Integration of P- and SH-wave high-resolution seismic reflection and micro-gravity techniques to improve interpretation of shallow subsurface structure: New Madrid seismic zone

C. E. Bexfield, J. H. McBride, A. J.M. Pugin, D. Ravat, S. Biswas, W. J. Nelson, T. H. Larson, S. L. Sargent, M. A. Fillerup, B. E. Tingey, L. Wald, M. L. Northcott, J. V. South, M. S. Okure, M. R. Chandler

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Shallow high-resolution seismic reflection surveys have traditionally been restricted to either compressional (P) or horizontally polarized shear (SH) waves in order to produce 2-D images of subsurface structure. The northernmost Mississippi embayment and coincident New Madrid seismic zone (NMSZ) provide an ideal laboratory to study the experimental use of integrating P- and SH-wave seismic profiles, integrated, where practicable, with micro-gravity data. In this area, the relation between "deeper" deformation of Paleozoic bedrock associated with the formation of the Reelfoot rift and NMSZ seismicity and "shallower" deformation of overlying sediments has remained elusive, but could be revealed using integrated P- and SH-wave reflection. Surface expressions of deformation are almost non-existent in this region, which makes seismic reflection surveying the only means of detecting structures that are possibly pertinent to seismic hazard assessment. Since P- and SH-waves respond differently to the rock and fluid properties and travel at dissimilar speeds, the resulting seismic profiles provide complementary views of the subsurface based on different levels of resolution and imaging capability. P-wave profiles acquired in southwestern Illinois and western Kentucky (USA) detect faulting of deep, Paleozoic bedrock and Cretaceous reflectors while coincident SH-wave surveys show that this deformation propagates higher into overlying Tertiary and Quaternary strata. Forward modeling of micro-gravity data acquired along one of the seismic profiles further supports an interpretation of faulting of bedrock and Cretaceous strata. The integration of the two seismic and the micro-gravity methods therefore increases the scope for investigating the relation between the older and younger deformation in an area of critical seismic hazard.

Original languageEnglish
Pages (from-to)5-21
Number of pages17
Issue number1-2
StatePublished - Jun 26 2006

Bibliographical note

Funding Information:
This research was supported, in part, by the U. S. Geological Survey (USGS), Department of the Interior, under USGS award numbers 1434-95-G-2525 and 1434-HQ-97-GR-03195 as part of the National Earthquake Hazards Reduction Program. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U. S. Government. Additional financial support was provided by a Brigham Young University Mentoring Environment Grant. We also acknowledge the support of this research by Landmark Graphics Inc. via the Landmark University Grant Program and by a software grant from Seismic Micro-Technology. Reviews by C. Juhlin and an anonymous referee greatly improved the final version of the paper.


  • Faulting
  • New Madrid
  • Seismic hazard
  • Seismic reflection
  • Shear waves

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes


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