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An Elusive Blind-Thrust Fault Beneath Metropolitan Los Angeles

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An Elusive Blind-Thrust Fault Beneath Metropolitan Los Angeles R EPORTS 5 The intercept of the line with the abscissa yields Di/D 1/4, which is an extreme case, differs only by 36. N. A. Sulpice and R. J. D’Arcy, J. Phys. E 3, 477 (1970). 7% as compared with D 5 0. DV. This geometry-independent constant is i 37. Electrical charging due to the electron beam cannot 31. Microscopy was performed with a Philips CM30 200- account for the effect, because the charge found to characteristic for the specific nanotube under kV high-resolution TEM. reside on the nanotubes is positive rather than neg- investigation and is typically on the order of 32. The ripple mode may be a precursor to buckling, but ative. Furthermore, the amplitude of vibration at several volts. Similarly, attaching nanoscopic it should not be confused with bucking. Buckling (in resonance does not change with electron dose, as it contrast to rippling) is characterized as an instability would if electron beam charging were important. conducting particles to the nanotubes facilitates giving rise to a nonlinear response. It occurs in highly 38. M. Gurgoze, J. Sound Vib. 190, 149 (1996). measurements of their work functions. stressed nanotubes (and beams) and manifests as 39. We thank U. Landman, R. L. Whetten, L. Forro, and A. The methods developed here are also well one or several kinks with very small radii of curvature Zangwill for fruitful discussion and R. Nitsche for his suited to measure masses in the picogram-to- (about 1 to 10 nm). It is accompanied by abrupt analysis of the static bent nanotube. D.U. thanks the change in the effective force constant and may cause Centre Interdepartemental de Microscopy Electronique, femtogram mass range, as demonstrated in Fig. irreversible damage. The observed effect may be Ecole Polytechnique Federale, for the use of the Philips 4A, which shows the resonance of a carbon related to the rippling found in classical beams as a CM30 microscope for Fig. 3, B through D, and the particle that is attached to the end of a nanotube precursor to buckling [see S. Kyriakides and G. T. Ju, Brazilian Council for Scientific and Technological Re- Int. J. Solids Struct. 29, 1117 (1992)]. search. Supported by the Army Research Office, grants (38). The mass of this particle was determined 33. In the bulk, the other elastic moduli are at least a DAAG 55-97-0133 ( W.A.d.H. and P.P.), by NSF9733160 from the resonance frequency of the structure factor of 5 and as much as a factor of 50 smaller than ( Z.L.W.), and by NSFDMR-9971412 (W.A.d.H. and that of C . and was found to be M 5 22 6 6fg(1fg5 11 Z.L.W.) –15 34. D. Ugarte, Nature 352, 707 (1992). 10 g). This value is near that calculated from 35. Lord Kelvin, Philos. Mag. 46, 82 (1898). 4 December 1998; accepted 26 January 1999 the measured geometry, assuming bulk amor- phous carbon density—that is, M ' 30 fg. This nanobalance method can be applied to other particles of similar dimensions, such as viruses. An Elusive Blind-Thrust Fault References and Notes Beneath Metropolitan Los 1. S. Iijima, Nature 354, 56 (1991). 2. J. W. Mintmire, B. I. Dunlap, C. T. White, Phys. Rev. Lett. 68, 631 (1992). Angeles 3. M. S. Dresselhaus, G. Dresselhaus, R. Saito, Carbon 33, 1 2 883 (1995). John H. Shaw * and Peter M. Shearer 4. D. L. Carroll et al., Phys. Rev. Lett. 78, 2811 (1997). 5. T. W. Ebbesen, Phys. Today 49, 26 (1996). Seismic reflection profiles, petroleum wells, and relocated earthquakes reveal the 6. W. A. de Heer, A. Chatelain, D. Ugarte, Science 270, 1179 (1995). presence of an active blind-thrust fault beneath metropolitan Los Angeles. A 7. S. Frank, P. Poncharal, Z. L. Wang, W. A. de Heer, ibid. segment of this fault likely caused the 1987 Whittier Narrows (magnitude 6.0) 280, 1744 (1998). earthquake. Mapped sizes of other fault segments suggest that the system is 8. J. Liu et al., ibid., p. 1253. 9. A. Thess et al., ibid. 273, 483 (1996). capable of much larger (magnitude 6.5 to 7) and more destructive earthquakes. 10. D. H. Robertson, D. W. Brenner, J. W. Mintmire, Phys. Rev. B 45, 12592 (1992). Damages exceeding $35 billion from the 1994 (8–10) in northern Orange County (Fig. 2). 11. R. S. Ruoff and D. C. Lorents, Carbon 33, 925 (1995). Northridge [magnitude (M) 6.7] earthquake (1), These folds grew in the Quaternary while 12. M. M. Treacy, T. W. Ebbesen, J. M. Gibson, Nature 38, combined with recent evidence of larger (.M sediments were deposited above them, yield- 678 (1996). 13. B. I. Yakobson, C. J. Brabec, J. Bernholc, Phys. Rev. Lett. 7) events in the geologic record (2), have fo- ing patterns of deformed strata that record 76, 2511 (1996). cused attention on the hazards posed by thrust fold growth and fault slip (11). These de- 14. M. R. Falvo et al., Nature 389, 582 (1997). faults to metropolitan Los Angeles. Efforts to formed strata are particularly well imaged in 15. J. P. Lu, Phys. Rev. Lett. 79, 1297 (1997). 16. E. Wong, P. Sheehan, C. Lieber, Science 277, 1971 assess and mitigate these hazards are compli- the Santa Fe Springs anticline (Fig. 1). (1997). cated, however, because thrust faults beneath On the basis of fault-related folding theo- 17. C.-H. Kiang et al., Phys. Rev. Lett. 81, 1869 (1998). the city are typically blind, meaning that they ries (11), the shape of the growth fold at 18. W. H. Knechte et al., Appl. Phys. Lett. 73, 1961 lie concealed beneath Earth’s surface (3, 4). Santa Fe Springs suggests that an underlying (1998). 19. S. Iijima, C. Brabeck, A. Maiti, J. Bernholc, J. Chem. Here, we used high-resolution, subsurface im- fault, which we call the Puente Hills thrust, Phys. 104, 2089 (1996). ages acquired by the petroleum industry (Fig. 1) dips to the north and extends upward into the 20. T. Kuzumaki et al., Phil. Mag. A 77, 1461 (1998). and relocated seismicity to map a large blind- Pliocene Fernando Formation. This fault 21. J.-P. Salvetat et al., Adv. Mat., in press. 22. N. Yao and V. Lordi, J. Appl. Phys. 84, 1939 (1998). thrust system lying directly beneath the metro- shape and position are consistent with a 23. G. Gao, T. Cagin, W. A. Goddard, Nanotechnology 9, politan area (Fig. 2). north-dipping reflection beneath the anticline 184 (1998). Many blind thrusts produce near-surface that cuts across bedding. This reflection is 24. B. T. Kelly, Physics of Graphite (Applied Science, Lon- folds that grow during repeated earthquakes observed on more than 10 seismic profiles don, 1981). 25. N. Osakabe et al., Appl. Phys. Lett. 70, 940 (1997). (3–5) in response to motions through bends in and persists through a range of processing 26. T. W. Ebbesen and P. M. Ajayan, Nature 358, 220 fault planes or above propagating fault tips, steps aimed to remove noise and artifacts (1992). We caution that different production recipes and their shapes reflect underlying fault ge- (12). Thus, we interpret this reflection as an can yield different results; in particular, defect densities may vary substantially from one laboratory to the next ometries and slip (6, 7). Seismic reflection image of the fault surface, caused by velocity (as is the case with crystal growing). For example, profiles and information from oil wells reveal and density contrasts that exist across the catalytically grown tubes are usually very defective. In a series of these anticlines extending from fault plane. contrast, the nanotube material used in this work [in- cluding (31)] was from the same stock as was used in downtown Los Angeles to the Coyote Hills Fault-plane reflections in a series of seis- our previous work (6, 7) and was of high quality. mic profiles define an east-west–striking sur- 27. The TEM used was a JEOL 100C (100 kV ) at the face that dips about 27° to the north. We School of Materials Science and Engineering, Georgia 1Department of Earth and Planetary Sciences, Harvard extrapolated beyond the limits of the fault- Institute of Technology. 2 University, Cambridge, MA 02138, USA. Institute of plane reflections, using fold shape, as imaged 28. D. J. Griffiths and Y. Li, Am. J. Phys. 64, 706 (1996). Geophysics and Planetary Physics, Scripps Institute of 29. L. Meirovich, Elements of Vibration Analysis (McGraw- Oceanography, University of California, San Diego, La in the seismic profiles, to predict the fault Hill, New York, ed. 2, 1986). Jolla, CA 92093–0225, USA. shape (6, 11) and map the fault surface (Fig. 30. Di was not measured for all nanotubes, and in those cases it was not included in the calculations. Howev- *To whom correspondence should be addressed. E- 2). The mapped fault extends 40 km along er, the value for E is rather insensitive to Di, because mail: [email protected] strike and includes three distinct geometric 1516 5 MARCH 1999 VOL 283 SCIENCE www.sciencemag.org R EPORTS segments, termed Los Angeles, Santa Fe bounds on these depth estimates are quite model. On the basis of the depths obtained Springs, and Coyote Hills. This fault system small (0.1 to 0.3 km), but these numbers do from the two methods, we estimate that the is distinct from the previously documented not include the uncertainties in the velocity mainshock depth is 13 6 1 km. This earth- Elysian Park fault (10, 13) and thus repre- sents a hazard that has not been previously N Exxon considered.
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