Japan Building Research Institute

Ibaraki, Japan

Japan Building Research Institute

Ibaraki, Japan
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A model for smoke filling in a large room was developed that considers entrainment into the horizontally spreading smoke under the ceiling. This was accomplished by incorporating a simple model for the spreading ceiling jet into the two-layer zone model. Here, the proposed model was validated by focusing on the horizontal smoke spread phase on the basis of the previous experimental data of smoke spread in a large office room. The calculated results were in good agreement with the experimental data. In addition, a case study on the smoke filling in a large room was conducted to clarify the characteristics of the proposed model. As a result, the proposed model can predict the underside of the smoke layer to be lower than the two-layer zone model. © 2017 Elsevier Ltd.

Hurukawa N.,Japan Building Research Institute | Maung P.M.,Ministry of Transport
Geophysical Research Letters | Year: 2011

Relocation of six M (magnitude) ≥7.0 earthquakes near the Sagaing Fault in Myanmar since 1918 allows us to image earthquake history along the Sagaing Fault. All the earthquakes were relocated on the Sagaing Fault by using the modified joint hypocenter determination method. Combining the relocated epicenters with information on foreshocks, aftershocks, seismic intensities, and coseismic displacement, we estimated the location of the fault plane that ruptured during each earthquake. This analysis revealed two seismic gaps: one between 19.2° N and 21.5°N in central Myanmar, and another south of 16.6°N in the Andaman Sea. Considering the length of the first seismic gap (∼260 km), a future earthquake of up to M ∼7.9 is expected to occur in central Myanmar. Because Nay Pyi Taw, the recently established capital of Myanmar, is located on the expected fault, its large population is exposed to a significant earthquake hazard. Copyright 2011 by the American Geophysical Union.

Murotani S.,University of Tokyo | Satake K.,University of Tokyo | Fujii Y.,Japan Building Research Institute
Geophysical Research Letters | Year: 2013

Scaling relations for seismic moment M0, rupture area S, average slip D, and asperity size Sa were obtained for large, great, and giant (Mw = 6.7-9.2) subduction-zone earthquakes. We compiled the source parameters for seven giant (Mw∼9) earthquakes globally for which the heterogeneous slip distributions were estimated from tsunami and geodetic data. We defined Sa for subfaults exhibiting slip greater than 1.5 times D. Adding 25 slip models of 10 great earthquakes around Japan, we recalculated regression relations for 32 slip models: S = 1.34 × 10 -10 M02/3, D = 1.66 × 10-7 M01/3, Sa = 2.81 × 10-11 M02/3, and Sa/S = 0.2, where S and S a are in square kilometers, M0 is in newton meters, and D is in meters. These scaling relations are very similar to those obtained by Murotani et al. (2008) for large and great earthquakes. Thus, both scaling relations can be used for future tsunami hazard assessment associated with a giant earthquake. Key Points The source scaling relations for M∼9 earthquakes are similar to those of M<8 Asperity area is 20% of source area on average regardless of earthquake size These relations can be used for tsunami modeling from giant earthquakes ©2013. American Geophysical Union. All Rights Reserved.

Satake K.,University of Tokyo | Fujii Y.,Japan Building Research Institute | Harada T.,University of Tokyo | Namegaya Y.,Geological Survey of Japan
Bulletin of the Seismological Society of America | Year: 2013

A multiple time window inversion of 53 high-sampling tsunami waveforms on ocean-bottom pressure, Global Positioning System, coastal wave, and tide gauges shows a temporal and spatial slip distribution during the 2011 Tohoku earthquake. The fault rupture started near the hypocenter and propagated into both deep and shallow parts of the plate interface. A very large slip (approximately 25 m) in the deep part off Miyagi at a location similar to the previous 869 Jogan earthquake model was responsible for the initial rise of tsunami waveforms and the recorded tsunami inundation in the Sendai and Ishinomaki plains. A huge slip, up to 69 m, occurred in the shallow part near the trench axis 3 min after the rupture initiation. This delayed shallow rupture extended for 400 km with more than a 10-m slip, at a location similar to the 1896 Sanriku tsunami earthquake, and was responsible for the peak amplitudes of the tsunami waveforms and the maximum tsunami heights measured on the northern Sanriku coast, 100 km north of the largest slip. The average slip on the entire fault was 9.5 m, and the total seismic moment was 4:2 × 1022 N ·m (Mw 9.0). The large horizontal displacement of seafloor slope was responsible for 20%-40% of tsunami amplitudes. The 2011 deep slip alone could reproduce the distribution of the 869 tsunami deposits, indicating that the 869 Jogan earthquake source could be similar to the 2011 earthquake, at least in the deep-plate interface. The large tsunami at the Fukushima nuclear power station is due to either the combination of a deep and shallow slip or a triggering of a shallow slip by a deep slip, which was not accounted for in the previous tsunami-hazard assessments.

Fujii Y.,Japan Building Research Institute | Satake K.,University of Tokyo
Pure and Applied Geophysics | Year: 2013

The slip distribution and seismic moment of the 2010 and 1960 Chilean earthquakes were estimated from tsunami and coastal geodetic data. These two earthquakes generated transoceanic tsunamis, and the waveforms were recorded around the Pacific Ocean. In addition, coseismic coastal uplift and subsidence were measured around the source areas. For the 27 February 2010 Maule earthquake, inversion of the tsunami waveforms recorded at nearby coastal tide gauge and Deep Ocean Assessment and Reporting of Tsunamis (DART) stations combined with coastal geodetic data suggest two asperities: a northern one beneath the coast of Constitucion and a southern one around the Arauco Peninsula. The total fault length is approximately 400 km with seismic moment of 1.7 × 1022 Nm (Mw 8.8). The offshore DART tsunami waveforms require fault slips beneath the coasts, but the exact locations are better estimated by coastal geodetic data. The 22 May 1960 earthquake produced very large, ~30 m, slip off Valdivia. Joint inversion of tsunami waveforms, at tide gauge stations in South America, with coastal geodetic and leveling data shows total fault length of ~800 km and seismic moment of 7.2 × 1022 Nm (Mw 9.2). The seismic moment estimated from tsunami or joint inversion is similar to previous estimates from geodetic data, but much smaller than the results from seismic data analysis. © 2012 The Author(s).

Ashie Y.,Japan National Institute for Land and Infrastructure Management | Kono T.,Japan Building Research Institute
International Journal of Climatology | Year: 2011

Recently, countermeasures against the urban heat island effect have become increasingly important in Tokyo. Such countermeasures include reduction of anthropogenic heat release and enhancement of urban ventilation. Evaluations of urban ventilation require construction of a high-resolution computational fluid dynamics (CFD) model, which takes into account complex urban morphology. The morphological complexity arises from multi-scale geometry consisting of buildings, forests, and rivers, which is superimposed on varying topography. Given this background, airflow and temperature fields over the 23 wards of Tokyo were simulated with a CFD technique using a total of approximately 5 billion computational grid cells with a horizontal grid spacing of 5 m. The root mean square (RMS) error of the air temperature between the simulation and observation results at 127 points was 1.1 °C. Using the developed model, an urban redevelopment plan for two districts in metropolitan Tokyo was examined from the viewpoint of air temperature mitigation. Numerical results showed that a reduction by 1 ha in the area covered by buildings increases the area with temperatures below 30 °C by 12 ha. Copyright © 2010 Royal Meteorological Society.

We have applied a technique to determine earthquake magnitudes, using durations of high frequency energy radiation and the maximum displacement amplitudes, to the 2011 off the Pacific coast of Tohoku Earthquake. The estimated duration of high frequency energy radiation and magnitude are 170.5 s, and 8.96, respectively. This agrees well with preliminary analyses for this earthquake. Compared with the December 26, 2004, Sumatra earthquake (M w 9.0), this event is characterized by a shorter duration of high frequency energy radiation and a larger displacement amplitude. The measured durations of high frequency energy radiation show azimuthal dependence, which indicates rupture propagation in the southwest direction. This result, together with rupture models obtained by other studies using lower frequency seismic signals or tsunami waveforms, suggests that there were two distinct rupture propagations in this event: one in a southwest direction from which high frequency energies were radiated efficiently, and the other in an east direction from which a very large seismic moment was released. We measured the time differences between F-wave arrivals and the times at which the absolute amplitudes of high bandpass (2-4 Hz) filtered F-waves became the largest. Most of the measured time differences, normalized by twice the centroid time shift, are in the range between 50 and 80 per cent. This is consistent with the frequency distribution that we obtained previously for a set of 68 large shallow earthquakes. © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

Sugimoto M.,Japan Building Research Institute
International Journal of Molecular Medicine | Year: 2014

This perspective review focused on the Werner syndrome (WS) by addressing the issue of how a single mutation in a WRN gene encoding WRN DNA helicase induces a wide range of premature aging phenotypes accompanied by an abnormal pattern of tumors. The key event caused by WRN gene mutation is the dysfunction of telomeres. Studies on normal aging have identified a molecular circuit in which the dysfunction of telomeres caused by cellular aging activates the TP53 gene. The resultant p53 suppresses cell growth and induces a shorter cellular lifespan, and also compromises mitochondrial biogenesis leading to the overproduction of reactive oxygen species (ROS) causing multiple aging phenotypes. As an analogy of the mechanism in natural aging, we described a hypothetical mechanism of premature aging in WS: telomere dysfunction induced by WRN mutation causes multiple premature aging phenotypes of WS, including shortened cellular lifespan and inflammation induced by ROS, such as diabetes mellitus. This model also explains the relatively late onset of the disorder, at approximately age 20. Telomere dysfunction in WS is closely correlated with abnormality in tumorigenesis. Thus, the majority of wide and complex pathological phenotypes of WS may be explained in a unified manner by the cascade beginning with telomere dysfunction initiated by WRN gene mutation.

I have developed two theoretical formulas on the basis of the power partition ratios among different modes of Rayleigh waves that are newly derived theoretically from seismic interferometry (SI). These formulas, one for the spatial autocorrelation method (SPAC) and another for the centerless circular array method (CCA), are used to simulate the estimates of the dispersion curves that can be obtained from the correlation methods using microtremor in situations when the higher normal modes are present along with the fundamental mode. The formulas can provide a way to overcome the problem caused by the assumption of the dominance of the fundamental mode, which is not always true. In addition, I have conducted a numerical validation check using the synthetic microtremor waveform data that were produced by the finite-difference method. I have found that the CCA can be an alternative to the SPAC to estimate the dispersion curves. The formula for the CCA can well simulate the dispersion curves estimated by the SPAC and CCA methods, and are better than the formula based on the above-mentioned assumption. Moreover, using the data mentioned above, I have discovered that the dual-mode inversion, which considers the presence of the fundamental and first higher modes on the basis of the formula for the CCA, performs better than the conventional single-mode inversion, which rests on the above-mentioned assumption. These positive results partially support the theoretical consequence of SI, i.e., the power partition ratio, and, further, SI itself on which the theoretically derived formulas fully rely. © 2010 Society of Exploration Geophysicists.

Suzuki S.,U.S. National Institute of Standards and Technology | Manzello S.L.,U.S. National Institute of Standards and Technology | Hayashi Y.,Japan Building Research Institute
Proceedings of the Combustion Institute | Year: 2013

Wildfires that spread into communities, commonly referred to as Wildland-Urban Interface fires (WUI), are a significant international problem. Post-fire damage studies have suggested for some time that firebrands are a significant cause of structure ignition in WUI fires, yet little research has been conducted to investigate firebrand production from burning vegetation and structures. To this end, firebrand production from real-scale building components under well-controlled laboratory conditions was investigated. Specifically, wall and re-entrant corner assemblies were ignited and during the combustion process, firebrands were collected to determine the size/mass distribution generated from such real-scale building components under varying wind speed. Finally, the size and mass distributions of firebrands collected in this study were compared with the data from an actual full-scale structure burn to determine if simple component tests such as these can provide insights into firebrand generation data from full-scale structures. The results are presented and discussed. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

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