Applications of the Joint Epicenter Determination Method
TELEDYNE GEOTECH ALEXANDRIA VA SEISMIC DATA LAB
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Joint Epicenter Determination JED, a least squares method of estimating earthquake epicenters and station corrections, is shown to be unstable for some teleseismic nets in that estimated locations and station corrections change substantially when a few readings from a large set are omitted. Locations are also shown to change if different travel-time tables are used. The result is established both for a North American and a world-wide net, using an epicentral region ranging 30 degrees along the Aleutian Islands. If the suite of epicenters were to be spread over the earth, a case not discussed in this study, JED may be stable. However, in that case it would apprear to be impossible, using JED, to discover the corrections to the average earth travel time tables caused by geology at the source or in the mantle. Thus JED could not be used to determine station corrections which would result in teleseismic locations accurate to 2-4 kilometers.