MAGNITUDE SCALING FACTORS

In developing the "simplified procedure" for evaluating liquefaction resistance, Seed and Idriss (1982) compiled a sizable database from sites where liquefaction did or did not occur during earthquakes with magnitudes near 7.5. From this database, these investigators defined a conservative deterministic bound separating data indicative of liquefaction from data indicative of nonliquefaction. They then scaled this bound to other earthquake magnitudes using magnitude scaling factors (MSF). Because insufficient observational data were available for magnitudes other than 7.5, Seed and Idriss (1982) analyzed recorded ground motions and laboratory test data to define the original set of scaling factors. As more field performance data were collected, the observed occurrences and nonoccurrences of liquefaction for smaller earthquakes (magnitudes less than 7) indicated that the original Seed and Idriss (1982) MSF may have been overly conservative for smaller magnitudes. In response to this apparent overconservatism, Idriss reevaluated the original seismic and laboratory data, made corrections, linearized the data on a logarithmic plot, and developed a revised set of MSF. Abraseys (1988), Arango (1996), Andrus and Stokoe (this report) and Youd and Noble (herein) defined alternative sets of MSF based on empirical field observations. These MSF lie within a narrow range for M sub W <= 7.5. The workshop gained consensus that a range of MSF values should be suggested for engineering practice. Practitioners could then select MSF from within this range, depending on the degree of risk they or their clients are willing to accept for various applications. The lower bound for that recommended range is the MSF proposed by Idriss (Column 3, Table 1) and the upper bound for the range is the factors proposed by Andrus and Stokoe (Column 7, Table 1). For magnitudes greater than 7.5, the revised factors of Idriss should be used. These factors are smaller than the original Seed and Idriss (1982) factors, and hence lead to an increase of calculated liquefaction hazard compared to the old factors. The workshop participants agreed, however, that the original factors by Seed and Idriss (1982) may not have been adequately conservative for large magnitude earthquakes.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/10883800
• Corporate Authors:

  National Center for Earthquake Engineering Research

  State University of New York, Buffalo, Red Jacket Quadrangle, Box 610025
  Buffalo, NY  United States  14261-0025

  Brigham Young University

  Department of Civil and Environmental Engineering
  Provo, UT  United States  84602
• Authors:
  • Youd, T L
  • Noble, S K
• Conference:
  • NCEER Workshop on Evaluation of Liquefaction Resistance of Soils
  • Location: Salt Lake City, Utah
  • Date: 1996-1-5 to 1996-1-6
• Publication Date: 1997-12-31

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 149-166
• Serial:
  • National Center for Earthquake Engineering Research
  • Publisher: National Center for Earthquake Engineering Research
  • ISSN: 1088-3800

Subject/Index Terms

• TRT Terms: Earthquakes; Engineering; Liquefaction; Magnitude; Scaling factor; Soils
• Old TRIS Terms: Resistance
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00758967
• Record Type: Publication
• Report/Paper Numbers: Technical Report NCEER-97, -0022
• Files: TRIS
• Created Date: Jan 26 1999 12:00AM