EarthquakePowerPointPresentation-11.pptx

Earthquakes

1. Understanding Earthquakes Earthquakes are caused by sudden shifts in the Earth's crust. These shifts release energy in the form of seismic waves. The point where the earthquake originates is called the focus. The point on the surface directly above the focus is the epicenter. Earthquakes are measured using seismographs and the Richter scale. Effects can range from tremors to devastating ground shaking and tsunamis.

2. Earthquake Stress and Strain Stress: Force applied to a rock 3 Types: Compression, Tension, Shear Causes rocks to deform or break When rocks break, energy is released as seismic waves = earthquake Elastic Rebound Theory: Explains how earthquakes occur due to stress buildup and release

3. Strain and Earthquakes Strain: How rocks respond to stress Types of Strain: Elastic, Plastic, Brittle Elastic Strain: Temporary deformation, rock returns to original shape Plastic Strain: Permanent deformation, rock stays deformed Brittle Strain: Rock breaks, causing an earthquake

4. Compression and Earthquakes Compression: Rocks are squeezed together, causing them to fold or fracture. Common at convergent plate boundaries. Leads to the formation of mountains, reverse faults, and thrust faults. Can cause powerful earthquakes and aftershocks. Contributes to the Earth's dynamic landscape.

5. Elastic Deformation and Volcanic Activity Elastic deformation can cause pressure to build up within a volcano. Magma pushing upwards creates stress on surrounding rock. Rock deforms elastically, storing energy like a compressed spring. When stress exceeds rock strength, it fractures, releasing energy. This sudden release of energy causes an eruption. The eruption releases pressure, allowing the rock to return to its original shape. Cycle repeats as magma continues to rise.

6. Plastic Deformation: Permanent Change Plastic Deformation: Permanent change in shape or size of a rock. Occurs when stress exceeds a rock's elastic limit. Rock layers bend or fold, but do not break. Common in areas with high temperatures and pressures. Contributes to the formation of geological structures like folds and domes.

7. Faults and Earthquakes Breaks in Earth's crust where rocks have slipped past each other Caused by tectonic plate movement and stress buildup Three main types: normal, reverse (thrust), and strike-slip Energy release during fault movement causes earthquakes Fault zones are areas with high earthquake activity

8. Reverse Faults: Compression and Uplift Reverse faults occur when rocks are compressed together. The hanging wall moves upward relative to the footwall. This movement is caused by compressional forces. They are often found at convergent plate boundaries. Can result in significant uplift and mountain building.

9. Normal Faults: Tension and Downward Slip Normal faults occur when rocks are pulled apart (tension). The hanging wall moves downward relative to the footwall. This movement is caused by tensional forces. They are often found at divergent plate boundaries. Can result in the formation of rift valleys and grabens.

10. Strike-Slip Faults: Horizontal Movement Strike-slip faults occur when rocks slide horizontally past each other. Movement is predominantly horizontal, parallel to the fault line. Caused by shear stress, where forces act in opposite directions. Often associated with transform plate boundaries. The San Andreas Fault is a famous example of a strike-slip fault. Can cause significant earthquakes and ground displacement.

11. Seismic Waves: Earth's Messengers Seismic Waves: Energy released by earthquakes travels in waves. Body Waves: Travel through Earth's interior. P Waves: Primary/compressional, fastest, travel through solids & liquids. S Waves: Secondary/shear, slower, travel through solids only. Surface Waves: Travel along Earth's surface, cause most damage. Love Waves: Side-to-side motion. Rayleigh Waves: Rolling motion.

12. Epicenters: Earthquakes Above Ground Epicenter: Point on Earth's surface directly above the earthquake's focus. Focus (Hypocenter): Point within the Earth where the earthquake originates. Seismic waves radiate outward from the focus. Epicenter experiences the strongest shaking. Location is determined using seismograph data. Plays a crucial role in understanding earthquake impacts.

13. Seismometers: Recording Earth's Tremors Seismometers are instruments that measure ground motion caused by seismic waves. They record the vibrations and convert them into electrical signals. These signals are then amplified and recorded on a seismogram. Seismograms provide valuable data about the earthquake's location, magnitude, and depth. Scientists use this information to study the Earth's interior and understand earthquake behavior.

14. Seismic Wave Propagation Seismic waves radiate outwards from the focus of an earthquake. Two main types: body waves and surface waves. Body waves (P and S) travel through the Earth's interior. Surface waves (Love and Rayleigh) travel along the Earth's surface. Surface waves cause the most damage.

15. Focus: Earthquake Origin Point The focus is also known as the hypocenter. It is the point within the Earth where an earthquake originates. Seismic waves radiate outward from the focus. Depth of focus influences the earthquake's impact. Shallow focus earthquakes (<70 km) cause more surface damage. Deep focus earthquakes (>300 km) are less damaging.

16. Measuring Earthquake Intensity Magnitude: Measures the energy released by an earthquake. Richter Scale: Most common magnitude scale, logarithmic. Each whole number increase represents a 10x increase in amplitude. Moment Magnitude Scale (MMS): More accurate for large earthquakes. Intensity: Measures the observed effects of an earthquake. Modified Mercalli Intensity Scale: Based on damage and human perception.

17. Measuring Earthquake Magnitude Richter Scale: Measures amplitude of seismic waves, outdated Moment Magnitude Scale (MMS): Measures energy released, more accurate Each whole number increase on these scales = 10x increase in wave amplitude/energy Magnitude indicates earthquake size, not necessarily damage Other scales exist for specific purposes (e.g., Mercalli Intensity Scale for perceived effects)

18. Earth's Interior: A Layered Sphere Earth's interior is divided into layers based on composition and physical properties. The crust is the outermost layer, thin and rigid. The mantle is the thickest layer, mostly solid but flows slowly. The outer core is liquid iron and nickel, responsible for Earth's magnetic field. The inner core is solid iron and nickel, extremely hot and dense.

19. Earthquake Hazards and Risks Ground Shaking: Can cause buildings and infrastructure to collapse. Tsunamis: Giant waves triggered by underwater earthquakes. Landslides: Ground instability can lead to landslides. Liquefaction: Soil loses strength and behaves like a liquid. Fires: Earthquakes can rupture gas lines and cause fires.

20. Earthquake Energy Release Earthquakes release energy as seismic waves, causing ground shaking. Energy originates from the focus, where rocks break under stress. Released energy travels as P-waves, S-waves, and surface waves. Surface waves cause the most damage due to their larger amplitude. Magnitude scales measure the amount of energy released.

21. Earthquake Mitigation Strategies Earthquake-resistant building design and construction Early warning systems to provide seconds of advance notice Community preparedness through drills and education Land-use planning to avoid high-risk areas Retrofitting existing buildings to improve their seismic resistance