170 likes | 502 Views
Earthquake Safety. C5S4. Earthquake Risk. How do geologists determine earthquake risk?. Geologists can determine earthquake risk by locating where faults are active, where past earthquakes have occurred, and where the most damage was caused. Plate boundaries .
E N D
Earthquake Safety C5S4
How do geologists determine earthquake risk? • Geologists can determine earthquake risk by locating where faults are active, where past earthquakes have occurred, and where the most damage was caused.
Plate boundaries • If you look at page 197 in your textbook Fig. 18 shows that California, Washington, and Alaska are at highest risk of am earthquake. • Plates meet along the Pacific coast, causing many active faults. • For example: San Andreas Fault, and the subduction zone of Juan de Fuca and the Pacific plate.
Mapping Earthquake Intensity • Geologists use modified Mercalli scale data to map the intensity of an earthquake. look at pg 198 in the textbook
What kind of damage does earthquakes cause? • Causes of earthquake damage include: shaking, liquefaction, aftershocks, and tsunamis.
Shaking • Shaking can trigger Avalanches or mudslides. • The type of soil determines where and how much the ground shakes. Loose soil shakes more violently than solid rock.
Liquefaction • Occurs when an earthquake’s violent shaking suddenly turns loose, soft soil into liquid mud. • Liquefaction is likely where the soil is full of moisture
AfterShocks Is an earthquake that occurs after a larger earthquake in the same area. Sometimes buildings weakened by an earthquake collapse during an earthquake.
Tsunamis The water displaced by the earthquake may form a large wave. A tsunami spreads out from an earthquake’s epicenter and speeds across the ocean. In the open ocean, the height of the wave is low. As a tsunami approaches shallow water, the wave grows into a mountain of water.
What can be done to increase earthquake safety and reduce earthquake damage? • The best way to protect yourself is to: • DROP! COVER! HOLD! • To reduce earthquake damage, new buildings must be made stronger and more flexible. Older buildings may be modified so as to withstand stronger quakes.
Base-isolated Buildings • Rests on shock absorbing rubber pads or springs. Like suspensions of a car, the pads and springs smooth out a bumpy ride. During a quake, the building moves gently back and forth without any violent shaking. http://www.youtube.com/watch?v=-N_Q6Q-3o7M#t=63