5:15 PM - 6:30 PM
[SCG20-P05] A receiver function imaging of the 660-km discontinuity beneath the Ogasawara Islands
Keywords:receiver function, Ogasawara, 660 km discontinuity
We calculate RFs using teleseismic records observed at two broadband stations, a station OGS in Ocean Hemisphere network Project (OHP) and another station OSW in F-net operated by National Research Institute for Earth and Disaster Prevention (NIED), deployed at the Chichijma Island in the Ogasawara Islands. The separation distance of the two stations is 4.6 km. The teleseismic events that occurred during 2006–2014 and 2005–2014 were used for OGS and OSW, respectively. The total number of the collected RFs is 267 (188 at OGS and 79 at OSW). We applied 0.16 Hz low-pass filter to the time-domain RFs, and converted them to depth-domain RFs using the 1D JMA velocity model.
We could image the depth-variation of the 660 from 660 km to 750 km. Most importantly, we found a RF that shows a peak of P660s, and the Ps converted point at a depth of 660 km of the RF is only ~20–30 km in horizontal distance away from the hypocenter of the deep earthquake, which allows us to compare the relative depths of the deep earthquake and the 660. As a result, is seems that the 660 is deeper than the focal depth at least by 50 km, and this fact indicated that the deep earthquake occurred in the upper mantle, but presumably deeper than the surrounding 660 km discontinuity.
We used seismic records observed by F-net operated by NIED, and thank K. Shiomi for kindly providing us teleseismic event data.