Earth’s inner core shows seismic anisotropy, with waves 3–4% faster along the rotation axis than at the equator, increasing with depth. Boy, 9, feels unwell after hike—parents face devastating reason ...

Earth’s inner core has long puzzled scientists because seismic waves move through it unevenly. Compressional waves from earthquakes travel about 3 to 4 percent faster along the planet’s rotation axis ...