K is used for a core traversing wave such as pkp

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‘K’ is used for a core traversing wave such as PKP. Because there is a very large velocity decrease across the core-mantle boundary, Snell’s Law predict the waves will refract ‘towards the normal’. This refraction creates a ‘ shadow zone ’ for both the P- and S-waves at epicentral distances >97°.
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More seismic phases and raypaths
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Travel times of P-waves for ∆ = 0-180 Note that the rays that take off at the source dive progressively deeper into the mantle before reaching their turning depths after which the ray comes back up. For the core-traversing P-wave, there are 2-3 P-wave arrivals due to the strong refraction effects of the low velocity outer core and the high velocity inner core.
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Most all the seismic phases for planet earth
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North-ridge, California earthquake recording by global seismic network stations
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The four effects that make a seismogram: earthquake source, propagation, site response, and instrument
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Earthquake in Nevada (Feb. 2008) recorded by vertical component of many seismometers. Can you identify the P-wave, the Love and Rayleigh waves and measure their velocities ?
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Low velocity zone: a region just under the lithosphere often thought to be the weak asthenosphere where plate shear accululates Lithosphere A combination of increasing temperature and pressure affect the rock modulus to make a LVZ. The LVZ generally extends to NO deeper than about 200 km depth.
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Shear velocity North America from surface wave measurement inversion
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Tomography: make whole earth 3-d images of velocity structure from millions of P and S-wave travel-time measurements! Note high velocity (blue) slab image under north Turkey going into lower mantle
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Blue is seismically fast and red is seismiclly slow material. Note the slab image in lower mantle under SE coast of North America in both the P and S-wave images.
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Mean vertical average crustal shear velocity Shear velocity (m/s) Note oceans have mean velocity of 3.3 km/s and continents a mean velocity of 3.4-3.9 km sec. Passive margin/delta sediments at3.0 km/s. At right is error map which is always important to understand. If errors are big, results will be no good.
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Mean Moho depth from surface wave measurement ‘inversions’ Note 8-12 km beneath oceans and 28-80 km beneath continents. What causes this crustal thickness difference between oceans and continents?
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Crustal thickness from surface wave seismic measurement inversion note oceans at 10 km and continents at >35 km
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