earthquakes natural vibrations of earth’s ground caused by: - movement along tectonic plates -or...
TRANSCRIPT
Earthquakes Natural vibrations of Earth’s ground caused by:
- Movement along tectonic plates
-OR
-Volcanic eruptions
Forces Within Earth
Fracture caused when:
-the forces acting on the Earth’s Crust exceed the strength of the Crust and Rocks
The Deformation of material caused by:
-Stress
In the Forms of:
- Compression
- Tension
- Shear
• Earthquakes occur at the boundaries of tectonic plates.
• See a lot of EQ’s in places like Japan and California.
• FACT: 3 million earthquakes happen every year!
Faults• A fault is the fracture or system of fractures along
which movement occurs.
• The surface along which the movement takes places is called the fault plane.
Types of Faults
Types of Faults
• Reverse faults are fractures that form as
a result of horizontal compression.
• Normal faults are fractures caused by horizontal tension.
• Strike-slip faults are fractures caused by horizontal shear.
• When rocks break during an earthquake energy is released in the form of seismic waves.• These waves travel in all directions.
• Focus is the exact point within the earth where the rock first breaks.
• Epicenter is the point on the surface immediately above the focus.
Waves spread out as a wave travels.
3 types of waves associated with an EQ
p-wave
s-wave
surface wave
P-WAVE• primary wave
• longitudinal type wave
• fastest wave: 6 km/sec
Longitudinal
S-WAVE
• secondary wave
• transverse wave• ½ speed of a p-wave: 3 km/sec
• they do not travel through liquids
Transverse
Transverse Waves
• A wave that causes the particles of the medium to vibrate perpendicularly to the direction the wave travels.
SURFACE WAVE
• they travel along earths surface
• it’s the wave you “feel” during an earthquake
• up/down and back/forth motion
• slowest of all 3 waves
Surface Waves
• Occurs in a liquid
• Circular particle motion
Surface Waves
• Occur at the boundary of two different mediums such as water and air.
Surface Waves cont
• Surface waves have a rolling pattern of particle motion.
Raleigh Waves
• Occurs in solid rock
• Particles move in elliptical path