1942 Ecuador earthquake

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1942 Ecuador earthquake
1942 Ecuador earthquake is located in Ecuador
1942 Ecuador earthquake
UTC time1942-05-14 02:13:27
ISC event900274
USGS-ANSSComCat
Local date13 May 1942
Local time09:13 ECT
Magnitude7.8 Mw
7.9-8.3 Ms
7.7 mb
Depth20.0 km
Epicenter0°01′30″N 79°57′18″W / 0.025°N 79.955°W / 0.025; -79.955Coordinates: 0°01′30″N 79°57′18″W / 0.025°N 79.955°W / 0.025; -79.955
FaultEcuador–Colombia megathrust
TypeThrust
Areas affectedEcuador
Total damage$40 million (2021 rate)
Max. intensityIX (Violent)
Aftershocks11 recorded
Casualties300+ dead

The 1942 Ecuador earthquake or the 1942 Guayaquil earthquake occurred on 13 May at 9:06 or 9:13 am ECT with a moment magnitude of 7.8. The temblor struck the coastal regions of Ecuador, causing damage mainly to cities like Guayaquil, Portoviejo and Guaranda, particularly towards reinforced concrete buildings.[1] More than 300 people lost their lives and the total damage cost about US$2.5 million (1942 rate) as a result of the quake.[2][3] Ecuador's largest city Guayaquil was the most affected despite the significant distantce from the epicenter. Many reinforced concrete structures in the city were completely destroyed.[4]

Tectonic setting[]

The Nazca Plate dives beneath the South American Plate along a convergent plate boundary stretching from Colombia to Chile in a process known as subduction. This plate boundary occasionally produces large megathrust earthquakes along the west coast of South America. The Ecuador–Colombia subduction zone occupies part of this plate boundary, where the convergence rate is between 5 and 8 cm/yr.[5] As the plates converge, elastic energy is stored at the subduction zone where friction between the plates locks them in place. Once the strain at the subduction is too great, the plates slip and the subduction zone ruptures in an earthquake.

Earthquake[]

Map of the Carnegie Ridge showing the epicenter location of the 1942 earthquake.
The northern flank of the Carnegie Ridge as it is underthrusted beneath the coast of Ecuador, where the earthquake occurred.

The earthquake struck with a hypocenter depth of 20 km, and an epicenter about 15 km west of Pedernales at 02:13 a.m. local time. The capital Quito was located some 165 km from the epicenter of the quake.

The earthquake of 1942, which was one of the largest in the country, partially ruptured a section of the subduction zone that was involved in the 1906 Ecuador–Colombia earthquake. The 1906 event broke the subduction zone for approximately 500 km. The approximate epicentral location of the 1942 quake calculated to be along the northern flanks of the Carnegie Ridge. In a period of 22 seconds, the seismic moment of the rupture was released in one simple event. Based on relocation of the aftershocks, and examining the distribution, the earthquake had ruptured a 200 km by 90 km section of the subduction zone.[6]

It is the first event in a sequence of large earthquakes that would re-rupture the subduction zone. Subsequent events would follow-up in 1958, 1979 and 1998. The recent 2016 event was a repeat of the 1942 earthquake.[7][8][9] This was similar to what was observed in Sumatra, Indonesia in the beginning of the 21st century with multiple earthquakes rupturing the Sunda subduction zone rather than in one large event.[10]

The earthquakes of 1942 and 2016 are part of a cycle of repeated events with an average recurrence interval period of 74 years, indicating the next event may occur in 2090.[11]

Effects[]

Ecuador's largest city Guayaquil suffered the worst during the earthquake, with more than 100 lives lost, and numerous high-rise collapses. Damage was also observed in Manabí, Guayas, Los Ríos, Esmeraldas, Bolívar and Imbabura.[12]

Moderate to high damage was reported in the Guayaquil; at least 250 km from the earthquake. In the commercial center, the earthquake had a maximum intensity of IX (Violent) to VIII (Severe) on the Mercalli intensity scale, while the rest of the city and surrounding towns were exposed to intensity VII (Very strong) to VI (Strong).[13] Countless buldings inclusing cinemas and theaters were destroyed or damaged. In this zone of high intensity, one reinforced concrete building completely collapsed while another was almost completely destroyed. Three tall reinforced concrete structures and a number of buildings single or double storey-tall suffered complete collapse. One building that housed a clinic on the first floor crmumbled to the ground, killing 29 individuals.[14] Three additional structures had beams on their first floors so badly rendered that supports had to be installed immediately before they could be repaired or demolished.[13] The location where the strongest intensity was felt in Guayaquil is just west of the Guayas River, and south of Cerro Del Carmen. The reason for the sudden violent shaking in this part of the city was attributed to its location—the city is built on water-saturated clay and alluvium deposited by the Guayas River.[13] This local geological setting amplified the seismic waves which worsened the strength of ground motion in the city.[13]

Further heavy damage was reported in the cities of Chone, Portoviejo, Manta, Junín, Calcetan and Pedernales. In the Naranjal Canton, large fissures formed in the ground which allowed a "foamy liquid" to erupt. Many homes and buildings situated along the coast were seriously damaged or destroyed.[12]

Shaking was felt as far as the Oriente region in the east, and the border towns of Colombia in the north.[12]

After the mainshock, two strong aftershocks rocked the coast of Ecuador, causing more panic.[15] Many surviving residents decided to live in the streets during the night for fear of more damage in their homes.[14]

See also[]

References[]

  1. ^ "Seismic Hazard Assessment for Guayaquil City (Ecuador): Insights from Quaternary Geological Data" (PDF). Final Meeting of the Dark Nature Project: 55–56.
  2. ^ "Significant Earthquake Information ECUADOR: GUAYAQUIL". NGDC. Retrieved 19 January 2021.
  3. ^ "Sismo de 7,8 también dejó dolor y muerte en 1942". El Diario. 16 August 2016. Retrieved 16 July 2021.
  4. ^ Roberto Aguiar; Enrique Morales; Kervin Chunga; Evelyn Iza; y Fernando Del Castillo (2016). "Acelerogramas y espectros inferidos del terremoto 1998 (Mw 7,2), Bahía de Caráquez, Ecuador". Ágora de heterodoxias. Barquisimeto, Venezuela: Universidad Centroccidental “Lisandro Alvarado”. 2 (2). ISSN 2443-4361.
  5. ^ Yamanaka, Y., Tanioka, Y. & Shiina, T. (2017). "A long source area of the 1906 Colombia–Ecuador earthquake estimated from observed tsunami waveforms". Earth Planets Space. 69: 163. doi:10.1186/s40623-017-0750-z.CS1 maint: multiple names: authors list (link)
  6. ^ Pararas-Carayannis, G. (2012). "Potential of tsunami generation along the Colombia/Ecuador subduction margin and the Dolores-Guayaquil mega-thrust" (PDF). Science of Tsunami Hazards. 31 (3): 209–230. Retrieved 19 March 2021.
  7. ^ "CUATRO AÑOS DESPUÉS DEL TERREMOTO DE PEDERNALES: UN TESTIMONIO SOBRE EL PELIGRO SÍSMICO EN EL ECUADOR". Instituto Geofisico. 16 April 2020. Retrieved 19 January 2021.
  8. ^ Lingling Ye; Hiroo Kanamori; Jean-Philippe Avouac; Linyan Li; Kwok Fai Cheung; Thorne Lay (2016). "The 16 April 2016, MW 7.8 (MS 7.5) Ecuador earthquake: A quasi-repeat of the 1942 MS 7.5 earthquake and partial re-rupture of the 1906 MS 8.6 Colombia–Ecuador earthquake" (PDF). Earth and Planetary Science Letters.
  9. ^ "M 7.2 - near the coast of Ecuador". USGS-ANSS. Retrieved 19 January 2021.
  10. ^ B. Gombert, Z. Duputel, R. Jolivet, M. Simons, J. Jiang, C. Liang, E.J. Fielding, L. Rivera (2018). "Strain budget of the Ecuador–Colombia subduction zone: A stochastic view". Earth and Planetary Science Letters. 498: 288–299. doi:10.1016/j.epsl.2018.06.046. ISSN 0012-821X.CS1 maint: multiple names: authors list (link)
  11. ^ Moncayo Theurer, M; Velasco, G.; Mora, Carlos; Montenegro, M; Cordova, J (2017). "Terremotos mayores a 6.5 en escala Richter ocurridos en Ecuador desde 1900 hasta 1970" [Earthquakes greater than 6.5 on the Richter scale that occurred in Ecuador from 1900 to 1970] (PDF). Ingeniería (in Spanish). Mérida, México: Universidad Autónoma de Yucatán. 21 (2): 55–64. Retrieved 16 July 2021.
  12. ^ Jump up to: a b c "Catálogo de Terremotos del Ecuador" (PDF). Retrieved 16 July 2021.
  13. ^ Jump up to: a b c d Villacres, Alex (1996). "The 1942 Guayaquil earthquake, recent evidences" (PDF). Eleventh World Conference on Earthquake Engineering. 131. ISBN 0-08-042822-3 – via Elsevier.
  14. ^ Jump up to: a b González Mora; Iván Eduardo (2012). "Actualización de la evaluación del riesgo sísmico en edificios de hormigón armado en los sectores con mayor riesgo sísmico de Guayaquil" [Update of the seismic risk assessment in reinforced concrete buildings in the sectors with the highest seismic risk in Guayaquil]. Degree Works - Civil Engineering Career (in Spanish). UNIVERSIDAD CATOLICA DE SANTIAGO DE GUAYAQUIL. Retrieved 16 July 2021.
  15. ^ "ISC Bulletin: event catalogue search". International Seismological Centre. doi:10.31905/D808B830. Retrieved 16 July 2021.
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