Earthquakes are complex in time and space
The existing models estimate earthquake magnitude by the earliest metrics of rupture signal-P waves from the near-field. However, there are three well-known issues in the current systems. First
, sensitive broadband sensors can be distorted and clipped in the near-field during strong shaking. Second
, the amplitude spectrum of large earthquakes saturates at higher frequencies, where accelerometers are most sensitive (this is called magnitude saturation). Finally
, the early signal of rupture may not provide the final information about the rupture (this is called non-determinism). As a result, determining large earthquake sources "quickly"
has been proven to be challenging. This is a trade-off between accuracy & warning time.