Earthquake notifications are typically add-on apps and regional in nature, or potentially via government notifications, and again these can be regional.
These are not forecasting apps, but are based on a network of sensors detecting an earthquake at some distance, and exploiting the difference in propagation times of the shaking and of the networks and notifications.
Either, neither, or both of these paths can potentially be available, depending on your particular location.
If you are located in the US states California, Oregon, and Washington, see the MyShake app. This app is part of the USGS MyShake project.
¿Para México, tal vez el app de SASSLA? Hay otros.
It would be be interesting to see if Apple could automate detection more widely using iPhone and iPad and presumably a whole lot of machine learning, but that is not available. If it is even possible. And mis-detections are bad.
In any case, send your suggestion to Apple: Product Feedback - Apple
Also send feedback to your elected representatives, as they control funding for these sorts of projects.