earthquakes pg 123. seismometer- an instrument that measures earthquakes earthquake- is a series...
TRANSCRIPT
Chapter 6
Earthquakes pg 123
Seismometer- an instrument that measures
earthquakes Earthquake- is a series of low frequency shock
waves traveling through earth Tectonic plate motion builds up stress at plate
boundaries and within the plates themselves. Stress- is a force exerted inside a material. Shear- exits when forces are acting in opposite
directions on different parts of the same object.
Tectonic Forces
Divergent boundaries- Plate sections that are
moving part. Convergent boundaries- plates moving
towards each other. Transform boundaries- where plates slide past
each other.
Strain- any change in shape of a solid under
stress. Ductility- the amount of strain a material can
endure without breaking Some Rocks have elasticity. These rocks store
energy which can cause a more serious earthquake.
Strain and fracture
Joints- cracks in rocks Faults- occurs when the sections of rock on
opposite sides of the crack move relative to each other
Most major fault lines in the United States are in mountain Ranges.
Dip slip fault- parallel to its dip Normal fault- block above fault surfaces drops. Reverse fault- upper block rises above lower
block
Section 6b Faults and Joints
Most earthquakes we feel happen at depths
less than 45 miles. Secondary earthquakes are called aftershocks. Aftershocks result from potential energy still
being stored in the rocks. The fault slips again which causes the after shock.
Aftershocks can go one for days, weeks or even months after the initial earthquake.
Faults and earthquakes
Seismometer are instruments that detect
seismic waves (earthquake waves). Seismographs include a seismometer and a way
to record the wave changes During normal activity the seismograph will
draw a straight line. During a earthquake the straight line turns into a zigzag. The height (amplitude) of the zigzag (wave) shows how strong the earthquake was.
The bigger the amplitude the stronger the earthquake
6c Earth waves and Seismology
Body waves- earthquake waves that pass right through the
earth. P waves- Fastest body waves. Have small amplitude and short
wavelengths. They can travel through both solid and liquid rock S waves- have larger amplitude. Stronger and slower than P
waves. They can travel through solid rock. Surface waves- travel through earths surface. Have to basic
waves Rayleigh and Love waves. Rayleigh and Love waves are more destructive waves because
they affect human structures. ( house buildings, roads, etc.)
Epicenter – Center; spot on earths surface directly Focus- the center of an earthquakes activity . This is deep
underground
Type of Seismic Waves
Richter scale- how the strengths of earthquakes are reported. Magnitude- indicates the energy released by the earth movement. This scale does not work well on earthquakes that have a magnitude over 7.
Effects of Earthquakes
Intensity- is a measure of how much damage
actually results from the earthquake. Earthquakes can last from a few seconds to a
few minutes. Modified Mercalli Intensity scale- Measures
the destructiveness of an earthquake. The scale is 1- 12.
1 is a earthquake that leaves no visible damage. A 12 is total destruction to the whole building.
Earthquake Intensity
Building collapse, fire, tsunamis, and landsides
are all hazards of earthquakes. Many cities are enforce earthquake proof
buildings and strict building codes. Many cities have sensors in their gas lines.
These sensor will turn the gas off if there is a break in the line.
Earthquake Hazards