The U.S. Commonwealth of Puerto Rico lias a population of 3.8 million (2000 Census), a higher population density than any U.S. state. The island, approximately 160 km east to west by 5 0 lcm north to south, is bounded by offshore active faults on all sides. Numerous local and regional events in the recorded history with M > 7.0, some of which have generated tsunamis, have caused extensive damage to local infrastructure, though the last significant ground motions were felt onshore in 1918. The U.S. Geological Survey hazard maps (Mueller et al. 2003) indicate chat the seismic hazard is similar to the Basin and Range province in the Western United States, and the island is assigned Seismic Zone 3 in the current standard building code in Puerto Rico, the 1997 UBC. The significant hazard, combined with the large population and untested infrastructure, results in a potentially devastating combination for Puerto Rico.
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