Natural Hazards and Risk Assessment
1. Earthquake Comparison: Indonesia vs. Japan
In 2007, a significant earthquake struck Java Island, Indonesia, resulting in 45 fatalities. A month later, a similar magnitude earthquake occurred in a densely populated area of Japan, but resulted in no fatalities. This difference in outcome can be explained by examining hazard, exposure, and vulnerability.
Hazard: Both regions experienced earthquakes of similar magnitude, indicating a similar level of seismic hazard.
Exposure: While both areas were exposed to earthquakes, the Japanese area had a higher population density, meaning more people and infrastructure were potentially at risk.
Vulnerability: The key difference lies in vulnerability. Japan’s superior building codes and earthquake-resistant infrastructure significantly reduced the vulnerability to damage and loss of life, compared to Indonesia’s infrastructure.
2. Eight Natural Hazards
- Volcanoes
- Earthquakes
- Tsunamis
- Flooding
- Subsidence
- Slope Processes
- Drought
- Wildfires
3. Risk Factors
Hazard: The potential for a catastrophic event.
Exposure: The number of people and assets potentially affected by a hazard.
Vulnerability: The susceptibility of people and assets to harm from a hazard.
4. The 3 “P’s” of Risk Management
Prediction: Attempting to determine the precise time, location, and magnitude of a future event. Often used interchangeably with forecasting.
Prevention: Implementing measures to avoid or minimize the impact of a hazard.
Preparedness: Developing plans and actions to respond to and recover from a hazard event.
5. Geological Hazards
| Internal Geological Hazards | External Geological Hazards |
|---|---|
| Volcanoes | Landslides |
| Earthquakes | Flooding |
| Subsidence | Tsunamis |
6. Deadliest Natural Hazards
Earthquakes, volcanic eruptions, and tsunamis are among the natural hazards that cause the most fatalities worldwide annually.
7. Direct and Derived Volcanic Risks
- Magma expulsion
- Emission of toxic gases
- Pyroclastic flows (glowing clouds)
- Explosions
- Lahars (volcanic mudflows)
- Lava flows
8. Most Dangerous Volcanoes and Their Location
All volcanoes pose a potential danger, even dormant ones, as they can erupt again. Volcanoes are primarily located along tectonic plate boundaries.
9. The Armero Tragedy (Nevado del Ruiz, Colombia) 1985
(Addressing the original questions a, b, and c requires more context from the referenced source. Please provide the relevant excerpt.)
10. Locating an Earthquake’s Epicenter
The epicenter is determined using data from at least three seismic stations.
11. Seismic Scales
(The provided information appears to describe the Mercalli Intensity Scale, which measures the observed effects of an earthquake. It’s important to differentiate this from magnitude scales like the Richter scale, which measure the energy released.)
12. Earthquake Prediction, Forecasting, and Prevention
Prediction: Currently, it is not possible to accurately predict the time, location, and magnitude of earthquakes.
Forecasting: While precise prediction remains impossible, scientists can identify high-risk areas based on geological data and fault lines.
Prevention: This involves implementing building codes and land-use planning to minimize the impact of earthquakes.
13. What to Do During an Earthquake
- Have an action plan and emergency contact numbers.
- Secure objects that could fall and cause injury.
- Move to an open area away from buildings.
- After the earthquake, check on family and neighbors.
- Remain calm and assist others.
- Do not move seriously injured people unless they are in immediate danger.
14. Types of Landslides
- Slide: Movement of a cohesive block of material along a surface.
- Fall: Free fall of material through the air.
- Flow: Movement of water-saturated material like a viscous fluid.
15. Subsidence and Collapses
Subsidence: Gradual sinking of the Earth’s surface.
Collapse: Sudden sinking or caving in of the ground.
16. Flood Prevention Measures
- Improve and maintain river channels and drainage systems.
- Construct appropriate infrastructure for channeling water.
- Implement land-use planning to avoid building in floodplains.
17. Cold Drop (Gota Fría)
A cold drop, or “gota fría,” is a meteorological phenomenon in Spain where a cold air mass collides with warm, moist air, resulting in intense rainfall and flash floods.
18. Definitions
Lahar: A volcanic mudflow.
Torrential Rainfall: Heavy rainfall, often associated with flash floods.
Pyroclastic Flow: A fast-moving current of hot gas and volcanic matter.
Hypocenter: The point of origin of an earthquake within the Earth.
Tsunami: A series of ocean waves caused by underwater disturbances.
Piroclast: A fragment of volcanic material.
(Definitions for “raptacion” and “seismic magnitude, Mercalli scale” were not provided in the original text.)
19. 2004 Indian Ocean Tsunami
The 2004 Indian Ocean tsunami was triggered by a massive undersea earthquake off the coast of Sumatra, Indonesia. The resulting tsunami devastated coastal communities across the Indian Ocean, causing widespread destruction and loss of life. The earthquake and tsunami are considered one of the deadliest natural disasters in modern history.
20. Natural vs. Man-Made Disasters
Disasters can be natural, such as earthquakes and tsunamis, or man-made, such as industrial accidents and infrastructure failures.