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JJC_XI. Earthquakes .pdf

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JJC_XI. Earthquakes .pdf

  1. 1. EARTHQUAKES JORIEL J. CRUZ “Earthquakes have long been feared as one of nature’s most damaging hazards. Earthquakes continue to remind us that nature still can strike without warning and, after only a few seconds, leave casualties and damage in their wake.” GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  2. 2. HOW AN EARTHQUAKE HAPPEN? 3 BASIC TYPES OF FAULTS EQUIPMENT USE TO RECORD/MEASURE EARTHQUAKES TOPICS TYPES OF QUAKE WAVES SCALE USED TO MEASURE QUAKES EARTHQUAKE PREPAREDNESS GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  3. 3. WHAT IS AN EARTHQUAKE? •Earthquakes are vibrations produced when rocks break along a fault. The term earthquake describes the sudden slip on a fault and includes the ground shaking and radiating seismic waves that is caused by the slip. Volcanic Activity, or other geologic processes, may cause stress changes in the earth that can also result in an earthquake. An earthquake is an intense shaking of Earth’s surface. The shaking is caused by movements in Earth’s outermost layer.- https://spaceplace.nasa.gov/earthquakes/en/ GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  4. 4. HOW AN EARTHQUAKE HAPPENS? GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  5. 5. Parts of Earthquakes GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  6. 6. FOCUS The point below the surface where the rock breaks and energy is released. (This is where the earthquake occurred.) GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  7. 7. LIFESTYLE BY SAWYER FAULT As soon as the rock breaks, there is movement along the broken surface causing a split in the surface. GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  8. 8. Faults a break or fracture in the crust of Earth. The earth’s crust is constantly experiencing pressure from forces within and around it. This pressure builds up over time, and eventually causes the crust to break. This becomes a fault. GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  9. 9. Classification of faults according to their relative motion and its parts: Normal Fault: hanging wall has dropped relative to the footwall. Reverse Fault: footwall has dropped relative to the hanging wall f a u l t p l a n e f a u l t p l a n e GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  10. 10. TYPE OF STRESS Compression: occurs when crustal rocks are squeezed together Can reduce the volume of rocks, can push the rocks higher up or deeper down into the crust Tension: the force that pulls rocks apart Rocks that are pulled apart by tension tend to become thinner Shearing: pushes rocks in opposite horizontal directions These rocks bend, twist, or break apart as they slide past each other. GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  11. 11. 3 BASIC TYPES OF FAULTS P Strike-Slip Reverse Normal Normal fault - when two plates are moving apart and one side of the fracture moves below the other; (caused by tension forces!) Reverse fault - when two plates collide and one side of the fracture moves on top of another; (caused by compression forces!!) Strike-slip - when two plates slide past each other. (caused by shear forces!)
  12. 12. EPICENTER The seismic waves from an earthquake are usually strongest at the epicenter.This is the point on the surface right above the focus. GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  13. 13. QUAKE OR SEISMIC WAVES Quake or Seismic waves carry energy from an earthquake away from the focus, through Earth’s interior, and across the surface Seismic waves are waves that travel through or over Earth. They are usually generated by movements of the Earth's tectonic plates (earthquakes) but may also be caused by explosions, volcanoes and landslides. They can tell us much about the Earth's structure. GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  14. 14. MAIN TYPES OF QUAKE/SEISMIC WAVES There are three basic types of seismic waves – P-waves, S- waves and surface waves. P- waves and S-waves are sometimes collectively called body waves. SURFACE WAVES BODY WAVES GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  15. 15. Move out from the earthquakes focus, the point where energy is released Travel the fastest of the 3 waves Move through solid and liquid layers of the Earth. Push and pull rock creating a back- and-forth (side to side) motion in the direction the wave is moving (longitudinal wave) 1. 2. 3. 4. P Waves also known as primary waves or pressure waves, travel at the greatest velocity through the Earth. GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  16. 16. S waves move rocks up and down, like a wave passing through a rope when you flick it. S waves travel more slowly than P waves but do more damage. S waves can only go through solid rock. 1. 2. 3. S Waves also known as secondary waves, shear waves or shaking waves, are transverse waves. S-waves cannot travel through air or water but are more destructive than P-waves because of their larger amplitudes
  17. 17. Surface waves are combined P and S waves that travel along Earth’s surface. Surface waves are the slowest seismic waves. They also do the most damage because they make the ground roll like the ocean. They are typically generated when the source of the earthquake is close to the Earth’s surface. 1. 2. 3. 4. Surface Waves Surface waves are similar in nature to water waves and travel just under the Earth’s surface. Rayleigh waves, also called ground roll, travel as ripples similar to those on the surface of water. Love waves cause horizontal shearing of the ground. They usually travel slightly faster than Rayleigh waves
  18. 18. EQUIPMENT USE TO RECORD/MEASURE EARTHQUAKES To record and measure the vibrations of seismic waves, geologists use instruments called seismographs.  Seismograph—A device that records ground movement caused by seismic waves as they move through Earth.
  19. 19. GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  20. 20. DIFFERENCE BETWEEN MAGNITUDE AND INTENSITY GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  21. 21. The Mercalli Intensity Scale was developed by the Italian volcanologist Fr. Giuseppe Mercalli in 1884 and expanded to include 12 degrees of intensity in 1902 by Adolfo Cancani. It was modified again by Harry O. Wood and Frank Neumann in 1931. It is known today as the Modified Mercalli Intensity Scale. Mercalli Scale The Mercalli Intensity Scale measures the intensity of an earthquake by observing its effect on people, the environment and the earth’s surface. Fr. Giuseppe Mercalli GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  22. 22. Mercalli Scale
  23. 23. RICHTER SCALE The Richter magnitude scale (often shortened to Richter scale) is the most common standard of measurement for earthquakes. Charles Richter (1891-1989) Rating of the size of seismic waves as measured by a seismograph. Accurate measurements for small nearby earthquakes not large distant ones. The Richter scale was developed in 1935 by American seismologist Charles Richter (1891-1989) as a way of quantifying the magnitude, or strength, of earthquakes.
  24. 24. Comparison betwen Mercalli and Richter Scale
  25. 25. WHAT TO DO BEFORE, DURIN AND AFTER AN EARTHQUAKE? Reference: PHIVOLCS GSE 415 EARTH/ENVIRONMENTAL SCIENCE
  26. 26. BEFORE EARTHQUAKE WHAT TO DO BEFORE AN EARTHQUAKE? KNOW THE HAZARDS: Familiarize yourself with earthquake hazards in your area. KNOW THE EVACUATION AREA: Check the nearest route going to identified area. PREPARE EMERGENCY SUPPLY KIT: Make it accesible at all times PREPARE YOUR HOUSE OR WORKPLACE Learn to USE the first aid kit , fire extinguishers, alarms, switching off waterlines, gas tanks, and circuit breakers. PARTICIPATE DURING EARTHQUAKE DRILLS. Regularly practice evacuation procedure.
  27. 27. DURING EARTHQUAKE WHAT TO DO DURING AN EARTHQUAKE? DURING SHAKING: DROP, COVER and HOLD STAY CALM and ALERT: Watch for the falling objects, glass windows, shelves, cabinets and other heavy objects that may cause injury. IF OUTSIDE, MOVE to an open area. IF NEAR SHORE, Move quickly to a higher grounds. Move away from steep slopes. STOP if inside a MOVING VEHICLE. Do not cross bridges, overpass or fly over.
  28. 28. AFTER EARTHQUAKE WHAT TO DO AFTER AN EARTHQUAKE? EVACUATE. As soon as the shaking stops, take the fastest and safest way out. EXPECT AFTERSHOCKS Put out small fires using extinguisher. BE UPDATED: Monitor the situation from the radio, tv and others. CHECK YOURSELF AND OTHERS FOR INJURIES

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