Over the past year, TREQ has made significant progress in the risk and hazard assessments for the selected cities – Santiago, Quito and Cali. This includes the completion of the compilation and preparation of existing PSHA models for hazard calculations; and the development of detailed exposure and vulnerability models.
Urban Hazard Assessment
For Cali, Colombia, the project improved the national model proposed by Arcila et al. (2020) by adding a new fault located over the city (i.e. Cauca-Cali-Patia fault), consistent with the seismic zonations used in the microzonation study for Santiago de Cali (Ingeominas-Dagma, 2005), and the Colombian building code (AIS, 2009).
For Quito, Ecuador, the project selected the model of Beauval et al. (2018), composed of shallow and subduction seismic sources characterized using an ISC-based catalogue and active shallow fault sources considering geodetic slip-rates assuming a 50% of aseismic slip.
In the second half of 2020, the project worked on collecting and consolidating the available geological, geophysical, and geotechnical data for each of the three cities needed to compute site-response (response of the local soil during seismic shaking).
When available, the data collected includes the following measurements for each soil layer: shear wave velocity, layer thickness, unit weight, effective pressure, plasticity index, over consolidation ratio, and non-linear material properties. These properties enable the project to perform dynamic analysis of the soil considering non-linear behavior. If some of this data is incomplete or unavailable, the project estimates the parameters using equations derived from literature where possible.
Urban Risk Assessment
GEM has already developed exposure datasets at the subnational level in Colombia, the Dominican Republic and Ecuador, however the risk assessment activities planned within the context of TREQ require exposure datasets at the urban scale for the three cities. In order to achieve this, the project focused its activities on the development of an exposure model at a district level using the available datasets in collaboration with the local partners.
For the Metropolitan District of Quito (DMQ), a total of 29 datasets were used to determine the occupants, structures and replacement costs of the residential, commercial and industrial building stocks. The project used datasets mainly from the official census of population and households (projected to 2020), the city cadastral database (2020), the land use dataset (2016) and the historical development of the city squares from 1760 to 2015.
Currently the model has over 1.8 million occupants and 500,000 structures worth 8 billion USD. The structures have been classified by their construction material, lateral load-resisting system, height, approximate age, use and occupancy type.
For Cali, Colombia, a detailed exposure model is under development in collaboration with the local partners. The working group include students and professors from EAFIT University, the city planning department (DAPM, Departamento Administrativo de Planeación Municipal), the Risk Emergency Secretariat of Cali (Secretaría de Gestión del Riesgo), and the Colombian Geological Survey (CGS).
For the city of Santiago de los Caballeros, the exposure model has been developed in collaboration with the office of territorial planning (POT, Plan de Ordenamiento Territorial). More than 10 different datasets are being used to characterize the urban environment. The baseline dataset is the land use of the city, featuring the current use of the land at a city square level. The project focused on identifying the physical characteristics of the structures in each square using other information owned by the POT, including the construction material, building height and age of homogeneous zones of the city.
The Covid-19 pandemic has strongly impacted the activities planned for the TREQ project. At GEM we are committed to transform and adjust the project activities in order to provide the best result and overcome the difficulties imposed by the global pandemic. Despite the challenges, TREQ local partners remain committed to continue with the project activities in their respective countries and to continue with the collaboration, once the transition period is completed.