SCEC Award Number 14236 View PDF
Proposal Category Individual Proposal (Integration and Theory)
Proposal Title Basin Amplification Variability for the Kanto Basin from Ambient-Seismic-Field Observations
Investigator(s)
Name Organization
Gregory Beroza Stanford University
Other Participants Pierre Boue, Marine Denolle, Naoshi Hirata, Hiroe Miyake, Shigeki Nakagawa
SCEC Priorities 6d, 6e, 6a SCEC Groups GMP, Seismology, GMSV
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
 We continued work on using ambient seismic field data to explore amplification in urban Tokyo. We used a combination of 375 Hi-Net deep borehole seismometers across central Honshu as virtual sources and 296 seismic stations of the MeSO-Net work shallow-borehole seismometers within the basin as receivers to map the basin impulse response (Denolle et al., 2014). We found a linear relationship between vertical ground motion and basin depth at periods of 2 – 10 seconds that could be used to represent 3D basin effects in ground motion prediction equations. We also found that the strength
 of basin amplification depends strongly on the direction of illumination by seismic waves. This is consistent with observations of Niigata-area earthquakes that show strong amplification vs. Fukushima-area earthquakes that do not. Under this grant we are developing a new approach to developing ambient-field Green’s functions for which the bias due to uneven distribution of noise sources is sharply reduced.
Intellectual Merit This project grew out of an effort to validate ground motion simulations in SCEC special projects. It represents fundamentally new approach to strong ground motion prediction, and as such is well aligned with SCEC goals and objectives.
Broader Impacts The broader impacts of this research to validate ground motion simulations so that they will be used by earthquake engineers. Our work under this grant has inspired people in other countries - France, Mexico, Switzerland, Korea, Japan, Italy, New Zealand, Nepal, and likely elsewhere, to apply the method to their earthquake problems. We are currently in discussion to apply it on a smaller scale to the important emerging hazard of ground motion from induced seismicity. A YouTube video (http://www.youtube.com/watch?v=WTg3GzGCRfA) that was released when the LA Basin paper was published has received over 61,500 hits as of May 2, 2015.
Exemplary Figure Figure 4. Results for the Long Beach nodal seismic array. Top panel shows the empirically derived virtual source contributions from the stations within the array for a single station pair. The upper gray panel shows the contributions with time into the seismogram, and the resulting stack (red). Lower two panels show the same quantities, but for the theoretically ideal case as sampled by the stations of the array. Note the close resemblance between the hyperbolae of top and bottom panels. Under this grant we are developing similar images for the Kanot Basin using the MesoNet array.