Breaking of rock lets the fault slip breaking breaks

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Unformatted text preview: SUBDUCTION ZONE Seismic Gap along Himalayas USGS web page on October 8 2005 magnitude 7.6 in Pakistan Can earthquakes be predicted? Can earthquakes be predicted? Short Term, Not very well Short-range predictions Goal: provide warning location & magnitude within a narrow time frame within Research on precursors due breaking prior Research slip. Breaking of rock lets the fault slip Breaking Breaks called fracture zones. T α L Breaks Breaking causes volume increase (dilation) Breaking and uplift in the rocks. uplift Dilatancy causes many measurable changes Short-Term Earthquake Prediction Dilatancy of Highly Stressed Rocks 56 Investigating Earth’s Interior Earthquakes help us understand Earth’s Interior Structure. We use: Speed changes in different materials due changes rigidity, density, elasticity Reflections from layers with different properties Attenuation of Shear Waves in fluids Direction changes (Refraction) Result: 3 Major Layers of Earth 58 Shallow Components of Earth ! Seismic­wave velocities are faster in the upper mantle Velocity increases w depth, waves bend back to surface. Waves that travel via mantle arrive sooner at far destinations Wave Velocities Crust slow Mohorovičić discontinuity Upper Mantle Fast Asthenosphere Slow Lower Mantle Fast Mineralogy of Earth’s Layers The P­Wave Shadow Zone P­waves through the liquid outer core bend, leaving a low intensity shadow zone 103 to 143 degrees away from the source, here shown as the north pole HOWEVER, P­waves traveling straight through the center continue, and because speeds in the solid inner core are faster, they arrive sooner than expected if the core was all liquid. Inge Lehmann Behavior of waves through center reveal Earth’s Interior The S­Wave Shadow Zone Since Shear (S) waves cannot travel through liquids, the liquid outer core casts a larger shadow for S waves covering everything past 103 degrees away from the source. End of Earthquakes End of Earthquakes...
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