PHYS2403 Geophysics Simulation Lab

Experiment 3: Seismic Wave Propagation & Seismogram

Earthquakes generate body waves (compressional P-waves, shear S-waves) and surface waves (Rayleigh, Love). These propagate through Earth's layers at velocities determined by rock elasticity. Use this interactive model to observe wave movements, particle oscillations, and how a seismograph records them.

Wave Controls

P-wave velocity (v_P)6.0 km/s

S-wave velocity (v_S)3.5 km/s

Source Frequency (f)1.5 Hz

Active Wave Type

Wavefront Propagation & Particle Motiont = 0.00 s

Synthetic Seismogram

Plots vertical ground motion recorded at the receiver. Markings indicate theoretical arrival times.

P arrival:13.33 s

S arrival:22.86 s

S−P gap:9.52 s

Seismic Wave Mechanics

P-Waves (Primary)

Longitudinal/compressional waves. Ground particles oscillate parallel to wave travel direction. P-waves are the fastest and travel through solids and liquids.

v_P = \sqrt{\frac{K + \frac{4}{3}\mu}{\rho}}

S-Waves (Secondary)

Transverse/shear waves. Ground particles oscillate perpendicular to travel. S-waves can only travel through solids, as liquids lack shear strength ( $\mu = 0$ ).

v_S = \sqrt{\frac{\mu}{\rho}}

Rayleigh Waves

Surface waves causing retrograde elliptical motion (ground rolls up and back). Velocities are slower ( $v_R \approx 0.92 v_S$ ) but amplitudes decay slowly, causing high damage.

Love Waves

Surface waves causing horizontal, transverse shearing of the ground. Velocities are slightly faster than Rayleigh waves ( $v_L \approx 1.05 v_S$ ).