A Dynamic Rupture Source Model for Very Low-Frequency Earthquake Signal Without Detectable Nonvolcanic Tremors

A very low-frequency earthquake is a type of seismic event that is rich in low frequencies and depleted in higher frequencies compared to regular fast local earthquakes of similar magnitude. The source process behind very low-frequency earthquakes is still poorly understood. Here we present a dynamic rupture source model for very low-frequency earthquake signal without detectable associated tremors. We show that a single asperity model with sudden stress drop followed by a rate strengthening effect damps the seismic radiation and increases event duration. We compute synthetic seismograms for our source model. The synthetic signal successfully reproduces the features of observed very low-frequency earthquakes. Moreover, the synthetic very low-frequency earthquake signal in 0.02–0.05 Hz is not accompanied by detectable tremor signals at 2–8 Hz. Our results help explain why in some cases we observe very low-frequency earthquakes without accompanying tremor.