1994 Bolivia earthquake
|Date||June 9, 1994|
|Magnitude||8.2 Mw |
|Depth||647 kilometres (402 mi) |
Harvard assigned it a focal depth of 647 km and a magnitude MW of 8.2, making it, at the time, the largest earthquake since the Sumbawa earthquake of 1977, later superseded by more recent larger events (e.g., 2004 Indian Ocean earthquake). It is also the second largest earthquake ever recorded with a focal depth greater than 300 km, the largest currently being the 2013 Okhotsk Sea earthquake. South America also experienced the then second and third largest earthquakes at focal depths greater than 300 km: Colombia, 1970; and northern Peru, 1922.
The rupture was located on the Nazca plate where it is being pushed beneath the mantle of the South American continent. 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.
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."
- Frohlich, Cliff (2010). Deep Earthquakes. Cambridge University Press. ISBN 9780521123969.
- UN DHA Information Report No.1 United Nations Department of Humanitarian Affairs
- Wakefield, J. (1995). "Scientists Get a Closer Look at Mechanism of Deep Bolivian Quake". Eos (American Geophysical Union) 76 (2): 9–10.
- Broad, William J. (April 11, 1995). "Bolivia Shakes, and So Does Theory on Deep Quakes". The New York Times.