Seismic Waveform‐Coherence Controlled by Earthquake Source Dimensions

Rupture size is a fundamental earthquake source parameter that challenging to infer independently from far-field seismological observations. Here, we develop novel observational constraint on based the decay rate of wavefield coherence across seismic array. For given earthquake, waveform decays with increasing interstation distance or, more precisely, projection difference defined as between takeoff vectors associated two stations projected along rupture direction. We find generally falls off faster for earthquakes larger magnitudes. The magnitude dependence can be explained by finite effect: sizes cause differences phase delays waves arriving different parts at stations, hence stronger spatial variability wavefield, resulting in breakdown coherence. Assuming 1-D Haskell's model, estimated rate. apply this method USArray data three subduction zones, Sea Okhotsk, South America and Japan. inferred patterns are consistent scaling relations intermediate width-saturated L-models quasi equi-dimensional models. Our observation captures unique pattern array demonstrates potential utilizing study parameters.