1990 Luzon earthquake

Geology
Based on preliminary analysis, cases and controls were similar in age and sex distribution. Similar proportions of cases and controls were inside (74% and 80%, respectively) and outside (26% and 20%, respectively) buildings during the earthquake. For persons who were inside a building, risk factors included building height, type of building material, and the floor level the person was on. Persons inside buildings with seven or more floors were 35 times more likely to be injured (odds ratio [OR]=34.7; 95% confidence interval [CI]=8.1-306.9). Persons inside buildings constructed of concrete or mixed materials were three times more likely to sustain injuries (OR=3.4; 95% CI=1.1-13.5) than were those inside wooden buildings. Persons at middle levels of multistory buildings were twice as likely to be injured as those at the top or bottom levels (OR=2.3; 95% CI=1.3-4.2).[15]

Patterns of damage
The earthquake caused different patterns of damage in different parts of Luzon Island. The mountain resort of Baguio was most severely affected, probably because it had the highest population density and many tall concrete buildings, which were more susceptible to seismic damage. Because all routes of communication, roads, and airport access were severed for several days, relief efforts were also the most difficult there. Relief efforts were further hampered by daily drenching, cold rains. Because Baguio is home to a large mining company and a military academy, experienced miners and other disciplined volunteers played a crucial role in early rescue efforts. Rescue teams arriving from Manila and elsewhere in Luzon were able to decrease mortality from major injuries. Surgeons, anesthesiologists, and specialized equipment and supplies were brought to the area, and victims were promptly treated. Patients requiring specialized care (e.g., hemodialysis) not available in the disaster area were airlifted to tertiary hospitals in metropolitan Manila. Outside of Baguio, destruction tended to be more diffuse. Damage was caused by landslides in the mountains and settling in coastal areas. Relief efforts in these areas were prompt and successful, partly because the areas remained accessible.[15]

On July 19, 3 days after the earthquake, the priority of relief efforts shifted from treatment of injuries to public health concerns. For example, numerous broken pipes completely disrupted water systems, limiting the availability of potable water, and refugees who camped in open areas had no adequate toilet facilities. Early efforts at providing potable water by giving refugees chlorine granules were unsuccessful. Most potable water was distributed from fire engines, and DOH sanitarians chlorinated the water before it was distributed. Surveys of refugee areas showed few latrines; these had to be dug by the DOH.[16]