Monday 9/30 QOD ---- on left p12 Write out your answer in a complete sentence. 1)What causes an earthquake to occur?

Earthquakes & Their Parts 9/30right 13 Standard 8.3.8: Explain how earthquakes result from forces inside the Earth. Standard 8.3.2: Explain how scientists use seismic waves – primary, secondary, and surface waves – and Earth’s magnetic fields to determine the internal structure of Earth.

Earthquake Photos /Earthquakes?aut huser=0&feat=directlinkpicasaweb.google.com/ /Earthquakes?aut huser=0&feat=directlink

Remember from the Landforms notes…. Forces and stresses ( tension, compression, and shearing ) along faults can build up as blocks of rock are pushed ( compression or shearing ) or pulled apart ( tension ). If the pressure or stress becomes too great, the rock breaks at a weak point along the fault, and energy is released.

seismology earthquake the study of earthquakes the movement of the ground caused by waves of energy released as rocks move along faults – Most occur along plate boundaries

fault focus epicenter surface along which rocks break and move the specific point in the crust (or mantle) where the energy is released the point on the Earth’s surface directly above the focus – Energy that reaches the surface is greatest at this point.

seismic waves the energy waves that move outward from the quake’s focus and make the ground shift There are three major types of seismic waves: – Primary wave – Secondary wave – Surface waves (also called L-wave or love wave or R-wave or raleigh wave)

Basics About Waves Key Points: (8-6.1 & 3)Recall that waves transmit energy but not matter.Recognize, recall, interpret and illustrate factors that influence the basic properties of waves.

Waves A rhythmic disturbance that transfers energy without carrying matter. Are created when a source of energy (force) causes a vibration. When waves travel through a medium, the particles of the medium are NOT carried along with the wave (just the energy).

Vibration Medium A repeated back-and-forth or up-and-down motion. The material through which a wave can travel. It can be a solid, liquid, or a gas. All waves can transmit energy through a medium, but only certain waves can transmit energy through empty space (no medium)

Longitudinal waves particles of matter in the medium vibrate by pushing together and moving apart parallel to the direction in which the wave travels. Compression: the place on the wave that particles are pushed together. Rarefaction: the place on the wave that particles are further apart. Examples: sound waves (and some seismic waves) /basic-waves-theory.html

Transverse Waves Waves in which the particles of matter in the medium vibrate by moving back and forth and are perpendicular to the direction the wave travels. Examples: waves on a rope, strings on a musical instrument, and some seismic waves.

Crest Trough Sketch and Label the drawing in your notebook. The highest point in a transverse wave. The lowest point in a transverse wave.

Amplitude Sketch and Label the diagram. A measure of the distance between the resting point and a crest or trough. The greater the amplitude… the greater the force which created the wave the greater the energy that is being carried by the wave Transverse waves will be higher. Sound waves will be louder. Light waves will be brighter.

Wavelength A measure of the distance from the crest on one wave to the crest on the very next wave. (or trough to trough) Shorter wavelengths are influenced (affected) by the frequency. A higher frequency causes a shorter wavelength and greater energy. Sketch and Label the diagram.

Frequency Sketch and label the diagram. A measure of how many waves pass a point in a certain amount of time. The higher the frequency… the closer the waves are together the greater the energy carried by the waves will be

Speed A measure of the distance a wave travels in an amount of time. Determined by: the type of wave and the nature of the medium Waves travel at different speeds in different media. As a wave enters a different medium, the wave’s speed changes. All frequencies of electromagnetic waves travel at the same speed in empty space.

P-waves “primary” Move out from the focus, Longitudinal (compression) wave (like an accordion) fast moving --- first to arrive travel through liquids and solids

S-waves “secondary” Move out from the focus transverse wave (up & down OR side-to-side  perpendicular to direction of wave) slow moving travel through solids only

Surface Wave (L- or R-wave) P and S waves are called surface waves when they reach the surface. If the focus is not too deep, these waves can be the most violent. Cause the ground to shake, and roll like an ocean

How we know what’s inside the Earth. Scientists use the principle that the speed and direction of a seismic wave depends on the material it travels through. Because of the behavior of these different waves, scientists have indirect evidence for the solid inner core and the liquid outer core of the Earth. Because earthquake waves travel faster through the mantle than through the crust, scientists know that the mantle is denser than the crust.

seismographs an instrument used to record the vibrations caused by the seismic waves of earthquakes

seismograms The vibration record that shows the time and strength of each seismic wave reaching that station. – looks like jagged lines on paper.

S-P Interval: the time difference between the arrival of the p- and s- waves at one seismograph station. - Use an s-p interval graph to determine the distance to the epicenter.

triangulation Identifies the epicenter of an earthquake Found by plotting circles on a map from the records of three seismograph stations and finding the point where the 3 circles intersect.

p.14 Homework Diagram, label, and provide short descriptions of a focus, epicenter & fault. Contrast the three major types of seismic waves.