1973 Colima earthquake

On January 30, at 15:01 (UTC–6), a magnitude 7.5 earthquake struck 43 km beneath the Sierra Madre del Sur range in the Mexican states of Colima, Jalisco and Michoacán. On the Mercalli intensity scale, the earthquake reached a maximum intensity of VIII, causing damages to the region. In all, 56 people were killed and about 390 were injured.[1]

1973 Tecomán earthquake
UTC time1973-01-30 21:01:12
ISC event765442
USGS-ANSSComCat
Local date30 January 1973 (1973-01-30)
Local time15:01 CT
Duration2 minutes 40 seconds
Magnitude7.5 Ms
7.6 Mw 
Depth43.0 km
Epicenter18.481°N 102.996°E / 18.481; 102.996
FaultMiddle America Trench
TypeThrust
Areas affectedMexico
Max. intensityVIII (Severe)
TsunamiYes
AftershocksYes
Casualties56 dead
390 injured

Tectonic setting

Off the west coast of Mexico is the Middle America Trench; a convergent plate boundary where the Cocos and Rivera plates subducts beneath the North American Plate at a rate of ~6-9 cm/yr.[2] The interface of this plate boundary is a huge thrust fault fault known as a megathrust which occasionally produces large megathrust earthquakes and tsunamis.

Earthquake

The January 30 earthquake ruptured a shallow-angle section of the megathrust near a triple junction with the Rivera Plate. Its location places it very close to the rupture patch from the 1941 earthquake. The depth of the event varies between authors, from as shallow as 8 km to 35 km, while the USGS-ANSS event page places it at 43 km. It is estimated that a 145 km by 85 km section of the subduction zone was involved in the rupture which propagated at a velocity of 2.7 km/s.[3][4][5] Prior to the earthquake, that section of the subduction zone was designated a seismic gap which has not experience any earthquakes in recent memory.[6] The Mexico City earthquake rupture would overlap that of the 1973 quake 12 years later.[7]

Effects

The earthquake was powerful enough to be felt across the country to the Gulf of Mexico. Severe shaking and heavy damages were limited to Colima, Jalisco and Michoacán. Fifty six people died and 390 were injured by this event. Tecomán and Coahuayana suffered significant damages from the violent ground motions. Landslides and ground fissures were discovered along the relatively unpopulated coasts of Michoacán. Water, electricity and telephone lives were cut throughout.

In Mexico City, the earthquake was felt strongly in the north and western part of the city for at least 40 seconds. It caused mass hysteria and light damages to high-rise buildings.[8]

Tsunami

A moderate tsunami with amplitudes of 0.40 to 1.16 meters was observed along the Mexican coast.[9][10] Tidal gauges in Hawaii also recorded the tsunami at 0.21 meter.[10]

See also

References
  1. "Significant Earthquake MEXICO: S, FARIAS, TECOMAN". NGDC. Retrieved 1 January 2021.
  2. "Do slow slip events trigger large and great megathrust earthquakes?". Science Advances. 4 (10). 2018. doi:10.1126/sciadv.aat8472.
  3. Miguel A. Santoyo, Takeshi Mikumo and Luis Quintanar (2006). "Faulting process and coseismic stress change during the 30 January, 1973, Colima, Mexico interplate earthquake (Mw=7.6)". Geophysics International (in Spanish). 45: 163–178.
  4. Stuart V. Schmitt, Charles DeMets, J. Stock, O. Sánchez, B. Márquez-Azúa, G. Reyes (2007). "A geodetic study of the 2003 January 22 Tecomán, Colima, Mexico earthquake". Geophysical Journal International. 169: 389–406. doi:10.1111/j.1365-246X.2006.03322.x.CS1 maint: multiple names: authors list (link)
  5. Santoyo, Miguel A.; Mikumo, Takeshi; Menzoza, Carlos (2007). "Possible lateral stress interactions in a sequence large interplate thrust earthquakes on the subducting Cocos and Rivera plates". Geofísica Internacional. 46 (4): 211–226.CS1 maint: multiple names: authors list (link)
  6. Shri Krishna Singh, Luciana Astiz (1981). "Seismic gaps and recurrence periods of large earthquakes along the Mexican subduction zone: A reexamination". Bulletin of the Seismological Society of America. 71 (3).
  7. lesias, Alcocer, S., Gutiérrez, C., Vaid, C., Kostoglodovll, V., Almora, D., Ayala, M., Castro, G., Cruz, J.L., Duran, R., Echavarria, A., G., Espitia, Estrada, J., Flores, L., Guevara, E., Javier, C., López, C., López, O., Macías, M., Mena, E., Ortiz, M., Pacheco, M.A., Perez, C., Pérez, J., Ramírez, M., Romo, M., Ruiz, A., Sandoval, H., Santoyo, M., Torres, M., Vazqu, R., J., Velasco, M., & Ylizaliturri, J. (2003). "A Preliminary Report on the Tecoma'n, Mexico Earthquake of 22 January 2003 (Mw 7. 4) and Its Effects" (PDF). Seismological Research Lettes. 74 (3): 279–289.CS1 maint: multiple names: authors list (link)
  8. "10 REPORTED KILLED IN A QUAKE IN MEXICO". The New York Times. Archived from the original on 31 January 1973. Retrieved 1 January 2021.
  9. "Tsunami Event Information S. MEXICO". NGDC. Retrieved 1 January 2021.
  10. Coffman, Jerry L. (1975). "United States Earthquakes, 1973". US Geological Survey.
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