Natural Hazards in Puerto Rico

Abstract

TOURISM literature portrays Puerto Rico as an American paradise, a destination for tourists interested in the casinos and nightlife of San Juan or the natural beauty of the Caribbean beaches and El Junque National Forest. Yet Puerto Rico also has a sizable potential for natural disasters. Each year, from July to November, a series of hurricanes passes through the Caribbean region. One such storm, Hurricane Hugo, struck Puerto Rico and the Virgin Islands on 18 September 1989. Hugo caused an estimated $1 billion in damage and destroyed some five thousand homes, especially in areas of unregulated development on hillsides, coastal areas, and floodplains (FEMA 1989). The aftermath of Hurricane Hugo provided an opportunity to assess attitudes toward and responses to natural hazards, including earthquakes, tsunamis, hurricanes, coastal floods, riverine flooding, and landslides. This article presents an overview of the types of natural hazards that beset Puerto Rico and summarizes the results of a sample survey that measured both the perceived vulnerability to these hazards and the factors that affect the adoption of mitigation measures. GEOPHYSICAL SETTING AND HAZARD VULNERABILITY The interaction of geophysical risk and human settlement makes the Caribbean region especially vulnerable to natural hazards (Cross 1992). Puerto Rico shares in that risk. Situated near the subduction zone between the North American and Caribbean tectonic plates, Puerto Rico lies in what has been called one of the most earthquake-prone regions of the world (Hays and Gori 1984, 13). The first recorded damaging earthquake, which occurred in the 1520s, destroyed the home of Ponce de Leon (McCann 1984, 41). Other major earthquakes occurred in 1717, when the San Felipe Church in Arecibo was completely ruined; in 1787, when great damage was done to the El Morro and San Cristobal forts in San Juan and many churches and large buildings were destroyed; and in 1867, when a quake centered in the Virgin Islands caused damage in eastern Puerto Rico. Although the island population has experienced frequent smaller shocks, the last disastrous earthquake occurred in October 1918. This 7.5-magnitude quake, which had its epicenter in the Mona Passage, spurred a tsunami that drowned many residents and destroyed many dwellings on the west coast of Puerto Rico. Overall, the disaster claimed 116 lives and $4 million in property damage. Most damage to buildings occurred in areas where the structures had been erected on alluvium. Areas in the San Juan region are at risk of intense ground shaking, especially along the floodplains of the Rio Bayamon, Rio Piedras, and Rio Grande de Loiza (Molinelli 1987). These floodplains contain large numbers of high-rise buildings and housing units as well as airport facilities, roads, and water mains. In addition, about 17 percent of the region is susceptible to liquefaction, and other areas, especially the southern part of the metropolitan region, face risks of earthquake-induced landslides. The high earthquake vulnerability of Puerto Rico relates to the location of large numbers of buildings and infrastructure in especially hazardous zones. Although earthquakes occur infrequently, a single event can cause catastrophic damage and numerous casualties. Connected with the earthquake hazard is the risk of seismically induced tsunamis. These cataclysmic waves form when large masses of displaced earth in ocean basins disturb the overlying water column. Generally, tsunamis occur at large subduction zones, as in the Caribbean region. One of the more dramatic tsunamis there occurred on 18 November 1857, triggered by an earthquake in the Anegada trough between St. Croix and St. Thomas. The event delayed the United States' purchase of the Virgin Islands for fifty years and damaged settlements not only in the Virgin Islands but also in Vieques, Yabucoa, and Fajardo in eastern Puerto Rico (Lander and Lockridge 1989). As noted earlier, another tsunami, which hit the opposite end of the island, was associated with the 1918 earthquake. …