Two 1993 Kamchatka earthquakes     

Jean M. Johnson  Yuichiro Tanioka  Kenji Satake  Larry J. Ruff 《Pure and Applied Geophysics》1995,144(3-4):633-647

Two earthquakes occurred in 1993 off southern Kamchatka. They have similar surface wave magnitudes, focal mechanisms, and depths, but have distinctly different characteristics. The November earthquake is a standard or impulsiveM7 underthrusting event. The June earthquake is a tsunamigenic or low-stress-drop event with several unusual characteristics, including a large, diffuse aftershock zone, directivity, and a long source time function. The 1993 earthquakes ruptured a segment of the Kamchatka Arc which has not ruptured since 1904. The 1993 earthquakes seem to signal the midpoint in the southern Kamchatka seismic cycle.  相似文献   

Impact of the 2011 Tohoku earthquake tsunami on zooplankton community in Otsuchi Bay,northeastern Japan     

Yuichiro Nishibe  Hiroshi Isami  Hideki Fukuda  Shuhei Nishida  Toshi Nagata  Aiko Tachibana  Atsushi Tsuda 《Journal of Oceanography》2016,72(1):77-90

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Mesoscale eddy effects on temporal variability of surface chlorophyll a in the Kuroshio Extension     

Shinya Kouketsu  Hitoshi Kaneko  Takeshi Okunishi  Kosei Sasaoka  Sachihiko Itoh  Ryuichiro Inoue  Hiromichi Ueno 《Journal of Oceanography》2016,72(3):439-451

We investigated the relationship between chlorophyll a (Chl-a) concentrations estimated from satellite observations and the activity of eddies in the Kuroshio Extension region. High (low) area-averaged Chl-a concentrations were frequently observed in the core of cyclonic (anticyclonic) eddies. Such relationships between Chl-a concentrations and eddy cores were not frequently observed in the southern part of the recirculation gyre, and advection of background meridional gradient of Chl-a by eddy-edge currents accounted for Chl-a spatial variability. Decadal-scale changes of Chl-a concentrations around the Kuroshio Extension were strongly affected by eddy activity and transport but not by large-scale near-surface isopycnal heaving. We also found that decadal changes of nutrient concentrations near the main stream could affect Chl-a concentrations in the southern part of the recirculation gyre via southward transport of eddies and mean flow.  相似文献   

Introduction to “Global Tsunami Science: Past and Future,Volume I”     

Eric L. Geist  Hermann M. Fritz  Alexander B. Rabinovich  Yuichiro Tanioka 《Pure and Applied Geophysics》2016,173(12):3663-3669

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Changes of seawater quality in Ofunto Bay,Iwate, after the 2011 off the Pacific coast of Tohoku Earthquake     

Yuichiro Yamada  Shinnosuke Kaga  Yoshimasa Kaga  Kimiaki Naiki  Shiho Watanabe 《Journal of Oceanography》2017,73(1):11-24

Ofunato Bay was a semi-closed area because of the breakwater effect at the entrance; however, the breakwater was destroyed by a massive tsunami generated by the 2011 off the Pacific coast of Tohoku Earthquake. Consequently, the physical environment of Ofunato Bay has been changed significantly, i.e., the modification of the stratified structure of seawater inside the bay and the intermittent intrusion of seawater outside the bay. These alterations of physical environment are considered to have an influence on the chemical and biological environment in Ofunato Bay. To elucidate the influence of the tsunami on the aquatic environment, we measured dissolved nutrients, chlorophyll a and dissolved oxygen concentrations, and heterotrophic bacteria abundance inside and outside of Ofunato Bay from 2012 to 2014, and compared these data with those obtained before the earthquake. As compared with before the earthquake, significant changes after the earthquake were (1) decrease of ammonium and phosphate concentrations, (2) increase of chlorophyll a concentration, (3) increase of dissolved oxygen concentration in the bottom, and (4) decrease of heterotrophic bacteria abundance. The collapse of the breakwater and consequential enhanced water exchange were considered to have brought the decrease of nutrient concentration inside the bay. Furthermore, washout of shellfish mariculture rafts by the tsunami decreased the shellfish biodeposits along with the elution of nutrients by heterotrophic bacteria. Decrease of cultivated shellfish further caused a decline in feeding pressure on phytoplankton and, subsequently, increased the phytoplankton biomass that contributed to the decrease of nutrients inside the bay.  相似文献   

Organochlorine and butyltin residues in deep-sea organisms collected from the western North Pacific,off-Tohoku,Japan   总被引：4，自引：0，他引：4  

de Brito AP  Takahashi S  Ueno D  Iwata H  Tanabe S  Kubodera T 《Marine pollution bulletin》2002,45(1-12):348-361

Organochlorine (OCs) and butyltin (BTs) residues were determined in deep-sea organisms collected from the western North Pacific, off-Tohoku, Japan. Among OCs, concentrations of polychlorinated biphenyls (PCBs) and DDTs (DDTs and its metabolites) were the highest in deep-sea organisms (maximum concentrations of 6700 and 13,000 ng/g lipid wt, respectively). Chlordane compounds (CHLs) were the next most abundant OCs, and hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were the lowest. BTs were also detected at maximum concentrations of 570 ng/g wet wt. Concentrations of PCBs, CHLs and BTs in deep-sea organisms collected from the western North Pacific, off-Tohoku, were generally lower than those in deep-sea and shallow water organisms from Japanese coastal waters. On the other hand, considerable variations in the concentrations of OCs were found among deep-sea organisms analyzed. Several carnivorous fishes such as snubnosed eel, lanternshark and grenadiers accumulated some OCs such as PCBs, DDTs and CHLs at high concentrations of up to a few μg/g levels. In addition, the residue pattern of OCs and BTs in fishes showed a specific trend according to the sampling depth; higher concentrations of PCBs, DDTs and CHLs and lower concentrations of HCHs, HCB and BTs were found in fishes collected from greater depth (1000 m) compared to those from shallower waters. This trend is consistent with the results of our earlier study on mesopelagic myctophid fishes. Results of this study suggest vertical transport of hydrophobic OCs such as PCBs, DDTs and CHLs and its accumulation in benthic deep-sea organisms.  相似文献   

Fusulinoidean faunal succession of a Paleo–Tethyan oceanic seamount in the Changning–Menglian Belt, West Yunnan, Southwest China: An overview     

Katsumi Ueno  Yujing Wang  Xiangdong Wang 《Island Arc》2003,12(2):145-161

Abstract   Fusulinoidean faunal succession from Paleo–Tethyan seamount-type carbonates of the Yutangzhai section in the Central zone of the Changning–Menglian Belt of West Yunnan, Southwest China, is presented for the first time. The Changning–Menglian Belt is one of the orogenic belts that represent the closed main Paleo–Tethys in East Asia. The Yutangzhai section is represented by basalts and overlying carbonates, about 1100 m thick. It exhibits a continuous faunal succession composed of 17 fusulinoidean assemblages ranging from the Serpukhovian (late Mississippian/late Early Carboniferous) to Midian/Capitanian (late Middle Permian/late Guadalupian). No significant faunal break can be recognized in this section. The generic and some specific composition of the Yutangzhai assemblages indicates that the faunal succession is similar to those observed in Tethyan and Panthalassan areas and is of tropical Tethyan type although their generic diversity is definitely lower than those of Paleo–Tethyan shelves, such as South China, Indochina, and Central Asia. Throughout the Yutangzhai section, the carbonate rocks are essentially massive, very pure in composition, and devoid of terrigenous siliciclastic inputs. These lithologic characters are identical to those observed in accreted shallow-marine carbonate successions of seamount origin in Permian and Jurassic accretionary complexes of Japan, for example the Akiyoshi Limestone. This evidence further demonstrates the seamount origin of the basalt–limestone succession in the Central zone of the Changning–Menglian Belt from the viewpoint of lithofacies. In middle Mississippian (middle Early Carboniferous) time, oceanic submarine volcanism that was probably related to hot spot activities formed a number of seamounts and oceanic plateaus. It was active not only in the Panthalassa, but also in the Paleo–Tethys.  相似文献   

The July 1998 Papua New Guinea Earthquake: Mechanism and Quantification of Unusual Tsunami Generation     

Kenji Satake  Yuichiro Tanioka 《Pure and Applied Geophysics》2003,160(10-11):2087-2118

— The unusual tsunami generated by the July 17, 1998 Papua New Guinea earthquake was investigated on the basis of various geophysical observations, including seismological data, tsunami waveform records, and on-land and submarine surveys. The tsunami source models were constructed for seismological high-angle and low-angle faults, splay fault, and submarine slumps. Far-field and near-field tsunamis computed from these models were compared with the recorded waveforms in and around Japan and the measured heights along the coast around Sissano Lagoon, respectively. In order to reproduce the far-field tsunami waveforms, small sources such as splay fault or submarine slump alone were not enough, and a seismological fault model was required. Relocated aftershock distribution and observed coastal subsidence were preferable for the low-angle fault, but the low-angle fault alone could not reproduce the large near-field tsunamis. The low-angle fault with additional source, possibly a submarine slump, is the most likely source of the 1998 tsunami, although other possibilities cannot be excluded. Computations from different source models showed that the far-field tsunami amplitudes are proportional to the displaced water volume at the source, and the comparison with the observed tsunami amplitudes indicated that the displaced water volume at the 1998 tsunami source was ～0.6 km³. The near-filed tsunami heights, on the other hand, are determined by the potential energy of displaced water, and the comparison with the observed heights showed that the potential energy was ～2 × 10¹² J.  相似文献   

青藏高原季风期降水的日变化   总被引：7，自引：0，他引：7  

Liu Liping  Feng Jinming  Chu Rongzhong  Zhou Yunjun  K. Ueno 《大气科学进展》2002,19(2):365-378

利用1998年夏季GAME－TIBET IOT期间的探空、降水和雷达资料分析了季风期降水和CAPE、LCL热力参量的日变化及其之间的关系。降水的日变化很明显，最大的降水和CAPE的最大值出现在同一时间段。6km和8.5km高度内的大气层结在大部分时间是不稳定的。0400－0800时间内6km以下9km以上的稳定层结阻碍了对流系统的发展，降水的日变化与这些热力参数的日变化有关。同时，利用三维云模式模拟了降水的日变化和水汽及温度对降水的影响，云模式再现了降水和回波强度的最大和最小值，晚上低层的高湿度是影响降水的重要因素。  相似文献   

Missing ophiolitic rocks along the Mae Yuam Fault as the Gondwana–Tethys divide in north-west Thailand     

Ken-ichiro Hisada  Masaaki Sugiyama  Katsumi Ueno  Punya Charusiri  Shoji Arai 《Island Arc》2004,13(1):119-127

Abstract Thailand comprises two continental blocks: Sibumasu and Indochina. The clastic rocks of the Triassic Mae Sariang Group are distributed in the Mae Hong Son–Mae Sariang area, north‐west Thailand, which corresponds to the central part of Sibumasu. The clastic rocks yield abundant detrital chromian spinels, indicating a source of ultramafic/mafic rocks. The chemistry of the detrital chromian spinels suggests that they were derived from three different rock types: ocean‐floor peridotite, chromitite and intraplate basalt, and that ophiolitic rocks were exposed in the area, where there are no outcrops of them at present. Exposition of an ophiolitic complex denotes a suture zone or other tectonic boundary. The discovery of chromian spinels suggests that the Gondwana–Tethys divide is located along the Mae Yuam Fault zone. Both paleontological and tectonic aspects support this conclusion.  相似文献