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Since P-waves travel faster than S-waves, the greater the difference between the arrival time of the P and S-waves, the further a seismometer is away from the epicenter Triangulation of the epicenter:data from 3 or more seismometers are required to pinpoint the location of the epicenter Tsunamis:waves generated by the vertical movement of the seafloor Mercalli intensity scale:describes extent of damage to structures and the degree to which ground motion are felt following an earthquake -Destructiveness (perceptions of the extent of damage) - 12-point scale 80% of earthquakes are recorded in the Circum-Pacific beltand most originate at depths that rarely exceed 100 km. Deep-focus earthquakes: because some earthquake foci can be as deep as 670 km, it must be concluded that the descending lithosphere can retain at least some brittle properties to that depth. -No earthquakes originate at depths below 670 km Intraplate earthquakes:relatively shallow foci and the majority occur on continents -5% of earthquakes are not near modern plate boundaries Seismologists base long-term predictions on identification of seismic zones and the recurrence intervalSeismic waves can be reflected or refracted when they enter new mediums of different densities-Because they are reflected and refracted at the core-mantle boundary (CMB), none of the P-waves emerge at the surface between 103 and 143 degrees from the epicenter -The CMB casts an even more pronounced shadow for the S-waves, between 103 and 180 degrees, from the epicenter Orogenesis: mountain building With the exception of the large volcanoes formed over hot spots, mountains do not occur in isolation, but as part of linear ranges called mountain belts or orogens. Sedimentary rocks are originally deposited in horizontal layers (typically no folds or bends) Deformationchanges the character of the rocks and is easy to see -Undeformed rocks, like sedimentary rocks, display horizontal beds, with no folds or faults -Deformed rocks showtilted beds,metamorphic alteration,folding andfaulting-Stress:force applied per unit of surface area -Strain:change in shape or volume
-Strain is proportional to stress Elastic deformation:non-permanent deformation of a solid when it is stretched, bent, or squeezed and the force is then removed -Occurs when stress is applied slowly under low pressure Ductile/plastic deformation:a solid exhibiting ductile deformation behaves elastically under low stress, but, beyond a certain point, elastic properties cease and ductile flow occurs Brittle deformation and fracture:when the limits of elastic deformation are exceeded, a solid may fracture Fractures, like ductile deformation, produce permanent and irreversible deformation. Large scale fractures in rocks are called jointsof faults. Joints:a crack along which there is little or no movement The behavior of a rock depends on: -Temperature: the higher the temperature, the weaker and less brittle a solid becomes -Confining pressure:an increase in confining pressure inhibits the formation of fractures -