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Seismic Waves/Earthquake Notes Review: Scientists study and record ____________________ data and ___________________ activity in order to support the theory of plate tectonics. The evidence proves that there is a distinct relationship between seismic activity, volcanic activity, and the lithospheric plate boundaries. Seismic Data and Plate Tectonics: The interaction along ___________ boundaries results in an increased frequency (occurrence) of earthquakes at those locations. Additionally, stronger earthquakes are more likely to occur along active plate boundaries. Strong earthquakes are more common at___________________ and ______________________ plate boundaries. The San Andreas fault in California is an example of an active transform plate boundary. How are earthquakes measured? Earthquakes are measured using the ____________________________. The strongest earthquake ever measured was a 9.5 on the Richter Scale. This is a measurement of the amount of energy released from the earthquake. The _Richter Scale expresses or measures the magnitude (energy) of an Earthquake and measures the energy released. The scale goes from 1 to 10 . Seismic Waves Activity: Illustrate & explain the seismic waves based on the Pop & Lock Activity. Primary (P) Waves Secondary (S) Waves Surface Waves Seismic Waves (3 types) _______________________________ are waves generated by an earthquake that travel through the Earth. These waves can cause the ground to move forward, backward, up, down, and even to ripple. Seismic Waves are generated at the ____________________ time but move in different ways, and at different speeds. There are 3 types of Seismic Waves: ____________________________________________ _____________________________________________ ______________________________________________ 1 Type of Wave/ Illustration PRIMARY WAVES: P WAVES Position The _______________ seismic wave to move out from the earthquake focus, the point where the energy is released Travel the _____________ of the three waves SECONDARY WAVES: S WAVES The ________________ wave to Move out from the earthquake focus Move _______________ than primary waves Movement Moves through what states of matter ___________ and ______________ Moves through rock creating a back-and-forth _______________ motion in the direction the wave is and ______________ moving…. This known as a layers of Earth (it (___________________________ also can move in gas) wave) A type of seismic wave that compresses and expands the ground Move at __________________ to primary waves causing rocks to move up and down and side to side…this is known as a (_____________________ wave) A type of seismic wave that moves the ground up and down or side to side Can only move through _______________ rock If S-waves can only move through solids, then which EARTH layer can’t it go through? shear waves - move material perpendicular to wave movement SURFACE WAVES Form when _______ and _________ waves reach the ______________ AND THESE WAVES ARE CONSIDERED THE ____________________ SEISMIC WAVES. Especially damaging to buildings Can cause the ground to shake making rock sway from side to side and roll like an ocean wave Travel just below or along the ground’s surface Moves through_________ the states of matter: solid, liquid, and gas Produces motion in the upper crust Motion can be up and down Motion can be around Motion can be back and forth Mainly moves like P & S waves Scientists use the principle that the _______________ and _________________ 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 liquid outer core of Earth; because earthquake waves travel faster through the ___________________ than through the crust, scientists know that the mantle is denser than the crust. 2 MEASURING EARTHQUAKES The energy spreads outward in all directions as vibrations called ________________________. Seismic waves can be measured and recorded by a ____________________________. ______________________________ are instruments or a device that detects and records seismic or earthquake waves. It measures the vertical ground motion and the horizontal ground motions (N-S/EW). It also traces wave shapes onto paper and translates waves into an electronic signal. The vibration record, called a ___________________________, looks like jagged lines on paper. Seismograms are traces of amplified, electronically recorded ground motion made by seismographs. Measuring the time between the arrival of the P and S waves determines the _________________ between the recording seismograph and the earthquake epicenter. SEISMOGRAPH SEISMOGRAM LOCATING AN EARTHQUAKES EPICENTER ______________________________ identifies the epicenter of an earthquake. The location of an earthquake’s epicenter is found by plotting ___________ circles on a map from the records of three seismograph stations and finding the point where the three circles _______________________ Three seismograph Triangulation stations are needed to locate the epicenter of an earthquake. Triangulate means to use three positions to determine an exact location. How do scientists calculate how far a location is from the epicenter of an earthquake? CALCULATING THE S-P INTERVAL: - Scientists calculate the difference between arrival times of the P waves and S waves - The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves 3 4