Building Damage Ratios Research Articles

Empirical estimation based on remote sensing images of insured typhoon-induced economic losses from building damage

Rapid and cost-effective economic loss estimation for buildings in non-life insurance is an important issue for insurance industries in order to provide immediate financial supports to residents affected by natural disasters. This study introduces an empirical approach for economic loss estimation of typhoon-induced building damage from post-disaster remote sensing (RS) images based on insurance records obtained in Osaka and Chiba, Japan affected by the 2018 Typhoon Jebi and the 2019 Typhoon Faxai, respectively. From the insurance records and the analysis of the RS images, we found that area-based loss rates (ALRs) defined as ratio of amount of loss to amount of insured values within a mesh were proportional to building damage ratios (BDRs) identified from number of damaged buildings in the RS images and existing building inventory data, whereas it was still challenging to accurately estimate loss rate for building-by-building even from very high-resolution images. A linear regression function was developed from the relationship between the ALRs and BDRs obtained in this study. We confirmed that the regression function provided a good approximation of the insured losses from the typhoon disasters. The result indicates that typhoon-induced insured losses can be rapidly estimated from the insurance inventory and the analysis of post-disaster RS images without field investigations.

Residential building flood damage: Insights on processes and implications for risk assessments

AbstractFlood damage assessments provide critical insights on processes controlling building damage and loss. Here, we present a novel damage assessment approach to develop an empirical residential building damage database from five flood events in New Zealand. Object‐level damage data was collected for flood hazard and building characteristics, along with relative building component and sub‐components damage ratios. A Random Forest Model and Spearman's Rank correlation test were applied to analyse damage data variable importance and monotonic relationships. Model and test results reveal flood inundation depth above first finished floor level is highly important and strongly correlated with total building damage ratios while flow velocity is important for structure component damage. Internal finishes components contribute highly to total building damage ratios as higher value sub‐component materials are susceptible to direct damage from water contact and indirect damage during repair. The empirical damage data has several implications for damage model development due to the limited heterogeneity of flood hazard intensities and building attributes observed. Extending empirical damage data with synthetic damage data in future would support development of more representative object‐specific damage models to evaluate direct tangible damages for local contexts.

Shallow crustal earthquake models, damage, and loss predictions in Banda Aceh, Indonesia

The city of Banda Aceh stands on Holocene fluvial basin sediment, surrounded by the Aceh and Seulimeum fault segments where large magnitude earthquakes can occur at any time. Such earthquakes could cause extensive physical infrastructure damages, injuries, and economic loss. This research aims to produce several earthquake scenarios, to determine the damage ratio of the buildings and its distribution in these different scenarios and to estimate the number of potential casualties and economic loss. Data analysis in this research includes modelling an earthquake by applying a ground motion model for shallow crustal earthquakes to yield an intensity map after the correction for site effects. The damage ratios for different types of buildings were calculated using the fragility curves of buildings that were developed by other researchers. Building occupants at different times, building damage ratios, and injury ratios were used to determine the number of injured residents in the earthquake scenario. The results show that Banda Aceh could be potentially experience earthquake ground motion within the intensity range from MMI VII to IX due to earthquakes of Mw 6.5 to Mw 7.0. The Mw 7.0 earthquake on the Aceh segment is the worst case scenario, causing building damage throughout Banda Aceh with casualty rates of 3.5–20% of the population in buildings in general if it happened during daytime, with economic loss about 3320 million USD. Mitigation and preparedness programs for the Banda Aceh community are therefore very important in order to reduce the potential level of damage, personal injury, and economic loss due to future earthquakes.

Vulnerability Characteristics of Tsunamis in Indonesia: Analysis of the Global Centre for Disaster Statistics Database

Regional disaster data are important for understanding the characteristics of disasters and for identifying potential mitigation measures. However, many countries have no official disaster database that includes information such as numbers of deaths or damaged buildings for each disaster event. The Global Centre for Disaster Statistics (GCDS) was established to assist countries and organizations in the collection of disaster data. At present, a significant amount of tsunami disaster data are available from Indonesia, which will be used to demonstrate its application for analyzing vulnerability characteristics of historical tsunamis. There are 53 data points covering 13 tsunami events between the year 1861 and 2014. Based on data availability, five tsunami events, namely the 1977 Sumba, the 2004 Indian Ocean, the 2006 Java, the 2010 Mentawai, and the 2011 Great East Japan, were selected. Numbers of deaths and damaged buildings were used in combination with hazard data to estimate vulnerability, defined as the ratio between maximum flow depth against death and building damage ratios. Numbers of evacuees were initially used to estimate actual numbers of exposed population but it was later discovered that this parameter overestimated the exposed population in certain cases. As a result, this study presents the vulnerability characteristics of people and buildings in Indonesia, exposed to unusual or extreme tsunamis, mostly in a condition without or with limited access to official warnings. In brief, a maximum flow depth of 5 m caused an approximate 100% death ratio in the majority of Indonesian tsunamis in this study. On the other hand, death ratio in the 2011 Japan tsunami was limited to 10% because of the early warning and high disaster awareness. Effective disaster risk reduction activities such as official warnings, evacuations, and tsunami education were observed for certain locations. Lastly, adding hazard and population data at the village level is recommended for improving the collection of future tsunami disaster data for the GCDS database.

An Analysis of Fatality Ratios and the Factors That Affected Human Fatalities in the 2011 Great East Japan Tsunami

This study presents a new analysis of spatial variation in fatality ratios in the 2011 Great East Japan tsunami, in order to overcome the limitations of previous studies that tended to underestimate the fatality ratios. In addition, this analysis was performed in a manner that allows the results to be compared to those from analyses of fatality ratios in other historical tsunamis. To do this, it uses population and fatality data at the village scale in areas of less than 3 km2 where the inundation ratio was greater than 70%, rather than the lower-resolution data used in previous studies. The median value of the tsunami inundation depth at each location was extracted at the original 5-m grid resolution. All of the data were obtained from the Reconstruction Support Survey Archive. Based on the results, a strong correlation between the fatality ratio and inundation depth was found only in some areas of the Sendai Plain, whereas no strong correlation was observed along the Sanriku ria coastline. Fatality ratios in Sanriku were likely related not only to the force of the tsunami but also to other factors, such as the ria topography and the population’s experience of past historical tsunamis. Data from other tsunamis in regions where tsunamis frequently occur also indicate that historical tsunami experience is a key factor in reducing fatality ratios. In contrast, the Sendai Plain shows smaller variation in local tsunami amplification effect compared to that of the Sanriku ria coastline, as well as fewer coastal defence structures. Therefore, the fatality ratio in that region was predominantly affected by the force of the tsunami and the residents’ individual characteristics. On the Sendai Plain, Ishinomaki City exhibited a strong correlation between the fatality ratio and inundation depth, as well as between fatality ratio and building damage because its low evacuation ratio meant that many fatalities occurred in victims’ homes. Therefore, the fatality ratio in Ishinomaki City was higher than those in other areas at the same inundation depth. Simple empirical formulas were developed for estimation of human fatalities based on inundation depths and building damage ratios.

Report on a reconnaissance survey of damage in Kathmandu caused by the 2015 Gorkha Nepal earthquake

Nepal was hit by the M7.8 Gorkha earthquake on April 25, 2015, which was the largest earthquake in Nepal’s history since 1934. The recent report presented by the Government of Nepal indicates that the recorded death toll has reached about 8800.Following the earthquake, the Japanese Geotechnical Society (JGS), Asian Technical Committee of ISSMGE on Geotechnical Natural Hazards (ATC3), Japan Society of Civil Engineers (JSCE) and Japan Association for Earthquake Engineering (JAEE) decided to jointly dispatch a survey team to Nepal to conduct a reconnaissance survey of the major damage caused by the earthquake. This report summarizes the results of the survey of the geotechnical and structural damage in the Kathmandu valley, which were observed by the survey sub-team between May 1 and 8, 2015. Geotechnical and geological characteristics of a deep soil profile up to 600m and a shallow profile up to 30m are also described with the help of the database system established by Bhandary et al. (2012). In order to study the correlation between building damage ratios and the predominant period of ground vibration, a partial exhaustive type survey was conducted along NS line where microtremor measurements had been previously conducted in 2008. The predominant period of ground vibration was short at the ridge of the valley and long at its center, ranging from 1.2 to 4.5s. A total of 532 buildings were assessed and more than 90% were classified as “No damage” or “Negligible to slight Damage” (Grade 0 and Grade 1), whereas only 5% of buildings were assessed as “Substantial to heavy damage” to “Destruction” (Grade 3 to Grade 5).Five locations were identified where the soil had liquefied. Liquefaction-induced damage to structures at these locations was not found, except at Nepal Engineering College where minor settlement of the college building was observed. During the 1934 earthquake, foundation liquefaction was observed in Tundhikhel area, but in the 2015 earthquake no evidence of liquefaction was detected in this area.The Kathmandu–Bhaktapur Road of Araniko Highway was heavily damaged in the Lokanthali area. The subsidence of soft soils and their lateral spreading in this area may have exacerbated the damage to this road.

Development of Building Inventory Data and Earthquake Damage Estimation in Lima, Peru for Future Earthquakes

Even though detailed building inventory data are necessary for estimating earthquake damage reliably, most developing countries do not have sufficient data for such estimations. This necessitates a way for finding building distribution and feature easily. In this study for estimating the number of households in all building categories of different structures or floor numbers in Lima, Peru, where a great earthquake is expected, we propose an estimation method based on existing GIS data from a census, satellite imagery, and building data from field surveys, and apply it to estimate the entire area of Lima for create building inventory data. Building fragility functions were used to calculate a severe damage ratio of buildings due to the expected earthquake. The rate was multiplied by created building inventory data to estimate the number of households in damaged buildings. Furthermore we clarified damage reduction by retrofitting for low earthquake-resistant buildings.

Development of Earthquake-Induced Building Damage Estimation Model Based on ALOS/PALSAR Observing the 2007 Peru Earthquake

With the aim of developing a model for estimating building damage from synthetic aperture radar (SAR) data in the L-band, which is appropriate for Peru, we propose a regression discriminant function based on field survey data in Pisco, which was seriously damaged in the 2007 Peru earthquake. The proposed function discriminates among damage ranks corresponding to the severe damage ratio of buildings using ALOS/PALSAR imagery of the disaster area before and after the earthquake. By calculating differences in and correlations of backscattering coefficients, which were explanatory variables of the regression discriminant function, we determined an optimum window size capable of estimating the degree of damage more accurately. A normalized likelihood function for the severe damage ratio was developed based on discriminant scores of the regression discriminant function. The distribution of the severe damage ratio was accurately estimated, furthermore, from PALSAR imagery using data integration of the likelihood function with fragility functions in terms of the seismic intensity of the earthquake.

Relationship between Building Damage Ratios and Ground Motion Characteristics during the 2011 Tohoku Earthquake

Fragility curves, the relationships between three kinds of building damage ratios, i.e., total collapse ratio (TCR), collapse ratio (CR) and damage ratio (DR), as well as ground motion characteristics, i.e., peak ground acceleration (PGA), peak ground velocity (PGV), Japan Meteorological Agency instrumental seismic intensity (IJMA) and spectral intensity (SI), were studied for the 2011 Tohoku Earthquake. It was found that the DR was related better to ground motion characteristics than the TCR and CR during this earthquake, and the correlation between the DR and any one of the PGV, IJMA or SI indices was almost the same. The DR during the 2011 Tohoku Earthquake reached almost the same level as that during the Kobe Earthquake for the same level of ground motions. There were some districts where the DRs did not always correspond to reasonable levels of ground motion characteristics. One reason for this was considered to be the representativeness of the ground motions over each district. Thus, one method of estimating ground motions at damaged sites was proposed by using the underground velocity structures identified from the H/V spectral ratios of microtremors, after we confirmed the consistency of the H/ V spectral ratios between earthquakes and microtremors. It is expected to be used for the construction of fragility curves with greater accuracy.

A STUDY ON PREDICTION OF DAMAGE RATIO OF PUBLIC MANAGEMENT APARTMENT BUILDINGS DUE TO EARTHQUAKE BASED ON SEISMIC PERFORMANCE INDEX

In this paper, an earthquake response analysis model based on seismic performance indices is proposed to evaluate actual seismic performance of public management apartment buildings appropriately. Damage ratio of buildings are calculated using this proposed model and observed seismic ground motions during the 1995 Hyogo-ken Nanbu Earthquake. As a result, the relationships between an index of seismic ground motion and calculated damage ratio of buildings show good agreement with vulnerability functions based on actual damage data of buildings in the 1995 Hyogo-ken Nanbu Earthquake. Through this study, it is pointed out that damage ratio of buildings could be overestimated, if load carrying capacity which has not been considered in the seismic design is not properly evaluated. Additionally, it is shown that the effect of slit on reinforced concrete wall has a big influence on the damage ratio of buildings.

Reevaluation Method of Fragility Curves of Wooden House Based on Collected Damage Information

The distribution of earthquake damage plays an important role in the rescue operation and the restoration work in the aftermath of a seismic event. Immediately after an earthquake, the building damage ratios are estimated using ground motion indices and fragility curves constructed from the prior earthquake damage information. However, it should be noted that the fragility curves may sometimes provide less accurate estimations for recent earthquakes. On the other hand, some researchers are focusing efforts on collecting the actual damage information efficiently soon after an earthquake has occurred. The increased attention to collecting the actual damage information is expected to improve the efficiency in the near future and become increasingly helpful for a rapid disaster assessment. In this study, a method for data synthesis to restructure fragility curves is proposed, with respect to the actual gathered damage information. Either the mean or the standard deviation of the prior fragility curve is updated based on collected building damage datasets after recent earthquakes. As a result, the restructured fragility curves with the updated mean values show better estimations than the original ones.

兵庫県南部地震以降の被害地震データに基づく建物被害関数の検討

Vulnerability functions of buildings are examined based on the damage survey data in seven earthquakes occurred in 2003 to 2008. The building damage ratios show lower correlation with peak acceleration, but higher correlation with instrumental seismic intensity or peak velocity. The obtained vulnerability functions, in comparison with the previous ones based on the data in the 1995 Kobe earthquake, are that 1) the damage ratios increase more rapidly with increase of ground motion intensity, 2) the damage ratios are lower at the same intensity level and 3) the difference of the functions for older and newer buildings is smaller.

The Approach on Making Empirical Earthquake Damage Matrix Complete Using Beta Distribution

In recent years, many earthquakes occurred in our country. Some is big, but most are small or middle earthquakes. Usually earthquake damage ratio of buildings in low intensity area can be attained from on site survey. But it is important that how to evaluate the seismic performance of existing building stock subjected to high intensity in earthquake-affected area. In this paper, the expectation and variance value of damage probability in known intensity is calculated by making the probability disperse. Supposing that the damage probability in each intensity obeys to Beta distribution. The expectation and variance value of damage probability in other intensity is given by comparing to that of criterion earthquake damage matrix. So the parameter of Beta-distribution function is calculated from the expectation and variance in other intensity. Then the probability of each damage grade in other intensity is gained. This approach makes the damage matrix which is suitable for this region complete and provides the reference for earthquake damage prediction and earthquake economic loss evaluation. The result showed that this approach is feasible.

EVOLUTIONAL BUILDING DAMAGE PREDICTION

We hypothesized that the scale of the predicted Nankai Earthquake will increase gradually year by year as the time passes from the last occurrence in December 1946, and then we estimated strong motions chronologically from 2009 to 2060 for western Japan based on the up-to-date strong motion prediction method, i.e., the so-called statistical Green's function method with hierarchical source heterogeneities. Next, we input the derived chronological strong motions into a set of nonlinear response analysis models proposed by Nagato and Kawase and estimated building damage ratios for different structure types and numbers of floors. When we compare the evolutional damage ratios of buildings in the subject regions with those for the reference case (corresponding to the scenario that will happen in 2036), we found that for every 10 years of delay in occurrence of the mega-thrust Nankai event we must expect 40% of increase in building damage, mainly in the epicentral areas.

DAMAGE PREDICTION MODELS FOR REINFORCED CONCRETE BUILDINGS BASED ON NON-LINEAR ANALYSIS WITH SOIL-STRUCTURE INTERACTION

It is very important to construct analytical models that can express the actual seismic strength of buildings in order to estimate the damage of building against the future earthquakes. Nagato and Kawase (2001) create such models by comparing the building damage ratios based on the damage statistics of RC (reinforced concrete) buildings during the Hyogo-ken Nanbu earthquake and those of the nonlinear response analyses of buildings models assumed from the current building code using simulated strong motions. In this paper, Nagato's models are improved by considering both the effect of amplification of the earthquake motion in the surface sediments and the effect of the soil-structure interaction. As the results, more appropriate models are proposed, especially for 9- and 12-storied RC buildings.

人工衛星SAR画像による被害地域検出手法の2004年新潟県中越地震への適用と高度化

Building damage detection technique which we had developed, has been successfully applied to past earthquakes such as the 1995 Kobe, the 2001 India, and the 2003 Bam, by using the compound index, z-value, which is the value derived from the correlation and difference in intensities between pre- and post-event SAR images. This technique was applied to the affected areas due to the 2004 Niigata-ken Chuetsu earthquake on October 23, 2004, by using one pair of Radarsat images taken before and after the earthquake. However, it was not possible to identify any significant distribution of damaged buildings. In this study, we examined the reason and proposed a new technique by using two pairs (pre-seismic and co-seismic) of SAR images, to identify smaller building damage ratios in less densely built-up areas compared to previous techniques. The main idea is to minimize the effect of signal noise and tempral changes of the earth's surface, on building damage estimation, by calculating the difference values from the two pre-event images and one post-event image. In a macroscopic point of view, the distributions of the both deference values of z-value and correlation coefficient in built-up areas were in good agreement with damage by survey reports. In Yamakoshi village, located in highland, we also could identify large-scale landslides with accuracy as good as interpretation from aerial photos.

耐震診断結果に基づく低層鉄筋コンクリート造学校建物の地震被害率の予測に関する研究

In this paper, an earthquake response analysis model which appropriately evaluates actual seismic performance of low-rise reinforced concrete school buildings based on seismic performance indices is proposed. Damage ratios of buildings during the 1995 Hyogo-ken Nanbu earthquake are calculated using this model and observed seismic ground motions. As a result, the relationships between an index of seismic ground motion and calculated damage ratio of buildings show good agreement with vulnerability function based on actual damage data of buildings in Hyogo-ken Nanbu earthquake. In addition, it is pointed out that damage ratio of buildings could be overestimated, if load carrying capacity which has not been considered in the seismic design is not properly evaluated.

GISを活用した地震損害評価システムの構築

A loss estimation system for earthquake hazard capable of evaluating all of Japan was developed. A GIS (Geographic Information System) for personal computers is utilized for this system, which assists in interactive selection of the assumed earthquake and representation of the estimated results on a computer screen. Source parameters of the assumed earthquake can be derived from a database of active faults and historical earthquakes. Earthquake ground motion, liquefaction and earthquake-triggered fire are considered in order to estimate building damage ratios. An insurance company's exposure can quickly be estimated by linking this system to an insurance contract database.