INTRODUCTION

Central America consists of seven small countries between Mexico and Colombia, most of which are afflicted by earthquakes and volcanic eruptions. These include Guatemala, Belize, Honduras, El Salvador, Nicaragua, Costa Rica, and Panama. All were formerly ruled by Spain except for Belize, which was formerly British Honduras and is the only country not in danger from earthquakes or volcanoes. Mexico tried unsuccessfully to annex the five countries of Guatemala, Honduras, El Salvador, Nicaragua, and Costa Rica after they declared their independence from Spain, but the Central American countries, led by Guatemala, broke away and formed the United Provinces of Central America, which itself broke up into separate countries in 1838. Panama was formerly part of Colombia, but achieved its independence in 1903 with the backing of the United States because it was the site of the future Panama Canal. Most of these countries have had difficult, even violent, political histories (LaFeber, 1983), with the exception of Costa Rica, which became a democracy and did away with its army. Costa Rica is not a wealthy country, but it is a stable one.

The five countries from Guatemala to Costa Rica contain one of the densest concentrations of active volcanoes in the world (inset, Figure 26.1). In addition, the Middle America subduction zone has generated many earthquakes, but this subduction zone is very different from the Mexican subduction zone to the north. Both subduction zones involve the Cocos plate, but the dip of the oceanic Cocos plate opposite Central America is much steeper than it is in Mexico. Because of this steep dip, earthquakes on this subduction zone are offshore and have not produced a hazard as high as earthquakes on the low-dipping Mexican subduction zone. People have lost their lives in Middle America subduction zone earthquakes, but the magnitudes are smaller, and none have been as large as magnitude 8.

A greater hazard is earthquakes in continental crust, generated on faults close to Central American volcanoes. In Guatemala, El Salvador, and Nicaragua, many of these faults tend to be strike-slip, in which crust closer to the ocean moves northwest during an earthquake, parallel with the coastline, with respect to the crust in the interior.