a minimum of 80% of commercially productive basins, most of the local deformation is reported as aseismic, i.e., there is no evidence forM _L3 earthquakes. Nevertheless, the induced stresses vary as a function of time in a manner that depends on the hydraulic diffusivity (i.e., permeability) of the reservoir and surrounding rocks. Because small earthquakes (M _L3) indicate changes in stress and pore pressure, monitoring of seismicity is a means of assessingin situ reservoir behavior.The less constrained seismic response to hydrocarbon recovery is the possible connection between local fluid manipulations, triggered earthquakes and major regional earthquakes. Positive feedback mechanisms suggest that the region of seismic hazard changes is much larger than the area where hydrocarbons are extracted. These observations and models testify that fluid movement and pore pressure changes (increase or decrease) play important roles in the mechanics of earthquakes and in the triggering of natural earthquakes.  相似文献   

Formation of lode‐style gold mineralisation during Tabberabberan wrench faulting at Lefroy,eastern Tasmania     

A. Reed 《Australian Journal of Earth Sciences》2013,60(5):879-890

The Lefroy Goldfield in eastern Tasmania is anomalous in southeastern Australia because mineralised fault reefs (i.e. reefs that are also faults) strike in an easterly direction at a high angle to the predominantly northwest strike of bedding and folds. Gold mineralisation is of Early to Middle Devonian age, with reef formation coinciding with a third regionally compressive deformation event (D₃), and a second phase of Tabberabberan orogenesis. Mineralised reefs are hosted by Mathinna Supergroup turbidites of Cambrian to Ordovician age and extend for up to 2 km across the boundary between the sandstone‐dominated Stony Head Sandstone and the shale‐dominated Turquoise Bluff Slate. Ore shoots in the reefs plunge moderately west and, in the Volunteer Mine, coincide with the intersection of the reef and a D₁/D₂ thrust contact. The subvertical orientation and discordant relationship of the mineralised reefs to bedding, as well as the lack of gold mineralisation along bedding and pre‐D₃ structures, indicate that the reefs formed during a period of wrench faulting. In contrast to lode‐style deposits in Victoria, the far‐field minimum compressive stress at Lefroy during reef formation was not vertical but, rather, occupied a subhorizontal orientation.  相似文献   

Faulting and earthquake triggering during the 1783 Calabria seismic sequence   总被引：9，自引：0，他引：9  

E. Jacques  C. Monaco  P. Tapponnier  L. Tortorici  T. Winter 《Geophysical Journal International》2001,147(3):499-516

  相似文献   

论我国微细浸染型金矿床与沉积盆地演化的关系——以右江盆地为例   总被引：19，自引：1，他引：19  

刘建明  叶杰  刘家军  顾雪祥 《矿床地质》2001,20(4):367-377

对华南右江盆地中某些微细浸染型金矿床开展了系统的地质学、组构学以及矿床地球化学研究。地质学和组构学研究表明，这类矿床具有大量的沉积阶段－成岩阶段的成因特征，在沉积物沉积－成岩期间就已经成矿。矿化与碳酸盐岩孤台的密切联系和丰富的成岩期软变形组构，表明成矿与控制海底地形的同沉积期断裂活动密切相关。而大量泄水构造和液化层理的出现则表明，在沉积物成岩阶段，沉积柱中曾有大量流体的活动。而且这种盆地流体的活动与成矿有密切关系。丰富的生物－有机成因组构则显示，成矿与沉积有机质的演化有着密切的内在联系。另外，矿床没有显示出与岩浆活动的任何关系。因此，右江盆地的微细浸染型金矿床与美国的卡林型金矿床不同，可能是离散大陆边缘张性盆地演化过程中盆地流体活动的产物之一。这一认识也得到地球化学研究不同程度的支持。  相似文献   

断层活动时间的同步性特点     

刘行松  唐汉军 《华南地震》1993,(1)

断层活动是地壳应力释放等的一种表现。其主要应力一般通过区域性断层释放,小断层除释放剩余应力外也可是前者活动时的牵动。因此,在一个局部地区内断层活动时间常具有同步性特点。对化稍营地区大、小断层的研究表明,传统法确认油房断层被上更新统复盖,其最后一次活动时间在晚更新世以前;应用热释光、铀系法与显微构造分析结合,研究发育在基岩中的壶流河断层、F_(207)断层、F_(214)断层和F_(213)断层,确定其最后一次较强烈活动为距今20～30万年前。两者结果的吻合,证明了断层活动时间的同步性特点。  相似文献