Earthquake Characteristics and Damage Assessment

1. Warm Up 11/1 • Which of the following is NOT a characteristic of S waves? a. They cannot be transmitted through water or air. b. They shake particles at right angles to the direction the waves travel. c. They travel more slowly than P waves. d. They temporarily change the volume of material by compression and expansion. • The trace that records an earthquake from seismic instruments is called a ____. a. richtergram c. seismogram b. seismograph d. magnitude • The distance between a seismic station and the earthquake epicenter is determined from the ____. a. measurement of the amplitude of the surface wave b. calculation of the earthquake magnitude c. arrival times of P and S waves d. intensity of the earthquake Answers: 1) d. 2) c. 3) c.

2. Destruction from Earthquakes Chapter 8, Section 3

3. Seismic Vibrations • The damage to buildings and other structures from earthquakes depends on several factors. The three factors include the intensity and duration of the vibrations, the nature of the material on which the structure is built, and the design of the structure. • Engineers have learned that unreinforced stone or brick buildings are the most serious safety threats during earthquakes • Liquefaction – loosely consolidated sediments are saturated with water and turned into a liquid that is not able to support buildings

4. Seismic Damage Liquefaction – Niigata, Japan 1964 Ground Shaking – Loma Prieta, CA 1989

5. Concept Check • When does liquefaction occur? • When loosely consolidated soils saturated with water are shaken by earthquake waves

6. Tsunamis • Tsunamis – A large water wave caused by seismic waves • A tsunami triggered by an earthquake occurs where a slab of the ocean floor is displaced vertically along a fault • A tsunami also can occur when the vibration of a quake sets an underwater landslide into motion • A tsunami can travel across the ocean at a speed of 500-950 km/hr • When the wave enters shallow coastal waters, it will slow down and begin piling on top of itself to reach a height sometimes greater than 30 meters

7. Tsunamis

8. Tsunami Travel Time to Honolulu

9. Indonesia Tsunami – 2004

10. Indonesia Tsunami – 2004

11. Concept Check • At what point does the tsunami gain the most height? • When it enters shallow waters

12. Other Dangers • The greatest damage to structures is from landslides and ground subsidence, or the sinking of the ground triggered by vibrations • The violent shaking can cause water and gas lines to rupture • Fire is also a threat, as witnessed by the large-scale destruction of San Francisco when their gas and electric lines were cut along with the water lines needed to put out the fires

13. Other Dangers Landslide – Turnnagin Heights, Alaska, 1964 Fire – San Francisco, 1906

14. Predicting Earthquakes • The goal of short-range prediction is to provide an early warning of the location and magnitude of a large earthquake • Methods for short-range predictions of earthquakes have NOT been successful • Long-range predictions give the probability of a certain magnitude earthquake occurring within 30 to 100-plus years • Seismic gap – an area along a fault where there has not been any earthquake activity for a long period of time • Scientists don’t yet understand enough about how and where earthquakes will occur to make accurate long-term predictions

15. Probability of Earthquakes Along the San Andreas Fault

16. Shaking Hazard for Southern California

17. Assignment • Read Chapter 8, Section 3 (pg. 229-232) • Do 8.3 Assessment #1-6 (pg. 232)