The EventRate Class - geoscience-community-codes/GISMO GitHub Wiki

The EventRate class is for making plots of:

  • number of events per unit time
  • energy release / cumulative magnitude per unit time

For a quick plot of earthquakes per hour, we create an eventrate object and then plot it. Here our binsize is 1/24 days, i.e. 1 hour.

>> eventrateObject = catalogObject.eventrate('binsize', 1/24);
>> eventrateObject.plot()

images/eventrate.plot.png

Now let's change to a smaller bin size of just 20 minutes:

>> eventrateObject = catalogObject.eventrate('binsize', 20/1440);
>> plot(eventrateObject);

images/eventrate.plot.2.png

Note that eventrateObject.plot() and plot(eventrateObject) do exactly the same thing. The first is the object-oriented style OBJECT.METHOD(INPUT PARAMETERS), the second is the functional style FUNCTION(OBJECT, INPUT PARAMETERS). We could just as easily do eventrate(catalogObject, 'binsize', 20/1440) too, but the object oriented style is preferable.

Event rates for overlapping time windows

Sometimes it is desirable to compute event rate metrics for sliding - i.e. overlapping - time windows. This is easily done with the 'stepsize' parameter. If omitted, stepsize defaults to the binsize - which is the length of the time window. So in the previous example, both binsize and stepsize were 1.0 hours. But we can just as easily compute an eventrate object for the same Events object with a binsize of 1 hour, and stepsize of just 5 minutes.

>> eventrateObject = catalogObject.eventrate('binsize', 1/24,  'stepsize', 5/1440);
>> eventrateObject.plot()

images/eventrate.plot.3.png

Plots of other event rate metrics

>> eventrateObject.plot()

is actually equivalent to typing:

>> eventrateObject.plot(), 'metric', 'counts');

The full list of metrics that can be plotted are:

  • counts
  • mean_rate
  • median_rate
  • cum_mag
  • mean_mag
  • median_mag
  • energy

All of these are properties of an eventrate object except for energy, which is computed from cum_mag on-the-fly. Several can be plotted at once in subplots of the same figure using a cell array:

>> eventrateObject.plot('metric', {'mean_rate'; 'median_rate'; 'mean_mag'; 'cum_mag'});

images/eventrate.plot.4.png

Or they can of course be plotted in separate figure windows:

>> eventrateObject.plot('metric', 'mean_rate')
>> eventrateObject.plot('metric', 'median_rate')
>> eventrateObject.plot('metric', 'mean_mag')
>> eventrateObject.plot('metric', 'cum_mag')

(Output not shown)

These are the same metrics, binsize and stepsize used by the [AVO swarm tracking system] (http://www.aeic.alaska.edu/input/west/papers/2009_srl_thompson_redoubtSwarms.pdf).

Two more simple plot types are:

>> eventrateObject.helenaplot()

images/eventrate.helenaplot.png

and:

>> eventrateObject.pythonplot()

images/eventrate.pythonplot.png