A New Strategy for Weak Events in Sparse Networks: The First-Motion Polarity Solutions Constrained by Single-Station Waveform Inversion
Abstract
Moment tensor determinations of small earthquakes are quite challenging. It is because their signal-to-noise ratio is satisfactory only at frequencies above the microseismic noise peak (TILDE OPERATOR+D910.2 Hz), and waveforms can be modeled only up to TILDE OPERATOR+D911-2 Hz at relatively near stations (epicentral distance of a few kilometers).
Therefore, the availability of high-quality waveforms at near stations is the most critical issue. Dense local networks enable solving specific issues like non-double-couple (non-DC) components (e.g., Vavryčuk, 2011), relation with tectonics (Serpetsidaki et al., 2013), and/or even space-time clustering of moment tensors (Cesca et al., 2014).
On the contrary, records of weak events at very few local stations hardly allow us to get even DC components of moment tensors.