Earthquake Intensity Activity

Earthquake Intensity Activity

Agassiz was great in the abstract but not in the concrete.

Zoology Building, Stanford University, April 18, 1906Directions:Use the modified Mercalli scale of earthquake intensity [MMI] to evaluate felt reports, damage surveys, and personal narratives collected after the April 18, 1906 Great San Francisco earthquake. The student should select the intensity [a Roman numeral from the MMI] that best fits each selected felt report, damage survey, or personal narrative. If the student feels that there is not enough information in a felt report, damage survey, or personal narrative to assign a single intensity, a narrow range of intensities may be selected. The student should be prepared to justify their answer with specific information from each selection.Modified Mercalli Intensity Scale from FEMA: I. People do not feel any Earth movement.

II. A few people might notice movement if they are at rest and/or on the upper floors of tall buildings.

III. Many people indoors feel movement. Hanging objects swing back and forth. People outdoors might not realize that an earthquake is occurring.

IV. Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors rattle. The earthquake feels like a heavy truck hitting the walls. A few people outdoors may feel movement. Parked cars rock.

V. Almost everyone feels movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken. Pictures on the wall move. Small objects move or are turned over. Trees might shake. Liquids might spill out of open containers.

VI. Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage.

VII. People have difficulty standing. Drivers feel their cars shaking. Some furniture breaks. Loose bricks fall from buildings. Damage is slight to moderate in well-built buildings; considerable in poorly built buildings.

VIII. Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures such as towers and chimneys might twist and fall. Well-built buildings suffer slight damage. Poorly built structures suffer severe damage. Tree branches break. Hillsides might crack if the ground is wet. Water levels in wells might change.

IX. Well-built buildings suffer considerable damage. Houses that are not bolted down move off their foundations. Some underground pipes are broken. The ground cracks. Reservoirs suffer serious damage.

X. Most buildings and their foundations are destroyed. Some bridges are destroyed. Dams are seriously damaged. Large landslides occur. Water is thrown on the banks of canals, rivers, lakes. The ground cracks in large areas. Railroad tracks are bent slightly.

XI. Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground. Underground pipelines are destroyed. Railroad tracks are badly bent.

XII. Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move.

Postcard sent from Los Angeles to Ontario, Canada on April 19th, 1906

Sources:

The felt reports, damage surveys, and personal narratives in this activity are all excerpted from the following three sources:

Barker, Malcolm E., editor. Three Fearful Days: San Francisco Memoirs of the 1906 Earthquake and Fire. San Francisco: Londonborn, 2006Jordan, David Starr, editor. The California Earthquake of 1906. San Francisco: A.M. Robertson, 1907

Lawson, Andrew C., chairman. The California Earthquake of April 18, 1906. Washington, D.C.: Carnegie Institution, 1908 [reprinted 1969]Examples:

Example 1: Alturas, California reported by C.B. Towle [Lawson]

The hanging lamps in a saloon were found at 5h 20m to be swinging east and west. A tub leaning against the house on the porch was thrown down. Some men camped near the town felt a tremble of the earth. Others in camp several miles from the town were up and heard the low sound of the earthquake, but did not feel the shock.The fact that a lamp was seen swinging and that not everyone outdoors in the vicinity felt the earthquake suggests that this should be rated a III on the MMI. Example 2: Willits, California reported by R.S. Holway [Lawson]

Brick chimneys were quite generally wrecked. The Buckner Hotel was completely demolished.The structure was largely frame, with some brick veneer. The stores of the Irvine Muir Company were badly wrecked. Fire-walls fell; plaster, shelving, and goods were thrown to the floor. Brick walls fell in several other stores, and frame buildings were in some cases thrown from their foundations. Small cracks across some of the streets were reported, but they are now not visible. All brick buildings were damaged to some extent.Chimneys collapsing and some frame buildings [which were generally NOT bolted to their foundations in 1906] shifting suggest that the lowest that this could be rated is an VIII on the MMI. If the small cracks in the street did form, then a IX on the MMI would be the upper limit.Selections:Rate each of the following selections on the sheet provided.Selection 1: Anaheim, California reported by J.F. Walker [Lawson]

Very few people in Anaheim report having felt a shock at all. It was very slight. No clocks were [stopped].

Selection 2: Coalinga, California reported by G.F. Zoffman [Lawson]The tops of a few of the walls of brick buildings were slightly damaged.A few dishes and bottles were thrown from the shelves, and water was [slopped] out of the tanks, but none capsized.

Selection 3: Hollister, California reported by James Davis [Lawson]

Two shocks were felt, of which the second was stronger.A rumble preceded the shock by a second or so. In my house a piano and other heavy objects were moved on a polished floor so that the north ends moved 2 or 3 feet farther out into the room than the south ends. I was standing at the time of the heaviest shock, and was thrown from side to side in a north and south direction. People here all agree as to the north and south direction of the movement. Most chimneys fell north, but some fell east and west. Pictures on east and west walls, hanging by single wires 4 to 6 feet long, swung from 3 to 8 feet along the walls, leaving distinct scratches. Pictures similarly hung on north and south walls simply pounded back and forth, leaving puncturing in the plastering. Water-tanks seem to have fallen to the north always. Three brick buildings, each 2-story, 1 old and 2 new, went down flat, and 2 others were badly damaged. Wooden buildings in general were not damaged except [through] the fall of chimneys.Selection 4: Merced, California [Lawson]

Clocks generally were [stopped], and hanging objects were caused to swing. One chandelier was observed to swing north and south, and then in a circle.

Selection 5: San Jose, California reported by G.F. Zoffman [Lawson]

The earthquake threw down many brick and stone buildings, and with the exception of 4 or 5, damaged all the rest of the brick buildings, more or less. The damage done to frame houses was proportionately far less. Forty buildings were counted, however, that were thrown off their foundations and damaged to a greater or less extent. In many instances these buildings were completely demolished. Numerous wind-mills and tanks capsized, while at least 95 per cent of the brick chimneys [throughout] the town fell. Movable objects, such as pianos, were in most cases wheeled out into the roomWater and mud in many instances are reported as having spurted from the artesian wellsThe plate-glass windows on the south side of First Street were cracked much more than those on the north side. This phenomenon was not noticeable on the other streets.

San Jose High School after the earthquake.Selection 6: Millbrae, California reported by Roderic Crandall [Lawson]

At Millbrae there are but few buildings that could be affected by the shock, but the brick power-house of the San Mateo electric line was partially wrecked. The north and south walls fell, while the east and west ones remained standing. The latter stood because they were held by the steel trusses which spanned east and west.Selection 7: Yosemite Valley, California [Lawson]

A slight shock was felt.

Selection 8: near the beach on the west side of San Francisco, California reported by W.D. Valentine [Lawson]

We were residing on Forty-eighth Avenue, between K and L Streets, within a few hundred feet of the oceanIn our section the shock was violent. It awakened me instantly, and for a few seconds I was unable to rise, as I was thrown back in the effort. Meanwhile I was carefully watching the movements of an extremely tall and heavy oaken wardrobe which stood almost in the middle of the floor. The top first swung to the west, then to the north, then to the east, and fell directly to the south with such force that it went to pieces. Our heavy upright piano and various heavy articles of furniture were thrown completely over.Our lot,, was shortened at least a foot, which was shown by the folding of the fence. Electric-light poles in the street in front of us, which were in the sand, were thrown down. There was a fissure for about a block, between Forty-seventh and Forty-eighth Avenues, about 3 feet wide and 6 or 8 inches deep, which was of course in the sand. There were also other blow-holes in the sand, which emitted water and sulfurous odors. Selection 9: the Valencia Street Hotel in the Mission district of San Francisco, California reported by Police Lt. Henry N. Powell [Barker]

I just peeped in and walked out again through the lobby. Then, as I was going out of the door, the earthquake came and I hurried my paces. The first quiver was strong enough, but it was not terrifying. As I stepped out to reach the middle of the street and safety from the falling glass and stuff that accompanies all earthquakes, the twister came, and for a few moments it baffled me.Valencia Street not only began to dance and rear and roll in waves like a rough sea in a squall; but it sank in places and then vomited up its [cable] car tracks and the tunnels that carried the cables. These lifted themselves out of the pavement, and bent and snapped. It was impossible for a man to stand, or to realize just where he was trying to keep standing. Houses were cracking and bending and breaking the same as the street itself and the car tracks. In my wake, out of the Valencia Hotel, the night clerk came scampering and tripping over the waves and iron obstacles of the pavement. Close behind him followed the remittance man. I caught the remittance man, who was unsteady on his legs, and ran with him toward Nineteenth Street. As we ran we heard the hotel creak and roar and crash. I turned to look at it. It was then daylight and the dust of the falling buildings had not had time to rise. The hotel lurched forward as if the foundation were dragged backward from under it, and crumpled down over Valencia Street. It did not fall to pieces and spray itself all over the place, but telescoped down on itself like a concertina. This took only a few seconds.

The four-story Valencia Street Hotel, on Valencia between 18th and 19th street, after the earthquake, but before the fire.Selection 10a: top floor of the Palace Hotel on Market Street in San Francisco, California reported by James W. Byrne [Barker]I got out of bed and found that the rocking floor made walking rather wobbly; but I was able to get into my overcoat and slippers, and run out into the corridor to go to my mothers room. When I reached her door she was in the act of opening it; her intention being to go to my room to find me. She had hurriedly thrown on a wrapper, but was scarcely better clad than I was in my overcoat and pajamas. Some other guests of the hotel were popping out of their rooms at this time, and most of them were attired more airily than we were. But the earthquake seemed to have ceased, and my mother decided to remain in her room and complete her toilette before going downstairs.

Selection 10b: courtyard of the Palace Hotel on Market Street in San Francisco, California reported by Frank Louis Ames [Barker]Inside the Palace, the office lights were bright and inviting. Even as I was looking in at them the tall palms in the courtyard that was part of the hotel lobby began to sway. At first I thought it was an optical delusion. But then the ground felt as if it were sinking under my feet.I turned instinctively to the tall buildings of the Chronicle and Call. The clock in the Chronicle tower seemed to waver, and the Calls skyscraper, anchored as it was hundreds of feet in the ground, simply rocked. Cornices and bricks came tumbling around me.I stepped into an alcove for safety. It seemed as if the very earth were reeling.As I stepped from the alcove, the pavement simply went in waves under my feet. I ran for the Chronicle building because, judging from the way the bricks were falling from the Palace I believed that it was about to fall. The quake ran from east to west and the cobblestones of market Street seemed alive. Every one of them was moving and the street car rails were twisted from their places.Selection 11: a room at the Faculty Club at the University of California in Berkeley, California reported by G.K. Gilbert [Jordan]It is the natural and legitimate ambition of a properly constituted geologist to see a glacier, witness an eruption and feel an earthquake.When, therefore, I was awakened in Berkeley on the eighteenth of April last by a tumult of motions and noises, it was with unalloyed pleasure that I became aware that a vigorous earthquake was in progress. The creaking of the building, which has a heavy frame of redwood, and the rattling of various articles of furniture so occupied my attention that I did not fully differentiate the noises peculiar to the earthquake itself. The motions I was able to analyze more successfully, perceiving that, while they had many directions, the dominant factor was a swaying in the north-south direction, which caused me to roll slightly as I lay with my head toward the east. Afterward I found a suspended electric lamp swinging in the north-south direction, and observed that water had been splashed southward from a pitcher.In my immediate vicinity the destructive effects were trivialSelection 12: Point Reyes Station, California reported by G.K. Gilbert [Lawson]The village at the railroad station of Point Reyes is about 0.5 mile northeast of the fault-trace, and stands on a low bench of apparently firm ground.The schoolhouse, a 2-story building standing on a brick foundation wall, was shifted 2.5 feet to the south. A stone building used as a store was thrown downThe hotel barn was shifted 20 inches toward the south and a few other buildings were shiftedBrick chimneys were generally thrown down. A large shed was wrecked. In all buildings furniture was shifted, objects on shelves were thrown down, dishes were brokenAn engine and three cars standing on the track were overturned to the southwest. A long wood-pile was thrown down toward the southwest.

An engine and three cars standing on the track were overturnedSelection 13: Bodie, California reported by E.B. Brooks [Lawson]The shock was perceptible; some clocks [stopped]. It was noticed by occupants in some 2-story buildings, but was not generally felt.

Selection 14: Point Arena, California reported by E.S. Larson [Lawson]All brick buildings in the place had completely collapsed, and in the opinion of the residents it was deemed wisest to replace them by frame structures. All brick chimneys had fallen; plaster had cracked and fallen wholesale fashion, especially on the lower floors, and many shop windows and smaller panes were broken. A few wooden buildings suffered from the collapse of their underpinning.Selection 15a: Redding, California reported by L.F. Bassett [Lawson]Mr. Bassett was indoors, squatted on his toes in front of a stove lighting the fire when the shock came. He felt no tremulous motion and only one principle disturbance, which lasted several seconds. There was a slight swaying motion of the house for perhaps 10 seconds, and this was strongest at the beginning. The motion tended to throw one to the north. No objects were overturned, but the windows rattled a little. A rumbling noise preceded and followed the shock, which he ascribed at the time to a passing train; but there was no train due at that time.Selection 15b: Redding, California reported by B. Macomber [Lawson]The shock was not intense enough at Redding to move loose objects. In a few cases clocks were [stopped]. The shock was felt violently and many people were awakened by it. It was preceded at a very slight interval by a roar. Up to the moment that the most violent part of the shock struck the house, I was under the impression that the sound and vibration were both caused by a train passing.

Name _______________________

Period ______

Answer Sheet for Earthquake Intensity ActivitySelection Intensity

Reasons you gave the selection that intensity1 ______

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10a and b ______

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15a and b ______