Saburoh Midorikawa

Semi-empirical estimation of peak ground acceleration from large earthquakes

Abstract A simplified method is proposed for synthesizing ground acceleration from a large earthquake. The present method is based on the semi-empirical method of Irikura (1986), which is consistent with the ω-square source model, but is much simplified for engineering use. In this method the fault of the large earthquake is divided into small elements and the acceleration envelope waveforms, instead of the time histories, from the elements are simply determined using the empirical relations. The envelope waveforms from the elements are summed to synthesize the envelope waveform of a large earthquake. The peak acceleration of the large earthquake is obtained from the maximum value of the summed envelope. To test the present method, the peak accelerations are calculated for the 1985 Central Chile earthquake (Ms 7.8), during which a considerable number of the strong-motion records were obtained close to the source. The calculated accelerations are in good agreement with the observed ones. The attenuation characteristics of the calculated peak accelerations for earthquakes of different magnitudes are examined. The results show that: 1. (1) the shortest distance from the fault plane is an appropriate definition for source distance; 2. (2) the peak acceleration becomes independent of magnitude in the near-field; and 3. (3) the source direction effect on the peak acceleration is not negligible.

Updating GIS Building Inventory Data Using High-Resolution Satellite Images for Earthquake Damage Assessment: Application to Metro Manila, Philippines

In order to conduct earthquake damage assessment, a methodology for updating GIS building inventory data in Metro Manila, Philippines, using remote sensing data is proposed. The locations of newly constructed mid- and high-rise buildings are detected from high-resolution satellite images using the image analysis technique, while the number of low-rise buildings is estimated from the built-up areas on a land cover classification map. The building inventory data is updated by incorporating the data on the newly constructed buildings into the existing data. The number of buildings in the updated inventory data shows good agreement with the results of the manual interpretation and a recent survey. A building damage assessment for a scenario earthquake is conducted using the updated inventory data.

Implications of the Mw9.0 Tohoku-Oki Earthquake for Ground Motion Scaling with Source, Path, and Site Parameters

The Mw9.0 Tohoku-oki Japan earthquake produced approximately 2,000 ground motion recordings. We consider 1,238 three-component accelerograms corrected with component-specific low-cut filters. The recordings have rupture distances between 44 km and 1,000 km, time-averaged shear wave velocities of VS30 = 90 m/s to 1,900 m/s, and usable response spectral periods of 0.01 sec to >10 sec. The data support the notion that the increase of ground motions with magnitude saturates at large magnitudes. High-frequency ground motions demonstrate faster attenuation with distance in backarc than in forearc regions, which is only captured by one of the four considered ground motion prediction equations for subduction earthquakes. Recordings within 100 km of the fault are used to estimate event terms, which are generally positive (indicating model underprediction) at short periods and zero or negative (overprediction) at long periods. We find site amplification to scale minimally with VS30 at high frequencies, in contrast with other active tectonic regions, but to scale strongly with VS30 at low frequencies.

Detection of Building Damage Areas of the 2006 Central Java, Indonesia, Earthquake through Digital Analysis of Optical Satellite Images

In order to evaluate the capability of building damage detection from optical satellite images, a procedure for digital image analysis is examined and applied to images captured before and after the 2006 Central Java, Indonesia, earthquake. In the image analysis, the pixels of the images are classified into vegetation, bare ground, and built-up areas. The damage areas are detected by the differential of the digital numbers in the built-up areas. The estimated damage distribution is validated by comparing it with the GIS data on building damage obtained from a field survey. The results show that the severely damaged areas were well detected by the analysis. In the densely vegetated areas, however, the damage was underestimated because many of the buildings were obscured by trees. For assessing quantitative damage information, the relationship between the number of collapsed buildings and the areas detected by the image analysis is evaluated.

Building Damage Assessment Using High-Resolution Satellite SAR Images of the 2010 Haiti Earthquake

Damage to individual buildings in an urban area of Port-au-Prince, Haiti, from the 2010 Haiti earthquake was assessed by means of high-resolution synthetic aperture radar (SAR) intensity images and ancillary building footprints. A comparison of pre- and post-event images and a building damage inventory showed that backscattering intensity between images was more significantly changed in collapsed buildings than in less damaged buildings. The linear discriminant function, based on the difference and correlation coefficient of the images was developed to detect collapsed buildings. The result showed that almost 75% of the buildings were correctly detected by discriminant analysis. An accuracy assessment revealed the difficulty of detecting small and congested buildings because the number of image pixels was too small and the buildings were obscured by neighboring buildings and other features in the images.

A study of site amplification effects on ground motions in Santiago, Chile

Abstract The smasch array for the observation of strong ground motion has been operating in the Santiago Valley since 1989. One of the objectives of this instrumentation project is to study the influence of local geological conditions on earthquake ground motions. The array consists of seven free-field sites located on different soil conditions ranging from a reference rock outcrop site to a site located on soft silty ground. Using data from low intensity events which occurred in 1989 and 1990, a preliminary evaluation of site amplification effects has been carried out. Fourier Amplitude spectra of the accelerograms for each site, for several different events, were computed. For this purpose only a limited portion of the record was used: that containing predominantly S waves. The spectral shapes were smoothed using a Parzens lag window of 0.7 Hz and amplitude ratios with respect to the rock site were calculated. For each site mean amplification ratios were computed. From these results it is apparent that there is a noticeable influence of the site soil conditions on the amplification value and also that this amplification can be quite different depending on the period range considered.

Dense Strong-Motion Array in Yokohama, Japan, and Its Use for Disaster Management

This paper describes the dense strong-motion array in the city of Yokohama, Japan. The strong-motion array, which consists of 150 stations in the area of about 400 km2, has been originally planned for disaster management of the city. Based on the array which can report the ground motion intensity data immediately after an event, the real-time seismic hazard and risk assessment system is developed for emergency response. The data from the array are also used for ground motion studies which contribute to seismic hazard assessment of the city. In order to improve earthquake awareness and preparedness of citizens, seismic hazard and risk maps for scenario earthquakes are prepared.

Lessons from the Behavior of a Monitored 11-Story Building during the 2011 Tohoku Earthquake for Robustness Against Design Uncertainties

Specifically detailed pin-supported walls with steel dampers have been used to seismically strengthen an 11-story steel reinforced concrete building. By looking at the observed damage and monitored motions of the building during the M9.0 Tohoku earthquake in 2011, it is demonstrated that nonstructural reinforced concrete partition walls have had a major effect on its seismic behavior during the earthquake, the neglect of which constitutes a major design uncertainty. A finite element model used to assist the retrofit design is calibrated, taking advantage of the accelerograms obtained during the earthquake. The results of nonlinear time-history analysis investigations with the modified model identify both the positive and negative effects of the nonstructural walls at various ground motion intensities, and suggest that the pin-supported wall-frame system exhibits higher robustness against both record-to-record and modeling uncertainties than its bare-frame counterpart does.

Evaluation of Liquefaction Potential for Large Areas Based on Geomorphologic Classification

Ground motion maps and observation records of liquefaction sites from ten historical earthquakes are used to develop predictive equations for the regional occurrence of liquefaction. Liquefaction occurrence ratio is determined for different geomorphological conditions and intervals of causative shaking intensity obtained from the observation data. Probability regression analysis of these data, based on a cumulative normal distribution, is then used to develop equations for estimating probability of liquefaction for different geomorphological conditions given shaking intensity. Utility of the model is demonstrated for a hypothetical Tonankai-Nankai earthquake to create an estimated liquefaction potential map having 250-m grid-cells. The approach shows promise for rapid online generation of liquefaction maps following an earthquake.

EVALUATION OF INDOOR DAMAGE IN HIGH-RISE BUILDINGS DUE TO LONG PERIOD GROUND MOTION: - Seismic behavior of refrigerator considering opening doors and drawers -@@@－扉や引出しの開閉を考慮した冷蔵庫の地震時挙動－

The aim of this study is to evaluate indoor damage in high-rise residential buildings due to long period ground motion. In this study the seismic behavior of a refrigerator was evaluated considering opening doors and drawers using shaking table tests and simulations. As the result of this study, the doors and drawers begins to open about 150 cm/s2 in case that contents exist, and the refrigerator begins to move about 250 cm/s2. And the refrigerator collides many times against walls severely with scattering contents during floor shaking. So it is highly possible that it blocks evacuation routes and injures people