Metamorphism and Earthquake Processes

Metamorphism

Process of rock transformation due to heat and pressure.

Metamorphic rock

Rock formed from existing rock through metamorphism.

Earthquake

Sudden release of energy in Earth's crust.

Impact craters

Depressions formed by meteorite impacts.

Shock metamorphism

Metamorphism caused by high-pressure shock waves.

Deformation

Change in shape due to applied forces.

Stress

Force applied to rocks causing deformation.

Strain

Physical change resulting from stress on rocks.

Elastic deformation

Reversible change; rock returns to original shape.

Brittle deformation

Fracture occurs under stress; non-reversible.

Ductile deformation

Irreversible change; rock does not return to shape.

Folds

Bends in rock layers from ductile deformation.

Faults

Fractures in rocks where displacement occurs.

Joints

Fractures without significant displacement.

Normal fault

Occurs under tensional stress; rock stretches.

Reverse fault

Occurs under compressional stress; rock shortens.

Strike-slip fault

Lateral movement along the fault plane.

Dip-slip fault

Movement along the dip of the fault.

Oblique-slip fault

Combination of dip-slip and strike-slip movements.

Elastic rebound theory

Energy release during rock breakage causes earthquakes.

Focus (hypocenter)

Point within Earth where seismic waves originate.

Epicenter

Point on surface directly above earthquake focus.

Seismic waves

Energy waves released during an earthquake.

Body waves

Seismic waves traveling through Earth's interior.

P wave

Fastest seismic wave; compressional motion.

S wave

Slower seismic wave; transverse motion.

P waves

Primary waves that travel through solids and fluids.

S waves

Secondary waves that only travel through solids.

Surface waves

Slowest seismic waves causing most damage.

Love waves

Side-to-side motion with no vertical displacement.

Rayleigh waves

Rolling motion causing significant ground movement.

Seismometer

Internal component of a seismograph recording ground motion.

Seismograph

Instrument for recording earthquake ground motion.

P-S interval

Time difference between P and S wave arrivals.

Travel-time curve

Graph plotting seismic wave arrival time versus distance.

Moment Magnitude (MW)

Magnitude scale based on seismic moment measurements.

Seismic moment

Force needed to generate recorded seismic waves.

Tectonic earthquakes

Earthquakes caused by tectonic plate movements.

Volcanism

Earthquakes resulting from volcanic activity.

Artificial induction

Earthquakes caused by human activities or interventions.

Reservoir induction

Seismicity increase after water impounding behind dams.

Divergent boundaries

Plates move apart, creating new lithosphere.

Convergent boundaries

Plates collide, leading to mountain formation.

Transform-fault boundaries

Plates slide past each other horizontally.

Normal faults

Faults where one side slips down.

Thrust faults

Faults where one plate is pushed over another.

Reverse faults

Similar to thrust faults, but steeper.

East African Rift

Example of continental plate separation.

Ocean-ocean convergence

Forms oceanic trench and volcanic island arcs.

Ocean-continent convergence

Creates volcanic mountain chains and deep earthquakes.

Continent-continent convergence

Results in crustal thickening and folded mountains.

Subduction zone

Where one plate moves under another, causing earthquakes.

Nazca Plate

Oceanic plate subducting under South American Plate.

Peru-Chile Trench

Trench formed by Nazca Plate subduction.

Megathrust earthquakes

Largest earthquakes at convergent boundaries.

Wadati-Benioff Zone

Seismicity zone along subducting plate's plane.

Depth of focus

Distance between earthquake focus and epicenter.

Shallow focus earthquakes

0-70 km deep, 85% of occurrences.

Intermediate focus earthquakes

70-350 km deep, 12% of occurrences.

Deep focus earthquakes

350-670 km deep, 3% of occurrences.

Ductile manner

Deep rocks flow under stress, limiting energy release.

Transform boundaries

Plates slide past each other horizontally.

Strike-slip fault

Fault where plates move laterally against each other.

San Andreas Fault

Major transform fault in California.

Secondary hazards

Additional risks caused by primary earthquake hazards.

Liquefaction

Soil behaves like liquid during shaking.

Tsunamis

Waves caused by underwater earthquakes or landslides.

Ring of Fire

Area with high earthquake and tsunami risk.

Cascadia Subduction Zone

Location of potential megathrust earthquakes in Canada.

Creepmeters

Devices measuring fault movement over time.

Tiltmeters

Instruments monitoring land slope changes.