SEISMIC EXPERIMENT IN PATAGONIA AND ANTARCTICA (SEPA)

--PROJECT DESCRIPTION--


PROJECT GOALS:

The present day tectonics and seismological structure of Patagonia, Drake Passage, and the Antarctic Peninsula region are among the most poorly understood of any location. The geodynamic setting of this region offers a unique opportunity to study complex tectonic interactions, as illustrated by the recent cessation of volcanism in the South Shetland Islands and onset of rifting in the Bransfield Strait. The SEPA project is a deployment of broadband seismographs in the Antarctic Peninsula and Patagonia regions, designed to answer the following questions:

  • Is current subduction occurring beneath the South Shetland Islands, as evidenced by a descending slab and intermediate depth earthquakes?

  • Is there evidence from seismic anisotropy for large scale mantle flow around the South American slab through the Drake Passage region?

  • What is the seismological structure and earthquake activity of the active back-arc spreading center in the Bransfield Strait? Are active volcanoes present?

  • What are the tectonics of Drake Passage, where plate motion models imply compression should be occurring?

  • Where are the active faults in Patagonia, and what level of seismic hazard exists there?


    STAGES OF THE SEPA PROJECT:

    January and February, 1997:

    Ten seismographs were deployed during January and February of 1997. Five stations were located in Chilean Patagonia and five in the Antarctic Peninsula region. Each station consists of a Streckheisen STS-2 broadband seismograph and a Reftek 24 bit seismograph with GPS timing. Data is recorded to 1.2 Gb - 4 Gb SCSI disks. Nine of the seismographs were provided by the PASSCAL program of IRIS (Incorporated Research Institutions in Seismology); a tenth seismograph is owned by Washington University.

    The field team consisted of:

  • Douglas Wiens - Washington University
  • Emilio Vera - Universidad de Chile
  • Sergio Barrientos - Universidad de Chile
  • Patrick Shore - Washington University
  • Gonzalo Perez - Universidad de Chile
  • Paul Friberg - PASSCAL (Lamont-Doherty Instrument Center)
  • George Helffrich - Bristol University (UK)
  • Erich Roth - Washington University

    The Antarctic instruments were deployed by flying to Frei Base on King George Island aboard a Chilean Air Force C-130. Other bases and remote sites were reached using the Chilean Navy ship "ISAZA", coordinated by the Instituto Antarctico Chileno (INACH).


    December 1997 - January 1998

    During the 1997-1998 Antarctic summer, a second trip was made to service the ten stations, retrieve data, and install one new seismometer on Low Island.

    The field team consisted of:

  • Patrick Shore - Washington University
  • Stacey Robertson - Washington University
  • Kenneth Lein - Universidad de Chile

    The R/V Abel-J, a small research ship, transported the team from Puerto Williams, Chile, to the Antarctic field sites. The team visited the previously installed Patagonian and Antarctic sites before installing the new station on Low Island (LOWI).


    December 1998 - January 1999:

    A third trip was made during the 1998-1999 Antarctic summer. Four of the Patagonia stations were removed, leaving only Puerto de Hambre (HAMB). The six Antarctic sites were serviced using the R/V Laurence M. Gould, and one new site was installed at Spring Point (SPPT). LeRoy Dorman of Scripps Institute of Oceanography also deployed fourteen ocean bottom seismometers (OBSs). The OBSs were removed in May of 1999.

    The field team consisted of:

  • Douglas Wiens - Washington University
  • Stacey Robertson - Washington University
  • Rodrigo Adaros - Universidad de Chile
  • Raul Rodriguez - Universidad de Chile


    December 1999 - January 2000:

    A fourth trip was made during the 1999-2000 Antarctic summer. Puerto de Hambre was serviced in Patagonia. Four of the Antarctic sites were removed, leaving three stations that continue to operate: O'Higgins (OHIG), Prat (PRAT) and Frei (FREI). The servicing trip was performed using the R/V Nathaniel B. Palmer.

    The field team consisted of:

  • Patrick Shore - Washington University
  • Rodrigo Adaros - Universidad de Chile


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    Comments or questions?? Send email to doug_at_kermadec.wustl.edu
    Latest revision: May 17, 2001