The Earthquake’s Relative Location Algorithms Effected by Data Recorded at Nearby Station

Based on the primary theory of location, it is found that the data recorded at nearby stations are applicable in double difference relocation algorithm, but not in other relative location algorithms. Equation derivation and simulated calculation demonstrate that double difference algorithm allows to get the absolute locations of earthquakes with certain accuracy by using the nearby stations records. The errors of relative location become larger when using the nearby station records alone than that using the distant station records. Combining the nearby and distant station records, the best locations are obtained. In the case that hypocenter depth is far less than the epicenter distance without depth phases available, only the relative epicenter distribution could be obtained accurately by double difference method, the depth determined would be not stable. The relocation test of a part of aftershocks in Jiashi earthquake sequence verify the effect of nearby station records on the double difference algorithm mentioned above.