Deep reflection experiments in northeastern Australia, 1976–1978

Geophysics ◽  
1983 ◽  
Vol 48 (12) ◽  
pp. 1588-1597 ◽  
Author(s):  
S. P. Mathur
Keyword(s):  
Sedimentary Basin ◽  
Mineral Resources ◽  
Crust And Upper Mantle ◽  
Recording Time ◽  
Northern Margin ◽  
Free Zone ◽  
Extra Effort ◽  
Reflection Data ◽  
Common Depth Point ◽  
Crustal Reflection

Between 1976 and 1978 the Australian Bureau of Mineral Resources (BMR) recorded deep crustal reflection data at seven sites in northeastern Australia over continuous profiles up to 15 km long by simply extending the recording time to 16 sec during normal sedimentary basin surveys. The record sections show many events with variable strength, continuity, dip, and spatial distribution. By comparing the sections from the longer and the shorter perpendicular traverses, it is possible to discriminate between primary reflections and diffractions, multiples, and other noise events. Based on their character the reflections can be grouped into zones which are interpreted in terms of the nature and structure of the crust. Most of the reflection sections show, below the sedimentary reflections, a thin (2–3 sec) reflection‐free zone underlain by a thick (9 sec or more) zone of numerous reflection segments which varies in thickness and the distribution of reflection segments. The data thus suggest that the upper crust under the sediments is similar in seismic character throughout northeastern Australia. On the other hand, the deeper crust under the Georgina and Drummond basins is significantly different in seismic signature and thickness from that under the Bowen basin and the northern margin of the Galilee basin. It is concluded that good quality deep reflections can be recorded with little extra effort during sedimentary basin surveys using modern multiple‐fold common‐depth‐point (CDP) techniques, and that the data recorded on long traverses, cross‐spreads, and expanded spreads provide information on the structure and composition of the crust and upper mantle with a resolution greater than has been possible before. Such information is valuable in studying the evolution of mineral and petroleum provinces and the lithosphere in general.

Crustal structure and surface zonation of the Canadian Appalachians: implications of deep seismic reflection data

1989 ◽  
Vol 26 (2) ◽  
pp. 305-321 ◽  
Author(s):  
François Marillier ◽  
Charlotte E. Keen ◽  
Glen S. Stockmal ◽  
Garry Quinlan ◽  
Harold Williams ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Surface Expression ◽  
Seismic Profiles ◽  
Crust And Upper Mantle ◽  
Seismic Reflection Data ◽  
Central Block ◽  
Reflection Data ◽  
Lower Crustal ◽  
Canadian Appalachians

In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.

A comparison of legacy and recently acquired multichannel seismic data on 95 Ma Pacific oceanic crust south of the Hawaiian Islands

2020 ◽  
Author(s):  
Phil Cilli ◽  
Tony Watts ◽  
Brian Boston ◽  
Donna Shillington
Keyword(s):  
Oceanic Crust ◽  
Hawaiian Islands ◽  
Separation Distance ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Common Depth Point ◽  
The Pacific ◽  
Original Field ◽  
Multichannel Seismic Reflection Data ◽  
Multichannel Seismic Data

<p>The oceanic crust in the vicinity of the Hawaiian Islands is of tectonic interest because it formed at a fast spreading mid-oceanic ridge during the Late Cretaceous (Turonian) and has been deformed since the Late Miocene by volcanic loads generated at a deep mantle hotspot. We have used legacy and recently acquired multichannel seismic reflection data to determine the character of oceanic crust and the Moho in a region south of the Hawaiian Islands where the Pacific plate has been flexed upwards partly by volcano loading and partly by the dynamics of the hotspot. The legacy data is based on Common Depth Point (CDP) and Constant Offset Profile (COP) data acquired onboard R/V <em>Robert D. Conrad</em> and R/V <em>Kana Keoki</em> during August/September 1982. <em>Conrad</em> was equipped with a 3.6 km long streamer and a 1864 cu. in. airgun array and <em>Kana Keoki</em> was equipped with a 1864 cu. in. array. During the COP experiment the two ships steamed on a similar heading and a separation distance of 3.6 km, yielding an effective offset for reflection data of 7.2 km. Original field data have been re-processed with ‘state-of-the-art’ seismic processing work flows using Shearwater REVEAL software. The recently acquired data was acquired during October 2018 with R/V <em>Marcus G. Langseth</em>, equipped with a 15 km long streamer and a 6600 cu. in. airgun array. Comparisons between the legacy and recently acquired reflection data have been informative, revealing new methods to process <em>Conrad’s</em> legacy of multichannel data acquired on 31 cruises during 1975 to 1989 and new insights on the structure and nature of the Moho in 95 Ma oceanic crust.</p>

Enhancing crustal reflection data through curvelet denoising

2011 ◽  
Vol 508 (1-4) ◽  
pp. 106-116 ◽  
Author(s):  
Vishal Kumar ◽  
Jounada Oueity ◽  
Ron M. Clowes ◽  
Felix Herrmann
Keyword(s):  
Reflection Data ◽  
Crustal Reflection
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