A New Posthole Seismometer at Concordia Permanent Research Facility in the Heart of the Icy East Antarctic Plateau

In the Southern Hemisphere, the prevalence of oceans and the difficulty of access to land result in reduced coverage of seismological stations, limiting our detailed knowledge of Earth’s structures and of large earthquakes sources. This situation is exacerbated inside the antarctic continent, where only two permanent seismic stations are currently available (IU.QSPA at South Pole and G.CCD). The CCD station, built in early 2000s with state-of-the-art surface instrumentation and located at the French–Italian Concordia base (75° S, 123° E), has been providing seismological data since 2008. However, it suffers from several problems: the vault is deformed by the hydrostatic pressure of the snow, the firn waveguide traps anthropogenic noise from the base causing strong noise below 1 s, and a coupling defect limits the performance above 30 s on the horizontal channels. To ensure the continuity of CCD and to improve its overall performance, we started in 2014 to plan the installation of a borehole seismometer at the site. In this article, we describe in detail this renovation of CCD and some examples of data analysis. The new borehole sensor shows that short-period disturbances are largely attenuated (−20 dB at 0.1 s) compared to the surface installation and that the horizontal channels have a lower noise level at long periods (−8 dB at 100 s). Data for all components are below the standard noise model between 0.1 and 0.2 s, which makes this sensor one of the quietest installations in the world for this bandwidth. For periods >600 s we observe atmospheric pressure-related perturbations on the vertical component. Despite this problem, the new CCD borehole station is a success with better-than-expected performances at all periods <600 s. The data produced are now distributed in the world’s data centers as G.CCD.20 and we encourage the scientific community to use the data for all studies requiring seismograms from Antarctica.

[1]  P. Koelemeijer,et al.  Normal mode observability of radial anisotropy in the Earth’s mantle , 2022, Geophysical Journal International.

[2]  P. Richards,et al.  Achievements and Prospects of Global Broadband Seismographic Networks After 30 Years of Continuous Geophysical Observations , 2022, Reviews of Geophysics.

[3]  A. Ringler,et al.  Modeling tilt noise caused by atmospheric processes at long periods for several horizontal seismometers at BFO - a reprise , 2021, Geophysical Journal International.

[4]  M. DuVernois,et al.  Six Decades of Seismology at South Pole, Antarctica: Current Limitations and Future Opportunities to Facilitate New Geophysical Observations , 2021 .

[5]  A. Deuss,et al.  A new catalogue of toroidal-mode overtone splitting function measurements , 2021, Geophysical Journal International.

[6]  D. Wiens,et al.  Seismic Structure of the Antarctic Upper Mantle Imaged with Adjoint Tomography , 2020, Journal of Geophysical Research: Solid Earth.

[7]  N. Leroy,et al.  Quality Improvement of the French Permanent Broadband Stations with Shallow Posthole Installations , 2019 .

[8]  A. Cannata,et al.  Exploring the link between microseism and sea ice in Antarctica by using machine learning , 2019, Scientific Reports.

[9]  B. Romanowicz,et al.  Anisotropy in the deep Earth , 2017 .

[10]  C. R. Hutt,et al.  Broadband seismic noise attenuation versus depth at the Albuquerque Seismological Laboratory , 2017 .

[11]  L. Rivera,et al.  Long-period analysis of the 2016 Kaikoura earthquake , 2017 .

[12]  H. Benz.  Building a National Seismic Monitoring Center: NEIC from 2000 to the Present , 2017 .

[13]  L. Arnaud,et al.  Modelling firn thickness evolution during the last deglaciation: constraints on sensitivity to temperature and impurities , 2016 .

[14]  Yuansheng Li,et al.  S‐velocity model and inferred Moho topography beneath the Antarctic Plate from Rayleigh waves , 2015 .

[15]  G. Ekström,et al.  An anisotropic shear velocity model of the Earth's mantle using normal modes, body waves, surface waves and long-period waveforms , 2014 .

[16]  A. Deuss.  Heterogeneity and Anisotropy of Earth's Inner Core , 2014 .

[17]  Göran Ekström,et al.  The global CMT project 2004–2010: Centroid-moment tensors for 13,017 earthquakes , 2012 .

[18]  É. Stutzmann,et al.  Observations of the seasonality of the Antarctic microseismic signal, and its association to sea ice variability , 2011 .

[19]  J. Lévêque,et al.  Seismological constraints on ice properties at Dome C, Antarctica, from horizontal to vertical spectral ratios , 2010, Antarctic Science.

[20]  Lion Krischer,et al.  ObsPy: A Python Toolbox for Seismology , 2010 .

[21]  É. Stutzmann,et al.  Global climate imprint on seismic noise , 2009 .

[22]  Agathe Roullé,et al.  Site Effects in the City of Lourdes, France, from H/V Measurements: Implications for Seismic-Risk Evaluation , 2007 .

[23]  E. Wielandt,et al.  On the minimum of vertical seismic noise near 3 mHz , 2007 .

[24]  Kazushige Obara,et al.  A densely distributed high-sensitivity seismograph network in Japan: HI-net by National Research Institute for Earth Science and Disaster Prevention , 2005 .

[25]  Daniel E. McNamara,et al.  Ambient Noise Levels in the Continental United States , 2004 .

[26]  Carlo Barbante,et al.  Eight glacial cycles from an Antarctic ice core , 2004, Nature.

[27]  D. Rouland,et al.  Overlooked earthquakes on and around the Antarctica plate: identification and location of 1999 shallow depth events , 2003 .

[28]  D. Albert.  Theoretical modeling of seismic noise propagation in firn at the South Pole, Antarctica , 1998 .

[29]  P. Lognonné,et al.  The effects of the atmospheric pressure changes on seismic signals or how to improve the quality of a station , 1996, Bulletin of the Seismological Society of America.

[30]  Yefim Gitterman,et al.  Empirical site response evaluations: case studies in Israel , 1996 .

[31]  Hsi-Ping Liu,et al.  Site amplification at five locations in San Francisco, California: A comparison of S waves, codas, and microtremors , 1996, Bulletin of the Seismological Society of America.

[32]  W. Zürn,et al.  On noise reduction in vertical seismic records below 2 mHz using local barometric pressure , 1995 .

[33]  J. Tromp,et al.  Toroidal splitting observations from the Great 1994 Bolivia and Kuril Islands Earthquakes , 1995 .

[34]  J. Hinderer,et al.  Effective barometric admittance and gravity residuals , 1995 .

[35]  Edward H. Field,et al.  A comparison and test of various site-response estimation techniques, including three that are not reference-site dependent , 1995 .

[36]  Francisco J. Chávez-García,et al.  Site effect evaluation using spectral ratios with only one station , 1993, Bulletin of the Seismological Society of America.

[37]  E. Wielandt,et al.  The leaf-spring seismometer: Design and performance , 1982 .

[38]  F. Press,et al.  Further study of atmospheric pressure fluctuations recorded on seismographs , 1953 .

[39]  R. Widmer-Schnidrig,et al.  Improvements in seismic resolution and current limitations in the Global Seismographic Network , 2019, Geophysical Journal International.

[40]  A. Souriau,et al.  Deep Earth Structure – The Earth’s Cores , 2015 .

[41]  O. Eisen,et al.  Joint interpretation of explosive and vibroseismic surveys on cold firn for the investigation of ice properties , 2013, Annals of Glaciology.

[42]  M. Vallée,et al.  SCARDEC: a new technique for the rapid determination of seismic moment magnitude, focal mechanism and source time functions for large earthquakes using body‐wave deconvolution , 2011 .

[43]  A. Reading.  The seismicity of the Antarctic plate , 2007 .

[44]  Y Nakamura,et al.  A METHOD FOR DYNAMIC CHARACTERISTICS ESTIMATION OF SUBSURFACE USING MICROTREMOR ON THE GROUND SURFACE , 1989 .