Depth-dependent attenuation in the uppermost inner core from the Taiwan short period seismic array PKP data

Inner core attenuation properties from two spots were examined in detail us ing PKIKP and PKP(BC) phases with a distance range of between 147 degrees a nd 154 degrees as recorded by both the short-period regional seismic array in Taiwan and the broadband stations of the German Regional Seismic Network . The ray paths from the six South American events to Taiwan sampled the in ner core region beneath the eastern part of the northern Pacific Ocean, whi le those from Fiji to Europe reflected the inner core boundary under the we stern part of the northern Pacific Ocean. Results of this study show the de pth-dependent attenuation of Qp beneath the eastern part of the northern Pa cific Ocean from 241+/-21.8 (at depths < 210 km) to 337+/-46.5 (at depths > 270 km) with a weighted mean of 305+/-25.4 within the frequency band 0.5 s imilar to2.0Hz. The average Qp under the western part of the northern Pacif ic Ocean is 160+/-33.5 (0.5 similar to1.5Hz) which is consistent with that previously reported. It is found that Qp under the western part of the nort hern Pacific is clearly lower than that under the eastern part. This discre pancy might be related to regional variations in the uppermost inner core.