Mitigation - Disaster Mitigation Guidelines for Hospitals and other Health Care Facilities in the Caribbean (Pan American Health Organization (PAHO) / Organización Panamericana de la Salud (OPS), 1992, 76 p.): Chapter 2: The nature of natural hazards in commonwealth Caribbean countries: General definitions

Mitigation - Disaster Mitigation Guidelines for Hospitals and other Health Care Facilities in the Caribbean (Pan American Health Organization (PAHO) / Organización Panamericana de la Salud (OPS), 1992, 76 p.)

Chapter 2: The nature of natural hazards in commonwealth Caribbean countries

		Introduction
		General definitions
		Earthquakes
		Volcanoes
		Hurricanes
		Floods

General definitions

At the outset, some basic concepts and information are necessary in order to better understand the contents of this booklet.

Hazard

A hazard is a phenomenon which, when it manifests itself in a given area over a specific period of time, has the potential for severe social disruption, trauma, property damage and loss.

The potential impact of a hazard is normally expressed in terms of its magnitude or intensity, which are expressed as a probability function over a specified time period according to hazard type. Hazard functions can be derived for different sites if there are sufficient relevant records going back over a significant period of time. For example, if we analyze the known history of earthquake occurrences in the Eastern Caribbean countries, and we measure their size in terms of the intensities given by the Modified Mercalli Intensity Scale, we will find that not all countries are under the same seismic hazards.

Vulnerability

Vulnerability is a measure of the intrinsic susceptibility of structures, contents and processes to fail once they are exposed to potentially damaging natural phenomena.

Vulnerability is generally expressed as the degree of expected damage or loss, given in a certain scale, as a function of hazard intensity.

Risk

Risk is a measure of the probability of expected loss for a given hazardous event.

Structural Elements

The portions of a building that support it and resist gravity, earthquakes, hurricane winds and other type of loads are said to be the structural elements.

The structural elements of buildings include columns (pillars), beams (girders and joists), floor or roof sheeting, slabs or decking, load bearing walls and foundations.

Non-structural Elements

The non-structural elements of a building include every part of it and all of its contents with the exception of the structure. Common non-structural items include ceilings, windows, laboratory equipment, inventory stored on shelves, computers, electrical equipment, furnishings and light fittings.