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

Abstract

AbstractA 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.