Yoshihisa Maruyama

ACCURATE EVALUATION OF BUILDING DAMAGE IN THE 2003 BOUMERDES, ALGERIA EARTHQUAKE FROM QUICKBIRD SATELLITE IMAGES

Using QuickBird satellite images of Boumerdes city obtained following the 21 May 2003 Algeria earthquake, our study examined the applicability of high-resolution optical imagery for the visual detection of building damage grade based on the ground-truth data on the urban nature, typology of a total of 2,794 buildings, and the real damage observed. The results are presented as geographical information system (GIS) damage mapping of buildings obtained from field surveys and QuickBird images. In general, totally collapsed buildings, partially collapsed buildings, and buildings surrounded by debris can be identified by using only post-event pan-sharpened images. However, due to the nature of the damage observed, some buildings may be judged incorrectly even if preevent images are employed as a reference to evaluate the damage status. Hence, in this study, we clarify the limitations regarding the applicability of high-resolution optical satellite imagery in building damage-level mapping.

Site-Response Characteristics Evaluated from Strong Motion Records of the 2003 Boumerdes, Algeria, Earthquake

Site response characteristics at seismic stations were investigated using horizontal-to-vertical (H/V) spectral ratios calculated from a seismic-motion dataset of the 2003 Boumerdes earthquake, and transfer functions were evaluated from soil profile data. Although high peak ground acceleration (PGA) values were recorded at some sites, the nonlinear effect at these stations was not clear. The H/V spectral ratios calculated from weak and strong motion events did not show a clear difference in the predominant period and amplitudes, and the shapes of the H/V ratios were flat for some stations. These observations are characteristic of the presence of firm to hard layers under the stations; however, one station was located on Quaternary deposits showed a remarkable amplification at the predominant period and a high PGA value.

The Effects of Building Characteristics and Site Conditions on the Damage Distribution in Boumerdès after the 2003 Algeria Earthquake

This study highlights the major contributing factors to the observed damage distribution in the city of Boumerdès after the 2003 Algeria earthquake. The results of field investigations and statistical analyses show that a majority of the damaged buildings, mostly mid-rise reinforced concrete (RC) moment-frame systems, were located on steep slopes and small hilltops, along river valleys. The horizontal-to-vertical (H/V) ratios from free-field microtremor measurements at these sites did not show clear results. In contrast, buildings with the same structural characteristics located on flat ground did not suffer much damage, and clear peaks were observed from the H/V ratio curves. The amplification effects of topography have not been incorporated into the revised Algerian seismic code, but the results from this study show the importance of considering this factor when designing new buildings for earthquake resistance.

Evaluation of Building Damage and Tsunami Inundation Based on Satellite Images and GIS Data Following the 2010 Chile Earthquake

This paper presents the results of a field survey conducted by the authors after the 2010 Chile earthquake. The authors visited the affected area about a month after the earthquake. The usefulness of satellite images captured after the earthquake to detect damaged buildings in Concepción is discussed, compared with the field photos taken by the authors. GIS datasets for the damage levels of buildings in Talca and the tsunami-inundated areas in Talcahuano, Dichato, and Constitución are constructed in this study. The GIS dataset for the damage levels of buildings in Talca is compared with the satellite images, and the possibility of detecting damage to adobe houses is investigated. Further, a series of fundamental analyses are performed using a digital elevation model (DEM) that is constructed from ASTER images (ERSDAC 2009), and the usefulness of the DEM is evaluated comparing with the field survey results.

DAMAGE ASSESSMENT OF BURIED PIPES DUE TO THE 2007 NIIGATA CHUETSU-OKI EARTHQUAKE IN JAPAN

This study investigated the damage distribution of buried pipes due to the 2007 Niigata Chuetsu-Oki earthquake in Japan. Various damage datasets — e.g. water pipes, low-pressure gas pipes, mid-pressure gas pipes, sewage lines, collapsed houses, and liquefaction occurrences — were integrated into a geographic information system. Using the datasets, the spatial distribution of damage was investigated with respect to geomorphological land classification and altitude. The minimum distances between the damaged locations were measured, and the spatial correlations of damage incidents to lifeline systems were evaluated. In addition, the damage ratios of water distribution pipes were compared with different fragility curves constructed from the damage datasets for the 1995 Kobe earthquake and other recent earthquakes in Japan.

DETECTION OF COLLAPSED BUILDINGS DUE TO EARTHQUAKES USING A DIGITAL SURFACE MODEL CONSTRUCTED FROM AERIAL IMAGES

The buildings that collapsed during the 2007 Niigata Chuetsu-oki earthquake are detected based on aerial photogrammetry using digital aerial images. The digital surface models (DSMs) in the area where severe damage to buildings was observed after the earthquake are constructed using digital aerial camera images. Pre- and post-event aerial images are employed to obtain the DSMs in this study. The differences in building heights between the pre- and post-event models are considered to detect collapsed buildings and the accuracy of the method is discussed in this paper. The results indicate that the collapsed buildings can be detected and undamaged buildings can also be correctly recognized by the proposed method.

Experiments of Earthquake Early Warning to Expressway Drivers Using Synchronized Driving Simulators

To reduce the casualties and impacts resulting from earthquakes, the Japan Meteorological Agency (JMA) introduced its earthquake early warning (EEW) system to the general public on 1 October 2007. Interestingly, a side effect of the system is an anticipated increase in traffic accidents that may occur because the EEW transmission will not be received by all drivers. Consequently, the effects of an EEW are investigated using three synchronized driving simulators to replicate the conditions of three cars traveling in close proximity on an expressway. When the EEW was received by all cars, the drivers behaved properly, and no problems occurred. When an EEW was received by just one car, however, some drivers reduced speed immediately, and accidents resulted in two out of 14 test cases. These experiments show the necessity of educating the public on how to respond if an EEW is received while driving on an expressway. In such situations, activating hazard lights and reducing speed gradually is suggested to avoid traffic accidents.

EFFECTS OF EARTHQUAKE EARLY WARNING TO EXPRESSWAY DRIVERS BASED ON DRIVING SIMULATOR EXPERIMENTS

To reduce casualties and troubles due to earthquakes, Japan Meteorological Agency introduced earthquake early warning (EEW) to general public on 1 October 2007. However, the possibility that EEW induces traffic accidents exists because EEW through car radio may not be transmitted to all the expressway drivers. Hence, the effects of EEW were investigated based on driving simulator experiments. Two kinds of experiments were performed in this study. First, single driving simulator was employed to reveal the effects of EEW on expressways. The reactions of drivers with/without warning are compared in avoiding an obstacle induced by seismic motion. Second, three synchronized driving simulators, simulating three cars running together on an expressway, were employed. When EEW was transmitted to only one car, some drivers reduced speed suddenly, and accidents occurred in two cases out of 14 tests. These experiments show the necessity of public education how to react an EEW on expressways. Turning on the hazard lights after receiving an EEW and then reducing speed gradually is suggested to avoid traffic accidents.