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1.
Abstract Based on a field analysis of slip vectors from Cretaceous and Tertiary rocks and coupled with rift basin analysis in north China, the Cenozoic deformation history of the Tancheng–Lujiang (Tan–Lu) Fault Zone can be divided into three main phases: early Tertiary normal faulting and northwest–southeast extension; Miocene normal faulting and northeast–southwest to north‐northeast–south‐southwest extension; and Quaternary dextral strike–slip faulting and east‐northeast transpression. The early Tertiary extension, which was responsible for rift basin formation in north China, originated from back‐roll mantle convection induced by westward subduction of the Pacific Plate beneath the Asia continent. The Miocene extension occurred possibly in association with the process of the Japan Sea opening. The Quaternary dextral slip was mainly localized along the middle part of the Tan–Lu Fault Zone and resulted from the far‐field effect of the late‐stage India–Eurasia convergence. 相似文献
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Active tectonics around the junction of Southwest Japan and Ryukyu arcs: Control by subducting plate geometry and pre‐Quaternary geologic structure 
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下载免费PDF全文 Yukinobu Okamura 《Island Arc》2016,25(4):287-297
The origin of active faults in the Inner zone of the western part of Southwest Japan was explained by a decrease of the minimum principal stress and reactivation of ancient geologic structures. Although the E–W maximum principal stress in Southwest Japan due to the collision of the Southwest and Northeast Japan arcs along the Itoigawa–Shizuoka Tectonic Line is assumed to decrease westward, the density of active strike‐slip faults increases in the western margin of the Southwest Japan Arc (western Chugoku and northern Kyushu) where the subducting Philippine Sea Plate dips steeply. The E–W maximum compressional stress is predominant throughout Southwest Japan, while the N–S minimum principal stress that is presumably caused by coupling between Southwest Japan arc and Philippine Sea Plate decreases due to the weak plate coupling as the plate inclination increases under the western margin of Southwest Japan. The increase of the fault density in the western margin of the arc is attributed to a decrease of the minimum principal stress and consequent increase of shear stress. Low slip rates of the active faults in this region support the view that the westward increase of fault density is not a response to increasing maximum stress. These faults of onshore and offshore lie in three distinct domains defined on the basis of fault strike. They are defined domains I, II, and III which are composed of active faults striking ENE–WSW, NW–SE, and NE–SW, respectively. Faulting in domains I, II, and III is related to Miocene rift basins, Eocene normal faults, and Mesozoic strike‐slip faults, respectively. Although these active faults are strike‐slip faults due to E–W maximum stress, it is unclear whether their fault planes are the same as those of pre‐Quaternary dip‐slip faults. 相似文献
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New paleomagnetic data from shallow-marine sediments of the Ichishi Group suggest a clockwise tectonic rotation of Southwest Japan in the Middle Miocene. Samples have been collected from mud or tuff layers at 17 sites. Stability of remanent magnetization has been examined by using alternating field and thermal demagnetization. The polarity sequence, composed of four normal and seven reversed polarity sites, is correlated to Polarity Epoch 16 (15.2–17.6 Ma), based on micropaleontological assignment of the upper Ichishi Group to Blow's Zone N8. The mean paleomagnetic direction of the 11 sites shows an anomalous declination toward the northeast. This result suggests that Southwest Japan was subjected to a clockwise rotation through 45° since 16 Ma. The clockwise rotation can be explained by the drift of Southwest Japan associated with the spreading of the Japan Sea during the Middle Miocene. 相似文献
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Yong I. Lee 《Island Arc》2008,17(4):458-470
The currently available paleogeographic maps of the East Asia continental margin during the Mesozoic have been recast in the light of recent research results on sediments distributed in Korea and Japan. Both the Korean peninsula and the Inner zone of Southwest Japan exchanged sediment supply during the Middle to Late Mesozoic, suggestive of a close paleogeographic relationship between the two countries at the active continental margin setting. During the latest Middle to earliest Late Jurassic the Mino–Tamba trench was developed along the southeastern Korean peninsula, from which trench‐fill sediments were sourced and to which an accretionary complex was accreted. Lower Cretaceous quartz‐arenite clasts of the Tetori Group in the Hida Marginal Belt of Southwest Japan were derived from pre‐Mesozoic quartz‐arenite strata distributed in the southern central and east central Korean peninsula, suggesting that the Tetori Basin was located close to the central eastern part of the Korean peninsula at the time of deposition of quartz‐arenite clasts, contrary to conventional thought of far distance between the two areas based on paleomagnetic data. During the early Late Cretaceous radiolaria‐bearing chert pebbles and sands in the northern part of the non‐marine Gyeongsang Basin distributed in the southeastern Korean peninsula were derived from the uplifted Mino–Tamba accretionary complex distributed in southwest Japan, suggesting that the Mino–Tamba terrane was land‐connected with the eastern Korean peninsula. These new findings suggest that in contrast to conventional thought, the collage of tectonic blocks in Southwest Japan has assembled in post‐early Late Cretaceous time. 相似文献
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Emilio Rodríguez-Escudero José J. Martínez-Díaz José A. Álvarez-Gómez Juan M. Insua-Arévalo Ramón Capote del Villar 《Bulletin of Earthquake Engineering》2014,12(5):1831-1854
In this work we analyze the tectonic setting of the recent damaging seismic series occurred in the Internal Zones of the eastern Betic Cordillera (SE Spain) and surrounding areas, the tectonic region where took place the 11th May 2011 Mw 5.2 Lorca earthquake. We revisit and make a synthesis of the seven largest and damaging seismic series occurred from 1984 to 2011. We analyze their seismotectonic setting, and their geological sources under the light of recent advances in the knowledge on active faults, neotectonics, seismotectonics and stress regime, with special attention focused on the Lorca Earthquake. These seismic series are characterized by two types of focal mechanisms, produced mainly by two sets of active faults, NNW–SSE to NNE–SSW small (no larger than 20–30 km) extensional faults with some strike slip component, and E–W to NE–SW large strike slip faults (more than 50 km long) with some compressional component (oblique slip faults). The normal fault earthquakes related to the smaller faults are dominant in the interior of large crustal tectonic blocks that are bounded by the large E–W to NE–SW strike-slip faults. The strike slip earthquakes are associated to the reactivation of segments or intersegment regions of the large E–W to NE–SW faults bounding those crustal tectonic blocks. Most of the seismic series studied in this work can be interpreted as part of the background seismicity that occurs within the crustal blocks that are strained under a transpressional regime driven by the major strike slip shear corridors bounding the blocks. The seismotectonic analysis and the phenomenology of the studied series indicate that it is usual the occurrence of damaging compound earthquakes of M \(\sim \) 5.0 associated with triggering processes driven by coseismic stress transfer. These processes mainly occur in the seismic series generated by NNW–SSE to NNE–SSW faults. These mechanical interaction processes may induce a higher frequency of occurrence of this kind of earthquakes than considered in traditional probabilistic seismic hazard assessments and it should be taken into account in future seismic hazard assessments. 相似文献
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利用断层滑动资料反演构造应力张量从而确定出海原、六盘山断裂带至银川断陷的第四纪两期构造应力场 :早更新世末期以前 ,为北东—南西挤压型构造应力场 ,由此造成该地区断裂活动主要以逆断为主 ;早更新世末期至中更新世以后 ,构造应力场发生了调整 ,主压应力方向由早期的北东—南西改变为北东东—南西西 ,应力结构由挤压型转变为走滑型 ,并导致断裂活动由早期的逆断为主变为走滑为主 ,这种应力场格局一直持续至今。研究区现代构造应力场可划分为 :海原断裂带走滑应力区、六盘山逆断 -走滑混合应力区和银川断陷拉张应力区 相似文献
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《Journal of Volcanology and Geothermal Research》2005,146(4):284-306
A NNW-trending belt of alkaline mafic volcanic fields parallels the Gulf of Mexico from the U.S. border southward to Veracruz state, in eastern Mexico. Previous studies grouped this volcanism into the so-called “Eastern Alkaline Province” (EAP) and suggested that it resulted from Gulf-parallel extensional faulting migrating from north to south from Oligocene to Present. On the basis of new geologic studies, forty-nine unspiked K–Ar and two 40Ar–39Ar ages, we propose a new geodynamic model for the volcanism along the southwestern Gulf of Mexico.We studied in detail four of the six recognized fields of mafic alkaline volcanism in Veracruz state: 1) The lavas flows of Tlanchinol area (7.3–5.7 Ma), 2) the Alamo monogenetic field and Sierra de Tantima (7.6–6.6 Ma), 3) the Poza Rica and Metlatoyuca lava flows (1.6–1.3 Ma) and 4) the Chiconquiaco–Palma Sola area (6.9–3.2 Ma). Other two mafic volcanic fields may represent the continuation of alkaline volcanism to the southeast: the Middle Miocene lavas at Anegada High, offshore port of Veracruz, and the Middle to Late Miocene volcanism at the Los Tuxtlas.The existence of major Neogene extensional faults parallel to the Gulf of Mexico (i.e., ∼N–S to NNW–SSE) proposed in previous works was not confirmed by our geological studies. Elongation of volcanic necks, vent alignment, and faults mapped by subsurface data trend dominantly NE to ENE and NW to NNW. These directions are parallel to transform and normal faults that formed during the Late Jurassic opening of the Gulf of Mexico. Ascent of mafic magmas was likely facilitated and controlled by the existence of these pre-existing basement structures.Coupled with previous studies, our data demonstrate the occurrence of three magmatic episodes in Veracruz: 1) A Middle Miocene (∼15–11 Ma) episode in southern Veracruz (Palma Sola, Anegada, and Los Tuxtlas); 2) A Late Miocene to Early Pliocene (∼7.5–3 Ma) pulse of mafic alkaline volcanism throughout the study region; and 3) A Late Pliocene to Quaternary transitional to calc–alkaline volcanism in southern Veracruz (Palma Sola, Los Tuxtlas). Whereas the first and third episodes may be considered part of the subduction-related Trans-Mexican Volcanic Belt, the second pulse of mafic alkaline volcanism has a more complex origin. The absence of significant extensional faulting precludes a rift origin. We favor a model in which a transient thermal anomaly and melting of the mantle was triggered by the tearing and detachment of part of the subducted slab. 相似文献
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昌马断裂带是是青藏高原北部一条活动强烈的左旋走滑断裂带。它表现为重力、航磁、地壳厚度的综合异常梯度带，属于断面陡、切割深的超岩石圈断裂。昌马断裂带由１２条长４公里至１８公里不等的不连续的主断层和４条次级断层组成，可划分为东、中、西三大段落。断裂的水平位移和滑动速率具有分段性，全新世以来，东、中、西三段的左旋水平滑动速率分别为４．１毫米／年，２．６毫米／年和１．５毫米／年。北东东、北北西和北西西三个方向断层的位移具有分级特征，不同级别的位移具有良好的同步性。全新世以来北东东、北北西和北西西三个方向断层的水平滑动速率分别为４．１毫米／年、３．８毫米／年和２．７毫米／年。白垩纪以来，昌马断裂呈天平式运动，显示了枢纽断裂运动特征，枢纽轴位于断裂中段。昌马地震震源破裂性质及其反映的震源应力场与地震破裂带的破裂性质及其反映的构造应力场不一致。昌马地震震源机制解反映了北北西～南南东挤压，作用应力近于水平的震源应力场；昌马地震破裂带的变形组合反映了东北～南西挤压的构造应力场。昌马地震破裂带长１２０公里，分为东部正走滑段、中部逆走滑段和西部尾端破裂段，显示了多个水平位移峰值。全新世以来，沿昌马断裂发生了６次强震事件，强震复发 相似文献
10.
K. Theunissen N. L. Dobretsov A. Korsakov A. Travin V. S. Shatsky L. Smirnova and A. Boven 《Island Arc》2000,9(3):284-303
Abstract In northern Kazakhstan the WNW striking Kokchetav megamélange includes different crustal sequences with high‐pressure/ultrahigh‐pressure (HP/UHP) remnants of their 540–520 Ma subduction metamorphism. Two domains separated by the north‐east trending Chaglinka fault are distinguished. The western domain exhibits NE–SW structures within a single Kumdy–Kol megaunit of diamond‐bearing UHP metasediments and high‐temperature (HT) eclogites. The eastern domain consists of the composite Kulet megaunit with the Kulet UHP unit (coesite‐bearing metasediments, whiteschists and eclogites), the Enbek–Berlyk medium‐pressure (MP) unit (kyanite‐bearing, high‐alumina rocks with interleaved coronitic metagabbro), and ortho‐ and paragneisses with eclogites and amphibolites included. All eclogites in the eastern domain are of the relatively low temperature (LT) type. Sillimanite is common and appears after kyanite in the sheared MP unit. A regional and moderately ESE plunging linear fabric coincides with the fold‐axis of the foliation poles from the eastern domain. Whether this also reflects a regional top to the WNW transport, as inferred from the dextral strike‐slip on steeply to SSW dipping foliation, needs further study. Top to the WNW shear is shown by weakly inclined low pressure (LP) cordierite rocks that flank the eastern domain in the south. Some new 39Ar/40Ar mica cooling ages (519, 521 Ma) from the Kulet UHP micaschists reflect the same early stage evolutionary event as was previously shown for the Kumdy–Kol UHP rocks (515, 517 Ma) in the west. Similar 39Ar/40Ar ages (500, 517 Ma) are recorded by micas and amphibole that outline a top to NNW shear fabric in the non‐subducted Proterozoic basement, north of the megamélange. A 447 Ma overprint of the MP sequences is considered to reflect the strike‐slip deformation with sillimanite and the reworking of an early kyanite‐bearing tectonite. Biotites from the LP cordierite rocks yielded approximately 400 Ma 39Ar/40Ar ages. In case they reflect the WNW shear deformation, the latter is considered to be associated with a regional granite magmatism (420–460 Ma) extending south of the eastern domain. In their present different structural domains the Kulet and Kumdy–Kol UHP units display a similar early stage event. Subsequent LP deformation, which is likely to be associated with regional granite magmatism (420–460 Ma), is assumed to have obliterated any common or uniform early exhumation structure for the whole megamélange. The north‐east structured Kumdy–Kol domain is assumed to have preserved the most information about the early stage exhumation. This domain is at an angle to the regional WNW strike of the megamélange. 相似文献