Real- Time Earthquake Data

EQ = Movement of E’s lithosphere that occurs when rocks in the lithosphere suddenly shift, releasing stored energy. EQs occur b/c stress forces of have exceeded the strength of rock. Stress builds when rocks along 2 sides of a fault snag and lock (friction) as stress builds – so does POTENTIAL ENERGY IN ROCKS When rocks are strained beyond limit – they break & move. (Potential  Kinetic Energy in form of seismic waves) EQs

Stress & Strain on Rocks Stress – Force that squeezes rocks together, pulls them apart, pushes in diff. directions. Stress causes strain or deformation (change in shape or volume) of rock Stress FoldsFaults Does not exceed rock strength Exceeds rock strength

Stress Folds = Bending rock layers Faults = Breaks in rock layers & movement along breaks Does not exceed rock strength Exceeds rock strength High Temps. & Pressure Low Temp. & Pressure – Near Crust

Folds Anticline = up facing fold Syncline = down ward facing fold

Faults

Types of Faults 1. Dip – Slip Motion up or down fault surface

Types of Faults 2. Strike – slip Sliding – Horizontal Movement 3. Oblique – slip dip-slip & strike slip combined

Interpretation of Tectonic History DivergentTransform Plate Boundary: Convergent NormalThrust/ReverseStrike-Slip

EQ vibrations begin at a point called a FOCUS. Vibrations travel from focus through the earth’s crust as waves. Surface directly above the focus is called the epicenter. These waves can be detected and measured on earth’s surface with a SEISMOGRAPH. EQ Vibrations

Instrument that measures & records EQ waves. Strength of EQ waves is referred to as MAGNITUDE. SEISMOGRAPHS Wave Motion: =964f1ed30b7e49ceb81bd77f444d =964f1ed30b7e49ceb81bd77f444d9230

3 Types of Seismic Waves 1. Primary Waves (P waves) 2. Secondary Waves (S waves) 3.Surface Waves Each wave originates from the FOCUS of the earthquake. Each wave travels in a different way, at different speeds, and causes different amounts of destruction.

Seismic Waves = vibrations produced by energy released during EQ Virtual EQs Seismic Waves P Waves: Primary Wave Arrives 1 st & Travels FASTER. Compress & Expand like accordion (like sound waves) Move through Solids & Liquids Least destructive

Seismic Waves S Waves – Secondary What you FEEL in an EQ Rock moves up & down or side to side (Snake-like) Arrive after P Move only through SOLIDS

Seismic Waves: Surface Waves Surface Waves develop when vibrations reach surface Slowest waves Most destructive, most damaging More P & S wave animations: Video clip:

Rating Earthquakes Earthquakes are rated in terms of MAGNITUDE or INTENSITY by different scales. 1.Moment Magnitude Scale 2.Richter Scale 3.Mercalli Scale

Uses a seismogram Rates on scale from Looks at Eqs in terms of ENERGY Each # releases 31 times more ENERGY than the # before it. Example A 6 releases 31 times more energy than a 5, and a 5 releases 31 times more energy than a 4. The energy difference between a 4 and a 6 EQ is 31 X 31 = 961 Moment Magnitude Scale

Uses a seismogram Rates on scale from Looks at Eqs in terms of the SIZE OF THE WAVES Each # has waves 10x bigger than previous # 1 – 3: Small earthquake waves – very little shaking 4 – 6: Moderate earthquakes – noticeable shaking and some damage BIG Earthquakes – Very destructive Richter Scale

Mercali Intensity Scale Measures observed RESULTS or DAMAGE of Earthquake on a 1 – 12 scale Degree of shaking and DAMAGE to structures Don’t need a seismogram Link

Deaths & Injuries Damage to buildings & structures Underground water and gas pipes break – floods & fires Landslides Tsunamis EFFECTS OF EQs

Seismic Waves are used to Study Earth’s Interior Link: on=964f1ed30b7e49ceb81bd77f444d on=964f1ed30b7e49ceb81bd77f444d9230 P and S waves are “bent” and their velocities are affected as they move through material of varying density

Latest Quakes qsww/Quakes/quakes_all.php Top Ten Lists hp

Links Virtual Earthquakes html Wave Types Triangulation & “Hearing EQs” More virtual seismograms Earthquakes outline subducting slab – Interactive Web Lab–