Advertisement

pure and applied geophysics

, Volume 135, Issue 1, pp 31–52 | Cite as

Seismic tomography constrained by bouguer gravity anomalies: Applications in western Washington

  • J. M. Lees
  • J. C. VanDecar
Article

Abstract

Tomographic inversions for velocity variations in western Washington indicate a high correlation with surface geology and geophysical measurements, including gravity observations. By assuming a simple linear relationship between density and velocity (Birch's law) it is possible to calculate the gravity field predicted from the velocity perturbations obtained by local tomographic inversion. While the predicted gravity matches observations in parts of the model, the overall correlation is not satisfactory. In this paper we suggest a method of constraining the tomographic inversion to fit the gravity observations simultaneously with the seismic travel time data. The method is shown to work well with synthetic data in 3 dimensions where the assumption of Birch's law holds strictly. If the sources of the gravity anomalies are assumed to be spatially localized, integration can be carried out over a relatively small volume below the observation points and sparse matrix techniques can be applied. We have applied the constrained inversion method to western Washington using 4,387 shallow earthquakes, to depths of 40.0 km, (36,865 raypaths) convering a 150×250 km region and found that the gravitational constraints may be satisfied with minor effect on the degree of misfit to the seismic data.

Key words

Seismic tomography joint inversion gravity regularization Puget sound western Washington 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Aki, K., Christoffersson, A., andHusebye, E. S. (1977),Determination of the Three-dimensional Seismic Structure of the Lithosphere, J. Geophys. Res.82, 277–296.Google Scholar
  2. Birch, F. (1961),The Velocity of Compressional Waves in Rocks to 10 Kilobars, 2, J. Geophys. Res.66, 2199–2224.Google Scholar
  3. Bonini, W. E., Hughes, D. W., andDanes, Z. F. (1974),Complete Bouguer Gravity Anomaly Map of Washington, Washington Division of Geology and Earth Resources, Scale approximately 1:500,000.Google Scholar
  4. Backus, G., andGilbert, G. (1968),The Resolving Power of Gross Earth Data, Geophys. J. R. astr. Soc.266, 169–205.Google Scholar
  5. Chiu, S. K. L., Kanasewich, E. R., andPhadke, S. (1986),Three-dimensional Determination of Structure and Velocity by Seismic Tomography, Geophys.51 (8), 1559–1571.Google Scholar
  6. Chou, C. W., andBooker, J. R. (1979),A Backus-Gilbert Approach to Inversion of Travel-time Data for Three-dimensional Velocity Structure, Geophys. J. R. astr. Soc.59, 325–344.Google Scholar
  7. Crosson, R. S. (1976),Crustal Structure Modelling of Earthquake Data. 1. Simultaneous Least-squares Estimation of Hypocenter and Velocity Parameters, J. Geophys. Res.71 (17), 3036–3046.Google Scholar
  8. Dines, K. A., andLytle, R. J. (1979),Computerized Geophysical Tomography, Proc. IEEE67, 1065–1073.Google Scholar
  9. Evans, J. R., andZucca, J. J. (1988),Active High-resolution Seismic Tomography of Compressional Wave Velocity and Attenuation Structure at Medicine Lake Volcano, Northern California Cascade Range, J. Geophys. Res.93, 15016–15036.Google Scholar
  10. Gower, H. D., Yount, J. C., andCrosson, R. S. (1985),Seismotectonic Map of the Puget Sound Region, Washington, Map I-1613, U.S. Geol. Survey.Google Scholar
  11. Hearn, T. M., andClayton, R. W. (1986),Lateral Velocity Variations in Southern California. 1. Results for the Upper Crust from Pg Waves, Bull. Seismol. Soc. Am.76 (2), 495–427.Google Scholar
  12. Herman, G. T.,Image Reconstructions from Projections (Academic Press, New York 1980).Google Scholar
  13. Ho-Liu, P., Kanamori, H., andClayton, R. W. (1988),Applications of Attenuation Tomography to Imperial Valley and Cos-Indian Wells Region, Southern California, J. Geophys. Res.93, 10501–10520.Google Scholar
  14. Humphreys, E., Clayton, R. W., andHager, B. H. (1984),A Tomographic Image of Mantle Structure Beneath Southern California, Geophys. Res. Lett.11 (7), 625–627.Google Scholar
  15. Inoue, H., Fukao, Y., Tanabe, K., andOgata, Y. (1990),Whole Mantle P-wave Travel Time Tomography, Phys. Earth and Planet. Int.59, 294–328.Google Scholar
  16. Ivansson, S. (1986),Seismic Borehole Tomography—Theory and Computational Methods, Proc. IEEE74, 2.Google Scholar
  17. Jupp, D. L. B., andVozoff, K. (1975),Stable Iterative Methods for the Inversion of Geophysical Data, Geophys. J. R. astr. Soc.42, 957–976.Google Scholar
  18. Kissling, E., Ellsworth, W. L., andCockerham, R. S. (1984),Three-dimensional Structure of the Long Valley Caldera, California, Region by Geotomography, Proc. of Workshop XIX, Active Tectonic and Magmatic Processes beneath Long Valley Caldera, Eastern California, 1, U.S. Geol. Surv. Open File Report, 84-939, 188–220.Google Scholar
  19. Lees, J. M.,Seismic Tomography in Western Washington (University of Washington, Ph.D. Thesis 1989).Google Scholar
  20. Lees, J. M., andCrosson, R. S.,Bayesian ART versus conjugate gradient methods in tomographic seismic imaging: An application at Mount St. Helens, Washington, InSpatial Statistics and Imaging: Proceedings of the 1988 AMS-IMS-SIAM Summer Research Conference (ed. Posollo, A.) (in press 1991).Google Scholar
  21. Lees, J. M., andCrosson, R. S. (1989),Tomographic Inversion for Three-dimensional Velocity Structure at Mount St. Helens Using Earthquake Data, J. Geophys. Res.94 (B5), 5716–5728.Google Scholar
  22. Lees, J. M., andCrosson, R. S. (1990),Tomographic Imaging of Local Earthquake Delay Times for Three-dimensional Velocity Variation in Western Washington, J. Geophys. Res.95 (B4), 4763–4776.Google Scholar
  23. Lines, L. R., Schultz, A. K., andTreitel, S. (1988),Cooperative Inversion of Geophysical Data, Geophysics 53 (1), 8–20.Google Scholar
  24. Meissner, R.,The Continental Crust: A Geophysical Approach (Academic Press, Orlando 1986).Google Scholar
  25. Menke, W.,Geophysical Data Analysis: Discrete Inverse Theory (Academic Press, Orlando 1984).Google Scholar
  26. Nakanishi, I. (1985),Three-dimensional Structure Beneath the Hokkaido-Tohoku Region as Derived from a Tomographic Inversion of P-arrival Times, J. Phys. Earth33, 241–256.Google Scholar
  27. Neumann-Denzau, G., andBehrens, J. (1984),Inversion of Seismic Data Using Tomographical Reconstruction Techniques for Investigations of Laterally Inhomogeneous Media, Geophys. J. R. astr. Soc.79, 305–315.Google Scholar
  28. O'Sullivan, F. (1986),A Statistical Perspective on Ill-posed Inverse Problems, Stat. Sci.1 (4), 502–527.Google Scholar
  29. Oppenheimer, D. H., andHerkenhoff, K. E. (1981),Velocity Density Properties of the Lithosphere from Three-dimensional Modeling at the Geysers-Clear Lake Region, California, J. Geophys. Res.86, 6057–6065.Google Scholar
  30. Paige, C. C., andSaunders, M. A. (1982),LSQR: An Algorithm for Sparse Linear Equations and Sparse Least Squares, Trans. Math. Software8, 43–71.Google Scholar
  31. Pavlis, G. L. (1986),Geotomography Using Refraction Fan Shots, J. Geophys. Res.91, 6522–6534.Google Scholar
  32. Rodi, W. L., Jordan, T. H., Masso, J. F., andSavino, J. M. (1980),Determination of the Three-dimensional Structure of the Eastern Washington from the Joint Inversion of Gravity and Earthquake Travel Time Data, Final Tech. Rep. SSS-R-80-4516, Systems, Science and Software, La Jolla, California.Google Scholar
  33. Savino, J. M., Rodi, W. L., Goff, R. C., Jordan, T. H., Alexander, J. H., andLambert, D. G. (1977),Inversion of Combined Geophysical Data for Determination of Structure Beneath the Imperial Valley Geothermal Region., Final Tech. Rep. SSS-R-78-3412 to the Department of Energy, Systems, Science and Software, La Jolla, California.Google Scholar
  34. Spakman, W., andNolet, G.,Imaging algorithms, accuracy and resolution in delay time tomography, InMathematical Geophysics (ed. Vlaar, N. J.) (D. Reidel Publishing Co. 1988) pp. 155–187.Google Scholar
  35. Stacey, F. D.,Physics of the Earth (John Wiley & Sons, Inc., New York 1977).Google Scholar
  36. Stanley, W. D., Finn, C., andPlesha, J. L. (1987),Tectonics and Conductivity Structures in the Southern Washington Cascades, J. Geophys. Res.92, 10,179–10,193.Google Scholar
  37. Walck, M. C. (1988),Three-dimensional V p/V s Variations for the Coso REgion, California, J. Geophys. Res.93, 2047–2052.Google Scholar
  38. Walck, M. C., andClayton, R. W. (1987),P Wave Velocity Variations for the Coso Region, California, Derived from Local Earthquake Travel Times, J. Geophys. Res.92, 393–405.Google Scholar

Copyright information

© Birkhäuser Verlag 1991

Authors and Affiliations

  • J. M. Lees
    • 1
  • J. C. VanDecar
    • 2
  1. 1.Institute for Crustal StudiesUniversity of CaliforniaSanta BarbaraUSA
  2. 2.Geophysics ProgramUniversity of WashingtonSeattleUSA

Personalised recommendations