GEOL 101 1nd Edition Lecture 29 Outline of Last Lecture I. Locating earthquakesII. Measuring earthquakesIII. Earthquake HazardsIV. Earthquake DestructionOutline of Current Lecture I. Secondary HazardsII. Predicting EarthquakesIII. Preparing EarthquakesIV. Earth’s Interior V. Physical LayersVI. Discovering Earth’s InteriorCurrent LectureSecondary Hazards-Fire- Often times Earthquakes will break cities’ water lines, allowing fires to spread quickly- Such was the case during the 1906 San Francisco earthquakeo April 18, 1906 estimated 7.9 MMS earthquake sourced along the San Andreas Faulto Despite being at 7.9 (Mw) the greatest loss of the life and property was due to the fire-Disease- With damaged infrastructure, thousands of people displaced and homeless, living in crowded, unsanitary refugee camps, disease outbreaks often follow earthquakes- Especially prevalent in developing nationso January 12, 2010 – The 7.0 Mw magnitude Haiti earthquake not only crippled thecity of Port-au-Prince but within 9 months there were over 2300 cases of Choleraand nearly 200 confirmed deaths from the diseaseThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Primary source of contracting the disease is unsafe drinking water-Nuclear hazards- One of the most tragic effects of the 9.0 Mw Japan earthquake is the continuing disaster at the Fukushima nuclear power plant- While the earthquake itself did not significantly damage the nuclear plant, the 46 ft high tsunami wave did (the plant was protected by a seawall that would withstand a more typical 19 ft wave)o The cooling system in the past was so damaged, in addition to loss of power in region, reactors began to overheat with the radioactive decayo Partial core meltdown of reactors 1, 2 and 3, with fires and explosions in 1-4-The main concerns are radioactive caesium, iodine, and plutonium which - At the peak of radiation release, the core was releasing 400m Sv/h, which is roughly twice what the Chernobyl workers were dosed with o The Chernobyl core explosion released over 300,000o So far only about 1/10 of the amount of radiation released from Chernobyl has been released from Fukushima- While not as catastrophic as Chernobyl, Fukushima is still rated as a level 7 “major accident”- Major long-term health risks (cancer) are expected in the immediate areaPredicting Earthquakes-We do not yet have accurate short-term methods of predicting when and where an earthquakewill strike- There are some “precursors” such aso Foreshockso Bizarre animal behavioro Changes in the ground watero Release of radon gas or methane from the ground- Some of these have been useful in predicting past earthquakes, however they do not always occur.-We do have good methods for making earthquake forecasts – long-term likelihood of where, when, and how big an earthquake might be (hazard assessments).-We can study faults and earthquake history in an area to predict how often earthquakes happen in that area-Data sources:o Recent earthquakes – data from seismometerso Ancient earthquakes – data from the roc record or “pale seismology” -Earthquake forecasts are given as probabilities-Large faults (such as the San Andreas) don’t continuously move, but rather move in segments- There are often times bends along the fault o This is where stress gets concentrated- An area along the fault that has not had any earthquakes in a long time is called a seismic gapo This is where the fault has been “locked” for quite sometimeo There is presumably a lot of strain building up within the seismic gap, making it the most likely place to rapture-We can also use long-term studies to establish a recurrence internal– the average time between earthquakes of a specific size along a fault- Recurrence internals are also calculated as probabilities - i.e. “There is a 20% chance that an earthquake of 7.0 or higher will occur in the next 10 years”Preparing Earthquakes-There are a number of ways to prevent loss of life and property for those living in earthquake-prone areas- Engineering earthquake-resistant structures - Emergency response protocol - Tsunami warning systems - Public education-Most earthquake-related deaths occur when buildings collapse-In California, buildings are designed to have a certain amount of “give” or ductility so that whenbuildings sway up-down, left-right, back-front, the material can bend, instead of break- Brick buildings are not resistant beneath the brick and mortar are rigid materials- Flexible steel allows for more sway-This earthquake-resistance is still limited physical and economic factors to how strong we can make construction material-Emergency response is critical during an earthquake – if resource personnel know the hardest place hits, they can allocate resources to save more lives- Southern California has established a system called TriNet - When an earthquake hits, it shows them the intensity of ground shaking across the area,and thus the areas to send first response teams.-Tsunamis are a major hazard along coastal areas, particularly along the Pacific Ocean- The Pacific Tsunami Warning Center in Hawaii tracks earthquakes around the Pacific rim and calculates arrival times of oncoming tsunami waves- This gives Hawaiian coastal communities enough time to evacuate if a tsunami is coming Earth’s Interior -Prior to the turn of the 20th century, very little was known about the interior of the earth-The deepest well that has been drilled is 7.5 miles deep- While impressive for a well, it is still less than 1% of the entire distance to the core-It has been through the study of Earthquake waves that scientists have been able to understand what’s going on beneath us. -If the earth were a perfectly homogenous material, we would observe seismic waves travel through at constant speeds and in straight lines-This however, is not the case:- It is observed that seismic waves travel faster with depth, which is consistent with materials under increasing pressure- This causes the seismic waves to refract (bend) instead of traveling in a straight line- Some lines are also reflected back to the surface at certain depths-The compositional layering of the planet most likely occurred early during formation, when heavier elements sank to the center, and lighter elements floated to the