盐源-宁蒗地震共轭破裂及极限主应力随地壳深度变化

许多震例表明,地震可以形成于共轭破裂。地震震源处,其温度和压力与地壳浅处及地表不同,温、压越高,共轭破裂角越大,随着深度的变浅(温、压减小),地震共轭破裂角减小;高烈度等震线共轭角也减小。用数学力学方法和岩石力学实验结果,探讨了1976年盐源-宁蒗6.7和6.4级地震共轭破裂及极限主应力随地壳深度变化。      

盾构法隧道施工阶段管片的力学分析

盾构隧道衬砌管片在施工阶段处于复杂的受力状态,易出现局部破损现象。阐明了盾构施工阶段管片的受力特点,对其常见的局部破损现象及产生原因进行了总结与分析,在此基础上构建了施工阶段的管片力学模型,即一端固定、一端简支的受力构件。以某盾构工程施工参数为例,运用有限元方法实现该力学模型,按不同工况对其进行了数值模拟,并与现场实测结果进行了对比分析。研究表明：盾构施工阶段,衬砌管片会在第5～7环之间产生局部破损,与现场出现的管片破损部位十分接近;千斤顶推力的大小、倾角及偏差是导致施工阶段管片局部破损的主要原因,并给出了盾构施工阶段减轻管片破损的一些建议。     

建立在雷达卫星影像判读基础上四川龙门山断裂晚第四纪活动特征研究

介绍了应用雷达卫星影像对四川龙门山活动断裂开展断错地貌判读结果,展示了龙门山构造带4条分支断裂9个点位的雷达卫星影像图像、11个点位的野外调查结果及6个点位与断层活动性有关的地层测年。在11个野外调查点位中,位于青城山北面4条断裂8个点位均出现2008年5.12汶川MS8.0地震的地表破裂,其中包括沿青川断裂青溪段及金山寺断层沟谷出现的两条地表破裂,沿后山断裂带茂县北断层和汶川南七盘沟断层出现的地表破裂;   沿中央断裂带北川和小鱼洞南2个点位出现的地表破裂;   以及沿前山断裂汉旺台地前缘和青城山山前地表破裂点位。在这些地表破裂中,中央断裂带地表垂直位移为 2～6m,青川断裂、后山断裂和前山断裂多数段地表断错垂直位移量为 10～40cm。后者位移量虽小,也不应被忽视。本项研究结果表明,雷达卫星影像显示青川断裂与后山断裂带和中央断裂带右旋走滑明显。雷达卫星影像实地调查表明,前山断裂带南段的水口场－横山庙断裂带醒目的断错地貌引人注目。     

汶川地震对现代河流形态的影响与水文效应

2008年5月12日14时28分,我国四川发生里氏8.0级大地震,发震构造为龙门山断裂带.形成了NE向映秀-北川断裂地表破裂带,彭县-灌县断裂破裂带以及NW向的小鱼洞破裂带,表现为逆冲-走滑性质.目前,有关地表破裂、次生地质灾害及堰塞湖等开展了大量的调查工作,而地震对河流形态的影响还缺少较为系统的分析.在野外地震地貌考察的基础上,根据河流走向与断层位置关系,并结合地表破裂特征,总结了汶川地震对现代河流形态影响的几种地貌类型:顺向陡坎跌水,河道错动,断寨湖(塘),河流改道等,并对其演化趋势进行了讨论.分析了汶川地震的河流水文效应:地震增加了河流泥沙含量,改变了河流水质,同时,也使得河流与地下水系统之间的联系更为紧密.     

Tsunami impact to Washington and northern Oregon from segment ruptures on the southern Cascadia subduction zone

This paper explores the size and arrival of tsunamis in Oregon and Washington from the most likely partial ruptures of the Cascadia subduction zone (CSZ) in order to determine (1) how quickly tsunami height declines away from sources, (2) evacuation time before significant inundation, and (3) extent of felt shaking that would trigger evacuation. According to interpretations of offshore turbidite deposits, the most frequent partial ruptures are of the southern CSZ. Combined recurrence of ruptures extending ~490 km from Cape Mendocino, California, to Waldport, Oregon (segment C) and ~320 km from Cape Mendocino to Cape Blanco, Oregon (segment D), is ~530 years. This recurrence is similar to frequency of full-margin ruptures on the CSZ inferred from paleoseismic data and to frequency of the largest distant tsunami sources threatening Washington and Oregon, ~M _w 9.2 earthquakes from the Gulf of Alaska. Simulated segment C and D ruptures produce relatively low-amplitude tsunamis north of source areas, even for extreme (20 m) peak slip on segment C. More than ~70 km north of segments C and D, the first tsunami arrival at the 10-m water depth has an amplitude of <1.9 m. The largest waves are trapped edge waves with amplitude ≤4.2 m that arrive ≥2 h after the earthquake. MM V–VI shaking could trigger evacuation of educated populaces as far north as Newport, Oregon for segment D events and Grays Harbor, Washington for segment C events. The NOAA and local warning systems will be the only warning at greater distances from sources.     

Great earthquakes of variable magnitude at the Cascadia subduction zone

Comparison of histories of great earthquakes and accompanying tsunamis at eight coastal sites suggests plate-boundary ruptures of varying length, implying great earthquakes of variable magnitude at the Cascadia subduction zone. Inference of rupture length relies on degree of overlap on radiocarbon age ranges for earthquakes and tsunamis, and relative amounts of coseismic subsidence and heights of tsunamis. Written records of a tsunami in Japan provide the most conclusive evidence for rupture of much of the plate boundary during the earthquake of 26 January 1700. Cascadia stratigraphic evidence dating from about 1600 cal yr B.P., similar to that for the 1700 earthquake, implies a similarly long rupture with substantial subsidence and a high tsunami. Correlations are consistent with other long ruptures about 1350 cal yr B.P., 2500 cal yr B.P., 3400 cal yr B.P., 3800 cal yr B.P., 4400 cal yr B.P., and 4900 cal yr B.P. A rupture about 700-1100 cal yr B.P. was limited to the northern and central parts of the subduction zone, and a northern rupture about 2900 cal yr B.P. may have been similarly limited. Times of probable short ruptures in southern Cascadia include about 1100 cal yr B.P., 1700 cal yr B.P., 3200 cal yr B.P., 4200 cal yr B.P., 4600 cal yr B.P., and 4700 cal yr B.P. Rupture patterns suggest that the plate boundary in northern Cascadia usually breaks in long ruptures during the greatest earthquakes. Ruptures in southernmost Cascadia vary in length and recurrence intervals more than ruptures in northern Cascadia.     

东昆仑活动断裂带强震地表破裂分段特征

东昆仑活动断裂带是青藏高原内部一条长度达到1000km以上的活动断裂带。在近100年期间,沿该断裂带曾发生过4次M_S7.0以上地震。最新一次强震是2001年昆仑山口M_S8.1地震。本文综合前人资料,通过东昆仑活动断裂带的几何展布、活动速率、历史强震及古地震地表破裂带展布,讨论了该断裂带的强震破裂分段特征、强震破裂端点障碍体的稳定性,强调了从断裂带演化过程认识断裂带的几何展布与现今强震地表破裂分段的异同,并讨论了该断裂带未来的强震破裂危险地段。      

The Roermond earthquake of 13 April 1992, the Netherlands: geological aspects

The epicentre of the Roermond earthquake is located near the western boundary fault of the Roer valley trough, one of the deepest and the most active in the Quaternary part of the Lower Rhine graben. The Late Pleistocene and Holocene activity of the trough is manifested by offsets of the main (Mindel) and the lower (Riss and Late Pleistocene) terraces along the boundary faults.
Surface fractures have been observed in an area of more than 50 km²: 2.5–3.5 km to the north of the town of Roermond, at 0.8 km to the south of the village of Herkenbosch and in the southeastern part of the village of Montfort. Three types of ruptures were differentiated: scarps up to 50 cm high along open fractures near the Maas River; open fractures (continued by scarps in some places) and open fractures with a liquefaction of the Quaternary alluvium sands. The last type is predominant. The location of the ruptures depends on the landscape and water-table of the region. While they could be produced solely by hydraulic shock during the earthquake (increased by the wet spring season), the majority of the ruptures strike N50°W ± 10°, i.e. parallel to the main trough faults, or N55°E ± 10°, along 'neotectonic lines', parallel to the Maas valley and deduced from space imagery. Thus, the ruptures could be the secondary surficial effect of the earthquake, linked indirectly with the active tectonics of the region.     

Relationship between the Pre-existing Active Kunlun Fault and Co-seismic Surface Ruptures Produced by the 2001 Mw 7．8 Central Kunlun Earthquake，China

Field investigations allow to constrain the co-seismic surface rupture zone of ～400km with a strike-slip up to 16．3 m associated with the 2001Mw 7．8 Central Kunlun earthquake that occurred along the western segment of the Kunlun fault,northern Tibet．The co-seismic rupture structures are almost duplicated on the pre-existing fault traces of the Kunlun fault．The deformational characteristics of the co-seismic surface ruptures reveal that the earthquake had a nearly pure strike-slip mechanism．Theg eologic and topographice vidence clearly shows that spatial distributions of the co-seismic surface ruptures are re-stricted by the pre-existing geological structures of the Kunlun fault．     

A new hydrogeochemical and geotectonical interpretation of the Lake Nyos disaster in Cameroon

Conclusion The gas eruption in Lake Nyos allows solely a deep inorganic origin of the CO₂, and CO₂ ascent along intersecting ruptures to be considered. Enormous gas volumes can be liberated from ascension paths with voids in the deep sections of the Earth's crust rather than from the water-dissolved phase (a lake) on the Earth's surface. In this case, rupture activity rather than volcanic activity should be involved. Similarly to volcanic activity, other events are also associated with open ruptures in the Earth's crust. No interrelations exist between the single phenomena. One of them consists in the ascent of CO₂ with no relation to magma. Earthquakes, too, are associated with ruptures. Even a very slight tremor of the Earth's crust can contribute to the liberation of deepseated compressed CO₂. However, disturbing the equilibrium of the water-column pressure and the compressed gas can result in an eruption even with no external impetus, e. g. an earthquake.     

Seismotectonic features of the September 24, 1999 Ahram earthquake in the Zagros,Iran

The September 24, 1999 Ahram Earthquake in southwestern Iran was moderate in energy (M = 5.0–5.5 from different sources) and did not entail significant destruction and casualities. The tectonic position of the source zone, surficial seismic dislocations, and results of macroseismic and seismological study of this seismic event in the junction zone of the Zagros Fold System and the piedmont plain are described in the paper, including data on rejuvenated ancient ruptures exposed in two trenches excavated across the strike of the regional Kazerun-Borazjan Fault. One of the trenches was driven a few months before and the other a year after this seismic event. The conclusion is drawn that new deformations in the Quaternary near-surface sediments observed at the walls of both trenches may be regarded as unusual seismic ruptures of the Ahram earthquake. These ruptures, described as proved primary seismic dislocations of such a moderate seismic event, are a unique phenomenon in the world seismotectonic practice. The localization of the earthquake source zone in the Kazerun-Borazjan Fault Zone with complex kinematics makes it possible to study the internal structure of one of the most important tectonic lines of the Zagros Fold Region.     

四川汶川Ms 8.0地震地表破裂构造初步调查与发震背景分析

5月16-24日对川西汶川大地震震中区的发震断裂地带进行的实地考察和初步测量,获得了宝贵的地表变形和同震位移最数据资料,证实汶川地震属于逆冲断裂型地震,主破裂沿映秀-北川断裂带发育,前山地区滑灌县-安县断裂也有地表破裂,同震位移量在3～5m.汶川地震产牛的地表破裂构造和运动性质显示明显分段特性,映秀-北川段以挤压逆冲为主,而北川以北段则伴有显著的右旋走滑分量.     

四川汶川MS 8.0大地震地表破裂带的遥感影像解析

2008年5月12日发生于四川盆地西部龙门山断裂带的汶川MS 8.0级大地震造成巨大的人员伤亡和财产损失,并形成了空间上基本连续分布的地表破裂带（地震断层）。根据地表破裂带的解译标志及影像特征,我们充分利用震后中国科学院航空遥感飞机所获取的高分辨率航空遥感图像以及我国台湾福卫-2卫星遥感图像进行详细解译分析,并结合震后的多次野外科学考察与验证,初步查明了四川汶川MS 8.0级大地震所产生地表破裂带的空间分布特征。遥感解译分析表明汶川大地震产生的地表破裂带总计长约300 km,其几何学特征十分复杂,主要沿先存的NE走向活动断裂带呈不连续展布;变形特征以逆冲挤压为主兼具右旋走滑分量。按同震地表破裂带所在断裂带位置,可将其分为两条： 中央地表破裂带：沿映秀-北川断裂带分布,从西南开始呈北东向延伸至平武县水观乡石坎子北东一带,长约230 km,最大垂直位移量达6.0 m左右,最大右旋水平位移达5.8 m;山前地表破裂带：沿灌县-安县断裂带分布,由都江堰市向峨乡一带开始呈北东向延伸至安县雎水镇一带,长约70 km,以逆冲挤压为主,最大垂直位移量可达2.5 m。此外,遥感图像分析还表明上述地表破裂带与地质灾害分布在空间上具有十分密切的相关性,因此,挤压逆冲-走滑型地震断层的致灾效应研究是未来应该加以重视的研究课题。     

Mineralogical compositions of fault rocks from surface ruptures of Wenchuan earthquake and implication of mineral transformation during the seismic cycle along Yingxiu-Beichuan fault,Sichuan Province,China

Mineralogy and Petrology - There are two co-seismic bedrock surface ruptures from the Mw 7.9 Wenchuan earthquake in the northern and central parts of the Beichuan-Yingxiu fault, Sichuan Province,...     

Stress history controls the spatial pattern of aftershocks: case studies from strike-slip earthquakes

International Journal of Earth Sciences - Earthquake ruptures perturb stress within the surrounding crustal volume and as it is widely accepted now these stress perturbations strongly correlates...     

The Erzincan earthquake of 13 March 1992 in Eastern Turkey: tectonic aspects

The tectonic significance of the Erzincan earthquake of 13 March, 1992 in Eastern Turkey is discussed. The intersection of the North Anatolian and The East Anatolian strike-slip fault zones has resulted in formation of the Erzincan pull-apart basin and new seismically active fault branches on its northeastern side. Local concentrations of surface ruptures strike along the most active branches of the North Anatolian fault zone (N300W) for 62 km. They are usually open fractures with northeastern sides uplifted up to 20 cm and rarely with dextral offset up to 10 cm. These secondary ruptures manifest indirectly oblique seismic fault displacement corresponding to the Late Quaternary motion on the fault zone, although at the surface the dextral component has been suppressed relative to the vertical one.     

Identification of Ruptures and their Interaction with Hydrothermal–Magmatic Systems on Northern Paramushir Isl. (Kuril Islands,Russia): 3D Modeling of Tectonic Fragmentation

Geotectonics - Correlation of ruptures with volcanic activities, and related hydrothermal-magmatic systems are studied. In our research we used a set of methods that included analysis of satellite...     

The limits of self-similarity

Numerical experiments on simulating ruptures of a one-dimensional plate boundary suggest that certain basic features of seismicity (including multiple ruptures and aftershock sequences) can be adequately reproduced if one assumes the existence of an elementary particle (or geon) of fault dynamics. Some general consequences of corpuscular assumptions in the earth sciences are discussed, with particular reference to the estimation of hazard.     

Calculation of the Model of Coesite Inclusions and Analysis of Their Retrometamorphic Paths

The process and path of retrometamorphism of coesite have great significance to our understanding of the P-T tracks of the exhumation of ultrahigh-pressure metamorphic rocks. Most of the coesites in the eclogite from Shima, Anhui Province, the Dabie Mountains, China, are found degraded to quartz partly or wholly, with ruptures occurring in the shells, outside which include the coesite and quartz. According to the microscopic observation, the sample of coesite inclusion is composed of garnet, quartz and coesite, based on which we have built a three-shelled composite sphere model to compute the transition of coesite. Based on the crystal growth formulas and pressure conditions of the ruptures in the garnet, we have calculated the radius of the quartz sphere, which depends on temperature, and eventually drawn the different retrometamorphic paths for different retrometamorphism rates.     

Surface Rupture and Co-seismic Displacement Produced by the Ms 8.0 Wenchuan Earthquake of May 12th, 2008, Sichuan, China： Eastwards Growth of the Qinghai-Tibet Plateau

An earthquake of Ms 8 struck Wenchuan County,western Sichuan,China,on May 12~(th), 2008 and resulted in long surface ruptures (>300 km).The first-hand observations about the surface ruptures produced by the earthquake in the worst-hit areas of Yingxiu,Beichuan and Qingchuan, ascertained that the causative structure of the earthquake was in the central fault zones of the Longmenshan tectonic belt.Average co-seismic vertical displacements along the individual fault of the Yingxiu-Beichuan rupture zone reach 2.5-4m and the cumulative vertical displacements across the central and frontal Longmenshan fault belt is about 5-6 m.The surface rupture strength was reduced from north of Beichuan to Qingchuan County and shows 2-3 m dextral strike-slip component.The Wenchuan thrust-faulting earthquake is a manifestation of eastward growth of the Tibetan Plateau under the action of continuous convergence of the Indian and Eurasian continents.