Collapsed masonry bridge outside Santiago
The Bridge Team made it back to Santiago today after covering over 1200 miles in the last 4 days. We realized that of all of the teams, we have the most ground to cover. Partly because bridges are dispersed around the entire region, and partly because many of our sites to investigate are dead-end roads precisely for the reason we are there: the bridge is out. We also realized that we are somewhat removed from the worst of the hardship of the people. While we briefly observed people dealing with hardship in Tubul and Concepcion, it must be much harder for the Tsunami Team to make observations by visiting the devastated towns north of Concepcion, or the Building Teams documenting building performance day after day in the most heavily hit urban areas.
Today, we slowly made our way up Route 5 from Linares (we never made it to Curico yesterday) to Santiago. We saw what was left of an beautiful over 200-year-old beautiful masonry bridge. Even in collapse it is a work of art. It must have survived several earthquakes and the question we ask ourselves is…why this one? We also saw several severely damaged and closed overpasses crossing Route 5 coming into Santiago. All of them rotated like the one near Ercilla (except mostly in the opposite direction), one nearly 5 feet at each abutment. As before, we saw several damaged in a row, then several identical bridges with no damage whatsoever. This pockets of damage are common in earthquakes, and are often the result of local site effects: soil conditions or topography that tend to amplify ground motions. For example, the crest of a crest or bluff, like those found over the beaches in Oregon, can amplify shaking as much as 50% or more due to focusing of seismic waves, and soft soils, like those found around bays or rivers, can amplify even small shaking by several times.
We had to drop one of our team off at the airport tonight; Luis Fargier, a consulting engineering and adjunct professor from Venezuela. Tomorrow the remainder of the team, will document performance of several bridges in and around Santiago. Along the way, a Discovery Channel crew may catch up with us. More tomorrow.
