Earthquakes Flashcards
P wave
Primary wave. Fastest waves. Start from focus. Move through solids and liquids.
Seismic wave
The energy released by an earthquake
S waves
Secondary wave. Second fastest. Moves through solids only. Start from focus.
Surface waves.
Slowest wave. Most destructive. Start from epicenter. Travel olmly at surface.
Focus
The underground origin of the earthquake. P and S waves start here.
Epicenter
The spot on the surface of the ground where the shaking is worst. Above focus. Surface waves start here.
Plate boundaries
Most earthquakes occur along plate boundaries.
Identify the fault, focus and the epicenter in a picture
Fault = the break in the rock
Focus = the first slippage of the rock
Epicenter = point on the surface above the focus
Fault
Any break in the crust
Amplitude
The height of a seismic wave.
Tells geologists how powerful an earthquake is.
S-P Lag Time
The difference from the start of the P wave to the start of the S wave.
Can be used to tell how far away an earthquake is.
Which seismic station was closer to the earthquake, Tokyo or Sydne?
Tokyo, because the lag time is smaller and the amplitude is larger.
Which city was closest to the earthquake?
Montreal, because the lag time is the smallest.
Liquefaction
The mixing of soil and groundwater duing an earthquake. Can lead to buildings sinking into the soil.
Ground dispalcement
movment of the crust along a fault
What is the lag time of this seismogram?
About 14 seconds. P wave arrives at 10 seconds and S wave arrives at 24 seconds.
What is the amplitutde for this seismogram?
About 18 mm.
