Rapid Visual Assessment to Classify Residential Houses Typology and Predict Population Vulnerability to Earthquake in North Bandung, Indonesia

Earthquake results in much damage and losses around the world, however the majority of fatalities due to earthquake is not due to the earthquake itself, but due to structural damage because of earthquake. The risk of structural damage will increase if the structures are not built with sufficient quality. Residential houses are an example of buildings that are more prone to earthquake damage, because typically residential houses are non-engineered and built without specific consideration against earthquake. It is estimated that 80% of buildings in cities in Indonesia are residential houses, making them vulnerable to earthquake. Not only that, areas with more percentage of poor households are more likely to experience a greater negative impact due to earthquake disasters. This indicates that there are differences in the quality of buildings that lead to differences in buildings vulnerability to disasters even between economic classes. This paper investigates structural typology of residential houses in Bandung and the differences of structural parameter between two economic classes and then extends these findings to calculate population risk. The method used is by conducting rapid visual screening and interviews in several sub-districts in North Bandung, which is considered vulnerable to its proximity to the nearest fault of Bandung city, the Lembang Fault. From this field survey, the residential houses are classified based on EMS98 type of structures. The field survey investigated 406 houses, out of which 27 socio-economic data and 15 detailed house characteristics data are obtained. Prediction of population vulnerability due to earthquake is calculated using the Lembang Fault earthquake scenario with the assumption that the population in one sub-district has the same distance from the epicenter. The results show that the residential houses consist of 57.9% confined masonry, 35% RC infilled frame, and 7.1% unconfined masonry. The average number of floors owned by the high economy class is two, with an area about 200 m² per building floor. While the average wall thickness is 250 mm with a distance between tie columns 2.5 m, the average number of floors owned by the low economy class is one, with an area per building floor at 72 m². The average wall thickness is 150 mm with a distance between tie columns of about 3 m. The results also show that if Bandung is shaken by the scenario of an earthquake caused by the Lembang Fault with a magnitude of 7, 20% of the houses will not be damaged, 34% have damage level 1, 35% have damage level 2, 11% have damage level 3, and 1% suffer damage level 4.