  Over 2000 years Aristotle: earthquake as subsurface wind  19 th century: scientific observation begins  Understanding: what, why, where, magnitude, frequency  Earthquakes (seisms): caused by rapid release of energyseisms  Caused by: volcanic activity, meteors, landslides, explosions  Also caused by: sudden movements along faults  Faults: Sharp lines in rock layers  Stresses in near-surface rocks, rocks fracture, shift along fault  Rock rupturing produce shock waves  Concentrated energy release, moves radially outward  Fault mapping: determine earthquake-hazard belts  Over 2000 years Aristotle: earthquake as subsurface wind  19 th century: scientific observation begins  Understanding: what, why, where, magnitude, frequency  Earthquakes (seisms): caused by rapid release of energyseisms  Caused by: volcanic activity, meteors, landslides, explosions  Also caused by: sudden movements along faults  Faults: Sharp lines in rock layers  Stresses in near-surface rocks, rocks fracture, shift along fault  Rock rupturing produce shock waves  Concentrated energy release, moves radially outward  Fault mapping: determine earthquake-hazard belts 1 4: Earthquake History Google Images, Faults Blue Anchor, Somerset, UK Understanding Earthquakes, (2:55) Hutton’s Unconformity, ScotlandUnconformity Hutton’s Unconformity, ScotlandUnconformity

  Plates move: mountains elevated, basins warped down  Lithospheric rocks fracture, i.e. jointing, cracking  Large stress: fault, tilting, folding  Dip-Slip Fault: vertical movement caused by pulling or pushing force  Normal fault – pull apart, sea floor spread centers  Reverse fault – compression, convergence, subduction, continental collisions  Strike-Slip: horizontal movement along fault  Ex. Queen Charlotte  Transform Fault: horizontal movement on boundary  Plate sides move past each other 2 Types of Faults Google Images, Queen Charlotte Fault Earthquakes of the Midwest, (12:53)

  Surface waves – complex motion, slowest velocity  Primary (P) waves – compressional motion, fastest  Secondary (S) waves – “shake” motion, slower than P waves  Travels through solids  Focus – inside earth where waves originate  Epicenter – point on surface above focus  Earthquake destruction determined by:  Intensity, duration, building material, structural design  Destruction results from:  Ground shaking, liquefaction, tsunami, landslides  Ground subsidence and fires 3 Earthquake Waves Reconstruction of a Cascadia Subduction, (14:33) Fig 8.16: Damage 1964 Anchorage, Alaska

  Def : fractures in rocks with displacement  Normal fault (fig): c aused by tensional forces  Hanging wall below fault surface, footwall above  Prevalent along spreading centers  Crust fractures into blocks  Ex. Basin and Range Province  Produced parallel mountain ranges  Due to movement along fractures 4 Fault Specifics

  Type of dip-slip fault  Hanging wall block moves up  Due to strong compressional forces  Accommodates crustal shortening 5 Reverse and Thrust Faults Mountains fault, (1:25) Google Images: Thrust Fault

  Transform fault: large strike-slip fault  Cuts through lithosphere  Occurs at boundary between plates 6 Transform Fault Google Images: San Andreas Fault San Andreas Fault, (3:03)