10_Earthquakes_and_Active_Faulting

10_Earthquakes_and_Active_Faulting - Earthquakes and...

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Earthquakes and Faulting
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Seismos Greek for earthquake Seismicity: earthquakes Seismology: study of earthquakes Seismologists Seismometers: earthquake measurement devices
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How and why do earthquakes occur? On a fault Existing or new faults
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What is this fault thing you keep talking about? A break in the earth Blocks move separately
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Ore, minerals found on faults Mining on faults Hanging wall / Foot wall Turns out…
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Why do we need all these words anyhow? Need to describe Motion of blocks Orientation of fault Which way fault blocks moved
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More terminology (review) Hypocenter (aka focus) Epicenter Hypo: under Epi: top
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Types of Faults M10
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This animation shows the differences between the three types of faults and illustrates how they are formed. View 1 shows a normal fault, View 2 shows a reverse fault, and View 3 shows a strike-slip fault. PC version Mac version
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Is it active? Active vs Inactive Earthquakes only on active faults Unlike volcanoes, faults don’t go away
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Fault trace Where fault intersects surface Sideways motion
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Fault scarp Step at surface Vertical motion
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Blind fault
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Blind Thrust doesn’t reach surface 1994 Northridge Earthquake W5
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Faulting: Cause and Effect Stress: Force/unit area Strain: How rock changes shape Plate Tectonics Faulting
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Not all faulting causes earthquakes Aseismic slip Near surface Fault Creep At depth more ductile Still in lithosphere Creeping section of San Andreas
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How can a rock behave? Rigid: Does not deform under stress Elastic: Bends under stress Regains shape Brittle: Breaks under stress Ductile: Flows under stress Doesn’t break
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Why earthquakes happen Rock bends Apply Stress Fault ruptures Cracks form
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10_10.jpg Apply Stress No sliding More Stress Sliding Apply Stress No sliding More Stress Sliding
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10_Earthquakes_and_Active_Faulting - Earthquakes and...

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