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52 Cards in this Set
- Front
- Back
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Richter Scale (magnitude)
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Measures energy of seismic waves. Today, a commonly used Richter scale is known as the local magnitude scale that incorporates modifications for modern recording equipment and regional conditions so it can be used worldwide. NUMBERS.
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Mercalli Scale (intensity)
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Measures intensity of ground shaking. Number value based on human observation. Can be estimated for historical earthquakes. I-XII
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Fault
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Pre-existing geological weaknesses
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Subduction zone
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When one plate bends down to pass beneath another
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Liquefaction
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Where water-saturated material can temporarily lose strength, because of strong shaking, and behave as a fluid.
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Tsunami
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Most distinctive secondary earthquake-related hazard. Result from:
1. Tectonic displacement of the seabed by large, shallow-focus earthquakes, 2. Collapse of volcanic islands, 3. Underwater/undersea landslide, 4. Asteroid collision |
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Epicenter
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A point on earth's surface directly above the hypocenter (point of rupture)
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Ring of Fire
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About 2/3 of all large earthquakes are located here in the Pacific.
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Tension
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Stretching, thinning of crust - normal fault
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Compression
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Shortening, folding - reverse fault
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Shear
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Twisting laterally, bonding horizontally - strike-slip fault
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3 Convergent boundaries
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1. Oceanic-Oceanic
2. Oceanic-Continental 3. Continental-Continental |
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Divergent boundaries
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Splitting apart. Ex: oceanic ridges, rift valleys
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Mantle plumes (hot spots)
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Account for island chains that are isolated from plate margins.
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Accreted terranes
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Account for geologic incongruities between continental interiors and their margins.
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Primary waves
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Vibrations caused by compression. Travel through solids and liquids.
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Secondary waves
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Slower than P-waves. Vibrations travel like waves in a rope held between two people. S-waves travel though solids only. Difficult to design buildings resistant to S-waves.
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Secondary hazards to earthquakes
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Fire, liquefaction, mass movement, tsunamis
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Protection
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Home and lot design - "the wise man." Comply with building codes.
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Adaptation
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Community preparedness (at local level) and recovery planning are key.
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Forecasting
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Detection of physical precursors near the active fault.
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Northridge, CA earthquake
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1994. 6.8 Richter: magnitude. $20 billion. 72 deaths. 22,000 homeless.
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Haiti earthquake
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2010. Magnitude: 7.0. $60 billion. 200,000 deaths. 1.5 million people homeless.
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Pyroclastic flows:
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Gas bubbles burst explosively and eject hot gases, ash, pumice fragments, and glass.
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Tephra
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Ashfall
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Lahar
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Volcanic mudflows. Either primary (due to volcanoes) or secondary (with heavy rainfall).
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Fumarole
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Opening in planet's crust which emits steam and gases.
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Hot spot volcanoes
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Exist in the middle of tectonic plates where a crustal weakness allows molten material to penetrate from the earth's interior.
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Shield volcano
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Volcano built almost entirely of fluid lava flows.
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Strato volcano
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Steep profiles and periodic, explosive eruptions
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Pahoehoe lava
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Flows that are mostly liquid, with a relatively smooth but wrinkled surface.
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Aa lava
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Blocky, spiny and slow moving with a rough, irregular surface.
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3 places volcanoes are likely to occur:
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1. Subduction zones
2. Rift zones 3. Hot spots |
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Primary hazards of volcanoes
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Pyroclastic flows, air-fall tephra, lava flows and volcanic gases
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Secondary hazards of volcanoes
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Mass movement (ground deformation, lahars, landslides, famine) and tsunamis
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Methods of protection
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Damming and diverting lava flows, and volcano-resistant homes
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Methods of adaptation
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Forecasting and warning (precursors to eruption - earthquake activity and ground deformation)
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Hawaii's hazard zones
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Divided into zones based according to the degree of hazard from lava flows (1 is most dangerous, 9 is least dangerous)
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Driving force
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Act of applying force to propel something
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Powder avalanche
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(Sluffs). Occur in powder snow where bonding between crystals is weak. Avalanche often caused by a falling rock. Leaves an inverted V-scar.
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Slab avalanche
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Large slabs break loose where a cohesive layer of snow breaks away from a weaker layer. Sharp fracture line or crown is evident at upper end of the scar. Weight of skier can set slab in motion.
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Rockfall
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Rocks transported through air. Occur on steep slopes where joints or other weaknesses occur. Presence of water is important. Often result from many freeze-thaw cycles.
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Solifluction
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Slow, downhill movement of soil, saturated with meltwater, over a permanently frozen subsoil in tundra regions.
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3 categories of landslides:
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1. Rock fall - through air
2. Slides - movement along slip slope (rotational - curved, transitional - planar surfaces) 3. Flows - fluidised soil moving as viscous mass. |
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Avalanche triggers
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Shear strength decreases as temperatures decrease. Heavy snowfall or rapid thawing. Artificial increase in loading (people). Pack failures.
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Strengthening slopes
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Excavation and filling, drainage, re-vegetation, restraining structures.
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Identify avalanche tracks
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Breaks of slope, eroded channels on hillsides, and damaged vegetation.
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Strom surge
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Offshore rise of water associated with a low pressure weather system, typically a tropical cyclone
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Hurricane development and hazard
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Begin as small areas of low pressure. Become hurricane when wind speed reaches 73 mph.
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Tornado development and hazard
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Warm, moist air from south and cool, dry air from north and mild, dry air from southwest.
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Salfir Simpson scale
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Hurricanes - Categories 1-5
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Fujita scale
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Tornadoes - 0-5
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