The Application And Research Of The Earthquake Relative Location In Some Respects

The double difference relative location approach (DD) is applied and investigated in this paper in the following three respects.Firstly, double difference method is used to relocate Ludian earthquake sequence occurring from August to December in 2004 and in Yunnan province located in the "north and south earthquake belt" (NSEB), and the more accuracy relative locations are obtained. We developed a set of methods in data processing and result analysis with the ability to use the real time data from temporary seismic network monitoring the NSEB and to relocate the moderate and strong earthquake sequence. The more accurate earthquake locations provide us basic information to analysis seismic activity and estimate the earthquake trend in NSEB.Secondly, the effect of data recorded at the nearby stations on DD algorithm is investigated in this paper by theoretical analysis, numerical modeling and actual data computation. The difference is found between DD and the master event technique, multiplet relative relocation as well as the hypocentroid decomposition (HDC), the condition that span between events is much less than the event-station distance is must be satisfied for latter but not for former when the velocity lateral heterogeneity is not so strong. The data recorded at nearby stations allow us to obtain the more accurate absolute earthquake position and depth estimation.Thirdly, a double difference relative location program using the regional earthquake and teleseismic data is developed, where theoretical travel time from event to station at regional and telseismic distances is calculated by IASPEI91 Earth model. The Jiashi earthquake sequence occurring in 2003 and Xinjiang province is relocated by the program, and the result seems more reasonable.