Two Practical Methods of Earthquake Locating:
Joint Hypocenter Determination and Double Difference
Speaker: Bor-Kuan Li
Abstract
These papers present two kinds of algorithms of earthquake location. Both these algorithms are in order to minimize the effects of the travel-time anomalies, causing by variation of medium velocity, and make the travel-time have direct correlation with the distances from earthquakes to stations.
The main notion of Joint hypocenter determination (JHD) is making one event in the group of earthquake or explosion as the calibration event, and its hypocenter will be restrained to its known location. By comparing to the calibration event, all events in the group are delayed by the same amount.
Double Difference make each event coupled to its neighbors as a event pair, and the method incorporates ordinary absolute travel-time measurements and cross-correlation P and S wave differential travel-time measurements.
In this two dissertation, we can catch on the ways to minimize the effects of velocity variation of lateral layer, even we only use the one-dimensional velocity mode. In conclusion, we would see the achievements of two algorithms respectively in western Venezuela and northeastern Colombia(JHD) and The Northern Hayward Fault in California (Double Difference).
Reference
James W. Dewey (1972) Seismicity and Tectonics of Western Venezuela. Bulletin of the eismological Society of America. Vol 62, No. 6, pp 1711-1751.
Felix Waldhauser ,William L. Ellsworth (2000) A Double-Difference Earthquake Location Algorithm: Method and Application to the Northern Hayward Fault, California. Bulletin of the Seismological Society of America, Vol 90, 6, pp 1353-1368.