Present-day deformation across the Basin and Range Province, western United States

Science

Volumn 283, Issue 5408, 1999, Pages 1714-1718

  Thatcher, Wayne ^a   Foulger, G R ^b   Julian, B R ^a   Svarc, J ^a   Quilty, E ^a   Bawden, G W ^a  

^a U S GEOLOGICAL SURVEY   (United States)

^b DURHAM UNIVERSITY   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

DEFORMATION; FAULT DISPLACEMENT; GPS;

ARTICLE; DENSITY GRADIENT; GEOGRAPHY; GEOLOGY; PRIORITY JOURNAL; ROCK; TEMPERATURE; TOPOGRAPHY; UNITED STATES;

UNITED STATES;

EID: 0033548630     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.283.5408.1714     Document Type: Article

References (30)

1. W. Hamilton, in Continental Extensional Tectonics, M. P. Coward, J. F. Dewey, P. L. Hancock, Eds. (Geological Society, London, 1987), vol. 28, pp. 155-176.
2. B. Wernicke, in The Cordilleran Orogen: Conterminous U. S.: The Geology of North America Volume G-3, P. W. Lipman, B. C. Burchfiel, M. L. Zoback, Eds. (Geological Society of America, Boulder, CO, 1992), pp. 553-581.
3. S. Hecker, "Quaternary tectonics of Utah with emphasis on earthquake-hazard characterization" (Bulletin 127, Utah Geological Survey, Salt Lake City, UT, 1993).
4. J. C. Dohrenwend, B. A. Schell, C. M. Menges, B. C. Moring, M. A. McKittrick, "Reconaissance photogeologic map of young (Quaternary and late Teritary) faults in Nevada" (Open-File Report 96-2, Nevada Bureau of Mines and Geology, Reno, NV, 1996).
5. D. M. dePolo and C. M. dePolo, "Earthquakes in Nevada 1852-1996" (Map 111, Nevada Bureau of Mines and Geology, Reno, NV, 1998).
6. D. F. Argus and R. G. Gordon, Geology 19, 1085 (1991).
7. T. H. Dixon, S. Robaudo, J. Lee, M. C. Reheis, Tectonics 14, 755 (1995).
8. R. A. Bennett, B. P. Wernicke, J. L. Davis, Geophys. Res. Lett. 25, 563 (1998).
9. L. J. Martinez, C. M. Meertens, R. B. Smith, ibid., p. 567.
10. J. C. Savage, M. Lisowski, W. H. Prescott, J. Geophys. Res. 97, 2071 (1992).
11. J. C. Savage, M. Lisowski, J. L. Svarc, W. K. Gross, ibid. 100, 20257 (1995).
12. The October 1992 survey was carried out with Turborogue GPS receivers with choke-ring antennas, and the September 1996 and September 1998 measurements were carried out with Ashtech Z12 receivers and Ashtech choke-ring antennas. The network consists of 47 stations strung about 15 to 30 km apart along U.S. Highway 50 and 16 stations spaced between 60 and 120 km apart to the north and south. The 16 bounding network stations and 8 additional Highway 50 stations were generally occupied on 4 consecutive days in each survey. Of the other Highway 50 sites, 23 were occupied on 2 consecutive days and the remaining 16 were observed on a single day. Most Highway 50 sites used National Geodetic Survey leveling benchmarks installed as long ago as 1932. Other sites used stainless steel plugs we cemented into bedrock outcrops. Data were reduced with Gipsy software release 4. Station positions for each epoch were derived in the ITRF96 reference frame, and velocity vectors were determined relative to stable North America. All station coordinates and site velocities may be accessed at the U.S. Geological Survey Web site (http://quake.wr.usgs.gov/QUAKES/ geodetic/gps/).
13. The VLBI-derived estimate of Sierra Nevada-stable North America relative motion near 37°N, 118°W is 12.1 ± 1.2 mm/year at an azimuth of 322° ± 5° (7). The average of GPS determinations from four stations within the Sierra Nevada block (open circles in Fig. 2) is 11.8 ± 1.6 mm/year at 308° ± 5°. Values between 119.8° and 120.3°W average 12.5 ± 1.5 mm/year at 299° ± 5°. The velocity of a VLBI station near Ely, NV, is 4.9 ± 1.3 mm/year at an azimuth of 262° ± 13° (7). The VLBI site lies roughly equidistant and ∼12 km from two of our stations [near 115°W (Fig. 2)] whose average velocity is 3.2 ± 1.6 mm/year at 303° ± 19°. Although the two estimates are consistent at the 2 SD level, our results from other GPS stations in the region suggest that velocities are generally directed more northwest and are smaller in magnitude than the nearly west-oriented value determined for the Ely VLBI site. Initial results from a 13-station continuous GPS array (8) located north of our network and roughly centered on 40°N show an increase in velocity west of the central Nevada seismic zone, which is consistent with our data. An inferred linear east-to-west increase in the east component of velocity (8) is not supported by our data. Instead, our data show an abrupt increase of east and north velocity components near 118°W.
14. R. K. Dokka and C. J. Travis, Tectonics 9, 311 (1990).
15. J. Sauber, W. Thatcher, S. Solomon, J. Geophys. Res. 91, 12683 (1986).
16. J. C. Savage, M. Lisowski, W. H. Prescott, Geophys. Res. Lett. 17, 2113 (1990).
17. S. K. Pezzopane and R. J. Weldon, Tectonics 12, 1140 (1993).
18. -1, which is comparable to many plate-driving and resisting forces. This force produces extensional stress in the elevated region and compressional stress in the adjacent lower lying crust [see D. L. Turcotte, in Mountain Building Processes, K.J. Hsu, Ed. (Academic Press, London, 1982), pp. 141-146]. The magnitude of these forces will differ if lateral density contrasts extend into the mantle. For example, the driving force will be smaller than computed above if the mantle lithosphere is colder and denser beneath the Sierra Nevada and Colorado Plateau than it is beneath the Basin and Range.
19. We assume that principal stress orientations estimated from earthquake fault plane solutions, borehole elongations, and slip directions on faults are coincident with incremental principal strains determined by GPS. M. L. Zoback [J. Geophys. Res. 94, 7105 (1989)] has estimated least principal stress orientations that are nearly east-west across the Wasatch fault near Ogden and N90°E to N120°E across our CPS network.
20. A. H. Lachenbruch and P. Morgan, Tectonophysics 174, 39 (1990).
21. -1, which is comparable to the effects of province margin topography given in (18). However, these authors also point out significant uncertainties in the computed force gradients due to poor constraints on the exact upper mantle density structure and its lateral variations.
22. J. C. Savage and R. O. Burford, J. Geophys. Res. 78, 832 (1973); J. C. Savage, ibid. 88, 4984 (1983).
23. J. C. Savage and R. O. Burford, J. Geophys. Res. 78, 832 (1973); J. C. Savage, ibid. 88, 4984 (1983).
24. L. B. Freund and D. M. Barnett, Bull. Seismol. Soc. Am. 66, 667 (1976). The horizontal displacement pattern in Fig. 3 is for a west-dipping fault. If the fault has an eastward dip, the pattern is reversed, with all local peaks replaced by troughs and vice versa (turn Fig. 3 upside down to visualize this). For dips shallower than 60°, the local peaks and troughs become progressively less prominent for the same slip distribution as that in Fig. 3.
25. The central Utah models use two 60°-dipping faults locked from the surface to a depth of 15 km. Slip of 4 mm/year is required across the Wasatch fault and of 2 mm/year across the Drum Mountain fault. These slip rates are surprisingly high and may be related to a discrepancy noted from the Wasatch fault near Ogden, where geologically estimated late Holocene slip rates are 1 to 2 mm/year [D. P. Schwartz and K. J. Coppersmith. J. Geophys. Res. 89, 5681 (1984)] and geodetic estimates are ∼5 mm/year (9, 10).
26. Some of the local velocity decreases seen at fault crossings of our network may be due to a sampling bias. Both coseismic fault slip and topographic height are expected to be a maximum near the center of each range and to decrease toward its ends. The interseismic strain accumulation rate (the velocity gradient normal to the fault) should generally mimic this pattern. Because highway engineers site roadways through the lowest available topographic gradient, most of our range-crossing stations are located either near the ends of active ranges or between adjacent ones. This bias will produce local along-strike velocity gradients and velocity minima near the ends of active ranges, which is qualitatively consistent with patterns seen in our data across central Utah and easternmost Nevada.
27. W. F. Brace and D. L. Kohlstedt, J. Geophys. Res. 85, 6248 (1980); L. J. Sonder and P. C. England, Earth Planet. Sci. Lett. 77, 81 (1986).
28. W. F. Brace and D. L. Kohlstedt, J. Geophys. Res. 85, 6248 (1980); L. J. Sonder and P. C. England, Earth Planet. Sci. Lett. 77, 81 (1986).
29. 1/2 [J. Langbein and H. Johnson, J. Geophys. Res. 102, 591 (1997)].
30. This work was supported by NASA's Dynamics of the Solid Earth Program. Help with GPS fieldwork was provided by G. Hamilton, J. Sutton, C. Stiffler, G. Marshall, R. Stein, K. Hodgkinson, M. Hofton, N. King, T. Sagiya, and B. Kilgore. Discussion with W. Hamilton, A. H. Lachenbruch, T. Parsons, W. H. Prescott, J. C. Savage, R. Simpson, G. Thompson, R. Wells, and M. L. Zoback is gratefully acknowledged. Careful reviews of the manuscript were provided by J. C. Savage, M. L. Zoback, R. B. Smith, and an anonymous reviewer.