浙江沿海潜在区域地震海啸风险分析   总被引：1，自引：2，他引：1  

毛献忠  祝倩  Wei Yong 《海洋学报》2015,37(3):37-45

采用COMCOT海啸模型建立三重网格模型模拟了2011年3月11日日本东北部9.0级地震引发的海啸发生、发展以及在我国东南沿海传播过程。震源附近浮标站以及浙江沿海的潮位站实测资料验证结果显示,大部分监测站首波到达时间和海啸波的计算值相差在15%以内,表明模型可较好的模拟海啸在计算域内的传播过程。研究表明日本南海海槽、冲绳海槽以及琉球海沟南部是影响浙江沿海主要的区域潜在震源,通过情景计算分别模拟3个潜在震源9.1级、8.0级和8.7级地震引发的海啸对浙江沿海的海啸风险,计算结果表明,海啸波产生后可在3~8h内传至浙江省沿岸,海啸波达1~3m,最大可达4m,此时浙江沿岸面临Ⅲ~Ⅳ级海啸风险,达到淹没至严重淹没等级。  相似文献   

Geochemical characteristics of stable isotopes from hydrothermal chimneys in the Mariana Trough, West Pacific Ocean   总被引：1，自引：0，他引：1  

吴世迎  张道建  王揆洋  陈成业  白黎明 《中国海洋湖沼学报》2000,18(4):378-384

ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｓｅａｒｃｈｅｓｏｎｓｅａ ｆｌｏｏｒｈｙｄｒｏｔｈｅｒｍａｌａｃｔｉｖｉｔｉｅｓａｎｄｈｙｄｒｏｔｈｅｒｍａｌｓｕｌｆｉｄｅｓｙｉｅｌｄｅｄｔｈｅｎｅｗｅｓｔｋｎｏｗｌｅｄｇｅａｂｏｕｔｍｏｄｅｒｎｍａｒｉｎｅｇｅｏｌｏｇｉｃａｌｅｖｏｌｕｔｉｏｎａｎｄｍｉｎｅｒａｌｉｚａｔｉｏｎｐａｔｔｅｒｎｓ.Ｓｉｎｃｅｔｈｅ 1 980ｓ,ｓｃｉｅｎｔｉｓｔｓｈａｖｅｂｅｅｎａｐｐｌｙｉｎｇｔｈｅｏｘｙｇｅｎｉｓｏｔｏｐｅｍｅｔｈｏｄｔｏｒｅｃｏｖｅｒｔｈｅｎｏｔｄｉｒｅｃｔｌｙｄｅ…  相似文献   

The potential influence of subduction zone polarity on overriding plate deformation, trench migration and slab dip angle   总被引：1，自引：0，他引：1  

W.P. Schellart   《Tectonophysics》2007,445(3-4):363-372

A geodynamic model exists, the westward lithospheric drift model, in which the variety of overriding plate deformation, trench migration and slab dip angles is explained by the polarity of subduction zones. The model predicts overriding plate extension, a fixed trench and a steep slab dip for westward-dipping subduction zones (e.g. Mariana) and predicts overriding plate shortening, oceanward trench retreat and a gentle slab dip for east to northeastward-dipping subduction zones (e.g. Chile). This paper investigates these predictions quantitatively with a global subduction zone analysis. The results show overriding plate extension for all dip directions (azimuth α = − 180° to 180°) and overriding plate shortening for dip directions with α = − 90° to 110°. The wide scatter in data negate any obvious trend and only local mean values in overriding plate deformation rate indicate that overriding plate extension is somewhat more prevalent for west-dipping slabs. West-dipping subduction zones are never fixed, irrespective of the choice of reference frame, while east to northeast-dipping subduction zones are both retreating and advancing in five out of seven global reference frames. In addition, westward-dipping subduction zones have a range in trench-migration velocities that is twice the magnitude of that for east to northeastward-dipping slabs. Finally, there is no recognizable correlation between slab dip direction and slab dip angle. East to northeast-dipping slabs (α = 30° to 120°) have shallow (0–125 km) slab dip angles in the range 10–60° and deep (125–670 km) slab dip angles in the range 40–82°, while west-dipping slabs (α = − 60° to − 120°) have shallow slab dip angles in the range 19–50° and deep slab dip angles in the range 25–86°. Local mean deep slab dip angles are nearly identical for east and west-dipping slabs, while local mean shallow slab dip angles are lower by only 4.7–8.1° for east to northeast-dipping slabs. It is thus concluded that overall, there is no observational basis to support the three predictions made by the westward drift model, and for some sub-predictions the observational basis is very weak at most. Alternative models, which incorporate and underline the importance of slab buoyancy-driven trench migration, slab width and overriding plate motion, are better candidates to explain the complexity of subduction zones, including the variety in trench-migration velocities, overriding plate deformation and slab dip angles.  相似文献   

An epigenetic origin for the Passagem de Mariana gold deposit, Quadrilátero Ferrífero, Minas Gerais, Brazil     

D.S. Vial  B.P. Duarte  K. Fuzikawa  M.B.H. Vieira 《Ore Geology Reviews》2007,32(3-4):596

The gold–tourmaline quartz–vein deposit of Passagem de Mariana, in the southeastern part of the Quadrilátero Ferrífero, produced more than 60 tonne of gold, from the end of the 17th Century until 1954. The mine has not operated since 1985. Orebodies are veins composed of white quartz (> 60 vol.%), carbonate (ankerite), tourmaline, sericite and sulfides. Tourmaline (dravite), up to 10 vol.% of the vein, occurs as subhedral, coarse, commonly zoned crystals, and is concentrated along vein boundaries and on the edges of host rock inclusions in the veins. Tourmaline is present in all rock types in the mine, but the chemical composition of the host rocks determinates the intensity of tourmalinization, with the alteration being greater in sericitic phyllites, graphite–sericite phyllites, and calcareous rocks. The most abundant sulfide is arsenopyrite, which is normally associated with pyrite and pyrrhotite. Minor amounts of chalcopyrite, galena, löllingite, berthierite, and maldonite are present throughout the deposit. Sulfides are concentrated at veins boundary or are dispersed in the veins. Arsenopyrite is associated, most commonly, with calcareous rocks, and graphite–sericite phyllite. Pyrrhotite is usually found at the base of itabirites. Gold abundance is directly proportional to sulfide concentration. Hydrothermal alteration associated with the veins includes silicification, tourmalinization, and sulfidation. The mineralized zone is a shear zone associated with a bedding-parallel thrust fault that juxtaposes the itabirite (Lower Proterozoic Minas Supergroup) over other units. This shear zone/thrust fault extends for tens of km beyond the Passagem mine and hosts numerous gold deposits. The richest orebodies are along the itabirite footwall contact and within the graphite–sericite phyllite (Main orebody). Although many lithologic units were mineralized the graphite–sericite phyllite appears to have been most favorable for gold deposition.The area underwent three phases of deformation, D₁, D₂ and D₃. Mineral assemblages indicate upper-greenschist to lower-amphibolite conditions of regional metamorphism. Retrograde metamorphism, characterized by chloritization of biotite and chloritization and biotitization of garnet, developed locally. The gold-bearing veins crosscut the main foliation and lithologic contacts at low angle and occur within, or are in contact with, all lithotypes. Field and laboratory data indicate that gold mineralization at Passagem de Mariana is epigenetic. Gold deposition occurred after the peak of metamorphism, within the late- to post-D₂ period of deformation, which is correlated with second set of structures of Trasamazonian age of Alkmim and Marshak [Alkmim, F.F., Marshak, S., 1998. Transamazonian Orogeny in the Southern São Francisco Craton Region, Minas Gerais, Brazil: evidence for Paleoproterozoic collision and collapse in the Quadrilátero Ferrífero. Precambrian Research 90, 29-58.], indicating that the gold mineralization occurred between 2.124 and 2.04 Ga. We choose to regard Passagem de Marina as an orogenic gold deposit as defined by Groves et al. [Groves, D. I., Goldfarb, R.J., Gebre-Mariam, M., Hagemann, S.G., Robert, F., 1998. Orogenic gold deposits: A proposed classification in the context of their crustal distribution and relationship to other gold deposit types. Ore Geology Reviews 13, 7-27.], i.e., an epigenetic, structurally-hosted lode–gold vein system in a deformed metamorphic terrane.  相似文献   

Physical conditions producing slab stagnation: Constraints of the Clapeyron slope, mantle viscosity, trench retreat, and dip angles   总被引：1，自引：0，他引：1  

Yoku Torii  Shoichi Yoshioka 《Tectonophysics》2007,445(3-4):200-209

Recent seismic tomography has revealed various morphologies in the subducted lithosphere. In particular, significant flattening and stagnation of slabs around the 660-km boundary are seen in some areas beneath the northwestern Pacific subduction zones. We examined the cause of slab stagnation in terms of the Clapeyron slope of the phase transformation from ringwoodite to perovskite + magnesiowüstite, trench retreat velocity, dip angles, and high viscosity of the lower mantle based on two-dimensional (2-D) numerical simulations of thermal convection. In particular, we examined the conditions necessary for slab stagnation assuming a very small absolute value of the Clapeyron slope, which were proposed based on recent high-pressure, high-temperature (high P–T) experiments. Our calculations show that slabs tend to stagnate above the 660-km boundary with an increasing absolute value of the Clapeyron slope, viscosity jump at the boundary, and trench retreat velocity and a decreasing initial dip angle. Stagnant slabs could be obtained numerically for a realistic range of parameters obtained from high P–T experiments and other geophysical observations combining buoyancy, high lower-mantle viscosity, and trench retreat. We found that a low dip angle of a descending slab at the bottom of the upper mantle plays an important role in slab stagnation. Two main regimes underlie slab stagnation: buoyancy-dominated and viscosity-dominated regimes. In the viscosity-dominated regime, it is possible for slabs to stagnate above the 660-km boundary, even when the value of the Clapeyron slope is 0 MPa/K.  相似文献   

马里亚纳海槽玄武岩中熔融包裹体的初步研究   总被引：1，自引：0，他引：1  

孙海青  高爱国  倪培  张德玉 《海洋科学进展》2004,22(3):292-298

对马里亚纳海槽玄武岩科长石和橄榄石斑晶中的熔融包裹体进行了镜下观察和均一化测温实验。镜下观察表明,斑晶中结晶质熔融包裹体和玻璃质熔融包裹体均较发育,具有不同的相态特征和演化程度,反映了岩浆被捕获处不同的地质条件。捕获在橄揽石和斜长石斑晶中的包裹体均一化测温结果分别为1035～1100℃和105C～1145℃,比利用玄武岩全岩化学成分计算的矿物结晶温度结果低100℃左右,反映了斑晶矿物结晶的多期性。根据本次实验结果,结合马里亚纳海槽的构造背景和地质资料,对研究区玄武岩浆的运移过程进行了探讨．  相似文献   

Bait-attending fauna of the Kermadec Trench, SW Pacific Ocean: Evidence for an ecotone across the abyssal-hadal transition zone   总被引：1，自引：0，他引：1  

A.J. Jamieson  N.M. KilgallenA.A. Rowden  T. FujiiT. Horton  A.-N. LörzK. Kitazawa  I.G. Priede 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(1):49-62

The bait-attending fauna of the abyssal-hadal transition zone of the Kermadec Trench, SW Pacific Ocean (4329-7966 m), was investigated using a baited camera and a trap lander. The abyssal stations (4329-6007 m) revealed a typical scavenging fish community comprising macrourids and synaphobranchid eels, as well as natantian decapods. At the hadal depths of 7199 and 7561 m, the endemic liparid Notoliparis kermadecensis was observed aggregating at the bait reaching surprisingly high numbers of 5 and 13, respectively. A total of 3183 invertebrate samples were collected (mean deployment time=16 h) of which 97.8% were of the order Amphipoda (nine families, 16 species). Ten of the amphipod species represent new distributional records for the Kermadec Trench and the New Zealand Exclusive Economic Zone; this includes the shallowest known record of the endemic hadal amphipod Hirondellea dubia (6000, 6007 m). Using amphipods to statistically examine the compositional change across the abyssal-hadal boundary, an ecotone between depths <6007 and >6890 m was found, indicating that there is an ecologically distinct bait-attending fauna in this trench.  相似文献   

Crustal structure across the Kurile Trench off south-eastern Hokkaido by airgun-OBS profiling     

Azusa Nishizawa  Kiyoshi Suyehiro 《Geophysical Journal International》1986,86(2):371-397

  相似文献   

Measurements of upper mantle shear wave anisotropy from a permanent network in southern Mexico     

Steven A.C. van Benthem  Raúl W. Valenzuela  Gustavo J. Ponce 《Geofísica Internacional》2013,52(4):385-402

Upper mantle shear wave anisotropy under stations in southern Mexico was measured using records of SKS phases. Fast polarization directions where the Cocos plate subducts subhorizontally are oriented in the direction of the relative motion between the Cocos and North American plates, and are trench-perpendicular. This pattern is interpreted as subslab entrained flow, and is similar to that observed at the Cascadia subduction zone. Earlier studies have pointed out that both regions have in common the young age of the subducting lithosphere. Changes in the orientation of the fast axes are observed where the subducting plates change dip and/or are torn, and are thus indicative of 3-D flow around the slab edges. They are consistent with slab rollback, as previously shown by other authors. Some stations located away from the plate boundaries have their fast directions controlled by the absolute motion of the North American plate. The fast axis for station ZAIG, located in the Mesa Central, is oriented WNW-ESE and is different from all the other measurements in this study.  相似文献   

A paleo-seismological study of the Dauki fault at Jaflong,Sylhet, Bangladesh: Historical seismic events and an attempted rupture segmentation model     

《Journal of Asian Earth Sciences》2014

A paleo-seismological study was conducted at Jaflong, Sylhet, Bangladesh, which is on the eastern part of the Dauki fault. The geomorphology around Jaflong is divided into the Shillong Plateau, the foothills, the lower terraces, and the alluvial plain from north to south. Because the foothills and lower terraces are considered to be uplifted tectonically, an active fault is inferred to the south of the lower terraces. This fault, which branches from the Dauki fault as a foreland migration, is known as the Jaflong fault in this paper. The trench investigation was conducted at the southern edge of the lower terrace. The angular unconformity accompanied by folding, which is thought to be the top of the growth strata, was identified in the trench. An asymmetric anticline with a steep southern limb and gentle northern limb is inferred from the back-tilted lower terrace and the folding of the gravel layer parallel to the lower terrace surface. The timing of the seismic event which formed the folding and unconformity is dated to between AD 840 and 920.The trench investigation at Gabrakhari, on the western part of the Dauki fault, revealed that the Dauki fault ruptured in AD 1548 (Morino et al., 2011). Because the 1897 great Indian earthquake (M ⩾ 8.0; Yeats et al., 1997) was caused by the rupture of the Dauki fault (Oldham, 1899), it is clear that the Dauki fault has ruptured three times in the past one thousand years. The timing of these seismic events coincides with that of the paleo-liquefactions confirmed on the Shillong Plateau. It is essential for the paleo-seismological study of the Dauki fault to determine the surface ruptures of the 1897 earthquake. The Dauki fault might be divided into four rupture segments, the western, central, eastern, and easternmost segments. The eastern and western segments ruptured in AD 840–920 and in 1548, respectively. The 1897 earthquake might have been caused by the rupture of the central segment.  相似文献