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1.
--The mechanical and statistical characteristics of acoustic emission (AE) events during stable sliding are investigated through a laboratory experiment using a granite specimen with a pre-cut fault. Numerous AE events are found to be generated on the pre-cut fault, indicating that microscopically unstable fracture occurs during macroscopically stable sliding. The composite focal mechanism solution of AE events is determined from the first motion directions of P-waves. The determined mechanism is consistent with the double-couple one expected for the slip on the pre-cut fault. The source radii of large AE events are estimated to be about 10 mm from the widths of the first P-wave pulses. These indicate that the AE events are generated by shear fracture whose faulting area is a part of the pre-cut fault plane. The occurrence of AE events as a stochastic process approximately obeys the Poisson process, if the effect of mutually dependent events consti tuting clusters is corrected. The observed amplitude-frequency relation of AE events approximately follows a power law for a limited amplitude range. As the macroscopic sliding rate increases, the number of AE events per unit sliding distance decreases. This rate dependence of the AE activity is qualitatively consistent with the observation that the real area of contact between sliding surfaces decreases with an increase in the sliding rate as reported in the literature. 相似文献
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Koji Kameo Makoto Okada Moamen El-Masry Toshio Hisamitsu Saneatsu Saito Hiroomi Nakazato Naohiko Ohkouchi Minoru Ikehara Hisato Yasuda Hiroshi Kitazato Asahiko Taira 《Island Arc》2006,15(3):366-377
Abstract A continuous, well-preserved core was obtained from the Choshi area, on the Pacific side of Japan, to investigate paleoceanographic and paleoclimatic changes around the northwestern Pacific region during the middle Pleistocene. Siliciclastic sequences in the core are divided into five formations – the Obama, Yokone, Kurahashi and Toyosato Formations in the Inubo Group and the Katori Formation, in ascending order. Examination of calcareous nannofossils and magnetic polarities detected four datums in the core sediments of the Inubo Group: the top of Reticulofenestra asanoi , the base of Helicosphaera inversa , the top of Pseudoemiliania lacunosa and the Brunhes–Matuyama boundary. Fourteen marine isotope stages (MIS24–MIS11) were identified in the δ18 O and δ13 C records based on detected datums and the graphic correlation with the standard stack oxygen isotope curve. Magnetic susceptibility and gamma-ray attenuation porosity evaluator density were also measured and low values characterize the glacial intervals. Biogenic sedimentation by primary production may be larger during the glacial periods because of invasions of nutrient-rich northern surface-waters related to the southward shift of the Kuroshio front in the Choshi area. 相似文献
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Yoshito Chikaraishi Ryouichi Tanaka Ayumi Tanaka Naohiko Ohkouchi 《Organic Geochemistry》2009,40(5):569-573
Deuterium (D) depletion in phytol relative to ambient water as well as other lipids has been widely observed in various biological and geological samples; however, the mechanism for the depletion remains unknown. We have determined the hydrogen isotopic compositions of phytol and its precursors in cucumber cotyledons and have evaluated the fractionation of hydrogen isotopes during phytol biosynthesis. The hydrogen isotopic compositions of geranylgeraniol, dihydrogeranylgeraniol, tetrahydrogeranylgeraniol and phytol are ?281‰, ?302‰, ?325‰ and ?345‰, respectively. The results suggest that significantly D-depleted hydrogen is incorporated stepwise during hydrogenation of geranylgeraniol to phytol. We conclude that hydrogenation is important in controlling D depletion in phytol. 相似文献
5.
Nonuniform and Unsteady Sliding of a Plate Boundary in a Great Earthquake Cycle: A Numerical Simulation Using a Laboratory-derived Friction Law 总被引：1，自引：0，他引：1
—A numerical study is conducted to simulate complicated sliding behavior and earthquake activity on a subducting plate boundary. A 2-D model of a uniform elastic half-space with a semi-infinite thrust fault is set up, and the frictional stress prescribed by a rate- and state-dependent friction law is assumed to act on the plate boundary fault. Spatial nonuniformity of friction parameters representing rate-dependence of friction and of slip-dependence of friction are introduced in the model to obtain complicated sliding behavior in the numerical simulation. Analogs of great earthquakes that break the entire seismogenic plate boundary repeatedly occur at a constant time interval. Smaller events of seismic or aseismic sliding occur during a great earthquake cycle. Regions of rate-strengthening of friction and of a large characteristic distance in slip-dependence of friction behave as barriers or asperities. Rupture propagation is often arrested in such a region and a great earthquake occurs later when the region is broken. The variety of earthquake activity observed in many regions along real plate boundaries may be explained by similar nonuniformity in friction parameters. Conversely, the friction parameters on plate boundaries might be estimated from comparison of theoretical simulations with observations of earthquake activity. Simulation results indicate that spatiotemporal variation in stress due to aseismic sliding may play an important part in generating earthquakes. 相似文献
6.
Toward seamless indoor-outdoor applications: Developing stakeholder-oriented location-based services
Kohei Ogawa Edward Verbree Sisi Zlatanova Naohiko Kohtake Yoshiaki Ohkami 《地球空间信息科学学报》2013,16(2):109-118
Location-Based Services (LBS), an emerging new business based on smartphone and mobile networks, are becoming more and more popular. Most of these LBSs, however, only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role. Our specific aim is to solve these issues. This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders. 相似文献
7.
Toward seamless indoor-outdoor applications: Developing stakeholder-oriented location-based services
Kohei OGAWA Edward VERBREE Sisi ZLATANOVA Naohiko KOHTAKE Yoshiaki OHKAMI 《地球空间信息科学学报》2011,14(2):109-118
Location-Based Services (LBS),an emerging new business based on smartphone and mobile networks,are becoming more and more popular.Most of these LBSs,however,only offer non-seamless indoor/outdoor applications and simple applications without giving stakeholders the chance to play an active role.Our specific aim is to solve these issues.This paper presents concepts to solve these issues by expanding the Open Location Services Interface Standard (OpenLS) to allow seamless indoor/outdoor positioning and to extend the content of the services to include information recommended by stakeholders. 相似文献
8.
Kita-Uebaru natural rock slope failure and its back analysis 总被引：3，自引：2，他引：1
A large landslide occurred in Kita-Uebaru (or Asato) area of Nakagusuku village in Okinawa Island (Japan) on 10 June 2006
after a rainy period of about 9 days. The total rainfall was 126 mm from June 8 till the time of the landslide this period.
This landslide destroyed several buildings and roads, and the total travel distance of the landslide was about 110 m. In this
article, the authors were concerned with the initiation conditions of Kita-Uebaru landslide and post-failure motions of the
landslide body. The observations made in the landslide area, structural geology analyses and outcomes of geotechnical investigations
are described first. Then, possible causes of the landslide are investigated through back analyses using as inputs the geological
structure and the strength properties of planes of discontinuities involved in the sliding processes. The final part of the
article is concerned with the simulation of post-failure motions of the landslide body. The results of the investigations
and back analyses indicate that the failure plane was bi-planar and the heavy torrential rainy period for about 3 days was
the main cause of initiation of the landslide. The mechanical model presented in this article was capable of capturing the
overall features of the landslide body following the initiation of the failure. 相似文献
9.
Ömer Aydan Yoshimi Ohta Melih Geniş Naohiko Tokashiki K. Ohkubo 《Rock Mechanics and Rock Engineering》2010,43(6):857-875
Underground structures are well known to be earthquake resistant. However, the recent earthquakes showed that underground structures are also vulnerable to seismic damage. There may be several reasons such as high ground motions and permanent ground movements. This study attempts to describe various forms of damage to underground structures such as tunnels, caverns, natural caves and abandoned mines during major earthquakes. Results of various model tests on shaking table are also presented to show the effect of ground shaking on the response and collapse of underground structures in continuum and discontinuum. Furthermore, some empirical equations are proposed to assess the damage to underground structures, which may be useful for quick assessments of possible damage. 相似文献
10.
A newly developed direction finding (DF) technique for auroral hiss based on the measurement of time differences of wave arrival was carried out in 1978 at Syowa Station (geomag. lat. -70.4°), Antarctica and its two slave unmanned observing points located at about 20 km distances from Syowa. The auroral hiss signals (0.3–100 kHz) received at the two spaced points were transmitted to Syowa by a wide-band telemeter of 2 GHz. The arrival time difference of auroral hiss between Syowa and each spaced point was automatically determined by cross-correlating the waveforms of the received signals, and then the incident and azimuthal angles were measured with an accuracy of about 10°.It has been found that the new DF technique can determine localized exit regions at the ionospheric level which show rapid temporal movements. A comparison of the DF results with ground-based auroral data has shown that impulsive type auroral hiss with a wide-band frequency range has not emerged from the whole region of a bright aurora but from some localized regions of bright electron auroras at the ionospheric level, and that the arrival directions of auroral hiss change rapidly in accordance with the auroral movements. 相似文献