Uplift: Faults and Earthquakes Vibrations in rocks caused by a release of energy when rocks break at fault planes or plate boundaries Ex. San Andreas Fault

1. Three types of stress Tensional: at diverging boundaries: Normal faults Compressional: converging boundaries: Reverse faults Shear: transform boundaries: strike slip faults

2. Why rocks move Plate movements ->stress_-> strain in rocks. This stored “elastic strain energy” makes rocks deformed When rocks cannot handle stress any more, they rupture releasing energy as seismic waves: EARTHQUAKE!!! Elastic Rebound: rocks snap back to original shape but are OFFSET (displaced) Lab: Trabuco fault lab

What type of fault?

Normal: Hanging wall slides down Tensional stress

What type of fault?

What type of fault? Reverse: Hanging wall slides up: Compressional stress

What type of fault?

What type of fault? Transform fault: Right or Left lateral??

3. epicenter, focus of e.q.

C. Released energy travels in the form of Seismic waves

4. Properties of waves P – primary waves: 1st to arrive; ~7 km /sec.; compressional; travels through air, water, solids S – secondary: 2nd to arrive; shear or right angles, ~3-4 km/sec.; solids only L – Love and Rayleigh waves: slowest; last to arrive; most destructive

P - push pull waves P - push pull waves                                                                                                         

S - shake or shear waves S - shake or shear waves                                                                                                        

L - surface waves: surface waves                                                                                                                               

5. Recording an earthquake’s time, Duration, Magnitude, Location, Energy Seismometer: Drum and seismogram paper Seismogram: graph of waves shows time of ground shakings: 1.It gives time quake occurred 2. Duration Lag time- gives 3. location (with TT graph) and 4. magnitude (with Richter scale) Amplitude- gives magnitude

Time: when it occurred:

Duration Measure from the beginning of P-wave to end of S-wave

Lag time =S-P; and Amplitude Used to find magnitude, energy Used to find epicenter – location Amplitude used to find magnitude

Finding Magnitude: Use lag time and Richter’s Scale See Richter’s scale worksheet Each number is exponentially 30 (32) times greater than the previous number Ex.How much stronger is Mag. 4 than mag.1? Ans.= 303 = 27,000x

Finding the epicenter 1. Use a Time travel graph and Lag time to get distance to epicenter from one city

Travel time graph S-P = Lagtime is measured on vertical axis Horizontal axis gives distance to epicenter for each station

Graph shows P, S, L times

Finding epicenter… continued 2. Get distances from three(3) cities. 3. Distances = radii from cities Use scale of map to measure distances and draw three circles 4. Where radii intersect is the epicenter

Finding the epicenter

S and P shadow Zones