TOPIC 2 - CETS 461 - TERMS

EARTHQUAKE ENGINEERING

Epicenter

Geographic point on Earth’s surface directly above the focus

Focus/Hypocenter

Point where fault rupture begins (underground).

Fault Plane

Plane along which rock ruptures and slips.

Dip Angle

Angle between fault plane and horizontal surface.

Strike Angle

Direction of fault line relative to North.

Fault Slip

Relative displacement along the fault plane.

Epicentral Distance

Distance from epicenter to observation station.

Shallow

Focal depth of <70 km (most destructive)

Intermediate

Focal depth of 70–300 km

Deep

Focal depth of >300 km

Foreshocks

Smaller quakes before main shock.

Aftershocks

Smaller quakes after main shock due to stress adjustments

Fault Types

• Dip-Slip

• Strike-Slip

• Oblique-Slip

Dip-Slip

Vertical movement (normal/reverse faults).

Strike-Slip

Horizontal movement (e.g., transform faults).

Oblique-Slip

Combination of both Dip-Slip and Strike-Slip

Body Waves

• P-waves (Primary)

• S-waves (Secondary)

Surface Waves (most destructive)

• Love Waves

• Rayleigh Waves

P-waves (Primary)

• Longitudinal, fastest (∼6 km/s in solids).

• Travel through solids and liquids.

S-waves (Secondary)

• Transverse, slower (∼3 km/s).

• Travel only through solids.

Love Waves

Horizontal shearing motion.

Rayleigh Waves

Rolling motion (like ocean waves).

Peak Ground Acceleration (PGA)

Key parameter for design.

Attenuation

Dissipation of seismic energy with distance.