Disaster Readiness and Risk Reduction - Earthquakes, Seismic Waves - PDF

DISASTER READINESS AND RISK or side-to-side REDUCTION perpendicular to the direction that the wave is EARTHQUAKE: is the sudden mo...

DISASTER READINESS AND RISK or side-to-side REDUCTION perpendicular to the direction that the wave is EARTHQUAKE: is the sudden movement travelling. of the ground that releases elastic energy 2.​ SURFACE WAVES: Surface stored in rocks and generates seismic waves can only travel along the waves. surface. -​ LOVE WAVE: Love waves GROUND SHAKING: Ground shaking or cause rocks to move vibration is what we feel when energy built horizontally or side to side. up by the application of stress to the Transverse. No vertical lithosphere is released by faulting during motion. an earthquake. -​ RAYLEIGH WAVE: Rayleigh waves cause SEISMIC WAVES: These are elastic rocks to move upward, up, energies that travel through the Earth’s backward, down. Ground layers. roll. Transverse. -​ Seismic waves are the waves of HOW IS GROUND SHAKING energy caused by the sudden MEASURED?: The strength of ground breaking of rock within the earth or shaking is measured in terms of frequency an explosion. content of shaking, velocity, acceleration, -​ They are the energy that travels and duration. through the earth and is recorded HOW INTENSE IS GROUND SHAKING?: on seismographs. Based on: TYPES OF SEISMIC WAVES: -​ Earthquake Magnitude 1.​ BODY WAVES: They can travel -​ Depth of Focus through the interior of Earth from -​ Distance from Epicenter the focus to the distant points on -​ Duration of Shaking the surface. -​ P WAVES: This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through. -​ S WAVES: The second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock. S waves move rock particles up and down,  -​ Avoidance of active fault trace and high-risk danger zone GROUND RUPTURE: Earthquake faults HOW FAR FROM THE FAULT IS SAFE that have reached the surface. FROM RUPTURING?: 5 meters setback FAULTING: The displacement of rocks regardless of building type along a fracture surface, and the fracture along which movement has occurred is a LIQUEFACTION: This is a process by FAULT. which water-saturated sediment -​ NORMAL FAULT: The hanging temporarily loses strength and acts as a walls move down relative to the fluid. footwall as a result of extension. TYPES OF LIQUEFACTION: -​ REVERSE FAULT (thrust): The 1.​ FLOW FAILURE: Most dangerous hanging walls move up relative to type. Occurs on liquefiable slope the footwall as a result of material with steepness. compression. Most dangerous. 2.​ LATERAL SPREAD: Blocks or the -​ STRIKE-SLIP FAULT: Two blocks broken pieces of the flat ground. of crust slide past each other on 3.​ GROUND OSCILLATION: Ground the same plane. The motion is right is unable to spread and instead or left lateral instead of up and oscillates like a wave. The surface down layer, riding on a buried liquefied MEASURES TO MINIMIZE THE layer, is thrown back and forth by EFFECTS OF GROUND RUPTURES: the shaking and can be severely -​ Sound engineering and deformed. construction practice may be 4.​ LOSS OF BEARING STRENGTH: adopted to prevent total Loss of strength of sediments destruction. resulting in tilting of houses or -​ Look for local Active Faults in your buildings. area  5.​ SETTLEMENT: settlement caused TYPES OF LANDSLIDES: Landslides by ground failure can cause detach, transport, and deposit earth buildings to displace, tilt, stretch, materials such as solid or loose rocks and twist, buckle or a combination of all soil. five. 1.​ TOPPLES: Occur suddenly when EFFECTS OF LIQUEFACTION: a massive part of very steep -​ Caused sinking of buildings and slopes break loose and rotate vehicles. forward. -​ Sinking, spreading, and cracking of 2.​ ROCK FALLS: Involve chunks of ground. detached rock that fall freely for -​ Seepage of water that leads to some distance or bounce and roll flooding. down the steep slope. MITIGATING LIQUEFACTION: 3.​ SLIDES: Involve large blocks of -​ Hazard zone maps bedrock that break free and slide -​ Building liquefaction-resistant down along a planar or curved structures surface. -​ Improving the existing soil 4.​ LATERAL SPREADS: Triggered by earthquake. Slope material LANDSLIDE: Movement of a mass of loses cohesion through liquefaction rock, debris, down a slope. Landslide is a caused by the shaking. common term used by many people to 5.​ FLOWS: Involve down slope describe sudden events in which large motion of soil made mobile by quantities of rock and soil plunge down water saturation. Mudflows and steep slopes. Earthflows are examples of this. WHY LANDSLIDES OCCUR?: A change 6.​ COMPLEX SLIDES: Combinations in stability of a slope can be caused by a of two or more types of movement. number of factors acting together or alone. These factors include: CONTROLLING FACTORS IN MASS -​ REMOVAL OF SUPPORT: At the WASTING: base of a slope which may be due -​ SLOPE ANGLE: As the slope to erosion at the toe of a slope by angle increases, the tendency to rivers or ocean waves. slide down the slope becomes -​ GROUNDWATER (pore water) greater. When shear stress > PRESSURE: During sudden shear strength, downslope changes in the water level of movement occurs. All forces bodies of water adjacent to the resisting movement downslope can slope also acts to destabilize it. be grouped under the term shear -​ VOLCANIC ERUPTION: Bulging strength. of slopes and the force of volcanic -​ ROLE OF WATER: Angle of material ejection or emission. Repose, the steepest slope at -​ INTENSE RAINFALL: Weakening which a pile of unconsolidated of the slope material by water grains remain stable. Addition of saturation. water from rainfall or snowmelt -​ SNOWMELT: Same effect as in adds weight to the slope. saturating slope material. -​ ROLE OF EARTH MATERIALS: -​ EARTHQUAKES: Sudden shaking Weak materials and structure. of hilly and mountainous areas. Weak rocks (sedimentary) will -​ HUMAN INTERVENTION  weather more quickly than hard -​ METEORITE IMPACT: Meteorites rocks (igneous). impacting the ocean can trigger -​ ROLE OF TIME: Physical and tsunamis. chemical weathering can weaken HOW TO ESCAPE A TSUNAMI: slope materials decreasing -​ The idea is to get out as quickly as resisting force. This causes the possible with your family. rock to become very weak and -​ Know the evacuation center. mass wasting occurs. -​ Take only escape routes that are EFFECTS OF LANDSLIDES: safe from the tsunami waves and -​ Loss of lives floods. -​ Injuries -​ Cling on to floating objects to -​ Damage to structures prevent drowning. Stay alert at all -​ Alteration of agriculture and times. changes to natural ecosystems HOW TO PREPARE FOR A TSUNAMI: -​ Relocation of some human -​ Take the occurrence of an population and infra to new areas. earthquake as a natural alerting MITIGATING THE EFFECTS OF mechanism. LANDSLIDES: -​ Always keep a radio or other -​ Recognizing and reporting any sources of information. sign of slope instability. -​ Bringing a survival kit with you all -​ Monitoring and preventing the time. construction and other activities on NOTABLE TSUNAMIS: unstable slopes. -​ 9.1 magnitude. Sumatra, -​ Planting of deeply-rooting trees Indonesia. December 26, 2004. holds slope material together and -​ 9.0 magnitude. North Pacific reduces slope’s water load. Coast, Japan. March 11, 2011. -​ Landslide barriers and drainage -​ 7.9 magnitude. Moro Gulf Tsunami, structures. Western Mindanao. August 17, 1976. TSUNAMI: A tsunami is a series of waves EFFECTS OF TSUNAMI: caused by the displacement of a large -​ Devastating effects to life, property, volume of water. and the environment. CAUSES OF A TSUNAMI: A basic -​ Loss of lives due to drowning, requirement is the presence of vertical building collapse, impact of various fault movement that generates sufficient kinds of debris, and sometimes displacement and disturbance of the electrocution. surrounding water. MITIGATING THE EFFECTS OF -​ LANDSLIDE: Landslides occurring TSUNAMI: under the ocean and coastal -​ LGUs and government agencies landslides displacing ocean water. concerned need to constantly -​ VOLCANIC ERUPTION OR remind people through information EXPLOSION: Any submarine or and education campaigns. coastal volcanic activity and -​ Protecting properties – products that can trigger tsunami construction of new buildings are by displacing large volumes of banned, constructing seawalls. water. -​ Engineers can design and build tsunami-resistant buildings. VOLCANIC HAZARDS: A volcanic hazard -​ TYPES OF LAVA FLOW: is the probability that a volcanic eruption 1.​ BASALTIC LAVA: Fastest or related geophysical event will occur in a Flowing Lava. Associated given geographic area and within a with shield volcanoes specified time. - Lava Flow Styles: LAVA FLOW: Product of quiet effusion of 1.​ Pahoehoe: smooth molten rock or magma beneath a volcano. surface. Inner parts Temperature ranges from 700 to 1,200 flow continuously. degree Celsius. Extremely low speed. 2.​ A’a: sharp spiny Generation of Magma. surface. Lava -​ LAVA EFFUSION AND hardens more EXPLOSIVE ERUPTIONS: As quickly as it flows magma rises to the surface where - Both flow types are the pressure is less, gas dissolved associated with lava in the magma expands. The fountains. volume of gas expands as 2.​ ANDESITIC LAVA: pressure is reduced. Too much gas Associated with gives magma’s explosive stratovolcanoes. Commonly character. form lava domes. Travelling - Explosive eruptions: tephra below 5m per day. - Quiet eruptions: lava 3.​ RHYOLITIC LAVA: Slower -​ AMOUNT OF GAS: It determines than andesitic and basaltic the material that comes out and flow. Associated with the type of landform. Dependent violent eruptions. on viscosity. 4.​ SHEET LAVA: Thicker than - Composition and Temperature: Pahoehoe. Associated with a.​ Silica Content violent eruptions. b.​ Viscosity increases in 5.​ PILLOW LAVA: decreasing magma Pillow-shaped rocks formed temperature. by sudden cooling of lava. c.​ Low viscosity, least explosivity. EFFECTS OF LAVA FLOW: Damage or -​ It causes irritation of the total destruction of land and property by eyes at low concentrations. burying, crushing, or burning. Deaths due -​ 30 minute exposure to 500 to explosive showers of molten spatter. ppm will cause dizziness, MITIGATING THE EFFECTS OF LAVA headache, and diarrhea. FLOW: 6.​ FLUORINE -​ Stay away from lava flow danger 7.​ HYDROGEN HALIDES: (HF, HCl, zones. HBr) Strong, toxic acids. When -​ Diversion of lava flow by using magma ascends close to the explosives and barriers. surface, volcanoes can emit the -​ Engineered barriers and diversion halogens fluorine, chlorine and channels bromine in the form of hydrogen halides (HF, HCl and HBr) These VOLCANIC GASES: Volcanic gases are species are all strong acids and gases given off by active volcanoes. The have high solubility; therefore they principal components of volcanic gases rapidly dissolve in water droplets are: within volcanic plumes or the 1.​ WATER VAPOR atmosphere where they can 2.​ CARBON DIOXIDE: Abundant potentially cause acid rain. Natural Product of respiration EFFECTS OF VOLCANIC GASES (1991 -​ 2-3 % Shortness of breath Mt. Pinatubo Eruption): During very large -​ 7% Headache, shortness of eruptions, SO2 can be injected to altitudes breath, dizziness, loss of of greater than 10km into the mental ability, weakness, stratosphere. Here, SO2 is converted to and ringing of ears. sulfate aerosols which reflect sunlight and -​ 10% Loss of consciousness therefore have a cooling effect on the within 10-15 minutes. Earth's climate. -​ >15% Lethal- -​ 20 million metric tons of sulfur unconsciousness or death. dioxide -​ Weakness and ringing of -​ Earth’s surface cooled by about ears. 0.5 degree Celsius for 3 years. 3.​ SULFUR DIOXIDE: Colorless gas -​ Sulfate aerosols accelerated chem. with strong odor Reactions that led to acceleration -​ 6-12 ppm irritation of the of ozone layer’s depletion. nose and throat MITIGATION MEASURES FOR -​ 20 ppm irritation of eyes VOLCANIC GASES: -​ 10,000 ppm – irritation of -​ Evacuation and resettlement of skin affected population. -​ Its inhalation at very high -​ Use of automated gas alarms. concentrations should be -​ Use of a gas mask. avoided as it is harmful to -​ Staying hydrated (sulfur the upper respiratory tract compounds) and bronchi. -​ Avoid overexertion. -​ Irritation of skin. -​ Stay indoors, close windows and 4.​ HYDROCHLORIC ACID doors. Use an air conditioner. 5.​ HYDROGEN SULFIDE: A colorless, flammable gas with a PYROCLASTIC FLOWS: Hot mixtures of strong, offensive odor. fresh lava, gas, rock, and ash. Mobility and Speed: MITIGATING THE EFFECTS OF - Gas content PYROCLASTIC FLOW: - Heat of its components -​ Pyroclastic Flow pathways such as TYPES OF PYROCLASTIC FLOWS: valleys 1.​ MERAPI-TYPE PYROCLASTIC FLOW: arises from collapse of the TEPHRA FALLS AND BALLISTIC lava dome whereby large lava PROJECTILES blocks are crushed into smaller -​ TEPHRA refers to volcanic rock particles during movement down and lava materials that are ejected the steep slope. Due to gravity. into the air by explosions or carried 2.​ PELEAN-TYPE PYROCLASTIC upward by eruption column’s hot FLOW (Nuee ardente): eruptions gases or lava fountains. occur when a large quantity of gas, -​ BALLISTIC PROJECTILES are a dust, ash and lava fragments are special kind of tephra. It follows a blown out of a volcano’s central projectile path as these are forced crater. Due to explosion. out of the vent at steep angles. 3.​ SOUFRIERE-TYPE TYPES OF TEPHRA FALLS AND PYROCLASTIC FLOW: the BALLISTIC PROJECTILES eruption column (ash and tephra) 1.​ ASH: 64 mm pyroclastic flows on the flanks of diam the volcano. -​ Bombs: fresh magma, NOTABLE PYROCLASTIC FLOWS: smooth. -​ Vesuvius, Italy, 79 A.D. -​ Blocks: chips of walls of -​ Tambora, Indonesia, 1815 volcanic vent, rough with -​ Hibok-Hibok, PH, 1951 sharp edges. -​ Pinatubo, PH, 1991 3.​ PUMICE: Rich in silica. Derived -​ Kanlaon, Negros Island, PH, 2024 from Plinian eruptions like the type EFFECTS OF PYROCLASTIC FLOW: which occurred in the 1991 -​ BURN: The extreme temperatures Pinatubo eruption. of rocks and gas inside Pyroclastic 4.​ SCORIA: Poor in silica. Product of flows can burn people, houses, Strombolian eruptions of basaltic to and vegetation. andesitic volcanoes like Taal. -​ IMPACT AND BURIAL: PF can 5.​ PELE’S TEARS AND PELE’S knock down, shatter, bury, or carry HAIR: Tears are rapid cooling of away nearly all objects and basaltic lava while still in the air. structures in its path. Hair is strong winds shaped the -​ INHALATION OF HOT GAS AND lava into hair-like fragments. GASES: Burn and Impaired DANGERS FROM TEPHRA FALLS AND breathing (asphyxiation of people BALLISTIC PROJECTILES and animals.) -​ Airborne fine particles. -​ LAHARS AND FLOODING: Thick -​ Ash accumulation accumulation of loose pyroclastic -​ Automobile accidents from slippery flow deposits is easily mobilized by roads and poor visibility. stream flow to become part of lahar. PF can also melt snow and LAHARS: a mudflow consists of volcanic ice. debris with the consistency of wet concrete. It carries pyroclastic flow and one big sector of the volcano tephra falls. Process wherein of volcanic including its top. wet cement-like mixture material and -​ Debris avalanche deposits may not water flows down the slopes of the be entirely as hot as lava flow or volcano. Can travel as far as 300 km. pyroclastic flow but the abnormally Speed of 70km/hr. large volumes of volcanic materials TYPES OF LAHARS: travelling at great speed will bury 1.​ PRIMARY: occur during a volcanic areas far and wide. eruption. TRIGGERING MECHANISMS: 2.​ SECONDARY: occur after an -​ Force of rising magma makes it eruption during periods of unstable. inactivity. -​ Volcanic gases: Hot acidic TWO TYPES OF DENSITIES FOR hydrothermal system LAHARS: -​ Nearby earthquake 1.​ HIGH SEDIMENT: Looks like wet -​ Intense Rainfall concrete mixed with debris. EFFECTS OF VOLCANIC DEBRIS 2.​ LOW SEDIMENT: Flows like AVALANCHE: Debris avalanches greatly muddy water or slurry downhill. alter the pre-existing topography by HOW ARE LAHARS GENERATED?: creating deep horseshoe-shaped craters -​ Volcanic materials and by burying and destroying in their -​ Sources of Water: Rainfall, melting paths. of snow and ice cap, breaching of MITIGATING DEBRIS AVALANCHE: dams, breaching of crater lake. -​ Debris avalanche must be EFFECTS OF LAHARS: anticipated -​ Move fluid masses -​ Areas prone to debris avalanche -​ Transport large amount of debris must be identified through -​ Economical and environmental preparation of hazard maps. damage -​ Anything along the path is crushed, blown away, or buried. TAMING LAHARS: -​ Dissemination of lahar hazard information is necessary. -​ Flow sensors. -​ Alternate channels, tunnels, and concrete structures. -​ Evacuation as a preventive measure. VOLCANIC DEBRIS AVALANCHE: Landslides that occur in volcanic slopes. Debris avalanches are faster and more far-reaching than non-volcanic landslides because of the large amount of material involved. -​ Debris avalanche may involve collapse of the volcano's flank or of