ABSTRACT: Improving satellite-derived gravity data in nearshore waters by radar-signal re-tracking: an eastern Indonesian perspective

Laxon, Seymour¹, John Milsom¹, Dave McAdoo², and Tim Wright³
(1) University College London, London, United Kingdom
(2) NOAA, Silver Spring, MD
(3) Oxford University, Oxford, United Kingdom

Inversion of satellite radar altimetry is now an established method for estimating marine free-air gravity values. Data quality in the deep oceans is generally superior to that achievable by all but very detailed shipborne surveys, but problems persist in the shallower waters which are commonly of interest to the oil industry. Errors caused by tides and currents can be treated using oceanographic data, but errors due to contamination of the signal by echoes from reefs and small islands within the radar footprint require a different approach. Conventional processing discards these data, but it has proved possible to separate sea-surface returns from other echoes in ERS-1 full-waveform data, first in ice covered areas and more recently in the island-strewn waters of eastern Indonesia. Comparisons with shipborne data have shown that improvements over more conventionally processed data are small in open water but significant near coastlines. Further enhancement is possible if onshore gravity data are used to control the inversion.

The roughly triangular Teluk Cendrawasih (Irian Jaya) provides an excellent example of the new approach. A deep gravity low in the east, partly defined by land measurements, occupies almost half the offshore area, but higher gravity dominates further west. In the north, the Yapen Fault is emphasised in the new data. The differences from other published inversions are in places very large. Reprocessed satellite gravity is thus making a significant contribution to interpretation of this poorly known region.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia