A new dawn for Australian ocean-bottom seismography

Abstract

The Australian government recently acquired 20 state-of-the-art broadband ocean-bottom seismograph (OBS) units. These instruments were designed and built by Güralp Systems Ltd. (U. K.) with the ability to withstand extreme ocean depths to 6000 m and to remotely record data for as long as 12 months. The Australian national OBS fleet is part of AuScope's Australian Geophysical Observing System (AGOS) — an initiative of the Australian government funded through the Education Investment Fund (EIF). These instruments will contribute greatly to understanding of the crust beneath oceanic basins surrounding Australia. In 2014–2015, the Australian national OBS fleet was used by the petroleum industry on several seismic surveys. High-quality data were recorded at all OBS deployment sites, often to offsets sufficiently large enough to detect possible Pn phases — refractions from the upper mantle. Such information means that crustal thickness as well as the seismic-velocity distribution to the Moho can be determined. As a result, these data can provide important constraint for subsidence and hydrocarbon-maturation modeling. Analysis of earthquake data recorded during marine seismic surveys is ongoing and should provide new information on the interaction between anthropogenic signals (air-gun sources, vessel noise) and the natural environment. Recording earthquake and air-gun signals at fixed locations opens a completely new possibility for calibration and comparison of those signal strengths and spectral compositions. Access to the OBS fleet is open to industry, academia, and government organizations. Application to use Australia's OBS fleet is via a simple process through ANSIR ( www.ansir.org.au ).