## 4 Conclusions  
From the results obtained in this study, it is observed that the site response in terms of the fundamental frequency \(f_{0}\) had a wide variety throughout the TMVB and there was no visible correlation between the shape of the HVSR curves and extent of any particular geological unit. In almost 46% of the stations analyzed, the response was mostly flat or it was not possible to identify clear peaks. In most of these cases, no significant impedance contrasts were observed, so they could be considered as hard rock sites. There was another small group of stations distributed in the four sectors, in which multiple peaks were observed in the HVSR curves. Some of these peaks could be identified as spurious or attributable to the influence of underlying layers of varying stiffness and thickness. Additionally, in approximately 36% of the analyzed sites there were clear peaks of varied amplitude in the HVSR curves. In these cases, it was possible to identify the value of the resonance frequency, which was mostly between 1 and 10 Hz. Similarly, in some sites there were peaks in frequencies lower than 1 Hz, which should not be underestimated considering the modern trend of tall buildings in the populated areas of the TMVB. To date, most of the seismicity studies in Mexico have focused on earthquakes originated on the Pacific Ocean coast. Except for Mexico City, due to its geotechnical properties, the amplitude of these events usually reaches the TMVB considerably attenuated. For this reason, this study focused on analyzing what happens in this zone with regional earthquakes. In this regard, it is important to note that there were sites with high peaks in the four sectors analyzed, not only in the central-eastern sector where Mexico City is located. In some stations, it was possible to make a comparison of the results obtained from ambient noise and earthquake records. In most of them, there were no significant differences in the shape of the average HVSR curves. In the analyses carried out with seismic records, no evidence of non-linear behavior was identified in the site response with respect to the ambient noise results. This could be attributed to the fact that most of the events considered are of low magnitude. In general, there are few major earthquakes with both epicenter and instrumental records inside the TMVB. However, there were some sites with a flat HVSR ambient noise curve in which new peaks appeared when analyzing earthquake data. Considering that the energy associated with ambient noise is not comparable to that associated with a seismic event, it is possible that several sites considered as hard rock may have significant amplifications during the occurrence of an earthquake. Based on these observations, we consider it is necessary to increase the density of the permanent seismic instrumentation in the TMVB. This will allow to have greater coverage, better quality records, and the possibility of carrying out more analyses using earthquake data, including the SSR technique. A greater permanent seismic instrumentation would allow obtaining isofrequency maps, which could be used in soil-structure interaction analyses and as a basis for estimating seismic hazards and risk assessment in the TMVB. This would also allow to better delimit the risk of populated zones based on local seismicity, considering the significant growth that the cities in the area have had in recent years. Conceptualization, L.F.P.-M., Q.R.-P. and F.R.Z. ; methodology, L.F.P.-M.; formal analysis, L.F.P.-M.; investigation, L.F.P.-M. and M.A.P.-L.; writing--original draft preparation, L.F.P.-M.; writing--review and editing, Q.R.-P., F.R.Z., J.H.-R. and M.d.I.L.P.-R.; supervision, J.H.-R., M.d.l.L.P.-R. and M.A.P.-L. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. The APC was funded by L.F.P.-M.  
**Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.