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1920 Xalapa earthquake

Coordinates: 19°16′N 97°05′W / 19.27°N 97.08°W / 19.27; -97.08
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1920 Xalapa earthquake
A partially destroyed church in Saltillo Lafragua
1920 Xalapa earthquake is located in Mexico
1920 Xalapa earthquake
UTC time1920-01-04 04:22:16
ISC event912397
USGS-ANSSComCat
Local date3 January 1920
Local time22:25 CST
MagnitudeMw 6.3–6.4
Depth15 kilometres (9.3 mi)
Epicenter19°16′N 97°05′W / 19.27°N 97.08°W / 19.27; -97.08[1]
TypeNormal
Areas affected
Max. intensityMMI XII (Extreme)
Aftershockscontinued until April 1920
Casualties648–4,000 killed

A moment magnitude 6.3–6.4 earthquake affected the Trans-Mexican Volcanic Belt in the states of Puebla and Veracruz, Mexico on 3 January 1920 at 22:25 CST.[2] A maximum Modified Mercalli intensity of XI–XII (Extreme) was assigned in the epicenter, between Chilchotla and Patlanalán. Its aftershocks were recorded by a seismograph yielding data that suggested the mainshock originated within the Earth's crust. Earthquakes beneath the volcanic belt, although infrequent, pose a significant threat due to their proximity to highly populated towns. Their rarity, with return periods of several thousand years also mean past seismic-hazard zoning projects have classified the region as non-hazardous. These earthquakes are caused by normal faulting which may have been identical to the one involved in 1920. They are the result of ongoing extension within the volcanic belt which are accommodated by normal faults.

The earthquake killed between 648 and 4,000 people; many deaths were attributed to mudslides that swept through several settlements along the Huitzilapa and Pescado rivers. Many buildings, especially the masonry kind, were badly damaged or totally ruined. The towns of Patlanalá, Barranca Grande, Cosautlán, Quimixtlán and Teocelo were severely affected. Wooden jacales generally performed well during the earthquake but some were destroyed. The total cost of damage was estimated at US$25 million.

The Veracruz government took immediate action in the aftermath—providing assistance and establishing communication services. Governor Cándido Aguilar formed a disaster relief board and travelled to several towns to participate in distributing resources. The devastated towns of Xalapa, Coatepec, Cosautlán, Coscomatepec, Patlanalá, Quimixtlán, Huatusco and Ayahualco were given funds for reconstruction. The Bishop of Veracruz, Rafael Guízar y Valencia, also assisted in the relief efforts and N$20,000 in donations. Civil society groups and civilians also participated in relief efforts through joining relief committees and raising funds. Meanwhile, the newspapers overdramatized their reports and falsely claimed that volcanoes in the area were erupting. However, some organised fundraising or promoted relief efforts; eventually, more than N$300,000 were raised.

Tectonic setting

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Main article: Plate tectonics
A cross-sectional diagram illustrates the flat slab subduction beneath Mexico, showing the Cocos plate sharply plunging beneath central Mexico. Earthquake epicenters are marked along the descending slab. Near the Mexican coast, the slab dips to around 30–40 kilometers and continues at this depth for about 300 kilometers inland before bending steeply. It then descends further to approximately 250 kilometers, beyond which it is no longer detectable.
Cross diagram of flat slab subduction and steep plunging of the Cocos plate beneath central Mexico[a]

Mexico lies at the convergence of three tectonic plates. The Mexican landmass rests atop the westward-moving North American plate. Oceanic lithosphere of the Cocos and Rivera plates subducts northwestwards[3] along the Middle America Trench.[4] Seismic strain at the subduction zone causes earthquakes and tsunamis when released. Volcanism occurs when the subducting plates (slabs), dehydrate during metamorphism. The water that is driven off causes some of the overlying mantle material to melt and rise through the overriding plate, forming volcanoes.[5] The Trans-Mexican Volcanic Belt (TMVB) stretches over 1,000 km (620 mi) from the Pacific coast to the Gulf of Mexico. Instead of running trench-parallel, it aligns obliquely along the trench where the Cocos and Rivera plates subduct at different angles.[3] In Jalisco, the Rivera plate subducts at 50°, while from Michoacán to Guerrero, the Cocos plate's subduction angle progressively decreases.[6] From Guerrero to Oaxaca, the slab is subhorizontal, causing flat slab subduction for 250 km (160 mi).[7] Southeastwards, from Oaxaca to Central America, the slab gradually plunges to about 50–60°.[6]

Volcanism usually occurs directly above slabs that undergo metamorphism at around 100 km (62 mi) depth, which typically happens about 100 km (62 mi) from the trench. In southern Mexico, flat-slab subduction causes the slab to reach this depth 300 km (190 mi) from the trench. As a result, the volcanic arc is further than typical.[5] Intraslab earthquakes within the Cocos plate occur at 60–100 km (37–62 mi) depth, but cease abruptly some 100 km (62 mi) south of the TMVB, possibly because the slab does not produce earthquakes in the north before plunging steeply to 120 km (75 mi) depth beneath the TMVB.[8] Shallow intraplate earthquakes within the TMVB happens north of where intraslab seismicity cease. Crustal deformation in the TMVB is characterized by extension.[8] East–west striking normal faults form as a result of this tectonic deformation. Some of these faults are visible for over 50 km (31 mi).[9][10] Offsets within the alluvium and Quaternary cinder cones suggests recent geologic activity on these faults. On average, these faults move at 2 mm (0.079 in) per year, and because of their active state, they can produce earthquakes.[10]

Animated picture of a block representing the cross section of the Earth's crust being offset along diagonal faults
Normal faulting within the crust caused by extension

Since 1568, known shallow crustal earthquakes in the TMVB have been documented with magnitudes as large as Mw  7.6.[11] A brief account of an earthquake affecting Xalapa in 1546 may be an earlier example of shallow crustal seismicity.[12] Seismicity in the TMVB is infrequent, with the most recent major earthquakes being the 1912 Acambay (Mw  6.9) and 1920 Xalapa events.[13] Veracruz experiences moderate seismicity compared to the Pacific coast,[14] where the subduction zone displays greater activity.[15] Some earthquakes with epicenters in the state have been deadly, such as those in 1959 and 1967. The 1973 earthquake though with an epicenter outside the state, caused significant destruction and deaths.[14]

Mexico is one of the most seismically active regions of the world;[16] nearly 52 million people or 40 percent of the population live around the TMVB.[17] Long-established seismic hazard evaluation projects,[3] such as from the Comisión Federal de Electricidad have classified it a moderate-hazard area.[18] These assessments only considered instrumentally recorded earthquakes since at least 1912, excluding several large historical events dating back to 1568.[18] In 2017, Geofísica Internacional published a study that suggested the TMVB is more vulnerable to earthquakes. The research considered instrumentally recorded and historical earthquakes from 1858, suggesting a return period of 150 years estimated for Mw  7.0 or larger events. However, the analysing only the instrumental record yielded a 12,000-year return interval.[18] A their recurrence intervals span millenniums, they rarely happen. Although moderate in magnitude compared to their subduction zone counterparts, these earthquakes can be destructive when they occur near densely populated areas.[17] Highly populated municipalities such as Mexico City, Guadalajara, Puebla and Morelia are located in close proximity to these active faults, such as the Acambay-Tixmadejé and Venta de Bravo faults and Chapala graben.[10]

Earthquake

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The earthquake had a moment magnitude (Mw ) of 6.3–6.4, and its hypocenter was 15 km (9.3 mi) beneath the surface.[19][20] Although there is no focal mechanism solution, the shock may have been caused by normal faulting along a plane striking east–west. Other earthquakes in the TMVB which occur at less than 15 km (9.3 mi) depth also rupture along normal faults, leading to this conclusion.[21] A fault length of 25 km (16 mi) was estimated using scaling relationships between the seismic magnitude and rupture length which corresponded with the meizoseismal area.[22] No ground faulting was observed either because it was too small, hidden under debris,[23] or the rupture was entirely buried in the crust.[24] According to a research published by the Bulletin of the Seismological Society of America in 1996, a 15 km (9.3 mi) lineament trending east–northeast that was identified via satellite imaging may represent the causative fault.[24]

A map of the Veracruz region overlaid by elliptical countours that denote the Modified Mercalli intensity during the earthquake varied with location.
Isoseismal map illustrating the Modified Mercalli intensity distribution

The epicenter was likely between the towns of Chilchotla and Patlanalán where the strongest shaking was observed.[19] In Chilchotla, Ixhuacán, Quimixtlán and Patlanalá, and the epicenter area, a Modified Mercalli intensity of XI–XII (Extreme) was evaluated.[25] In Xalapa, the assigned intensity was VIII–IX (Severe–Violent),[26] and in Ayahualulco, Cosautlán and Teocelo, was IX–X (Violent–Extreme).[25] The plotted isoseismal lines formed a concave footprint-like shape extending east–southeast to west–northwest. Intensities XI, X and IX covered 70.8 km2 (27.3 sq mi), 433.6 km2 (167.4 sq mi), and 955.2 km2 (368.8 sq mi), respectively.[27] Light shaking was felt in Mexico City and parts of Oaxaca's Teotitlán, Cuicatlán and San Jerónimo.[28]

There were foreshocks in the area two months prior.[19] The aftershock sequence lasted until April 1920, with some felt 220 km (140 mi) away in Mexico City. To monitor this activity, a Wiechert seismograph was installed in Xalapa.[29] Data from the seismograph indicated that these aftershocks occurred 30–40 km (19–25 mi) from where it was installed, suggesting that the preceding mainshock was a shallow focal event. In contrast, intraslab earthquakes would be located further away as they originate at more than 60 km (37 mi) depth.[30]

Damage and casualties

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The interior of a church reveals outer walls still standing, while the floor is strewn with rubble from the collapsed roof above, leaving the space open to the sky.
A collapsed church in Saltillo Lafragua

The earthquake killed 648 people,[31] although later estimates suggests up to 4,000 dead.[b][31] It caused the second highest number of deaths from an earthquake in Mexico, second to the 1985 Mexico City earthquake.[36] At least 419 deaths were from landslides triggered by the earthquake.[37] Many residents died in Patlanalá (239), Barranca Grande (101), Cosautlán (85), Quimixtlán (80) and Teocelo (35).[38] Serious damage occurred in Xalapa, Coatepec, Teocelo, Cosautlán, Ixhuacán, Ayahualulco, Calcahualco, Coscomatepec, Alpatláhuac, Rinconada, Huatusco and Córdoba.[39] Heavy destruction was attributed to building constructed with heavy masonry which were not seismic resistant.[40] At least 167 were injured, including 85 in Teocelo; 60 in Cosautlán; and 10 in Quimixtlán and Xalapa, respectively.[38] The Catholic Telegraph reported the property damage at US$25 million.[41]

Within the XI isoseismal band, landslides were concentrated along the Huitzilapa River, extending westward from Chilchotla to Acantiopa, near Patlanalá. Many occurred along the left bank and its tributaries,[42] with the region's mountainous topography and 10 days of prior heavy precipitation contributing to the phenomenon.[42][43] Initially these small landslides began obstructing the tributaries and gradually combined into a large mass. River debris also accumulated and the massive flow travelled downstream. It swept through several villages over the first 20 km (12 mi) and left deposits up to 10 m (33 ft) thick. Continuing further downhill, it transitioned to a hyperconcentrated flow.[43] After merging with the Pescado River near Teocelo, it continued for 80 km (50 mi) before entering the Gulf of Mexico, burying Acuatlatipa, El Rincón, Mecatitla, and Petlacuacán along the way.[32] Human bodies were carried by the flow towards Jalcomulco and some floated in the Antigua River near the gulf. The banks of the Pescados River were also littered with human and animal remains.[44]

Mountains in the area exhibited scars from these landslides, which transported loose earth, vegetation, and bedrock. Near Cerro Colorado and Acantiopa, some landslide deposits contained boulders up to 7 m3 (250 cu ft). In Ahuautla village, north of Quimixtlán, landslides comprising highly fragmented materials generated dust clouds that local residents interpreted as signs of volcanic activity.[42]

Ruined home in Saltillo Lafragua

In Patlanalá, there were only two residents who survived the landslide with injuries, largely because most people caught in the flow perished.[45] Some masonry buildings in the town cracked and had their pillars shifted from their alignments while wooden homes were less damaged.[46] A church and its attached rectory were destroyed. The municipal building and a shop also experienced toppled or cracked walls.[47] Some homes in Teocelo's upper district collapsed or were totally destroyed. A soldier died and his wife was injured when a church tower partially collapsed. Its roof also caved-in, leaving the main altar in ruins, and cracks appeared in the central nave arches while walls were severely cracked or crumbled.[48] The town's public offices building and a girls' school were levelled. According to the mayor, a town council member was seriously injured.[49]

The destruction in Saltillo Lafragua amounted to N$420,000, and only 51 of the 375 homes remained intact. Many stone buildings were heavily damaged while the eastern district, comprising mostly wooden jacales, was less affected. Though most adobe buildings appeared intact from their external, their ruined interiors were uninhabitable. Damage in Agua de la Mina was limited because there were few masonry buildings and only one person was injured.[50] Similarly, wooden jacales performed well in Chilchotla although some were destroyed during the shaking and the church tower and walls partially collapsed.[47] The partial collapse of Dos Corazones church in Xalapa ruined nearby houses and injured several people. The Francisco I. Madero orphanage, a government palace and the municipal building were damaged, along with nine streets.[51] Nearly all buildings along Enriquez Street were damaged with few remaining unaffected. Improperly erected supports meant to stabilize these buildings worsened the damage.[52] The number of injured people in one civil hospital overwhelmed the facility; it was also severely cracked and at risk of collapse.[51] In Orizaba, several homes collapsed and other buildings were cracked.[53]

Response

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Buildings along Enríquez Street sustained considerable damage

Governmental and civilian relief efforts were mobilised in the wake of the destruction and to provide aid. On 6 January, Cándido Aguilar resumed his position as Governor of Veracruz, then held by interim governor Armando Deschamps. He formed a disaster relief board and, with military assistance, traveled to Huatusco, Córdoba, Xalapa, and Coatepec, distributing money, food, and clothing.[54] Public infrastructure and buildings were reconstructed under his supervision, and refuge shelters opened in the worst-affected areas such as Teocelo.[55] Aguilar also ordered civic and military authorities in Xalapa, Coatepec, Xico, Teocelo, Cosautlán, and Ayahualulco to support Harry Hopkins and Haner Borst, members of the American Red Cross. The pair were accompanied by Catholic priest Francisco J. Krill to assess the impact and offer aid.[56] Additional Red Cross members and medical personnel treated injured survivors and buried the dead.[41]

Charities and civil societies also supported the effort;[55] the San Francisco de las Peñas municipal government initiated a donation drive, and state employees contributed a day's wages.[51] The Francisco Verdad, a fraternal organization of the National Mexican Rite requested for donations from its members through the local newspaper, El Dictamen.[57] The publication participated in promoting and organizing Guízar's fundraising efforts; by 9 January, more than N$300,000 were raised. Other newspapers such as El Universal and Excélsior organized public donation drives in Mexico City.[58] For reconstruction, Xalapa, Coatepec, and Cosautlán received N$60,000 each; Coscomatepec received N$25,000; Patlanalá, Quimixtlan, and Huatusco received N$20,000 each; and Ayahualco received N$5,000.[59] The federal government also reserved N$40,000 for affected individuals.[49] The Governor of Sonora, Adolfo de la Huerta, donated N$4,078 to relief organisations in both states.[60] In Xalapa, there were at least 74 individual requests for assistance due to damaged homes from January to early February. Additionally, the police inspected and evicted residents from buildings deemed collapse-prone.[53] Restoring the government palace's ceiling lights, paintings, and decorations amounted to over N$13,300.[61]

Rafael Guízar y Valencia, the Bishop of Veracruz, coordinated relief and donation activities. One of these was a meeting that raised N$20,000.[62] In Teocelo, Guízar officiated a sermon for its residents and distributed N$3,000 among them. He also preached sermons in other affected areas and continued to tour the area until 1921.[63] Mexico also received international assistance and condolences from other nations including the United States and Germany. The San Antonio-based Spanish-language newspaper La Presna raised US$15,000 while the governments of El Salvador and Honduras sent US$10,000 each and declared a period of mourning. Pope Benedict XV also donated an undisclosed amount.[41]

The press sensationalized the disaster;[64] early reports exaggerated the death toll and destruction. Reports of volcanic activity on Pico de Orizaba and Cofre de Perote were dismissed.[64] Mexico City newspapers also wrote that Veracruz was destroyed, which its city officials refuted.[65]

See also

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Notes

[edit]
  1. ^ See 2017 Puebla earthquake for 09-19 Earthquake.
  2. ^ 700,[32] 800,[33] 1,500 and[34] 4,000.[35]

References

[edit]
  1. ^ Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1953.
  2. ^ National Seismological Service n.d., p. 1.
  3. ^ a b c Suárez, Caballero-Jiménez & Novelo-Casanova 2019, p. 3545.
  4. ^ Benz et al. 2011.
  5. ^ a b Tectonics Observatory 2009.
  6. ^ a b Castellanos, Clayton & Pérez-Campos 2018, p. 7741–7742.
  7. ^ Pardo & Suárez 1995, p. 12357.
  8. ^ a b Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3545–3546.
  9. ^ Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1952.
  10. ^ a b c Viveros, Reynoso & Schroeder 2017, p. 90.
  11. ^ Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3545–3547.
  12. ^ Suárez & Novelo-Casanova 2018, p. 1894.
  13. ^ Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3548–3556.
  14. ^ a b Flores et al. 2019, p. 96.
  15. ^ Stevens 2017.
  16. ^ Agence France-Presse 2021.
  17. ^ a b Andrews 2019.
  18. ^ a b c Viveros, Reynoso & Schroeder 2017, p. 88.
  19. ^ a b c Suárez & Novelo-Casanova 2018, pp. 1896–1897.
  20. ^ ISC 2022.
  21. ^ Córdoba-Montiel et al. 2018, p. 93.
  22. ^ Suárez & Novelo-Casanova 2018, pp. 1897–1898.
  23. ^ Suárez & Novelo-Casanova 2018, p. 1897.
  24. ^ a b Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1956.
  25. ^ a b Flores & Camacho 1922, p. 24.
  26. ^ Córdoba-Montiel et al. 2018, p. 90.
  27. ^ Flores & Camacho 1922, p. 94–95.
  28. ^ Flores & Camacho 1922, p. 25.
  29. ^ Suárez & Pérez-Campos 2020, p. 6.
  30. ^ Córdoba-Montiel et al. 2018, p. 92.
  31. ^ a b National Geophysical Data Center / World Data Service (NGDC/WDS) 1972.
  32. ^ a b Suárez & Novelo-Casanova 2018, p. 1896.
  33. ^ Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3558.
  34. ^ Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1955.
  35. ^ Miyamura 1988, p. 401–419.
  36. ^ Torres et al. 2012, p. 2.
  37. ^ National Seismological Service n.d., p. 5.
  38. ^ a b Flores et al. 2019, p. 101.
  39. ^ Sánchez 2022.
  40. ^ Flores et al. 2019, p. 100.
  41. ^ a b c "Mexican earthquake". The Catholic Telegraph. Vol. 89, no. 5. 5 February 1920.
  42. ^ a b c Flores & Camacho 1922, p. 90–92.
  43. ^ a b Carrasco-Núñez et al. 2006, pp. 161.
  44. ^ Flores & Camacho 1922, p. 37.
  45. ^ Flores et al. 2019, pp. 101–102.
  46. ^ Flores & Camacho 1922, p. 30–31.
  47. ^ a b Flores & Camacho 1922, p. 86–87.
  48. ^ Flores & Camacho 1922, p. 33–34.
  49. ^ a b Flores et al. 2019, p. 103.
  50. ^ Flores & Camacho 1922, p. 84–85.
  51. ^ a b c Flores et al. 2019, p. 104.
  52. ^ Flores & Camacho 1922, p. 34–35.
  53. ^ a b Flores et al. 2019, p. 105.
  54. ^ Flores et al. 2019, p. 106.
  55. ^ a b Flores et al. 2019, p. 109.
  56. ^ Flores et al. 2019, p. 115–116.
  57. ^ Flores et al. 2019, p. 115.
  58. ^ Freixa & Redondo 2021, pp. 112.
  59. ^ Flores et al. 2019, p. 109–110.
  60. ^ Flores et al. 2019, p. 111.
  61. ^ Flores et al. 2019, p. 95.
  62. ^ Flores et al. 2019, p. 111–112.
  63. ^ Flores et al. 2019, p. 113.
  64. ^ a b Flores et al. 2019, pp. 98–99.
  65. ^ "2000 dead in Mexican quake: disaster takes big life toll". San Diego Union and Daily Bee. 12 January 1920.

Sources

  • Miyamura, S. (1988). "Some Remarks on Historical Seismograms and the Microfilming Project". In Lee, W.H.K.; Meyers, H.; Shimazaki, K. (eds.). Historical Seismograms and Earthquakes of the World. Academic Press. pp. 401–419. ISBN 0124408702.
  • Suter, M.; Carrillo-Martfnez, M.; Quintero-Legorreta, O. (1996). "Macroseismic Study of Shallow Earthquakes in the Central and Eastern Parts of the Trans-Mexican Volcanic Belt, Mexico". Bulletin of the Seismological Society of America. 86 (6): 1952–1963. Bibcode:1996BuSSA..86.1952S. doi:10.1785/BSSA0860061952. S2CID 132743263.
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