Comparison of mid-oceanic earthquake epicentral differences of travel time, centroid locations, and those determined by autonomous underwater hydrophone arrays

摘要

Mid-oceanic interplate earthquakes are difficult to locate accurately because they normally occur far away from land-based seismic stations. Use of water-borne T waves recorded by autonomous underwater hydrophone (AUH) arrays records an order of magnitude more highly accurate regional low seismicity along the north Mid-Atlantic Ridge than the International Seismic Centre (ISC). Even though the physical meaning of an AUH locations is still not well known, AUH's small location errors are important for better constraining mid-oceanic earthquakes. Comparison of such AUH locations with those in ISC and Harvard centroid moment tensor (CMT) location catalog, and relocated ones based on the high-resolution bathymetry and teleseismic P phases, is made in this study. AUH locations are used as a reference to compare the teleseismically determined locations. For large earthquakes with known focal mechanisms, we find that relocated locations agree with AUH ones better than with ISC. We also note that the centroid vectors from relocated epicenters are usually larger than AUH centroid vectors. The relocated epicenters and AUH locations lie in similar azimuthal directions to the associated CMT epicenters. The larger relocated and AUH centroid vectors (than the error ellipses of AUH, CMT, and relocated ones combined) might be explained by the fault rupture process. For smaller events, relocated location confidence ellipses are usually large enough to cover AUH locations and their error ellipses. Overall, the highly accurate AUH locations can be used to confirm the mid-oceanic earthquake hypocenters and seismicity characteristics and for detail studies of the low-level seismicity associated with the plate motions.