Lecture 3

22 views3 pages
Published on 30 Oct 2010
School
UTSC
Department
Environmental Science
Course
EESA06H3
Professor
Jan 23rd 2009
EESA06
What do earthquakes tell us about the planet's interior, and plate tectonics?
- how do we collect information about the earth's interior
o deep drilling
o russian hold record of 12Km deep
o at 12Km rocks are getting soft and will fill up the hole
earthquakes: what can we learn of the earth's interior?
- rocks are brittle, they will snap
- energy produced from the snap produces an earthquake
- epicenter: directly above the focus
- fault plane: line of breakage; smooth surface where rocks have slipped
- propagates the rocks as seismic waves
- fault trace: part of the fault showing on the surface; often buried (blind faults)
- fault plane: part of the fault showing underneath
New Zealand
- in between pacific plate and indo-australian plate
- a lot of fault scarps
Waves
- surface waves does most damage to buildings (e.g. love wave and rayleigh wave)
- primary waves(compressional waves): 5-7km/sec; arrive first, faster
- secondary waves: 2-4 km/sec; last type of wave to arrive, smaller
- there will be a gap in time between the arrivals of the primary and secondary waves
o separation of the arrival times can be used to find the epicentre
o if on the epicenter, both waves will arrive simultaneously
p-waves
- compressional waves
- p-waves that pass through the core are refracted
- area that does not receive direct p-waves is call the p-wave shadow zone
- p-waves spread directly around the epicenter for 103degrees latitude
s-waves
- core doesn't transmit s-waves; cannot travel through liquids
- spreads directly to 103degrees latitude around epicenter
- s-wave shadow zone very large
Seismic tomography
- image of the earth's interior in slices
- there are major physical properties (temperature, pressure) changes that affect the waves
- MOR spreading centers are underlaying by very hot rocks (plumes)
o plumes feed the MORs (convection)
o core->mantle->lithospheric plates(lithosphere: hard crust of the earth)
o some subducting plates cannot penetrate the boundary between lithosphere and
mantle
o if the plate bursts through the mantle, its descends into the mantle (downgoing slab)
and return to the top as plume (mantle overturning)
o this is a model for the earth's cooling system
A computer model of the earth's interior
- the core is hard
- the liquid on the outside is in the shape of plumes
www.notesolution.com
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Document Summary

Propagates the rocks as seismic waves fault trace: part of the fault showing on the surface; often buried (blind faults) fault plane: part of the fault showing underneath. Waves in between pacific plate and indo-australian plate a lot of fault scarps surface waves does most damage to buildings (e. g. love wave and rayleigh wave) P-waves that pass through the core are refracted. Seismic tomography image of the earth"s interior in slices there are major physical properties (temperature, pressure) changes that affect the waves. A computer model of the earth"s interior the core is hard the liquid on the outside is in the shape of plumes www. notesolution. com. Descending slab: slab-pull pulls the rock into the earth and slab-rollback moves it at an angle trench suction: rotation of the mantle rates: 2-25cm/year. Lithospheric plate crust + asthenosphere (weak rock of the upper mantle) continental crust is thicker (<70km thick) Oceanic crust is much thinner (5-8km thick)