Earth's Surface Cracks and Faults

Study Notes

Earth's Surface Cracks

Earthquakes: Sudden releases of energy in Earth's crust cause shaking and trembling.
Faults: Fractures or breaks in Earth's crust.
Fault zones: Series of associated faults.
Stress: Force applied to rocks.
Types of Stress:
- Tensional stress: Rocks stretched apart.
- Compressional stress: Rocks pushed together.
- Shear stress: Rocks pushed perpendicular to the axis.

Faults and Movements

Dip: Angle of a fault plane.
Dip-slip faults: Faults formed by the dip, including normal and reverse faults.
Hanging wall: Part of the fault above the fault plane.
Footwall: Part of the fault below the fault plane.
Normal Fault: Hanging wall moves down relative to the footwall due to tensional stress.
Reverse Fault: Hanging wall moves up relative to the footwall due to compressional stress.
- Thrust fault: Subtype of reverse fault with a dip less than 45°.
Strike-slip fault: Fault movement along the strike (horizontal).
- Shear: Parallel but opposite movements along the fault plane.
  - Left-lateral strike-slip fault: Leftward movement of one side relative to the other.
  - Right-lateral strike-slip fault: Rightward movement of one side relative to the other.
Oblique-slip fault: Movement along both dip and strike directions, combining shearing and compression/tension.

Active and Inactive Faults

Active faults: Generated earthquakes within the last 10,000 years and may continue to do so.
- Shallow earthquakes occur on active faults.
Inactive faults: No record of generating earthquakes in the last 10,000 years, but may generate earthquakes in the future.
Creep fault: Fault movement without associated earthquake activity.
Trenches: Long, narrow, and steep-sided depressions in the ocean floor.
- Philippine Trench: Deepest trench in the Philippines, third deepest globally.
Philippine Fault Zone (PFZ): Major tectonic feature crossing the Philippines (northwestern Luzon to southeastern Mindanao), 1200 km long, composed of many faults.
- Central Mindoro Fault: Right-lateral fault marking a slope break.
- Lubang Fault: Left-lateral fault offshore between Batangas and Mindoro.

Anatomy of an Earthquake

Focus/Hypocenter: Point where rocks first break, releasing seismic energy.
Fault plane: Breaking surface underground.
Fault line: Edge of the fault plane.
Fault scarp: Exposed fault plane above the ground, indicating a fault.
Epicenter: Point on Earth's surface directly above the focus; the strongest earthquake point.
Types of Earthquake According to Depth of Focus: (related information omitted in the text).

All About Tsunamis

Tsunami: Large volume of water reaching the surface, triggered by underwater events.
Causes of Tsunamis:
- Underwater earthquakes.
- Volcanic eruptions.
- Nuclear explosions.
- Meteors.
- Underwater landslides.
Strong Tsunamis:
- Tohoku, Sendai (Japan) - March 11, 2011: 9.0 magnitude.
- Southern Chile - May 22, 1960: Strongest earthquake, 9.5 magnitude.
- Northwest Sumatra (Indonesia) - December 26, 2004: 9.3 magnitude underwater earthquake.

Description

Explore the dynamics of Earth's surface with a focus on earthquakes, faults, and the various types of stress that act on rocks. This quiz covers essential concepts like dip-slip faults, normal and reverse faults, and the characteristics of stress. Test your understanding of geological processes and fault mechanics.