Magma intrusion beneath Long Valley caldera confirmed by temporal changes in gravity

Science

Volumn 285, Issue 5436, 1999, Pages 2119-2122

  Battaglia, M ^a   Roberts, C ^b   Segall, P ^a  

^a STANFORD UNIVERSITY   (United States)

^b U S GEOLOGICAL SURVEY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

SILICATE;

GRAVITY ANOMALY; IGNEOUS INTRUSION; MAGMATISM;

ARTICLE; EARTHQUAKE; ENVIRONMENTAL MONITORING; GEOLOGY; GRAVITY; POROSITY; PRIORITY JOURNAL; THERMAL ANALYSIS; VOLCANIC ASH; VOLCANO;

UNITED STATES;

EID: 0032843916     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.285.5436.2119     Document Type: Article

References (36)

1. R. L. Smith and R. A. Bailey, Mem. Geol. Soc. Am. 116, 613 (1968).
2. R. I. Tilling and J. Dvorak, Nature 363, 125 (1993).
3. G. Berrino, J. Volcanol. Geotherm. Res. 61, 293 (1994).
4. D. Dzurisin, K. M. Yamashita, J. W. Kleinman, Bull. Volcanol. 56, 261 (1994).
5. G. De Natale, F. Pingue, P. Allard, A. Zollo, J. Volcanol. Geotherm. Res. 48, 199 (1991).
6. C. Wicks Jr., W. Thatcher, D. Dzurisin, Science 282, 458 (1998).
7. C. Berrino, H. Rymer, G. C. Brown, G. Corrado, J. Volcanol. Geotherm. Res. 53, 11 (1992).
8. R. C. Jachens and C. W. Roberts, J. Geophys. Res. 90, 11210 (1985).
9. A. A. Eggers, J. Volcanol. Geotherm. Res. 33, 201 (1987).
10. Measurements made in the same month may minimize seasonal variations in water table [F. Arnet et al., Geophys. Res. Lett. 24, 2741 (1997)]; sites on low-porosity outcrops (32) or near sea level (30) may minimize water table effects on gravity changes.
11. R. A. Bailey, Map 1-1933 (U.S. Geological Survey, Reston, VA, 1989).
12. _ and D. P. Hill, Geosci. Can. 17, 175 (1990).
13. J. Langbein et al., J. Geophys. Res. 100, 12487 (1995).
14. B. R. Julian, Nature 303, 323 (1983).
15. C. W. Roberts, R. C. Jachens, R. Morin, U.S. Geol. Surv. Rep. 88-50 (1988).
16. The measured gravity differences at each station were processed with a least squares method to obtain one gravity value following the methods described by R. C. Jachens [in 7980 Eruptions of Mount St. Helens, Washington (U.S. Geological Survey, Reston, VA, 1981), pp. 175-181].
17. J. F. Howle and C. D. Farrar, U.S. Geol. Surv. Open File Rep. 96-382 (1996).
18. D. Dzurisin, personal communication.
19. P. Goovaerts, Geostatistics for Natural Resources Evaluation (Oxford Univ. Press, New York, 1997).
20. Kriging provides only an incomplete measure of local accuracy and no estimation of joint accuracy when several locations are considered together. Gaussian simulations are designed specifically to provide such measures. Gaussian simulation is the process of drawing alternative, equally probable, joint realizations of a random variable (in our case, the uplift or change in water table depth at a given location) that follows a multivariate Gaussian distribution. The parameters of the Gaussian distribution (mean and variance) are determined by kriging. The random sampling is such that all the realizations fit the existing data exactly. The variance of a set of simulated values provides a measure of local uncertainty for the attribute of interest.
21. S. Rouhani and D. E. Meyers, Math. Geol. 22, 611 (1990).
22. M. L. Sorey, R. E. Lewis, F. H. Olmsted, U.S. Geol. Surv. Prof. Pap. 1044-A (1978).
23. The fact that the station in the eastern caldera with the large residual gravity change experienced an unusually small raw gravity change (-4 ± 7 μgal) compared with neighboring stations in the eastern caldera (with gravity changes of -46 ± 10, -30 ± 14, -42 ± 11 μgal) suggests possible measurement errors at this site (see Fig. 3A).
24. B. Efron and R. Tibshirani, Stat. Sci. 1, 54 (1986). The data were randomly resampled with replacement (that is, some stations appear multiple times and others not at all). The resampled data set was inverted for source depth, and the process was repeated several thousand times. Ninety-five percent confidence intervals were determined by ordering the bootstrap results and excluding the smallest and largest 2.5% of the distribution.
25. K. Mogi, Bull. Earthquake Res. Inst. 36, 99 (1958).
26. R. S. Charmicael, Ed., Handbook of Physical Rock Properties, vol. III (CRC Press, Boca Raton, FL, 1984).
27. J. B. Walsh and J. R. Rice, J. Geophys. Res. 84, 165 (1979).
28. The estimated volume from gravity is based on data from July 1982 to July 1998. Because leveling was not conducted in 1998, the estimated volume from leveling is based on data from July 1982 to July 1997. Volume change between 1997 and 1998 is thus not accounted for.
29. C. M. Weiland, L. K. Steck, P. B. Dawson, V. A. Korneev, J Geophys. Res. 100, 20379 (1995).
30. C. McKee, J. Mori, B. Talai, in Volcanic Hazards; Assessment and Monitoring (Springer-Verlag, Berlin, 1989), pp. 399-428.
31. B. Talai et al., Bull. Global Volcanism Network 22 (no. 4) (1997) (available at http://www.volcano.si.edu/gvp/ volcano/region05/newbrit/rabaul/var_01.htm 2204).
32. J. B. Rundle and J. H. Whitcomb, J. Geophys. Res. 91, 12675 (1986).
33. F. Barberi, in Monitoring and Mitigation of Volcano Hazards (Springer-Verlag, Berlin, 1996), pp. 771-786.
34. C. D. Farrar et al., Nature 376, 675 (1995).
35. M. L. Sorey, C. D. Farrar, G. A. Marshall, J. F. Howle, J. Geophys. Res. 100, 12475 (1995).
36. This work would have not been possible without support and data from several individuals and institutions. In particular, we thank R. Bailey, D. Dzurisin, C. Farrar, D. Hill, J. Langbein, J. Murray, and W. Thatcher.