A Comparison and Test of Various Site-Response Estimation Techniques, Including 3 That Are Not Reference-Site Dependent

Publication Type  Journal Article
Year of Publication  1995
Authors  Field, E. H.; Jacob, K. H.
Journal Title  Bulletin of the Seismological Society of America
Volume  85
Issue  4
Pages  1127-1143
Journal Date  Aug
ISBN Number  0037-1106
Accession Number  ISI:A1995RT43100012
Key Words  san-francisco-bay; teleseismic p-waveforms; loma-prieta earthquake; 5-second micro-tremors; new-york-state; s-wave coda; ground motion; source parameters; propagation characteristics; central california
Abstract  

We compare various site-response estimation techniques using aftershock data of the 1989 Loma Prieta earthquake collected in Oakland, California. Because of recent interest in comparing results from weak and strong motion (to infer any nonlinearity) and between direct S and coda waves, we pay particular attention to the uncertainties, First, sediment to bedrock spectral-ratio estimates between pairs of sites are compared with those obtained from various generalized-inversion approaches where the source and site effects of multiply recorded events are solved for simultaneously. We find that the site amplification factors are very similar among these approaches, but that the uncertainties can be significantly different depending on how the data are weighted.We also examine and test three site-response estimation techniques that do not rely on a reference site to estimate source and path effects. The first involves a parameterized source- and path-effects inversion. Even when the bedrock data are excluded from consideration, this approach is found to reveal the frequency dependence of site response at each of the sediment sites. The second technique involves taking horizontal- to vertical-component spectral ratios (receiver-function-type estimates) of shear-wave aftershock data. These are also found to reveal the frequency dependence of site response at the sediment sites, and the results for the bedrock site are relatively flat and near unity. The third estimate is formed by taking horizontal- to vertical-component ratios of ambient seismic noise, and these are shown to reveal the fundamental resonant frequency of the sediment sites. Unfortunately, discrepancies exist among all of the site-response estimates (and with one-dimensional predictions) with respect to a frequency-independent scaling factor. Nevertheless, the highly frequency-dependent character of site response is well constrained, and the fact that non-reference-site-dependent methods are capable of revealing this is promising for site-specific hazard assessments in regions that lack adequate reference sites.

Notes  

Rt431Times Cited:161Cited References Count:67

URL  <Go to ISI>://A1995RT43100012