Mexico City during and after the September 19, 2017 earthquake: Assessment of seismic resilience and ongoing recovery process.

Mexico City was severely affected by the September 19, 2017 Puebla-Morelos earthquake (M w = 7.1). City authorities confirmed that more than 12,000 structures for all uses were damaged as a consequence of this earthquake. In this paper, the focus of attention is devoted to trying to quantify in a simple manner how resilient the built environment in Mexico City was during the September 19, 2017 earthquake. Global statistics compiled for the severity of damage observed during this seismic event from detailed information gathered from well-documented and detailed damage surveys were used for this purpose. Also, an update is provided on how the seismic reconstruction and recovery processes of the built environment in Mexico City have been after this earthquake. This adaptive resilience has been assessed from reliable information and statistics of the ongoing reconstruction process of the affected built environment in Mexico City. The implementation of structural health monitoring programs for typical, representative buildings within the city would be germane to detect and correct potential structural deficiencies on time before the next strong earthquake may strike, then helping to improve the seismic resilience of the built environment.

Bases de datos para estimación de riesgo sísmico en la Ciudad de México. Cuadernos de Investigación / Data base for estimation of seismic risk in Mexico City. Research Notebooks

Se da a conocer información almacenada en una base de datos perteneciente al Centro Nacional de Prevención de Desastres de la Secretaría de Gobernación, que describe la problemática de los riesgos geológicos, como sismos y volcanes; los riesgos hidrometereológicos, como inundaciones, huracanes, sequías y erosión y de los riesgos químicos, tales como incendios, explosiones y contaminación por desechos industriales. En el presente documento se describe un modelo para estimar movimientos del terreno y daño a edificaciones, basado en relaciones intensidad-daño derivadas de 14 clases de edificios representativos de la construcción en la ciudad de México.

The seismic response of shallow alluvial valleys using a simplified model

A simplified model is used to approximately simulate the seismic response of three-dimensional shallow alluvial valleys. It is constructed from the exact solution for a simple configuration. Namely, the antiplane response of a rectangular deposit with a moving rigid base. In such solution, which is used as a framework for our approximations, the spectral signature of locally generater surface waves is explicit. Thus an approximate expression is constructed to separately account for 1D response and lateral effects. Results are presented for two- and three - dimensional cases. Comparisons are provided with rigorous solutions. Our formulas allow for fast computations (AU)

Resonance characteristics in the seismic response of shallow alluvial valleys

The resonance characteristics of shallow alluvial valleys during seismic excitation are studied by using several models in order to analyze the influence of interface shape, impedance contrast and anelastic attenuation. The models are studied under incidence of P, S and Rayleigh waves. We use an indirect boundary element method (BEM). Results for shallow triangular and parabolic valleys are studied in terms of frecuency-space (f-x) and frecuency-wavenumber (f-k) representations. f-x diagrams show that the valley's interface shape strongly controls the resonance patterns which appear in the response under the incident wavefield. For simple, smooth shapes such patterns are well defined. They define zones that effectively behave as barriers for certain frequencies or zones with enhanced surface wave propagation, for other frecuencies. These patterns can give large amplitudes when no damping is used (quality factor Q = ). However, for realistic values of quality factors for P and S waves, the resonance patterns show less complexity and important amplitude decrements. On the other hand, f-k diagrams allow to define dispersion curves of the surface waves present in the response. They allow to estimate the relative amount of energy that travels in each direction and provide alternative means to analize results. Preliminary analysis of spatially interpolated transfer functions for a well recorded event in Mexico City is consistent with our interpretation (AU)

Data base for seismic risk assessment in Mexico City

After the September 19, 1985 earthquake, which produced severe damage to buildings in Mexico City's lake, bed zone, many efforts have been made to better understand the nature of ground motions and the seismic behavior of structures. Results from these efforts give now the possibility to combine several sources of information to produce estimates of seismic hazard and risk that would be expected due to the occurrence of postulated earthquakes. In this paper, we describe a model to estimate: a) expected ground motions; and b) expected damage, based on intensity damage relations derived for 14 classes of buildings representative of Mexico City constructions. This information, along with the geographic distribution of construction density, allows computation of expected losses during a given event, and their spatial distribution throughout the city. Results are presented by means of a Geographic Information System (AU)

Analysis of ground motion in Mexico City during the April 25, 1989 Guerrero earthquake

In this work we analyze instrumental observations of ground motion in Mexico City durign the April 25, 1989 Guerrero earthquake. Our aim is to understand various aspects of the seismic response of the valley that are not completely resolved. Such understanding of the basic mechanisms that control the seismic behavior of the valley sediments will be crucial in any modeling attempt. The study of vertical motion for this event, which practically was not affected by site conditions, leads to identify a prominent long period (AU)