摘要： •Earthquakes in the southern termination of Mariana Arc are consistently exciting T waves.•Isobaths curvature and earthquake radiation pattern are attributable to T excitations.•Steep offshore slopes and incident rays vertical to local isobaths are primary and secondary roles for efficient receiver-side conversions. We used broadband stations in Taiwan and on the Ryukyu Arc islands to investigate T waves induced by earthquakes in the Izu-Bonin-Mariana subduction zone. Of the 48 earthquakes that took place in 2005, 17 earthquakes exhibited T-wave signals consistent with predicted arrival times at stations. Of theses T-excited events, 13 were located in the South Mariana Arc, where the isobaths exhibit strong concave curvature, and were predominantly of normal faulting type. The energies of observed T waves were used quantitatively to evaluate the relative efficiency of receiver-side acoustic–elastic conversions by Gamma calculations. Results show that the steep slopes of offshore bathymetry together with nearly perpendicular angles of back azimuth relative to local isobaths are suitable conditions for T waves observations. In 2010, two clusters of repeated moderate earthquakes in the north and south ends of the Mariana Arc displayed stark contrasts in terms of T-wave excitations despite their normal faulting type. Examining of this discrepancy indicate that a specific curvature together with a specific radiation pattern accounts for the frequent excitations of T waves from shallow earthquakes in the South Mariana Arc. 出版者： Elsevier Ltd 出版日期： 2015-02 出處： Journal of Asian earth sciences, 2015-02, Vol.98, p.50-60 資源來源： ScienceDirect 版權： 2014 Elsevier Ltd 識別號： ISSN: 1367-9120 識別號： EISSN: 1878-5786 識別號： DOI: 10.1016/j.jseaes.2014.10.033
