1994 Bolivia earthquake
|UTC time||1994-06-09 00:33:17|
|Local date||June 8, 1994|
|Magnitude||8.2 Mw |
|Depth||647 kilometres (402 mi) |
|Casualties||5 dead (unconfirmed)|
The Harvard CMT Project 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647 km and a magnitude MW of 8.2, making it, at the time, the largest earthquake since the 1977 Sumba earthquake, later superseded by more recent larger events (e.g., 2004 Indian Ocean earthquake).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, along with the 2018 Fiji earthquake, 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 within the Nazca plate where it is being subducted 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. Such deep events are known as intraplate earthquakes because they occur within a tectonic lithosphere rather than at the boundary of two. The earthquake involved a particularly small fault area of only 30 km by 50 km for 22 seconds at a rupture velocity of 1.5 km/s.
The quake also disproved 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 had believed that the crushing pressures and increasing heat, below a certain depth, compressed rocks into deeper forms, 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."
There are unconfirmed reports that five people were killed in Peru's Arequipa and Cuzco provinces. Three deaths from Arequipa Province were attributed to a landslide while the other two in Cuzco Province died from falling debris or a heart attack. Many more were left injured due to landslides in other parts of Southern Peru. In Cochabamba, La Paz and Oruro, the windows of many tall structures shattered. Light damage to buildings was also reported in Arica, Chile and Manaus, Brazil, although all these claims have not verified. Light damage to buildings was felt in Sao Paulo, Brazil, and Toronto, Ontario, Canada. In Chile, panic caused many residents of major cities ran out of buildings. The earthquake also disrupted power and communication services.
Due to the earthquake's great depth, it was felt at places extremely far from its epicenter. According to the Los Angeles Times and US Geological Survey, the earthquake was described as very gentle. Similar effects were observed in Sioux Falls, Sioux City, Minneapolis, and Omaha in the United States.
- 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. 76 (2): 9–10. Bibcode:1995EOSTr..76....9W. doi:10.1029/EO076i002p00009-02 (inactive 2021-01-15).CS1 maint: DOI inactive as of January 2021 (link)
- Zhongwen Zhan, Hiroo Kanamori, Victor C. Tsai, Donald V. Helmberger, Shengji Wei (2014). "Rupture complexity of the 1994 Bolivia and 2013 Sea of Okhotsk deep earthquakes". Earth and Planetary Science Letters. 385: 89–96. doi:10.1016/j.epsl.2013.10.028. ISSN 0012-821X. Retrieved 16 March 2021.CS1 maint: multiple names: authors list (link)
- Broad, William J. (April 11, 1995). "Bolivia Shakes, and So Does Theory on Deep Quakes". The New York Times.
- "BOLIVIA-PERU: AREQUIPA, FELT IN N AND S AMERICA". NGDC NCEI. NCEI. Retrieved 16 March 2021.
- LA TIMES STAFF AND WIRE REPORTS (1994-06-09). "Major Earthquake in Bolivia Is Felt as Far Away as Toronto". Golden, Colorado: The Los Angeles Times. The Los Angeles Times. Retrieved 16 March 2021.