1978 Oaxaca earthquake
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On November 29, 1978 a powerful magnitude 7.6-7.8 earthquake struck off the coast of the southern Mexican state Oaxaca.
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| UTC time | 1978-11-29 19:52:47 |
|---|---|
| ISC event | 674661 |
| USGS-ANSS | ComCat |
| Local date | 29 November 1978 |
| Local time | 11:52 PST |
| Duration | 1.5 - 2 minutes |
| Magnitude | 7.7 Ms |
| 7.8 Mw | |
| Depth | 18.0 km |
| Epicenter | 16°00′36″N 96°35′28″W / 16.010°N 96.591°W |
| Fault | Middle America Trench |
| Type | Megathrust |
| Areas affected | Mexico, Oaxaca, Mexico City |
| Max. intensity | VIII (Severe) |
| Casualties | 8 dead |
Tectonic setting
Along the west coast of Mexico, the Rivera, Cocos and Nazca Plate dives beneath the North American and Caribbean Plate in a process known as subduction. This occurs along the Middle America Trench which runs from Mexico down to Costa Rica for over 2,750 km. The subduction zone is a large thrust fault that has produced devastating earthquakes in human history. Subduction has also resulted in volcanic activity in central Mexico.
Earthquake
The earthquake ruptured an area of 5525 kilometer square along the boundary interface of the Cocos and North American Plates.[1] That particular segment has not produced any large earthquakes since 1928 and 1931 and thus considered a seismic gap. A major earthquake of magnitude 7.5 ± 2.5 was forecasted at that area in 1973.[2]
Maximum intensity in the Oaxaca area reached VIII (Severe) on the Mercalli intensity scale.
Impact
Nine people were killed, eight of those were from Mexico City one from Oaxaca. A few buildings in Mexico City had minor damage to it, this was contrary to the numerous newspaper reports that many buildings had collapsed. Eyewitness reported many buildings swaying during the earthquake. Two buildings, the Treasury Building and another owned by the Bank of Mexico suffered considerable damage to their external.[3]
References
- ^ Gordon S. Stewart Eric P. Chael Karen C. McNally (10 June 1981). "The November 29, 1978, Oaxaca, Mexico, earthquake: A large simple event". Journal of Geophysical Research. 86 – via AGU.
- ^ S. K. SINGH, J. HAVSKOV, K. McNALLY, L. PONCE, T. HEARN, M. VASSILIOU. "The Oaxaca, Mexico, Earthquake of 29 November 1978: A Preliminary Report on Aftershocks". Science. 207.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ EERI Reconnaissance Team (January 1979). Quick-Look Report On Oaxaca, Mexico Earthquake.