Tuesday, July 9, 2013

Support Vector Machines

For a proof of concept, we tried to train a support vector machine to distinguish between quiet time and quake time periods. The results are promising!

The support vector machine was trained on 7 different earthquake for a set of stations for the quiet time and the quake time. Currently, the first pick is considered as the boundary between the quiet time and quake time periods. A set of random data points- 3 random stations for each quake for both quiet time and quake time was chosen as the training data.

We had a dataset of 2240 data points in all.

Results:

True positive: Correctly predicted quake time as quake time
True Negative: Correctly predicted quiet time as quiet time
False Positive: Incorrectly predicted quiet time as quake time
False Negative: Incorrectly predicted quake time as quiet time

Training Data:
The Support Vector Machine seemed to be able to fit the training data well enough.
True positive: 78.93%
True Negative: 84.19%
False Positive: 15.81%
False Negative: 21.07%

Test Data:
The Support Vector Machine was also able to correctly classify the test data.
True positive: 80.00%
True Negative: 88.57%
False Positive: 11.43%
False Negative: 20.00%

The idea of detecting earthquakes by capturing the differences in the frequency domain properties, seems logical now. We will try changing a few parameters to figure the best possible way for the classification to get optimal results.

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