Though plate tectonics tells us that the Earth's surface is constantly in motion, Tierra del Fuego hasn't much moved since the Western settlement of this island appendage to southernmost South America, described by E. Lucas Bridges in his similarly-titled book[1], took place. Now physically about 3 metres closer to London on account of the motion of the plates, the distance is shrunk more by encroaching civilisation. What took an entire season of steamer travel to reach 150 years ago now takes an airliner about 30 hours. You can choose to fly to Punta Arenas, in Patagonia, or directly to Ushuaia, in Tierra del Fuego. Our scientific team studying earthquakes in Patagonia and Antarctica disembarked in Punta Arenas because it serves as a supply point for the Antarctic bases we also planned to use as seismic stations.

      The SEPA project (Seismic Experiment-Patagonia-Antarctica) is a two year deployment of seismographs in Chilean Patagonia, the South Shetland Islands, and the Antarctic Peninsula. It is a joint project, involving Bristol University, Washington University (St. Louis, Missouri, USA), and the Universidad de Chile, designed to answer some geological questions concerning this remote region of the Earth. The chief issues are:

1)

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

2)

Plate motion studies indicate that South America moves westward, narrowing the Pacific. Is there evidence for large scale mantle flow around South America through the Drake Passage region?

3)

What kind of earthquakes are happening in Drake Passage, and are they of the type expected from plate motion studies?

      Ten seismographs were deployed during January and February, 1997 to gather the data to address these issues. The group of 8 scientists was split into two teams to install the seismographs, five stations in Patagonia and five in Antarctica. The Antarctic instruments were deployed by five of us flying to a Chilean base aboard a Chilean Air Force C-130, and then dispersed to the other Antarctic bases and field sites on board the Chilean Navy ship "ISAZA". More prosaic deployment means were used in Patagonia by the other three team members: pickup trucks packed with gear. However, one of the stations we installed is at a unique point for motorists, the end of the southernmost road in continental South America at Puerto Hambre.

      About six months of data from each station has been recorded so far, and the data is being organized into earthquake-related slices in time by our Chilean and American colleagues. When the first batch arrives, intensive analysis will begin. We already know that Patagonia is seismically active because a locally large (magnitude 5) earthquake occurred earlier this year which was felt by many of the local residents. A preliminary location puts it within 5 kilometres of one of our stations.

Footnotes