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Los Angeles was likely too far away from Monday’s epicenter for anyone to feel the quake’s “P” wave — the first type of shaking wave an earthquake generates, in which the rock vibrates in the direction of the moving wave.

Depending on where people are, some may not get a warning before they feel the first shaking, which is known as the “P wave.”

This superrotation was gradually realigning the seismic wave paths with a north-south axis in the inner core known to boost P wave speeds.

The system’s sensors can rapidly detect that initial P wave and send that data to a processing center, where algorithms can determine and estimate the geographical extent of the earthquake, the magnitude and the expected shaking intensity in different areas, Crayne said.

“The P wave is first and fast. It travels out and ahead of the S wave, and it is not producing the shaking,” Crayne said.