6 - EARTHQUAKE AND EARTHQUAKE HAZARDS.pdf

EARTHQUAKE AND EARTHQUAKE HAZARD ○ A quake magnitude is determined by EARTHQUAKE measuring the amplitude of the largest Shakin...

EARTHQUAKE AND EARTHQUAKE HAZARD ○ A quake magnitude is determined by EARTHQUAKE measuring the amplitude of the largest Shaking of the ground caused by sudden slippage wave recorded on the seismogram. of rock masses below or at the surface of the earth. ○ The larger the amplitude, the greater is the It is a wave-like movement of the earth’s surface. displacement of the recording pen and the An earthquake may be classified as either tectonic greater the earthquake. or volcanic. SEISMICITY – intensity, frequency, and distribution DEEP EARTHQUAKE – mild & may be felt as tremors of earthquakes in a specific area. SHALLOW EARTHQUAKE – A very severe earthquake SEISMIC WAVES – elastic energy that travels as is usually associated with shocks called foreshocks waves through the Earth's crust at speeds of several and aftershocks. miles per second and is propagated or transmitted FORESHOCKS – series of tremors that occur before outward radially from the focus of an earthquake. the main earthquake. SEISMOGRAPH – a very sensitive instrument that AFTERSHOCKS – weaker earthquakes that follow the can detect, measure and record ground vibrations main shocks and can cause further damage to and their intensities during an earthquake. weakened buildings. SEISMOGRAMS – record from seismograph; Be aware that some earthquakes are actually indicates the plot of time vs. intensity of motion foreshocks, and a stronger earthquake might occur. SEISMOLOGY – branch of geology that studies ACTIVE FAULT – moved once or more times in the earthquakes and seismic waves that move through past 10,000 years & likely to move in the future and around the earth as well as their effects. AMPLITUDE – size of the wiggles on an earthquake SEISMOLOGIST – studies seismology recording. BODY WAVES EPICENTER – the point on the Earth's surface Seismic vibrations that move through the Earth’s vertically above the focus of an earthquake interior FAULT – a crack in the Earth’s crust along which the PRIMARY WAVES (LONGITUDINAL) – push-pull rocks slide. waves, waves move back and forth in the direction ○ Are found at the edges of the plates where in which the wave is travelling. the crust is moving in different directions. ○ Change both volume and shape of material FOCUS/HYPOCENTER – the point below the Earth’s in which they pass. surface where an earthquake rupture begins ○ Affect and can pass through solids, liquids, ○ located inside the Earth where the rock and gases. breaks off and pressure is released. ○ Longitudinal Waves - wave motion FOCAL DEPTH OF AN EARTHQUAKE – the depth of the (amplitude) is parallel to direction of travel hypocenter below the Earth's surface. SECONDARY WAVES (TRANSVERSE) – vibrations MAGNITUDE – a number that categorizes the occurring at right angles to direction of wave amount of energy released during an earthquake. propagation. ○ written in Hindu Arabic numbers ○ They are shake-waves (shear waves), INTENSITY – severity of an earthquake in terms of its vibrating side-to-side. effects on the earth's surface and on humans and ○ They are not as fast as P-waves and result their structures. in changing only shape of material they ○ written in roman numeral numbers travel through. ○ most commonly used in the United States ○ Affect and can pass through only solid are the Modified Mercalli scale and the materials (only solids offer resistance to Rossi-Forel scale change in shape). MAINSHOCK – largest, main earthquake ○ Transverse Waves - wave motion is PLATE TECTONICS – science of the process where perpendicular to direction of travel rigid plates move across hot molten material. SURFACE ○ Helps explain the formation of mountains Seismic vibrations that move along the outer layer and the distribution of earthquakes and of the Earth's surface. volcanoes Have both vertical and horizontal components of RICHTER SCALE – measures the magnitude of motion; horizontal components cause the most seismic energy released during an earthquake damage.  LOVE WAVES – horizontal vibration, perpendicular to WHAT TO DO DURING AN EARTHQUAKE? travel. RAYLEIGH WAVES – rolling / orbital ground vibration Direct family members to stay inside a structurally like ocean waves. sound building. Advise them to protect their body from falling debris EARTHQUAKE HAZARDS by bracing themselves in a doorway or by getting GROUND RUPTURE under a sturdy desk or table and doing the DUCK, Deformation on the ground that marks the COVER and HOLD. intersection of the fault with the earth’s surface When inside a vehicle, pull to the side of the road Effects: fissuring, displacement of the ground due to and stop. Do not attempt to cross bridges or the movement of fault overpasses which may have been damaged. GROUND SHAKING Direct family members to move to an open area Disruptive up, down, and sideways vibration of the when they are outside a building or any structure. ground during an earthquake Stay away from power lines, posts, walls, and other Effects: damage or collapse of structure, may structures that may fall or collapse. Stay away from consequently cause hazards like liquefaction and buildings with large glass panes. landslide Move away from steep escarpments which may be LIQUEFACTION affected by landslides particularly if they are on a Phenomenon wherein sediments, especially near mountain or near steep hill slopes. bodies of water, behave like liquid similar to a WHAT TO DO AFTER AN EARTHQUAKE? quicksand Effects: sinking / tilting of structure above it, Advise family members to take the fastest and sandboil, fissuring safest way out if caught in a old or weak classroom EARTHQUAKE-INDUCED LANDSLIDE building. Down slope movement of rocks, soil, and other They should be advised to: Get out calmly and in an debris commonly triggered by strong shaking orderly manner. Not to rush or push one another. Effects: erosion, burial and blockage of roads and Not to use elevators, but instead use the stairs; rivers Check themselves for cuts and for injuries and TSUNAMI approach the nearest older family member or Series of waves caused commonly by an neighbor for assistance. earthquake under the sea Check the surroundings of the house Effects: flooding, coastal erosion, drowning of Call the proper authority to clean up chemical spills, people, and damage to properties toxic, and flammable materials since this is hazardous to untrained people. WHAT TO DO BEFORE AN EARTHQUAKE? Check for fire and if any, have it controlled. Check for the presence of other potential sources of hazard due to secondary effect of earthquakes like steep hill slopes, hanging heavy objects, dams, storage tanks, falling debris, and fire. Strap heavy furniture/cabinets inside the rooms to the wall to prevent sliding or toppling Store breakable items, harmful chemicals and flammable materials inside the rooms in the lowermost shelves and secure firmly. Install latches on drawers and cabinets. Check rooms for hanging or unstable objects that may fall on during the earthquake. Advise kids not to use the elevator during and after an earthquake. Structure or power failure may lead you to get stranded in the elevator. Identify strong parts of the building like door jambs, sturdy tables where the family members can take refuge duringan earthquake.