Estimation of Seismic Attenuation of the Greenland Ice Sheet Using 3-D Waveform Modeling

We estimated the seismic attenuation (Q factor) of the Greenland Ice Sheet (GrIS) by comparing observed and theoretical Rayleigh waveforms. Observed waveforms are obtained by interfering noise waveforms in vertical-component seismograms between stations belonging to the latest broadband seismic network distributed throughout Greenland (GLISN network). Theoretical waveforms are calculated by parallel computation using the latest 3-D seismic waveform modeling method. Comparing the observed waveforms with the theoretical waveforms at different Q factors reveals that the GrIS has a low Q of 10 <= Q(P), Q(S) <= 50, indicating very high attenuation of seismic waves due to the ice. This study is the first to establish the low Q factor of ice sheets via ultra-long-distance propagation (350-1,000 km). The Q factors obtained in this study are indispensable for estimating the thermal state and density distribution of the GrIS, as well as for interpreting the characteristics of seismic waveform that propagates through the GrIS. Plain Language Summary Seismic anelastic attenuation refers to the energy loss caused by anelastic processes or internal friction during wave propagation and is quantified by the quality (Q) factor. The Q factor of ice sheets and glacial ice is especially important because it is highly sensitive to the thermal state and density distribution. We estimated the Q factor of the Greenland Ice Sheet (GrIS) by comparing observed and theoretical surface (Rayleigh) waveforms. Observed waveforms are extracted by the latest broadband seismic network distributed throughout Greenland (GLISN network). Theoretical waveforms are calculated using the latest 3-D seismic waveform modeling method. The results showed an extremely low Q (10-50) for the GrIS, indicating very high attenuation of seismic waves. Although previous studies have obtained similar results, they all used high frequency (>= 30 Hz) seismic waves with short propagation distances (<similar to 10 km). This study is the first to infer the large-scale, bulk Q property of the GrIS using low-frequency (0.1-0.3 Hz) waves and long (350-1,000 km) propagation distances. The Q factors obtained in this study are essential for estimating the internal state of the GrIS, as well as for interpreting the characteristics of seismic waveforms that propagate through it.