In a study published on Wednesday in Science Advances, “Characterizing large earthquakes before rupture is complete” Diego Melgar and Gavin Hayes said the final magnitude of an earthquake could be determined in as little as 10 to 15 seconds after it begins. It this is true; it would give more precise warnings to populations that has not been hit.

For more info, please read the original article by The New York Times:
https://www.nytimes.com/2019/05/29/science/earthquakes-detection-richter-scale.html