1994 Bolivia earthquake

Earthquake
title=1994 Bolivia earthquake
date= June 9, 1994


caption =
magnitude = 8.2 M_w [http://www.cambridge.org/us/catalogue/catalogue.asp?isbn=9780521828697&ss=exc Deep Earthquakes] "Cambridge University Press"]
depth=convert|647|km|mi|0
location=coord|13|7|S|67|3|W [http://www.reliefweb.int/rw/RWB.NSF/db900SID/OCHA-64DJMQ?OpenDocument UN DHA Information Report No.1] "United Nations Department of Humanitarian Affairs"]
countries affected = BOL
casualties = 1,000 from mudslides

The 1994 Bolivia earthquake occurred on June 9, 1994. The epicenter was located in a sparsely populated region in the Amazon jungle, about 200 miles from La Paz.

Harvard assigned it a focal depth of 647 km and a magnitude MW of 8.2, making it the largest earthquake since the Sumbawa earthquake of 1977. It is also the largest earthquake ever recorded with a focal depth greater than 300 km. South America also experienced the second and third largest earthquakes at focal depths greater than 300 km: Colombia, 1970; and northern Peru, 1922.

Description

The rupture was located on the Nazca plate where it is being pushed beneath the mantle of the South American continent. [http://www.cambridge.org/us/catalogue/catalogue.asp?isbn=9780521828697&ss=exc Scientists Get a Closer Look at Mechanism of Deep Bolivian Quake] "American Geophysical Union"] It shook the ground from Argentina to Canada and its oscillations were the first to be captured on a modern seismic network. Light damage to buildings was felt in Sao Paulo, Brazil, and Toronto, Canada. [http://query.nytimes.com/gst/fullpage.html?res=990CE0DB1538F932A25757C0A963958260&sec=&spon=&pagewanted=all Bolivia Shakes, and So Does Theory on Deep Quakes] "New York Times"]

Aftermath

The seismic event killed no people directly, though a mudslide triggered by the earthquake killed an official total of 253 people. [http://query.nytimes.com/gst/fullpage.html?res=990CE0DB1538F932A25757C0A963958260&sec=&spon=&pagewanted=all Colombia Says Quake Toll May Exceed 1,000] "New York Times"] However, Juan Manuel Uribe, an officer at the National Disaster Prevention Office in Bogota, suggested that in fact more than 1,000 people may have been killed by the mudslide. Some of the survivors had no food, water or shelter, and spent freezing nights on hillsides waiting for helicopters. More than 12 villages were destroyed by the mudslide in the Paez River Valley in the Andes.

The quake also destroyed scientists' opinions on deep earthquakes. According to the squeeze theory of earthquakes, pressures and temperatures at the depth of 200 to 400 miles should be so great that rock should not undergo frictional sliding; most geologists believed that the crushing pressures and increasing heat below a certain depth compressed rocks into forms that were denser, creating huge cracks in the earth's surface. The Bolivian earthquake was 395 miles below sea level and, according to geologist Paul G. Silver, " [the earthquake] looks and acts and talks like these shallow earthquakes. But it shouldn't exist."

References