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Monitoring the Compaction Underneath Mexico City Using Ambient Noise

Mexico City is undergoing subsidence due to groundwater extraction that leads to compaction of the sediments composing its upper aquitard and aquifer. We study whether the influence of subsidence on the elastic properties of the near-surface, which are highly relevant for seismic hazard, can be near-continuously monitored with (urban) ambient seismic noise.

We measure relative changes in seismic velocity (dv/v) using single-station measurements of all seismic data available on the FSDN and construct time series spanning from 15 months to 25 years. We identify mainly three signals in the dv/v time series: a seasonal variation, a rapid drop and subsequent recovery coinciding with the Puebla earthquake 2017 and a long-term velocity increase that is mainly prominent at stations in and near the zone of lacustrine clay deposits that form the aquitard (“Lake zone”). We use precipitation data and the poroelastic response model of Roeloffs (1988) to calibrate the stress sensitivity of shear wave velocity. We use a co-seismic drop and relaxation model to model the Puebla 2017 earthquake signals. Finally, we extract the rate of velocity increase at each station, which we compare to the rates of subsidence determined by remote sensing methods such as InSAR. Results suggest a spatial correlation of subsidence rate and near-surface velocity increase rate.

Session: The Effects of Sedimentary Basins on Earthquake Ground Motions I

Type: Oral

Room: Cedar

Date: 4/20/2022

Presentation Time: 02:30 PM Pacific

Presenting Author: Laura A. Ermert

Student Presenter: No

Additional Authors