Earthquake Intensity vs. Earthquake Magnitude

Measuring Earthquake Intensity

Homework Project 4                                                                                      25 Points

 

 

Earthquake Intensity vs. Earthquake Magnitude

Several methods are used to describe the strength of an earthquake. While some methods characterize earthquake strength using a single numerical value (e.g. the moment magnitude or Richter scales), others describe the intensity of a quake using numerical values that can vary across the region.  These methods commonly use earthquake damage reports to map out the effect of the quake over large areas.

 

Modified Mercalli Intensity Scale

Although numerous earthquake intensity scales have been developed over the last several hundred years, the one currently used in the United States is the Modified Mercalli Intensity Scale. This scale, composed of 12 increasing levels of intensity that range from imperceptible shaking to catastrophic destruction, is designated by Roman numerals (I to XII). It does not have a mathematical basis but is based on testimonies of those who experienced the earthquake and observable earthquake damage.

 

The Modified Mercalli Intensity value assigned to a specific site after an earthquake has a more meaningful measure of severity to the nonscientist than the magnitude because it refers to the effects actually experienced at that place.

Intensity values decrease with greater distance from the source. The intensity of shaking is also influenced greatly by the type of underlying material (i.e. soft sediments commonly shake more than hard rock). The lower numbers of the intensity scale generally deal with the manner in which the earthquake is felt by people. The higher numbers on the scale are based on observed structural damage.

 

October 31, 1895 Earthquake, Central United States

Magnitude 6.8

A moderately strong earthquake struck the Midwest at 5:07 AM (Central Standard Time) October 31, 1895. The quake was centered in the Mississippi valley region and had an estimated magnitude of 6.8 on the Richter scale. It was felt as far away as Washington, D.C. and Buffalo, NY.

 

Although this quake was widely felt throughout the Midwest, it caused serious damage only in the epicentral area near the confluence of the Ohio and Mississippi rivers. No substantial buildings collapsed, no one was killed, and there were few injuries.  Descriptions of the earthquake intensity and damage begin on Page 3 of this exercise.

 

Exercise Procedure: 

  1. Beginning on Page 3 are 53 descriptions of the 1895 earthquake taken from newspaper accounts from the day after the event. Read each earthquake report and use the provided Modified Mercalli Scale (Page 2) to determine the intensity value for each location.  IMPORTANT:  When determining the intensity value for a location, use the descriptions of shaking or damage indicative of the highest Mercalli value.  For example, the shaking that will knock down a brick wall (Mercalli VIII), will also cause hanging object to swing (Mercalli III).

 

  1. One you have determined a Modified Mercalli Scale value, mark it down next to the VALUE: label underneath each account. Also list the value on the attached worksheet (Page 9).

 

  1. Each student will turn in the Page 9 of the Worksheet prior to class on the assignment due date (Ocober 25).

 

  1. Each student must also bring the completed earthquake descriptions (Pages 3-8) to class on the on the assignment due date for the purpose of constructing an Isoseismal map of the area affected by the October 31, 1895 earthquake.

MODIFIED MERCALLI INTENSITY SCALE

  1. Not felt. Marginal and long period effects of large earthquake.

 

  1. Felt by persons at rest, or on upper floors, or favorably placed. May not be recognized as an earthquake.

 

 

III. Felt indoors. Hanging objects swing. Vibration like passing of light trucks. Duration estimated. May not be recognized as an earthquake.

 

  1. Dishes, windows, and doors rattle. Tall buildings sway. Vibration like passing of heavy trucks. Duration estimated. Still may not be recognized as an earthquake.

 

  1. Felt outdoors; direction estimated. Sleepers wakened. Liquids disturbed, some spilled. Small unstable objects displaced or upset. Doors swing, close, open. Shutters, pictures move. Pendulum clocks stop, start, change rate.

 

  1. Felt by all. Many frightened and run outdoors. Persons walk unsteadily; sleepers thrown from beds. Windows, dishes, glassware broken, knick-knacks, books, etc., shaken off shelves, pictures off walls. Furniture moved or overturned. Weak plaster and masonry cracked. The bells of churches, schools and clocks ring. Trees, bushes shaken (visibly, or heard to rustle). In areas underlain by saturated sediment, sand and mud is ejected toward the surface; cracks can form in pavement overlying saturated ground.

 

VII. Difficult to stand. Noticed by drivers of motor cars. Furniture broken. Some damage to strong masonry, including cracks. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles. Some cracks in masonry. Waves on ponds; water turbid with mud. Small slides and caving along sand or gravel banks.  Concrete irrigation ditches damaged.

 

VIII. Steering of motor cars affected. Significant damage to masonry including partial collapse. Fall of stucco and some masonry walls. Fall or twisting of strong chimney’s, factory stacks, monuments, towers, elevated tanks. Frame houses moved off foundations; loose panel walls thrown out. Branches broken from trees. Changes in flow or temperature of springs and wells.

 

  1. General panic. Complete collapse of homes and buildings with some foundation damage. Serious damage to reservoirs. Underground water and gas pipes ruptured. Large, conspicuous cracks formed in ground.

 

X+. Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc. Rails bent slightly to greatly. Underground pipelines completely out of service. Damage nearly total. Massive objects thrown into the air.

Newspaper reports of the 1895 Central United States Earthquake

Below are newspaper accounts from the eastern and central part of the United States of the damage caused by the October 31, 1895 earthquake.  Using the damage described in the reports, assign a Modified Mercalli Scale value (I to XII) for each town listed below.

 

Numbers before each report are keyed to locations on a base map that we will use in the next in-class exercise.  For that exercise you will plot your determined a Modified Mercalli Scale value for each corresponding map location by marking the location circle on the map with color that corresponds to the value.  We will go over this in class, so don’t sweat it now.

 

Alabama
  1. Montgomery, AL: Light earthquake lasting less than 30 seconds felt in the city at 6:30 a.m. today; windows rattled and beds shaken; No damage.

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  1. Gadsen, AL: Earthquake shock here early this morning shook homes and woke people from their beds.

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Arkansas
  1. Fort Smith, AR: A very slight earthquake shock was felt by a few individuals here at a few minutes past 6 o’clock a.m., but without any rumbling noise. Of about fifty persons asked relative to the shock only two stated that they felt it—Dr. Hatchett, a practicing physician, and Mr. W. Abbot, lumber merchant.  Dr. Hatchett reports the motion as lateral, but does not know the direction of movement.  Others felt the vibrations but did not know recognize it as an earthquake.  The Weather Bureau observer did not feel the shock.

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  1. Little Rock, AR: Distinct earthquake, the vibrations being directed east and west and lasting about one minute, occurred at 6:15 am.

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District of Colombia
  1. Washington, DC: A slight earthquake was felt by some residents of the District on Thursday morning.

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Indiana

  1. Fort Wayne, IN: There were three distinct shocks of earthquake here at 5:14 this morning.  The second shock was the most severe.  Houses shook, windows rattled as if a severe windstorm was prevailing and the occupants were such alarmed.  No damage is reported.

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  1. Laport, IN: Northern Indiana was shaken by an earthquake Thursday morning. The disturbance caused great excitement in the vicinity of Dune Park west if this city where buildings where violently shaken. The shock was felt here at five o’clock, people being awakened by the peculiar sensation.

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  1. Liberty, IN: At 5:15 this morning an earthquake lasting several minutes was felt at Liberty.  It was the most severe ever noticed.  Brick buildings trembled and cracked, dishes rattled, and the tops of some older chimneys fell.  Persons living in three and four-story brick buildings were greatly excited, leaving the buildings in their nightclothes.

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  1. Terre Haute, IN: At 5:10 this morning an earthquake, lasting fully a minute, was felt in this city.  Houses shook, windows rattled and were broken, clocks stopped, and the courthouse clock bell tapped twice.

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  1. Anderson, IN: At Anderson every building was shaken, five distinct shocks being felt.  The vibrations were from north to south.  Furniture was disturbed, crockery was rattled and cupboard doors were thrown open.  Hundreds of people ran from their houses in fright, but little damage was done.

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  1. Brazil, IN: A distinct earthquake shock was felt here at five o’clock Thursday morning.  The shock was so severe that the upper portions of several chimneys were shaken from dwelling houses.

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  1. Princeton, IN: One of the most distinct earthquake shocks ever felt occurred here at 6:15 a.m.  Vibration west to east lasting over one half minute.  Many chimneys collapsed and some buildings were shaken off their foundations.

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Illinois

  1. Litchfield, IL: An earthquake was felt here at 5:10 a.m.  Dishes were thrown upon the floor and people awakened from their slumbers.  No serious damage was done.

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  1. Grayville, IL: An earthquake, the most terrific one ever felt here, visited this city and vicinity early this morning.  Building rocked like cradles and in some instance bricks were shaken from chimneys.  The shock lasted several seconds and seemed to be from west to east.

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  1. Moline, IL: Moline and vicinity visited by an earthquake at 5:15 this morning.  Houses rattled and contents shaken.  It lasted half a minute.  No damage.

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  1. Monmouth, IL: A heavy earthquake shock was felt here about 5 this morning.  Many people were awakened, doors were opened, and furniture shaken.

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  1. Hillsboro, IL: A distinct earthquake shock of thirty seconds duration occurred here at 5:30 this morning, so strong that almost every one in the city was awakened. The oscillation was from east to west.

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Iowa

  1. Ottumwa, IA: Three distinct shocks of earthquake were felt here at 5;15 this morning.  Houses shook and woke sleeping inmates.  In some cases windows were broken.

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  1. East Des Moines, IA: The first earthquake shock in thirty years was felt here at 5;10 this morning.  It lasted several minutes and there were two distinct shocks.  Doors and windows rattled and people were awakened.

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Kansas

  1. Topeka, KS: An earthquake shock occurred about 6:12 a.m. today.  The weather observer was not awakened by it, though a large number of slumbering citizens were.

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  1. Abiline, KS: A slight earthquake was felt at about 5:10 Thursday morning lasting about 5 seconds.  Some residents reported vibrations similar to the passing of a high-speed freight.

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Kentucky

  1. Louisville, KY: Three distinct and very severe earthquake shocks were experienced this morning.  The first occurred at 6:07 a.m. and was followed a few seconds later by a second, and after a brief interval, by the third and most violent.  While no serious damage resulted, the vibrations were of sufficient force to cause the ringing of school bells, the rocking of articles of furniture, and the displacing of ornaments and other articles from tables and mantels.  The disturbance appeared to proceed from the northwest toward the southeast.  A number of persons state that slight shock occurred shortly after midnight, and many report that the main shock this morning was accompanied by a brilliant flash of light, resembling lightening.  The earthquake was very general throughout Kentucky and was apparently most severe in the extreme western counties.

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  1. Columbus, KY: At Columbus, Kentucky the shock was sufficient to crack brick walls and throw off plaster. The first shock was immediately followed by two others of less intensity.

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  1. Paducah, KY: At 5:10 o’clock this morning a severe shock of earthquake was felt all over town.  Houses swayed to and fro, a number of chimneys were completely destroyed, and several brick walls collapsed.

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Louisiana
  1. New Orleans, LA: A slight shock of earthquake was felt here this morning at 5:09.  The vibrations lasted less than 10 seconds but many residents did not immediately recognize the disturbance as an earthquake.

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Michigan

  1. Grand Haven, MI: Sharp earthquake shock felt this morning at 6:20, the vibrations lasting fully one minute.  No damage was done.

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Mississippi
  1. Vicksburg, MS: An earthquake shock was reported upon reliable authority in the vicinity of the city at 6:03 a.m.  Its duration was 15-20 seconds and was apparently continuous….The shock rattled station windows and doors and the word moderate would best describe its intensity.

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Missouri

  1. Hannibal, MO: The shock of the earthquake was felt very perceptibly in this city at 5:10 this morning. There were three distinct waves, from west to east, and every building in the city rocked to and fro.   The shock lasted about one minute.  In many of the stores, goods were thrown from the shelves and in residences, dishes were thrown off tables and pictures from walls.  The tops of several chimneys fell and the walls of some brick buildings were cracked.

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  1. St. Louis, MO: The most severe felt since the year 1811. At 5:12 a.m. several severe earthquake shocks were distinctly felt here.  The vibrations were from east to west and each shock continued several seconds.  The operators in the Western Union telegraph office became alarmed and several rushed from the building.  The shocks were not accompanied by any rumbling noise.  Clocks were stopped and windows rattled, but no serious damage has as yet been reported.  Up to 10 a.m. no damage had been reported beyond the toppling of a few old chimneys, a general swaying of beds and the rattling of furniture and other loose things.  The shock was the severest ever felt here and lasted fully two minutes.  The weather bureau reports the vibrations were from east to west…. Prof. F.E. Mipher of the Washington University, who has taken a deep interest in the study of earthquakes, said to an Associated Press representative today:  ‘To the best of my knowledge this is the most severe earthquake in this locality since the New Madrid earthquake in southwest Missouri in 1811’.

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  1. Chillicothe, MO: An earthquake shock was felt in this city at 5:10 this morning.  Sleeping people were aroused by their beds being violently shaken and other evidences of the internal disturbance were manifested.  The shock lasted thirty seconds.

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  1. Chicopee, MO: Two distinct earthquake shocks were felt here about 4:40 this morning.  The former was light, but the latter was stronger, shaking house till the windows rattled and waking all who slept.

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  1. Hermann, MO: An alarming earthquake shock was felt in this vicinity at 5 o’clock this morning and lasting about 30 seconds. Home furnishings were upset, pictures knocked from walls, and nearly all the clocks in the city were stopped.

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  1. Charleston, MO: The person…reporting from that place (Charleston) says that the force was ‘sufficient to break several plate-glass windows, crack brick walls, and throw down brick chimneys.  For a few minutes afterward water spurted from several pumps’  He also reports:  ‘About four miles southwest of this place two wooden houses and a barn were completely collapsed due to the shaking’.   There were at least two slight shocks immediately following the severe one, at intervals of ten or fifteen minutes.

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  1. Puxico, MO: At Puxico stoves were turned over and the chimneys and flues of most homes were tumbled to the ground.

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  1. Cape Girardeau, MO: At five o’clock Thursday morning our people were aroused from their slumbers by a roaring sound followed by an awful earthquake shock.  The shock began by a quivering motion of the earth and as it increased, houses creaked and rocked like the branches of trees in a storm.  The shock lasted nearly four minutes and nearly everybody in the city got out of bed.  Furniture was overturned and broken, the plastering in some houses was cracked, and it is believed that many cisterns are ruined.  Ten thousand dollars in gold that was stacked up in the lock safe in the First National Bank was found this morning scattered all about the safe.

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New York

  1. Buffalo, NY: Some residents of the city reported a slight earthquake shock Thursday morning at 6:15 lasting about 10 seconds.  The vibration felt to some like the passing of a wagon team.

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Ohio

  1. Toledo, OH: At 5:30 this morning the earthquake shock awakened many people. Houses shook, clocks were stopped and chandeliers jingled, but no damage is reported.

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  1. Gallipolis, OH: Between 5 and 6 o’clock this morning an earthquake shook buildings and rattled windows and doors in the city for approximately 30 seconds.

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  1. Cleveland, OH: Earthquake shocks were felt in this city and throughout Northern Ohio shortly after 6 o’clock this morning.  Dishes, windows and doors rattled, and tall buildings swayed perceptibly and the occupants were much alarmed.  The shock lasted nearly a minute and was accompanied by a heavy rumbling.

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  1. Zanesville, OH: A few minutes after 5 o’clock this morning residents in all parts of the city were aroused by distinct earthquake shocks.  It caused residences to tremble violently, in some cases loosening pictures from the walls and causing stove pipes and tinware to fall from their fastenings.  Trembling continued half a minute and caused no little alarm.  It was the most severe earthquake ever felt in this vicinity.

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  1. Dayton, OH: A severe earthquake shock was distinctly felt in this city at 6:12 this morning. Windows were rattled, buildings quivered, and people were awakened from their beds.  It was at first supposed to be a natural gas explosion.  No damage done.

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  1. Cincinnati, OH: An earthquake shock was felt here at 5:12 this morning, the most distinct for ten years.  It began with a slight tremulous motion that continued for perhaps one minute and then followed two or three violent undulations, shaking brick buildings and rattling windows, like some gigantic explosion.  The whole demonstration must have occupied nearly two minutes.  It was accompanied by a slight roaring sound which continued after the shaking ceased.

 

The first effect was felt about 5:10, and people in various parts of the city were awakened by the quivering of their beds.  Most of those who had telephones convenient, immediately called upon the central station office and for a few minutes the operators were kept busy.  All reports agreed as to and the general effect.  The operators at the central office felt the floor shake under them and transmitters and other objects rock to and fro.

 

Mr. Sewick, the Newport druggist, was thrown out of bed and dazed for several minutes.

 

A newsboy living at 58 West Third Street, was thrown out of bed and whole family at Oliver and Linn suffered a like experience.

 

Colonel Dietsch, Chief of Police, was thrown out of bed and immediately communicated with headquarters, where his views of the matter were confirmed.  From best accounts the undulations were from the north; the force gradually expanded the further north it went.

 

The city hall was severely shaken.  The furniture was thrown about and several persons on duty there ran out.  Those there said the great stone pile swayed on its foundation.   The city workhouse was violently shaken, and inmates just getting up were thoroughly alarmed.

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Oklahoma

  1. Pondcreek, OK: A light earthquake lasting a few seconds was felt in Pond Creek Thursday morning. The vibrations caused hanging kitchen pots and kettles to sway throughout the event.

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Ontario, Canada
  1. Chatham, Ontario: A severe shock of earthquake was felt Thursday morning at six o’clock.  Reports from many in the town describe a rumbling of the ground during the earthquake similar to the passing of a large locomotive.

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Pennsylvania
  1. Altoona, PA: At 6:15 this morning an earthquake rattled windows and doors of the city.

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  1. Pittsburgh, PA: Slight earthquake shock was felt at Bellevue and McKeesport, suburbs of Pittsburgh, at 6 a.m.  The shock produced only a very slight jar and a slight movement of pictures, etc., hanging on walls, and continued but a few seconds.

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South Carolina
  1. Charleston, SC Light earthquake shock at 6:04 a.m.; Light tremors and vibrations lasting about eight seconds.

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Tennessee

  1. Chattanooga, TN: An earthquake shock was felt in this city at 6:10 a.m. today; duration of the vibration, thirty seconds.  No effect in this city outside of shaking chandeliers, rocking of houses, rattling of windows, and rocking of beds.

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  1. Nashville, TN: A sharp earthquake shock was felt here at about 5:10 this morning.  Vibrations were quite severe, lasting fully a minute, and waking many from their beds.

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  1. Memphis, TN: An earthquake shock of considerable severity was felt in this city this morning shortly after 6 o’clock.  A careful comparison of time by a number of competent observers shows that the vibrations from the first shock ceased at 6 hr. 07 min. 30 sec. a.m., having lasted about thirty seconds.  A secondary shock or vibration was observed at 6 hr. 14 min. 00 sec. by a number of reliable observers, though not by all.  There was no damage done in this city, except to the tops of two chimneys in the suburbs, which were shaken down.

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  1. Clarksville, TN: This morning at 5 o’clock a severe shock of earthquake continuing over half a minute was felt over this section, traveling north and south.  The earthquake rattled windows, caused displacement of home furnishings, and the ringing of church bells.  Slight damage was reported.

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Wisconsin

  1. Milwaukee, WI: There was a distinct earthquake shock felt in this city between 4:30 and five o’clock Thursday morning.  A tremor seemed to pass over the city, which caused the houses to shake and awakened many people.  The shock lasted for over a minute, and consternation prevailed among those who had been aroused from their slumbers. The shock lasted about one minute.

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  1. Wausau, WI: A slight earthquake was reported by some residents of Wausau around 6 o’clock Thursday morning. Most of the reports were from people that had yet to rise from their beds.  However, most residents were not aware of its passing.

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GLG 111D                                                                              NAME:                      

Measuring Earthquake Intensity                                          

Homework Exercise Worksheet

25 Points

 

 

 

Alabama

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Arkansas

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District of Colombia

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Indiana

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Illinois

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Iowa

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Kansas

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Kentucky

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Louisiana

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Michigan

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Mississippi

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Missouri

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New York

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Ohio

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Oklahoma

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Ontario, Canada

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Pennsylvania

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South Carolina

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Tennessee

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Wisconsin

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