SEISMIC WAVES

SEISMIC WAVES

            Earthquakes produce vibrations called seismic waves, moving from the focus outward in all directions. Just like sound waves, these waves get weaker as they move away from the focus. This means, the farther you go from the hypocenter, the weaker the earthquake becomes.

TWO KINDS OF SEISMIC WAVES:

1.      BODY WAVES= very fast seismic waves moving through or inside the earth. These cause the most damage.

TWO TYPES OF BODY WAVES:

A.     Primary ( P ) or compressional waves = push and pull of the rocks in the earth. These can pass through solids, liquids and gases. They cause buildings to expand and contract ( compress). They move faster than shear waves.

B.      Secondary ( S) or Shear waves = move the rocks from side to side. They can only pass through solids. They cause buildings to shake.

2.      SURFACE WAVES = very slow, long waves moving along the earth’s surface, causing rocking movements that cause little damage to structures.

Two types of surface waves:

A.     Love waves = horizontally move along the surface, causing a side-to-side movement. This was named after Augustus E. H. Love, a British physicist who discovered it in 1911.

B.       Rayleigh waves = causes the surface to roll like the wave of the ocean, named after Lord Rayleigh, who discovered it in 1885.

Table 1.  Main types of seismic waves.
wave type	particle motion	name
body waves	longitudinal	P wave
	transverse	S wave
surface waves	horizontal transverse	Love wave
	vertical elliptical	Rayleigh wave

Animated seismic waves =  p & s waves

http://neic.usgs.gov/neis/eq_depot/2002/eq_021103/ak_seismic_waves.html

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm

love and Rayleigh waves

http://seismo.berkeley.edu/blogs/seismoblog.php/2009/07/27/title-5

http://www.geo.mtu.edu/UPSeis/waves.html

seismic waves http://www-rohan.sdsu.edu/~rmellors/lab8/l8maineq.htm