Earthquake and Volcanic Hazards: Causes, Effects, and Prevention

Earthquake Causes, Effects, and Prevention

Causes of Earthquakes

• Regional-Global Scale: Lithospheric subduction zones (cause of large earthquakes).
• Local Causes:
  • Volcanic eruptions
  • Escape of materials related to large surface currents
  • Fractures
  • Fluid extraction: groundwater, petroleum
  • Excavation collapse: mining, filling of reservoirs

Effects of Earthquakes

• Shaking of soil and buildings (the majority of deaths are caused by the collapse of buildings).
• Ground displacements taking place across fault lines.
• Landslides (a violent earthquake can trigger thousands of them).
• Tsunamis or tidal waves (traveling at high speed).
• Explosions: nuclear tests, exploration for mineral and oil deposits, mining operations.

Increased Seismic Risk Factors

• Human overpopulation in areas at risk (e.g., California).
• Human settlements in active fault zones.
• Human settlements in areas of unconsolidated land (sand, gravel).
• Construction of low quality.
• Value of goods involved (industrialized countries).
• Age of the population.

Seismic Risk Prevention Measures

Seismic Risk Prevention

These measures are based on the study of seismic precursors (seismic monitoring networks) and prior knowledge of risk areas.

Seismic Precursors: Increased intensity and frequency of micro-earthquakes in active fault zones.

Measures for Prevention of Seismic Risk

• Delimitation of areas of risk (risk maps).
• Land use planning.
• Restriction of construction and settlement in areas of faults and landslides.
• Earthquake-resistant building regulations (structural design).
• Emergency response infrastructure (equipment, services).
• Contracting insurance.

Seismic Risk in Spain

In the peninsula, the areas of highest risk are the South and Southeast, the Catalan Coastal Range, and the Iberian System. In the Canary Islands, seismic risks are associated with volcanism. The coastal areas may be affected by tsunamis of low intensity.

Risks Due to Tectonic Deformation

Folds and fractures are permanent deformations that alter the arrangement of rocks and their properties. They pose some risk to people and infrastructure.

Types of Tectonic Deformations

• Regional-Scale Deformation: Large strains associated with lithospheric plate dynamics.
• Local Deformations: Small deformations.

Effects and Risk of Tectonic Deformations

• Mass movements of sets for fracture surfaces.
• Fracture or discontinuity surfaces that cause landslides on hillsides.

Volcanic Hazards

Characteristics of Volcanic Hazards

Volcanic hazards are less visible to the public and are often caused by volcanoes that have been inactive for long periods, providing a false sense of security. Volcanic eruptions are very dangerous phenomena.

Risk Factors of Volcanic Hazards on Human Settlements

The risk from volcanoes is increased remarkably by the fact that millions of people around the world live in hazardous volcanic regions, attracted by their fertile soils.

Prevention of Volcanic Hazards

The only way to prevent the effects of a volcanic eruption is to know when it will happen, which requires thorough study. Only 1% of active volcanoes are controlled by sufficient sensors and measuring instruments.

Factors Conditioning the Danger of a Volcanic Eruption

• The explosiveness of eruptions.
• Standard exhaust products.
• Lahars.
• Lava flows.
• Characteristics of types of volcanic eruptions.
• Explosive Eruptions: They throw clouds laden with liquid magma fragments in suspension.