SCEC Project Details
SCEC Award Number  16054  View PDF  
Proposal Category  Collaborative Proposal (Integration and Theory)  
Proposal Title  HighFrequency Path and Source Parameters Determined from Recorded Ground Motion in Central California  
Investigator(s) 


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 Swaves, 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 nonparametric 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 12, 24, 48, and 816 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 Swave, (b) smoothed Spectrum of the Swave, (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. 