\documentclass[review,jog]{igs}
% \documentclass[review,aog]{igs}

\usepackage[utf8]{inputenc}

\usepackage{mathabx}
\usepackage{graphicx}
\usepackage{siunitx}

% the default is for unnumbered section heads
% if you really must have numbered sections, remove
% the % from the beginning of the following command
% and insert the level of sections you wish to be
% numbered (up to 4):

% \setcounter{secnumdepth}{2}

\jourvolume{12}
\jourissue{3}
\jourpubyear{2021}

\begin{document}

\title[Surface waves in Antarctic firn]{Ambient High Frequency Seismic Wavefields in Antarctic Firn}

\author[Chaput and others]{Julien CHAPUT,$^1$
  Rick ASTER,$^2$ Marianne KARPLUS,$^1$ Nori NAKATA,$^3$ \protect\thanks{Present address:
  Department of Earth, Environmental, and Resource Sciences, University of Texas at El Paso, EL Paso, TX,
  USA.}}

\affiliation{%
$^1$Department of Earth, Environmental, and Resource Sciences, University of Texas at El Paso, El Paso, TX, USA\\
$^2$Department of Geosciences and Warner College of Natural Resources, Colorado State University, Fort Collins, CO, USA\\
$^3$Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Boston, MA, USA\\
  Correspondence: Julien Chaput 
  \email{jachaput@utep.edu}}

\section{Supplement}

\subsection{Detailed observations from the RIS network}
The dense portion of the seismic array provides us with a measure of spatial variance on our measurements. We now seek to examine the two primary frequency bands of interest (5--12 Hz and 20--50 Hz) to single isolated stations of the RS array. Fig.S1 and Fig.S2 provide individual results from these isolated stations (i.e., those not part of the central array shown in Figure 8) for fast directions and slow directions, given that the two axes are not necessarily recovered to an equal degree of robustness. We find that low frequency (5--12 Hz) fast directions are often correlated with observable surface features, such as rifts, transported or local crevasses, and other flow and strain related structures.  Fast directions at higher frequencies converge to being parallel to flow, as is the case for the DR array. The apparent higher volatility in the lower frequency directions can be simply explained by the tendency for deeper structures to be carried over from past strain regimes and transformed in complex unpredictable (and often invisible) fashions. Examples where deeper anisotropy appears complex can be seen near or on the ridge above the DR array (e.g., DR05, DR15, Figure 8). Crevasses nearest to those stations feature accurate structures, with the closest edge being perpendicular to the low frequency slow direction. The higher frequency range (blue) is more clearly consistent in terms of fast directions being aligned with flow direction.  Flow appears to dominate the higher frequency splitting regime save for a few cases where the flow direction itself is unclear or complex (e.g., RS13, RS09, and RS12).

In some cases, clear crevasse structures are lacking in imagery, and the low frequency splitting matches the high frequency splitting (e.g. DR15, RS06, RS17, DR05), which is plausible since plastic deformation of denser firn and ice is also possible in the absence of pre-existing weaknesses, as per our calculations in the main text (i.e., the entire RIS is well below the d/b transition for ice in terms of strain). Given that these resonances have also been observed at other Antarctic locations (South Pole, West Antarctic Ice Sheet, Nascent Iceberg, and WAIS Divide; \citealt{Chaput2018,Chaput2022}), this form of single station observation can serve as a useful sparse observation to better understand the strain regime affecting deeper ice structures.


\clearpage
\newpage
\pagebreak

\begin{figure}
\centering
\includegraphics[width=1\textwidth]{Supp_Fig_1.pdf}
\caption{Fast directions computed at isolated stations on the Ross Ice Shelf, binned in terms of radial histograms as follows: Red = 5--17 Hz; Yellow = 17--30 Hz; Blue= 30--50 Hz. Green arrows depict estimated flow directions. Several stations in the Marie Byrd Land (RS12-RS14) do not show obvious flow directions so flow arrows are omitted.}
\label{figS1}
\end{figure}

\clearpage
\newpage
\pagebreak

\begin{figure}
\centering
\includegraphics[width=1\textwidth]{Supp_Fig_2.pdf}
\caption{Same as Fig.S1, but for slow directions. }
\label{figS2}
\end{figure}


\newpage
\clearpage

\bibliography{Chaput_RIS_2017.bib}
\bibliographystyle{igs} 

\end{document}