Geography - Tectonics 3.2 & 3.3

Geography - T ectonics 3.2 & 3.3 3.2 - Variations in disaster risks caused by earthquakes and volcanic eruptions across places ^ why disaster risks caused by earthquakes and volcanic eruptions vary across places Factors that affect the extent of tectonic disaster risks across places(EARTHQUAKES) EARTHQUAKES 1. nature of hazards: duration & time of shaking a. duration of shaking — longer the ground shakes = more damaging earthquake — buildings/bridges = long period of stress (more likely to collapse) — people likely to be trapped under collapsed infrastructure = more injuries & loss of life — eg. 2011 Tohoku, japan = 9 minutes earthquake = massive damage to buildings b. time of shaking — influences the activities carried out by people and how they respond when the earthquake strikes — @ night = asleep = less alert = unable to evacuate quickly — @ work / school = more alert = able to evacuate quickly — less likely to be trapped = less injuries / loss of life — eg. 1995 Kobe, japan = @ 6am = many asleep = trapped at home = more than 6000 lives lost 2. vulnerable conditions: quality of building design / construction & soil + rock properties a. quality of building design / construction — earthquakes itself do not kill people, buildings do — poorer building design & construction = more vulnerable the buildings are to collapsing = more trapped people (= >die) = disaster risks higher

— vulnerable = low quality materials (zinc - rigid / unable to withstand shaking) = don't follow building codes set by authorities = lack earthquake-resistant features (reinforced steel walls) — eg. 2010 Haiti = buildings made of poor-quality materials (concrete pillars holding up buildings were poorly reinforces) = more than 90% of buildings destroyed - 220000 lives lost b. soil & rock properties — potentially open the area up to other earthquake hazards (liquefaction) — liquefaction = soil is loose and saturated then is shaking — softer soil = higher disaster risks (seismic waves travel from hard rocks > soft soil = waves get amplified) — pass from rock > soil = waves slow down & get bigger — soft & loose soil shake more intensely than hard rocks = increase likelihood of buildings & bridges collapsing (solid rocks - compact = shake less intensely — buildings = vulnerable to collapse (sink into liquefied soil - tip over) — people = likely to be trapped in collapsed buildings (more injuries and loss of life) — eg. 2010 Haiti = seismic waves were amplified = collapse of many buildings = 220000 people lost their life 3. exposure: population density & distance from epicentre a. population density — number of people per unit of area — higher the population density = greater the number of people & buildings exposed to earthquakes — large amounts of people located within buildings = more people located within buildings = trapped = loss of lives — eg. 1995 Kobe, japan = densely populated industrial city (3000 people per km) = 6000 people killed b. distance from epicentre — nearer