SCEC Award Number 16054 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title High-Frequency Path and Source Parameters Determined from Recorded Ground Motion in Central California
Name Organization
Ralph Archuleta University of California, Santa Barbara Jorge Crempien University of California, Santa Barbara
Other Participants
SCEC Priorities 6c, 6d, 6e SCEC Groups CCSP, Seismology, GMP
Report Due Date 03/15/2017 Date Report Submitted 08/09/2017
Project Abstract
The main objective of this work was to determine Q for coda and direct S-waves, as well as in the coastal region between Paso Roble and San Luis Obispo. For this we determined the smoothed Fourier spectra for each ground motion recording, and used a non-parametric to invert for both path and source parameters. From the inverted source spectra, we determined , which in average was ~ 35 ms. We also determined coda Q values, where intrinsic Qi is ~315, 720, 890 and 1100 at 1-2, 2-4, 4-8, and 8-16 Hz frequency bands. Scattering Qs is ~ 1000.
Intellectual Merit We have determined important seismic parameters which are useful to quantify seismic hazard in the Central California Coastal region. To our knowledge, there have been no prior attempts to calculate regional values in this region, which are important to simulate ground motion and to estimate response spectra for engineering purposes. Also, during the term of the project, we developed a new method to estimate smooth Fourier amplitude spectra using a continuous wavelet transform.

Broader Impacts During this project, we where able to determine important seismic parameters such as Q and regional values, which will be useful for the Central California Coastal region in terms of hazard determination.
An outcome of the project was a Python code to determine Q and values, that in the future will be used to teach students on how to determine these important parameters. We plan to make this code freely available at a computer code repository.
Exemplary Figure Figure (2): (a) Ground motion produced by a Mw earthquake. The blue lines are the time window in which the continuous wavelet transform integrated along the time domain to produce a smoothed spectrum of the S-wave, (b) smoothed Spectrum of the S-wave, (c) the total attenuation (geometric, anelastic and scattering) with distance at different frequency ranges. We also show a theoretical 1/R attenuation depicted as a dashed black line, and (d) source spectra for four earthquakes of the total earthquakes we analyzed.