Earthquakes - Lec 11

Types of Earthquakes

Tectonic
Volcanic
Explosive
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Seismic Waves

Vital information about the internal structure of the Earth

Seismic Waves

• Body Waves (P-waves and S-waves)
• Surface Waves (Rayleigh waves and Love waves)

Body Wave

• Travel through the interior of the Earth

P-waves (Primary or Push-Pull or Pressure)

Longitudinal Waves / Compressional Waves
• Has greatest speed and appears first on seismograms
• Rigidity (↑ Rigidity, faster P-waves)
• Compressibility (↑ Compressibility, faster P-waves)
• Density (↑ Density, slower P-waves)

S-waves (Secondary or Shear or Shake)

Transverse Waves
• less speed than P – waves
• Rigidity (↑ Rigidity, faster S-waves)
• Density ↑ Density, slower S-waves)

Surface Wave

Along the surface of the Earth and the layers near the surface

Rayleigh waves

• Lord Rayleigh
• Combined effect of P- and S-waves on the earth’s surface
• Ground Roll / Rolling Waves

Love waves (L – Waves)

• Augustus Love
• Shearing sideways and then returning to its original form as each wave passes.

Seismic Velocity

Physical Deformation

• Seismic Wave
  • Speed
  • Direction
  • Location

Elastic Moduli

Viscoelastic microplastic behavior of rocks

Elastic Constant

Stress and Strains

Static Method

Deformation induced in a material by the application of a force

Dynamic method

Measuring the ultrasonic body wave velocities

Grouting

• Injection of appropriate materials under pressure into certain parts of the earth's crust
• Sealing of cracks in manmade structures

Compaction Grouting

• Increase the density of the soil
• Rehabilitate settlement of sensitive structures