Earthquake Machine Mechanical Modeling to Increase Student Understanding of Complex Earth Systems Most of you are probably covering strike-slip faults and the elastic rebound theory as part of your classes. Today we will use a mechanical model to reinforce the concepts you of the Elastic Rebound Theory as well as exploring earthquake prediction first hand. Michael Hubenthal - IRIS Consortium

Objectives (SWBAT) Explain earthquakes as a part of the natural Earth System Describe global trends for Earthquake occurrence and magnitude Interpret a Gutenberg Richter plot (Frequency vs. Magnitude) Critically analyze an argument Describe the importance of sharing science results with peers in the science process

What is an Earthquake? Write down a definition for an earthquake Keeping the centennial theme in mind, this was a question not well understood at the time of the turn of the century. How would you modify the model so that it no longer stored energy? How do you think your modification would impact the models operation? What does this say about rocks? What aspects of the model do you think could be “measured” quantitatively? Describe how we could do this. In small groups, discuss your definitions of an earthquake and create a consensus definition

Exploring with a model…

EQ Machine - Lite Bulk of the Plate Top View B C Elastic Properties of Earth Materials Plate has Constant Velocity Here Edge of the Plate

What did you observe? How would you alter your definition, to accommodate these observations?

Elastic Rebound Theory Distant forces cause a gradual build up of stress in the earth over tens or hundreds or thousands of years, slowly distorting the earth underneath our feet. Eventually, a pre-existing weakness in the earth--called a fault or a fault zone--can not resist the strain any longer and fails catastrophically.

http://quake.wr.usgs.gov/research/deformation/modeling/animations/index.html

Key Concepts Elastic materials can store potential energy Earth materials are elastic though they may not seem it within our temporal and thermal scales The Earth’s plates are constantly in motion though we can not perceive this without instruments

Studying Earthquake Recurrence

Developing arguments…. How many beads are in the box????

Exploring with a model…

Seismic Moment Mo = fault length x fault width x displacement x rigidity Moment Magnitude = Mw = log Mo/1.5 – 10.7

Visualizing magnitude with the model B Seismic Moment (Mo) is a measure of the size of an earthquake based the physical characteristics of the fault and can be determined either from seismograms or fault dimensions. Mo = L x W x D x  or Length x Width x Displacement (Slip) x Rigidity Moment Magnitude (Mw) based on the concept of seismic moment where constants in the equation have been chosen so the moment magnitude scale correlates with other magnitude scales. Mw = log Mo/1.5 – 10.7 Seismic Moment Mo = fault length x fault width x displacement x rigidity Moment Magnitude = Mw = log Mo/1.5 – 10.7

Group A Group B “There are long periods of quiet between earthquakes” “Most earthquakes are huge, deadly and destructive events” Develop an argument* either for or against this statement based on your experimentation with the earthquake machine. *Note: You must base our argument on minimally 30 events

“There are always long periods between earthquakes.”

“All earthquakes are huge, deadly, and destructive events”

Components of Prediction When? Where How Big?

Using the data you have collected argue either for or against the following statement… “There hasn’t been an earthquake in a long time; therefore the next one must be huge.”

Time Predictable Slip Predictable Stress Characteristic Slip Time

Calaveras Fault Data (Bufe et al., 1977)

For a full description of the EQ Machine and a multi-period lab please visit: http://www.iris.edu/edu/lessons.htm

Young students ideas (Ross and Shuell, 1991) (Tsai, 2001) A study of US students in grades k -6 found the most frequent student responses to the question “What is an earthquake?” was the shaking or trembling and the splitting open/cracking of the ground When asked about the causes of earthquakes 75% of K-3 and the over 50% of students in grades 4-6 responded that they did know. British students aged 11 to 14 suggested that they are caused the earths surface to cracking. the majority of Taiwanese 5th and 6th grade students held non-scientific, supernatural views for the causality of earthquakes. (Tsai, 2001) (Leather, 1987)

Conceptual shift at age 14? Leather also noted that beyond the age of 14 there was a sharp decline in students’ alternative conceptions,. Instead many students related seismic activity to movement along plate and fault boundaries. open-ended survey of sixty-three 9th grade students in Binghamton, NY revealed that nearly all students defined earthquakes as an interaction of plates or fault boundaries. This conceptual shift appears to hold as the vast majority of students enrolled in geology 101 courses still associate the movement of tectonics plates with earthquakes (Barrow & Haskings, 1996; DeLaughter et al., 1998; Libarkin et al., 2005))

Location of EQs & relation to plates Leather (1987) found that almost half of the British 11 to 14 year olds sampled thought that earthquakes occurred in hot countries. This was later substantiated by a small study conducted by Sharpe et al. (1995). The Delaughter et al. study displayed this relationship more clearly, finding that while the vast majority of undergraduate students used plates or plate tectonics in their responses about what an earthquake is, but when asked to explain why earthquakes occur where they do, only 41% of students gave responses indicating that the presence of faults or plate edges in the vicinity of their chosen location was the reason (1998). In the United States a wide ranging study of over 1000 undergraduates and school children aged 5-18 found that 36% thought that *Chicago was unlikely to be affected by an earthquake (Philips, 1991; Schoon, 1992). * It should be noted that while not pointed out in the literature, the Schoon study may be a bit of an exception. Chicago’s seismic hazard is a special case, as the risk is associated with the intraplate New Madrid seismic zone. Since the causes of intraplate events are not completely understood by the research community it may be unfair to include this study as evidence of students lack of understanding of earthquakes.

Centennial Connections During the 1906 event the earth on one side of the fault had slipped compared to the earth on the other side of the fault by up to 21 feet (7 m). Steinbrugge Collection of the UC Berkeley EERC

After studying the fault trace of the 1906 earthquake and regional surveys (pre/post event), Harry Fielding Reid, postulated that the forces causing earthquakes were not close to the earthquake source but very distant.

Event #  Time Displacement Examine page one of your data set and develop a prediction for the 26th event based on the previous 25 events.

Seismicity of the EQ Machine - 67 “Years”

Seismicity of the EQ Machine - 163 “Years”