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1.
Cultrera F. Barreca G. Burrato P. Ferranti L. Monaco C. Passaro S. Pepe F. Scarf&#; L. 《Natural Hazards》2016,86(2):253-272
The Gulf of Patti and its onshore sector represent one of the most seismically active regions of the Italian Peninsula. Over the period 1984–2014, about 1800 earthquakes with small-to-moderate magnitude and a maximum hypocentral depth of 40 km occurred in this area. Historical catalogues reveal that the same area was affected by several strong earthquakes such as the Mw = 6.1 event in April 1978 and the Mw = 6.2 one in March 1786 which have caused severe damages in the surrounding localities. The main seismotectonic feature affecting this area is represented by a NNW–SSE trending right-lateral strike-slip fault system called “Aeolian–Tindari–Letojanni” (ATLFS) which has been interpreted as a lithospheric transfer zone extending from the Aeolian Islands to the Ionian coast of Sicily. Although the large-scale role of the ATLFS is widely accepted, several issues about its structural architecture (i.e. distribution, attitude and slip of fault segments) and the active deformation pattern are poorly constrained, particularly in the offshore. An integrated analysis of field structural geology with marine geophysical and seismological data has allowed to better understand the structural fabric of the ATLFS which, in the study area, is expressed by two major NW–SE trending, en-echelon arranged fault segments. Minor NNE–SSW oriented extensional structures mainly occur in the overlap region between major faults, forming a dilatational stepover. Most faults display evidence of active deformation and appear to control the main morphobathymetric features. This aspect, together with diffused continental slope instability, must be considered for the revaluation of the seismic and geomorphological hazard of this sector of southern Tyrrhenian Sea.
相似文献2.
Oblique rifting in Salina, Lipari and Vulcano islands (Aeolian islands, southern Italy) 总被引：1，自引：0，他引：1
A structural analysis carried out on the volcanic products of the islands of Salina, Lipari and Vulcano (Aeolian archipelago) points out that the large-scale tectonic setting is dominated by NW-SE trending right-lateral extensional strike-slip faults and by N-S to NE-SW trending normal faults and fractures. This fault pattern generates pull-apart type structures, developing between different right-hand overlapping fault segments and a characteristic extensional imbricate fan geometry at the tip of the major strike-slip faults. All the structures, representing the surface expression of an active crustal discontinuity which controls the evolutionary history of the magmatism of the three islands, are kinematically compatible with a N100°E extension related to a rifting process affecting southern Italy. 相似文献
3.
通过收集整理前人成果资料,结合湖南、湖北地区地震地质特征、历史近代地震数据等,全面梳理分析该区主要活动断裂及历史地震,总结该区主要活动断裂系（带）及控震特征、地震活动性及时空分布特征。研究结果表明,该区主要活动断裂以北东、北北东、北西向为主,主要活动断裂系有6个,自北向南分别为秦昆北西向断裂系、鄂东北东向断裂系、江汉-洞庭盆地断裂系、鄂西-湘西北东向断裂系、湘中南北东向断裂系、湘东北东向断裂系,其中第四纪活动较为显著且影响程度大的是江汉-洞庭盆地断裂系及秦昆北西向断裂系西段。“两湖”地区地震活动水平相对较低,正处于第三活动期的相对平静期。结合近代中强震资料及中国地震烈度区划特征分析认为,江汉-洞庭盆地南部的东、西边界、鄂州-黄冈-武汉一带以及鄂西北断块隆起区地壳较不稳定,具有发震潜力,应在城市群规划建设、护江大堤设防和重大工程建设中予以特别关注。 相似文献
4.
Examination of damages affecting the buildings of the archaeological sites of Phaistos and Agia Triada (southern Crete) suggests that these Minoan settlements were probably destroyed by two major seismic events characterized by MKS intensities of IX–X and occurred at the end of the Protopalatial (1700 BC) and the Neopalatial (1450 BC) periods. Geological and morphological studies carried out in the neighbouring areas show the occurrence of E–W trending Quaternary normal fault segments (Spili and Agia Galini faults) that control the present topography and morphology, and exhibit steep young scarps mostly Holocene in age. These fault segments are related to a NW–SE extension direction, which is consistent with that indicated by the available focal mechanisms of the earthquakes occurring in this area in the last 50 years. Combining structural and seismic data we can infer that the Spili and Agia Galini fault segments could represent good candidates to be considered active faults generating large earthquakes (M6.5) that were responsible for the damages of Phaistos and Agia Triada. This hypothesis suggests that the Minoan palatial centres were destroyed by several large earthquakes related to ruptures along distinct fault segments rather than by a single catastrophic event that caused the abrupt destruction of the Minoan civilisation in the eastern Mediterranean. 相似文献
5.
P. J. Lyon P. J. Boult R. R. Hillis K. Bierbrauer 《Australian Journal of Earth Sciences》2013,60(5):675-689
The Penola Trough is an intensely faulted northwest – southeast-trending half-graben structure. It is bound to the south by the major listric Hungerford/Kalangadoo Fault system. Several large prominent faults observed in the Penola Trough show offset of basement at depth. These basement-rooted faults have exerted significant controls on the geometry of smaller intra-rift faults throughout the entire structural history of the area. Faulting of the basement was initiated during the initial rift event of the Late Jurassic – Early Cretaceous. Faulting first propagated through a pre-existing basement fabric oblique to the north – south extension direction prevalent during this time. This resulted in the formation of the Hungerford/Kalangadoo and St George Faults with a northwest – southeast and north-northeast – south-southwest trend, respectively. A series of east – west-trending basement faults subsequently initiated perpendicular to the north – south extension direction as extensional strain increased in magnitude. Significant displacement along these basement-rooted faults throughout the initial rift event was associated with the formation of a complex set of intra-rift faults. These intra-rift faults exhibit a broadly east – west orientation consistent with the interpreted north – south extensional direction. However, this east – west orientation locally deviates to a more northwest – southeast direction near the oblique-trending St George Fault, attributed to stress perturbation effects. Many of the intra-rift faults die out prior to the end of the Early Cretaceous initial rift event while displacement on basement faults continued throughout. Faulting activity during the Late Cretaceous post-rift fault event was almost exclusively localised onto basement faults, despite a significant change in extension direction to northeast – southwest. A high-density, en échelon array of northwest – southeast-trending fault segments formed directly above the St George Fault and the large east – west-trending basement faults contemporaneously reactivated. Seismic variance data show that post-rift fault segments that are hard-linked to the St George Fault at depth have propagated through near-surface units. Non-basement-linked post-rift fault segments that lie away from the St George basement have not. This suggests that recent fault activity has continued to occur preferentially along basement faults up to relatively recent times, which has significant implications for fault seal integrity in the area. This is empirically validated by our structural analysis of fault-dependent hydrocarbon traps in the area, which shows that partially breached or breached hydrocarbon columns are associated with basement faults, whereas unbreached hydrocarbon columns are not. 相似文献
6.
Abu-Dabbab area is the most active seismic zone in the central Eastern Desert of Egypt, where seismic activities are daily recorded. The reported earthquakes are microearthquakes of local magnitudes (ML < 2.0). A spatial distribution of these microearthquakes shows that the earthquakes of the area follow an ENE–WSW trending pattern, which is nearly perpendicular to the Red Sea Rift. Focal mechanisms of different fault styles were recognized with dominant normal faulting (with a strike-slip component) events characterized by focal depths greater than 7 km and reverse ones of shallower focal depths. Several lines of evidence indicating that the brittle-ductile transition zone underlies the Abu-Dabbab area occurs at a relatively shallow depth (10–12 km) and it is acting as a low-angle normal shear zone (LANF). Field-structural, EMR and seismic data (this study) reveal that the maximum compressive stress (σ1) in the area is perturbed from the regional NW–SE direction to ENE–WSW orientation. This stress rotation is evidently akin to the reactivation of the crustal scale Najd Fault System (NFS), where such reactivation is attributed to the ongoing activity/opening of the Red Sea. Our tectonic model proposes that the continuous activity on the brittle-ductile transition zone including the LANF led to stress localization, which triggering a brittle deformation in the upper crustal-levels and associated shallow dipping thrusts. Such bimodal tectonic model suggests that the deep earthquakes are owing to the tectonic movement on the LANF (transtension), whereas the shallow earthquakes are related to a brittle deformation inside the fault blocks of the upper crust (transpression). Deformation creep along this zone didn’t permit continuous accumulation of strain and hence reduce the possible occurrence of large earthquakes. 相似文献
7.
To better understand how active deformation localizes within a continental plate in response to extensional and transtensional tectonics, a combined analysis of high-quality gravity (Bouguer anomaly) and seismicity data is presented consisting of about 35000 earthquakes recorded in the Baikal Rift Zone. This approach allows imaging of deformation patterns from the surface down to the Moho. A comparison is made with heat flow variations in order to assess the importance of lithospheric rheology in the style of extensional deformation. Three different rift sectors can be identified. The southwestern rift sector is characterized by strong gravity and topography contrasts marked by two major crustal faults and diffuse seismicity. Heat flow shows locally elevated values, correlated with recent volcanism and negative seismic P-velocity anomalies. Based on earthquake fault plane solutions and on previous stress field inversions, it is proposed that strain decoupling may occur in this area in response to wrench-compressional stress regime imposed by the India–Asia collision. The central sector is characterized by two major seismic belts; the southernmost one corresponds to a single, steeply dipping fault accommodating oblique extension; in the centre of lake Baikal, a second seismic belt is associated with several dip-slip faults and subcrustal thinning at the rift axis in response to orthogonal extension. The northern rift sector is characterized by a wide, low Bouguer anomaly which corresponds to a broad, high topographic dome and seismic belts and swarms. This topography can be explained by lithospheric buoyancy forces possibly linked to anomalous upper mantle. At a more detailed scale, no clear correlation appears between the surficial fault pattern and the gravity signal. As in other continental rifts, it appears that the lithospheric rheology influences extensional basins morphology. However, in the Baikal rift, the inherited structural fabric combined with stress field variations results in oblique rifting tectonics which seem to control the geometry of southern and northeastern rift basins. 相似文献
8.
浙江杭州地区孝丰—三门湾断裂晚第四纪活动性研究 总被引：1，自引：0，他引：1
北西走向的孝丰—三门湾断裂是浙北地区一条重要的断裂。该断裂第四纪以来表现为左旋走滑,并水平断错了北东走向的萧山—球川断裂和东西走向的昌化—普陀断裂。这三条断裂交汇于杭州地区并造成了钱塘江的拐弯。在孝丰—三门湾断裂与北东走向断裂的交汇处曾有多次地震发生。通过在孝丰—三门湾断裂（杭州段）上布设的4 个探槽,发现该断裂附近存在一系列近于东西走向及北东走向的晚更新世活动断裂。这些断层活动可能是由孝丰—三门湾主干断裂的活动引起的,并调节着孝丰—三门湾主干断裂的活动,减弱断裂附近应力,降低区域地震危害性。采用了光释光（OSL）测年方法来限定断层活动时代,并采用孢粉测年对OSL 年龄进行验证。依据OSL 年龄,探槽所揭露的断层活动均发生距今1.65 万年之前,存在两次断层活动,分别发生于1.65~1.97 万年和4.2~5.12 万年。孝丰—三门湾断裂在晚更新世有所活动的认识对于杭州地区乃至整个浙北地区未来的地震危险性评价具有重要的意义。 相似文献
9.
Francisco Gutiérrez Eulàlia Masana Álvaro González Pedro Lucha Jesús Guerrero James P. McCalpin 《International Journal of Earth Sciences》2009,98(7):1691-1703
The Munébrega Plio-Quaternary half-graben is a NW-SE trending neotectonic depression located in the central sector of the intraplate Iberian Range (NE Spain). The master fault of the half-graben offsets an Upper Pleistocene pediment deposit, forming an upslope-facing scarp. A trench dug across the fault scarp exposed a 25-m wide deformation zone consisting of graben and horst fault blocks with fissures in the upper part of the scarp, and a monoclinal flexure affected by normal and reverse faults in the lower part of the scarp. We infer a minimum of three faulting events over the past 72 ka, yielding an average (maximum) recurrence interval of 24 ka. The oldest event (72–41 ka) produced an antislope scarp on the relict pediment surface, confining deposition to the downthrown block. Cross-cutting faults affecting sedimentary units deposited in the sediment trap produced by the first event provide evidence for at least two younger events (33–19? ka). The measured cumulative vertical displacement (7.4 m) yield a minimum vertical slip rate of 0.10 ± 0.01 mm/year (2σ error) for the past 72 ka. If the paleoearthquakes ruptured the whole mappable length of the fault (ca. 20 km), they probably had moment magnitudes ca. 6.9 (Stirling et al. Bull Seismol Soc Am, 2002). Such earthquakes would have been more than a magnitude unit larger than the largest ones recorded historically in the Iberian Range. These results suggest that the official seismic hazard assessments, based solely on the historic and instrumental record, may underestimate the seismic hazard in the area. 相似文献
10.
In the past two decades, several publications have been presented concerning the recent and active fault geometry, kinematics and geodynamics of the Aegean Region and particularly of the northern sector. Data and results are often contradictory and because of the complexity of the area most hypotheses and models should be considered carefully. The right-lateral movement of the North Anatolia Fault continues into some branches of the North Aegean fault system. There, strike-slip motion along NE–SW trending faults coexists with dip-slip E–W trending faults in the frame of an extensional regime related to N–S crustal stretching. If we take into account the geodynamic environment of the region, several mechanical problems arise. To the east, the Aegean is compressed by the westward convergence of Anatolia, while to the south and west along the Hellenic Arc, a hemiradial compression occurs due to subduction. Although the North Anatolia–North Aegean Trough fault system resembles a restraining bend, the whole area is in fact affected by pure extension and local transtension, along NE–SW trending structures. Accordingly, the major paradox of the area and especially in the western sector (fault termination?) is the occurrence of extension where compression should regionally, or at least locally, predominate. 相似文献
11.
The Holocene Activity Evidence of the Yema River-Daxue Mountain Fault in Western Qilian Mountain 总被引：2，自引：0，他引：2
Altyn Tagh fault controls the deformation characteristics of the northern margin of the Qinghai-Tibet Plateau.The sinistral slip rate of the eastern segment of the fault reduces gradually where the reduction transforms into the deformation within Qilian Mountain,forming a series of thrust faults and strike-slip faults.Among them,the Yema River-Daxue Mountain fault is one of the important structural transform faults in the study area.Based on the differences of the geometrical characteristics and activities,the fault is divided into four segments,the Yema River segment,the Shibandun segment,the Liushapo segment and the Baishitougou segment,among which the former three are Holocene active faults,and the Baishitougou segment belongs to late Pleistocene fault.The excavated trenches imply a total of 6 paleoearthquake events,and at least 4 events have occurred during Holocene,whose occurrence times are 8300±700 yr BP,6605±140 yr BP,4540±350 yr BP,2098±47 yr BP,respectively.The recurrence interval is 2600±600 yr BP that is close to the lapsed time of the last one,2098±47 yr BP,which suggests that the Yema River-Daxue Mountain fault is in a high risk of major earthquakes in the future.The vertical coseismic displacements of the four Holocene paleoearthquake events are 100 cm,42 cm,40 cm and 50 cm,respectively,the horizontal coseismic displacements are 5 m,4.5-5.5 m,5-8 m and 4-5.5 m,separately,and then the reference magnitude of the paleoearthquake events is conjectured to be M7.6±0.1. 相似文献
12.
Erman Özsayın 《Geodinamica Acta》2016,28(4):241-253
Western Anatolia is one of the world’s most seismically active regions. A nearly N–S-oriented extension caused the formation of E–W- and NE–SW-trending major grabens, creating the potential for earthquakes with magnitudes ≥ 5. The fault segments of the NE-trending Çameli Basin were evaluated using geomorphic indices, common tools for assessment of relative tectonic activity in such areas. Quantitative measurement of geomorphic indices including mountain-front sinuosity (Smf; 1.35–2.39), valley floor width-to-height ratios (Vf; 0.08?0.37), and hypsometric integral (HI; 0.31–1.05) suggest relatively higher tectonic activity along western and southern part of the basin. Hypsometric curves for all segments of the faults mostly exhibit concave or straight profiles, signifying existence of young mountain fronts in the Çameli Basin. These calculations indicate that the Çameli Basin is tectonically active and, southern/south-western areas of this depression have earthquake potential, consistent with epicentres of recent earthquakes, occurred along some fault segments. Possible reason of this activity seems to be related to the E–W-trending corridor lying between the Gulf of Gökova and south-eastern part of the Çameli Basin, represented by active normal faults. These findings should be valid beyond the Çameli Basin for similar situations along the Isparta Angle’s western margin. 相似文献
13.
Marco Bonini Chiara Tanini Giovanna Moratti Luigi Piccardi Federico Sani 《第四纪科学杂志》2003,18(8):695-708
This paper examines the morphotectonic and structural–geological characteristics of the Quaternary Martana Fault in the Umbria–Marche Apennines fold‐and‐thrust belt. This structure is more than 30 km long and comprises two segments: a N–NNW‐trending longer segment and a 100°N‐trending segment. After developing as a normal fault in Early Pleistocene times, the N–NNW Martana Fault segment experienced a phase of dextral faulting extending from the Early to Middle Pleistocene boundary until around 0.39 Ma, the absolute age of volcanics erupted in correspondence to releasing bends. The establishment of a stress field with a NE–ENE‐trending σ3 axis and NW–NNW σ1 axis in Late Pleistocene to Holocene times resulted in a strong component of sinistral faulting along N–NNW‐trending fault segments and almost pure normal faulting on newly formed NW–SE faults. Fresh fault scarps, the interaction of faulting with drainage systems and displacement of alluvial fan apexes provide evidence of the ongoing activity of this fault. The active left‐lateral kinematic along N–NNW‐trending fault segments is also revealed by the 1.8 m horizontal offset of the E–W‐trending Decumanus road, at the Roman town of Carsulae. We interpret the present‐day kinematics of the Martana Fault as consistent with a model connecting surface structures to the inferred north‐northwest trending lithospheric shear zone marking the western boundary of the Adria Plate. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
14.
G. Iovine I. Guagliardi C. Bruno R. Greco A. Tallarico G. Falcone F. Lucà G. Buttafuoco 《Natural Hazards》2018,91(1):193-219
Soil-gas radon concentrations and exhalation rates have generally been observed to be anomalously high along active faults in many parts of the world. The soil-gas method is based on the principle that faults and fractures in rocks are highly permeable pathways along which gases can migrate upward from deep crust and mantle to soil cover, retaining their source signatures. The present study summarizes the influence of fault zones on anomalous radon concentrations in soil by integrated geophysical and geo-structural analyses in three study areas of Central-Northern Calabria (Southern Italy). Soil-gas radon surveys have been carried out by means of an alpha scintillation counting system, at 12,509 locations between 2002 and 2004. A geostatistical approach has been used to estimate the spatial distribution of soil radon concentrations. Relations among soil-gas distribution and geo-structural features have been evaluated by ordinary multi-Gaussian kriging. Highest soil radon concentrations (ca. 90 kBq m?3) have been measured in the Rossanese sector. In the three study areas, no appreciable differences can be noticed among lithotypes, with the highest concentration values (ca. 89 kBq m?3) measured in alluvial deposit and in clay. Measurements of soil-gas radon reveal anomalies clearly connected to the tectonic structures. Increased signals are linearly distributed along regional WNW–ESE trending shear zones, with main pathways of concentration also recognizable along the E–W fault system in the Rossanese sector, the N–S fault system in the Crati Graben and the Catanzaro Trough, and the NE–SW fault system in the Catanzaro Trough. The distribution of epicentres of historical earthquakes occurred between 1184 and 2001 confirms the recent activity of the same fault systems. Soil-gas radon concentrations generally increase, as expected, with decreasing distance to the faults. 相似文献
15.
《Geodinamica Acta》2003,16(2-6):131-147
Combining fieldwork and surface data, we have reconstructed the Cenozoic structural and tectonic evolution of the Northern Bresse. Analysis of drainage network geometry allowed to detect three major fault zones trending NE–SW, E–W and NW–SE, and smooth folds with NNE trending axes, all corroborated with shallow well data in the graben and fieldwork on edges. Cenozoic paleostress succession was determined through fault slip and calcite twin inversions, taking into account data of relative chronology. A N–S major compression, attributed to the Pyrenean orogenesis, has activated strike-slip faults trending NNE along the western edge and NE–SW in the graben. After a transitional minor E–W trending extension, the Oligocene WNW extension has structured the graben by a collapse along NNE to NE–SW normal faults. A local NNW extension closes this phase. The Alpine collision has led to an ENE compression at Early Miocene. The following WNW trending major compression has generated shallow deformation in Bresse, but no deformation along the western edge. The calculation of potential reactivation of pre-existing faults enables to propose a structural sketch map for this event, with a NE–SW trending transfer fault zone, inactivity of the NNE edge faults, and possibly large wavelength folding, which could explain the deposit agency and repartition of Miocene to Quaternary deformation. 相似文献
16.
The study area is located in the south-eastern part of the Crati valley (Northern Calabria, Italy), which is a graben bordered by N–S trending normal faults and crossed by NW–SE normal left-lateral faults. Numerous severe crustal earthquakes have affected the area in historical time. Present-day seismic activity is mainly related to the N–S faults located along the eastern border of the graben. In this area, much seismically induced deep-seated deformation has also been recognised.In the present paper, radon concentrations in soil gas have been measured and compared with (a) lithology, (b) Quaternary faults, (c) historical and instrumental seismicity, and (d) deep-seated deformation.The results highlight the following:
- (a) There is no evidence of a strong correlation between lithology and the radon anomalies.
- (b) A clear correlation between the N–S geometry of radon anomalies and the orientation of main fault systems has been recognised, except in the southernmost part of the area, where the radon concentrations are strongly affected by the superposition of the N–S and the NW–SE fault systems.
- (c) Epicentral zones of instrumental and historical earthquakes correspond to the highest values of radon concentrations, probably indicating recent activated fault segments. In particular, high radon values occur in the zones struck by earthquakes in 1835, 1854, and 1870.
- (d) Deep-seated gravitational deformation generally coincides with zones characterised by low radon concentrations.
17.
Taha Rabeh 《Environmental Earth Sciences》2013,70(4):1539-1550
In this work, we present a reconnaissance study to elucidate and delineate subsurface fault structures for an active tectonics area that lies between Cairo and El Fayoum provinces and consider major sources of seismicity in Egypt. Well logging, aeromagnetic, land magnetic, and magnetotelluric data have been used. The well-logging data were used for several drilled wells along W–E direction. The magnetic data were analyzed using trend analysis, 3D magnetic modeling, and Werner deconvolution techniques. The magnetotelluric data were interpreted using 2D (TM–TE) modeling techniques. The results show that there are eight major fault structures having E–W, N–S, and NW–SE directions. These faults extend downward for about 20 km at the Dahshour and Qatrani areas. The epicenter sources of the earthquakes are clustering around the intersections of these structures. The Kattaniya horst structure has been interpreted as a regional structure that exceeds the limits previously determined by geologists. The depth to this horst reaches about 1.8 km at the NW and more than 4.3 km at the southern parts. The interpreted values of magnetic susceptibility at the horst zone indicate that they are ultrabasic/basic intrusion bodies. 相似文献
18.
Mohammad Mokhtari 《Natural Hazards》2010,52(2):351-368
Iran has long been known as one of the most seismically active areas of the world, and it frequently suffers destructive and catastrophic earthquakes that cause heavy loss of human life and widespread damage. The Alborz region in the northern part of Iran is an active EW trending mountain belt of 100 km wide and 600 km long. The Alborz range is bounded by the Talesh Mountains to the west and the Kopet Dagh Mountains to the east and consists of several sedimentary and volcanic layers of Cambrian to Eocene ages that were deformed during the late Cenozoic collision. Several active faults affect the central Alborz. The main active faults are the North Tehran and Mosha faults. The Mosha fault is one of the major active faults in the central Alborz as shown by its strong historical seismicity and its clear morphological signature. Situated in the vicinity of Tehran city, this 150-km-long N100° E trending fault represents an important potential seismic source. For earthquake monitoring and possible future prediction/precursory purposes, a test site has been established in the Alborz mountain region. The proximity to the capital of Iran with its high population density, low frequency but high magnitude earthquake occurrence, and active faults with their historical earthquake events have been considered as the main criteria for this selection. In addition, within the test site, there are hot springs and deep water wells that can be used for physico-chemical and radon gas analysis for earthquake precursory studies. The present activities include magnetic measurements; application of methodology for identification of seismogenic nodes for earthquakes of M ≥ 6.0 in the Alborz region developed by International Institute of Earthquake Prediction Theory and Mathematical Geophysics, IIEPT RAS, Russian Academy of Science, Moscow (IIEPT&MG RAS); a feasibility study using a dense seismic network for identification of future locations of seismic monitoring stations and application of short-term prediction of medium- and large-size earthquakes is based on Markov and extended self-similarity analysis of seismic data. The establishment of the test site is ongoing, and the methodology has been selected based on the IASPEI evaluation report on the most important precursors with installation of (i) a local dense seismic network consisting of 25 short-period seismometers, (ii) a GPS network consisting of eight instruments with 70 stations, (iii) magnetic network with four instruments, and (iv) radon gas and a physico-chemical study on the springs and deep water wells. 相似文献
19.
The Bekten Fault is 20-km long N55°E trending and oblique-slip fault in the dextral strike-slip fault zone. The fault is extending sub-parallel between Yenice-Gönen and Sar?köy faults, which forms the southern branch of North Anatolian Fault Zone in Southern Marmara Region. Tectonomorphological structures indicative of the recent fault displacements such as elongated ridges and offset creeks observed along the fault. In this study, we investigated palaeoseismic activities of the Bekten Fault by trenching surveys, which were carried out over a topographic saddle. The trench exposed the fault and the trench stratigraphy revealed repeated earthquake surface rupture events which resulted in displacements of late Pleistocene and Holocene deposits. According to radiocarbon ages obtained from samples taken from the event horizons in the stratigraphy, it was determined that at least three earthquakes resulting in surface rupture generated from the Bekten Fault within last ~1300 years. Based on the palaeoseismological data, the Bekten Fault displays non-characteristic earthquake behaviour and has not produced any earthquake associated with surface rupture for about the last 400 years. Additionally, the data will provide information for the role of small fault segments play except for the major structures in strike-slip fault systems. 相似文献
20.
塔里木盆地塔中Ⅰ号构造带在构造样式、活动强度等方面表现出明显的分段性,但分段变形的运动学特征与成因仍不够明确,需要开展进一步研究。本文利用二维、三维地震资料,通过精细构造解析、运动学参数统计、活动期次厘定等手段,研究了塔中Ⅰ号构造带的几何学、运动学特征,分析其分段变形机制,并讨论了分段控制因素。研究表明:以中古15井与中古21井位置为界,塔中Ⅰ号构造带构造样式、运动学特征主要呈三段的特点,西段主要活动机制是断裂短距离滑动逆冲和地层旋转变形,同一层位的落差/垂直断距(H/h)值最大;中段为断裂沿走向滑动,H/h值约为1;东段为断裂长距离滑动逆冲和强烈褶皱,H/h值介于二者之间。活动机制的差异导致各段构造样式分别为基底卷入逆冲断裂控制的断层传播褶皱、走滑断裂发育的断控坡折、逆冲断裂强烈活动控制的断块褶皱,且活动强度呈现东段最大、西段次之、中段较小的特点。两大造山带分期活动是塔中Ⅰ号构造带分段变形的发育背景,基底结构与先存断裂是造成分段的主控因素,NE向走滑断裂调节塔中Ⅰ号构造带差异逆冲变形,并作为伴生断裂发育。 相似文献