Abstract
Low-frequency earthquakes (LFEs) are detected within tremor, as small,
repetitive, impulsive low-frequency (1-8 Hz) signals. While the
mechanism causing this depletion of the high frequency content of their
signal is still debated, this feature may indicate that the source
processes at the origin of LFEs are different from those for regular
earthquakes. Key constraints on the LFE-generating physical mechanisms
can be obtained by establishing scaling laws between their seismic
moment and source durations. Here we apply a simple spectral analysis
method to the S-waveforms of LFEs from Guerrero, Mexico to measure their
seismic moments and corner frequencies, a proxy to source duration. We
find characteristic values of seismic moment around 3e12 N.m (Mw 2.3)
and of corner frequencies around 3 Hz with the corner frequency very
weakly dependent on the seismic moment. This moment-duration scaling
observed for Mexican LFE is similar to one previously reported in
Cascadia and is very different from the established one for regular
earthquakes. This suggests that they could be generated by sources of
nearly constant size with strongly varying intensities. LFEs do not
exhibit the self-similarity characteristic of regular earthquakes,
suggesting that the physical mechanisms at their origin could be
intrinsically different.