GEOL110_Natural Hazards CH4
GEOL110_Natural Hazards CH4 GEOL 110
Long Beach State
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This 5 page Class Notes was uploaded by Doris M on Wednesday April 20, 2016. The Class Notes belongs to GEOL 110 at California State University Long Beach taught by Ewa Burchard in Spring 2016. Since its upload, it has received 10 views. For similar materials see Natural Disasters in Geology at California State University Long Beach.
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Date Created: 04/20/16
Tsunamis Objectives for the Lesso n -‐What is the trend of population on coastal areas ? -‐How can we minimize tsunamis ? -‐What should we do when there's a warning issued ? Japan 2011: Tsunami and Nuclear Disaste r -‐over 8 M -‐flooded the coast and nuclear power plan t -‐created from a subduction zon e -‐when the plates move, the subduction zone -‐one moves below the other move s above -‐elastic rebound -‐compression -‐the subduction zone is on the ocean floo r -‐there was about 3000 km of water above -‐all of the water moved the rock s -‐on the open ocean, the wave isnt noticeable -‐energy released by the movement of the wave, an d now energy is stored with in the wave and moving in all direction s -‐the waves that are moving away are related to the coastlin e -‐the waves that are closer to the coast is known as the local tsunami wav e -‐the distant tsunami wave moved towards the water away from the coas t Intro to Tsunamis -‐tsunami is Japanese for "Harbor wave " -‐caused by a sudden vertical displacement of ocean wate r -‐triggered by: -‐large earthquakes that cause uplift or subsidence of sea floo r -‐underwater landslides -‐volcano flank collapse -‐can displace water and create tsunami s -‐submarine volcanic explosion -‐asteroids -‐can produce mega-‐tsunamis -‐during high tide, there is al ready elevated surface area, and so the tsunami would be highe r -‐Chart: Some Historic Tsunami s How Do Earthquakes Cause Tsunamis ? -‐movement on the ocean floor has to be significant to create a tsunam i -‐must be upward movemen t -‐1: Earthquake uplifts or downshifts the seafloo r -‐2:Tsunami moves rapidly in deep ocea n -‐3:Tsunami nears land, loses speed, gains heigh t -‐4: tsunami moves inland destroying everything in its pat h -‐tsunamis travel quickly -‐by knowing the depth of the ocean, you can find the tsunami's velocity -‐when the tsunami reaches the coast, the ocean slows down because of the frictio n -‐in an open area, the tsunami will reach deepe r -‐if there is vegetation it would slow the tsunami down the more vegetation, the bette r -‐all the parameters, will affect the amplitude of the tsunam i -‐tsunami carries a lot of energy and destroys -‐the more energy the more destruction -‐when the ocean recedes from the coast, it is significant because it can indicate if there was an earthquake and whether a tsunami will hi t -‐the first tsunami wave doesn’t have to be the stronges t -‐when the water recedes its an indication that another wa ve is coming -‐uplift-‐Ep-‐driving horizontal movemen t -‐split into local and distant waves height -‐1/2 of original dome Distant tsunami -‐travels out to sea -‐travels long distances with loss ov energy Local Tsunami -‐travels toward land quickly -‐ppl have little time to react How do Landslides cause Tsunamis ? -‐Alaska tsunami -‐created by landslide -‐created an abnormal water surg e -‐the tsunami wave was about 20 meters -‐vegetation affected and sediment was deposite d -‐Papa New Guinea -‐15 meters high -‐different coast have different tsunami hazard s -‐some have greater hazard, significant hazard, or low hazar d -‐greatest hazard: return per. Less than 500 yr s -‐significant hazard: 500-‐2000 yrs of return per. -‐low hazard: 2000+ yrs of return per. -‐shape of shoreline, vegetation Indonesian Tsunami -‐felt also in Africa -‐ppl not well educated and so ppl didn’t know how to behav e -‐after the tsunami there weren't proper precautions take n -‐located near subduction zone -‐megathrust faults associated with subduction zone s -‐no warning system -‐no measuring system of tsunami wave s -‐ppl were unfamiliar with tsunami wave s -‐animal behavior-‐elephants observed that there was going to be a disastrous event s -‐in the Indian ocean, there is subduction and the Australian plate is affecte d iclicker What happenes as a tsunami near land? The height of the waves inc…. If Kilauea volcano in Hawaii collapsed into the pacific ocean, areas of Oregon may experience a -‐distant tsunami The two waves created from a single wave (as seen in the figures) are called the -‐local and distant waves A local tsunami -‐can arrive quickly, giving little warning time . According to the map, which of the following has the least relative hazard f rom tsunamis? -‐Florida Tsunami Hazard Summary and Revie w 8.9 Magnitude earthquake occurred at the depth 1000 m, at the subduction zone: Indian and Burma plates. What is Tsunami velocity ? -‐velocity= (square root) Ex of Historical Tsunami Hazard s -‐there can be earthquakes that can trigger the slopes -‐any volcanic island located on the ocean can erupt can cause mass wasting or cause an eruption of a volcano -‐1883: volcano collapse: Krakatoa -‐Indonesia -‐there were 3 volcanoes -‐since the 1950's the volcano grew in heigh t -‐in the summer, it became restless -‐a tectonic plate pushed below the other and caused lava to move up and go thru the volcan o -‐3 small volcanoes on top of a larger on e -‐there are new volcanoes growing aroun d it -‐local tsunami for all the coasts Tsunami Hazard Effects -‐Primary effects -‐inundation of water and resulting flooding and erosio n -‐shorten coast line -‐debris erodes both landscape and human structure s -‐secondary effects -‐fires -‐from erupted gas lines or other source s -‐contaminated water supplies -‐floodwaters, wastewater treatment plant s -‐disease -‐come in contact w/polluted wate r Causes of Tsunamis -‐natural service functions , -‐bring nutrients from the ocean to coastal so ils -‐bring in sediment needed to build shoreline s -‐help us better understand tsunami hazard s -‐humans cant prevent or control tsunami s -‐humans don’t affect frequency or magnitud e -‐increased use of shoreline increases consequence s Detection and Warnin g -‐the pacific ocean has measuring system s -‐America is a little bit more prepared when it comes to detecting tsunami s -‐tsunaimeters are located on ocean floor s -‐the antennas can transfer info about possible tsunami s -‐ the ocean floor can inc in pressure and the devices can detect inc water pressure -‐land uses -‐creating hazardous zones -‐tsunami hazard zones -‐analysis -‐probability of a tsunami happenin g Education -‐recognizing evidences of tsunamais Tsunami Runup Map -‐runups: elevation waves Structural Control -‐Building Designs -‐houses and small buildings unable to withstand even one to 2 meter wave s -‐larger structures can be engineered to greatly reduce or minimizes destruction s -‐houses can be designed precifically for a tsunami wave -‐sea walls -‐located on Japanese coast The Ring of Fire -‐on the East coast there are also tsunami hazard s -‐closer to the Atlantic ocean La Palma -‐Cumbre Villeja erupsts unpredictably -‐change being taken place in the ven ts -‐deep in the volcano, there are 2kinds of rock s -‐one lets water in, the other collects wate r -‐a breakoff of a volcano can cause a tsunam i Land use -‐vegetation helps defend against tsunami s -‐vegetation helps prevents hazard s -‐prevents coastal erosio n -‐planting vegetation and wetlands are importan t Education -‐tsunami watch: there was a trigger-‐ a landslide or earthquake -‐there could be a possible tsunami -‐tsunami warning: a tsunami already happened and the scientists fig ure out how long it will take for the tsunami to hit -‐just because the first tsunami wasn’t strong, doesn’t mean the second one won t Tsunami Ready Status -‐higher ground Perception and Personal Adjustment Tsunami Hazar d -‐do not assume that if there are no waves the area is saf e -‐pollution created by tsunami and nuclear power plant explosions, the contamination can cause a concentration of radio active isotopes towards the coas t Which is not a way a tsunami hazard can be minimized ? -‐clearing all coastal vegetation What us the problem with building seawalls to protects against a tsunami ? -‐They could cause a false sense of securit y Even if a community is "tsunami", what
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