|Corporal Damage as Related to Building Structure and Design: The Need for an International Survey (Centre for Research on the Epidemiology of Disasters, 1989, 16 p.)|
Research is therefore needed in two directions, i.e. (1) to identify the hazards of different types of housing structures as related to earthquakes, in view of providing planners, architects and structural engineers with a quantitative assessment of risks; (2) to determine the response of trapped victims.
These studies are complementary. The dual objective is to provide a basis for the design of safer structures, and to contribute to a better planning of emergency and rescue services. This approach does not have to be restricted to earthquake, and could be extended to other types of natural disasters where the interaction of houses and occupants play a major role, mainly atmospheric hazards such as wind storms, tornadoes, hurricanes and tropical cyclones.
Such studies have been carried out extensively for automobile and traffic accidents, aircraft crashes, and industrial accidents, but to no significant extent for habitation.
(1) Regarding the identification of hazards associated with building structure, some data are available from the literature.
An interesting observation is that previously, following earthquakes, the ratio of casualties requiring medical care to deaths was approximately (within a large range) 3 to 1. Now, as shown in Armenia, it could come close to 1 to 3 (5). It seems that earthquakes in the ecology of large industrialized or developing urban areas is becoming a killer, with few casualties and many deaths.
In Guatemala, 1976, the adobe houses especially when overcrowded were the most lethal. No relation was observed with the type or roof or the number of doors and windows. The worst houses were those with heavy adobe block held by weak mud mortar. The best were chose with non-adobe lightweight cornstalk walls supported on a wooden frame; if the walls collapse, the frame and the roofs remain intact. Houses older that 7 years had a higher risk, with 1.6 times more casualties, than newer ones, since age tends to dry out the bricks and make them brittle. The size of the adobe blocks had no relation with the severity of injuries (1).
In Jalapa, Guatemala, after the same earthquake in 1976, a survey of the survivors showed that 11.5 of the admitted in the hospital casualties had fractures of the clavicle, suggesting that they were hit by falling roofs, walls, or beams (6).
In China, a large number of pelvic fractures were reported after the Hsing Tai earthquake, totalizing 30 % of all cases admitted to hospital (7), while only 32 cases of such fractures were noted in Tangshan estimated at 240.000 dead.
High rates of crush syndrome in the rescued survivors are at times reported (16 % in Agadir, 5.5 % in Skoplje) (8,9), whereas in other occasions none is mentioned, what suggests that either rescue was quite fast or more probably came too late.
Such data are scarce, and most of the time they were collected in a haphazard manner or are just chance observation. No systematic survey of deaths and casualties associated to building structure have been carried out. There are of course good reasons for this lack of data, since at the site of an earthquake all efforts are directed to immediate rescue.
Two research programs should be envisaged, one on a macrolevel, the other more on a more detailed scale.
The first research should assess the probability of death and casualty according to the type of housing (style, type of material, number or floors, age).
The second research should aim at identifying individual building characteristics responsible for deaths and casualties (ornaments, material, design). It will require a careful evaluation of the body damages, and to the extent possible should include forensic determination of the immediate cause of death.
Surveys on body damage and structures will have to take into account other major variables, mainly behavior at the tine of impact, and rescue procedures. Such data will incidentally have a bearing for defining the appropriate protective behaviors that the population should be taught, as well as improving training for rescue and designing appropriate non counterproductive rescue procedures.
Studies should also be conducted on the hazards associated with anti-seismic structures. It may happen that people survive well in building damaged beyond any repair, and conversely. The correlation of damage to antiseismic structures and casualties should therefore be further investigated, in order to develop failure models compatible with prevention of human losses.
(2) With respect to search and rescue, the response of trapped victims surviving the impact determine their chance to be extricated alive in a given period of time. Since it is obviously impossible to conduct cohort survival studies from the time of impact, chances of survival can only be estimated indirectly, by comparing the proportion of victims extricated death or alive at different times after impact. Data should be collected on the absolute number extricated dead or alive by periods of time (hours or days), or as cumulative figures over time after impact. Different patterns may emerge, which will give indication on the effectiveness of rescue and on the efficiency of extrication procedures.
Such observations however do not provide indication on when the dead victims actually died, and how much time the ones alive would have survived further. Still included among the deaths will be those victims who were killed at impact, and for whom earlier rescue would have made no difference. Determination of the cause of death, including wherever possible autopsies in at least a subsample, could provide some indication on the size of this group.
Since the objective of such studies is to determine delay in rescue for effective emergency health care, it should take into account the long term survival of the victims which were finally extricated alive, making provision for those who are beyond chance of survival at time of rescue.