Probing environmental and tectonic changes underneath Mexico City with the urban seismic field
<p>The sediments underneath Mexico City have unique mechanical properties that give rise to strong site effects. We investigated temporal changes in the seismic velocity at strong-motion and broadband seismic stations throughout Mexico City, including sites with different geologic characterist...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-05-01
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| Series: | Solid Earth |
| Online Access: | https://se.copernicus.org/articles/14/529/2023/se-14-529-2023.pdf |
| _version_ | 1827942634162749440 |
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| author | L. A. Ermert L. A. Ermert E. Cabral-Cano E. Chaussard D. Solano-Rojas L. Quintanar D. Morales Padilla E. A. Fernández-Torres M. A. Denolle |
| author_facet | L. A. Ermert L. A. Ermert E. Cabral-Cano E. Chaussard D. Solano-Rojas L. Quintanar D. Morales Padilla E. A. Fernández-Torres M. A. Denolle |
| author_sort | L. A. Ermert |
| collection | DOAJ |
| description | <p>The sediments underneath Mexico City have unique mechanical properties that give rise to strong site effects. We investigated temporal changes in the seismic velocity at strong-motion and broadband seismic stations throughout Mexico City, including sites with different geologic characteristics ranging from city center locations situated on lacustrine clay to hillside 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 post-seismic changes, as well as a long-term linear trend in seismic velocity.
Seasonal variations can be explained by self-consistent models of thermoelastic and poroelastic 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 <span class="inline-formula"><i>M</i><sub>w</sub></span> 7.1 Puebla and 2020 <span class="inline-formula"><i>M</i><sub>w</sub></span> 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.</p> |
| first_indexed | 2024-03-13T10:01:10Z |
| format | Article |
| id | doaj.art-5ab63a72ab154592bd8c43df38b7fb85 |
| institution | Directory Open Access Journal |
| issn | 1869-9510 1869-9529 |
| language | English |
| last_indexed | 2024-03-13T10:01:10Z |
| publishDate | 2023-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Solid Earth |
| spelling | doaj.art-5ab63a72ab154592bd8c43df38b7fb852023-05-23T05:10:51ZengCopernicus PublicationsSolid Earth1869-95101869-95292023-05-011452954910.5194/se-14-529-2023Probing environmental and tectonic changes underneath Mexico City with the urban seismic fieldL. A. Ermert0L. A. Ermert1E. Cabral-Cano2E. Chaussard3D. Solano-Rojas4L. Quintanar5D. Morales Padilla6E. A. Fernández-Torres7M. A. Denolle8Department of Earth and Space Sciences, University of Washington, Seattle WA, USAnow at: Swiss Seismological Service, ETH Zürich, Zürich, SwitzerlandInstituto de Geofísica, Universidad Nacional Autónoma de México, CDMX 04510, Mexicoindependent researcherFacultad de Ingeniería, Universidad Nacional Autónoma de México, CDMX 04510, MexicoInstituto de Geofísica, Universidad Nacional Autónoma de México, CDMX 04510, MexicoFacultad de Ingeniería, Universidad Nacional Autónoma de México, CDMX 04510, MexicoInstituto de Geofísica, Universidad Nacional Autónoma de México, CDMX 04510, MexicoDepartment of Earth and Space Sciences, University of Washington, Seattle WA, USA<p>The sediments underneath Mexico City have unique mechanical properties that give rise to strong site effects. We investigated temporal changes in the seismic velocity at strong-motion and broadband seismic stations throughout Mexico City, including sites with different geologic characteristics ranging from city center locations situated on lacustrine clay to hillside 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 post-seismic changes, as well as a long-term linear trend in seismic velocity. Seasonal variations can be explained by self-consistent models of thermoelastic and poroelastic 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 <span class="inline-formula"><i>M</i><sub>w</sub></span> 7.1 Puebla and 2020 <span class="inline-formula"><i>M</i><sub>w</sub></span> 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.</p>https://se.copernicus.org/articles/14/529/2023/se-14-529-2023.pdf |
| spellingShingle | L. A. Ermert L. A. Ermert E. Cabral-Cano E. Chaussard D. Solano-Rojas L. Quintanar D. Morales Padilla E. A. Fernández-Torres M. A. Denolle Probing environmental and tectonic changes underneath Mexico City with the urban seismic field Solid Earth |
| title | Probing environmental and tectonic changes underneath Mexico City with the urban seismic field |
| title_full | Probing environmental and tectonic changes underneath Mexico City with the urban seismic field |
| title_fullStr | Probing environmental and tectonic changes underneath Mexico City with the urban seismic field |
| title_full_unstemmed | Probing environmental and tectonic changes underneath Mexico City with the urban seismic field |
| title_short | Probing environmental and tectonic changes underneath Mexico City with the urban seismic field |
| title_sort | probing environmental and tectonic changes underneath mexico city with the urban seismic field |
| url | https://se.copernicus.org/articles/14/529/2023/se-14-529-2023.pdf |
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