Array Analysis of Body-Wave Polarization Data: Application to Mexico City Seismic Networks
Abstract
Mexico City is a densely populated area located largely on top of a shallow layer of sediments known as the lake-bed zone. The associated site effects together with the recurrent seismic activities of the region stress the importance of studying the subsurface structure of Mexico City. In order to better characterize the near-surface structure, we present a novel approach utilizing the body-wave polarization data which were demonstrated to be effective in estimating shallow (~100 m) structure in an inexpensive and non-invasive way (Park and Ishii, 2018). While the previous method analyzes individual stations separately, we develop a technique that can take advantage of seismic array data from a series of events. Our array analysis provides robust estimates of ray parameters, allowing one to utilize regional and local earthquake data even when raypaths traverse complicated structures. Moreover, the new formulation only requires ray parameter estimates for a single event. This makes the technique further applicable to data without accurate instrument timing, which are often excluded by conventional traveltime-based analyses.
We applied our technique to the Mexico City network CIRES, using body-wave polarization data from a set of intraslab earthquakes with epicentral distances of 100 to 300 kilometers. The estimated shear wave speed values were found consistent with geotechnical models both at soft-soil and hard-rock sites. The compressional wave speed estimates at soft-soil sites provide new insight into the seismic structure of the lake-bed zone, given that the compressional wave speed structure of the area had not been thoroughly studied before. Therefore, the results of our study will further contribute to improvement of the local seismic codes and mitigation of future damage. Park, S., & Ishii, M. (2018). Near-surface compressional and shear wave speeds constrained by body-wave polarization analysis. Geophysical Journal International, 213, 1559-1571, doi:10.1093/gji/ggy072.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMNS009..02R
- Keywords:
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- 1835 Hydrogeophysics;
- HYDROLOGY;
- 4315 Monitoring;
- forecasting;
- prediction;
- NATURAL HAZARDS;
- 4341 Early warning systems;
- NATURAL HAZARDS