A reason to study earthquakes
The Jewel of the West loses its lustre
In this case study...
We explore the 1906 earthquake that devastated San Fransisco, how the disaster was made worse by human action in the days after the quake, and how it contributed to the science known as seismology
Historical case study by: Dr. Glenn Dolphin
Introduction
In the United States, the city of San Francisco, with the promise of gold, grew in prominence and population (Dalessandro, 2006; James, 1911). The city’s location on the coast of the Pacific made it an attractive destination for those seeking wealth, and during those last years of the 1800s, the population doubled almost monthly. In fact, by the early 1900s, a full 25% of the US population living west of the Rocky Mountains, were located in or near the city limits of this coastal city. It was clearly thriving, with 17 cable car lines, 37 banks, and three opera houses. The city rivalled New York City for imports and exports, and was referred to as The Jewel of the West, and Paris of the Pacific. Some noteworthy historical figures got also got their start there. A German immigrant saw the need for miners to have durable work clothes and began cutting cotton tarps and dying them blue. His name was Levi Straus. In the 1850s, Henry Wells and William Fargo founded a financial institution that today still bears their names. They conducted business by stagecoach and by ship, and by the early 1900s they maintained thousands of offices countrywide.
During the early morning hours of April 18th, 1906, most people were sleeping, though some were just heading home after a full night of revelry,when the earth began to shake violently and continuously for almost a minute. Later classified as a magnitude 7.8 earthquake, the shaking caused several buildings in the city to collapse and started dozens of fires. Most of these were due to underground gas lines that broke during the earthquake. As well, several water mains also broke, adding to the havoc in the city. Since two of the three major lines were damaged, fighting the fires through out the city was nearly impossible.
The Damnedest, Finest Ruins
If possible, watch this compelling documentary on the 1906 earthquake before reading further
Two Witnesses
Two American authors were in San Francisco at the time of the quake and later wrote about their experiences. The backgrounds of these two gentlemen are clearly quite different and as you can imagine, their interpretation of the events of the morning of the 18th April, 1906 reflected their diverse backgrounds.
Proceed to Activity 1
Think Question: Briefly describe the similarities between how Jack London perceived this event with how William James perceived the event.
Think Question: Discuss why these authors may have differed in their perceptions of the same event?
Panorama of San Francisco after earthquake of 1906
Investigating Earthquakes
The devastation to the city increased as the Mayor of San Francisco ordered military and law enforcement personnel to use dynamite to try to extinguish burning areas. After nearly a week of trying to contain the disaster, the fires eventually did subside, but about 80% of the city had either burned down or been blown up, and some 3,000 people were dead. The total cost of the disaster came to about 400 million US dollars, a price tag equivalent to the entire national budget at that time.
While people of the period had plenty of experience with earthquakes, no one really knew what they were or what caused them. Given the huge cost of this particular event, not to mention the loss of life and the tremendous disruption in commerce, the Governor of California, George C. Pardee, appointed Andrew C. Lawson as the head of the State Earthquake Investigation Commission (later known as the Lawson Commission). Lawson, a professor from the University of California, Berkley, had with him eight scientists from other institutions—such as various observatories, the University of California, Johns Hopkins University and the still quite young United States Geological Survey. Theirs was a historic mandate, as it was the first time the government had commissioned a scientific investigation. Though the state government did not have the money to fund the investigation (see below), this government-commissioned investigation was the origin of such well-known present day institutions as the National Science Foundation, and the National Institutes for Health, which now do fund scientific investigations with public (taxpayer) money. Until this occurrence, scientific investigations had been primarily directed and subsidized by private funds.
Think Question: If you were Lawson, and need money to support investigation of this huge disaster, where would you go to get money? How would you justify your expenses?
Think Question: What kinds of strategies would you employ to investigate this massive earthquake?
In his book, California Earthquakes: Science, Risk, and the Politics of Hazards (2001), Carl-Henry Geschwind (2001) wrote about the findings of this commission. The details are startling in their clarity and insight into the cause and implications of this unexpected and massive geological event:
Carl-Henry Geschwind's findings of the commission
Tear in the ground outside San Fransisco
The ground had broken open for more than 270 miles along a great fault—the San Andreas rift. The country on the east side of the rift had moved southward relative to the country on the west side of the rift. The greatest displacement had been 21 feet about 30 miles northwest of San Francisco
- William Rubey
Think Question: Given the preliminary results from this report, if you were Governor Pardee, what would be some of the issues you would want to start considering to ensure the safety of the citizens of California?
Elastic Rebound Theory
Harry Fielding Reid
One of the commission’s members was Harry Fielding Reid (1859–1944), a professor from Johns Hopkins University in Baltimore, Maryland. While Reid had been born in Baltimore, he was schooled in Switzerland where he took an interest in the science of glaciers. In 1886, after completing his PhD in geophysics from Johns Hopkins, he became a professor of mathematics in Chicago. However, he soon got another appointment at Johns Hopkins, first as a physics professor and soon thereafter as a professor of geological physics. He turned to his interest in glaciers and went on to develop much of the knowledge we currently have today about glaciers. His interests changed again after being appointed to the Lawson Commission as he began to make great contributions to the discipline of seismology—that is, deformation of the earth’s crust.
In his research, Reid looked at survey data from the previous several decades. During a survey from 1851–1865, markers were set from west to east across the San Andreas fault. These survey markers were again measured in a second survey, that took place around 1890. After the 1906 event, the commission again measured these markers. In essence, what Reid found was that there was relative displacement of about 4 metres on each side of the San Andreas fault where the earthquake happened, which could be measured for several kilometres away. See “Survey III (1906)” in Figure 1 below. Enigmatically, however, is Reid’s observation that the survey markers in survey II (Figure 1) show a gradation of displacement, from no displacement where the survey line crossed the fault, gradually increasing to a couple of metres several kilometres away.
Based on the survey data across all of the three dates in for which it was collected, including the 1906 earthquake, Reid (1910) made a number of claims. They were as follows:
- The strain, or deformation of the bedrock (seen by the curved path of the survey markers in survey II) decreased farther east and west of the fault line.
- The displacement in the path of survey markers observed in survey III decreases north and south along the fault, away from the epicenter.
- The displacement occurred suddenly, ruling out a gradual compressional or extensional force to cause this pattern of deformation.
- Because displacement was horizontal, the force could not be gravitational. Gravity would be responsible for vertical displacements.
- The Farallon Islands, far west of the event, showed the 6 metres of displacement, but none of the strain.
More about Reid
Want to learn more about Harry Fielding Reid? Read his biographical memoir!
Think Question: Given the data and the reasoning of Reid (above), develop an explanation for the great earthquake of 1906.
Please proceed to Activity 2.
Reid’s interpretation of the data assumed a time when there was no displacement across the fault, as shown in (a) in the graphic below. After the first survey, the ground deformed in response to horizontal displacement; west of the fault the ground moved in a northerly direction, and east of the fault it moved in a relatively southern direction. The deformation accommodated the gradual build up of strain, represented as (b) below; this deformation was like bending a large stick that would bend back to its original configuration once the stress was removed. Eventually, the strain build-up became too much for the strength of the rock and the rock broke along the fault. When the rock broke, the energy in the rock, stored as strain, was released as the rocks elastically rebounded to their normal, unstrained structure, shown in (c). Based on much of these findings, Reid developed his ideas into a very important explanation of seismic activity, which he called elastic rebound theory. This theory remains the cornerstone in seismology for understanding how and why earthquakes happen.
Think Question: According to Reid’s theory of elastic rebound, what is an earthquake? What causes earthquakes to happen? Where do earthquakes get energy?
Think Question: Reid’s life in Switzerland is credited for the development of his interest in the physics of glaciers. How might his experiences with glaciers and their dynamics have influenced Reid’s understanding of the relationship between the deformation in the earth’s crust and the cause of earthquakes?
Think Question: How could Reid’s theory of elastic rebound actually be further tested? Where would be the best places to do such testing?
Think Question: What are the possible implications of this new understanding about earthquake triggers and processes? How could this information benefit those who find themselves living in seismically active areas?
Think Question: Based on the methods and findings of the Lawson Report, where should seismologists concentrate their future research efforts? What types of new investigations should they begin? What data should they start collecting and how should they do this?
Diagram showing Reid’s idea of gradual strain (b), causing deformation in the crust, until it broke and rock on each side of the fault rebounded, releasing stored elastic energy. Source: http://www.iris.edu/hq/gallery/photo/1530 The picture on the right shows actual offset of a fence crossing the San Andreas Fault. Source: http://earthquake.usgs.gov/regional/nca/1906/18april/reid.php
In discussing the history of the San Francisco earthquake of 1906, Lubick (2006) wrote the following:
Activities
Understanding earthquakes
Use the following activities to engage your students throughout. See the cues in the case study which indicate at which point in the readings to start which activity.
Personal accounts of the 1906 San Francisco earthquake—Read the two personal accounts of the 1906 San Francisco earthquake by Jack London and William James, at the links noted above. On the Venn diagram provided below, record the similarities and the differences between how each of them perceived the events during and after the earthquake.
- Using one block and one rubber band (to start), determine the different forces at play within the system. Make a sketch that demonstrates how the system behaves as you pull the rubber band and the block moves. You can draw a force diagram here. Also create a table that describes all the forces, and other possible variables, at work. Include in the table which ones you can control and which ones you cannot. Begin to change different variables and see how the system responds to such changes. Make notes to this effect and add the information to your original diagram, or create a new diagram (or diagrams) to illustrate the changing of the variables.
- Add a second block to the set up (Figure 2). Test some of the variables again. Make notes as to how the system has changed and how it has not changed.
- After having explored the earthquake machine for some time, develop a question that you can investigate within the constraints of the machine. Write procedures for your investigation. Set your variables and record all observations as diagrams and any numeric data within data tables. When finished, make a general claim and support it with evidence from your data.
- Describe how the system would behave if you were to replace each rubber band with 1. a piece of string, and 2. A piece of chewed gum (eew!), warm taffy, or silly putty.
- The system or wood blocks and rubber bands is a model called the earthquake machine. Discuss (in general) why we use models in science. Describe some other instances where models are used in a scientific manner.
- The use of models comes from being able to map the aspects of the model (the source) to aspects of the real world (target). Taking a look at your analysis of the earthquake machine, try to map (transfer) various aspects/variables/forces of the model to analogous aspects of the real world. It would be helpful to make observations of the “marble tongs” and the spring and ball molecular model when mapping the model onto reality.
- Models in science are developed for a particular purpose, usually to focus on or emphasize a particular aspect of a phenomenon or system of phenomena. As such, they have strengths ( i.e. they convey ideas, or behave well in the context of a particular aspect of a system being studied). However, they also have limitations ( i.e. circumstances where the model does not behave or convey ideas very well concerning other aspects of the system being studied). List at least two strengths and two limitations of this particular model and discuss why it is you think each is a strength or limitation.
- Describe in your own words, and based on the model, what an earthquake is and what causes it. List some places on earth that you would go to try and test this model for accuracy, and explain your choices.
- If you wanted to eliminate “earthquakes” from the earthquake machine, in what ways would you change the model? How would these changes translate into the “real world”? In other words, what would change in nature to match the change you made to the model?
- Ask students:
- What is an earthquake?
- What causes earthquakes?
- Allow for discussion of possible answers.
- Show some footage of different effects of earthquakes
- Japan EQ seeps - https://www.google.ca/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=japan%20earthquake%2C%20seeps
- Buildings shaking - https://www.youtube.com/watch?v=3Cjz3JFxMPc
- Buildings shaking - https://www.youtube.com/watch?v=woxqjkSMLpM
- Earthquake security camera footage -https://www.youtube.com/watch?v=RvQ8GQbWa10
- Northridge event - http://video.nationalgeographic.com/video/earthquake-montage
- Haiti event 2010 (7.0) (long, pick a few spots) - https://www.youtube.com/watch?v=4770QrLTgHE
- Mention that today there are organizations United States Geologic Survey (USGS) Earthquake hazards program (http://earthquake.usgs.gov/) and its global seismic monitoring program (http://earthquake.usgs.gov/monitoring/gsn/) and Incorporated Research Institutes for Seismology (IRIS) (http://www.iris.edu/hq/) with their seismic monitor (http://ds.iris.edu/seismon/), that monitor, help plan and work at predicting events to help mitigate the hazards associated with earthquakes. This case will help us understand the origin of systematic research into the origin and hazards associated with earthquake occurrence.
- Begin the case with a description of San Francisco, California in the last half of the 19th century. Also utilize the documentary: “The Damnedest Finest Ruins” for clips or watch the whole thing if time permits (https://www.youtube.com/watch?v=mvve8YiYGSo). It is important to build up the perception of a city flourishing; growing quickly in terms of population, economy, building, and trade. It all comes to an end in about a minute due to an earthquake.
- Have students read the two personal accounts of the 1906 earthquake; one by American Novelist, Jack London (http://london.sonoma.edu/Writings/Journalism/), the other by American philosopher and psychologist, William James (http://grammar.about.com/od/classicessays/a/WJamesEarthquake.htm). You can have students read portions to the class. If time permits, allow students to read up on both James and London to learn who they are as people and how their backgrounds might influence how they interpret the event as they recorded it.
- Show some pictures of the devastation.
- Gallery of photos of San Francisco event (M7.8) - http://galleryhip.com/san-francisco-earthquake-1906-in-color.html
- Images of San Francisco event - http://www.eas.slu.edu/eqc/eqc_photos/1906EQ/1906thumb.html
- There have been other large US earthquakes but none have had either the size of scope (in terms of destruction and economic impact). Have students compare and contrast these events with the Event in San Francisco.
- Charleston, South Carolina, 1886 (M7.3) - http://earthquake.usgs.gov/earthquakes/states/events/1886_09_01.php
- New Madrid fault zone, 1811-1812 (M7.5, M7.3, M7.5) - http://earthquake.usgs.gov/earthquakes/states/events/1811-1812.php#february_7
- Suggest to students they are in the California’s Governor’s mansion. Once the hazard has ended and people start to think about rebuilding the city, what do you do to try to prevent this type of catastrophe from happening again?
- Professor A. C. Lawson Chairman of Geology at University of California becomes the head of a group of scientists who are doing work to study different aspects of the earthquake. About 20 other researchers are on the commission. Pose question to students: What are some of the strategies the commission should adopt to gain the most useful data for understanding this earthquake and help mitigate similar damage from possible future events? Give a rationale for your strategies. This type of investigation will require funding. Who do you look to in order to pay for the investigation? How do you approach them?
- Implement Activity 2, the Earthquake Machine
- It is worth mentioning after the activity that Reid was an important glaciologist prior to becoming a seismologist. With this background may have come the experience of measuring the displacement of slow moving bodies. Also, the dynamics of brittle ice, deforming elastically before cracking (creating “ice quakes”) may have been foundational to Reid’s ideas of the gradual build up of stress in the crust until failure released energy in the form of an earthquake.
References
- Dalessandro, J. (Writer). (2006). The damnedest, finest ruins - episode 601. In J. Dalessandro & R. S. Burton (Producer), Truly California. Napa, CA: KQED.org.
- Geschwind, C.-H. (2001). California earthquakes : Science, risk, and the politics of hazard mitigation. Baltimore, MD: Johns Hopkins University Press.
- James, W. (1911). On some mental effects of the earthquake. In H. James (Ed.), Memories and studies (pp. 207-226). London ; New York: Longmans, Green.
- London, J. (1906). Story of an eyewitness: The San Francisco earthquake. Collier's Weekly, p. http://london.sonoma.edu/Writings/Journalism/.
- Lubick, N. (2006). Seismology: Breaking new ground. Nature, 440(7086), 864-865. doi: 10.1038/440864a
- Reid, H. F. (1910). The California earthquake of April 18, 1906: The mechanics of the earthquake Report of the state earthquake investigation commission in two volumes and atlas (Vol. II). Washington, D.C.: Carnegie Institution of Washington.