![Decoding Mysterious Seismic Signals](https://cdn.newsserve.net/en/knowledge/North-America_20190129.jpg)
Decoding Mysterious Seismic Signals
For the decades since their discovery, seismic signals known as PKP precursors have challenged scientists. Regions of Earth’s lower mantle scatter incoming seismic waves, which return to the surface as PKP waves at differing speeds.
The origin the precursor signals, which arrive ahead of the main seismic waves that travel...