Natural disaster
What is an earthquake?
Apr
Earthquake is the ground shaking caused by sudden loads and movement of geological blocks in the Earth’s crust.
Earthquake
can occur for various reasons, including movement of geological blocks, geological radiation, volcanic activity, tectonic shifts, and hydroelectric activity. Earthquakes can trigger different phenomena, including ground damage, landslides, tsunamis, and other consequences such as loss of life and property.
1. What is an Earthquake?
Earthquake or Seism is the shaking of the Earth’s surface due to the sudden release of energy in the Earth’s crust, generating seismic waves. Seismic activity in an area is the frequency, type, and magnitude of earthquakes experienced over time. The term “seismic tremor” is also used for ground vibrations that do not cause earthquakes. Earthquakes also occur on planets and satellites with solid outer crusts similar to Earth.
Earthquake is a natural phenomenon that often occurs on Earth, especially in areas along geological plate boundaries or near tectonic edges. Earthquakes can be measured using seismographs and evaluated on the Richter scale. Strong earthquakes can cause serious destruction to residential areas, buildings, and infrastructure, making forecasting and response critical to reduce impacts on humans and the environment.
2. Causes of Earthquakes
The causes of earthquakes can be diverse, but most are due to movement and pressure between geological blocks in the Earth’s crust. Key causes include:
- Separation of geological blocks: Movement of geological blocks apart can cause significant earthquakes, especially in areas with complex terrains.
- Collision of geological blocks: When two blocks collide, they create pressure and reaction forces, causing earthquakes.
- Volcanic activity: Eruptions and expansion of volcanoes can trigger earthquakes.
- Geological radiation: Emission from radioactive rocks may cause earthquakes, particularly in areas with high radioactive rock concentration.
- Human activities: Mining, infrastructure construction, and other civil works can also trigger earthquakes.
- Natural disasters: Phenomena such as landslides, tsunamis, and forest fires can also lead to earthquakes.
3. Types of Earthquakes in Nature
a. Earthquake Fault Types
- Thrust fault: occurs when the rock on one fault surface moves up or down relative to the rock beneath. Thrust faults frequently occur in high mountain regions. Example: Nepal earthquake in 2015.
- Strike-slip fault: occurs when two rock blocks on fault surfaces move parallel horizontally. Strike-slip faults often occur in mountainous regions or at tectonic plate boundaries. Example: San Francisco earthquake in 1906.
b. Off-fault Earthquake
- Off-fault earthquakes occur in areas not directly associated with active tectonic boundaries. They usually occur near active fault zones and may result from stress transfer to distant rock regions.
- Off-fault earthquakes are difficult to predict and can cause significant effects in nearby areas, such as landslides, tunnel closures, building damage, and infrastructure disruption.
c. Clustered and Deep-focus Earthquakes
- Clustered earthquake: a series of consecutive earthquakes occurring in a specific region over a short period. This differs from dispersed earthquakes, which are scattered in time and space.
- Deep-focus earthquake: occurs at depths of 300–700 km beneath the Earth’s surface, below tectonic plate boundaries. These earthquakes usually cause minimal surface damage due to their depth but generate strong seismic waves affecting nearby areas.
d. Volcanic Earthquakes
- Volcanic earthquakes are caused by volcanic activity, including changes in internal pressure, movement of magma, and redistribution of volcanic materials during eruptions.
- Volcanic earthquakes are generally shallow and low-intensity, but they can increase eruption risks and impact surrounding areas.
4. Earthquake Intensity Scale
- 1–2 on the Richter scale: Not perceptible
- 2–4: Perceptible but causes no damage
- 4–5: Ground shakes, audible noise, minor damage
- 5–6: Buildings sway, some structures may crack
- 6–7: Triggers landslides, volcanoes may erupt
- 7–8: Strong, destroys most ordinary buildings, major cracks or subsidence
- 8–9: Very strong, destroys nearly entire towns, large cracks, partial building collapse
- Above 9: Extremely rare
- Above 10: Extremely rare, total destruction
5. Earthquake Early Warning
Earthquake early warning is crucial to minimize damage. Methods include:
- Sensor systems: Installed worldwide to detect earthquake signs, measuring ground movement and seismic waves, sending alerts to seismic stations.
- Seismic networks: Detect earthquake signals and send early warnings to seismic stations.
- Geological sensors: Installed on land and oceans to detect earthquake activity and alert stations.
- Social media: Can be used to share earthquake alerts and warnings with the public.
Earthquake Early Warning System
However, early warning methods are not perfect and cannot precisely predict time, location, or intensity. Therefore, preparedness and practicing earthquake response skills are essential to ensure safety.
6. Measures to Mitigate Earthquake Consequences
Earthquakes can cause severe human and property damage. Mitigation measures include:
- Rescue and first aid: Deploy rescue teams immediately to help victims trapped during earthquakes.
- Ensure essential supplies and safety: Provide food, water, and medical supplies to affected areas while ensuring safety and security.
- Reconstruction of infrastructure: Restore roads, electricity, water, and telecommunications, rebuilding according to earthquake-resistant standards.
- Training and awareness: Educate the public and officials to improve earthquake preparedness and response.
- Investment in research and new technologies: Develop sensors and monitoring systems to reduce earthquake damage.
- Financial and social support: Provide funds, psychological counseling, and social assistance to victims and families.
7. Post-Earthquake Rescue Operations
Rescue operations ensure the safety of trapped, injured, or missing individuals. Activities include:
- Searching and rescuing victims from rubble: Rescue teams locate victims, extract them from debris, and transport them to safe areas for treatment.
- Providing first aid: Treat and transport injured individuals to nearby hospitals.
- Supplying water, food, and necessities: Deliver essential supplies to affected communities.
- Finding missing persons: Use modern technologies, sensors, and monitoring equipment to locate missing individuals.
- Organizing relief activities: Support displaced people and those who lost property or income through relief efforts.
An Earthquake Destroying Entire Buildings
