JNTU B.Tech III ELEMENTS OF EARTHQUAKE ENGINEERING Previous Question Paper (August - 2022 - R18)

Earthquake effects are categorized into direct and indirect impacts based on their immediate causal relationship with ground motion.

Direct Effects: These result immediately from the ground shaking and fault rupture. They include ground shaking, which causes structural damage or collapse of buildings, bridges, and dams; surface faulting, where the ground surface is permanently displaced along a fault line; and ground failure, such as liquefaction, lateral spreading, or landslides triggered directly by seismic energy.

Indirect Effects: These are secondary consequences triggered by the direct effects. Key examples include tsunamis, which are large sea waves generated by underwater earthquakes; fires, often caused by ruptured gas lines or electrical short circuits; flooding due to dam failures; and socio-economic disruption, including loss of life, homelessness, destruction of infrastructure, and long-term economic instability.

Seismic waves are classified into two main categories: Body waves and Surface waves.

1. Body Waves: These travel through the interior of the Earth.

• Primary (P) Waves: Also called compressional or longitudinal waves. They involve particle motion in the same direction as the wave propagation. They are the fastest and travel through solids, liquids, and gases.
• Secondary (S) Waves: Also called shear or transverse waves. Particle motion is perpendicular to the direction of wave travel. They travel only through solids and are slower than P-waves.

2. Surface Waves: These travel along the Earth's surface and are responsible for most damage.

• Love Waves: These cause horizontal shifting of the ground perpendicular to the direction of wave movement. They are faster than Rayleigh waves.
• Rayleigh Waves: These produce an elliptical, rolling motion of the ground surface, similar to ocean waves.

Sketch description: Imagine P-waves as a series of compressions and rarefactions (slinky motion), S-waves as a rope being shaken up and down, Love waves as a snake-like side-to-side surface movement, and Rayleigh waves as a circular rolling motion of surface particles.