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Guided Notes for Measuring and Locating Earthquakes

Guided Notes for Measuring and Locating Earthquakes. Section 19.3. More than 1 million earthquakes occur each year. More than 90 percent of these are not felt and cause little, if any, damage. 2) Magnitude is the measurement of the amount of energy released during an earthquake.

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Guided Notes for Measuring and Locating Earthquakes

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  1. Guided Notes for Measuring and Locating Earthquakes Section 19.3

  2. More than 1 million earthquakes occur each year. More than 90 percent of these are not felt and cause little, if any, damage.

  3. 2) Magnitude is the measurement of the amount of energy released during an earthquake.

  4. 3) Describe how the Richter Scale is used to measure earthquakes The Richter Scale is based on the size of the largest seismic waves generated by the quake. Each successive number in the scale represents an increase in wave size, or amplitude, of a factor of 10.

  5. 4) Each increase in magnitude on the Richter scale corresponds to a 32-fold increase in seismic energy.

  6. 5) The moment magnitude scale takes into account the size of the fault rupture, the amount of movement along the fault, and the rock’s stiffness. Moment magnitude values are estimated from the size of several types of seismic waves produced by an earthquake.

  7. 6) The intensity of an earthquake is the measurement of the amount of damage done to the structures involved, and is determined using the modified Mercalli scale. It uses the Roman numerals I to XII. The higher the numeral, the worse the damage done to structures.

  8. 7) Earthquake intensity depends primarily on the amplitude of the surface waves generated.

  9. 8) Another factor that determines the intensity of an earthquake is the depth of the quake’s focus. An earthquake can be classified as shallow, intermediate, or deep depending on the location of the quake’s focus. Catastrophic quakes with high intensity values are almost always shallow focus events.

  10. 9) What is epicentral distance? • Epicentral distance is the distance from a quake’s epicenter to a seismograph, which is measured by the difference in arrival times of P-waves and S-waves.

  11. 10) How many seismic stations are needed to determine an epicenter? 3

  12. 11) How is the time of occurrence of an earthquake determined? • It is determined by subtracting the travel time of P-waves and S-waves from the known arrival times of the waves.

  13. 12) Earthquake locations are not randomly distributed. The majority of the world’s earthquakes occur in relatively narrow seismic belts that separate large regions with little or no seismic activity.

  14. 13) Most earthquakes are associated with tectonic plate boundaries.

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