1978 Oaxaca earthquake
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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 | 7.8 Mw |
| Depth | 18.0 km |
| Epicenter | 16°00′36″N 96°35′28″W / 16.010°N 96.591°W / 16.010; -96.591 |
| Fault | Middle America Trench |
| Type | Megathrust |
| Areas affected | Oaxaca, Mexico City |
| Max. intensity | MMI VIII (Severe) |
| Casualties | 9 dead |
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On November 29, 1978 a moment magnitude 7.7–7.8 earthquake struck off the coast of the southern Mexican state Oaxaca.[1] The thrust-faulting event caused severe damage in Oaxaca and Mexico City.
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 5,525 km3 along with the boundary interface of the Cocos and North American Plates.[2] 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.[3] The earthquake ruptured about 80 percent of the segment designated a seismic gap and produced slip of 1.48 m (4 ft 10 in).[4]
This earthquake is well known as one out of the two earthquakes that forecasted in advance in the West. The other was the magnitude 5.9, 1975 Oroville earthquake in California, both due to irregular seismic activities in the area before the main shock.[5]
Impact
Nine people were killed, eight of those were from Mexico City and one death occurred in Oaxaca. A few buildings in Mexico City had minor damage; 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 exterior.[6] A further 100 people were injured. Falling glass and collapsing walls injured 50 people. Electricity services were cut in some areas causing major traffic jams.[7] Damage inspections by professionals led many buildings in Mexico City to close.[8]
References
- ^ ISC (2022), ISC-GEM Global Instrumental Earthquake Catalogue (1904–2018), Version 9.1, International Seismological Centre, doi:10.31905/D808B825
- ^ 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 (1980). "The Oaxaca, Mexico, Earthquake of 29 November 1978: A Preliminary Report on Aftershocks". Science. 207 (4436): 1211–1213. Bibcode:1980Sci...207.1211S. doi:10.1126/science.207.4436.1211. PMID 17776859. S2CID 21529500.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Singh, S. K.; Havskov, J.; McNally, K.; Ponce, L.; Hearn, T.; Vassiliou, M. (1980). "The Oaxaca, Mexico, Earthquake of 29 November 1978: A Preliminary Report on Aftershocks". Science. 207 (4436): 1211–1213. Bibcode:1980Sci...207.1211S. doi:10.1126/science.207.4436.1211. PMID 17776859. S2CID 21529500.
- ^ Tiedemann, H., 1992. Earthquakes and Voulcanic Eruptions. S.R.C., p.167
- ^ EERI Reconnaissance Team (January 1979). Quick-Look Report On Oaxaca, Mexico Earthquake.
- ^ Riding, Alan (30 November 1978). "Quake Hits Wide Area in Mexico; Injuries, Several Deaths Reported". The New York Times. Retrieved 24 September 2023.
- ^ "Mexican Earthquake". The Harvard Crimson. 1 December 1978. Retrieved 24 September 2023.