1 Earthquakes

2 Great Quake of 1906 San Francisco, CaliforniaSan Francisco City Hall San Francisco, California Around 5:12 am on April 18, 1906 Lasted 40 seconds then paused for 10 seconds and was followed by 25 seconds of a stronger tremor Could be felt from southern Oregon to south of Los Angeles inward to Nevada Estimated at between 7.8 and 8.3 magnitude, resulted from the North American and Pacific tectonic plates moving past each other by more than 15 feet

3 Damage Areas that were hit the hardest were sediment-filled land and where land was reclaimed from the San Francisco Bay Solid bedrock areas sustained less damage 1906 Earthquake Sacramento Street with fire approaching

4 Effects 500 city blocks destroyed – 28,000 buildings700-3,000 people died – estimates vary Over 250,000 people homeless Quake destroyed water and gas lines Fires erupted all over the city due to broken gas lines for 3 days Most of the city burned due to not having water lines to put out the fires About ¾ of the city was destroyed by fire

5 Effects Telephones, railways, and streets all are not working or limited Refugee camps were built all over the city Damage estimated at $ million in 1906 dollars equal to $4.8 – 10 billion today

6 Why did this happen? Proximity to a major faultPoorly built structures – there were no codes for building in earthquake areas at that time Inadequate fire protection system

7 Aftermath Quickly rebuilt structuresDid not improve building codes – some think structures were more vulnerable after 1906 The city's business and political leaders downplayed the earthquake’s impact to make outside investors’ feel better and relayed the disaster as a fire not an earthquake. San Francisco had actually been destroyed by 6 fires prior to 1906 so this made sense.

8 Aftermath Insurance companies were only responsible for paying money to people who’s building were destroyed by the earthquake not the fire – determining this was difficult – caused a change in insurance policies and the closing of companies One of the first natural disasters to be captured on film – Visit the Virtual Museum for more images.

9 Loma Prieta EarthquakeSome thought the earthquake that hit on October 17, 1989 was “The Big One”, but that’s not likely Measured at 7.1 and was the strongest quake since 1906 63 people killed – most from the collapse of the Cypress Freeway San Francisco’s Marina District and year old houses in Santa Cruz were hit the hardest

10 The Earthquake Series Occurred just before the third game of the World Series between the San Francisco Giants and the Oakland A’s San Francisco’s Candlestick Park has some damage Goodyear Blimp caught aerial footage Series was suspended for 10 days World Series Footage When Disaster Strikes

11 Earthquakes An EARTHQUAKE is a vibration of Earth caused by a release of built up energy that has been stored along a fault Rocks suddenly slide past each other releasing energy to shake the ground – the ground bends for so long before it can’t take it anymore and breaks FAULTS are breaks in the rock where slabs can move Usually earthquakes last for seconds to a few minutes

12 3 Different Types of FaultsNormal Fault – rock slabs pull apart and one slab moves up while the other moves down along a fault Reverse Fault – rock slabs are pushed together and one slab is pushed under the other along a fault Strike-Slip Fault –rock slabs move horizontally past each other – twist and tears rock layers San Andreas Fault is an example of this

13 Where They Occur EPICENTER - The point directly above the focusFOCUS - The point at which an earthquake begins These are below the surface Can occur anywhere from 3 – 420 miles below the surface Most of the worst ones occur within 35 miles of the surface

14 Waves When an earthquake occurs seismic waves are sent out in all directions Waves carry seismic energy, which shakes objects on the surface 4 main types of waves P Waves S Waves L Waves R Waves – Rayleigh waves move in an elliptical orbit Wave Animation

15 P Waves Primary or Compression FastestCan travel through mantle and core 1st movements people feel Waves move out in all directions from the focus. Push and pull rocks. P Wave Animation

16 S Waves Secondary Not as fast as P Can only travel through solidsProduces side to side and up and down action Moves rocks at right angles to the movement of the wave S Wave Animation

17 L Waves Surface or Long Slowest Rocks move up and down.Caused by P and S waves Like waves on the ocean bouncing up and down Most destructive  Discovered by Augustus Love – you don’t need to write this one Seismic Waves from 2002 earthquake

18 Now let's create an earthquake!

19 How Do We Measure Earthquakes?2 ways to measure: Mercalli Scale and Richter Scale Mercalli Scale – similar to the Did You Feel It? Scale Measures the amount of damage that occurs Gives a Roman numeral from I-XII Subjective – based on opinion Named after Guiseppe Mercalli an Italian volcanologist It doesn’t match up perfectly with the Richter Scale

20 How Do We Measure Earthquakes?Richter Scale Measures the magnitude or strength of an earthquake Gives it a number from 1-10 Minor earthquakes are 4 or less Major earthquakes are 6 or higher Each increase of 1.0 on the Richter Scale represents 30 more times the energy Named for American seismologist Charles Richter

21 Seismographs Seismograph – an instrument used to record seismic waves2 main types Spring Pendulum Ancient seismograph from the Han Dynasty

22 How are tsunamis examples of rapid surface changes?Tsunami – a seismic sea wave that forms when an earthquake occurs on the ocean floor Actually means – harbor wave in Japanese It has nothing to do with tides – NOT controlled by the gravity of the moon Can also be triggered by landslides or volcanic eruptions

23 How does a tsunami form in the ocean?Step 1: energy causes the seafloor to move up and down to create a wave Only about 1 m (3 ft) high – go unnoticed out in the middle of the ocean Step 2: wave gets higher Distance between two crests or troughs can be 60 mi. Travels close to 500 mph Step 3: wave slows down as it nears the shore due to friction As water gets shallower, wave height increase Step 4: water recedes from shore, then wall of water rushes towards shore Tsunami Animation

24 How they occur? Massive slabs of rock are forced into the mantlePlates lock up when they collide building up energy Energy is released – raises and lowers ocean floor – starts a tsunami

25 Why are tsunamis so dangerous?Gigantic walls of water that occur around the Pacific Plate (Ring of Fire) Only occur about once a year Cause massive destruction where they begin and everything in their path Can travel thousands of miles from origin More than 1 wave will hit

26 How can we predict tsunamis?They can be predicted Tsunami Warning System 2 in the US Hawaii Alaska Use satellites to gather seismic data Tsunami sensors measure ocean level changes or less than a millimeter Warnings are sent out for earthquakes that are 6.5 or higher Animal Behavior

27 What can you do? Know what to do in case of a tsunamiDon’t go near the water Go to higher ground If there is no higher ground – go inland As a last resort, climb a tall, strong tree and hold on Wait for the all clear signal because another wave could come 5 minutes to an hour later Look for signs like this one to know if you are in an area that could get hit with a tsunami

28 Recent Tsunamis December 26, 2004 – earlier in the morning a 9.0 earthquake occurred off the coast of Sumatra, Indonesia Tsunami hits Sri Lanka, Thailand, India, Indonesia, and parts of Africa Killed over 250,000 people in areas affected 2004 Tsunami animation Map showing how long it took for the wave to hit areas Before and After Photos 2004 Video of the wave hitting – Disclaimer – you will see people who got washed away by the wave As of 2012 Indian Ocean now has at least 3 buoys in their tsunami warning system

29 The most recent tsunamiMarch 11, 2011 at 2:46 Japanese time – 9.0 earthquake hits off of the coast of Japan that starts a tsunami 100 foot waves hit towns of Japan and a nuclear plant traveling as far as 6 miles inland Several waves hit Japan March 12, 2011 – 6.2 aftershock hits Japan over night, 6.3 aftershock just before 6 am Cooling systems fail in several of the nuclear reactors resulting in meltdowns Many people exposed to radiation – evacuate areas

30 Japan 2011 As of 2014, 28,000 people are confirmed dead or missingEstimates of over $310 billion in damages Over 125,000 houses washed away Largest earthquake to hit Japan since 1900 and fourth largest in the world since 1935 Two days prior had a 7.2 earthquake that caused little damage Japan did warn people before the tsunami and have since upgraded their tsunami warning system Japanese Tsunami Video Japanese Before/After Pictures

31 Amazing Facts The earthquake shifted Earth on its axis of rotation by redistributing mass, like putting a dent in a wobbling top. It shortened the length of day by about a microsecond. More than 1,000 aftershocks have hit Japan since the earthquake, the largest a magnitude 7.9. Jolt moved Japan's main island of Honshu eastward by 8 ft. The Pacific Plate slid westward near the epicenter by 79 feet. In Antarctica, the seismic waves from the earthquake sped up the Whillans Ice Stream, jolting it by about 1.5 feet. Broke icebergs off the Sulzberger Ice Shelf in Antarctica. Killed more than 110,000 nesting seabirds at the Midway Atoll National Wildlife Refuge.

32 Test your knowledge - Tsunami Quiz