We present an improved method for quickly and accurately estimating the size (magnitude) of earthquakes, which is especially important for issuing early warnings for tsunamis near the coast. Traditional methods using seismic data can be too slow, and geodetic methods often rely on less precise assumptions. We enhance a combined “seismogeodetic” approach using high-rate GPS and accelerometer data originally developed for one type of earthquake (thrust) to now also compatible with strike-slip and normal faults.

We test our method on 16 past earthquakes of different types and find it could reliably estimate magnitudes within 2–3 minutes of the event starting, with an accuracy of ±0.2 units. Key improvements included accounting for how earthquake waves travel and expanding data use to stations with limited instruments. While correcting for wave direction offered little benefit due to real-time challenges, using known tectonic data helped guide model choice.

Overall, the expanded approach enables faster and more reliable magnitude estimates, which is vital for tsunami and earthquake warning systems, especially in regions close to the earthquake’s source.