Natural and Technological Disasters: Risks, Causes, Responses

Types of Disasters

Natural and Technological Disasters

Natural disasters: the term refers to natural phenomena. Technological disasters: those caused by human activities.

Natural Risk and Prevention

Natural risk: the probability of damage or catastrophe for the population of an area or their property. It depends on the hazard and the frequency of exposure, as well as the volume of population and property that may be affected. It also depends on the vulnerability or susceptibility a community presents to be damaged. Prediction is based on statistical data that indicate whether a particular phenomenon is common in an area.

Prevention: proposes adopting the necessary measures so that an event has minimal effects.

Earthquakes: Terms and Measures

Earthquake: ground vibrations caused by the sudden release of stored energy in rocks under stress. Large masses are subjected to forces that lead to fracture of rock. These fractures are called faults.

Hypocenter (focus): the place where the earthquake originates. Epicenter: the point on the Earth's surface nearest the earthquake focus.

Seismograph: an instrument that records graphical traces (seismograms) of earthquakes and measures their magnitude.

Magnitude: the amount of energy released by an earthquake; it is measured with scales such as the Richter scale. Each unit increase corresponds to about 32 times the energy of the previous level.

Intensity: a measure of an earthquake's effects at a specific location.

Tsunami

Tsunami: a series of very large waves caused by the sudden vertical displacement of a large volume of water at the bottom of the sea. These waves can travel long distances with little loss of intensity and often result in a sudden withdrawal of the sea before the wave arrives.

Volcanic Activity and Hazards

Volcanic activity:

• Effusive: low-viscosity lava flows out of the crater and produces small, mild pyroclastic explosions.
• Explosive: very viscous lava can obstruct conduits; gases accumulate and cause large explosions that project many pyroclasts.

Volcanic hazards:

• Toxic gases
• Burning clouds of pyroclastic flow
• Explosive ejecta
• Lahars (mudflows)
• Flows of lava

Precursors to an eruption:

• Small local earthquakes
• Changes in ground tilt or inclination
• Rising groundwater temperature in wells
• Increased gas emissions

Catchment Area (Watershed)

Catchment area: an area that includes all the territory that drains into the same river. The limit between two adjoining river basins is marked by the watershed divide. Part of the surface water flows as surface runoff.

Human Influence on Disaster Risk

Human influence: occupation of floodplains, deforestation, and covering the ground with impermeable materials all increase risk. Infrastructure can interfere with natural channels and worsen impacts.