Precursory and coseismic resistivity changes     

Y. Yamazaki 《Pure and Applied Geophysics》1975,113(1):219-227

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Tectonoelectricity     

Yoshio Yamazaki 《Surveys in Geophysics》1977,3(2):123-142

Anomalous earth-current changes in association with an earthquake occurrence have often been reported since the 19th century. Changes reported in classical as well as recent literature are reviewed, although it is hard to say that any physically clear relationship between earth-current changes and earthquakes has been established. Even though a strong correlation between precursory earthcurrent changes and earthquakes has often been reported in the U.S.S.R. and the People's Republic of China in recent years, it appears that a general rule governing the earthquake-related earth-current changes is still very much unknown, partly because of contamination by artificial and natural noise.In contrast to the difficulty in understanding earth-current changes, monitoring of earth-resistivity seems to provide a much clearer means for interpreting geoelectric phenomena in association with tectonic processes in the Earth. Soviet and American work showed that the resistivity decreases to a considerable extent in the focal region prior to an earthquake. Such a change seems to be closely correlated to dilatancy generation in the Earth's crust. This finding doubtless provides an important means for earthquake prediction.An ususual, highly sensitive resistivity variometer, developed by the writer, disclosed that a resistivity change takes place at a teleseismic distance when an earthquake of large and medium magnitude occurs. Many of the resistivity changes thus observed are preceded by a premonitory change, which is supposed to reflect the preliminary rupture at a focal region.  相似文献   

Seismic microzonation of the greater Bangkok area using microtremor observations     

Rabin Tuladhar  Fumio Yamazaki  Pennung Warnitchai  Jun Saita 《地震工程与结构动力学》2004,33(2):211-225

Bangkok, the capital city of Thailand, is located at a remote distance from seismic sources. However, it has a substantial risk from these distant earthquakes due to the ability of the underlying soft clay to amplify ground motions. It is therefore imperative to conduct a detailed seismic hazard assessment of the area. Seismic microzonation of big cities, like Bangkok, provides a basis for site‐specific hazard analysis, which can assist in systematic earthquake mitigation programs. In this study, a seismic microzonation map for the greater Bangkok area is constructed using microtremor observations. Microtremor observations were carried out at more than 150 sites in the greater Bangkok area. The predominant periods of the ground were determined from the horizontal‐to‐vertical (H/V) spectral ratio technique. A microzonation map was then developed for the greater Bangkok area based on the observations. Moreover, the transfer functions were calculated for the soil profile at eight sites, using the computer program SHAKE91, to validate the results from the microtremor analysis. The areas near the Gulf of Thailand, underlaid by a thick soft clay layer, were found to have long natural periods ranging from 0.8s to 1.2s. However, the areas outside the lower central plain have shorter predominant periods of less than 0.4s. The study shows that there is a great possibility of long‐period ground vibration in Bangkok, especially in the areas near the Gulf of Thailand. This may have severe effects on long‐period structures, such as high‐rise buildings and long‐span bridges. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Textural analysis and flow mechanism of the Donzurubo subaqueous pyroclastic flow deposits     

T. Yamazaki  I. Kato  I. Muroi  M. Abe 《Bulletin of Volcanology》1973,37(2):231-244

The Donzurubo subaqueous pyroclastic flow deposits deposited in subaqueous environments maintaining high temperatures (about 500°C). Each flow unit of these pyroclastic flow deposits shows some characteristic size distributions in its stratigraphic column. The concentration of pumice at the top clearly defines the top facies of a flow unit. Median diameter (Md Ø) and the averages of the largest ten essential dense debris increase gradually starting from both the top and the bottom of the flow unit. The maximum points of Md Ø and the averages of the largest ten essential dense debris are usually found in the middle zone of each flow unit, but the Md Ø maximum points are generally in a lower position than the averages. Mechanical analyses show that the deposits consist of polymodal populations. They show, on the whole, an asymmetrical distribution, which is mainly due to the absence of the coarser fractions of the main population. The size distribution characteristics and the C-M pattern of the deposits suggest that these subaqueous pyroclastic flow deposits were not originated by homogeneously suspended turbulent flows but by incandescent turbulent flows with layered suspension.  相似文献   

Population vulnerability to tsunami hazards informed by previous and projected disasters: a case study of American Samoa     

Wood  Nathan  Jones  Jeanne M.  Yamazaki  Yoshiki  Cheung  Kwok-Fai  Brown  Jacinta  Jones  Jamie L.  Abdollahian  Nina 《Natural Hazards》2019,95(3):505-528

Natural Hazards - Population vulnerability from tsunamis is a function of the number and location of individuals in hazard zones and their ability to reach safety before wave arrival. Previous...  相似文献   

Fragility curves for expressway embankments based on damage datasets after recent earthquakes in Japan     

Yoshihisa Maruyama  Fumio Yamazaki  Kiku Mizuno  Yoshiyuki Tsuchiya  Hiroyuki Yogai 《Soil Dynamics and Earthquake Engineering》2010

The seismometer network of the Japanese expressway system was enhanced following the 1995 Kobe earthquake. Based on earthquake information from the instruments of the seismometer network, a traffic control is performed directly after the event because of the potential for damage to expressway structures. Expressways serve as vital trunk lines of transportation and are important for the restoration of damage-stricken areas. Therefore, earthquake-induced damage to expressway structures should be estimated as soon as possible. Expressway embankments were seriously damaged during recent earthquakes, such as the 2004 Niigata Chuetsu earthquake. The present study constructs the fragility curves of expressway embankments in Japan in order to estimate the damage distribution immediately after an earthquake. Damage datasets for expressways are compiled for the 2003 Northern-Miyagi earthquake, the 2003 Tokachi-oki earthquake, the 2004 Niigata Chuetsu earthquake, and the 2007 Niigata Chuetsu-oki earthquake. The spatial distributions of the peak ground velocity (PGV) are estimated for these four earthquakes in order to evaluate the relationship between the damage ratio of expressway embankments and the PGV. Statistical analysis is then conducted in order to draw the fragility curves for expressway embankments. Based on the fragility curves, major damage that disrupts ordinary expressway traffic may occur when the peak ground velocity exceeds approximately 35.0 cm/s. The fragility curves constructed in the present study are helpful for predicting the damage distribution on expressways soon after an earthquake, which enables efficient traffic control and rapid disaster response.  相似文献   

Crustal structure of central Japan and its petrological implications     

Oguz Ozel  Takaya Iwasaki  Takeo Moriya  Shin'ichi Sakai  Takuya Maeda  Chengshi Piao  Toshikatsu Yoshii  Shinya Tsukada  Akihito Ito  Masayuki Suzuki  Akira Yamazaki  & Hiroki Miyamachi 《Geophysical Journal International》1999,138(1):257-274

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Effects of extratropical warming on ENSO amplitudes in an ensemble of a coupled GCM     

Kuniko Yamazaki  Masahiro Watanabe 《Climate Dynamics》2015,44(3-4):679-693

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Ground Water Contamination of Arsenic in Ganges Plain     

Hiroaki Ishiga  Kaori Dozen  Md. Badrul Islam  Md. Hamidur Rahman  Md. Abdus Sattar  Chikako Yamazaki  Ahmed Faruque 《Gondwana Research》2001,4(4):636

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An integrated model simulating the initiation and motion of earthquake and rain induced rapid landslides and its application to the 2006 Leyte landslide   总被引：10，自引：7，他引：3  

Kyoji?SassaEmail author  Osamu?Nagai  Renato?Solidum  Yoichi?Yamazaki  Hidemasa?Ohta 《Landslides》2010,7(3):219-236

A gigantic rapid landslide claiming over 1,000 fatalities was triggered by rainfalls and a small nearby earthquake in the Leyte Island, Philippines in 2006. The disaster presented the necessity of a new modeling technology for disaster risk preparedness which simulates initiation and motion. This paper presents a new computer simulation integrating the initiation process triggered by rainfalls and/or earthquakes and the development process to a rapid motion due to strength reduction and the entrainment of deposits in the runout path. This simulation model LS-RAPID was developed from the geotechnical model for the motion of landslides (Sassa 1988) and its improved simulation model (Sassa et al. 2004b) and new knowledge obtained from a new dynamic loading ring shear apparatus (Sassa et al. 2004a). The examination of performance of each process in a simple imaginary slope addressed that the simulation model well simulated the process of progressive failure, and development to a rapid landslide. The initiation process was compared to conventional limit equilibrium stability analyses by changing pore pressure ratio. The simulation model started to move in a smaller pore pressure ratio than the limit equilibrium stability analyses because of progressive failure. However, when a larger shear deformation is set as the threshold for the start of strength reduction, the onset of landslide motion by the simulation agrees with the cases where the factor of safety estimated by the limit equilibrium stability analyses equals to a unity. The field investigation and the undrained dynamic loading ring shear tests on the 2006 Leyte landslide suggested that this landslide was triggered by the combined effect of pore water pressure due to rains and a very small earthquake. The application of this simulation model could well reproduce the initiation and the rapid long runout motion of the Leyte landslide.  相似文献