nico-EARTHQUAKES-AND-TSUNAMIS

EARTHQUAKE AND TSUNAMIS Prepared by: Ms. Shelamie P. Coquilla

EARTHQUAKES

  • Definition: Trembling of the Earth’s surface.

  • Origin: Occurs when energy stored in the Earth as strain in rock layers is released.

CAUSES OF EARTHQUAKES

Stressful Forces in the Crust

  1. Tension Forces:

    • Stretch or pull rock layers from opposite directions.

  2. Compression Forces:

    • Push rock layers from opposite sides.

  3. Shearing Forces:

    • Pull rock layers in different directions.

EFFECTS OF STRESS

  • Rock layers may tilt, bend, or break.

  • Folding: Occurs when rocks crumple or wrinkle.

    • Example: Mountains formed by folding and shaping from volcanic materials.

FAULTS AND EARTHQUAKE TERMS

Definitions

  • Focus (Hypocenter): Point within the Earth where faulting begins.

  • Epicenter: Point on the Earth’s surface directly above the focus.

TYPES OF FOLDS

  1. Anticline: Rock layer bends upward.

  2. Syncline: Rock layer bends downward.

  3. Tight Fold: A sharp peaked anticline or syncline, compressed with greater force.

  4. Overfold: Folds become bent or warped and may overlap.

  5. Recumbent Fold: Compressed extensively; may take the form of an “s”.

FAULTING

  • Definition: Rock layer breaks due to excessive forces.

Types of Faults

  1. Normal Fault: Rocks move away from each other. The less stable tectonic plate drops below the more stable.

  2. Reverse Fault: Rocks are compressed; one plate moves up relative to the other.

  3. Tear Fault: Tectonic plates slide past each other causing severe earthquakes.

  4. Rift Valley: Formed when two normal faults occur parallel to each other, causing land to sink.

ELASTIC REBOUND THEORY

  • Rocks resist applied forces and eventually exceed their elastic limits, resulting in an earthquake.

  • Theory states that during an earthquake, rocks under strain suddenly break, causing vibrations or tremors as the fault slips, radiating seismic waves.

TYPES OF FAULTS (Continued)

Classification by Direction of Movement

  1. Normal Fault: One block moves down.

  2. Thrust or Reverse Fault: One block moves upward.

  3. Strike-slip Fault: Horizontal displacement movement.

  4. Oblique-slip Fault: Combination of strike-slip and normal fault movements.

LOCATING EARTHQUAKES

  • Seismic waves released by breaking rock layers.

Types of Seismic Waves

  1. Body Waves: Propagate through the earth’s interior (includes P-waves and S-waves).

    • P Waves (Primary waves): Fastest, move through solids, liquids, and gases.

    • S Waves (Secondary waves): Slower, only move through solids, causing shearing.

  2. Surface Waves: Propagate along the Earth's surface, causing extensive damage.

    • Love Waves: Move ground horizontally.

    • Rayleigh Waves: Move ground up-and-down and side-to-side.

MEASUREMENT OF EARTHQUAKES

1. Intensity

  • Based on damage to structures and effects on people.

  • Variability depending on distance to epicenter and ground conditions.

2. Magnitude

  • Energy released at the focus, measured using Richter scale.

RICHTER SCALE

  • 1-3: Not felt

  • 3-4: Often felt, no damage

  • 5: Felt widely, slight damage

  • 6: Damage to poorly constructed buildings

  • 7: Major earthquake, significant damage

  • 8: Great earthquake with extensive destruction

  • 9: Rare, catastrophic damage over large areas.

EFFECTS OF EARTHQUAKES

  • Vary based on local conditions, including:

    • Building collapse, Landslides, Fires, and Tsunamis.

TSUNAMIS

  • Generated when the seafloor deforms abruptly, displacing overlying water.

  • Series of waves caused by underwater disturbances; travel at high speeds.

  • Meaning: Japanese for "harbor wave" (tsu - harbor, nami - wave).

  • Can reach heights of over 100 ft upon reaching land.

  • Example: December 26, 2004, magnitude 9.3 earthquake caused massive tsunami in the Indian Ocean, affecting multiple countries and causing a high death toll.

PREDICTING EARTHQUAKES

  • No exact prediction capabilities yet; instruments to detect warning signs include:

  1. Seismometer: Measures shaking of earthquakes.

  2. Seismograph: Detects tremors; changes in seismic wave speed.

  3. Laser Range Finder: Measures movements across faults

  4. Tide Gauge: Monitors tides for changes.

  5. Geiger Counter: Monitors radon levels.

  6. GPS: Measures movements of faults.

PROTECTION FROM EARTHQUAKE DAMAGE

  • Building designs should incorporate more vertical columns and mechanisms for reducing lateral movements.

  • Site selection is critical; avoid soft ground and active fault zones.

  • Special designs for bridges and minimizing overhanging structures.

EARTHQUAKE SAFETY

What to Do During an Earthquake

  1. Indoors: Drop to the floor, take cover under sturdy furniture.

  2. Outside: Move to open areas away from structures.

  3. Driving: Slow down, remain in the vehicle, and avoid overhead structures.

  4. Coastal Areas: Move to higher ground in case of tsunamis.

What to Do After an Earthquake

  1. Check for injuries.

  2. Look for hazards like fires and broken utility lines.

  3. Clean up hazardous spills.

  4. Stay alert for tsunami warnings and expect aftershocks.

THANK YOU!