Earth Quakes Earth quakes Causes of earth quakes Seismic waves & measuring earth quakes Consequences of earth quakes Major earth quake zones Factors to predict earth quakes

Earth quakes An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. An aftershock is an earthquake that occurs after a previous earthquake, the main shock. Aftershocks are formed as the crust around the displaced fault plane adjusts to the effects of the main shock. Foreshocks are smaller earthquakes that may occur in the same area as a larger earthquake that follows. They are caused by minor fracturing of rocks under stress prior to the main break or main shock. Focus: location of initial slip on the fault; where the earthquake origins Epicenter: spot on Earth’s surface directly above the focus

Causes of earth quake Plate tectonics Volcanism Intraplate Earthquakes After shock & foreshock

Seismic (shaking )waves & seismology P-waves: called compressional, or push-pull waves Propagate parallel to the direction in which the wave is moving Move through solids, liquids High speed S-waves: Called shear waves Propagate the movement perpendicular the direction in which the wave is Moving slow speed as compared to p waves Can pass through liquids only P-waves: the bell analogy: waves felt by both sound

Primary or “P” Wave Secondary or “S” Wave

Surface waves Surface waves (L-waves or long waves). Up-and-down and side-to-side Slowest Most damage to structures, buildings

Measuring Earth Quakes Most common magnitude measure is Richter Magnitude, named for the renowned seismologist, Charles Richter.   Richter Scale Logarithmic numerical (NOT a physical) scale Increasing one whole unit on Richter Scale represents 10 times greater magnitude. Going up one whole unit on Richter Scale represents about a 30 times greater release of energy. Intensity Intensity refers to the amount of damage done in an earthquake Mercalli Scale is used to express damage

Seismograph Measures horizontal motion (P waves)

Seismograph Seismogram 1000 stations on earth Seismometer :amplify the waves

Calculation – difference in arrival time 03:27:15 -03:21:15 00:06:00 minutes

Locating the Epicenter of an Earthquake Part I: Finding the distance to the epicenter 00:06:00 minutes

Locating the Epicenter of an Earthquake Part I: Finding the distance to the epicenter

Locating the Epicenter of an Earthquake Part I: Finding the distance to the epicenter

Location of Epicentre

Consequences of earth quakes Ground shifts & landslides Liquefaction (unconsildated particles to water saturated ) Seiches Tsunami Fires

Zones Plate boubdries Mexico & south and central america Interplate

Short-term predictions 1. Foreshocks: usually increase in magnitude 2. Ground deformation 3. Fluctuations in water well levels 4. Changes in local radio wave characteristics 5. Anomalous animal behavior 6.Dilatancy Animals and earthquakes: On February 4, 1975 the Chinese successfully evacuated the city of Haicheng several hours before a 7.3 magnitude earthquake-- based primarily on observations of unusual animal behavior. Conventional science has never been able to adequately explain the phenomenon. Although the majority of accounts pertain to dogs and cats, there are also many stories about other types of animals in the wild, on farms, and in zoos; including horses, cows, deer, goats, possums, rats, chickens, and other birds. The behavior has been reported in many other animal species as well, including fish, reptiles, and even insects. Deep sea fish, for example, have been caught close to the surface of the ocean on numerous occasions around Japan prior to earthquakes (Tributsch, 1982). A number of theories have been proposed to explain this phenomenon, and what the precursory signals that the animals are picking up on might be. Because many animals possess auditory capacities beyond the human range, it has been suggested that some animals may be reacting to ultrasound emitted as microseisms from fracturing rock (Armstrong, 1969). Another candidate is fluctuations in the earth's magnetic field. Because some animals have a sensitivity to variations in the earth's magnetic field (usually as a means of orientation), and since variations in the magnetic field occur near the epicenters of earthquakes (Chapman and Bartels, 1940), it has been suggested that this is what the animals are picking up on.