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Earthquakes The Earth is covered by tectonic plates which slide past or over/under one another. The sliding motion is jerky because of friction. The interface jams and stress builds up. The stored elastic energy is suddenly released in an earthquake, which is usually followed by aftershocks. Gutenberg-Richter Law log10 N = a − bM M is the magnitude of the quake M ∼ log(M0) M0 is the seismic moment M0 = µSD D is the displacement of the fault in the quake S is the area of the fault µ is the shear modulus or rigidity of the rocks in fault N (M ) is the number of quakes with magnitude > M Outline of quake.py path to gnuplot executable define a function to linear fit x-y data without error bars data downloaded from http://neic.usgs.gov/neis/epic/epic_global.html store event data in a python dictionary object with key = magnitude starting in column 50 value = number of events with this magnitude x data = M values sorted in increasing order y data = log10(N ) where N = number of events with magnitude >= M perform a least square fit write histogram data to file Gnuplot commands to plot histogram create a script file and call Gnuplot Python Dictionaries in quake.py Earthquake date are stored in a dictionary with magnitude M as key and number of quakes with this magnitude as value Read M from the current event line in the data file Attempt to increment the number of quakes with this M If the attempt fails, handle the exception Python dictionary tutorial: http://docs.python.org/tutorial/ datastructures.html#dictionaries Python exceptions tutorial: http://docs.python.org/tutorial/errors.html Very important: N (M ) in the Gutenberg-Richter law is NOT the number of events with magnitude M