On the Limitations of Spectral Source Parameter Estimation for Minor and Microearthquakes

Reliable estimation of earthquake source parameters is fundamental to improve our understanding of earthquake source physics and for ground-motion modeling in seismic hazard assessment. Nowadays, methods traditionally used for investigating the source parameters of earthquakes with Mw ≥ 3, such as spectral fitting or spectral ratio approaches, are also extensively applied to smaller magnitude events because of the increase in the number of stations and the more common borehole installations. However, when working with recordings of such minor and microearthquakes, significant limitations of the usable frequency range spanned by the spectra arise. At the lower end, signal-to-noise ratio constraints limit the usage of low frequencies, whereas at the upper end, the sampling rates of typical seismological networks as well as high-frequency attenuation can be limiting factors. In addition, earthquake source parameters determined from ground-motion spectra are known to exhibit potentially se...