Migration of fluids beneath yellowstone caldera inferred from satellite radar interferometry

Science

Volumn 282, Issue 5388, 1998, Pages 458-462

  Wicks Jr , Charles ^a   Thatcher, Wayne ^a   Dzurisin, Daniel ^b  

^a U S GEOLOGICAL SURVEY   (United States)

^b CASCADES VOLCANO OBSERVATORY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CALDERA; DEFORMATION; HYDROTHERMAL FLUID; MAGMATISM; SUBSIDENCE; SYNTHETIC APERTURE RADAR;

EARTHQUAKE; GEOLOGY; INTERFEROMETRY; LIQUID; MIGRATION; PRIORITY JOURNAL; REVIEW; TELECOMMUNICATION; UNITED STATES; VOLCANO;

UNITED STATES;

EID: 3543148236     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.282.5388.458     Document Type: Review

References (29)

1. R. B. Smith and L. W. Braille, J. Volc. Geotherm. Res. 61, 121 (1994).
2. R. L. Christiansen, in Explosive Volcanism: Inception, Evolution, and Hazards (National Academy Press, Washington, DC, 1984), pp. 84-95.
3. R. O. Fournier and A. M. Pitt, Transactions of the Geothermal Resources Council 1985: International Symposium on Geothermal Energy, C. Stone, Ed. (Geothermal Resources Council, Honolulu, HI, 1985), pp. 319-327.
4. W. W. Locke and G. A. Meyer, J. Geophys. Res. 99, 20079 (1994).
5. K. L. Pierce, K. P. Cannon, G. A. Meyer, Eos 78, 802 (1997).
6. J. R. Pelton and R. B. Smith, Science 206, 1179 (1979); J. Geophys. Res. 87, 2745 (1982).
7. J. R. Pelton and R. B. Smith, Science 206, 1179 (1979); J. Geophys. Res. 87, 2745 (1982).
8. D. Dzurisin and K. M. Yamashita, J. Geophys. Res. 92, 13753 (1987).
9. D. Dzurisin, J. C. Savage, R. O. Fournier, Bull. Volc. 52, 247 (1990).
10. D. Dzurisin, K. M. Yamashita, J. W. Kleinman, ibid. 56, 261 (1994).
11. F. Arnet et al., Geophys. Res. Lett. 24, 2741 (1997).
12. C. M. Meertens and R. B. Smith, ibid. 18, 1763 (1991).
13. D. Massonnet, P. Briole, A. Arnaud, Nature 375, 567 (1995).
14. Fringes from orbital errors (inaccuracies in satellite positions) have been corrected for by subtracting a plane from each interferogram. The dominant orbital errors appear as nearly parallel fringes, and where coherence is good across the image the plane is easily found by inspection. We used inspection to set bounds for a grid search, then accepted the plane that gave a minimum variance-corrected interferogram. Because of poor coherence, the planes used to correct images in Fig. 2, E and F, were more qualitative in nature (there were no minimum variance solutions). The magnitude of tilt across each image is as follows: 30 mm (Fig. 2A), 300 mm (Fig. 2B), 220 mm (Fig. 2C), 300 mm (Fig. 2D), 220 mm (Fig. 2E), and 110 mm (Fig. 2F). These magnitudes are much larger than any signature that could be expected from regional tilting.
15. We assessed the DEM inaccuracies by forming interferograms from SAR images paired from summers of the same year, where the pairs had low altitudes of ambiguity (∼25 m). These pairs were sensitive to DEM inaccuracies and (because of the short time interval) fairly coherent. Inaccuracies appear to be generally less than 10 m, with the exception of a small area off the southeast tip of Hebgen Lake (HL) that is in error by ∼25 m. This DEM artifact has the largest effect in Fig. 2B (Table 1), where it appears as an area with half a fringe of signal, which could be interpreted as ∼14 mm of line-of-sight subsidence. The effect of the DEM artifact near HL is smallest in Fig. 2A (Table 1), where it would appear as an area with only ∼1.5 mm of subsidence.
16. H. A. Zebker and J. Villasenor, IEEE Trans. Geosci. Remote Sensing 30, 950 (1992).
17. An initial model was obtained by forward modeling to fit ∼400,000 data pixels (Fig. 2B). Seven model parameters were estimated for each of the two sills as follows: 1. East location of sill origin. 2. North location of sill origin (the origin of the sill specifies the geographic position of the sill by specifying one corner of a rectangle). 3. Sill dip. 4. Sill strike. 5. Sill length. 6. Sill width. 7. Amount of compaction (directed perpendicular to the sill surface). A Monte Carlo search was first used to refine the forward model, then used to estimate bounds on the model parameters. Any model with a variance increase (relative to the best-fitting model) that an F test revealed to be significant at the 95% level was taken as an acceptable model - indistinguishable from the minimum variance solution at the 95% level. The range of model parameters spanned by the acceptable models was used to constrain the depths and volume changes given in the text. The dip of the sill-like bodies is 0° ± 12°.
18. D. S. Miller and R. B. Smith, in preparation.
19. D. W. Vasco, R. B. Smith, C. L. Taylor, J. Geophys. Res. 95, 19839 (1990).
20. Because the interferograms in Fig. 2 have varying amounts of incoherence (indicated by the amount of image speckle) on top of a long-wavelength signal, we averaged the interferogram phases (which are all measured in multiples of 2π) over a number of pixels. In most of the caldera area, this enabled us to unwrap the phases. Unwrapping translates the interferogram phases into line-of-sight displacement by taking care of the 2nπ uncertainty in the phases. We averaged the phase values over a square area of pixels until the unwrapped phases of the pixels occupied by the benchmarks were similar to the unwrapped phases of each of the surrounding eight pixels. We then increased the number of pixels to the next odd number squared and repeated the phase unwrapping. For each line in Fig. 4 labeled InSAR, we plotted displacement from 36 displacement estimates (the benchmark pixel and the surrounding eight pixels with four different pixel averages). For Fig. 4, A through C, the uncertainties inferred from this procedure (the spread of the lines) is largest from 0 to 12 km where the leveling line runs along the edge of YL (the lake produces essentially random interferogram phases). The heavily speckled nature of Fig. 2F from 0 to 12 km along the leveling line appears to be the cause of the poor estimates of displacement there.
21. In comparing leveling and InSAR displacements, we are assuming that the satellite line-of-sight measurements in Fig. 4 represent predominantly vertical deformation. However, the satellite line of sight is inclined 23° to the vertical, so horizontal displacement may be mapped into range displacement. We assessed the magnitude of the error introduced by using this assumption by computing the effect of horizontal displacements in the synthetic (model) interferogram (Fig. 3B). The results suggest that the largest error along the leveling route introduced by this assumption is less than 3 mm, located where the route crosses the edges of the smaller sill-like body (Figs. 1 and 2).
22. H. Tarayre and D. Massonnet, Geophys. Res. Lett. 23, 989 (1996); H. A. Zebker, P. A. Rosen, S. Hensley, J. Geophys. Res. 102, 7547 (1997).
23. H. Tarayre and D. Massonnet, Geophys. Res. Lett. 23, 989 (1996); H. A. Zebker, P. A. Rosen, S. Hensley, J. Geophys. Res. 102, 7547 (1997).
24. -6 Pa · s (water and vapor, respectively).
25. We use the term magmatic fluids to refer to magma (molten rock) or volatile gases and liquids released from magma, whereas we use the term hydrothermal fluids to refer to steam and hot water that are mostly of meteoric origin.
26. From the snapshots of subsidence (Fig. 2) we cannot discern whether the subsidence deformation front moves from southwest to northeast or northeast to southwest. Because the inception of uplift was captured in Fig. 2C, however, we can conclude that the uplift deformation front moves from the northeast to the southwest (Fig. 2F).
27. D. Massonnet and T. Rabaute, IEEE Trans. Geosci. Rem. Sensing 31, 455 (1993).
28. K. Feigl and E. Dupré, Comp. Geosci., in press.
29. We thank our colleagues R. L. Christiansen and J. C. Savage and two anonymous reviewers for thorough technical reviews of the manuscript; R. O. Fournier, D. J. Stevenson, E. Brodsky, D. Massonnet, and N. Pourthie for helpful discussion; and P. Wessel and W. Smith for GMT software [Eos 72, 441 (1991)]. This research was supported by the Volcano Hazards Program, USGS. W.T. was supported by a visiting professorship at the Division of Geological Sciences, California Institute of Technology, while some of the work reported here was carried out.