1917 San Salvador earthquake
 Ruins of buildings in San Salvador | |
  San Salvador  | |
| UTC time | 1917-06-08 00:51:44 |
|---|---|
| ISC event | 913530 |
| USGS-ANSS | ComCat |
| Local date | June 7, 1917 |
| Local time | 18:55 CST |
| Magnitude | 6.7 Mw |
| Depth | 15 km (9.3 mi) |
| Epicenter | 13°48′07″N 89°21′40″W / 13.802°N 89.361°W [1] |
| Areas affected | El Salvador |
| Casualties | 1,050 killed |
The 1917 San Salvador earthquake occurred on June 7 at 18:55 local time near the Salvadoran capital. The hypocenter of the Mw 6.7 was at a shallow depth of 15 km (9.3 mi), and occurred along a shallow crustal fault near San Salvador. The earthquake caused significant destruction of the city and left approximately 1,050 dead. It was followed by an eruption on San Salvador that killed another 1,100. Only behind the earthquake of 1986, it is the second deadliest in El Salvador's history.[2]
Earthquake
[edit]There were two earthquakes felt in the San Salvador area on 6 June; one at 18:55 and 19:10.[3] The largest earthquake was the first event, recorded at Mw 6.7.[1] The latter event was a Ms 6.3 aftershock. Another Ms 6.0 aftershock was centered around San Jacinto Hill, close to the epicenter of the 1986 shock.[4]
Geology
[edit]Subduction of the Cocos Plate beneath the Caribbean Plate is associated with a volcanic arc that extends from Costa Rica to Guatemala. Across the Central America Volcanic Arc, there are three major geological structures; the Nicaraguan depression, El Salvador Fault Zone and Jalpatagua Fault. The El Salvador Fault Zone represents an area of geological strain with a dimension of 150 km (93 mi) by 20 km (12 mi). Earthquakes in the volcanic arc are concentrated within this region.[5]
The fault zone predominantly comprise east to southeast-striking strike-slip faults. Some southeast to southeast-striking normal faults also occur. These faults are seismically active and was the source of the 13 February 2001 and 1917 earthquakes. Their displacement rates were estimated to be as high as 11 mm (0.43 in) annually and Mw 7.2 earthquakes are possible on these faults. One of these faults, the Guaycume Fault, is a possible source of the earthquake. The fault slips at a rate of 9 ± 3 mm (0.35 ± 0.12 in) per year, and is one of the most dangerous in El Salvador due to its proximity to San Salvador. Damage from the earthquake was mainly concentrated to the south of the fault while no major destruction was reported to its north. Near the fault, districts of Nejapa, Opico and Quezaltepeque experienced the greatest impact. Modelling of peak ground acceleration from an earthquake on the Guaycume Fault also indicated higher values to the south while lower values were predicted in the north.[5]
Impact
[edit]
An area 30–40 km (19–25 mi) west of San Salvador volcano suffered the greatest damage inflicted by the initial earthquake. San Salvador and the region to the north, including around the volcano were devastated by the aftershock.[4] At least 1,050 people died and left many injured. The towns of Santa Tecla, San Julián, Sacacoyo, Tepecoyo, Ateos, Caluco and San Vicente sustained significant damage.[6] Hundreds of people died in San Salvador.[7]
In the towns of Armenia and Quezaltepeque, 40 people were killed and over 100 were injured. Damage in San Salvador was severe; described as "80 out of every 100 homes" levelled. The business district of San Salvador was incinerated by fires.[8] Out of the 9,000 homes in San Salvador, only 200 remained standing. All government buildings with the exception of the national theater and palace withstood the earthquake. Hospitals, university buildings, schools, and other public buildings were razed. The National Palace, National Press building, President Residence and banks were also devastated.[6][7] Surviving buildings eventually toppled during the second major earthquake at 19:30.[9] In addition to damaged buildings, the local coffee plantations were ruined.[10] The earthquake was experienced by Colombian poet, Porfirio Barba-Jacob, who documented it in a book and the local newspaper Diario del Salvador.[11][6]
Volcanic eruption
[edit]At the San Salvador volcano, eruptive activity occurred after the second shock, at 20:11.[12]: 35 A fracture formed on the northwest flank of the Boquerón cone in the San Salvador volcano crater. The fissure later evolved into smaller craters. Lava erupted from the vent and flowed outwards in the direction of Sitio del Niño.[3] The eruption produced an ash cloud and lava flow extended some 8 km (5.0 mi) along the northern slopes of San Salvador. The eruption was the largest since 1671, and was possibly triggered by the earthquakes disrupting plumbing within the magma chamber.[4] About 6 km (3.7 mi) north of the vent, the lava flows buried a section of railroad.[3]
The eruption caused the Boquerón crater lake to evaporate and form a cinder cone in the crater named Boqueroncito—it ejected material up to 200 m (660 ft) high. Several people died when they were caught in the lava flows.[13] The eruption rated a 3 on the Volcanic explosivity index.[14] The lava flows also destroyed homes between Quezaltepeque and Sitio del Niño.[15] By 11 June, the eruption had generally subsided, and the lava flows affected a 16 km2 (6.2 sq mi) area, burying it under ʻaʻā. A few of the craters had merged while some occasionally produced explosions. Two craters at the southern part of the fracture displayed fumarolic activity. One of these eruptive craters, El Tornador, located at 580–650 m (1,900–2,130 ft) in elevation, continued to produce lava and Strombolian explosions. Localised earthquakes were also felt.[3] Explosions on 28 and 29 June expelled volcanic material 200 m (660 ft) into the air. The eruptions continued until November.[12]: 36–37
See also
[edit]
References
[edit]- ^ a b ISC-GEM Global Instrumental Earthquake Catalogue (1904–2018), Version 9.0, International Seismological Centre
- ^ Huezo, Carlos M. (2004). "Sismos en El Salvador 1900-2001: contexto" (PDF). Servicio Nacional de Estudios Territoriales. Retrieved 17 September 2022.
- ^ a b c d Roy, Sharat Kumar (30 August 1957), "A Restudy of the 1917 Eruption of Volcán Boquerón, El Salvador, Central America", Fieldiana: Geology, 10 (30), Chicago Natural History Museum: 363–381
- ^ a b c White, Randall A.; Harlow, David H.; Alvarez, Salvador (1987). "The San Salvador Earthquake of October 10, 1986—Seismological Aspects and Other Recent Local Seismicity". Earthquake Spectra. 3 (3): 419–434. Bibcode:1987EarSp...3..419W. doi:10.1193/1.1585439. S2CID 129240737.
- ^ a b Alonso-Henar, J.; Benito, B.; Staller, A.; Álvarez-Gómez, J.A.; Martínez-Díaz, J.J.; Canora, C. (2018). "Large-magnitude crustal seismic sources in El Salvador and deterministic hazard scenarios". Engineering Geology. 243: 70–83. Bibcode:2018EngGe.243...70A. doi:10.1016/j.enggeo.2018.06.015. S2CID 134683242.
- ^ a b c Cañas-Dinarte, Carlos. "El Salvador: cronología de una tierra danzarina". El Diario de Hoy. Retrieved 17 September 2022.
- ^ a b National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), Significant Earthquake Database (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5TD9V7K
- ^ "June 9, 1917 Newspaper Clippings". Department of Earth and Atmospheric Sciences, Saint Louis University. 9 June 1917. Archived from the original on 5 December 2022. Retrieved 17 September 2022.
- ^ Lardé y Larín, Jorge (2000). "El Salvador: inundaciones e incendios, erupciones y terremotos". El Salvador: descubrimiento, conquista y colonización. Vol. 5. Consejo Nacional para la Cultura y el Arte. pp. 123–125. ISBN 9992300493.
- ^ Dinarte, Carlos Cañas (7 June 2020). "La erupción del volcán de San Salvador en 1917: la noche trágica de Corpus Christi" [The eruption of the San Salvador volcano in 1917: the tragic night of Corpus Christi]. El Mundo. Retrieved 17 September 2022.
- ^ Jacob, Porfirio-Barba (2001). El terremoto de San Salvador: narración de un superviviente. Villegas Editores. p. 238. ISBN 9789589393987.
- ^ a b Morán, Saúl Campos; Navarrete, Paola María; Osegueda, Carlos Felipe (2017). Etnografía del volcán de San Salvador [Ethnography of the San Salvador volcano]. Colección Investigaciones (in Spanish). Vol. 67. Technological University of El Salvador. ISBN 9996148777.
- ^ National Geophysical Data Center / World Data Service (NGDC/WDS) (1972), NCEI/WDS Global Significant Volcanic Eruptions Database. NOAA National Centers for Environmental Information (Data Set), National Geophysical Data Center, NOAA, doi:10.7289/V5JW8BSH
- ^ "San Salvador". Global Volcanism Program. Smithsonian Institution.
- ^ Barrera, Susana (21 June 2011). "A 94 años de la erupción del volcán de San Salvador" [94 years after the eruption of the San Salvador volcano] (in Spanish). ContraPunto. Archived from the original on 26 June 2011. Retrieved 17 September 2022.