Journal
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
Volume 123, Issue 6, Pages 5120-5129Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2017JB015251
Keywords
phase picking; deep learning; focal mechanisms; real-time seismology; machine learning
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Funding
- Gordon and Betty Moore Foundation
- NSF [EAR-1550704]
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Determining earthquake hypocenters and focal mechanisms requires precisely measured P wave arrival times and first-motion polarities. Automated algorithms for estimating these quantities have been less accurate than estimates by human experts, which are problematic for processing large data volumes. Here we train convolutional neural networks to measure both quantities, which learn directly from seismograms without the need for feature extraction. The networks are trained on 18.2 million manually picked seismograms for the Southern California region. Through cross validation on 1.2 million independent seismograms, the differences between the automated and manual picks have a standard deviation of 0.023s. The polarities determined by the classifier have a precision of 95% when compared with analyst-determined polarities. We show that the classifier picks more polarities overall than the analysts, without sacrificing quality, resulting in almost double the number of focal mechanisms. The remarkable precision of the trained networks indicates that they can perform as well, or better, than expert seismologists.
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