Factors influencing severity of tectonic hazards
Tectonic Hazards
These hazards are studied in terms of their global distribution at plate boundaries, primary and secondary effects, and the social and economic impacts on different regions. They can be measured using scales like the Moment Magnitude Scale (MMS) for earthquakes and the Volcanic Explosivity Index (VEI) for volcanoes.
Factors influencing severity of tectonic hazards
Physical factors
-Magnitude and Intensity: The sheer size and strength of the event are primary factors.
-Depth of Focus (Earthquakes): Shallow-focus earthquakes cause more intense shaking and surface damage because less energy is absorbed by the crust before reaching the surface.
-Proximity to the Epicenter/Source: The effects of an earthquake are most severe at its epicenter and decrease with distance. For volcanoes, proximity to the vent increases the risk from lava flows, pyroclastic flows, and ash fall.
Factors influencing severity of tectonic hazards
Human factors
Factors influencing severity of tectonic hazards
Understanding earthquakes and their impacts
Earthquakes are caused by the sudden release of stress that builds up between tectonic plates as they move. This energy is released in the form of seismic waves, causing the ground to shake. The focus is the point within the crust where the earthquake originates, while the epicentre is the point directly above it on the surface. Shallow-focus earthquakes (0–70km deep) tend to be more destructive than deep-focus ones due to their proximity to the surface.
Factors influencing severity of tectonic hazards
Understanding earthquakes and their impacts
They occur on these plate boundaries:
-Conservative (transform) boundaries generate frequent, shallow earthquakes.
-Destructive (convergent) boundaries can produce powerful, deep earthquakes.
-Collision zones and constructive boundaries also experience earthquakes, typically of lower magnitude.
Factors influencing severity of tectonic hazards
Severity of earthquakes
The severity of a earthquake is influenced by
-Magnitude (Moment Magnitude Scale)
-Depth of focus
-Proximity to the epicentre
-Geology (e.g. soft ground leads to liquefaction)
-Human vulnerability (e.g. population density, building quality, emergency services)
Severity of earthquakes
Primary Hazards
ground shaking and surface rupture.
Severity of earthquakes
Secondary Hazards
tsunamis, fires, landslides, and disease outbreaks.
Severity of earthquakes
Other influences
The impact of an earthquake depends not only on physical processes, but also on human factors such as governance, wealth, and education. These are often compared using hazard profiles, which visually represent a hazard’s characteristics (e.g., magnitude, frequency, predictability, areal extent, and impact).
Modifying hazards (controlling/vulnerability/mitigation)
