Hypocentre determination offshore Eastern Taiwan using the Maximum Intersection method
Résumé
The maximum intersection (MAXI) method, which derives from the master station method(MSM), determines within a 3-D velocity model the absolute hypocentral location based onobserved arrival times. First, the spatial node that better satisfies the arrival time differencescomputed at all station pairs, plus or minus an error tolerance value (in seconds), is definedas the preliminary hypocentral solution (PRED). Second, because PRED depends neither onthe estimate of origin time nor on the residual root mean square (rms), residual outliers areobjectively detected and cleaned out from the original data set without any iterative processor weighting. Third, a statistical minimization (residual rms) is conducted in a small domainaround the PRED node, which results in a unique FINAL solution. The MAXI method is appliedto the determination of earthquake hypocentres (with the proper station correction terms) in thesouthernmost extremity of the Ryukyu subduction zone, where several dense seismic clustersoccur near the seismogenic plate interface. The location of earthquakes, recorded at both theTaiwanese and Japanese networks, is obtained for about a thousand events (between 1992 and1997). The process uses a detailed 3-D velocity model based on multiple geophysical datasources obtained in the junction area between subduction and collision (east of Taiwan). Theearthquake clustering and the significant drop in residual statistics (1.20, 0.80 and 0.35 s,for Taiwanese catalogue, MSM and MAXIM solutions respectively) indicate the accuracy ofthe method, which can be used to routinely determine absolute hypocentre location based onobserved arrival times.
Domaines
Planète et Univers [physics]
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