Earthquakes 3: Seismology, earthquake magnitude/intensity

Hypocenter vs epicenter

Hypocenter is where the earthquake is on the plate, epicenter is the the closest point on the surface.

Body waves vs surface waves

Body waves travel inside materials (in the earth

Survive waves travel along boundaries between materials

P wave

Body wave

Particles move same direction as waves traveling

Compression and extension of solid/fluid

Fastest seismic wave (6km per second)

S wave

body wave

Particles move perpendicular to direction of wave propagation

Shearing distortion of solid

Slower than p wave (3.5km /sec)

Which wave can’t pass through fluids?

S waves!

Surface waves (Rayleigh wave)

Requires interface ( ground-air, water-air)

Slower than body waves

Particles move similar to ocean

Surface wave (Love wave)

Horizontal movement perpendicular to waves travel directi

What does p-s lag time tell us?

Distance from earthquake to seismograph

3 seismograph location

Tell us the epicenter

Magnitude

How much energy was released

Intensity

How strong ground motion is at specific location

Soil and EQ intensity

Bedrock low amplification

Well compacted sediment: moderate amplification

Water saturated sediment; high amplification

Earthquake intensity depends on

Structural resistance

Durations

Elastic Rebound

how faults store and release energy

earthquakes are caused the faults cause elastic deformation—> brittle failiure,

plates locked =

stress and deformation

plates release =

earthquake and tsunami