El presente documento es el resultado del esfuerzo colaborativo entre la Fundación GEM, el Servicio Geológico de los Estados Unidos, la Dirección Metropolitana de Gestión del Riesgo, la Oficina de la Alcaldía de Quito, la Pontificia Universidad Católica del Ecuador, y la Empresa Pública Metropolitana de Agua Potable y Saneamiento de Quito. El objetivo de este reporte es presentar los resultados de la evaluación de riesgo urbano para el Distrito Metropolitano de Quito, obtenidos dentro del contexto del Proyecto para la Comunicación y Formación en la Evaluación de Riesgos por Terremotos (TREQ), financiado por la Oficina de Ayuda Humanitaria de los Estados Unidos (BHA, por sus siglas en inglés).

Earthquake-induced landslides and liquefaction are important secondary earthquake perils that can cause substantial damage to the built environment in addition to direct damage caused by seismic ground shaking. In spite of their impacts, they are not regularly included in probabilistic seismic hazard and risk analysis (PSHRA), in part because they have not been incorporated in most PSHRA frameworks such as GEM’s OpenQuake Engine. As part of the TREQ project, existing landslide and liquefaction models were implemented within the OpenQuake Engine, and have been made available for both probabilistic and deterministic (scenario) analyses. In this study we present the methodological approach we used to implement these models using the city of Cali as the case study. Regarding coseismic landslides, found that the probability of coseismic landslides within the city limits of Cali is extremely small, although it is likely higher in the adjacent mountain regions. For liquefaction analysis, we tested the models on seismic scenarios selected by the USGS through a hazard disaggregation process. The risk metrics obtained suggest that, in the case of liquefaction, the models make an appropriate prediction of the spatial distribution of damage and loss. However,in terms of the absolute number of damaged structures, estimates for both, landslide and liquefaction risk, are inconsistent with the level of damage and loss obtained from the ground shaking. Hence, we concluded that the existing methodologies do not perform satisfactorily in urban risk applications.

The objective of a selection based on hazard is to identify events with destructive potential based on their contribution to the seismic hazard. In turn such events can be modelled to inform the risk management offices about their potential impact and support in disaster preparedness.

This seismic risk component at urban level covers the development of uniform, open and transparent datasets for the urban building inventory (exposure model), the physical response of the infrastructure under seismic loads (vulnerability model), and the assessment of the impact from earthquakes, along with risk metrics required for the development of risk reduction plans.

Reporte sobre tipologías constructivas en las ciudades del Proyecto TREQ.

We perform seismic hazard analysis for three urban centers (Cali, Colombia; Quito, Ecuador; and Santiago, Dominican Republic) within the TREQ project, explicitly accounting for the local soil response in each city. The two requirements for this analysis are (1) hazard estimates on reference bedrock at each city, for which we use the models described in D2.2.2 and D2.2.3 and (2) soil response models that quantify the amplification (or deamplification) of ground shaking throughout the three urban centers due to the shallow soil layers. In this study, in collaboration with local experts, we develop the soil response models for each city using available local geotechnical and geophysical data. We simulate the soil response using 1D equivalent linear analysis using pySRA, and a large suite of input motions generated from (and therefore fully compatible with) the underlying hazard model, which accounts for uncertainty in the input motions. The computed soil response models consist of a set of soil amplification factors (AF) and their uncertainty (�lnAF), covering the respective urban centers. The AFs are defined for periods relevant for risk analysis (PGA – 2.0 s), as well as for a wide range of bedrock shaking intensity levels (0.05 – ~4 g), and can therefore be readily used for probabilistic hazard and risk analysis. Finally, hazard curves are computed at the surface by convolving the bedrock hazard with the AFs and �lnAF at a set of sites. The results are compared to those computed using the ergodic site terms within the GMPEs, which depend on the shear wave velocity in the upper 30 m (Vs30), for which we find significant differences at some sites. Specifically, using the local soil response models can either increase (up to a factor ~2) or decrease the hazard results compared to when an inferred Vs30 is used. For soft sites at longer return periods, the hazard can be lower (and sometimes lower than the hazard on rock) due to soil nonlinearity. These differences can have a significant impact on the risk results, which are described in Deliverable D2.3.5. This study demonstrates the importance of incorporating local soil response when the goal is to model hazard at the urban scale with a higher level of detail compared to more standard approaches using Vs30.

Description of the hazard results on rock and soil for the three cities in the urban hazard assessment component of TREQ.

Description of the probabilistic seismic hazard model developed for the Dominican Republic

The Training and Communication for Earthquake Risk Assessment (TREQ) Project was designed to demonstrate how earthquake hazard and risk assessment can inform decision makers in the development of risk reduction policies, as well as how earthquake risk can be properly communicated to stakeholders and the public in general. The project was organized into two main parts. The first one aimed to develop capacity for urban earthquake hazard and risk assessment in Latin America, Quito (Ecuador), Cali (Colombia), and Santiago de los Caballeros (Dominican Republic); while the second part was to develop training, educational and communication material to enhance the understanding of earthquake risk worldwide. The program was tailored for a wide spectrum of stakeholders, categorized into four main groups: governance (decision-makers/public authorities), industry (practitioners and professionals), academia (researchers and professors), and the community.

Descripción del modelo probabilístico de amenaza sísmica desarrollado para La República Dominicana