Ground Motion in Mexico City During the Intraslab Earthquake of 19 September 2017 (Mw 7.1) Revisited
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Abstract
The intraslab earthquake of 2017 (Mw7.1) was one of the most destructive earthquakes in the history of Mexico City. Several measures of the ground motion reveal that the 2017 event was unusually energetic at CU, the reference hillzone site in the city, and, hence, in the entire Valley of Mexico, in the critical frequency range of 0.4 to 1 Hz, e.g., Fourier acceleration spectrum (FAS), peak ground velocity (PGV), and pseudoacceleration response spectrum (Sa), 5% damping, at structural periods of 1 ≤ T ≤ 1.8 s (0.55 ≤ f ≤ 1 Hz). However, the cause of the large ground motion at CU remains unresolved. The issue merits a careful analysis of all available data. On 7 December 2023, an intraslab Mw 5.8 earthquake occurred in proximity to the 2017 event. We analyze the recordings of the 2017 earthquake separately and of the 2017 and 2023 events together in an attempt to isolate the cause of the anomalous high-frequency radiation. In this context, we take recourse of the 2023 recordings as empirical Green’s functions (EGFs). Synthesized Sa for a Mw7.1 earthquake, using 2023 (Mw 5.8) recordings as EGFs and assuming the same stress drop, Δσ, of 3 MPa for both events, are significantly lower than those observed, irrespective of the azimuth. We find that the source was unusually energetic at all azimuths, and the role of rupture directivity in enhancing the ground motion was relatively small. The possibility that the enhanced ground motion in the city in 2017 was due to a particular direction of the incident wavefield on the 3-D structure of the Valley of Mexico may be ruled out since the recordings of the 2023 event, which was nearly collocated with the 2017 earthquake, show nothing anomalous. The simulated Sa using recordings of the 2023 event as EGFs suggest that a postulated intraslab Mw 7.1 earthquake, with source characteristics similar to the 2023 event, at a distance of ~ 130 km from CU, should cause little or no damage in the city. In other words, if the source of the 2017 earthquake had been a scaled-up version of the 2023 event then, quite likely, Mexico City would have been spared the damage and deaths that it suffered.
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References
Anderson, J. G., Bodin, P., Brune, J. N., Prince, J., Singh, S. K., Quass, R. & Oñate, M. (1986). Strong ground motion from the Michoacan, Mexico earthquake. Science, 233(4768), 1043–1049. doi: https://doi.org/10.1126/science.233.4768.1043
Arroyo, D., Ordaz, M. & Singh, S. K. (2024). Prediction of Fourier amplitude spectrum of ground motion in Mexico City from subduction thrust earthquakes. Geofísica Internacional, 63(2), 783–801. doi: https://doi.org/10.22201/igeof.2954436xe.2024.63.1.1717
Arroyo, D., Singh, S. K., Ordaz, M., Meli, R. & Ramírez, M. (2020). Observed seismic intensities and damage pattern in central Mexico during intraslab earthquakes of 1999 (Mw 6.9) and 2017 (Mw 7.1). Geofísica Internacional, 59(2), 82-100. doi: https://doi.org/10.22201/igeof.00167169p.2020.59.2.2082
Boatwright, J. & Choy G. L. (1986). Teleseismic estimates of the energy radiated by shallow earthquakes. Journal of Geophysical Research, 91(B2), 2095–2112. doi: https://doi.org/10.1029/JB091iB02p02095
Boore, D. M. (2003). Simulation of ground motion using the stochastic method. Pure and Applied Geophysics, 160, 635–676. doi: https://doi.org/10.1007/PL00012553
Brune, J. N. (1970). Tectonic stress and the spectra of seismic shear waves from earthquakes. Journal of Geophysical Research, 75(26), 4997-5009. doi: https://doi.org/10.1029/JB075i026p04997
Ferrari, L., Orozco-Esquivel, T., Manea, V. & Manea, M. (2012). The dynamic history of the Trans-Mexican Volcanic Belt and the Mexico subduction zone. Tectonophysics, 522, 122-149. doi: https://doi.org/10.1016/j.tecto.2011.09.018
García, D., Singh, S. K., Herráiz, M. & Pacheco, J. F. (2005). Inslab earthquakes of central Mexico: peak ground-motion parameters and response spectra. Bulletin of the Seismological Society of America, 95(6), 2272–2282. doi: https://doi.org/10.1785/0120050072
García, D., Singh, S. K., Herráiz, M., Pacheco, J. F. & Ordaz, M. (2004). Inslab earthquakes of central Mexico: Q, source spectra and stress drop. Bulletin of the Seismological Society of America, 94, 789–802. doi: https://doi.org/10.1785/0120030125
Herrmann, R. B. (1985). An extension of random vibration theory estimates of strong ground motion to large distances. Bulletin of the Seismological Society of America, 75, 1447-1453. doi: https://doi.org/10.1785/BSSA0750051447
Iglesias, A., Singh, S. K., Pacheco, J. F. & Ordaz, M. (2002). A source and wave propagation study of the Copalillo, Mexico earthquake of 21 July, 2000 (Mw = 5.9): Implications for seismic hazard in Mexico City from inslab earthquakes. Bulletin of the Seismological Society of America, 92(3), 1060–1071. doi: https://doi.org/10.1785/0120010144
Jaimes, M. A., Ramirez-Gaytán, A. & Reinoso, E. (2015). Ground-motion prediction model from intermediate-depth intraslab earthquakes at the hill and lake-bed zones of Mexico City. Journal of Earthquake Engineering, 19(8), 1260-1278. doi: https://doi.org/10.1080/13632469.2015.1025926
Melgar, D., Pérez-Campos, X., Ramirez-Guzman, L. Spica, Z., Espíndola, V. H., Hammond, W. C. & Cabral-Cano, E. (2018). Bend faulting at the edge of a flat slab: the 2017 Mw7. 1 Puebla-Morelos, Mexico earthquake. Geophysical Research Letters, 46(6), 2633-2641. doi: https://doi.org/10.1002/2017GL076895
Mirwald, A., Cruz-Atienza, V. M., Díaz-Mojica, J., Iglesias, A., Singh, S. K., Villafuerte, C. & Tago, J. (2019). The 19 September 2017 (Mw7.1) intermediate-depth Mexican earthquake: A slow and energetically inefficient deadly shock. Geophysical Research Letters, 46. doi: https://doi.org/10.1029/2018GL080904
Ordaz, M. & Singh, S. K. (1992). Source spectra and spectral attenuation of seismic waves from Mexican earthquakes, and evidence of amplification in the hill zone of Mexico City. Bulletin of the Seismological Society of America, 82, 24–43. doi: https://doi.org/10.1785/BSSA0820010024
Ordaz, M., Arboleda, J. & Singh, S. K. (1995). A scheme of random summation of an empirical Green’s function to estimate ground motions from future large earthquakes. Bulletin of the Seismological Society of America, 85, 1635-1647. doi: https://doi.org/10.1785/BSSA0850061635
Ordaz, M., Arroyo, D., Singh, S. K. & Salgado-Gálvez, M. A. (2024). A PSHA for Mexico City based solely in Fourier-based GMM of the response spectra. Soil Dynamics and Earthquake Engineering, 187, 109025. doi: https://doi.org/10.1016/j.soildyn.2024.109025
Ordaz, M., Reinoso, E., Jaimes, M. A., Alcántara, L. & Pérez, C. (2017). High-resolution early earthquake damage assessment system for Mexico City based on a single-station. Geofísica Internacional, 56, 117-135. doi: https://doi.org/10.22201/igeof.00167169p.2017.56.1.1751
Ordaz, M., Singh, S. K. & Arciniega, A. (1994). Bayesian attenuation regressions and application to Mexico City. Geophysics Journal International, 117, 335–344. doi: https://doi.org/10.1111/j.1365-246X.1994.tb03936.x
Ordaz, M., Singh, S. K., Reinoso, E., Lermo, J., Espinosa, J. M. & Domínguez, T. (1988). Estimation of response spectra in the lake bed zone of the valley of Mexico during the Michoacan earthquake. Earthquake Spectra, 4(4), 815–834. doi: https://doi.org/10.1193/1.1585504
Ovando Shelley, E. (2011). Some technical properties to characterize Mexico City clay, Proc. 14-the Panamerican conference on soil mechanics and geotechnical engineering. Canadian Geotechnical Society, Paper 889.
Pacheco, J. F. & Singh, S. K. (1995). Estimation of ground motion in the Valley of Mexico from normal-faulting, intermediate-depth earthquakes in the subducted Cocos plate. Earthquake Spectra, 11(2), 233–247. doi: https://doi.org/10.1193/1.1585813
Pérez-Campos, X. & Beroza, G. C. (2001). An apparent mechanism dependence of radiated seismic energy. Journal of Geophysical Research, 106(B6), 11,11127–11136. doi: https://doi.org/10.1029/2000JB900455
Pérez-Campos, X., Singh, S. K. & Beroza, G. C. (2003). Reconciling teleseismic and regional estimates of seismic energy. Bulletin of the Seismological Society of America, 93, 2123–2130. doi: https://doi.org/10.1785/0120020212
Reinoso, E. & Ordaz, M. (1999). Spectral ratios for Mexico City from free-field recordings. Earthquake Spectra, 15, 273–296. doi: https://doi.org/10.1193/1.1586041
Reinoso, E. & Ordaz, M. (2001). Duration of strong ground motion during Mexican earthquakes in terms of magnitude, distance to the rupture area and dominant site period. Earthquake Engineering Structural Dynamics, 30(5), 653-673. doi: https://doi.org/10.1002/eqe.28
Singh, S. K., Lermo, J., Domínguez, T., Ordaz, M., Espinosa, J. M., Mena, E. & Quaas, R. (1988a). The Mexico Earthquake of September 19, 1985—A study of relative amplification of seismic waves in the valley of Mexico with respect to a hill zone site (CU). Earthquake Spectra, 4(4), 653–674. doi: https://doi.org/10.1193/1.1585496
Singh, S. K., Mena, E. & Castro, R. (1988b). Some aspects of source characteristics of 19 September 1985 Michoacan earthquake and ground motion amplification in and near Mexico City from the strong motion data. Bulletin of the Seismological Society of America, 78(2), 451–477. doi: https://doi.org/10.1785/BSSA0780020451
Singh, S. K., Ordaz, M., Pérez-Campos, X. & Iglesias, A. (2015). Intraslab versus interplate earthquakes as recorded in Mexico City: Implications for seismic hazard. Earthquake Spectra. doi: https://doi.org/10.1193/110612EQS324M.
Singh, S. K., Pérez-Campos, X., Espíndola, V. H., Cruz-Atienza, V. M. & Iglesias, A. (2014). Intraslab earthquake of 16 June 2013 (Mw 5.9), one of the closest such events to Mexico City. Seismological Research Letters, 85, 268-277. doi: https://doi.org/10.1785/0220130179
Singh, S. K., Pérez-Campos, X., Espindola, V. H., Iglesias, A. & Quintanar, L. (2020) An intraslab earthquake at a depth of 100 km in the subducting Cocos plate beneath Nevado de Toluca volcano. Geofísica Internacional, 59(1), 5-12. doi: https://doi.org/10.22201/igeof.00167169p.2020.59.1.2072
Singh, S. K., Reinoso, E., Arroyo, D., Ordaz, M., Cruz‐Atienza, V. M. & Pérez‐Campos, X. (2018). Deadly intraslab Mexico earthquake of 19 September 2017 (Mw 7.1): Ground motion and damage pattern in Mexico City. Seismological Research Letters, 89, 2193–2203. doi: https://doi.org/10.22201/igeof.00167169p.2020.59.1.2072
Wessel, P. & Smith, W. H. (1995). New version of the generic mapping tools. Eos, Transactions American Geophysical Union, 76(33), 329-329. doi: https://doi.org/10.1029/95EO00198