Carnegie Mellon University
April 28, 2014

Collaboration with Colombian University Leads to First Velocity Model of Aburrá Valley

Collaboration with Colombian University Leads to First Velocity Model of Aburrá Valley

Vertical component of the velocity wave field at t=7.5s due to a Mw=4.0 point-source earthquake along the Romeral fault. The yellow start represents the earthquake epicenter. Results were obtained using the Initial Velocity Model of the Aburra Valley region developed in partnership by the Quake Group at CMU and the Applied Mechanics Group at Universidad EAFIT.Vertical component of the velocity wave field at t=7.5s due to a Mw=4.0 point-source earthquake along the Romeral fault. The yellow start represents the earthquake epicenter. Results were obtained using the Initial Velocity Model of the Aburra Valley region developed in partnership by the Quake Group at CMU and the Applied Mechanics Group at Universidad EAFIT.

Paul Christiano University Professor Jacobo Bielak, a renowned researcher in engineering seismology and earthquake engineering, believes strongly in the benefits of cross-cultural collaboration and is involved in a number of international projects related to earthquake simulation. Several years ago, Bielak and Jim Garrett, then-CEE department head, initiated an agreement between the Carnegie Mellon University Civil & Environmental Engineering Department and Colombia’s EAFIT University to promote joint educational and research initiatives that would benefit both institutions. The agreement, which was signed during a visit to EAFIT by Bielak and Garrett in 2010, established a dual PhD program between EAFIT and CMU. 

The first EAFIT student to participate in the program, Doriam Restrepo, received joint funding from EAFIT, the Fulbright Program, the CEE Department, and Colombia’s CNSC (Comisión Nacional del Servicio Civil) to develop a model of the Aburrá Valley, the hilly, highly seismic region where EAFIT is located. “Researchers in Colombia wanted to be able to conduct earthquake simulations of the Valley, like the ones we are conducting in California,” Bielak explained. “But to do that, you need a model of the region’s geological properties, and that didn’t exist. So Dorian, working with geologists in EAFIT, created a large model of this region. It was a project that was of interest to us in CEE, but also one that will benefit Colombia.” 

In creating the model, Restrepo and Bielak developed a new method that more accurately represents hills and mountains in a landscape. Previously, sloped sections of the land were modeled in Hercules, the wave propagation finite element code developed by the Quake group at CMU, using small cubes as units. This resulted in an artificial, jagged edge, much like a staircase, which introduced errors in the model. The challenge was to find a way to better define the contours of the surface. “This involved ‘cheating’ the existing methodology, which only understands cubes, to create arbitrary shapes while preserving the structure of the code – not an easy task,” Bielak explained. After developing the methodology, they then applied it to the Aburrá Valley model. 

“With the help of local researchers, Doriam has constructed the first model ever created of a seismic region in Colombia,” Bielak said. “We have already conducted some initial tests in which we simulate an earthquake in a particular area and explore how the waves travel. It is quite an accomplishment.”

Restrepo completed his PhD studies in October 2013 and is now an assistant professor in EAFIT. He is in the process of publishing several papers that detail the modeling methodology that he developed and discusses potential applications of his approach. Other students are expected to take part in the joint program in the future, and Bielak hopes to see the program expand to include additional departments within Carnegie Mellon.

“The advantages of international projects like the CEE-EAFIT agreement are numerous,” said Bielak. “In the case of EAFIT, they sent a student here, he has been trained, and he is now returning as a representative of CMU and will have an influence there,” he explained. “And at the same time, we in CEE were able to contribute to knowledge. That type of win-win situation is when these collaborations work.” Bielak also noted that international exchanges benefit CEE students academically and personally. “I see that when our students have the opportunity to live abroad – even for as little as a month – it not only expands their understanding of engineering; it also gives them a better understanding of the U.S. and of the world.”