In situ Measurements of Tide Gauge Response and Corrections of Tsunami Waveforms from the Niigataken Chuetsu-oki Earthquake in 2007     

Yuichi Namegaya  Yuichiro Tanioka  Kuniaki Abe  Kenji Satake  Kenji Hirata  Masami Okada  Aditya R. Gusman 《Pure and Applied Geophysics》2009,166(1-2):97-116

Linear and nonlinear responses of ten well-type tide gauge stations on the Japan Sea coast of central Japan were estimated by in situ measurements. We poured water into the well or drained water from the well by using a pump to make an artificial water level difference between the outer sea and the well, then measured the recovery of water level in the well. At three tide gauge stations, Awashima, Iwafune, and Himekawa, the sea-level change of the outer sea is transmitted to the tide well instantaneously. However, at seven tide gauge stations, Nezugaseki, Ryotsu, Ogi, Teradomari, Banjin, Kujiranami, and Naoetsu, the sea-level change of the outer sea is not always transmitted to the tide well instantaneously. At these stations, the recorded tsunami waveforms are not assured to follow the actual tsunami waveforms. Tsunami waveforms from the Niigataken Chuetsu-oki Earthquake in 2007 recorded at these stations were corrected by using the measured tide gauge responses. The corrected amplitudes of the first and second waves were larger than the uncorrected ones, and the corrected peaks are a few minutes earlier than the uncorrected ones at Banjin, Kujiranami, and Ogi. At Banjin, the correction was significant; the corrected amplitudes of the first and second upward motion are +103 cm and +114 cm, respectively, while the uncorrected amplitudes were +96 cm and +88 cm. At other tide gauge stations, the differences between the uncorrected and corrected tsunami waveforms were insignificant.  相似文献   

A petrological and geochemical study on time-series samples from Klyuchevskoy volcano,Kamchatka arc   总被引：1，自引：0，他引：1  

Olga?Bergal-Kuvikas  Mitsuhiro?NakagawaEmail author  Takeshi?Kuritani  Yaroslav?Muravyev  Nataliya?Malik  Elena?Klimenko  Mizuho?Amma-Miyasaka  Akiko?Matsumoto  Shunjiro?Shimada 《Contributions to Mineralogy and Petrology》2017,172(5):35

To understand the generation and evolution of mafic magmas from Klyuchevskoy volcano in the Kamchatka arc, which is one of the most active arc volcanoes on Earth, a petrological and geochemical study was carried out on time-series samples from the volcano. The eruptive products show significant variations in their whole-rock compositions (52.0–55.5 wt.% SiO₂), and they have been divided into high-Mg basalts and high-Al andesites. In the high-Mg basalts, lower-K and higher-K primitive samples (>9 wt.% MgO) are present, and their petrological features indicate that they may represent primary or near-primary magmas. Slab-derived fluids that induced generation of the lower-K basaltic magmas were less enriched in melt component than those associated with the higher-K basaltic magmas, and the fluids are likely to have been released from the subducting slab at shallower levels for the lower-K basaltic magmas than for higher-K basaltic magmas. Analyses using multicomponent thermodynamics indicates that the lower-K primary magma was generated by ~13% melting of a source mantle with ~0.7 wt.% H₂O at 1245–1260?°C and ~1.9 GPa. During most of the evolution of the volcano, the lower-K basaltic magmas were dominant; the higher-K primitive magma first appeared in AD 1932. In AD 1937–1938, both the lower-K and higher-K primitive magmas erupted, which implies that the two types of primary magmas were present simultaneously and independently beneath the volcano. The higher-K basaltic magmas evolved progressively into high-Al andesite magmas in a magma chamber in the middle crust from AD 1932 to ~AD 1960. Since then, relatively primitive magma has been injected continuously into the magma chamber, which has resulted in the systematic increase of the MgO contents of erupted materials with ages from ~AD 1960 to present.  相似文献   

http://dx.doi.org/10.1016/j.gsf.2016.06.013     

Tsuyoshi Komiya  Shinji Yamamoto  Shogo Aoki  Keiko Koshida  Masanori Shimojo  Yusuke Sawaki  Kazumasa Aoki  Shuhei Sakata  Takaomi D. Yokoyama  Kenshi Maki  Akira Ishikawa  Takafumi Hirata  Kenneth D. Collerson 《地学前缘(英文版)》2017,8(2):355-385

The Archean continental crusts account for ca.20% of the present volume,but the thermal history of the Earths' mantle suggests much more continental crusts were formed in the early Archean.Because the Archean continental crust underwent severe metamorphism,it is important to avoid influence by the later thermal events.We carried out a comprehensive geochronological work of Cathodoluminescence(CL) observation and U-Pb dating of zircons from orthogneisses and supracrustal rocks over the Saglek Block to obtain their protolith ages.The zircons were classified into three domains of core,mantle and rims,and the cores were further classified into three groups of inherited,altered and zoned cores based on the zonation on the CL images.We estimated the protolith ages from Pb-Pb ages of the zoned-cores of zircons with low U contents.We made a detailed sketch of a small outcrop in St.John's Harbour South(SJHS) area,and classified the orthogneisses and mafic enclaves into seven generations based on the geologic occurrence.The first and second generations comprise mafic rocks and lack magmatic zircons.We conducted CL imaging and U-Pb dating of zircons from the third,sixth and seventh generation of the orthogneisses to estimate the protolith ages at 3902 L 25,3892 ± 33 and 3897 ± 33 Ma for each,supporting the presence of the over 3.9 Ca Iqaluk Gneiss.The geological occurrence that the mafic rocks occur as enclaves within the 3.9 Ga Iqaluk Gneiss indicates that they are the oldest supracrustal rocks in the world.Our geochronological and geological studies show the Uivak Gneiss is quite varied in lithology and age from 3.6 to 3.9 Ga,and tentatively classified into six groups based on their ages.The oldest Uivak Gneiss components including the Iqaluk Gneiss are present around the SJHS area,and the orthogneisses become young as it is away.The lines of evidence of overprinting of younger granitoid on older granitoid in small outcrops and geological-map scale as well as presence of inherited zircons even in the oldest suite suggests that crustal reworking played an important role on erasing the ancient crusts.  相似文献   

High-resolution terrestrial carbon isotope and planktic foraminiferal records of the Upper Cenomanian to the Lower Campanian in the Northwest Pacific     

Reishi Takashima  Hiroshi Nishi  Toshiro Yamanaka  Keiichi Hayashi  Amane Waseda  Akiko Obuse  Takashige Tomosugi  Naoki Deguchi  Sunao Mochizuki 《Earth and Planetary Science Letters》2010,289(3-4):570-582

Making Upper Cretaceous biostratigraphic correlations between the Northwest Pacific and Tethyan–Atlantic sections have been difficult because of rare frequencies of age-diagnostic macro- and microfossils in the sequences in the Northwest Pacific region. In order to correlate these sections precisely, an integrated planktic foraminiferal and bulk wood carbon-isotope stratigraphy from the upper Cenomanian to the lower Campanian succession (the middle–upper part of the Yezo Group) of Hokkaido, northern Japan is established with an average resolution of 50 k.y. The δ¹³C curves from bulk wood of the Yezo Group and from bulk carbonate of English Chalk show remarkably similar patterns of isotopic fluctuation, allowing the correlation of 22 carbon isotopic events between these sections. This high-resolution correlation greatly improves the previous micro- and macrofossil biostratigraphic schemes in the Northwest Pacific region, and reveals that global events, such as the oxygen depletion at the OAE 2 horizon, the constant decrease in pCO₂ during the Late Cretaceous, and the eustatic sea-level falls in the late middle Turonian, Santonian/Campanian Boundary and early Campanian, are recorded in the Upper Cretaceous sequence of the Northwest Pacific.  相似文献   

Denaturing gradient gel electrophoresis shows that bacterial communities change with mid-ocean ballast water exchange     

Akiko Tomaru  Masanobu Kawachi  Yasuwo Fukuyo 《Marine pollution bulletin》2010,60(2):299-255

Ships carry ballast water for better stability and to control trim. However, the discharge of ballast water near ports is known to transport invasive species from one coastal area to another. The exchange of ballast water on the high seas is supposed to reduce such invasions of exotic species. In this study, we used denaturing gradient gel electrophoresis (DGGE) to analyze the composition of the bacterial community in ballast water before and after such a mid-ocean exchange, and we also measured total bacterial counts. Our findings confirmed that the ballast water was replaced by the mid-ocean exchange, as indicated by the marked change in the composition of the bacterial community. There was also a significant decrease in bacterial abundance after the mid-ocean exchange. Finally, our findings support the incubation hypothesis, because the composition of the bacterial communities changed over time within the same ballast water.  相似文献   

U–Pb zircon geochronology of the North Pole Dome adamellite in the eastern Pilbara Craton          下载免费PDF全文

Hisashi Asanuma  Yusuke Sawaki  Shuhei Sakata  Hideyuki Obayashi  Kazue Suzuki  Kouki Kitajima  Takafumi Hirata  Shigenori Maruyama 《Island Arc》2018,27(4)

Supracrustal rocks around the North Pole Dome area, Western Australia, provide valuable information regarding early records of the evolution of crustal processes, surface environments, and biosphere. Owing to the occurrence of the oldest known microfossils, the successions at the North Pole Dome area have attracted interest from many researchers. The Paleoarchean successions (Warrawoona Group) mainly comprise mafic‐ultramafic greenstones with intercalated cherts and felsic lavas. Age constraints on the sediments have been mainly based on zircon U–Pb geochronology. However, many zircon grains have suffered from metamictization and contain anomalously high contents of common Pb, which makes interpretation of the U–Pb data complicated. In order to provide more convincing chronological constraints, an U–Pb Concordia age is widely accepted as the best estimate. Most zircons separated from two adamellites also suffered from severe metamictization. In our analyses, less metamictized domains were selected using a pre‐ablation technique in conjunction with elemental mapping, and then their U–Pb isotopic compositions were determined with a laser ablation inductively coupled plasma mass spectrometry. Most analyzed domains contained certain amounts of common Pb (²⁰⁴Pb/²⁰⁶Pb > 0.000 1), whereas three and five U–Pb data points with less common Pb (²⁰⁴Pb/²⁰⁶Pb < 0.000 1) were obtained. These U–Pb datasets yielded U–Pb Concordia ages of ca 3 445 Ma and 3 454 Ma, respectively. These ages represent the timing of the adamellite intrusion, and constrain the minimum depositional age of the Warrawoona Group. In addition, a single xenocrystic zircon grain showed a ²⁰⁷Pb/²⁰⁶Pb age of ca 3 545 Ma, supporting the idea that the sialic basement of the Pilbara Craton existed prior to 3 500 Ma. The in situ U–Pb zircon dating combined with the pre‐ablation technique has the potentials to identify non‐metamictized parts and to yield precise and accurate geochronological data even from partially metamictized zircons.  相似文献   

Effect of canopy openness and meteorological factors on spatial variability of throughfall isotopic composition in a Japanese cypress plantation   总被引：1，自引：0，他引：1       下载免费PDF全文

Xinchao Sun  Yuichi Onda  Akiko Hirata  Hiroaki Kato  Takashi Gomi  Xueyan Liu 《水文研究》2018,32(8):1038-1049

Spatial variability of throughfall (TF) isotopic composition, used as tracer input, influences isotope hydrological applications in forested watersheds. Notwithstanding, identification of the dominant canopy factors and processes that affect the patterns of TF isotopic variability remains ambiguous. Here, we examined the spatio‐temporal variability of TF isotopic composition in a Japanese cypress plantation, in which intensive strip thinning was performed and investigated whether canopy structure at a fine resolution of canopy effect analysis is related to TF isotopic composition and how this is affected by meteorological factors. Canopy openness, as an index of canopy structure, was calculated from hemispherical photographs at different zenith angles. TF samples were collected in a 10 × 10 m experimental plot in both pre‐thinning (from July to November 2010) and post‐thinning (from May 2012 to March 2013) periods. Our results show that thinning resulted in a smaller alteration of input δ¹⁸O of gross precipitation, whereas the changes in deuterium excess varied in both directions. Despite the temporal stability of spatial patterns in TF amount, the spatial variability of TF isotopic composition was not temporally stable in both pre‐ and post‐thinning periods. Additionally, after thinning, the isotopic composition of TF was best related to canopy openness calculated at the zenith angle of 7°, exhibiting three different relationships, that is, significantly negative, significantly positive, and nonsignificant. Changes in meteorological factors (wind speed, rainfall intensity, and temperature) were found to affect the relationships between TF δ¹⁸O and canopy openness. The observed shifts in the relationships reveal different dominant factors (partial evaporation and the selection), and canopy water flowpaths control such differences. This study provides useful insights into the spatial variability of TF isotopic composition and improves our understanding of the physical processes of interception through canopy passage.  相似文献   

Longitudinal variability of the equatorial counter electrojet during the solar cycle 24     

Soares  Gabriel  Yamazaki  Yosuke  Matzka  Jürgen  Pinheiro  Katia  Stolle  Claudia  Alken  Patrick  Yoshikawa  Akimasa  Uozumi  Teiji  Fujimoto  Akiko  Kulkarni  Atul 《Studia Geophysica et Geodaetica》2019,63(2):304-319

Studia Geophysica et Geodaetica - Ground and space-based geomagnetic data were used in the investigation of the longitudinal, seasonal and lunar phase dependence of the equatorial counter...  相似文献   

Geochemical characteristics of zircons in the Ashizuri A‐type granitoids: An additional granite topology tool for detrital zircon studies          下载免费PDF全文

Yusuke Sawaki  Kazue Suzuki  Hisashi Asanuma  Satoki Okabayashi  Kentaro Hattori  Takuya Saito  Takafumi Hirata 《Island Arc》2017,26(6)

Zircon is resistant to alteration over a wide range of geological environments, and isotopic ratios within the mineral provide constraints on ages and their parental magmas. Trace element compositions in zircon are also expected to reflect those of their parent magmas, and have a potential as essential indicators for their host rocks. Because most detrital zircons that accumulate at river mouths are derived primarily from granitoids, the classification of zircon within granitoids is potentially meaningful. This study employs the conventional classification scheme of granites (I‐, S‐, M‐, and A‐types). To clarify geochemical characteristics of zircons in A‐type granites, trace element compositions of zircons extracted from the A‐type Ashizuri granitoids were examined. Zircons from the Ashizuri granitoids commonly show enrichments of heavy rare earth elements and positive Ce anomalies, indicating that these zircons were igneous in origin. In addition, zircons in these A‐type granites are characterized by enrichments of Nb, Y, Ta, Th, and U and strong negative Eu anomalies, which exhibit good positive correlations with those in their whole rocks. This fact indicates that these signatures in zircons reflect well those in their parental bodies and are useful in identifying zircons derived from A‐type granite. Based on compilations of available data, zircons from A‐type granites can be clearly discriminated from other‐types of granites within Nb/Sr–Eu anomaly, U/Sr–Eu anomaly, Nb/Sr–U/Sr, and Nb/Sr–Ta/Sr cross‐plots. All indices used in these diagrams were selected based on the geochemical features of both zircon and whole rock of A‐type granites. Application of these discrimination diagrams to detrital zircons will likely provide further insights. For example, some Hadean detrital zircons plot in similar fields to A‐type granites, implying the existence of A‐type magmatism in the Earth's earliest history.  相似文献   

Detrital zircon multi‐chronology,provenance, and low‐grade metamorphism of the Cretaceous Shimanto accretionary complex,eastern Shikoku,Southwest Japan: Tectonic evolution in response to igneous activity within a subduction zone          下载免费PDF全文

Hidetoshi Hara  Yoshihiro Nakamura  Kousuke Hara  Toshiyuki Kurihara  Hiroshi Mori  Hideki Iwano  Tohru Danhara  Shuhei Sakata  Takafumi Hirata 《Island Arc》2017,26(6)

Detrital zircon multi‐chronology combined with provenance and low‐grade metamorphism analyses enables the reinterpretation of the tectonic evolution of the Cretaceous Shimanto accretionary complex in Southwest Japan. Detrital zircon U–Pb ages and provenance analysis defines the depositional age of trench‐fill turbidites associated with igneous activity in provenance. Periods of low igneous activity are recorded by youngest single grain zircon U–Pb ages (YSG) that approximate or are older than the depositional ages obtained from radiolarian fossil‐bearing mudstone. Periods of intensive igneous activity recorded by youngest cluster U–Pb ages (YC1σ) that correspond to the younger limits of radiolarian ages. The YC1σ U–Pb ages obtained from sandstones within mélange units provide more accurate younger depositional ages than radiolarian ages derived from mudstone. Determining true depositional ages requires a combination of fossil data, detrital zircon ages, and provenance information. Fission‐track ages using zircons estimated YC1σ U–Pb ages are useful for assessing depositional and annealing ages for the low‐grade metamorphosed accretionary complex. These new dating presented here indicates the following tectonic history of the accretionary wedge. Evolution of the Shimanto accretionary complex from the Albian to the Turonian was caused by the subduction of the Izanagi plate, a process that supplied sediments via the erosion of Permian and Triassic to Early Jurassic granitic rocks and the eruption of minor amounts of Early Cretaceous intermediate volcanic rocks. The complex subsequently underwent intensive igneous activity from the Coniacian to the early Paleocene as a result of the subduction of a hot and young oceanic slab, such as the Kula–Pacific plate. Finally, the major out‐of‐sequence thrusts of the Fukase Fault and the Aki Tectonic Line formed after the middle Eocene, and this reactivation of the Shimanto accretionary complex as a result of the subduction of the Pacific plate.  相似文献