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EARTHQUAKES II Earthquakes Release Stored Potential Energy When rocks break and an earthquake occurs a significant amount of _____________________ is released. The energy travels through Earth in the form of ______________. These waves are called ____________________. The waves start in the crust where the rocks break and travel __________________ in all directions from this point. This outward traveling energy causes Earthquake ________________. Focus vs. Epicenter • ___________: • The focus is the ____________________ of an earthquake. • It is where the rock actually snaps and ________________ occurs. • Most of the time it is __________________ (as least 65 km down). • ___________: • The ___________ on Earth’s surface directly ____________ the focus. • This spot experiences the ___________________ during the earthquake. • After an earthquake, the earthquakes ___________ is given by the _______________ location. Seismic Waves • When there is movement at a fault, energy is released in the form of __________________________: • The shaking occurs as the energy travels _______ from the ___________. • Like throwing a stone in a pond, the ripples of water move out in all directions. • There are two types of waves released • _________________________ – travel through Earth • _________________________ – travel on Surface Seismic Waves – Body Waves ____________: A ___________ moving ____________________ body wave that can travel through both ____________ and _____________. Because they travel through liquids and solids, P-waves can travel through the liquid and solid interior of Earth and ________________________ on the _____________________ of Earth. • P-Waves (Primary – Think _____________) 1. _____________ waves: Arrive at a location before any other wave. 2. _____________ waves: Travel at the highest speed (6km/sec.) 3. _____________ waves: Pushes & Pulls at rock as it travels through it. 4. ___________________ – can travel through magma. EARTHQUAKES II Seismic Waves – Body Waves _____________: A ______________ moving body wave that travels at _________________ to the primary wave and ______________________ through ______________. Because they travel through solids only, the S-waves _________ travel to the ____________ of Earth. When they _________ the _________ magma interior of Earth, they reflect back eventually stopping. S-Waves (Secondary – Think ___________________________) o ________________ waves: Waves that arrive second at a location. o ________________ waves: Travel at the slow speeds (about ___ of P wave - __________.) o ________________ waves: Vibrate and move up and down. o ________________ waves: travel through solid rock only. Seismic Waves – Surface Waves • __________ Waves (Think ________________________) 1. Waves that propagate _________________________________ 2. Created when ___________________ reach the ____________ 3. The surface _________ like an ocean wave. 4. They are the ___________ type of waves. • Surface waves are the _________________________! We measure all of these seismic waves using a _________________________ • It draws a __________ pattern that depicts the seismic waves motion. • It creates a print out called a ______________________. By looking at a seismogram, two conclusions can be made. 1. _____________________ of the waves. 2. _______________ to the Earthquakes epicenter. P-waves are the __________ to arrive S-waves are the __________ to arrive Surface waves are the ____________ to arrive o The _______________ the distance between the S and P waves, the ______________ the earthquake epicenter. o Examples: Race car racing a station wagon…the longer the race, the larger the distance between the two cars EARTHQUAKES II What if you want to find the _______________ to an _______________? • Use a _______________________ graph • It shows the _____________ travel times for ______________ waves. 1. Find the time _________ the ___ & ___ wave (either from the seismogram, or it may be given to you). 2. Use the time-travel graph and find the ________ on the graph where the S and P waves are _____________ by the _____________________ in step 1 above. 3. __________ a _______ straight down at the location and ________ the ____________ off the graph. What if you wanted to find where the earthquake occurred? • Once an earthquake occurs, you can determine its location. • _____ seismograph stations must ___________ the seismic waves. • Using the ____________ time of the waves, the station can say that the earthquake occurred within a certain _____________ (distance). • Once 3 stations map out the radius, the ____________ ________ is where the 3 circles ____________ each other. • This is referred to as _______________________: Commonly used by geologists to find the ______________ of Earthquakes. HOMEWORK QUESTIONS 1. Identify / label each diagram 2. What waves always reach a seismograph station first? _____________ Second? _______________ 3. Label the P, S, and Surface waves on the seismogram. 4. Was the epicenter closer to station A or station B?___________ Why? 5. At which station was the earthquake felt the most intensity? 6. What was the lag time between the P and S waves at station B (each line represents 5 min. of time)?