Abstract
ATTEMPTS have been made recently1–3 to revise the Jeffreys–Bullen (J.–B.) travel time tables4 and Herrin et al.5,6 have published a set of tables which are intended as a new standard. But these new tables fail to predict the P travel times for some explosions with known epicentres and origin times. Most notably, the P waves generated by the Longshot (Aleutian Island) explosion arrive earlier than predicted at stations to the north of the Aleutian arc and later than predicted at stations to the south. This bias in the P wave travel time results in a mislocation by about 25 km when the epicentre of Longshot is computed by standard methods. The cause of this travel time bias is usually attributed to the effects of structure beneath the Longshot firing site—and the term source bias has been proposed by Herrin and Taggart7 to describe the phenomenon.
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References
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LILWALL, R., DOUGLAS, A. Quest for a P Travel Time Standard. Nature 222, 975–977 (1969). https://doi.org/10.1038/222975a0
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DOI: https://doi.org/10.1038/222975a0
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