Temporal changes of subsurface velocities during strong shaking as seen from seismic interferometry

We apply a deconvolution method to a strong motion data set recorded at the surface and in boreholes in northeast Honshu, Japan. We try to characterize the nonlinear effects of the subsurface soil during strong shaking and show the change of the subsurface velocity structure during the shaking. The deconvolved waveforms reflect the subsurface velocity structure, and their horizontal and vertical components correspond to S and P wave, respectively, traveling from the borehole to the ground surface. The strong motion records with smaller values of peak acceleration do not include significant nonlinear effects, so the deconvolved waveforms of the observed accelerations can be well simulated by the program SHAKE91. For high acceleration motions during the shaking of two separate earthquakes, large reductions of near-surface velocities are seen. In results for the 2008 Iwate-Miyagi Nairiku earthquake, the large high-frequency ground motions over 4g at one near-source station caused a nonlinear response of the soil, and the reduction of the average shear wave velocity reached 24%. This corresponds to a stiffness change of over 75%. The soil properties and the stiffness coefficient which changed during the shaking did not fully recover after the shaking, leaving a static change

Monitoring seismic velocity change caused by the 2011 Tohoku-oki earthquake using ambient noise records

We estimated the changes in seismic velocity in the southern Tohoku district of Japan during the six-month period centered on the 11 March 2011 Tohoku-oki earthquake, using scattered waves retrieved by autocorrelation of ambient seismic noise. The estimated velocity decrease after the earthquake, and after two large aftershocks in the study area, was as great as 1.5% in the area nearest to the mainshock. The velocity changes displayed gradual healing. The spatial distribution of the velocity change showed a correlation with both the changes in static strain, derived from GPS records, and the peak particle velocity experienced during the three earthquakes, derived from strong-motion records. Therefore, our results show that velocity changes possibly contain information from deep in the crust bearing on coseismic stress release, in addition to shallower effects due to strong ground motion

Event Data Search and Download System for WIN Format Seismic Waveform and Pick Data Files

An event data search and download system for WIN format seismic data is developed on the world wide web (www) basis. Database of the WIN format seismic data is generated separately in advance, which includes several search keys such as event locations and their uncertainty with the names of the associated waveform and pickdata files. A program package including cgi’s and command line base programs is developed to retrieve the data interactively on the www page. This system is implemented on the data server of the Joint Seismic Observations at the Niigaka-Kobe Tectonic Zone to provide obtained seismic data to the members of the research group.＜論説

Inheritance of Glutamate Oxaloacetate Transaminase Isozymes in Kekiri (Cucumis melo kekiri group)

Glutamate oxaloacetate transaminase isozymes in kekiri (Cucumis melo kekiri group) were analyzed by polyacrylamide gel electrophoresis to demonstrate the usefulness of them as genetic markers in melon breeding. The GOT isozyme phenotypes in GOT-1 showed a simple Mendelian inheritance. The additional kekiri specific phenotype in GOT-1, which was not found in the previous study, was observed in the selfed progenies. As the phenotype did not have common band with other cultivars of Cucumis melo examined, this can be used as a genetic marker for testing the genetic purity of F, hybrids in commercial seed production. Cotyledonous leaves of the plants had identical phenotypes with those of mature leaves in GOT, indicating that this genetic marker can be employed in very early growth stage for melon breeding

自治体における地震防災に貢献する正確かつ役に立つ地震情報およびその提供手法に関する研究

自治体の地震防災行政の現場では、震度情報に基づいた対応がとられる。しかしそれ以上の詳細な地震情報が不足する場合が多い。本研究では、自治体行政の現場にいて詳細な地震情報に接し得る環境を整備する。そのシステムの試用をもとに、自治体防災担当者と地震研究者が連携協力し議論して、実際の地震防災に役立つ地震情報の構築と伝達手法を研究する。An earthquake information display system was installed in the disaster prevention crisis management division of the Tottori prefectural office. An environment was established in the disaster prevention administration, where detailed earthquake information could be understood. The purpose of this study is to investigate methods of building and transferring the information which will be useful to actual earthquake disaster reduction, through discussion between the researchers and the local government administration.自治体の地震防災行政の現場では、震度情報に基づいた対応がとられる。しかしそれ以上の詳細な地震情報が不足する場合が多い。本研究では、自治体行政の現場にいて詳細な地震情報に接し得る環境を整備する。そのシステムの試用をもとに、自治体防災担当者と地震研究者が連携協力し議論して、実際の地震防災に役立つ地震情報の構築と伝達手法を研究する。An earthquake information display system was installed in the disaster prevention crisis management division of the Tottori prefectural office. An environment was established in the disaster prevention administration, where detailed earthquake information could be understood. The purpose of this study is to investigate methods of building and transferring the information which will be useful to actual earthquake disaster reduction, through discussion between the researchers and the local government administration