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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 parts of Puebla and Veracruz towards the eastern end of the Trans-Mexican Volcanic Belt, Mexico, on 3 January 1920 at 22:25 CST.[2] A maximum Modified Mercalli intensity of XI–XII (Extreme) was recorded in the epicenter, between Chilchotla and Patlanalán. The earthquake killed between 648 and 4,000 people; many deaths were attributed to mudslides that swept through settlements along the Huitzilapa and Pescado rivers. Many buildings were badly damaged or totally ruined. The towns of Patlanalá, Barranca Grande, Cosautlán, Quimixtlán and Teocelo were severely affected. The cost of damage was estimated at US$25,000,000.

There are normal faults in the volcanic belt that form because the underlying crust undergoes extension. These earthquakes can occur near highly populated towns and pose a significant hazard. The 1920 earthquake may have been caused by rupture along one of these faults within the belt. After the earthquake, a seismograph was deployed in Xalapa to record the aftershocks. The data from the seismograph suggested the mainshock originated within the North American plate at a shallow depth.

The Veracruz government immediately provided assistance; 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 government funds for reconstruction. Bishop Rafael Guízar y Valencia assisted in the relief efforts and donations. Civil society groups and civilians also participated in relief efforts, joining relief committees and raising funds. Some local newspapers overdramatized their reports and falsely claimed that volcanoes in the area were erupting. Others organised fundraising or promoted Guízar's fundraising efforts and eventually raised over US$150,000. The Salvadoran and Honduran governments, as well as Pope Benedict XV, also contributed monetary aid.

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. 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-section diagram showing change from flat slab subduction to steep plunging of the Cocos plate beneath central Mexico. Inset map shows plate boundaries and depth contours on the top of the Cocos plate slab and section location

Three tectonic plates converge off the west coast of Mexico. Most of the Mexican landmass, except Baja California,[3] forms part of the westward-moving North American plate. Oceanic lithospheres of the Cocos and Rivera plates subduct northeastward along the Middle America Trench.[4][5] Seismic strain at the subduction zone causes earthquakes and tsunamis when they are released, while volcanism occurs when the subducting plates (slabs) dehydrate during metamorphism. Released water causes the overlying mantle to partially melt and rise through the overriding plate to create volcanoes.[6] The Trans-Mexican Volcanic Belt (TMVB) stretches more than 1,000 km (620 mi) from the Pacific coast to the Gulf of Mexico. Instead of running trench-parallel, it aligns obliquely to the trend of the trench. This is because the Cocos and Rivera plates subduct at different angles.[7] The geometry of the Cocos plate shifts from constant moderate dip in the northwest to flat-slab in the southeast, producing contours on the top of the slab at around 100 km (60 mi) and beyond that aligns with the trend of the TMVB. In Jalisco, the Rivera plate subducts steeply into Earth's interior at 50° relative to the planet's surface. To the southeast, from Michoacán to Guerrero, the subduction angle progressively decreases.[8] The slab is subhorizontal between Guerrero and Oaxaca, demonstrating 165 km (100 mi) of flat slab subduction, with the top of the slap attaining a depth of roughly 50 km (30 mi).[5] Beyond Oaxaca, it gradually steepens again, reaching 50–60° beneath Central America.[8]

Normal faulting within the TMVB caused by extension

Volcanism usually occurs directly above slabs that undergo metamorphism at around 100 km (60 mi) depth, which typically happens about 100 km (60 mi) from the trench. In southern Mexico, flat-slab subduction causes the slab to reach this depth 300 km (200 mi) from the trench. As a result, the volcanic arc is located further from than the trench than is typical.[6] Beneath land, the Cocos plate generate earthquakes at 60–100 km (40–60 mi) depth, but cease abruptly some 100 km (60 mi) south of the TMVB.[9] North of where the intraslab seismicity ceases are shallow intraplate earthquakes within the TMVB. Crustal deformation in the TMVB is characterized by extension.[9] This extension occurs perpendicular to the general strike direction of the TMVB.[10] East–west striking normal faults form as a result of this tectonic deformation; some of these fault scarps are mapped for up to 50 km (30 mi).[11][12] The presence of offset 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.[12]

Mexico is one of the world's most seismically active regions;[13] nearly 52 million people (or 40 percent) of the population live around the TMVB.[14] In 2008, the Comisión Federal de Electricidad published its seismic hazard that was adopted nationwide.[7][15] They classified cities along the TMVB as a moderate-hazard region,[16] based on analyzing the seismic records since 1912. The seismic record from 1912 onwards indicated the region is characterised by infrequent earthquakes,[16] but extending the timeline to the 16th century revealed eight additional earthquakes of magnitude 5.0 to 7.6.[17] A 2017 study in Geofísica Internacional re-evaluated earthquake records from 1858 and suggested a greater risk. The researchers estimated a return period of 150 years for Mw  7.0 or larger events while analysing only the instrumental record yielded a 12,000-year period.[16] Although moderate in magnitude and occurring less frequently compared to their subduction zone counterparts, these earthquakes can be destructive if they occur near cities such as Mexico City, Guadalajara, Puebla and Morelia.[12][14]

Earthquake characteristics

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The earthquake had a moment magnitude (Mw ) of 6.3–6.4, with a hypocenter 15 km (9.3 mi) beneath the surface.[18][19] Although limited seismic data made determining the faulting mechanism challenging, the event was likely caused by an east–west striking normal fault. Similar earthquakes in the TMVB with depths of less than 15 km (9.3 mi) have focal mechanisms corresponnding to normal faulting, suggesting the mainshock had similar characteristics.[20] Using scaling relationships between the seismic magnitude and rupture length, a fault length of 25 km (16 mi) was estimated, corresponding with the meizoseismal area.[21] No ground faulting was observed probably because it was too small, obscured by debris,[22] or the rupture was entirely buried in the crust.[23] A 1996 study in the Bulletin of the Seismological Society of America identified a 15 km (9.3 mi) lineament trending east–northeast located near the meizoseismal area which may represent the causative fault.[23]

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

Based on where the strongest shaking occurred, the epicenter was likely between the towns of Chilchotla and Patlanalán.[18] A 70.8 km2 (27.3 sq mi) area,[24] including Chilchotla, Ixhuacán, Quimixtlán and Patlanalá and the epicenter, was assigned a Modified Mercalli intensity of XI–XII (Extreme) based on the damage severity.[25] The region surrounding the. meizoseismal area experienced lower intensities: 433.6 km2 (167.4 sq mi) experienced intensity X, and 955.2 km2 (368.8 sq mi) experienced intensity IX. The plotted isoseismal lines outlining these zones formed a concave footprint-like shape extending east–southeast to west–northwest.[24] In Xalapa, the assigned intensity was VIII–IX (Severe–Violent),[26] and Ayahualulco, Cosautlán and Teocelo was IX–X (Violent–Extreme).[25] Light shaking was felt in Mexico City and parts of Oaxaca's Teotitlán, Cuicatlán and San Jerónimo districts.[27]

There were foreshocks in the area two months prior,[18] while the aftershock sequence lasted until April 1920, with some felt 220 km (140 mi) away in Mexico City. To monitor the aftershocks, a Wiechert seismograph was installed in Xalapa.[28] Data from the seismograph indicated that these aftershocks occurred 30–40 km (19–25 mi) from where it was installed, confirming that the preceding mainshock was a shallow focal event within the North American plate. In contrast, deeper intraslab earthquakes would be located further from the seismograph.[29]

Since 1568, the TMVB has experienced earthquakes as large as Mw  7.6.[30] However, a brief account of an earthquake affecting Xalapa in 1546 may be an earlier example.[31] Seismicity in the TMVB is infrequent and the 1912 Acambay (Mw  6.9) and 1920 Xalapa events were the most recent Mw  6.0 or larger earthquakes.[32] Some earthquakes with epicenters in Veracruz have been deadly, such in 1959 and 1967, though these occurred near the gulf coast rather than within the TMVB.[33] The state experiences moderate seismicity compared to Mexico's Pacific coast,[34] where the subduction zone generate more earthquakes.[35] Some earthquake originating outside the state also caused significant destruction and deaths, such as in 1973.[34]

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.
Ruined home in Saltillo Lafragua.
Ruins of a church and home in Saltillo Lafragua

Reports on the death toll vary widely. Early newspaper accounts estimated between 2,000 and 4,000 casualties.[36][37][38][39] In contrast, a 1922 field report by the Seismological Society of Mexico documented 648 fatalities.[40] Later studies, published in 1988, 1996, and twice in 2018, estimated the deaths at 700, 800, 1,500, and 4,000, respectively.[41][42][43][44] It is the second deadliest earthquake in Mexico's history, behind a Mw  8.0 event that struck Michoacan in 1985, killing more than 9,500.[45][46] At least 419 deaths were from a landslide triggered by the earthquake.[47] Many fatalities were reported in Patlanalá, Barranca Grande, Cosautlán, Quimixtlán and Teocelo.[40] Eighty-five people in Teocelo, 60 in Cosautlán and 10 in Quimixtlán and Xalapa, respectively, were wounded.[40] The Catholic Telegraph reported the property damage at US$25,000,000 (equivalent to $380,232,558 in 2023[48]).[49] Many buildings in Xalapa, Coatepec, Teocelo, Cosautlán, Ixhuacán, Ayahualulco, Calcahualco, Coscomatepec, Alpatláhuac, Rinconada, Huatusco and Córdoba were affected.[50][51] Masonry buildings in these areas that lacked seismic resistance were among the badly-affected structures.[51]

The region's mountainous topography and 10 days of heavy precipitation destabalised slopes prior to 4 January.[52][53] The earthquake triggered landslides that obstructed the Huitzilapa River and its tributaries. These deposits combined with river debris, forming a mass that cascaded through multiple villages for 20 km (12 mi) and left a 10 m (33 ft) thick debris layer. Further downhill, it became a hyperconcentrated flow.[53] Between Chilchotla and Acantiopa, landslides mostly occurred along the Huitzilapa River and tributaries.[52][53] After merging with the Pescado River near Teocelo, the flow continued for 80 km (50 mi) towards the Gulf of Mexico, burying four villages along the way.[41] Human and animal remains were strewn along the Pescado River bank and bodies were carried toward Jalcomulco and the Antigua River.[54] The mountains in the area exhibited landslide scars of dislocated earth, vegetation and bedrock. Near Cerro Colorado and Acantiopa, deposits included boulders up to 7 m3 (250 cu ft).[52]

In Patlanalá, only two residents survived.[55] Some masonry buildings cracked while wooden homes were less damaged.[56] A church, rectory, municipal building and shop were damaged or destroyed.[57] In Teocelo, a church tower partially collapsed and its roof caved-in, destroying the main altar. Cracks also appeared in the nave arches while its walls were severely cracked or crumbled.[58] A public office building and school were levelled.[59]

The destruction in Saltillo Lafragua amounted to US$209,370 (equivalent to $3,184,372 in 2023[48]) and only 51 of the 375 homes remained intact. Though most adobe buildings appeared externally intact, their interiors were damaged beyond use. In the town's eastern district, where masonry buildings were scarce and most homes were wooden jacales, the impact was less extreme. There were also few masonry buildings in Agua de la Mina and the damage was limited.[60] In Chilchotla, wooden jacales resisted the shaking although some were destroyed and a church tower partially collapsed.[57] In Xalapa, the partial collapse of Dos Corazones church ruined nearby houses and injured several people, and an orphanage, government palace and municipal building were damaged.[61] Nine streets including almost all the buildings on Enriquez Street were damaged.[62] The city's hospital walls cracked but the building remained operational.[61] In Orizaba, several people were killed when their homes collapsed. Panic at a theater led several audience members to leap off the balcony, causing injuries.[63]

Response

[edit]
Buildings along Enríquez Street sustained considerable damage

Governmental and civilian relief efforts were immediately mobilised to provide aid. On 6 January, Veracruz governor Cándido Aguilar formed a disaster relief board and, with military assistance, traveled to four towns, distributing money, food and clothing.[64] Under his supervision, public infrastructure and buildings were rebuilt, and refugee shelters were established in severely impacted areas such as Teocelo.[65] Aguilar also ordered civic and military forces in affected towns to support Harry Hopkins and Haner Borst of the American Red Cross, who, accompanied by Catholic priest Francisco J. Krill, assessed the impact and offered aid.[66] Additional Red Cross members and medical personnel treated the wounded and managed burials.[49]

Charities and civil organizations contributed significantly to the recovery.[65] The San Francisco de las Peñas municipal government initiated a donation drive, while some state employees donated a day's wages.[61] For reconstruction, the local government allocated between US$2,492 (equivalent to $37,902 in 2023) and US$29,910 (equivalent to $454,910 in 2023) for each of the eight affected towns with Xalapa, Coatepec, and Cosautlán receiving the largest amount.[67][48] They also reserved US$19,940 (equivalent to $303,273 in 2023) for affected individuals.[59][48] The Sonora governor, Adolfo de la Huerta, donated US$2,033 (equivalent to $30,921 in 2023) to relief groups in Puebla and Veracruz.[68][48] In Xalapa, the police inspected and evicted residents from buildings at risk of collapse,[69] while restoring the government palace's ceiling lights, paintings, and decorations cost over US$6,630 (equivalent to $100,838 in 2023[48]).[70]

Rafael Guízar y Valencia, the Bishop of Veracruz, coordinated a donation drive.[71] El Dictamen promoted and organised Guízar's fundraising efforts, and by 9 January, raised more than US$149,550 (equivalent to $2,274,551 in 2023[48]). In Mexico City, El Universal and Excélsior organised public donation drives that also contributed to the amount.[72] The Mexican diaspora in the United States contributed to Guízar's fund, among them, the San Antonio-based Spanish-language newspaper La Presna raised US$15,000 (equivalent to $228,140 in 2023). In Teocelo, he officiated a sermon and distributed US$1,496 (equivalent to $22,753 in 2023) to residents.[48] The El Salvador and Honduras government and Red Cross donated US$10,000 (equivalent to $152,093 in 2023) each while Pope Benedict XV donated an undisclosed amount.[49][48][73]

See also

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References

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  1. ^ Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1953.
  2. ^ National Seismological Service n.d., p. 1.
  3. ^ Huesca-Pérez et al. 2021.
  4. ^ Benz et al. 2011.
  5. ^ a b Pardo & Suárez 1995, p. 12357.
  6. ^ a b Tectonics Observatory 2009.
  7. ^ a b Suárez, Caballero-Jiménez & Novelo-Casanova 2019, p. 3545.
  8. ^ a b Castellanos, Clayton & Pérez-Campos 2018, p. 7741–7742.
  9. ^ a b Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3545–3546.
  10. ^ Suter et al. 2001, pp. 693.
  11. ^ Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1952.
  12. ^ a b c Viveros, Reynoso & Schroeder 2017, p. 90.
  13. ^ Agence France-Presse 2021.
  14. ^ a b Andrews 2019.
  15. ^ Hernández & Rocha 2008, pp. 9.
  16. ^ a b c Viveros, Reynoso & Schroeder 2017, p. 88.
  17. ^ Suárez, Caballero-Jiménez & Novelo-Casanova 2019, p. 3547.
  18. ^ a b c Suárez & Novelo-Casanova 2018, pp. 1896–1897.
  19. ^ ISC 2022.
  20. ^ Córdoba-Montiel et al. 2018, p. 93.
  21. ^ Suárez & Novelo-Casanova 2018, pp. 1897–1898.
  22. ^ Suárez & Novelo-Casanova 2018, p. 1897.
  23. ^ a b Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1956.
  24. ^ a b Flores & Camacho 1922, p. 94–95.
  25. ^ a b Flores & Camacho 1922, p. 24.
  26. ^ Córdoba-Montiel et al. 2018, p. 90.
  27. ^ Flores & Camacho 1922, p. 25.
  28. ^ Suárez & Pérez-Campos 2020, p. 6.
  29. ^ Córdoba-Montiel et al. 2018, p. 92.
  30. ^ Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3545–3547.
  31. ^ Suárez & Novelo-Casanova 2018, p. 1894.
  32. ^ Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3547–3556.
  33. ^ Singh et al. 2015, pp. 294.
  34. ^ a b Flores et al. 2019, p. 96.
  35. ^ Stevens 2017.
  36. ^ "Report Mexican village swallowed by earthquake". Biddeford Weekly Journal. Vol. LXXV, no. 11. 9 January 1920. p. 7. Retrieved 28 November 2024.
  37. ^ "Mexican earthquake". Colonist. Vol. LXII, no. 15272. 12 January 1920. p. 5. Retrieved 28 November 2024.
  38. ^ Fernanda, R. R. (28 December 2019). "El terremoto que sacudió hace 100 años a Veracruz y Puebla" [The earthquake that shook Veracruz and Puebla 100 years ago]. El Universal (in Spanish). Retrieved 28 November 2024.
  39. ^ "Death toll from eruptions large". The Newburgh Daily News. No. 10582. 9 January 1920. p. 1. Retrieved 28 November 2024.
  40. ^ a b c Flores et al. 2019, p. 101.
  41. ^ a b Suárez & Novelo-Casanova 2018, p. 1896.
  42. ^ Suárez, Caballero-Jiménez & Novelo-Casanova 2019, pp. 3558.
  43. ^ Suter, Carrillo-Martfnez & Quintero-Legorreta 1996, p. 1955.
  44. ^ Miyamura 1988, p. 401–419.
  45. ^ Torres et al. 2012, p. 2.
  46. ^ ANSS. "1985 M 8.0 – 26 km NW of El Habillal, Mexico". Comprehensive Catalog. U.S. Geological Survey.
  47. ^ National Seismological Service n.d., p. 5.
  48. ^ a b c d e f g h i Foreign exchange rates, 1922–1929 (PDF), Federal Reserve Bulletin, Federal Reserve Board, 1929
  49. ^ a b c "Mexican earthquake". The Catholic Telegraph. Vol. 89, no. 5. 5 February 1920.
  50. ^ Sánchez 2022.
  51. ^ a b Flores et al. 2019, p. 100.
  52. ^ a b c Flores & Camacho 1922, p. 90–92.
  53. ^ a b c Carrasco-Núñez et al. 2006, pp. 161.
  54. ^ Flores & Camacho 1922, p. 37.
  55. ^ Flores et al. 2019, pp. 101–102.
  56. ^ Flores & Camacho 1922, p. 30–31.
  57. ^ a b Flores & Camacho 1922, p. 86–87.
  58. ^ Flores & Camacho 1922, p. 33–34.
  59. ^ a b Flores et al. 2019, p. 103.
  60. ^ Flores & Camacho 1922, p. 84–85.
  61. ^ a b c Flores et al. 2019, p. 104.
  62. ^ Flores & Camacho 1922, p. 34–35.
  63. ^ "Two villages destroyed and scores killed when earthquake shook Mexico". Edmonton Journal. Vol. 16, no. 145. 5 January 1920. p. 1. Retrieved 28 November 2024.
  64. ^ Flores et al. 2019, p. 106.
  65. ^ a b Flores et al. 2019, p. 109.
  66. ^ Flores et al. 2019, p. 115–116.
  67. ^ Flores et al. 2019, p. 109–110.
  68. ^ Flores et al. 2019, p. 111.
  69. ^ Flores et al. 2019, p. 105.
  70. ^ Flores et al. 2019, p. 95.
  71. ^ Flores et al. 2019, p. 111–112.
  72. ^ Freixa & Redondo 2021, pp. 112.
  73. ^ "Red Cross sends $10,000 for Mexico quake victims". No. United Press. The Pittsburgh Press. 18 January 1920. p. 71. Retrieved 28 November 2024.

Sources

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