Earthquake Machine, part 2 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. Developed by Michael Hubenthal - IRIS Consortium

Objectives 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

Studying Earthquake Recurrence 3

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

Relationship of slip to magnitude 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 = fault length x fault width x displacement x rigidity 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 μ 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 Moment Magnitude = Mw = log Mo/1.5 – 10.7 In earthquake machine, this means magnitude is directly related to fault displacement 6

#1 #2 Extra credit “There are long periods of quiet between earthquakes” #1 “Most earthquakes are huge, deadly and destructive events” #2 “There hasn’t been an earthquake in a long time; therefore the next one must be huge.” Extra credit Develop an argument either for or against one statement based on your experimentation with the earthquake machine.

“There are always long periods between earthquakes.”

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

Time Predictable Slip Predictable Stress Characteristic Slip Time

Calaveras Fault Data (Bufe et al., 1977)

Seismicity of the EQ Machine - 67 “Years”

Seismicity of the EQ Machine - 163 “Years”

Summary There are many more small earthquakes than large earthquakes There are more short time periods between earthquakes than long time periods In the earthquake machine, the longer since the last earthquake, the larger the earthquake is likely to be This isn’t usually true in the Earth