1970 Colombia earthquake

Date	July 31, 1970 (1970-07-31)
Magnitude	8.0 Mw[1]
Depth	651 km (405 mi)
Epicenter	1°28′S 72°34′W / 1.46°S 72.56°W / -1.46; -72.56Coordinates: 1°28′S 72°34′W / 1.46°S 72.56°W / -1.46; -72.56
Areas affected	Colombia
Casualties	1

The 1970 Colombia earthquake occurred in Colombia on July 31.

Details and aftermath

The earthquake hit at 17:08 UTC on July 31, 1970.^[2] It registered 8.0 on the Richter scale, and it killed one person, injuring multiple others. Because it had a depth of 651 km (405 mi), it spread over an extensive area and caused shaking in San Juan, Bogotá, Caracas, Buenos Aires, and São Paulo; it was felt as far north as Mexico City.^[2] Its depth forestalled more serious casualties,^[2] and there were no aftershocks.^[3]

The depth of the earthquake prompted scientists in South America to install seismometer networks focused on long-period earthquakes.^[2] Until the 1994 Bolivia earthquake, the 1970 Colombia earthquake was famous among seismologists as the largest deep earthquake.^[4]

Analysis

A study completed by Dziewonski and Gilbert (1974) determined that the earthquake had featured isotropic compression, or an increase in density near the rupture point similar to an implosion;^[5] this was released to great controversy.^[4] They also claimed that the compression had been initiated 80 seconds before the actual earthquake's short-period shaking. Many studies have reached differing conclusions including a dearth of isotropic movement, and many scientists feel that resolution created errors in Dziewonski and Gilbert's findings.^[6] In 1997, Russakoff, Ekstrom, and Trump reassessed their findings utilizing more advanced equipment that factored in shear wave splitting and coupling (the measure of how tightly locked two sides of a fault or plate are) and confirmed that there was very little isotropic compression.^[4]

References

Sources

• Karato, Shun'ichiro (2003). The Dynamic Structure of the Deep Earth: An Interdisciplinary Approach. Princeton University Press. ISBN 978-0691095110. 
• Kennett, L.N. and Simons, R.S. (1976). "An Implosive Precursor to the Colombia Earthquake 1970 July 31". Geophysical Journal International (Oxford University Press) 44: 471–482. Bibcode:1976GeoJI..44..471K. doi:10.1111/j.1365-246X.1976.tb03668.x. 
• Russakoff, Daniel, Ekstrom, Goram, and Tromp, Jeroen (September 10, 1997). "A new analysis of the great 1970 Colombia earthquake and its isotropic component". Journal of Geophysical Research (American Geophysical Union) 102 (B9): 20,423–20,434. doi:10.1029/97jb01645.