Styles of mesoscale brittle deformations associated with the Miocene folding of the Taishu Group,Tsushima, between the Japan Sea and East China Sea backarc basins     

Atsushi Yamaji  Tatsuhiko Yanagisawa  Katsushi Sato 《Island Arc》2021,30(1):e12392

The Taishu Group is a folded, Eocene–Lower Miocene, thick sedimentary package exposed widely on Tsushima Island between the Japan Sea and East China Sea. This location makes the strata important to understand tectonics and paleo-environments in the Far East, but the timing of the folding is controversial. We studied the styles of brittle deformations of the strata. It was found that flextural-slip folds were dominant. Mesoscale faults were classified into two groups: NE–SW trending reverse faults and NW–SE trending strike-slip faults. Members of both the groups showed movements largely perpendicular to the fold axes. The latter group consisted of sinistral and dextral faults. Accordingly, we interpreted that they were transfer faults activated during the folding. Consequently, mesoscale faults and flexural-slip faults evidence the map-scale plane strain of the Taishu Group in the plane perpendicular to the NE-trending fold axes. There were few transpressional deformations in the group. This is inconsistent with the transpression hypothesis for explaining the simultaneous folding and Japan Sea opening. Another hypothesis in which the folds in Tsushima are regarded as an onshore part of the Taiwan-Shinji fold belt is inconsistent with the timing of folding suggested by mining geologists to be consistent with and contemporaneous with this deformation. On the other hand, we found that dolerite dikes and sills were involved in the folding. Therefore, we conclude that the folding began during the late Early Miocene time and climaxed during the ore mineralization at around 15 Ma. We suggest that the folding in Tsushima was the easternmost manifestation of the compressional regime around the Yellow Sea and East China Sea in the Early to early Middle Miocene, and that the compression was brought about by the arrival of the Philippine Sea plate to initiate buoyant subduction under Kyushu.  相似文献   

http://dx.doi.org/10.1016/j.gsf.2016.06.010     

Ryuho Kataoka  Tatsuhiko Sato 《地学前缘(英文版)》2017,8(2):247-252

Galactic cosmic rays and solar protons ionize the present terrestrial atmosphere,and the air showers are simulated by well-tested Monte-Carlo simulations,such as PHITS code.We use the latest version of PHITS to evaluate the possible ionization of protoplanetary disks by galactic cosmic rays(GCRs),solar protons,and by supernova remnants.The attenuation length of GCR ionization is updated as 118 g cm~(-2),which is approximately 20% larger than the popular value.Hard and soft possible spectra of solar protons give comparable and 20% smaller attenuation lengths compared with those from standard GCR spectra,respectively,while the attenuation length is approximately 10% larger for supernova remnants.Further,all of the attenuation lengths become 10% larger in the compound gas of cosmic abundance,e.g.128 g cm~(-2) for GCRs,which can affect the minimum estimate of the size of dead zones in protoplanetary disks when the incident flux is unusually high.  相似文献   

应用压力感知胶片测定岩石连通空隙的分布     

罗绍河  後藤龍彦 《地质科技情报》2008,27(6)

应用砂岩微观孔隙模型驱替实验技术,首次研究了张天渠油田长2油层在注水开发过程中的水驱油微观机理、孔隙结构与水驱油效率的关系.通过不同驱替压力、注入水倍数下的水驱油效率驱替实验证明油层孔隙结构的非均质性直接影响水驱油效果.分析了不同渗透率砂岩模型的驱替压力、注入倍数与驱油效率之间的相互关系以及残余水、残余油的分布特征,认为非活塞式驱油、绕流、卡断是残余油形成的主要原因.该实验研究为科学、合理地制定油田注采方案、提高水驱油效率提供了可借鉴的理论依据.  相似文献   

Soil pore characteristics of evergreen and deciduous forests of the tropical monsoon region in Cambodia     

Jumpei Toriyama  Seiichi Ohta  Makoto Araki  Ken'ichirou Kosugi  Tatsuhiko Nobuhiro  Naoki Kabeya  Akira Shimizu  Koji Tamai  Mamoru Kanzaki  Sophal Chann 《水文研究》2011,25(5):714-726

Both evergreen and deciduous forests (Efs and Dfs) are widely distributed under similar climatic conditions in tropical monsoon regions. To clarify the hydraulic properties of the soil matrix in different forest types and their effects on soil water storage capacity, the soil pore characteristics (SPC) were investigated in Ef and Df stands in three provinces in Cambodia. Soils in the Ef group were characterized in common by large amounts of coarse pores with moderate pore size distribution and the absence of an extremely low K_s at shallow depths, compared to Df group soils. The mean available water capacity of the soil matrix (AWC_sm) for all horizons of the Ef and Df group soils was 0·107 and 0·146 m³ m^?3, respectively. The mean coarse pore volume of the soil matrix (CPV_sm) in the Ef and Df groups was 0·231 and 0·115 m³ m^?3, respectively. A water flow simulation using a lognormal distribution model for rain events in the early dry season indicated that variation in SPC resulted in a larger increase in available soil water in Ef soils than in Df soils. Further study on deeper soil layers in Ef and each soil type in Df is necessary for the deeper understanding of the environmental conditions and the hydrological modelling of each forest ecosystem. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Evolution of carbon dioxide-bearing saline fluids in the mantle wedge beneath the Northeast Japan arc     

Yoshitaka?KumagaiEmail author  Tatsuhiko?Kawamoto  Junji?Yamamoto 《Contributions to Mineralogy and Petrology》2014,168(4):1056

Lherzolite xenoliths containing fluid inclusions from the Ichinomegata volcano, located on the rear-arc side of the Northeast Japan arc, may be considered as samples of the uppermost mantle above the melting region in the mantle wedge. Thus, these fluid inclusions provide valuable information on the nature of fluids present in the sub-arc mantle. The inclusions in the Ichinomegata amphibole-bearing spinel–plagioclase lherzolite xenoliths were found to be composed mainly of CO₂–H₂O–Cl–S fluids. At equilibrium temperature of 920 °C, the fluid inclusions preserve pressures of 0.66–0.78 GPa, which correspond to depths of 23–28 km. The molar fraction of H₂O and the salinity of fluid inclusions are 0.18–0.35 and 3.71 ± 0.78 wt% NaCl equivalent, respectively. These fluid inclusions are not believed to be fluids derived directly from the subducting slab, but rather fluids exsolved from sub-arc basaltic magmas that are formed through partial melting of mantle wedge triggered by slab-derived fluids.  相似文献   

Two efficient algorithms for iterative linearized inversion of seismic waveform data   总被引：1，自引：0，他引：1  

Robert J. Geller  Tatsuhiko Hara 《Geophysical Journal International》1993,115(3):699-710

We present two equivalent algorithms for iterative linearized waveform inversion for 3-D Earth structure with respect to an arbitrary 3-D starting model; one is a matrix formulation, and the second is a wavefield formulation. Both algorithms require the computation of accurate synthetic seismograms, but neither requires that any particular method be used to compute the synthetics. The matrix formulation is equivalent to our previously published algorithm (Hara, Tsuboi & Geller 1991), but requires less than 10 per cent of the CPU time of the previous algorithm. The wavefield algorithm is equivalent to that of Tarantola (1986) and Mora (1987), but appears to be substantially more efficient.  相似文献   

Velocity shift in two-dimensional anisotropic random media using the Rytov method     

Tatsuhiko Saito 《Geophysical Journal International》2006,166(1):293-308

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Crustal analysis of the Ulleung Basin in the East Sea (Japan Sea) from enhanced gravity mapping     

Chan Hong Park  Jeong Woo Kim  Nobuhiro Isezaki  Daniel R. Roman  Ralph R. B. von Frese 《Marine Geophysical Researches》2006,27(4):253-266

To facilitate geological analyses of the Ulleung Basin in the East Sea (Japan Sea) between Korea and Japan, shipborne and satellite altimetry-derived gravity data are combined to derive a regionally coherent anomaly field. The 2-min gridded satellite altimetry-based gravity predicted by Sandwell and Smith [Sandwell DT, Smith WHF (1997) J Geophys Res 102(B5):10,039–10,054] are used for making cross-over adjustments that reduce the errors between track segments and at the cross-over points of shipborne gravity profiles. Relative to the regionally more homogeneous satellite gravity anomalies, the longer wavelength components of the shipborne anomalies are significantly improved with minimal distortion of their shorter wavelength components. The resulting free-air gravity anomaly map yields a more coherent integration of short and long wavelength anomalies compared to that obtained from either the shipborne or satellite data sets separately. The derived free-air anomalies range over about 140 mGals or more in amplitude and regionally correspond with bathymetric undulations in the Ulleung Basin. The gravity lows and highs along the basin’s margin indicate the transition from continental to oceanic crust. However, in the northeastern and central Ulleung Basin, the negative regional correlation between the central gravity high and bathymetric low suggests the presence of shallow denser mantle beneath thinned oceanic crust. A series of gravity highs mark seamounts or volcanic terranes from the Korean Plateau to Oki Island. Gravity modeling suggests underplating by mafic igneous rocks of the northwestern margin of the Ulleung Basin and the transition between continental and oceanic crust. The crust of the central Ulleung Basin is about a 14–15 km thick with a 4–5 km thick sediment cover. It may also include a relatively weakly developed buried fossil spreading ridge with approximately 2 km of relief.  相似文献   

Geomagnetic anomaly pattern of the Japan Sea     

Nobuhiro Isezaki  Seiya Uyeda 《Marine Geophysical Researches》1973,2(1):51-59

Using all available geomagnetic data, including those obtained in a detailed survey conducted by the authors in 1970, the geomagnetic anomaly pattern if the Japan Sea has been studied. It has been established that sublinear magnetic anomalies run subparallel to the general trend of the Japanese Islands. The peak to peak amplitudes of most of these anomalies are less than 300y, their wavelengths 20 to 40 km. The anomalies are much less distinct in linearity than those found in the northwestern corner of the Pacific basin off northeastern Honshu. The linear trend is better developed in the deeper basin areas and less recognizable in the Yamato- and Kitayamato-areas. The anomaly pattern appears to support the view that the Japan Sea floor evolved through a spreading process from numerous spreading centers. A definite conclusion about the genesis of the Japan Sea, however, must await further investigation.  相似文献   

Grain size,La/Yb and Th/Sc of settling particles in the western North Pacific: Evidence for lateral transport of small Asian loess     

Nobuhiro Maeda  Shinichiro Noriki  Hisashi Narita 《Journal of Oceanography》2007,63(5):803-812

To understand the transport process of lithogenic particles in the ocean, we measured the grain size distributions of lithogenic particles and measured the opal, La, Yb, Th, and Sc concentrations of the settling particles collected from time-series sediment traps at Sta. KNOT (44°N, 155°E, water depth 5320 m) from June 2002 to May 2004. The annual mean lithogenic particle flux observed at the lower sediment trap (5100 m) was twice as high as that at the upper sediment trap (770 m). The contribution of Asian loess estimated by the La/Yb and the Th/Sc ratios in the lower layer was greater than that in the upper layer. The fluxes of small lithogenic particles with sizes of 3–4 μm at the lower layer (5 to 65 mg/m²/day) were approximately four times larger than that at the upper layer (0.6 to 27 mg/m²/day). These results indicate that the horizontal addition of small particle sizes of Asian loess is a main factor in the increase of lithogenic particles at the lower layer. The temporal variations in the small lithogenic particle flux at the lower layer had a positive correlation with those at the upper layer (r = 0.71). The small lithogenic particle fluxes showed a strong positive correlation with the opal fluxes (r = 0.9). We therefore conclude that the small lithogenic particles were laterally transported and scavenged by the formation of aggregates with opal.  相似文献