共查询到20条相似文献，搜索用时 78 毫秒
1.
We investigated the Coulomb stress changes in the active faults surrounding a moderate‐magnitude normal‐faulting earthquake (2009 L'Aquila, Mw 6.3) and the associated variations in the expected ground motion on regional probabilistic seismic hazard maps. We show that the static stress variations can locally increase the seismic hazard by modifying the expected mean recurrence time on neighbouring faults by up to ~290 years, with associated variations in the probability of occurrence of the maximum expected earthquake of up to ~2%. Our findings suggest that the increase in seismic hazard on neighbouring faults following moderate‐magnitude earthquakes is probably not sufficient to necessitate systematic upgrades of regional probabilistic seismic hazard maps, but must be considered to better address and schedule strategies for local‐scale mitigation of seismic risk. 相似文献
2.
A systematization of active faults has been developed based on the progress of scientists from the leading countries in the
world in the study of seismotectonics and seismic hazard problems. It is underlain by the concept of the fault-block structure
of the geological-geophysical environment governed by the interaction of differently oriented active faults, which are divided
into two groups—seismogenic and nonseismogenic faults. In seismogenic fault zones, the tectonic stress accumulated is relieved
by means of strong earthquakes. Nonseismogenic fault zones are characterized by creep displacement or short-term, oscillatory,
and reciprocal movements, which are referred to local superintense deformations of the Earth’s crust (according to the terminology
used by Yu.O. Kuz’min). For a situation when a strong earthquake happens, a subgroup of seismodistributing faults has been
identified that surround the seismic source and affect the distribution of the seismic waves and, as a consequence, the pattern
of the propagation of the coseismic deformations in the fault-block environment. Seismodistributing faults are divided into
transit and sealing faults. Along transit faults, secondary coseismic effects (landfalls, landslides, ground fractures, liquefaction,
etc) are intensified during earthquakes. In the case of sealing faults, enhancement of the coseismic effects can be observed
on the disjunctive limb nearest to the epicenter, whereas, on the opposite limb, the intensity of such effects appreciably
decreases. Seismogenic faults or their systems are associated with zones of earthquake source origination (ESO), which include
concentrated seismicity regions. In such zones, each earthquake source is related to the evolution of a fault system. ESO
zones also contain individual seismogenic sources being focuses of strong earthquakes with M of ≥5.5 in the form of ruptures, which can be graphically represented in 2D or 3D as a surface projection of the source.
Depending on the type of data based on which they are identified, individual seismogenic sources are divided into geological-geophysical
and macroseismic sources. The systematization presented is the theoretical basis for and the concept of the relational database
that is being developed by the authors as an information system for the generation of seismotectonic GIS projects required
for the subsequent analysis of the seismic hazard and the assessment of the probability of the origination of macroseismic
earthquake effects in a predetermined location. 相似文献
3.
Thomas L. Pratt Mark Holmes Eugene S. Schweig Joan Gomberg Hugh A. Cowan 《Tectonophysics》2003,368(1-4):211
High-resolution seismic reflection profiles from Limón Bay, Republic of Panama, were acquired as part of a seismic hazard investigation of the northern Panama Canal region. The seismic profiles image gently west and northwest dipping strata of upper Miocene Gatún Formation, unconformably overlain by a thin (<20 m) sequence of Holocene muds. Numerous faults, which have northeast trends where they can be correlated between seismic profiles, break the upper Miocene strata. Some of the faults have normal displacement, but on many faults, the amount and type of displacement cannot be determined. The age of displacement is constrained to be Late Miocene or younger, and regional geologic considerations suggest Pliocene movement. The faults may be part of a more extensive set of north- to northeast-trending faults and fractures in the canal region of central Panama. Low topography and the faults in the canal area may be the result of the modern regional stress field, bending of the Isthmus of Panama, shearing in eastern Panama, or minor deformation of the Panama Block above the Caribbean subduction zone. For seismic hazard analysis of the northern canal area, these faults led us to include a source zone of shallow faults proximal to northern canal facilities. 相似文献
4.
鄂尔多斯盆地西缘作为南北构造带的一部分,不仅是研究该盆地形成、演化及油气成藏的重要窗口,也是探讨中生代特提斯洋关闭、新生代青藏高原隆升的热点地区。本文将盆地西缘中部及以东的新生界覆盖区作为一个整体,利用二维和三维地震资料进行精细构造解释,在天环坳陷中生界发现大量微小断层。地震解释表明：地震剖面上,微小断层具有正、逆断层并存,切穿层位差异大,挤压褶皱相伴生的特点;平面上,微小断层呈北西西—南东东向规律性展布,与西部前缘带的大型断层共同构成扫帚状展布的断层发育带。晚侏罗世燕山运动主幕,北东东向构造挤压应力由南向北传递,由于受东西向横向构造转换带的阻挡,在本区产生压扭作用,微小断层的形成受此压扭作用控制。微小断层形成后,主要经历了早白垩世伸展作用和晚白垩世—至今的后期改造。依据断层切穿的层位及改造阶段,将微小断层划分为3个期次,井震联合分析认为：Ⅰ期断层主要改善了延长组致密储层的物性,一般在延长组内部成藏;Ⅱ期断层主要促进了石油的运移,在延长组和延安组均能成藏;Ⅲ期断层对早期油藏具有一定的破坏作用。 相似文献
5.
古新世以来郯庐断裂的位移量及其对莱州湾凹陷的控制 总被引：4，自引：2，他引：2
高分辨三维地震可视化及方差切片分析显示,郯庐断裂渤海海域莱州湾段北北东向断裂系发育。断层在水平方差切片上的拖拽现象、断裂带内部断层的组合关系以及凹陷沉积中心的迁移等,表明古新世以来该区存在右旋走滑运动。假设在东、西两支断层的走滑拉分作用下,根据可容纳空间不变原理,设计了三角形模型、长方形模型、半地堑型模型以及地堑型模型共四种模型,计算莱州湾凹陷南北长度和凹陷深度的关系,其中半地堑模型计算得到的郯庐断裂的水平位移为7km。结合断层的平面分布和断层的切割关系,表明古新世以来郯庐断裂的走滑拉分作用难以控制莱州湾凹陷的形成,走滑拉分作用只是在走滑断裂带内部形成了局部小型洼地,其规模很小,影响非常有限。 相似文献
6.
通过认真、系统的地震资料解释, 我们在塔里木盆地西南坳陷首次发现晚新生代正断层。 这些正断层发育于西南坳陷的东北部, 走向 NE-SW, 剖面上组合成堑垒构造, 个别剖面上显示负花状构造特征。 正断层主要发育于新生界, 向上断至的最高层位是第四系更新统下部。 倾向相反的正断层向下交汇后断距消失, 断层继续向下延伸的情况不清楚。 根据断距 变化和生长指数计算, 正断层形成于上新世晚期, 持续演化至更新世早期。 正断层的形成演化过程与以往在阿瓦提凹陷、巴楚隆起和塘沽孜巴斯坳陷发现的晚新生代正断层基本一致, 正断层活动时间为 ca. 3～2 Ma。 它们形成于一个区域性弱伸展构造应力场, 代表印度-亚洲碰撞远程效应下, 塔里木盆地脉式挤压冲断过程中的一个构造间歇期。 相似文献
7.
琼东南盆地东部层间断层系及其形成机制分析 总被引：1，自引：1，他引：0
基于琼东南盆地最新3D地震资料的地质与地球物理解释,运用先进的地震剖面相干处理技术,在琼东南盆地东部早-中中新世泥岩中发现了大量层间断层,这些断层剖面上为板状正断层,倾角一般大于45°,长度不超过1000m,但是平面走向在不同区域差异很大。研究区层间断层为以体积收缩机制为主要形成机制,在区域应力、重力滑塌和超压水力破裂多种力学机制共同影响下形成的,基本限制在层间的、多种类型和多种性质的断层组合。研究区东北部主要为体积收缩机制形成的层间断层,并受到重力滑塌的影响,断层主要表现为平行于等深线的EW向的断层密集带和与之垂直的SN向直线状断层;中部主要受超压水力破裂作用和体积收缩机制的影响,断层主要由放射状断层和与之垂直的层间断层两部分组成;西南部地区主要受体积收缩作用和区域应力场的影响,在构造断层影响区,层间断层走向与构造断层相互垂直,未影响区则表现为断层多边形。 相似文献
8.
In intra-plate regions with low-seismic activity, seismic cycles last between 103 and 105 years and, consequently, quiescent faults may be capable of producing catastrophic earthquakes. Paleoseismic studies, which
are necessary to define capable faults in these regions and to establish their seismic parameters, are scarce and not always
possible. In order to overcome the scarcity of paleoseismic data, this paper proposes an approach to evaluate the capability
and seismic parameters of faults. This approach takes into account instrumental, historical, paleoseismological and geological
data. Assuming that in a given structural region with definite climatic and geological characteristics similar geomorphic
features reflect a similar structural-seismic evolution, the capability of faults is established by comparing the fault related
geomorphic features of the few proven seismogenic faults with those of the rest of the faults. The seismic parameters were
estimated using some mathematical relationships from geological and geomorphological data, where the slip rate of the faults
was determined from geological and geomorphological criteria. The case of eastern Iberia is presented to illustrate this approach.
This area is characterized by low seismicity, few historical destructive earthquakes, and only one fault with good paleoseismological
data. Of the 249 potential faults (longer than 10 km and adequately oriented with respect to the current stress field), 23
were regarded as capable faults. Some of these were located in seismic quiescent areas, and their main seismic parameters
were estimated. 相似文献
9.
在党的鼓足干勁、力争上游、多次好省地建設社会主义总路線照耀下,全国各項建設事業都处在躍进的高潮中。在这种形势推动下,地質科学事业正以万馬奔騰之势向前發展。“向深山要宝,向地球开战”的口号正响徹祖国的原野和边疆。这种波瀾壯閥的新局面,使我們相信,經过各方面的努力,在不久的將来,埋藏在地下几亿年的矿藏要被唤醒,要听我們使唤,为我們服务。那时,地质工作將会为国家生产建設准备更充足的矿产资源,和为地区开發提供必要的数据,“地质工作落后”的帽子就要丢掉,从而赶上和超过英、美等先进资本主义国家的水平。 相似文献
10.
11.
The spatial properties of events in the 1997 Colfiorito–Sellano seismic sequence (Northern Apennines, Italy) were investigated using coherence, a parameter derived from seismic moment tensors that quantifies the kinematic similarity between focal mechanisms. The 1997 Colfiorito–Sellano seismic sequence predominantly consists of normal faulting earthquakes, with a few strike-slip and reverse faulting episodes. This kinematic heterogeneity is possibly related to the contemporaneous activity of two different sets of faults: NW–SE normal faults and NNE–SSW sub-vertical faults, the latter inherited from the previous Miocene compressional phase. The study used two independently-derived data sets of the same seismic sequence characterized by a different number of events and by different precision of spatial localisation. Their statistical significances, assessed through a reshuffling procedure, reveal that data sets with at least some hundreds of events and good positional precision are required to obtain significant results through coherence analysis. Results from the better quality data set indicate that this seismic sequence is characterized by a rapid decrease in the kinematic similarity between earthquake pairs within 2 km of separation, particularly along directions sub-perpendicular to the normal fault strike. The decrease rate seems to be controlled by the geometric characteristics of the normal faults, given that the mean along-dip distance between fault segments is 2 km. In proximity to pre-existing tectonic lineaments the relative abundance of strike-slip and reverse faults tends to decrease the kinematic similarity between events but does not influence the coherence decrease rate. The presence of mixed focal mechanisms (normal, reverse and strike-slip) in a single seismic phase implies that mixed fault types are not restricted to polyphase tectonic histories: such heterogeneous kinematics during a single phase may be induced by the presence of inherited discontinuities. 相似文献
12.
淮南矿区十多年来开展的煤矿采区三维地震面积达到254.56 km2,占井田面积的46.14%。通过对以往三维地震成果1 030个验证点的统计分析,拟定了三维地震成果验证准确率的评价标准;据此得出常规三维地震勘探对13-1煤层中3 m以上断层解释的准确率达62.38%,11-2煤层中2 m以上断层解释合格率约46.74%;而高密度三维地震勘探对11-2煤层中2 m以上断层解释的准确率达到85.71%。结合实例研究,分析了小断层、煤层变薄区在三维地震资料上的显示特征与探采对比效果。 相似文献
13.
通过汶川地震震区大量的实地考察已证实沿着早先活动断裂主要发育了两条地表破裂带：一条是沿着映秀－北川断裂产生的逆冲伴随右旋走滑破裂带,长275km,最大垂直位移达11m,水平位移达12m; 另一条纯逆冲性质的破裂带,沿着灌县－安县断裂发育,最大垂直位移达4m。活动断裂之上的地表破裂带是野外工作中确定地震断裂性质的重要现象。另外,在活动断裂相邻区域和远离区域的路面以及建筑体还大量存在变形现象。通常沿活动断裂产生的地表破裂是典型的同震破裂,相邻区域的地表路面及建筑体发育的变形属于次生变形,远离区域发育的变形则属于震后变形。对次生变形和震后变形测量数据的应用容易影响活动断裂特征的确定和性质的判断,因为路面等建筑体上的挤压拱起、叠置以及水平错断等现象多是受到地震过程中通过断裂活动突然释放的巨大能量作用在局部地表建筑体产生的变形。但是,分布广泛的挤压现象暗示了区域上挤压应力场环境,有利于地表同震破裂位置的推测及地震断裂性质的判断。 相似文献
14.
可靠地划分地震区可奠定地震预测与地震危险性评价的地质基础,具有十分重要的意义。笔者等通过研究分析指出板内孕震构造块体侧向边界可由区域性大断层或由区域性大断层与板块边界界定,底边界为康拉德面或低速高导层;板间孕震构造块体为俯冲板块,可由区域性大断层和(或)板块边界约束;在同一个孕震构造块体和同一轮地震周期的地震具有内在联系。因此,地震区可定义为代表相应孕震构造块体地震活动的区域,其可表征该块体内源自锁固段破裂的地震活动。基于笔者等提出的孕震构造块体和相应地震区边界确定原则,把全球两大地震带(环太平洋地震带和欧亚地震带)划分为62个地震区;每个地震区的分区方案均通过了多锁固段脆性破裂理论的检验,这说明方案可靠。进而,笔者等归纳总结了地震区划分方法。 相似文献
15.
The shallow subsurface structures of the offshore Nile Delta particularly in the southeastern Mediterranean were dealt through the interpretation of 40 two-dimensional seismic reflection lines. The interpretations of seismic reflection data indicated that the principle sedimentary processes affecting the study area include three main structural groups according to their origin and development. The first group of structures comprises of gravity-driven structures, which include slides, slumps, turbidities, and debris flow. Slides are present in three different forms on seismic sections: slide sheets, slides with scar, and wedges of slide materials. Slumps have many geometrical shapes: lenses, spoon-shaped slumps, and slumped blocks bound by growth faults. Debris flows are present as transparent unit (due to the dispersion of seismic waves at debris boundaries), whereas turbidities appear on the seismic profiles, which are formed of closely spaced parallel thin reflectors analogous to their thin stratified bedded layers. The second group of structures is syn-depositional structures, which include growth faults, and tilted and rotated fault blocks. Growth faults are listric in shape and usually dip seaward; displacements along the fault plane increase with depth. Some of these faults are incipient, and some are complicated and intersected by secondary antithetic faults. Most of the growth faults soles out basin wards and in the evaporites layer. Fault blocks are formed due to the Messinian evaporite movement vertically and horizontally due to its mobility as a consequence to the pressure resulted from the overloading of Pliocene sediment. The third group of structures comprises evaporite flow structures such as diapiric structures and graben collapse structures. The surface of the Messinian evaporites was folded during its flow as a consequence to the lateral compression acted on the mobile strata of the Messinian evaporites to form diapiric triangular structures and creates a stress zone faulting and fractures system. These conditions led to the formation of collapse structures or graben collapse structures. 相似文献
16.
Low-angle detachment faults are key to our understanding of the tectonic evolution of magma-poor rifted continental margins. In seismic images of present-day rifted margins the identification and interpretation of such features is, however, notoriously difficult and ambiguous. We address this problem by studying the structure and seismic response of such faults through a synoptic interpretation of petrophysical data and geological evidence from the distal segments of the present-day West Iberian and the ancient Tethyan margins. On the basis of the geologically well-constrained remnants of the Tethyan margins, which are spectacularly preserved and exposed in the Alps of Eastern Switzerland, vertical profiles at four key geological settings of a typical magma-poor rifted margin are constructed and their synthetic seismic responses are compared to the observed seismic data from corresponding locations in the present-day Iberian margin. The seismic structure of these profiles is considered as the sum of deterministic large-scale and the stochastic small-scale components. Both components are analyzed for all pertinent lithologies. The large-scale structures are derived from laboratory measurements on samples from both, the West Iberian and Tethyan margins, whereas the small-scale fluctuations are constrained predominantly on the basis of well-log data from the Iberian margin. Different realizations of the simulated stochastic small-scale velocity fluctuations illustrate the potential variability of impedance contrasts and its impact on the seismic response from lithological interfaces and fault structures. Our results indicate that the nature of the seismic response from low-angle detachment faults is largely determined through the fracture-healing behavior of the surrounding rocks. Geological evidence from the exposed fragments of the Tethyan margins indicate that fracture-healing is generally well developed in crustal lithologies, but largely absent in mantle lithologies. It is for this reason that low-angle, intra-crustal detachment faults tend to be seismically undetectable. Conversely, crust–mantle detachments have a complex and variable seismic response, depending on the nature of the damaged zone and on the frequency content of the seismic data. These model-based inferences are consistent with the available evidence from the present-day Iberian passive margin and thus open new perspectives for the interpretation of the corresponding seismic images. 相似文献
17.
Geological deformation in the northern New Madrid seismic zone, near Olmsted, Illinois (USA), is analyzed using integrated compressional-wave (P) and horizontally polarized-wave (SH) seismic reflection and regional and dedicated borehole information. Seismic hazards are of special concern because of strategic facilities (e.g., lock and dam sites and chemical plants on the Ohio River near its confluence with the Mississippi River) and because of alluvial soils subject to high amplification of earthquake shock. We use an integrated approach starting with lower resolution, but deeper penetration, P-wave reflection profiles to identify displacement of Paleozoic bedrock. Higher resolution, but shallower penetration, SH-wave images show deformation that has propagated upward from bedrock faults into Pleistocene loess. We have mapped an intricate zone more than 8 km wide of high-angle faults in Mississippi embayment sediments localized over Paleozoic bedrock faults that trend north to northeast, parallel to the Ohio River. These faults align with the pattern of epicenters in the New Madrid seismic zone. Normal and reverse offsets along with positive flower structures imply a component of strike-slip; the current stress regime favors right-lateral slip on northeast-trending faults. The largest fault, the Olmsted fault, underwent principal displacement near the end of the Cretaceous Period 65 to 70 million years ago. Strata of this age (dated via fossil pollen) thicken greatly on the downthrown side of the Olmsted fault into a locally subsiding basin. Small offsets of Tertiary and Quaternary strata are evident on high-resolution SH-wave seismic profiles. Our results imply recent reactivation and possible future seismic activity in a critical area of the New Madrid seismic zone. This integrated approach provides a strategy for evaluating shallow seismic hazard-related targets for engineering concerns. 相似文献
18.
李玉新 《沉积与特提斯地质》2006,26(3):67-71
地震相干技术主要应用在断层和沉积相的解释中,确定有利储层沉积相带,正确指导油田的勘探与开发工作。本文着重论述了地震相干技术在断层与沉积相解释中的应用,研究发现当存在断层、地层岩性突变和特殊地质体时,相干图将展现出不同的相干特征,准确识别出现的地质现象。 相似文献
19.
川西前陆盆地南部莲花山区地震剖面构造解释及构造特征研究 总被引：1，自引：0，他引：1
通过详细的地震剖面解释,结合川西前陆盆地演化史,阐明莲花山地区地下断层及褶皱的几何形态及特征。认为区内部分断层是继承先成断层发育而来,部分断层是喜马拉雅期运动的产物;部分断层存在断层反转现象;控制盆地内沉积的主要因素是几个大断层。 相似文献
20.
Reliable fault plane solutions of shallow earthquakes and information on surface fault traces in combination with other seismic, geomorphological and geological information have been used to determine the orientation and other properties of the seismic faults in the Aegean and surrounding area.Thrust faults having an about NW-SE strike occur in the outer seismic zone along western Albania-westernmost part of mainland of Greece-Ionian Sea-south of Crete-south of Rhodes.The inner part of the area is dominated by strike-slip and normal faulting. Strike-slip with an about NE-SW slip direction occurs in the inner part of the Hellenic arc along the line Peloponnesus-Cyclades-Dodecanese-southwest Turkey as well as along a zone which is associated with the northern Aegean trough and the northwesternmost part of Anatolia. All other regions in the inner part of the area are characterized by normal faulting. The slip direction of the normal faults has an about SW-NE direction in Crete (N38°E) and an about E-W direction (N81°E) in a zone which trends N-S in eastern Albania and its extension to western mainland of Greece. In all other regions (central Greece-southern Yugoslavia and Bulgaria, western Turkey) the slip of the normal faults has an about N-S direction. 相似文献