Natural Hazards: Causes and Effects - Disaster Management Center ...

Chapter 2
Earthquakes
Introduction
Earthquakes are one of the most dangerous and destructive forms of natural hazards. They
strike with sudden impact and little warning. They may occur at any time of day or on any day
of the year. An earthquake can devastate an entire city or a region of hundreds of square
kilometers. They can reduce buildings to a pile of rubble in seconds, killing and injuring their
inhabitants.
Earthquakes are caused by the movement of massive land areas, called plates, on the earth’s
crust. Often covering areas larger than continents, these plates are in a constant state of
motion. As the plates move relative to one another, stresses form and accumulate until a
fracture or abrupt slippage occurs. This sudden release of stress is called an earthquake.
Historical Examples
Managua, Nicaragua, December 23, 1972
On December 23, 1972, a series of earthquakes shook the Central American nation of
Nicaragua. The largest earthquake registered 6.2 on the Richter scale. The earthquake’s
epicenter was located precisely at the capital city of Managua. The earthquake resulted in the
destruction of the heavily populated central zone and damage to a total area of about 27 square
kilometers (10 square miles). Subsequent fires blazed throughout the city, compounding the
damages. In the wake of the disaster, at least 8,000 of Managua’s total population of 430,000
had died, 20,000 were injured, over 260,000 had fled the city, 50 percent of the employed were
jobless, and 70 percent were left temporarily homeless. At least 10 percent of the nation’s
industrial capacity, 50 percent of commercial property, and 70 percent of government facilities
were rendered inoperative. Overall, the U.S. dollar damage was estimated at $845 million. 1
The city had been destroyed by previous earthquakes, but the capital was always rebuilt and
expanded on the same location. It is, therefore, understandable that a major issue after the
1972 earthquake concerned future decentralization or relocation of the city.
As is common in many developing countries, the capital is the focal point of the most productive
activities, including those of trade, industry, and financial services, as well as the site of the
central government. Thus, in addition to the loss of life and to property damage, the cost of
temporary upsets in public administration and disruption of economic activity must be taken into
account.
The sectors that were hardest hit by the earthquake were housing, retail trade, and small
manufacturing. These were concentrated in the over-crowded city-center closest to the
epicenter of the earthquake. The massive destruction was due in part to their location, but also
to inadequate building materials, structural deficiencies, and the absence of laws regulating
construction.
Although this earthquake was quite localized, it struck directly at the economic and
administrative heart of Nicaragua and left its mark for years to come. The public sector entered