Inner Core Differential Motion Confirmed by Earthquake Waveform Doublets
Jian Zhang(Lamont-Doherty Earth Observatory), Xiaodong Song(Lamont-Doherty Earth Observatory), Yingchun Li(Lamont-Doherty Earth Observatory), Paul G. Richards(Lamont-Doherty Earth Observatory), Xinlei Sun(Lamont-Doherty Earth Observatory), F. Waldhauser(Lamont-Doherty Earth Observatory)
Cited by 147
Abstract
We analyzed 18 high-quality waveform doublets with time separations of up to 35 years in the South Sandwich Islands region, for which the seismic signals have traversed the inner core as PKP(DF). The doublets show a consistent temporal change of travel times at up to 58 stations in and near Alaska, and they show a dissimilarity of PKP(DF) coda. Using waveform doublets avoids artifacts of earthquake mislocations and contamination from small-scale heterogeneities. Our results confirm that Earth's inner core is rotating faster than the mantle and crust at about 0.3 degrees to 0.5 degrees per year.