(a) Map of seismic stations with annotated azimuths, (b) stacked spectral-amplitude ratios between the 2009 and 2013 UNE records for stations in the azimuths of 120°–145°, and (c) comparison of stacked spectral-amplitude ratios for various azimuthal ranges. The population of the spectral-amplitude ratios is assessed by using a Gaussian distribution function. (d) Quasi-observed waveforms at two regional stations (BAR, HIA) for an mb 5.1 UNE that are calculated based on the 2009 mb 4.7 UNE. The quasi-observed waveforms match the observed waveforms of the 2013 mb 5.1 UNE well. (e) Comparison between quasi-observed waveforms for mb 7.0 UNE based on the 2009 and 2013 UNE waveforms. The quasi-observed waveforms match well each other. The map was created by using the software Generic Mapping Tools (http://gmt.soest.hawaii.edu/).