Geology - Tectonic Plates

Earthquake

event in which the ground shakes due to a release of built up energy.

Fault

where tectonic plates move against each other, earthquakes tend to occur

Seismic Waves

when tectonic plate moves → energy is transmitted in all directions

Focus

location within the Earth where energy is released, source of seismic waves

Epicenter

surface directly above an earthquake focus

Body Waves

moves through the inside of the Earth (IN THE EARTH)

2 Types of Seismic Waves

Primary (P) waves, Secondary (S) waves

P-waves

longitudinal waves (parallel to the direction the waves travels), the fastest, arrives first, and travels through solids and liquids

S-waves

transverse waves (perpendicular to the direction the wave travels), the slower and arrives the second, travels only through solids

Surface Waves

waves that move across the surface of the earth (ON THE EARTH) / below or along the surface, much slower and not as far as body waves.

2 Types of Surface Waves

Love (L) waves, Raleigh (R) waves.

L-waves

side to side motion

R-waves

rolling waves

Seismometer

instrument that detects and records seismic waves (seismograph)

Order of Waves

P-waves arrives first, S-waves second, then L & R waves

Difference in arrival times

can be used to calculate the distance of the seismograph to the epicenter

Triangulation

3 seismograph stations are needed to locate the epicenter, radius is equals to the epicenter, and the intersection of the circles locates the epicenter

Amplitude

wave is the maximum displacement that occurs during the vibration which is used to calculate the earthquake’s magnitude (ground movement)

Pointing Epicenter and Magnitude

1. Calculate the S-P interval in all three seismographs = seconds / distance

2. Determine Time/Distance intervals = radius

3. Draw a circle with the given radius around the seismographs and where all the seismograph intersect = location of the epicenter

4. Largest S-wave height = amplitude

5. Plotting the distance (S-P) on one axis and amplitude on another, where the line intersects on the richter scale = magnitude of an earthquake.

Richter Scale

used to determine the magnitude of an earthquake, measurement of maximum amplitude at the epicenter

Base-ten logarithmic scale

each whole-number increase = increase of tenfold in ground motion of the epicenter

Earthquake Predictors

foreshocks, changes in magnetic fields, changes in groundwater levels and patterns in past earthquakes.

Lithosphere

outermost layer of rock and the upper layer of the mantle

Crust

outermost layer of rock, oceanic + continental plates, thinnest layer, made of tectonic plates

Asthenosphere

upper layer of the mantle, fluid portion of mantle, and where convection currents happens

Mesosphere

more rigid part of the mantle beneath the asthenosphere

Outer Core

composed of liquid alloy of iron, nickel, cobalt

Inner Core

solid ball of iron, nickel, and cobalt

Deeper in the Earth

increase in both density and temperature