Most earthquake location algorithms are based on ray-theory travel-times and thus require as input data the onset times of body-wave phases such as P and S at a number of stations. It is often easy to detect and pick the first P onset times manually since the human eye can identify a change in amplitude or frequency in a signal even in the presence of high noise levels. The picking of S-phase onsets is more difficult because these onsets are often emergent and buried in the P coda, though at very short ranges the S onset can be impulsive...

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