Monitoring the changing site response of the Mexico City basin

Laura A. Ermert, & Marine A. Denolle

Published August 14, 2020, SCEC Contribution #10594, 2020 SCEC Annual Meeting Poster #083 (PDF)

Many large cities are built on sedimentary basins, and considerable effort has been dedicated to study the specific seismic hazard associated with their particular geometries and lithologies. Recently, there is growing recognition of the evolving nature of basin seismic response and its sensitivity to environmental changes.

Here, we study the Mexico city basin. Its fundamental resonance period has shifted in response to groundwater extraction and related subsidence during past decades (Arroyo et al., 2013). The aim of our study is to develop continuous monitoring methods for the seismic velocity, and ultimately also attenuation and resonance frequency, of the basin.

To measure velocity changes, we rely on urban noise correlations. We utilize continuous seismic recordings from temporary and permanent broadband seismic stations, as well as a continuously recording accelerometer, to create a baseline of observed changes in seismic properties.
Due to the variability and inhomogeneous spatial distribution of the urban seismic noise sources, we extract repetitive signals in the correlations using clustering. Measurements allows us to observe both seasonal and long-term trends in ground response.
Based on the results from continuous data, we further evaluate the possibility of using auto-correlations of regional earthquakes recorded on triggered accelerometers for supplementing the monitoring of seismic properties.

Recent unconventional instrumentation, such as RaspberryShake citizen science stations and low-cost MEMS accelerometers, may hold additional potential for monitoring the evolution of seismic response and site effects. We explore the usage of both types of sensors through the evaluation of urban noise and regional earthquakes. If successful, such sensors could greatly improve the spatial density of the observation of basin response and seismic hazard characteristics.

Key Words
ambient noise, site effects

Citation
Ermert, L. A., & Denolle, M. A. (2020, 08). Monitoring the changing site response of the Mexico City basin. Poster Presentation at 2020 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology