Seismic Waves

  1. Seismic Waves and Earth's Interior
    Seismic waves, released during earthquakes, help scientists locate the epicenter and understand the Earth's internal structure through their movement and behavior.

  2. Types of Seismic Waves
    Seismic waves are classified into four types:

Body Waves: P-waves and S-waves (travel through the Earth's interior).

Surface Waves: L-waves and R-waves (travel along the Earth's surface).

  1. Body Waves

P-Waves (Primary): Fastest, travel through solids, liquids, and gases; cause compression.

S-Waves (Secondary): Slower, move only through solids; cause perpendicular ground movement and major structural damage.

  1. Surface Waves

L-Waves (Love): Horizontal ground movement; cause severe damage.

R-Waves (Rayleigh): Rolling motion; slowest wave, dispersive, and affect large areas.

  1. Earthquake Detection and Measurement

Seismograph: Records seismic waves; produces seismograms.

Triangulation Method: Determines epicenter using three seismograph stations based on P- and S-wave arrival times.

  1. Direct Observations of Earth's Interior

Temperature & Pressure: Increase with depth (e.g., +3°C per 100 meters).

Rock Samples:

Xenoliths: From volcanic eruptions.

Ophiolites: Exposed by tectonic processes.

  1. Indirect Observations of Earth’s Interior

Seismic Waves: Refraction reveals rock composition.

Volcanic Activity: Provides materials for analysis.

Meteoric Fragments: Offer clues about Earth's internal composition.

  1. Determining Earth's Average Density
    Using Newton’s Law of Gravity, Earth's mass and volume were calculated, yielding an average density of 5.5g/cm35.5 g/cm^3, much denser than the crust ($$2.8 g/cm^