Structural Interpretation of Multichannel Seismic Reflection Profiles Crossing the Southeastern United States and the Adjacent Continental Margin: Decollements, Faults, Triassic(?) Basins and Moho Reflections

  1. Muawia Barazangi and
  2. Larry Brown
  1. John C. Behrendt

Published Online: 15 MAR 2013

DOI: 10.1029/GD014p0201

Reflection Seismology: The Continental Crust

Reflection Seismology: The Continental Crust

How to Cite

Behrendt, J. C. (1986) Structural Interpretation of Multichannel Seismic Reflection Profiles Crossing the Southeastern United States and the Adjacent Continental Margin: Decollements, Faults, Triassic(?) Basins and Moho Reflections, in Reflection Seismology: The Continental Crust (eds M. Barazangi and L. Brown), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD014p0201

Author Information

  1. U.S. Geological Survey, Denver, Colorado 80225

Publication History

  1. Published Online: 15 MAR 2013
  2. Published Print: 1 JAN 1986

Book Series:

  1. Geodynamics Series

ISBN Information

Print ISBN: 9780875905143

Online ISBN: 9781118670118

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Keywords:

  • Earth—Crust—Congresses;
  • Continents—Congresses;
  • Seismic reflection method—Congresses

Summary

In 1981 the U.S. Geological Survey (USGS) acquired 1350 km of 96-channel, 24-fold, multichannel seismic-reflection data along three profiles (S4, S6, and S8), recorded to 6 s and 8 s, extending across South Carolina and Georgia from the Appalachians to the Atlantic coast. Previously, in 1979, a 6-line grid (CH 1– CH 6) comprising 650 km of 64-channel, 32-fold data recorded to 12 s was surveyed over the continental shelf near Charleston, S. C. That offshore grid is tied to line S4 onshore and to the regional survey of the Atlantic continental margin. The result is a transect of four lines (including published COCORP data for Tennessee-Georgia) across the southeastern United States, extending, on a number of offshore deep-reflection lines, to oceanic crust.

The Appalachian decollement can be seen discontinuously on S6 and S8 from the Appalachian Mountains southeastward as far as the Carolina Slate Belt; it is not apparently continuous to the surface interpreted as the Charleston decollement offshore. A series of reflections on lines S4, S6, and S8 and on the COCORP line is interpreted as evidence of southeastward-dipping imbricate faults, from the Brevard fault on the northwest to beyond the Augusta fault, which marks the southeastern extent of the Eastern Piedmont fault zone. The Carolina Slate Belt is characterized on the four seismic profiles by a complex series of diffractions and reflections extending from less than l s to 8 s. A number of Triassic(?) basins are apparent in the reflection data for the rifted Charleston terrane identified from low-gradient magnetic anomalies. These basins are bounded by normal faults reactivated in the meizoseismal area of the Charleston earthquake of 1886 and elsewhere, in a compressional reverse or strike-slip sense during Late Cretaceous and Cenozoic time. It appears probable that the seismicity in the Charleston terrane is related to movement on these fault zones bounding the basins; movement on the faults identified at depth in the eastern Piedmont fault zone may be related to seismicity there. Good reflections from the Moho are observed in the 6 CH lines offshore of Charleston in the range of 8–11 s, which is consistent with COCORP reflection data for land surveys.