Browsing by Autor "Jacobo Bielak"

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Development of a first 3D crustal velocity model for the region of Bogotá, Colombia
(National University of Colombia, 2017) Andrea C. Riaño; Juan C. Reyes; Luis E. Yamín; Julián Montejo; Jose L. Bustamante; Jacobo Bielak; Nelson Pulido; Carlos Eduardo Rodríguez Molano; Alcides Huguett
Knowledge regarding the characteristics of soils in Bogotá basin has been possible to get through previous microzonation studies. However, there is still insufficient knowledge of the crustal velocity structure of the region. Bogotá is located in a region prone to a significant seismic hazard. Historically, the city has been affected by strong earthquakes, reaching moment magnitudes greater than or equal to 7. Furthermore, the city was built on a lacustrine basin, with soft soils of considerable depth that may strongly amplify the ground motion during an earthquake. In this article, we describe the development of a first crustal structure and material properties model for the region of Bogotá, Colombia, covering an area of about 130 km by 102 km. This effort aims at constructing a realistic 3D seismic velocity model using geological and geotechnical information from several sources. Major geological units have been identified and mapped into the model. The Inverse Distance Weighted (IDW) interpolation was used to create continuous surfaces delimiting the geological units. Seismic-wave properties are assigned to any point in the domain using a location-based approach. We expect this model to be useful for a wide range of applications, including dynamic ground motion simulations and fault system modeling.
Integrating 3D physics-based earthquake simulations to seismic risk assessment: The case of Bogot&#225;, Colombia.
(2023) Andrea C. Riaño; Juan C. Reyes; Jacobo Bielak; Doriam Restrepo; Ricardo Taborda; Luis E. Yamín
The basin beneath the greater metropolitan area of Bogot&#225;, Colombia, consists of soft material deposits with shear wave velocity&#160;Vs&#160;&#8804; 400 m/s that reach depths up to 425 m. Located on a high plateau in the eastern cordillera of the Colombian Andes, this highly populated urban area is subject to significant seismic hazards from local and regional fault systems.&#160;The potential ground motion amplification effects during earthquakes due to the presence of soft soil deposits and the surface and sub-surface topography constitute problems of great importance towards better understanding and estimating the seismic risk of the city. Given the scarcity of seismic data from large magnitude events, and in an effort to advance modern seismic hazard mapping for the region, this study aimed to develop a physics-based framework to generate synthetic ground records that can help to better understand the basin and other amplification effects during strong earthquake shaking in the region, and then to incorporate these effects into the estimation of seismic risk. To this end, a set of simulations were first conducted on Hercules, the wave propagation octree-based finite element simulator developed by the Quake Group at Carnegie Mellon University, to reproduce similar conditions to those observed in Bogot&#225; during past seismic events (e.g., 2008 Quetame Earthquake) and to identify the impacts of hypothetical strong earthquakes scenarios. Then the results from these simulations were then integrated into a new software package for post-processing and assessing the seismic risk in the Bogot&#225; region for different scenarios selected.