G10-Q1-SCIENCE-02

• What are earthquakes?

  Earthquakes are the vibrations of Earth due to a sudden and rapid release of energy.
• What causes the shaking of the ground during an earthquake?

  The shaking of the ground is due to rapid and sudden movement of the Earth's crust.
• Which part of the Philippines has no record of earthquakes?

  Palawan has no record of earthquakes.
• Why does Palawan have no record of earthquakes?

  Palawan is not technically part of the Philippines and only drifted nearby from another country.
• What is a fault in the context of earthquakes?

  • A fracture in the rocks that make up the earth’s crust.
  • Formed due to internal stress.
  • Locked due to confining pressure.
  • Not to be confused with joints, which have no displacement.
• What is the epicenter of an earthquake?

  The epicenter is the point on the surface of the Earth directly above the focus.
• What does the term "focus" or "hypocenter" refer to in an earthquake?

  The focus is the point within the earth where an earthquake rupture starts.
• What are seismic waves?

  Seismic waves are waves that transmit the energy released by an earthquake.
• What are the destructive natural forces caused by earthquakes?

  • Shaking of ground
  • Liquefaction of soil
  • Destruction of structures
  • Fires
• Who proposed the elastic rebound theory?

  Harry Fielding Reid proposed the elastic rebound theory.
• What did Harry Fielding Reid conclude about the 1906 San Francisco Earthquake?

  He concluded that the earthquake was caused by elastic stress in the Earth’s crust.
• What is the elastic rebound theory?

  • The crust or rocks behave elastically.
  • Gradual accumulation and release of stress and strain in the crust.
• What are the steps of elastic rebound?

  1. Crust remains in original position.
  2. Strain and elastic energy build up.
  3. Differential stress overcomes frictional resistance, causing slippage.
  4. Earthquake stops, and plates return to original position, but landmarks are displaced.
• What are mechanical waves and their categories?

  • Mechanical waves require a medium to transfer energy.
  • Categories:
  • Longitudinal Waves: vibrations parallel to wave direction.
  • Transverse Waves: vibrations perpendicular to wave direction.
• What are electromagnetic waves?

  • Waves that do not need a medium to transfer energy.
  • Can move in a vacuum.
• What are body waves in the context of seismic waves?

  Body waves are waves that move through the Earth.
• What are P Waves and their characteristics?

  P Waves are the fastest type of wave and can move through solid, liquid, and gas phases of matter.
• What are S Waves and their characteristics?

  S Waves are detected after P Waves and can only move through solids.
• What are surface waves and their characteristics?

  • Surface waves move only through the surface.
  • Generally slower than body waves.
  • Easily distinguishable in a seismogram.
  • Categories:
  • Love Waves: side to side motion, slower than S waves.
  • Rayleigh Waves: rolling motion, slowest waves.
• What are seismographs?

  Seismographs are tools used to record the vibrations of an earthquake.
• How do seismographs record earthquake vibrations?

  They record the vibrations on a sheet called a seismograph.
• In what order do seismic waves arrive?

  P waves arrive first, followed by S waves, then surface waves.
• What does the amplitude on a seismograph indicate?

  The amplitude corresponds to the intensity that the ground shakes or vibrates during the earthquake.
• What is seismology?

  • Seismology is the study of earthquakes and related phenomena.
  • It involves studying seismic waves and their effects.
• What is the purpose of a seismometer or seismograph?

  To record an earthquake’s characteristics.
• How does a seismogram work?

  Seismograms are placed deep in the Earth and use springs to record information based on inertia.
• What information is recorded on a seismogram?

  The duration and amplitude of the shaking are recorded.
• What does the amplitude on a seismogram indicate?

  The amplitude indicates how long the shaking maintains.
• What does the time interval between P waves and S waves indicate?

  The time interval indicates the distance to the epicenter.
• What is the Modified Mercalli Scale used for?

  The Modified Mercalli Scale is used to scale the intensity of earthquakes.
• Who was the Modified Mercalli Scale named after?

  It was named after Giuseppe Mercalli.
• How many levels of severity does the Modified Mercalli Scale have now?

  The Modified Mercalli Scale now has 12 levels of severity.
• What is magnitude in the context of earthquakes?

  Magnitude is the scientific and objective way of measuring the shaking of an earthquake.
• Who developed the Richter Scale?

  Charles Richter developed the Richter Scale in 1935.
• What does the Richter Scale quantify?

  The Richter Scale quantifies the actual ground motion of an earthquake.
• How does the Richter Scale work?

  The scale is based on the amplitude of the largest seismic wave.
• What does a 10-fold wave amplitude increase on the Richter Scale mean?

  Each magnitude is 10 times greater in strength than the last.
• What are the steps in finding the Richter magnitude?

  1. Find the time interval or distance to the epicenter.
  2. Measure the height of the largest amplitude.
  3. Plot the time interval and amplitude to find the Richter Magnitude.
• What is moment magnitude?

  Moment magnitude is the measure of magnitude based on the seismic moment.
• When is moment magnitude ideally used?

  It is ideal to use for larger earthquakes (greater than 5 on the Richter Scale).