In this paper, we present the spatiotemporal variations in physical and chemical characteristics of surface runoff due to rainfall and snowmelt in the Mt. Norikura alpine region, northern Japanese Alps. This investigation was conducted from June 22, 2016 to October 13, 2016. In addition to a water quality investigation, rainfall investigation with a rain gauge was conducted. Despite discuss the potential of surface runoff generation. We used the method of API (antecedent precipitation index) for discuss the potential of surface runoff generation. Result from rain gauge data, we quantify tendency transition from base flow to direct flow. Consequently, we achieved quantitative assessments of surface runoff using API, and became able to grasp the presence of direct flow. During the late period of melting season, we were not able to observe the surface runoff at some of investigation points. Despite during a non-rainfall period, surface runoff is observed every time at one investigation point only (elevation 2550 m a.s.l). This observation suggest that snow patch stably supply below a ground water quality locally. From the results obtained in water quality investigation, it was found that HCO3 concentration of spring water is higher than that of melt water of snow patch. The pH, electric conductivity and HCO3 concentration surface runoff were changed during flow event following rain. After it started raining, immediately these values rose and declined within a few hours. Afterwards, these values tend to gradually rose with declining water level.
{"title":"Response of surface runoff to rainfall and snowmelt in the Mt. Norikura alpine area","authors":"Shimizu Hironori, A. Sasaki, Keisuke Suzuki","doi":"10.4145/JAHS.48.71","DOIUrl":"https://doi.org/10.4145/JAHS.48.71","url":null,"abstract":"In this paper, we present the spatiotemporal variations in physical and chemical characteristics of surface runoff due to rainfall and snowmelt in the Mt. Norikura alpine region, northern Japanese Alps. This investigation was conducted from June 22, 2016 to October 13, 2016. In addition to a water quality investigation, rainfall investigation with a rain gauge was conducted. Despite discuss the potential of surface runoff generation. We used the method of API (antecedent precipitation index) for discuss the potential of surface runoff generation. Result from rain gauge data, we quantify tendency transition from base flow to direct flow. Consequently, we achieved quantitative assessments of surface runoff using API, and became able to grasp the presence of direct flow. During the late period of melting season, we were not able to observe the surface runoff at some of investigation points. Despite during a non-rainfall period, surface runoff is observed every time at one investigation point only (elevation 2550 m a.s.l). This observation suggest that snow patch stably supply below a ground water quality locally. From the results obtained in water quality investigation, it was found that HCO3 concentration of spring water is higher than that of melt water of snow patch. The pH, electric conductivity and HCO3 concentration surface runoff were changed during flow event following rain. After it started raining, immediately these values rose and declined within a few hours. Afterwards, these values tend to gradually rose with declining water level.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74602118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, we develop two methods for the inference of rotation vector on ground surface, two rocking rotations and a single torsional rotation. The first, termed nth-order elastic method, is based on the elasticity of the ground surface. The rotation vector is constructed from the first derivative with respect to the space of the ground surface motions. The first derivative is calculated from simultaneous equations by n-th order Taylor expansion obtained by difference motion between multiple observation points. Meanwhile, the second, termed rigid method, is based on the rigidity of ground surface and the rotation.
{"title":"Development of inference methods for rotational motions on ground surface","authors":"K. Hada, Horike Masanori","doi":"10.5610/jaee.17.2_88","DOIUrl":"https://doi.org/10.5610/jaee.17.2_88","url":null,"abstract":"In this study, we develop two methods for the inference of rotation vector on ground surface, two rocking rotations and a single torsional rotation. The first, termed nth-order elastic method, is based on the elasticity of the ground surface. The rotation vector is constructed from the first derivative with respect to the space of the ground surface motions. The first derivative is calculated from simultaneous equations by n-th order Taylor expansion obtained by difference motion between multiple observation points. Meanwhile, the second, termed rigid method, is based on the rigidity of ground surface and the rotation.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82086536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-10DOI: 10.1130/abs/2017AM-307731
J. Feinberg, Mark D. Bourne, I. Lascu, B. Strauss, Zongmin Zhu, Plinio Jaqueto
Caves are deep time archives of environmental conditions at the surface. Traditional paleoclimate proxies, such as oxygen and carbon isotopic ratios, are preserved within actively growing carbonate speleothems and can be constrained in time using high-resolution 230Th geochronology. While these isotopic speleothem proxies have revolutionized paleoclimate studies, here we discuss the use of magnetic measurements to constrain changes in the flux of Fe-bearing minerals (their composition, concentration, and magnetic grain size distribution) within the context of environmental change.
{"title":"Environmental Magnetism of Cave Deposits","authors":"J. Feinberg, Mark D. Bourne, I. Lascu, B. Strauss, Zongmin Zhu, Plinio Jaqueto","doi":"10.1130/abs/2017AM-307731","DOIUrl":"https://doi.org/10.1130/abs/2017AM-307731","url":null,"abstract":"Caves are deep time archives of environmental conditions at the surface. Traditional paleoclimate proxies, such as oxygen and carbon isotopic ratios, are preserved within actively growing carbonate speleothems and can be constrained in time using high-resolution 230Th geochronology. While these isotopic speleothem proxies have revolutionized paleoclimate studies, here we discuss the use of magnetic measurements to constrain changes in the flux of Fe-bearing minerals (their composition, concentration, and magnetic grain size distribution) within the context of environmental change.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"186 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80614235","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-10DOI: 10.1002/ESSOAR.A2EDB07C05ACA4E6.16657DD60EF14162.1
B. Mamo
[B-PT03] [EE] Biomineralization and the Geochemistry of Proxies -Field ecology, Laboratory culture and Paleo: poster abstract no. BPT03-P06
[B-PT03] [EE]中国地质大学学报(自然科学版);BPT03-P06
{"title":"Benthic foraminiferal baselines for the southern Great Barrier Reef: a foundation for future ecological research","authors":"B. Mamo","doi":"10.1002/ESSOAR.A2EDB07C05ACA4E6.16657DD60EF14162.1","DOIUrl":"https://doi.org/10.1002/ESSOAR.A2EDB07C05ACA4E6.16657DD60EF14162.1","url":null,"abstract":"[B-PT03] [EE] Biomineralization and the Geochemistry of Proxies -Field ecology, Laboratory culture and Paleo: poster abstract no. BPT03-P06","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84030674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Claudia Fujita, Y. Hiratsuka, Hajime Yamamoto, Takahiro Nakajima, Z. Xue
{"title":"Numerical simulation study on mitigation of the pressure build-up in the geological formation during injection of CO 2","authors":"Claudia Fujita, Y. Hiratsuka, Hajime Yamamoto, Takahiro Nakajima, Z. Xue","doi":"10.5917/JAGH.59.229","DOIUrl":"https://doi.org/10.5917/JAGH.59.229","url":null,"abstract":"","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89302094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-10DOI: 10.1175/JCLI-D-16-0858.1
S. Shige, Yuki Nakano, M. Yamamoto
AbstractRainfall over the coastal regions of western India [Western Ghats (WG)] and Myanmar [Arakan Yoma (AY)], two regions experiencing the heaviest rainfall during the Asian summer monsoon, is examined using a Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) dataset spanning 16 years. Rainfall maxima are identified on the upslope of the WG and the coastline of AY, in contrast to the offshore locations observed in previous studies. Continuous rain with slight nocturnal and afternoon–evening maxima occurs over the upslope of the WG, while an afternoon peak over the upslope and a morning peak just off the coast are found in AY, resulting in different locations of the rainfall maxima for the WG (upslope) and AY (coastline). Large rainfall amounts with small diurnal amplitudes are observed over the WG and AY under strong environmental flow perpendicular to the coastal mountains, and vice versa. Composite analysis of the boreal summer intraseasonal oscillation (BSISO) shows that the rain an...
{"title":"Role of orography, diurnal cycle, and intraseasonal oscillation in summer monsoon rainfall over Western Ghats and Myanmar coast","authors":"S. Shige, Yuki Nakano, M. Yamamoto","doi":"10.1175/JCLI-D-16-0858.1","DOIUrl":"https://doi.org/10.1175/JCLI-D-16-0858.1","url":null,"abstract":"AbstractRainfall over the coastal regions of western India [Western Ghats (WG)] and Myanmar [Arakan Yoma (AY)], two regions experiencing the heaviest rainfall during the Asian summer monsoon, is examined using a Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) dataset spanning 16 years. Rainfall maxima are identified on the upslope of the WG and the coastline of AY, in contrast to the offshore locations observed in previous studies. Continuous rain with slight nocturnal and afternoon–evening maxima occurs over the upslope of the WG, while an afternoon peak over the upslope and a morning peak just off the coast are found in AY, resulting in different locations of the rainfall maxima for the WG (upslope) and AY (coastline). Large rainfall amounts with small diurnal amplitudes are observed over the WG and AY under strong environmental flow perpendicular to the coastal mountains, and vice versa. Composite analysis of the boreal summer intraseasonal oscillation (BSISO) shows that the rain an...","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84928893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Zhao, Chuanxu Chen, You Tian, Shiguo Wu, A. Hasegawa, J. Lei, Jung-Ho Park, I. Kang
3-D P- and S-wave velocity structures of the mantle down to a depth of 800 km beneath NE Asia are investigated using similar to 981 000 high-quality arrival-time data of local earthquakes and teleseismic events recorded at 2388 stations of permanent and portable seismic networks deployed in NE China, Japan and South Korea. Our results do not support the existence of a gap (or a hole) in the stagnant slab under the Changbai volcano, which was proposed by a previous study of teleseismic tomography. In this work we conducted joint inversions of both local-earthquake arrival times and teleseismic relative traveltime residuals, leading to a robust tomography of the upper mantle and the mantle transition zone (MTZ) beneath NE Asia. Our joint inversion results reveal clearly the subducting Pacific slab beneath the Japan Islands and the Japan Sea, as well as the stagnant slab in the MTZ beneath the Korean Peninsula and NE China. A big mantle wedge (BMW) has formed in the upper mantle and the upper part of the MTZ above the stagnant slab. Localized low-velocity anomalies are revealed clearly in the crust and the BMW directly beneath the active Changbai and Ulleung volcanoes, indicating that the intraplate volcanism is caused by hot and wet upwelling in the BMW associated with corner flows in the BMW and deep slab dehydration as well.
{"title":"Mantle transition zone, stagnant slab and intraplate volcanism in Northeast Asia","authors":"D. Zhao, Chuanxu Chen, You Tian, Shiguo Wu, A. Hasegawa, J. Lei, Jung-Ho Park, I. Kang","doi":"10.1093/GJI/GGW491","DOIUrl":"https://doi.org/10.1093/GJI/GGW491","url":null,"abstract":"3-D P- and S-wave velocity structures of the mantle down to a depth of 800 km beneath NE Asia are investigated using similar to 981 000 high-quality arrival-time data of local earthquakes and teleseismic events recorded at 2388 stations of permanent and portable seismic networks deployed in NE China, Japan and South Korea. Our results do not support the existence of a gap (or a hole) in the stagnant slab under the Changbai volcano, which was proposed by a previous study of teleseismic tomography. In this work we conducted joint inversions of both local-earthquake arrival times and teleseismic relative traveltime residuals, leading to a robust tomography of the upper mantle and the mantle transition zone (MTZ) beneath NE Asia. Our joint inversion results reveal clearly the subducting Pacific slab beneath the Japan Islands and the Japan Sea, as well as the stagnant slab in the MTZ beneath the Korean Peninsula and NE China. A big mantle wedge (BMW) has formed in the upper mantle and the upper part of the MTZ above the stagnant slab. Localized low-velocity anomalies are revealed clearly in the crust and the BMW directly beneath the active Changbai and Ulleung volcanoes, indicating that the intraplate volcanism is caused by hot and wet upwelling in the BMW associated with corner flows in the BMW and deep slab dehydration as well.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"56 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73386874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-10DOI: 10.3997/2352-8265.20140218
H. Ohtani, H. Mikada, J. Takekawa
Hydraulic fracturing is a technique to enhance the permeability around the borehole to create fracture networks in oil and natural gas reservoirs. Since the performance of hydraulic fracturing is not fully predictable beforehand, it is important to pre-estimate the extension and the connectivity of artificial fractures for a given condition such as in-situ stress and various mechanical properties of reservoir rock. It, therefore, has been drawing attention to achieve this with a method of numerical simulation in recent years. The propagating direction of hydraulic fractures is the direction of maximum principal stress in an isotropic medium. Since reservoir rock of shale oil or gas is anisotropic in the mechanical properties inferred from several laboratory tests, the propagating direction of hydraulic fractures is strongly affected by the direction of anisotropy axis. Since there are few researches conducted on the numerical simulation of hydraulic fracturing in strongly anisotropic media with the existence of differential stress towards the borehole, it is necessary to examine the role of the differential stress. We give mechanically anisotropic properties such as uniaxial compressive strength, uniaxial tensile strength, permeability, etc., based on the calibration of microscopic parameters of DEM to represent macroscopic parameters of the reservoir rock. The empirical assumption of macroscopic uniaxial tensile strength distribution is introduced into microscopic strength of the model. The result showed that if the differential stress is large, hydraulic fractures tend to propagate in the direction of maximum principal stress whereas hydraulic fractures tend to propagate in the direction of bedding plane under low differential stress. Moreover, this information suggests that in the shale reservoir, which has mechanical anisotropy, the differential stress has important role in estimating the propagation direction of hydraulic fractures.
{"title":"Fundamental research on the role of differential stress in hydraulic fracturing in strength-anisotropic medium","authors":"H. Ohtani, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140218","DOIUrl":"https://doi.org/10.3997/2352-8265.20140218","url":null,"abstract":"Hydraulic fracturing is a technique to enhance the permeability around the borehole to create fracture networks in oil and natural gas reservoirs. Since the performance of hydraulic fracturing is not fully predictable beforehand, it is important to pre-estimate the extension and the connectivity of artificial fractures for a given condition such as in-situ stress and various mechanical properties of reservoir rock. It, therefore, has been drawing attention to achieve this with a method of numerical simulation in recent years. The propagating direction of hydraulic fractures is the direction of maximum principal stress in an isotropic medium. Since reservoir rock of shale oil or gas is anisotropic in the mechanical properties inferred from several laboratory tests, the propagating direction of hydraulic fractures is strongly affected by the direction of anisotropy axis. Since there are few researches conducted on the numerical simulation of hydraulic fracturing in strongly anisotropic media with the existence of differential stress towards the borehole, it is necessary to examine the role of the differential stress. We give mechanically anisotropic properties such as uniaxial compressive strength, uniaxial tensile strength, permeability, etc., based on the calibration of microscopic parameters of DEM to represent macroscopic parameters of the reservoir rock. The empirical assumption of macroscopic uniaxial tensile strength distribution is introduced into microscopic strength of the model. The result showed that if the differential stress is large, hydraulic fractures tend to propagate in the direction of maximum principal stress whereas hydraulic fractures tend to propagate in the direction of bedding plane under low differential stress. Moreover, this information suggests that in the shale reservoir, which has mechanical anisotropy, the differential stress has important role in estimating the propagation direction of hydraulic fractures.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80457548","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-10DOI: 10.1130/ABS/2017AM-299672
W. Behr, A. Kotowski, K. Ashley
We present data from an exhumed subduction interface that closely resembles the geologic environment of modern deep episodic tremor and slow slip (ETS). We focus on Eocene high pressure metamorphic rocks from the Cycladic Blueschist Unit on Syros Island in Greece. Metabasalts on Syros consist of intercalated blueschists and eclogites that record prograde deformation at 12-16 kbar (35-50 km) and 450-550 C-PT conditions that overlap with the deep ETS source in warm subduction zones such as Cascadia. Textural observations, Si-in-phengite concentrations, and quartz-inclusion-in-garnet barometry indicate that all of the mineral assemblages are in equilibrium, suggesting that variations in metamorphic facies reflect protolith bulk compositions rather than significant differences in PT conditions. Furthermore, field observations reveal that the coexistence of blueschists and eclogites sets up an important rheological contrast between the two metamorphic assemblages. The blueschists exhibit planar ductile deformation fabrics, whereas eclogites distributed within the blueschist matrix exhibit boudinage, brittle shear fracturing, and veins commonly filled with quartz and high pressure minerals. We interpret the high pressure brittle deformation and veining in eclogites to reflect fluid sealing and overpressurization: the high fluid-pressures drive brittle shear and extension in strong eclogitic layers that is dampened viscously into the weaker blueschist matrix. Our observations are inconsistent with models of deep ETS that invoke changes in rate-and-state friction parameters along a narrow planar fault zone, but are consistent with the inferred prominent role of high fluid pressures from geophysical and modeling studies. We suggest a conceptual model in which ETS is controlled by coupled brittle-viscous deformation in partially eclogitized basalts embedded within high-fluid-pressure patches along the plate interface.
我们提供了一个与现代深部幕式震颤和慢滑(ETS)的地质环境非常相似的俯冲界面的数据。本文研究了希腊锡罗斯岛基克拉迪蓝片岩单元始新世高压变质岩。Syros上的变质玄武岩由夹层蓝片岩和榴辉岩组成，记录了12-16 kbar (35-50 km)和450-550 C-PT条件下的递进变形，与Cascadia等温暖俯冲带的深部ETS源重叠。结构观测、硅辉石浓度和石榴石石英包裹体气压测量表明，所有矿物组合都处于平衡状态，表明变质相的变化反映了原岩体组成，而不是PT条件的显著差异。此外，野外观测表明，蓝片岩和榴辉岩的共存在两个变质组合之间建立了重要的流变学对比。蓝片岩表现为平面韧性变形组构，蓝片岩基质内榴辉岩表现为边界断裂、脆性剪切破碎、脉状充填石英和高压矿物。我们将榴辉岩中的高压脆性变形和脉纹解释为流体密封和超压的反映:高压驱动强榴辉岩层中的脆性剪切和伸展，这些剪切和伸展被粘滞到较弱的蓝片岩基质中。我们的观测结果与深层ETS的模型不一致，该模型利用了沿狭窄平面断裂带速率和状态摩擦参数的变化，但与地球物理和模拟研究推断的高流体压力的突出作用一致。我们提出了一个概念模型，其中ETS是由沿板块界面嵌入高流体压力斑块的部分榴辉化玄武岩的脆性-粘性耦合变形控制的。
{"title":"Metamorphically-induced rheological heterogeneity and the deep tremor source in subduction zones","authors":"W. Behr, A. Kotowski, K. Ashley","doi":"10.1130/ABS/2017AM-299672","DOIUrl":"https://doi.org/10.1130/ABS/2017AM-299672","url":null,"abstract":"We present data from an exhumed subduction interface that closely resembles the geologic environment of modern deep episodic tremor and slow slip (ETS). We focus on Eocene high pressure metamorphic rocks from the Cycladic Blueschist Unit on Syros Island in Greece. Metabasalts on Syros consist of intercalated blueschists and eclogites that record prograde deformation at 12-16 kbar (35-50 km) and 450-550 C-PT conditions that overlap with the deep ETS source in warm subduction zones such as Cascadia. Textural observations, Si-in-phengite concentrations, and quartz-inclusion-in-garnet barometry indicate that all of the mineral assemblages are in equilibrium, suggesting that variations in metamorphic facies reflect protolith bulk compositions rather than significant differences in PT conditions. Furthermore, field observations reveal that the coexistence of blueschists and eclogites sets up an important rheological contrast between the two metamorphic assemblages. The blueschists exhibit planar ductile deformation fabrics, whereas eclogites distributed within the blueschist matrix exhibit boudinage, brittle shear fracturing, and veins commonly filled with quartz and high pressure minerals. We interpret the high pressure brittle deformation and veining in eclogites to reflect fluid sealing and overpressurization: the high fluid-pressures drive brittle shear and extension in strong eclogitic layers that is dampened viscously into the weaker blueschist matrix. Our observations are inconsistent with models of deep ETS that invoke changes in rate-and-state friction parameters along a narrow planar fault zone, but are consistent with the inferred prominent role of high fluid pressures from geophysical and modeling studies. We suggest a conceptual model in which ETS is controlled by coupled brittle-viscous deformation in partially eclogitized basalts embedded within high-fluid-pressure patches along the plate interface.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90841847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Indonesian Throughflow (ITF) waters are significantly transformed within the Indonesian Archipelago and consequently influence the large-scale ocean circulation such as Agulhas and Leeuwin Currents. Existing ocean general circulation models (OGCMs) are, however, incapable of reproducing the transformation of the ITF waters, since tidal forcing is neglected in such models. In the present study, we first conduct high-resolution non-hydrostatic three-dimensional numerical experiments focusing on the transformation of the ITF waters in the Halmahera Sea which is thought to be the most important bottleneck in simulating the ITF water-mass properties. It is shown that intensive vertical mixing induced by breaking of internal tides in the shallow regions in the Halmahera Sea dilutes the ITF waters, significantly reducing model biases found in the existing OGCMs. We next evaluate quantitatively the effect of tide-induced vertical mixing on the transformation of the ITF waters. It is shown that tide-induced vertical mixing dominates the transformation of the ITF waters, although some supplementary processes such as horizontal mixing associated with the sub-mesoscale eddies resulting from tidal interaction with land configurations cannot be ignored.
{"title":"Non-hydrostatic simulations of tidally-induced mixing in the Halmahera Sea: A possible role in the transformation of the Indonesian Throughflow waters","authors":"T. Nagai, T. Hibiya","doi":"10.1002/2017JC013381","DOIUrl":"https://doi.org/10.1002/2017JC013381","url":null,"abstract":"The Indonesian Throughflow (ITF) waters are significantly transformed within the Indonesian Archipelago and consequently influence the large-scale ocean circulation such as Agulhas and Leeuwin Currents. Existing ocean general circulation models (OGCMs) are, however, incapable of reproducing the transformation of the ITF waters, since tidal forcing is neglected in such models. In the present study, we first conduct high-resolution non-hydrostatic three-dimensional numerical experiments focusing on the transformation of the ITF waters in the Halmahera Sea which is thought to be the most important bottleneck in simulating the ITF water-mass properties. It is shown that intensive vertical mixing induced by breaking of internal tides in the shallow regions in the Halmahera Sea dilutes the ITF waters, significantly reducing model biases found in the existing OGCMs. We next evaluate quantitatively the effect of tide-induced vertical mixing on the transformation of the ITF waters. It is shown that tide-induced vertical mixing dominates the transformation of the ITF waters, although some supplementary processes such as horizontal mixing associated with the sub-mesoscale eddies resulting from tidal interaction with land configurations cannot be ignored.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75172379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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