This paper describes the development and application of a new method for generation of realistic synthetic earthquake time histories compatible with multiple-damping design spectra. The effectiveness of this new method is demonstrated by applying it to adjust actual earthquake time histories to match the design spectra while minimizing perturbations on their characteristics. The paper also demonstrates that seismic responses of structures based on such spectrum-compatible realistic time histories are consistent with those obtained from analyses using an ensemble of time histories.
Sieh and Jahns (1984) forecasted that the next moderate Parkfield earthquake might trigger a major earthquake along a fault segment greater than 30 km long southeast of Cholame. Their forecast assumed (1) the slip was 3–4 m in 1857 and characteristic of the segment; (2) a slip rate of 3.4 cm/yr; and (3) full strain release in earthquakes.
Seismic design requirements for critical facilities normally require the development and application of a uniform hazard spectrum having a specified rerurn period. For a soil site, hazard results are often evaluated for bedrock level and soil surface. In many instances, use of soil hazard results can be problematic for a generic site response result because un-conservacive generic soil amplification functions may have been used in the ground morion attenuation model or a site specific result may be required.
Site-specific probabilistic seismic hazard assessments (PSHAs) and associated seismic design bases are critically dependent upon the local geological and geotechnical model. For reactor and critical non-reactor facilities on soil or softrock sites exhibiting strain-dependent behavior, estimates of site response can change significantly as site measurements and inferred structure evolve.
This paper compares a number of approximations used to estimate means and variances of continuous random variables and/ or to serve as substitutes for the probability distributions of such variables, with particular emphasis on three-point approximations.
In many cases the ground motions developed near the surface of a soil deposit during an earthquake may be attributed primarily to the upward propagation of shear waves from an underlying rock formation. If the ground surface, the rock surface, or the boundaries between different soil layers are inclined, analyses of the response of the soil deposit can be made only by techniques such as the finite-element method.
One of the fastest growing areas of Arizona is the eastern part of the Phoenix Basin near the communities of Chandler, Gilbert, Mesa, and Apache Junction. Much of this development has occurred on the piedmont near the base of the mountains where little of the surficial geology has ever been mapped. Because this area of the Phoenix Basin will continue to grow in the future, there is a need to understand the nature and distribution of surficial deposits.
It is well known that the most widely used earthquake magnitude scales, ML (local magnitude), M, (surface wave magnitude), and mb (body wave magnitude), are, in principle, unbounded from above. It is equally well known that, in fact, they are so bounded, and the reasons for this are understood in terms of the operation of finite bandwidth instrumentation on the magnitude-dependent frequency characteristics of the elastic radiation excited by earthquake sources.
The Wells and Coppersmith (1994) M–log A data set for continental earthquakes (where M is moment magnitude and A is fault area) and the regression lines derived from it are widely used in seismic hazard analysis for estimating M, given A. Their relations are well determined, whether for the full data set of all mechanism types or for the subset of strike-slip earthquakes.
Exposures we have excavated across the San Andreas fault contradict the hypothesis that part of the fault in the Carrizo Plain is unusually strong and experiences relatively infrequent rupture. The exposures record evidence of at least seven surface-rupturing earthquakes which have been approximately dated by accelerated mass spectrometry radiocarbon analysis of detrital charcoal and buried in situ plants.