Ying Zhou Finds 0.2-Second Outer-Core Shifts, Pointing to Vigorous Mixing
Updated
Updated · ScienceAlert · Aug 22
Ying Zhou Finds 0.2-Second Outer-Core Shifts, Pointing to Vigorous Mixing
1 articles · Updated · ScienceAlert · Aug 22
Summary
112 pairs of underground nuclear tests let Ying Zhou track repeated seismic paths and detect outer-core travel-time changes over less than two decades.
Seismic waves arrived about 0.1 seconds faster in 1982-83, 0.15 seconds faster in 1988-90, then 0.15 to 0.2 seconds slower by 1995 versus 1977, indicating the liquid outer core changed over time.
A newly identified wave, PKrKP, reflects within the middle of the outer core, helping isolate that layer from mantle signals by comparison with PP waves.
Zhou argues a southern Pacific anomaly more than 700 kilometers wide and about 100 kilometers thick—likely suspended solid material in liquid metal—could explain the shifts.
The findings suggest the outer core is not a uniform molten layer and may improve understanding of the deep dynamics tied to Earth's magnetic field.