Chapter I 6

Earthquakes

def. : vibration of the Earth caused by the sudden release of energy

Elastic: Rebound Theory

storage of energy, until rock 'snaps back' to its original undeformed shape

Seismology

-the study of earthquakes

-seismograph: instrument to record earthquakes

-seismogram: record made by a seismogragh

-focus: location within crust where rupture occurs (shallow f: <10 km,

intermediate f: 70-300 km, deep f: >300 km)

-epicenter: location on Earth surface vertically above focus

Earthquakes and Plate Margins

-subduction zones

-Benioff zone

Seismic Waves

-body waves: travel within the Earth (like sound waves)

-p-wave: compression-expansion wave, travels fastest, travels through everything

-s-wave: shear wave, travels slower, travels not through liquids

-surface waves: travel along ground surface (like ocean waves)

-Rayleigh-wave: slowest wave, like water waves

-Love-wave: material moves back and forth in a horizontal plane, perpendicular to the direction of wave travel

Locating an Earthquake

-triangulation

-time-travel curves

Measuring Earthquake Intensity and Magnitude

-Intensity (according to Mercalli): a qualitative assessment of the kinds of damage done by earthquake

-Magnitude (according to Richter): a quantitative measurement of the amount of energy released by earthquake, expressed on a logarithmic scale, and therefore an increase of mag. 5 to mag.6 earthquake means a l0-fold increase in amplitude of the largest seismic wave

Destructive Effects of Earthquakes

-ground shaking

-liquefaction

-fire

-tsunami

-ground failure

-land slides

-avalanches

-rock slides