A new approach to time-dependent inversion of geodetic data using a Monte Carlo mixture Kalman filter   总被引：1，自引：0，他引：1  

Jun'ichi Fukuda  Tomoyuki Higuchi  Shin'ichi Miyazaki  Teruyuki Kato 《Geophysical Journal International》2004,159(1):17-39

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Geodetic inversion for space–time distribution of fault slip with time-varying smoothing regularization     

Jun'ichi Fukuda  Shin'ichi Miyazaki  Tomoyuki Higuchi  Teruyuki Kato 《Geophysical Journal International》2008,173(1):25-48

We have developed a new geodetic inversion method for space–time distribution of fault slip velocity with time-varying smoothing regularization in order to reconstruct accurate time histories of aseismic fault slip transients. We introduce a temporal smoothing regularization on slip and slip velocity through a Bayesian state space approach in which the strength of regularization (temporal smoothness of slip velocity) is controlled by a hyperparameter. The time-varying smoothing regularization is realized by treating the hyperparameter as a time-dependent stochastic variable and adopting a hierarchical Bayesian state space model, in which a prior distribution on the hyperparameter is introduced in addition to a conventional Bayesian state space model. We have tested this inversion method on two synthetic data sets generated by simulated aseismic slip transients. Results show that our method reproduces well both rapid changes of slip velocity and steady-state velocity without significant oversmoothing and undersmoothing, which has been hard to overcome by the conventional Bayesian approach with time-independent smoothing regularization. Application of this method to transient deformation in 2002 caused by a silent earthquake off the Boso peninsula, Japan, also shows similar advantages of this method over the conventional approach.  相似文献   

日本地震预警系统在2011年3月11日地震中的效能、不足与改进     

Yukio Fujinawa  Yoichi Noda 《国际地震动态》2015,(7)

自2007年10月以来,成熟的公共紧急地震速报(earthquake early warning,EEW)系统(国内称为地震预警系统)在日本得到应用。2011年日本东北近海(Tohokuoki)地震和海啸(也被称为3·11)发生时,震中附近的几百万人在最严重的振动发生前约15~20s,收到了地震预警(EEW)信息,同时更多周边地区的人在不太严重的振动开始前,有更多的预警时间。这些人中大约90%能够预先采取行动拯救自己及其家庭成员的生命,或根据事先计划采取其他措施,有些行为措施是基于对警报的直观反应。如此高的效率,取决于学校及社会中关于EEW系统知识的教育。尽管EEW系统存在着一些不足,但其有效性促使日本加密现有的地震与海啸监测台网。该台网在日本东部近海岛弧有约150个台站,并提供一个特殊的终端,使EEW系统更进一步应用在超过53 000名学生的学校中。当前对其分析和发布方案的改进也正在进行中。  相似文献   

贵州罗甸二叠纪末生物大灭绝事件后沉积的微生物岩时代和沉积学特征   总被引：9，自引：1，他引：8  

刘建波  江崎洋一  杨守仁  王海峰  足立奈津子 《古地理学报》2007,9(5):473-486

二叠纪末期发生的显生宙以来最大的生物绝灭事件,使海洋生态系统和陆地生态系统均受到重创之后,微生物岩广泛分布于全球正常浅海地区。研究认为,扬子地台在二叠纪末期存在一次海平面降低的事件,造成研究区二叠纪地层与早三叠世微生物岩之间存在沉积间断或剥蚀,并使三叠纪牙形石混入二叠纪末期的沉积物中。二叠-三叠系界线位于微生物岩层的底界;微生物岩形成于早三叠世最早期,相当于Hindeodus parvus带,是早三叠世最早期开始的海侵事件为其提供生长所需的可容纳空间。在Isarcicella staeschei带-I. isarcica带早期再次发生相对海平面降低事件,之后海平面开始快速上升。研究区早三叠世早期的微生物岩以凝块构造发育为特征,具有斑状、层状、枝状和网状凝块构造4种典型中型构造。结合前人的工作,认为微生物群落通过生物沉积和物理沉积作用形成球状体,球状体汇聚形成不同的中型凝块构造。研究扬子地台早三叠世凝块石的确切时代和结构、构造类型特征,为准确恢复生物大灭绝事件前后的环境变迁以及生物演化事件与环境变化的相互作用关系提供重要的证据。  相似文献   

Complex vertical migration of larvae of the ghost shrimp, Nihonotrypaea harmandi, in inner shelf waters of western Kyushu,Japan     

Akio Tamaki  Sumit Mandal  Yoshihiro Agata  Ikumi Aoki  Toshikazu Suzuki  Hisao Kanehara  Takashi Aoshima  Yasushi Fukuda  Hideshi Tsukamoto  Tetsuo Yanagi 《Estuarine, Coastal and Shelf Science》2010

The position of meroplanktonic larvae in the water column with depth-dependent current velocities determines horizontal transport trajectories. For those larvae occurring in inner shelf waters, little is known about how combined diel and tidally-synchronized vertical migration patterns shift ontogenetically. The vertical migration of larvae of Nihonotrypaea harmandi (Decapoda: Thalassinidea: Callianassidae) was investigated in mesotidal, inner shelf waters of western Kyushu, Japan in July–August 2006. The larval sampling at seven depth layers down to 60 m was conducted every 3 h for 36 h in a 68.5-m deep area 10 km off a major coastal adult habitat. Within a 61–65-m deep area 5–7.5 km off the adult habitat, water temperature, salinity, chlorophyll a concentration, and photon flux density were measured, and water currents there were characterized from harmonic analysis of current meter data collected in 2008. The water column was stratified, with pycnocline, chlorophyll a concentration maximum, and 2% of photon flux density at 2 m, recorded at around 22–24 m. The stratified residual currents were detected in their north component, directed offshore and onshore in the upper and lower mixed layers, respectively. More than 87% of larvae occurred between 20 m and 60 m, producing a net onshore transport of approximately 1.3 km d⁻¹. At the sunset flooding tide, all zoeal-stage larvae ascended, which could further promote retention (1.4-km potential onshore transport in 3 h). The actual onshore transport of larvae was detected by observing their occurrence pattern in a shallow embayment area with the adult habitat for 24 h in October 1994. However, ontogenetic differences in the vertical migration pattern in inner shelf waters were also apparent, with the maximum mean positions of zoeae deepening with increasing stages. Zoeae I and II performed a reverse diel migration, with their minimum and maximum depths being reached around noon and midnight, respectively. Zoeae IV and V descended continuously. Zoeae III had behaviors that were intermediate to those of the earlier- and later-stage zoeae. Postlarvae underwent a normal diel migration (nocturnal ascent) regardless of tides, with the deepest position (below 60 m and/or on the bottom) during the day. These findings give a new perspective towards how complex vertical migration patterns in meroplanktonic larvae enable their retention in inner shelf waters before the final entry of postlarvae into their natal populations.  相似文献   

New Nodosaurid Dinosaur from the Late Cretaceous of Lishui, Zhejiang Province, China   总被引：6，自引：0，他引：6  

LU Junchang JIN Xingsheng SHENG Yiming LI Yihong WANG Guoping Yoichi AZUMA 《《地质学报》英文版》2007,81(3):344-350

A new genus and species of nodosaurid dinosaur： Zhejiangosaurus lishuiensis gen. et sp. nov. is erected herein. It is characterized by the sacrum consisting of at least three true sacral vertebrae, 5 caudal dorsal vertebrae fused to form the presacral rod, wide divergence of long slender preacetabular process of the ilium from the middle line of the body, and the fourth trochanter located at the femoral mid-length.  相似文献   

A simple approach to the high-redshift sub-millimeter galaxies     

Tamon Suwa  Hiroyuki Hirashita  Yoichi Tamura 《Astrophysics and Space Science》2010,330(2):219-226

We aim at understanding the statistical properties of luminous sub-millimeter (submm) galaxies (SMGs) in the context of cosmological structure formation. By utilizing a cosmological N-body simulation to calculate the distribution of dark halos in the Universe, we consider the dust enrichment in individual halos by Type II supernovae (SNe II). The SN II rate is estimated under a star formation activity which is assumed to occur on a dynamical timescale in the dark matter potential. Our simple framework successfully explains the luminosity function, the typical star formation rate, and the typical dust mass of an observational SMG sample at z～3. We also examine the clustering properties of SMGs, since a positive cross correlation between SMGs and Lyα emitters (LAEs) is indeed observed by a recent observation. In the simulation, we select SMGs by FIR dust luminosity >10¹² L _⊙, while LAEs are chosen such that the age and the virial mass are consistent with the observed LAE properties. The SMGs and LAEs selected in this way show a spatial cross correlation whose strength is consistent with the observation. This confirms that the SMGs really trace the most clustered regions at z～3 and that their luminosities can be explained by the dust accumulation as a result of their star formation activities. We extend our prediction to higher redshifts, finding that a statistical sample of submm galaxies at z≥6 can be obtained by ALMA with a 100 arcmin² survey. With the same survey, a few submm galaxies at z～10 may be detected.  相似文献   

Charcoal records from thermokarst deposits in central Yakutia, eastern Siberia: Implications for forest fire history and thermokarst development     

Fumitaka Katamura  Masami Fukuda  Nikolai Petrovich Bosikov  Roman Vasilievich Desyatkin 《Quaternary Research》2009,71(1):36-664

Macroscopic charcoal records from a thermokarst lake deposit in central Yakutia, eastern Siberia, were used to reconstruct the history of forest fires and investigate its relationship to thermokarst initiation. High accumulation rates of charcoal and pollen were coincident in the basal deposits of the thermokarst lake, which suggests that both were initially deposited on the forest floor and subsequently reworked and accumulated in the thermokarst depression. High charcoal and pollen accumulation rates in the basal deposits, dating to 11,000-9000 cal yr BP, also indicate that the thermokarst topography developed during the early Holocene. A lower charcoal accumulation rate after ca. 9000 cal yr BP suggests that thermokarst development has been inhibited since this time. It also indicates that a surface-fire regime has been predominant at least since ca. 9000 cal yr BP in central Yakutia.  相似文献   

A New Iguanodontian Dinosaur from the Lower Cretaceous Khok Kruat Formation,Nakhon Ratchasima in Northeastern Thailand     

Masateru SHIBATA  Pratueng JINTASAKUL  Yoichi AZUMA 《《地质学报》英文版》2011,85(5):969-976

Here we report a new iguanodontian dentary found from the Lower Cretaceous Khok Kruat Formation, Nakhon Ratchasima, northeast Thailand. A unique character, which is an elongated and flat shape of the dentary ramus, makes it possible to assign the specimen to the new genus of non‐hadrosaurid iguanodontian, Ratchasimasaurus suranareae gen. et sp. nov. R. suranareae shows both primitive and derived characters, such as a caudally inclined coronoid process and alveolar trough with a primitive crown impression, and a derived buccal shelf between tooth row and coronoid process. The discovery of a new iguanodontian from the Indochina Terrene, considering that the previously reported “Probactrosaurus‐like” iguanodontian, points out a great diversity of this group in the late Early Cretaceous in Thailand, and corresponds to the Asian iguanodontian diversity at that time.  相似文献   

Compensatory response of the unicellular-calcifying alga <Emphasis Type="Italic">Emiliania huxleyi</Emphasis> (Coccolithophoridales,Haptophyta) to ocean acidification     

Shin-ya Fukuda  Iwane Suzuki  Takeo Hama  Yoshihiro Shiraiwa 《Journal of Oceanography》2011,67(1):17-25

Ocean acidification damages calcareous organisms, such as calcifying algae, foraminifera, corals, and shells. In this study, we made a device equipped with a Clark-type oxygen electrode and a pH-stat to examine how the most abundant calcifying phytoplankton, the coccolithophorid Emiliania huxleyi, responded to acidification and alkalization of the seawater medium. When E. huxleyi was incubated at pH 8.2, close to oceanic pH, the medium was alkalized during photosynthesis, and the alkalization rate [determined as μmol HCl added (mg Chl)⁻¹ h⁻¹] was identical to the activity of photosynthesis [determined as μmol O₂ evolved (mg Chl)⁻¹ h⁻¹]. When pH was maintained at 7.2 by the pH-stat, alkalization activity was stimulated and exceeded photosynthetic activity, resulting in an increase in the ratio of alkalization to photosynthesis (Alk/PS). On the other hand, no alkalization and photosynthesis were observed at pH 9.2. In contrast, acidification of seawater was observed in the dark because of the release of respiratory CO₂ from cells at pH 8.2–9.2, but not at pH 7.2. When orthophosphate was rapidly depleted within a day in the batch culture, intracellular calcification gradually increased, and both photosynthesis and alkalization decreased gradually. During the period the Alk/PS ratio also decreased gradually. These results indicate that E. huxleyi possesses an ability to compensate for the acidification of seawater when photosynthesis is more actively driven than respiration. These results suggest that the E. huxleyi cells may not be severely damaged by oceanic acidification during photosynthesis because of their homeostatic function to avoid negative effects on cellular activity. Finally, we concluded that E. huxleyi cells possess a buffering ability to reduce acidification effects when photosynthesis is actively driven.  相似文献