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Preprints
https://doi.org/10.5194/egusphere-2022-1361
https://doi.org/10.5194/egusphere-2022-1361
10 Jan 2023
 | 10 Jan 2023

Probing environmental and tectonic changes underneath Ciudad de México with the urban seismic field

Laura Ermert, Enrique Cabral-Cano, Estelle Chaussard, Dario Solano-Rojas, Luis Quintanar, Diana Morales Padilla, Enrique A. Fernandez-Torres, and Marine A. Denolle

Abstract. The subsurface materials of Ciudad de México have unique mechanical properties that give rise to strong site effects. We investigated temporal changes in the seismic velocity at strong-motion and broad-band seismic stations throughout Mexico City, including sites with different geologic characteristics ranging from city center locations situated on lacustrine clay to hillsite locations on volcanic bedrock. We used autocorrelations of urban seismic noise, enhanced by waveform clustering, to extract subtle seismic velocity changes by coda wave interferometry. We observed and modeled seasonal, co-, and postseismic changes, as well as a long-term linear trend in seismic velocity. Seasonal variations can be explained by self-consistent models of thermo-elastic and poro-elastic changes in the subsurface shear wave velocity. Overall, sites on lacustrine clay-rich sediments appear to be more sensitive to seasonal surface temperature changes, whereas sites on alluvial and volcaniclastic sediments and on bedrock are sensitive to precipitation. The 2017 Mw 7.1 Puebla and 2020 Mw 7.4 Oaxaca earthquakes both caused a clear drop in seismic velocity followed by a time-logarithmic recovery that may still be ongoing for the 2017 event at several sites, or that may remain incomplete. The slope of the linear trend in seismic velocity is correlated with the downward vertical displacement of the ground measured by Interferometric Synthetic Aperture Radar, suggesting a causative relationship and supporting earlier studies on changes in the resonance frequency of sites in the Mexico City basin due to groundwater extraction. Our findings show how sensitively shallow seismic velocity, and in consequence, site effects, react to environmental, tectonic and anthropogenic processes. They also demonstrate that urban strong-motion stations provide useful data for coda-wave monitoring given sufficiently high-amplitude urban seismic noise.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
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Journal article(s) based on this preprint

23 May 2023
Probing environmental and tectonic changes underneath Mexico City with the urban seismic field
Laura A. Ermert, Enrique Cabral-Cano, Estelle Chaussard, Darío Solano-Rojas, Luis Quintanar, Diana Morales Padilla, Enrique A. Fernández-Torres, and Marine A. Denolle
Solid Earth, 14, 529–549, https://doi.org/10.5194/se-14-529-2023,https://doi.org/10.5194/se-14-529-2023, 2023
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

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Ciudad de México is built on a unique soil containing the clay-rich deposits of ancient lake...
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