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 the city is to epicentre = greater number of people / buildings

exposed to the hazard = greater disaster risk (more people are trapped - loss of life) — city nearer to epicentre = less energy absorbed by rocks (before seismic waves reach the city) = seismic waves reaching the city will be stronger = violent shaking — buildings/bridges more likely to collapse (loss of life) — eg. 2010 Haiti, epicentre = 2.5km west of city = 220000 deaths Factors that affect the extent of tectonic disaster risks across places (VOLCANIC ERUPTIONS) VOLCANIC ERUPTIONS 1. nature of the hazard: type of magma — high / low silica magma — type of magma = eruption is explosive / effusive - affecting the extent of disaster risk a. high silica magma — more viscous — explosive eruption — highly destructive pyroclastic flows = widespread damage to infrastructure = significant injuries / loss of life — explosion of volcanic materials = strike people / properties = injuries / loss of life — eg. 2010 Indonesia = pyroclastic flows (3kms down the heavily populated mountain sides) > volcanic bombs (spread over a distance of 10km) > 350 killed b. low silica magma — less viscous — gentle/effusive eruption — lava flows far from the volcano before cooling + rarely kill people (can avoid the pathway of lava) — damage infrastructure / properties = over large areas (within the geographic region of the volcano) — eg. 2018 Kilauea, Hawaii = 24 injuries = $800m property damage

2. Vulnerable Conditions: availability of surface + groundwater & prevailing wind conditions a. availability of surface & groundwater — greater the availability of surface & groundwater = more likely lahars can develop — increases the vulnerability of people / properties = increasing disaster risks (lahars - landslides) = bury / destroy properties = more injuries / loss of life — large quantities of water — rapid melting of snow / ice (on volcano's summit before/during eruption) — groundwater release through cracks / fracture during eruption — existing river / lakes nearby — heavy rainfall — eg. 1991 Indonesia, triggered by heavy rain (monsoon season) = destroyed 100000 homes b. prevailing wind conditions — strength and direction of prevailing winds = affect the distribution of ash fall & tephra = influence extent of disaster risk — ash fall & tephra = carried to human settlements — larger area affected = higher number of people / properties vulnerable — heavier / larger particles deposited close to volcano — finer ash particles = smaller and lighter = carried & deposited hundreds/thousands kilometres away from the volcano (people likely experience health issues - respiratory problems) — properties = damaged (weight of the ash accumulated on roofs - collapse) — crops = destroyed — eg. 1991 Philippines eruption = ash fall & tephra = spread a large distance (fast wind speed) = 90000 hectares of damaged farmland 3. exposure to volcanic eruptions: presence of human settlements — presence of human settlements = increase exposure of people / properties to volcanic hazards = increase disaster risks caused by volcanic

eruptions — however.. people choose to live near volcanoes? — volcanic soil = rich & fertile (ideal for farming) — geothermal energy = harnessed to produce electricity — valuable minerals = sulphur (can be mined) — eg. mount Sinabung (Indonesia) = active volcano (several explosive eruptions) = many continue to live & work within restricted zone (3km) = fertile soil for farming summary of conditions that influence the disaster risks that occur EARTHQUAKES: 1. duration 2. time 3. quality of building/infrastructure 4. soil and rock (type of ground) 5. population density 6. distance from epicentre VOLCANIC ERUPTIONS: 1. type of magma 2. availability of surface and groundwater 3. prevailing wind 4. presence of settlement 3.3 - Effectiveness of strategies in building community resilience to earthquakes & volcanic eruptions ^ strategies in building community resilience are important for communities living in hazard-prone zones to resist, adapt and recover from the impacts of disasters in a timely & efficient manner How to strengthen community resilience: — the strategies to build community resilience 1. land use planning = reduce exposure 2. hazard-resistant designs = reduce vulnerability 3. developing monitoring + warning systems = reduce vulnerability

4. disaster response & recovery = increase preparedness 1. land use planning (reduce exposure) — control & minimise development in high risk areas = decrease potential loss of lives / damage to properties — using hazard maps = strict guidelines to control development are implemented — hazard maps = identify areas at risk & use data on past earthquakes — suggest levels of risk = indicate the likely extent of disasters — eg. 1933 Japan tsunami = land use planning implemented = residential land use on coastal areas (shifted to higher ground) — (linked) 2011 Japan earthquake = houses on higher ground = not destroyed 2. hazard-resista