Understanding Earthquake and Volcanic Risks: Prevention and Safety

Posted on Mar 8, 2025 in Geology

Risks Associated with Internal Processes

Earthquake Risk

Areas with the greatest tectonic activity are the most seismically active. Causes of earthquakes include volcanic activity, landslides, and explosions from mining.

Effects of Earthquakes

Major earthquakes cause significant damage in a short time. The effects include:

  • Ground shaking and building collapse: This can result in many deaths.
  • Soil displacement: Occurs along fault lines.
  • Landslides: Violent earthquakes can trigger landslides, depending on the terrain.
  • Tsunamis: These fast-moving waves are produced by the displacement of large volumes of ocean water due to undersea earthquakes. Eruptions, landslides, and underwater explosions can also cause tsunamis. Wave heights can reach several meters, causing significant damage.

Prediction of Seismic Activity

  • Earthquakes are often preceded by shaking and ground deformation. However, these phenomena can also occur without leading to an earthquake, making them unreliable indicators.

Earthquake Risk Prevention

  • Prevention involves identifying high-risk areas and mitigating potential damage. It’s crucial to ensure the integrity of equipment and infrastructure to maintain essential services after an earthquake. Special measures in high-risk areas can reduce damage.

Risk Due to Strain

  • Folds and fractures are deformations that alter the arrangement and properties of rocks, posing risks to people and infrastructure.
  • Major tectonic deformations determine fundamental characteristics of surface regions, potentially increasing the risk of other processes. Understanding the geological history of a region is essential for prevention.
  • Small deformations can have significant short-term effects, causing problems with foundations, slope stability, and rock permeability. Studying the arrangement of fractures, including faults, joints, and cleavage, is crucial for risk prevention.
  • Joints are non-displaced fractures, while faults involve displacements of rock blocks, which can be normal or reverse.

Volcanic Hazards

  • Volcanoes can be less noticeable than earthquakes, remaining inactive for years and creating a false sense of security. However, they are very dangerous and can cause significant disasters. The energy released during an eruption can be equivalent to a magnitude 6 to 8.5 earthquake, but the release is gradual.
  • The risk is increased because millions of people live in volcanic regions, drawn by the fertile soil.

Volcanic Hazard Prevention

  • Effective prevention requires careful and constant monitoring of volcanoes. Precursors, such as magma intrusion into fractures near the surface, can be difficult to interpret accurately. Only a small percentage of active volcanoes are adequately monitored with sensors and measuring instruments.
  • If the magma is very acidic, with high silica content, it takes longer for gases to escape, leading to explosive eruptions. These volcanoes often form steep, needle-like or dome-shaped structures.
  • If the magma is basic, with low silica content, it flows smoothly, forming flatter volcanoes with non-explosive eruptions.

Dangers of Volcanoes

  • Explosiveness of eruptions: Higher gas content and viscosity increase explosiveness. Viscous, volatile-rich magma produces explosions, which can be intensified by water vapor contact. Eruptions can spew clouds of gas and liquid magma, creating pyroclastic flows that move rapidly across the surface.
  • Ejected material: Affects large areas and can collapse roofs due to its weight. Ashfall reduces visibility, and some volcanoes emit poisonous gases.
  • Lahars: Mudflows formed by rapidly melting snow and ice, possessing significant destructive capacity.
  • Lava flows: Occur when magma is fluid and contains few gases. They do not travel very far but can cause significant material damage and cover the ground.