UNIT 11 SEISMIC WAVES & (Ch. 9) Study Guide (Revised 7/18) UNIT 11 HOMEWORK worth 10 points VIDEO HIT HOMEWORK – write two paragraphs with three sentences each

(PHYSICAL GEOLOGY 1303) (Revised 7//18) UNIT 11 Video Hits For Unit 11 Video Hits, go to the “DMC HOME” website; in Search box –type “Kramer”, select “Faculty Listing”; click on Walter Vernon Kramer, click on Website“, scroll down and click GEOL 1303; then select “Video Hit Link Number 11”, and click on icon, watch video and see how scary earthquakes can be!. [IF NONE OF THE WEB SITES COME UP, YOUR COMPUTER PROBABLY NEEDS TO BE REBOOTED (RESTARTED)

Earthquakes - We saw that most of the world’s most destructive earthquakes occurred along the Pacific Rim - Most of these earthquakes occurred along major plate tectonic zones

- Every year, some parts of will experience an - We shared our earthquake experiences - Earthquake: a shaking or vibration of the Earth caused by the sudden release of energy - Saw a video of an earthquake at a Microsoft office - On March 24, 1997 – a 3.8 earthquake with its at Alice TX was felt in Corpus Christi. - Another Alice 4.0 earthquake occurred on April 24, 2010 - Gave examples of seismic activity associated with the movies Jurassic Park and Star Wars - Even the sun has “quakes”

Destructive Forces - Earthquakes are among the most destructive geologic forces on Earth. - In less than two minutes, an earthquake can kill more than 200,000 people and level hundreds of bridges and thousands of buildings for miles around Tsunami - Japanese word for harbor wave - Some earthquakes can generate tsunamis - These can be highly destructive tidal waves as seen in Japan (2011) and Indonesia (2004) 1

- Most tsunamis are created by an undersea moving tectonic plate - Tsunami waves can move at speeds of 500 mph in the deep oceans

Earthquake Model - The model most used to explain most earthquakes is the elastic-rebound theory. - Elastic-rebound theory: (H. F. Reid – 1906) The sudden release of “stored elastic energy” will create earthquake “waves of energy”. - A good example of this theory is the bending and the breaking of a pencil.

Earthquake Component Terminology - : a surface along which some part of the Earth (rocks) has been broken and displaced (moved) - Focus: point within the Earth where the initial fault slippage generates earthquake energy. The focus represents the area of released elastic energy. - Seismic waves are vibrations produced by earthquakes that radiate from the (focus) energy source. - Epicenter: a point on the Earth’s surface directly above the focus

Earthquake components Earthquake Instrumentation - Seismograph: instrument used to measure seismic waves (earthquake waves) - Seismogram: recording of a seismic event or “graph” of an earthquake made by a seismograph - Saw video of a seismograph recording an actual (small) earthquake

The ones who never try are the real losers

Seismic Waves and Density - The denser an Earth substance (such as air, water, soil, rocks, etc.), the faster that most forms of vibration energy (seismic waves) from an earthquake can travel. - This is why most seismic waves travel through the Earth than the Earth’s surface

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Seismic Pathways: Body and Surface

- Seismic body pathways are “paths” taken by seismic waves in the interior of the Earth. - Seismic surface pathways are “paths” taken by seismic waves on the surface of the Earth. - Seismic wave intensity and speeds are directly affected by the pathways that they travel within the Earth’s interior (body pathways) and on the Earth’s surface (surface pathways). - Body seismic waves travel faster within the Earth (which provides body pathways) than surface seismic waves which travel slower along the Earth’s surface (which provides surface pathways).

Two General Classes of Seismic Waves - Because of density and pathway differences, there are two “classes” of seismic waves. Each class could be further subdivided. 1. Seismic Body Waves and pathways are represented by two types of waves: a. Primary Seismic Waves (P-Waves) which move in solids, liquids and gasses b. Secondary Seismic Waves (S-waves) which move only in solids

2. Seismic Surface Waves: Although there are several types of surface waves, we will lump them into one type. c. Surface Seismic Wave (Surface waves) which moves Earth’s surface, somewhat similar to ocean waves

Relative Speeds and Arrival Times of the Two Classes of Seismic Waves - P-Wave speed: Primary body waves arrive first because they are the fastest waves. - S-Wave speed: Secondary body waves arrive second, later than P-waves. - Surface seismic wave speed: This wave is slower than P-waves and S-waves.

P-Wave Speed and Movement: 1) Primary waves will arrive first from an earthquake because the P-Waves are the fastest of the other seismic waves. 2) P-Waves are formed by alternating pulses of compression and dilation (a rapid push-pull). 3) P-Waves pass through solids, liquids and gasses.

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Life is tough – it is even tougher if you are stupid – John Wayne

S-Wave speed and movement: 1) Secondary waves will be the second wave of energy to arrive at a location. 2) S-Waves vibrate perpendicular to the direction of travel (a shearing motion) 3) S-Waves do not travel through liquids and gasses – only solids. 4) Near the earthquake, the S-Waves are larger and more dangerous than P-waves.

Surface Seismic Wave speed and movement: 1) Surface Seismic Waves are restricted to traveling along Earth’s surface. 2) Surface Seismic Waves are travel slower than P-waves and S-waves. 3) Surface Seismic Waves have an orbital motion, similar to ocean waves that would be traveling through rocks instead of water.

Modeling - Modeled P-wave with a slinky - Modeled S-wave with a rope “standing wave” - Modeled surface wave by waving rope up and down

Actual Earthquake Focus Depth Calculation - An earthquake focus depth (point of slippage) can be calculated by comparing the arrival times of the three seismic waves (first P-wave, first S-wave and first surface wave.

Focus depth

Earthquake Focus and Related Depths - Shallow focus earthquakes (90% of all earthquakes): Shallow focus depths range from the surface to 70 km depth (0 - 42 miles deep). Divergent zones, convergent zones and transform fault zones are the origin for most of these earthquakes. Other sources would include explosions and “collapsing forces”. - Intermediate focus earthquakes: focus ranges from 70-300 km depth (42 – 180 miles deep). These are found mostly deeper within subduction zone (faults). - Deep focus earthquakes (less than 3%): focus ranges 300-700 km deep (180 – 420 miles deep). These occur within deep subduction zones (faults). - Beyond this 700 km. depth, the rocks would be very hot and basically become too soft or plastic to break or compress.

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Locating an Earthquake Epicenter - An earthquake epicenter is located by calculating a distance by comparing P-wave and S-wave arrival times at a seismograph station. - The epicenter distance calculated by this method would represent the length of a radius of a circle, drawn from this seismic station.

Radius from stations - To find the actual epicenter requires drawing a circle (using the radius) from at least three different seismograph stations. - The earthquake epicenter would be located at the intersection of at least three circles.

Locating the epicenter of an earthquake - The further away the seismic station from the epicenter, the longer the wait for the arrival times

Earthquake Types Classified by Energy Sources: 1) Tectonic Earthquakes (most earthquakes) are those quakes caused by the sudden release of energy stored within the rocks along a fault and/or plate boundaries (divergent, transform and convergent zones). 2) Volcanic (igneous) Earthquakes associated with magmas and volcanoes. 3) Explosion Earthquakes that are caused by explosives, bombs and meteorites. 4) Collapse Earthquakes are caused by collapsing caves (karst topography) and underground mines. - Although the first two classes of earthquakes are more common, any type can cause a large local seismic event

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Tectonic Energy Earthquakes

Earthquake zones 1) US Tectonic Earthquakes (most earthquakes): - The Western US earthquake zones are associated with present-day tectonic features. - The Eastern US earthquake zones are associated with “intra-plate” earthquakes; those that occur along ancient or fail plate boundaries.

Volcanic Energy Earthquakes 2) Volcanic (igneous) Earthquakes are caused by the upward movement of magma. - As the magma rises toward the Earth’s surface, the molten rock fractures rock masses and causes continuous tremors that can last to several hours or days.

seismic from a volcano - Earthquakes are also associated with “exploding volcanoes.”

Most tectonic and “igneous” earthquakes occur along present or ancient plate boundaries - Seismic activity helps define the boundaries of tectonic plates and their processes. - The Pacific Ocean rim accounts for about 80% of our planet’s earthquakes.

I never let schooling interfere with my education – Mark Twain

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Earthquakes

- Earth tremors: minor earthquakes - : small tremors that precede the main earthquake - are earthquakes that follow the largest (main) shock of an earthquake sequence. They are smaller than the main shock of energy. - Aftershocks can continue over a period of weeks, months, or years. - In general, the larger the main shock, the larger and more numerous will be the aftershocks, and the longer the aftershocks will continue.

Damage to Structures by Earthquakes 1. Depends upon distance of structures from epicenter of the earthquake 2. Depends upon design of buildings and structures (“earthquake-proof”) 3. Depends upon type of surface material (sand or bedrock) that structure is built upon

Types of Earthquake Damage 1) Movement and building collapses

- Depth to bedrock affects the amount of damage that an area will suffer. - Structures built on bedrock usually suffer considerably less damage than structures built on sand or clay. - Saw example and video of the 1989 World Series earthquake 2) Fires are commonly caused by broken gas and fallen power lines from quakes. 3) Tsunamis (as we covered in previous lessons)

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4) Landslides and liquefaction - Liquefaction: is a phenomenon by which wet sand can become liquid-like when strongly shaken. The liquefied sand may flow to the surface like a volcano. - Structures can fall over “intact” under the influence of liquefaction.

5) Floods from breaking dams

Mercalli Earthquake Intensity Scale - Created by Giuseppe Mercalli (1902) to measure damage - Earthquake intensity is an evaluation of the severity of the ground movement as reported by witnesses. - The damage in an area caused by an earthquake is compared to a set of data used by Mercalli. - The Mercalli Scale is used by insurance companies to set insurance rates on structures.

Mercalli Intensity Scale - Mercalli Earthquake Intensity is based on: 1) Total energy released 2) Distance from the epicenter 3) Rock type (usually, the softer the rock or sediment, the greater the intensity)

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Richter Magnitude Earthquake Scale - Earthquake magnitude is an objective measure of the maximum energy released by an earthquake. - Repeat – the Richter measures the absolute maximum energy of an earthquake. - Magnitudes compare earthquakes to exploding quantities of TNT. - Today we use the modified Richter scale (1-12). - Each whole number is 30 times stronger than the previous number on the scale

- The largest known Richter earthquake is 9.5 that occurred in Chile.

Earthquake Folklore - The Swallowing Earth: No one has fallen into an earthquake chasm and died. - Earthquake Immunity: Small earthquakes will not prevent large earthquakes. - Astrological Considerations: Aligned planets do not create earthquakes.

Clarkwood Fault - We do not expect many earthquakes in the Corpus Christi area, because there is no shallow bedrock that is hard enough to store strong elastic energy. - The local Clarkwood Fault produces only very weak seismic signatures because it involves only relatively soft sediment.

Leopard Street/Clarkwood Fault 9

Earthquake Predictions - There are just too many factors to make accurate prediction as to the exact timing of an earthquake event. - Gave example of Parkfield CA for predicting earthquakes (and Turkey)

Large Historic American Earthquakes - Far West-Texas of Valentine experienced its most severe earthquake in1931. It had a magnitude of 5.80 and an intensity of VIII. - There have been historic major earthquakes in South Carolina and Massachusetts. -Largest Continental USA earthquake, that had aftershocks for years, was located near , along the Mississippi River. This earthquake was rated at an estimated +8.0 magnitude (and was stronger than any California earthquake)

Earthquake Safety - In earthquake areas, follow earthquake safety guides and buy earthquake proof homes.

The Moho - Named after Croatian Andrija Mohorovicic - Moho or Mohorovicic discontinuity: the “seismic” contact between the oceanic crust and continental crust with the “frozen upper mantle”

Just because it is hard does not mean that you have to quit

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Mapping the Earth’s Interior Using Seismic Waves - S-waves cannot pass through liquids; thus we can map the Earth’s liquid core. - P-waves are reflected and refracted while passing through the Earth, which we use to map Earth’s mantle as well as Earth’s inner and outer core.

S-waves help define Earth’s liquid core

Seismic wave pathways and patterns mapping inner & outer cores

For those who refuse education: --remember, you are hired now because you are cheap to hire and easily replaced

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(For your information only) Earthquake Information Bulletin

Earthquake maps predict the approximate percentage of each designated area that will liquefy and show surface manifestations of liquefaction such as sand boils and ground cracking. Liquefaction is a phenomenon that is caused by earthquake shaking. Wet sand can become liquid-like when strongly shaken. The liquefied sand may flow and the ground may crack and move causing damage to surface structures and underground utilities.

When you feel an earthquake, duck under a desk or sturdy table. Stay away from windows, bookcases, file cabinets, heavy mirrors, hanging plants, and other heavy objects that could fall. Watch out for falling plaster and ceiling tiles. Stay undercover until the shaking stops, and hold onto your cover. If it moves, move with it. Below are some additional tips for specific locations:

* If you are in a HIGH-RISE BUILDING, and not near a desk or table, move against an interior wall and protect your head with your arms. Do not use the elevators. Do not be surprised if the alarm or sprinkler systems come on. Stay indoors. Glass windows can dislodge during the quake and sail for hundreds of feet. * If you're OUTDOORS, move to a clear area away from trees, signs, buildings, electrical wires, and poles. * If you're on a SIDEWALK NEAR BUILDINGS, duck into a doorway to protect yourself from falling bricks, glass, plaster, and other debris. * If you're DRIVING, pull over to the side of the road and stop. Avoid overpasses, power lines, and other hazards. Stay inside the vehicle until the shaking is over. * If you're in a CROWDED STORE OR OTHER PUBLIC PLACE, do not rush for exits. Move away from display shelves containing objects that could fall. * If you're in a WHEELCHAIR, stay in it. Move to cover, if possible, lock your wheels, and protect your head with your arms. * If you're in the KITCHEN, move away from the refrigerator, stove, and overhead cupboards. (Take time NOW to anchor appliances, and install security latches on cupboard doors to reduce hazards.) * If you're in a STADIUM OR THEATER, stay in your seat and protect your head with your arms. Do not try to leave until the shaking is over, then leave in a calm, orderly manner. Avoid rushing toward exits.

AFTER THE EARTHQUAKE CHECK LIST * Be prepared for aftershocks, and plan where you will take cover when they occur. * Check for injuries. Give first aid, as necessary. * Remain calm and reassure others. * Avoid broken glass. * Check for fire. Take appropriate actions and precautions. * Check gas, water, and electric lines. If damaged, shut off service. If gas is leaking, don't use matches, flashlights, appliances, or electric switches. Open windows, leave building, and report to the gas company. * Replace all telephone receivers, and use for emergency calls only. * Tune to the emergency broadcast station on radio or television. Listen for emergency bulletins. * Stay out of damaged buildings

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(For your information) TEXAS EARTHQUAKES OR SEISMIC EVENTS

The October 22, 1882 earthquake felt, in Texas, was probably centered in or ; the total felt area covered about 375,000 square kilometers. At Sherman, Texas, heavy machinery vibrated, bricks were thrown from chimneys, and movable objects overturned. A May 3, 1887, earthquake in Sonora, Mexico, caused damage at Bavispe and was felt strongly in parts or Arizona, New Mexico and Texas. The epicenter was in the Sierra Madre Occidental Range.

On January 8, 1891, violent shaking of buildings and a few toppled chimneys were reported from Rusk, Texas. These effects were evaluated as intensity VII, although other towns in eastern Texas along a northeast- southwest line through Rusk experienced tornadoes and sudden, violent wind storms producing effects similar to, and in some cases more damaging than, those in Rusk.

A locally damaging earthquake occurred at Panhandle, Texas, on March 28, 1917. Some cracked plaster was reported, and children were evacuated from a school building (VI).

Another disturbance occurred in the area on July 30, 1925. There were three distinct shocks over a period of 15 seconds. Major problems were the shaking of dishes from shelves and rattling and creaking of furniture (V). The shocks were felt over an area of approximately 518,000 square kilometers including distant points such as Roswell, New Mexico, 350 kilometers away; Tulsa, Oklahoma, 480 kilometers away; and Leavenworth, , 640 kilometers away.

The 1931 western Texas earthquake heavily damaged many buildings at Valentine. Also, many chimneys fell (VIII). The shock occurred at 5:40 a.m. on August 16; although people were panic stricken, there were no fatalities and only a few minor injuries from falling adobe. Adobe buildings suffered most, and cement and brick walls in many places were badly cracked. Even though Valentine bore the brunt of the shock, damage was reported from widely scattered points in Brewster, Culberson, Jeff Davis, and Presidio Counties. Cracked walls and damaged chimneys were reported from several towns. The total felt area covered about 647,000 square kilometers in Texas and New Mexico and an estimated 518,000 square kilometers in Mexico. The earthquake was accompanied by rumbling subterranean sounds heard over practically the entire affected area. The shock, measured at magnitude 6.4, was strongly recorded on all seismographs in North America and at stations all over the world. Numerous aftershocks were felt in the epicenter region; the strongest, on August 18, was intensity V at Alpine, Lobo, Pecos, and Valentine and intensity IV at Carlsbad, New Mexico. A minor was felt at Valentine on November 3.

Slight damage resulted from an earthquake in the Mexia - Wortham area on April 9, 1932. Loose bricks were thrown down, and some plaster cracked (V-VI). The shock was also felt at Coolidge, Currie, Groesbeck, Hillsboro, Teague, and Richland. A moderate earthquake affected an area of about 7700 square kilometers in northeastern Texas and an adjoining portion of Oklahoma on April 11, 1934. The tremor was most distinctly felt at Arthur City, Caviness, Chicota, Powderly, and Trout Switch (intensity V). Many persons who felt the shock reported having heard a roaring or rumbling noise. Two shocks were recognized by many observers.

A widely felt earthquake with an epicenter in the Panhandle region occurred on June 19, 1936. Intensity V effects were noted at Gruver, White Deer, and Whittenberg, Texas, Kenton, Oklahoma, and Elkhart, Kansas. The area of perceptibility covered about 103,000 square kilometers. On March 11, 13

1948, another shock in the Panhandle area caused minor damage, consisting mainly of cracked plaster, in northern Texas, a few places in northeastern New Mexico and northwestern Oklahoma, and one place in southeastern Colorado. The strongest effects (VI) were reported from Amarillo, Channing, Dalhart, Electric City, Panhandle, Perico, and Perryton. The felt area, which was slightly larger than that of the preceding earthquake, covered about 129,000 square kilometers. The Texas Panhandle area was the center for another moderate shock on June 20, 1951. Damage to plaster (VI) occurred at Amarillo and Hereford. The felt region extended from Lubbock to Borger.

Four shocks over 6 hours affected an area of about 26,000 square kilometers in northeastern Texas and bordering portions of Arkansas and Louisiana on March 19, 1957. Press reports noted that a few objects were upset and at least one or two windows were broken. Newspaper office and police station switchboards were swamped with calls from alarmed residents. Intensity V effects were felt at Diana, Elkhart, Gladewater, Marshall, Nacogdoches, and Troup, Texas, and Magnolia, Arkansas.

A series of moderate earthquakes in the Texas - Louisiana border region near Hemphill started on April 23, 1964. were determined on April 23, 24, 27, and 28. There were numerous additional shocks reported felt at Pineland, Hemphill, and Milam. The only damage reported was from the magnitude 4.4 earthquake on April 28 - wall paper and plaster cracked at Hemphill (V). The magnitude of the other epicenters changed from 3.4 to 3.7. Shocks were also felt at Pineland on April 30 and May 7. On June 2, three more shocks were reported in the same area. The strongest was measured at magnitude 4.2; intensities did not exceed IV. Another moderate earthquake on August 16 awakened several people at Hemphill and there were some reports of cracked plaster (V). The shock was also felt at Bronson, Geneva, Milam, and Pineland.

The Texas Panhandle region experienced another tremor on July 20, 1966. The magnitude 4.8 earthquake knocked books from a shelf in one home and was felt by nearly all (V) in Borger. At Amarillo, an observer in the courthouse reported a chair moved 4 or 5 inches. A similar effect was noted at the Federal Aviation Administration control tower at the Municipal Airport; observers thought a truck had hit the tower. Several street signs were knocked down and windows were broken (VI) at Kermit from a magnitude 3.4 earthquake on August 14, 1966. The shock was also felt at Wink, Texas, and Loco Hill, New Mexico.

Four small earthquakes occurred near El Paso on May 12, 1969. The first two shocks, 23 minutes apart, were measured at magnitude 3.3 and 3.4. One house in El Paso had hairline cracks in the ceiling and cracks in the cement driveway (VI). These earthquakes were also felt at Newman.

On February 15, 1974, an earthquake in the Texas Panhandle caused plaster cracks (V) at Booker, Darrovzett, and Perryton. Similar effects were noted at Liberal, Kansas, and Texhoma and Woodward, Oklahoma. The magnitude 4.5 shock was felt over an area of about 37,000 square kilometers.

A magnitude 4.2 earthquake occurred near Fashing and Pleasanton in Atascosa County on 9 April 1993. This earthquake is one of several in this region which may have been induced by petroleum production

A magnitude 3.8 earthquake near Alice in Jim Wells County occurred on 24 March 1997

Earthquake Information Bulletin, Volume 9, Number 3, May - June 1977, by Carl A. von Hake. 14