Jan 18, 2018
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. 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 Earths 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 hasnt 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:
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.Chicagos
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