Stresses Due ToSeismic WavesSeismic waves are waves of energy that travelthrough the Earths layers, and are a result ofan earthquake, explosion, or a volcano thatimparts low-frequency acoustic energy.
Types Of Seismic Waves Body Waves :Primary Waves and Secondary Waves. Surface Waves :Love Waves and Rayleigh Waves.
Body WavesBody Waves travel through the Interior of earth.They follow the ray paths refracted by thevarying density and modulus (Stiffness) of theearth interior.This effect is similar to the refraction of lightwaves.
Types of Body WavesThese are the fastest moving waves. There aretwo types of Body Waves. P (primary) Waves or Compressional Waves. S (secondary) waves or Shear Waves.
P (primary) WavesA longitudinal earthquake wave that travelsthrough the interior of the earth and is usuallythe first conspicuous wave to be recorded by aseismograph.
S (secondary) wavesA transverse earthquake wave that travelsthrough the interior of the earth and isusually the second conspicuous wave toreach a seismograph.
Surface WavesSurface waves are analogous to water waves andtravel along the earth’s surface.They Travel Slower then Body Waves because ofthere low frequency, long duration, and largeamplitude.They can be the most destructive type ofSeismic Waves.
Types of Surface wavesThere are two main types of surface wavesRayleigh WavesLove Waves
Impact Of Seismic WavesSeismicwaves result fromslip and rupture(breakage) ofrocks and plates ofearth along faults.
Earthquakes occur with the passage of largeseismic waves. In other words we can say that there is asequence of seismic waves following each other.
There is a Question raised that,How can we reduce the effectand destructions of Seismic waves…..?
Resistant TechniquesEarthquake may not be able to damage entirebuilding but it damage members of it.So special techniques are adopted :Base Isolation DevicesandSeismic Dampers
Base Isolation Devices
Resistant StructureRectangles aresuch structure ofbuilding on whichthe Seismic wavesare less effective.
Arches and TrianglesArches and triangles are also suchstructures of building on which theSeismic waves are less effective or noteffect just like other buildings.
PrecautionaryMeasurementsWe need different levels of resistance fordifferent classes of structures.Critical structures such as hospitals, powerplants, water-treatment, and chemical plants,dams, etc.
These buildings must not only survive theshaking, but must remain in operation.These structure require the largestinvestment of resources to insure thatthey can provide services following anearthquake.