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Chapter 8 & 9 Earthquakes and Earth’s Interior and Plate Tectonics Earthquakes An ____________________is the __________ of Earth produced by the ___________ release of energy Focus and ________________ • Focus is the point within Earth where the earthquake _______________. • Epicenter is the __________________ on the surface directly above the ______________. Faults • Faults are _____________ in Earth where ___________________ has occurred. • General Features of Earthquakes – Vibrations of Earth_______________ by a sudden _____________ of _______________ – Associated with ___________________ along _____________________ – Explained by the ________________ tectonics ________________ – _______________ for earthquakes was 1st explained by ______________ – Early 1900’s – Rocks “___________________” - phenomenon –called elastic ___________________ Cause of Earthquakes Elastic Rebound Hypothesis • Most _________________ are produced by the ____________ release of _____________ energy stored in -___________ that has been _______________ to great forces. • When the __________________ of the rock is _____________, it suddenly ________________, causing the vibrations of an _________________ Cause of Earthquakes ____________________ and Foreshocks • An aftershock is a _____________ earthquake that ____________ the ____________ earthquake. • A foreshock is a _______________earthquake that often ____________ a _________ earthquake. Earthquake Waves Seismographs are _____________________ that record earthquake ___________________. Seismograms are ______________ of amplified, __________________ recorded ground motion _________________ by seismographs. _________________ – study of earthquake waves ___________________ waves are seismic waves that ___________ along Earth’s outer _______________. Earthquake Waves Body Waves • ___________________ as P waves or S waves • P waves - Are push-___________ waves that push (____________) and pull (____________) in the ____________________ that the waves ________________ - _______________ through ________________, liquids, and ________________ - Have the ___________________ velocity of all ___________________ waves Body Waves • S waves ____________________waves that _______________ along Earth’s __________ layer - ______________ particles at ______________ angles to the ____________ that they travel – Called “Shake _______________________” 1 Chapter 8 & 9 Earthquakes and Earth’s Interior and Plate Tectonics - Travel only __________________ solids - ________________ velocity than P waves A _____________ shows all ____________ types of seismic ___________—surface waves, P waves, and_____________ waves. Locating an Earthquake Earthquake Distance • The ___________ is located using the ______________ in the arrival ________ between P and S wave recordings, which are related to _______________. Earthquake Direction • Travel____________ graphs from three or more __________________ can be used to find the __________ location of an earthquake _____________________. Earthquake Zones • About _________ percent of the _____________ earthquakes occur in a few _______________ zones. Measuring Earthquakes Historically, _________________ have used _________ different types of measurements to describe the ____________ of an earthquake—_____________ and magnitude. ________________ Scale • Based on the ____________________ of the largest ________________ wave • ______________ unit of Richter ____________________ equates to roughly a 32-fold _____________ increase • Does not ____________________ adequately the ____________ of very ___________ earthquakes Momentum Magnitude • Derived from the _____________ of ________________ that occurs along the _____________ zone • _____________ magnitude is the most widely used __________________ for earthquakes because it is the only magnitude ______________ that estimates the _____________ released by earthquakes. • _____________________ very large _________________ Seismic Vibrations The ___________________to buildings and other structures from _____________ waves depends on several ____________. These factors include the _________________ and duration of the vibrations, the nature of the _______________ on which the structure is _______________ and the design of the ________________. Building Design • _________________________that determine __________________ damage - _______________________ of the earthquake - Unreinforced stone or ___________________ buildings are the most ____________ safety threats - Nature of the __________________ upon which the ________________ rests - The _________________ of the ______________________ Liquefaction • __________________- material turns __________________ • _________________ objects may __________ to ______________ Tsunamis _________ of Tsunamis 2 Chapter 8 & 9 Earthquakes and Earth’s Interior and Plate Tectonics • A tsunami __________________ by an earthquake occurs where a ___________ of the ocean floor is ________________ vertically along a fault. • A____________ also can occur when the ____________ of a quake sets an _________________ landslide into __________. • Tsunami is the Japanese word for “_____________ sea wave.” Tsunami Warning System • ___________________ earthquakes are reported to __________________ from Pacific seismic _____________________. • Although _______________ travel quickly, there is __________________ time to evacuate all but the area ___________________ to the ________________. Other Dangers Landslides • With many _____________________, the greatest _____________to structures is from landslides and ground _____________________, or the sinking of the ground triggered by ________________. Fire • In the San Francisco earthquake of ____________, most of the _______________ was caused by_______________ that started when gas and ___________ lines were cut. ___________________ Earthquakes Short-Range Predictions • So far, ________________ for short-__________________ predictions of earthquakes have not been ___________________. ________________-Range Forecasts • Scientists don’t yet understand enough about how and where __________________ will occur to make ___________________ long-term _____________________. • A seismic ____________ is an area along a ___________ where there has not been any _________________ activity for a ___________ period of ______________. Earth’s Major Roles According to the plate tectonics theory, the ___________ mantle, along with the overlying crust, behaves as a strong, _________ layer. This layer is known as the ____________. • A plate is one of numerous _______________ sections of the lithosphere that move as a unit over the _______________ of the ___________________ Types of Plate Boundaries Divergent boundaries (also called _____________ centers) are the place where two ____________ move apart. Convergent boundaries form where ____________ plates move ____________. Transform fault boundaries are ___________ where two plates grind past each other without the __________________ or destruction of the ___________________. Divergent Boundaries _________________Ridges and Seafloor _______________ • Oceanic ridges are continuous elevated zones on the floor of all _____________ ocean basins. The rifts at the ______________ of ridges represent _____________ plate boundaries. • Rift valleys are deep _____________ structures found along the axes of divergent plate boundaries. They can develop on the ________________ or on land. • Seafloor spreading produces new _______________ lithosphere. 3 Chapter 8 & 9 Earthquakes and Earth’s Interior and Plate Tectonics Convergent Boundaries A subduction zone occurs when one oceanic _____________ is forced down into the mantle beneath a _______________ plate. Oceanic-Continental • ________________ oceanic slab ________________ into the asthenosphere. • Pockets of ____________ develop and rise. • Continental volcanic arcs form in part by _______________ activity caused by the subduction of ____________ lithosphere beneath a _________________ • Examples include the Andes, Cascades, and the Sierra Nevadas. Oceanic-Oceanic • _____________ oceanic slabs _______________ and one descends beneath the other. • This kind of _________________ often forms _________________ on the ocean floor. • Volcanic island arcs form as volcanoes emerge from the _________. • Examples include the Aleutian, Mariana, and ________________ islands. Continental-Continental • When __________________ plates contain continental material, two continents collide. • This kind of boundary can produce new ____________ ranges, such as the Himalayas. Transform Fault Boundaries At a transform fault boundary, plates ________ past each other without ____________ the lithosphere. Transform faults • Most __________two segments of a mid-ocean ridge. • At the time of formation, they roughly _______________ the direction of plate movement. • They aid the movement of ____________ crustal material. 4