Seismic vulnerability in Latinamerica Speaker: Rafael Osiris de León Sciences Academy of Dominican Republic.

Seismic vulnerability in Latinamerica Speaker: Rafael Osiris de León Sciences Academy of Dominican Republic. IANAS GENERAL ASSEMBLY Punta Cana, 16-20 July, 2013

TECTONIC PLATES AND EARTHQUAKES

Pacific fire belt produces 80% of total eartquakes

Main regional faults in the Hispaniola Island

Main damages zone of the 2010 Haití earthquake

The 2010 Haiti earthquake On January 12 th, 2010, a 7.0 magnitude earthquake with an epicenter 15 km SW of the city of Port-au-Prince and a hypocenter at 10 km depth, produced 316,000 deaths, 350,000 wounded, and destroyed 300,000 homes that left 1,500,000 homeless. This is the worst global seismic tragedy of the past 50 years.

Haiti national palace, raised on soft clay, and destroyed by the 2010 earthquake.

Vs profile at North side of National Palace of Haití, showing soft soils at surface that should be remove for the construction of the new Palace.

Haiti Cathedral, raised on soft clay, and destroyed by the 2010 earthquake.

Typical clay of the Port au Prince valley

The famous hotel Montana raised on different materials with different seismic answers.

Small village, raised on soft clay, and destroyed by the 2010 earthquake.

Salessian School, raised on soft clay with 3 upper soft stories destroyed by the 2010 Haití earthquake.

Building raised on soft clay with first floor in columns, without shear wall. The soft floor collapsed.

Bank raised on soft clay with first floor in columns, without shear wall. The soft floor collapsed.

Typical structure collapsed in 2010 Haiti EQ.

University of Leogane, with three floors collapsed

Leogane school raised on soft clay and supported by columns failed by shear strenght..

Vs profile at harbor East side, in Port au Prince, Haití, showing soft soils between 2.0 and 4.5 m deep with a Vs of 75 m/sec. The best choice is to remove this bad material prior to start with the building foundations.

Vs profile at harbor East side, in Port au Prince, Haití, showing soft soils between 2.0 and 4.5 m deep with a Vs of 75 m/sec. Relating this low shear strength, we would expect a site amplification of the EQ effects.

Structures on rock without damages In the southern mountainous area of Petionville, buildings did not suffer any damage, although many buildings were erected without any engineering criteria, and although they were located in or near the epicenter area, but as they were raised on hard limestone bedrock, all the bad structures were ok, as a rock site protection effect.

Very hard limestone rock of south hills of Port au Prince. Site protection effect.

Poorly built structures erected without any engineering critera, without any type of damage, not even cracks, after the earthquake.

Poorly built structure, with a second soft floor, erected without any engineering critera, without any type of damage after the earthquake

A dense village compound, on the hard limestone rock of south hills of city. Note the lack of damage.

The rich villages of PetionVille, without any type of damage, not even cracks, after the earthquake.

The 2010 Chilean earthquake On February 27, 2010, 45 days after the Haity earthquake, Chile was shaked by on of the mayor earthquakes of the world, with magnitude of 8.8, causing 452 deaths, mainly in the coastal line where the sea water became as tsunami.

Alto Río building Collapsed during Chile earthquake of 2010.

2010 Chile earthquake

1960 Chile earthquake In 1960 Chile was shaked by the biggest earthquake registered, with a magnitud of 9.5, producing a tsunami that killed 61 peoples in Hawai and 200 peoples in Japan.

1939 Chile earthquake On January 24, 1939, the city of Chillán, Chile, was shaked by a very strong earthquake, with 30,000 deaths.

1944 Argentina earthquake On january 22 of 1944, the city of San Juan, Argentina, was shaked by one earthquake, with a balance of 10,000 deaths.

El terremoto de Perú One of the biggest earthquake in Latinamerican countries was on May 31, 1970, in Peru, with 75,000 deaths.

The 1972 Managua earthquake On december 23, 1972, Managua city, in Nicaragua, was shaked by a strong earthquake, killing 20,000 peoples.

The 1976 Guatemala earthquake On February 4, 1976, Guatemala city was shaked by an earthquake, with 23,000 deaths.

The 1985 México earthquake On September 19, 1985, Mexico city was shaked by an earthquake with epicenter in the Pacific coast, 320 Km away, killing near 45,000 deaths in the building raised over the flexibles soils of the ancient Texcoco lake.

The 1985 México earthquake

CONCLUSIONS The 2010 earthquake of Port-au-Prince, located on the southwestern area of the Hispaniola island, was the most devastating earthquake in the island s history, and this disaster was particularly extensive as the epicenter was close to a dense and poor urban area raised over low-shear strength clay and sand soils. Propagation velocities of shear seismic waves (Vs) on the east side of the Port au Prince harbor, shows that a horizon from 1.3 m to 4.5 meters deep has a shear-wave velocity (Vs) of approximately 75 meters per second. This material has low shear-strength, and therefore, would cause amplification of strong ground motion.

CONCLUSIONS In the southern mountainous area of Pétionville, where limestone bedrock is present at the surface, the buildings did not suffer any type of damage, not even cracks, in the poorly built structures erected without any engineering forethought. Soil characteristics should relate to building criteria designed to combat amplification, etc. For example, isolated columns in use on top of soft soils, must be increased in diameter to handle greater shear deformation. This applies to all buildings, but particularly to the construction of schools, hospitals, towers, malls, and service and strategic institutions.

CONCLUSIONS Future engineering seismic design must be in accordance with shearwave velocity measurements made at building site to avoid or reduce disasters, as seen in Haiti, Mexico, and other Latinamerican countries. Thank you for your attention.