1. theory
1.1. earth’s tectonic plates are always moving
2. internal structure of the earth
2.1. core
2.1.1. inner: high pressure :.solid. contains radioactive elements that give off heat
2.1.2. outer: liquid. contains liquid metal -> spins w/ earth's rotation -> magnetic field
2.2. mantle
2.2.1. rigid-upper
2.2.2. upper: molten
2.2.3. asthenospere
2.2.4. lower: dense, rigid
2.3. crust
2.3.1. oceanic:dense, beneath oceans
2.3.2. continental: light, made of continents, floats on O,
2.4. lithosphere
2.4.1. crust + uppermost mantle
3. convection currents
3.1. mantle material is heatedby core->expand& rise & spread out->plates are draggedalong & move awayfrom each other. Hotmantle material cools&sinks -> plate pulled along-> sinking mantle plate heats up near the core. Cycle repeats.
3.2. sinking oceanic plate atsubduction zones pulls rest of plate ->slab-pull force(main driving force forplate movement
3.3. subducting plate drives downwardportion of convection current. Mantlematerial away drives upward portion of convection current.
4. factors influencing impact
4.1. magnitude
4.1.1. higher magnitude greater damage
4.2. distance from epicentre
4.2.1. closer to epicentre = severe damage
4.3. population density
4.3.1. populated areas = more casualties
4.4. level of preparedness
4.4.1. damage is more manageable when ppl are prepared: evacuation plans, trained rescue workers,
4.5. time of occurence
4.5.1. night: when people sleeping = less chance of survival
4.6. type of soil
4.6.1. loose soil = greater damage structures may be affected by liquifaction
5. plate movement
5.1. divergent(constructive)
5.1.1. plates move away
5.1.1.1. O-O
5.1.1.1.1. convection currents-> plates diverge .magma rises in Sea-floor spreading. Lava cools & solidifies = mid-oceanic ridge. New/ young rock nearer ridge. Lava builds up = submarine volcano. surface above water = volcanic island
5.1.1.2. C-C
5.1.1.2.1. tensional forces cause rocks to tear away from each other, forming fractures= faulting
5.2. convergent(destructive)
5.2.1. plates move towards
5.2.1.1. O-O
5.2.1.1.1. denser plate subducts. Oceanic trench at subduction zone. Mantle material melt -> magma rise-> volcano -> arc of islands .friction b/wn rocks -> earthquakes
5.2.1.2. O-C
5.2.1.2.1. denser O plate subducts. point of subduction -> oceanic trench. compressional forces -> C plate -> buckle & fold -> fold mountain. Mantle material melt -> magma -> volcano -> volcanic island Friction b/wn rocks -> earthquakes
5.2.1.3. C-C
5.2.1.3.1. thick, buoyant :. resist subduction. Rock compressed, buckle & fold -> fold mountain (grow when plates -><- )
5.3. transform
5.3.1. slide-> transform fault. stress build up -> earthquakes
5.3.1.1. landform: earthquakes
5.3.1.1.1. example: San Andreas fault ; Pacific+North American
6. Tect plate types
6.1. Oceanic (O): dense rock e.g Basalt Formation: cooled magma. young rock:<200 million years old.
6.2. Continental (C): light rock e.g Granite. range of rock ages: recent - 4 billion years old
7. earthquakes
7.1. a vibration in the earth’s crust caused by the sudden release of stored energy in the rocks found along fault lines
7.1.1. when plates move past, towards or away from each other → movement is not smooth → slow build up of stress (energy/friction) on rocks found on either side of fault rocks can no longer withstand increasing stress (friction) → slip many meters → rocks jerk/break free → release stored energy in form of seismic waves → felt as vibrations on the earth’s surface → earthquake energy comes from friction caused by the movement of plates
7.2. seismic waves
7.2.1. radiate out from a point of sudden energy release =focus(normally found along plate boundaries) point ofearth’scrustdirectlyabovethefocus=epicentremost oftheenergyreleasedbyearthquake travels along the surface of the earth→groundvibratesviolently earthquakes with more shallow focus are stronger -> shortdistance between focus and earth’s crust→ travel less distance→less energy lost→ seismicwaves stronger → reach landsurface quickly
7.3. aftershocks
7.3.1. stress from ground within the earth’s crust cause many smaller earthquakes = aftershocks → occur along the fault line series of aftershocks may occur over several months after initial earthquake some aftershocks nearly as powerful as original eg. center in elazig province: many killed and injured due to earthquake
7.4. distribution
7.4.1. occur mostly at convergent plateboundaries around ¾ of the earthquakeswhich occur each year are found along thepacific ring of fire - eg.tohoku japan 2011 - eg.indian ocean 2004eg.exception:2008sichuanearthquake→occurredconsiderabledistancefromplateboundary→ earthquakeresultoftheconvergenceandsubductionofindianplate under theeurasianplate→broadzone ofeuraisanplatedeformedandfracturedincludingregion ofsichuan
7.5. impacts & hazards
7.5.1. tsunamis
7.5.1.1. unusually large sea wave, usually createdby volcanic or earthquake activity underthe ocean results in tall waves crashingonto the coastal areas
7.5.1.1.1. eg. 2011 tohoku earthquake → caused deadly tsunami that devastated fukushima and many other cities in japan eg. 2004 boxing day tsunami caused by archaea earthquake
7.5.1.2. subduction process causes an uplifting of lighter plate →displace water above it formation of huge waves with long wavelengths reaching shallower water → friction slows the waves → forcesthem to increase in height at point of impact on coast → tsunami waves travel at 30-50km/h reach heights of around 20m sometimes sea recedes from the coast before advancing onshore → caused by vertical displacement of sea floor if sea recedes, only does so in minutes before the tsunamireaches the shore water first rushes to fill the void caused by the movement of thesea floor→ sea recedeswater then forced out again → tsunami
7.5.2. landslides
7.5.2.1. rapid downslope movement of soil, rock and vegetation debris from a slope shaking of ground during earthquake → weaken slopes of hills and mountains unstable slopes → landslides can range from several meters to several kilometers in both length and width
7.5.2.1.1. eg. 1970, earthquake off the coast of peru → destabilized the slopes of mount huascaran and triggered a massive landslide → travelled more than 160km per hour and completely flattened the town of ranrahirca within seconds → death toll: more than 18000 → only 200 people survived eg. mount kinabalu
7.5.3. mudflow
7.5.3.1. occur when there is heavy rainfall → saturates the soil → cause mixed soil debris to flow down the slope often experienced in indonesia and philippines where heavy rainfall is common
7.5.4. loss of properties
7.5.4.1. widespread destruction in many homes people may be without homes after the disaster & reside in temporary shelters eg. tohoku earthquake 2011 → caused tsunami which travelled up to 10km inland → extensive structural damage → hundreds of people being forced out of their homes → severe shortage of housing and concerns about long term consequences on the health of people
7.5.5. disruption to services
7.5.5.1. supply of electricity, gas and water and potentially affect a large area vibrations in ground snap pipes and break cables → outbreak of fires communication service (television broadcasts and telephone connections affected) eg. kobe earthquake, japan, 2004 → damage pipes and transmission lines → disrupted electricity, gas and water pipes for about a million of kobe’s 1.4 mil residents
7.5.5.1.1. fires
7.5.5.1.2. destruction of infrastructure
7.5.6. disruption to lives
7.5.6.1. communities struggle to rebuild themselves education and healthcare services also disrupted → many children put on hold education // many who are sick → unable to seek medical treatment businesses can also be affected → lose jobs and income eg. children in manila fighting for protection against natural disasters
8. early warning systems
8.1. building designs
8.1.1. reduce collapseofbuildings&minimisedamage steelreinforcedconcrete:abletowithstandearthquakesbetterthanmorebrittlematerials eg. taipei 101madeof steel andreinforced concrete,dampingdeviceinstalled such asshockabsorbers for some oftheseismicenergyreleasedduring anearthquaketheyalso actas counterweightswhichmoveinthedirection opposite tothemotionofanearthquake,preventingabuildingfromswayingtoomuchandcollapsingconstructingbuildingswithwide andheavybases decreasesthelikelihoodofthesebuildingfromcollapsingeg.foundation of taipei101isreinforcedbyheavy metal barsbareisolationbearingsmade of rubberorcushioncan beplacedbetween thegroundand thebuildingact asa buffer →preventbuildingfromshaking toomuchduringearthquakewhenearthquakeoccurs,isolationbearingsabsorbthe force oftheearthquakeandreducesmovement ofthebuilding eg.lead rubberbearings usedatthesabinagöcken airport inistanbul
8.1.2. limitation: adds to the cost of construction. difficult to maintain & strengthen existing buildings. regulations may be difficult to enforce and monitor especially in less industrialised countries due to its remoteness eg. bamboo homes in nepal
8.2. earthquake ready infrastructure
8.2.1. communication network
8.2.1.1. communication channels (telecommunications, radio and TV receptions) should be established for early warnings, evacuations and relief measures
8.2.2. critical infrastructure
8.2.2.1. needs to be developed with advanced engineering to withstand potential damage. roads, bridges and dams built to resist shaking of the ground sothatthey do not collapse& can be easily repaired. Homes,office buildings and factories: fitted with trips witches →ensure electrical points are switched off in event of an earthquake. prevents fires from breaking out. In Japan, machines in many factoriesautomatically shut down whentheysenseearthquake vibrations.
8.2.3. limtiations
8.2.3.1. reinforced infrastructure remains untested until an earthquake occurs eg. however, past events in japan and california have benefited from reinforced infrastructure including fewer lives lost, faster rescue and evacuations and less money spent on recovery of the affected area
8.3. public education
8.3.1. emergency drills: form of preparedness measure where people practice the steps to take when a earthquake occurs creates awareness among the population and reduces level of panic and irrational behaviour during an event eg. drop, cover, hold… california practice earthquake drill drills include evacuating to safe locations, listening to instructions given by trained personnel and practicing first aid they may also become members of local response teams that assist people during a disaster eg. since 1960, japan conducts annual emergency drills on 1 sept to commemorate disaster prevention day, where an earthquake of high magnitude is simulated intention is to prepare the people mentally on how to react to a disaster main roads are blocked to create possible road conditions in the event of an earthquake emergency vehicles have to them seek alternative routes to reach affected areas
8.3.2. drills designed based on the most serious earthquake ever recorded in the area in the past --> not prepared for a hazard event of a higher magnitude eg. earthquake in tohoku, japan 2011 was on a scale never experienced before in japan emergency drills and evacuation plans were inadequate to prevent devastation of area affected by the earthquake only effective if there is enough time for people to evacuate, often there is insufficient time for evacuation as earthquakes are difficult to predict
8.4. landuse zoning
8.5. prediction & warning
8.5.1. seismicactivity can be monitored usingseismic risk maps and earthquake sensors
8.5.2. limitation:
8.5.2.1. difficult to predict, inaccurate, costly (usedin DCs), little time for response