Probing environmental and tectonic changes underneath Mexico City with the urban seismic field
Por:
Ermert, Laura A., Cabral-Cano, Enrique, Chaussard, Estelle, Solano-Rojas, Dario, Quintanar, Luis, Morales Padilla D., Fernandez-Torres, Enrique A., Denolle, Marine A.
Publicada:
23 may 2023
Resumen:
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 M-w 7.1 Puebla and 2020 M-w 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.
Filiaciones:
Ermert, Laura A.:
Department of Earth and Space Sciences, University of Washington, Seattle, WA, United States
Swiss Seismological Service, ETH Zürich, Zürich, Switzerland
Univ Washington, Dept Earth & Space Sci, Seattle, WA USA
Cabral-Cano, Enrique:
Instituto de Geofísica, Universidad Nacional Autónoma de México, CDMX, 04510, Mexico
Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City 04510, Mexico
Chaussard, Estelle:
independent researcher
Solano-Rojas, Dario:
Facultad de Ingeniería, Universidad Nacional Autónoma de México, CDMX, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Ingn, Mexico City 04510, Mexico
Quintanar, Luis:
Instituto de Geofísica, Universidad Nacional Autónoma de México, CDMX, 04510, Mexico
Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City 04510, Mexico
Morales Padilla D.:
Facultad de Ingeniería, Universidad Nacional Autónoma de México, CDMX, 04510, Mexico
Fernandez-Torres, Enrique A.:
Instituto de Geofísica, Universidad Nacional Autónoma de México, CDMX, 04510, Mexico
Univ Nacl Autonoma Mexico, Inst Geofis, Mexico City 04510, Mexico
Denolle, Marine A.:
Department of Earth and Space Sciences, University of Washington, Seattle, WA, United States
Univ Washington, Dept Earth & Space Sci, Seattle, WA USA
gold, Gold
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