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On using surface-source downhole-receiver logging to determine seismic slownesses

Soil Dynamics and Earthquake Engineering

By:
and
DOI: 10.1016/j.soildyn.2007.03.005

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Abstract

We present a method to solve for slowness models from surface-source downhole-receiver seismic travel-times. The method estimates the slownesses in a single inversion of the travel-times from all receiver depths and accounts for refractions at layer boundaries. The number and location of layer interfaces in the model can be selected based on lithologic changes or linear trends in the travel-time data. The interfaces based on linear trends in the data can be picked manually or by an automated algorithm. We illustrate the method with example sites for which geologic descriptions of the subsurface materials and independent slowness measurements are available. At each site we present slowness models that result from different interpretations of the data. The examples were carefully selected to address the reliability of interface-selection and the ability of the inversion to identify thin layers, large slowness contrasts, and slowness gradients. Additionally, we compare the models in terms of ground-motion amplification. These plots illustrate the sensitivity of site amplifications to the uncertainties in the slowness model. We show that one-dimensional site amplifications are insensitive to thin layers in the slowness models; although slowness is variable over short ranges of depth, this variability has little affect on ground-motion amplification at frequencies up to 5 Hz.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
On using surface-source downhole-receiver logging to determine seismic slownesses
Series title:
Soil Dynamics and Earthquake Engineering
DOI:
10.1016/j.soildyn.2007.03.005
Volume
27
Issue:
11
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Soil Dynamics and Earthquake Engineering
First page:
971
Last page:
985