The deep structure of East Antarctica from broadband seismic data: SSCUA 2002/03

Anya M. Reading

East Antarctica is the least-known region of the tectonic Earth yet it is a key component in our understanding of the formation and break-up of Gondwana and present-day crust and mantle dynamics. One of the few ways to advance our understanding of this remote continent is through the analysis of high-fidelity broadband seismic records. Stations may be deployed on rock or ice and allow the regional tectonic structure to be determined even where there is no surface exposure. Successive deployments of remote, solar-powered stations allow a large region of the continent to be sampled by energy from distant earthquakes. Seismic methods concerning body waves allow crustal and upper mantle structure to be determined and surface waves improve the resolution of the mantle across this vast region with very few permanent stations.

Recent geological and geochronological work in Antarctica and the southern hemisphere continents has changed our concept of the traditional tectonic framework of the Gondwana supercontinent. The idea of East Antarctica as an ancient, Archaean keystone around which the other continental blocks assembled has been changed by the identification of extensive mobile tectonic belts which trend perpendicular to the current Antarctic coastline. The extent of these major tectonic structures beneath the ice may be mapped using broadband seismic data. The present day seismicity and the mantle structure and dynamics of East Antarctica will also be investigated to address fundamental questions concerning Antarctic neotectonics.

The main deployment of SSCUA (Seismic Structure of the Continent Under Antarctica) seismic stations took place in the austral summer of 2002/03, following a pilot study the pilot study of 2001/02, during which a mains-powered station at Davis and a remote station at Beaver Lake were installed. Using field logistics and operational and stations support provided by Australian Antarctic Division, stations were installed at 5 further remote locations around the Lambert Glacier region (Figure 1). Locations furthest from Davis were installed using fixed-wing aircraft, and those further north using small helicopters. The station at Komsomolskiy Peak was located on the furthest south outcrop of rock in Australian Antarctic Territory – a challenging location for both instrumentation and the installation team. Each remote station consists of a Guralp CMG-ESP sensor (Figure 2, KOMS), frame-mounted solar panels and GPS antenna and an insulated box (Figure 3, KOMS) containing a Nanometrics Orion recorder, batteries, voltage regulator and sensor control box.

During 2002/03, data was uplifted from Beaver Lake and Davis stations, installed during the pilot deployment of the previous summer. Figure 4 shows data of excellent quality recorded at Beaver Lake during December 2002 from a teleseismic event close to Papua New Guinea against the low-noise background characteristic of the Antarctic interior during good weather. The majority of the data will be uplifted during the following Antarctic summer, 2003/04, after which the main data analysis will commence. On-line information: SSCUA deployment web-site, http://rses.anu.edu.au/seismology/sscua

AnSWeR, Antarctic Seismic Web Resource, http://rses.anu.edu.au/seismology/answer

Figure 4 Example of data from Beaver Lake, Antarctica. The earthquake occurred near Papua New Guinea on 12th December 2002.

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Questions about this topic to Anya reading:
anya.reading@anu.edu.au

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