Chapter 8 Earthquakes 8.3 Destruction from EQ 8.4 Earth’s Composition

8.3 Destruction from EQ The damage to buildings etc. form seismic waves depends on: – Intensity and duration of vibrations – Nature of material on which structure is built – Design of structure itself

Building Design & Liquefaction Design of structures affects damage level – More flexible (wood, steel)  less damage – Less flexible (brick, stone)  more damage Liquefaction: soils & other loose material saturate with water and turn to liquid – Unable to support buildings – Structures (bridges/buildings) may settle & collapse – Underground storage tanks & sewer lines may float toward surface. – Liquefaction in Japan Liquefaction in Japan – Extreme Soil Liquefaction Extreme Soil Liquefaction

Tsunamis Japan March 2011 Tsunami Photos Nat. Geo. Japan March 2011 Tsunami Photos Nat. Geo. Tsunami Animation Cause: series of ocean waves generated by sudden displacements in the sea floor, landslides, or volcanic activity. In the deep ocean, the tsunami wave may only be a few inches high. The tsunami wave may come gently ashore or may increase in height to become a fast moving wall of turbulent water several meters high. Tsunamis 101

‘Till the landslide brought me down… Landslides – Greatest damage to structures – Violent shaking causes soil/rock on slopes to fail – Gas/water pipelines can become ruptured – Christchurch Rockfall Impacts Christchurch Rockfall Impacts Fires – Electrical and gas lines damaged – Water lines are also damaged which means fires can’t be stopped

Predicting Earthquakes Short-Range Predictions – Early warnings regarding location and magnitude – Monitor precursors— Uplift Strain in rocks near faults Water level and pressures in wells – Typically not successful Long-Range Forecasts – Measure probability relying on historical data & patterns – Difficult to accurately predict exactly when and precise magnitude of future earthquakes Are animals the key to prediciting EQ?!

8.4 Earth’s Layered Structure Earth’s interior composed of 3 major zones (defined by chemical composition): – Crust – Mantle – Core Because layers have different compositions; seismic waves travel at different speeds in each layer

The Earth is made of multiple layers: CRUST topmost layer of solid and cool rock  the “plates” Earth’s Interior- pages

2. ___________ MANTLE located below the crust (more _______) DENSE ______ of earth’s total volume 80 %

3. CORE mostly made of _________________ very hot 2 layers: 1) OUTER CORE 2)INNER CORE iron and nickel

b. Inner core (________ metal)- very high ____________ so atoms are forced together despite the ______. SOLID PRESSURE HEAT a. Outer core (________ metal)- even though it’s above the boiling point they do not boil due to high pressure (no gases) LIQUID Layers of the Earth (NASA)

S waves: can’t travel through core (outer/liquid)  transverse & can’t travel through liquid P waves: can travel through core but deflected  change in type of matter Evidence of Earth’s Internal Structure Layers of Earth Mr Lee

Seismic waves are used to determine Earth’s interior structure…

Japan EQ Tsunami 2 Years Later Photos Before/After