2012 El Salvador earthquake

A convergent plate margin extends along the west coast of Central America where two tectonic plates collide. Oceanic lithosphere of the Cocos plate subducts beneath the continental crust of Central America. This continental crust is part of the Caribbean plate. Subduction occurs along the Middle America Trench, and the Cocos plate moves towards Central America at an estimated {{cvt|8.23 ± 0.22|cm}} per year.{{cite journal |last1=Zamora|first1= N.|last2= Babeyko|first2= A.Y. |title=Tsunami potential from local seismic sources along the southern Middle America Trench |journal=Natural Hazards |date=2016 |volume=80 |issue=2 |pages=901–934 |doi=10.1007/s11069-015-2004-3 |bibcode=2016NatHa..80..901Z |s2cid=130969961 |url=https://link.springer.com/content/pdf/10.1007/s11069-015-2004-3.pdf |access-date=21 April 2021}} The subduction zone is seismically active and has been responsible for large and tsunamigenic earthquakes when it ruptures. One of these large earthquakes affected Nicaragua in 1992, measuring {{M|w}} 7.6 and caused a destructive tsunami.{{cite journal |last1=Satake |first1=Kenji |title=Mechanism of the 1992 Nicaragua Tsunami Earthquake |journal=Geophysical Research Letters |date=15 November 1994 |volume=21 |issue=23 |pages=2519–2522 |doi=10.1029/94GL02338 |bibcode=1994GeoRL..21.2519S |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/94GL02338 |access-date=21 April 2021}}

File:Terremoto El Salvador 2012.jpg

The earthquake occurred in the Pacific Ocean, more than {{cvt|120|km}} south of El Salvador's Usulután department, on 26 August at 22:37 CST.

A 2013 study published in Earth and Planetary Science Letters determined that the earthquake ruptured a west–northwest striking, northeast dipping fault plane by applying seismic inversion on 83 broadband P-wave records. This rupture model corresponded to the shallow portion of the megathrust closest to the seafloor. The rupture extended along the megathrust from a depth of {{cvt|23|km}} towards the trench and propagated through the fault at {{cvt|2|km}} per second. The model determined that an approximately {{cvt|50|km}} length of the megathrust produced slip of up to {{cvt|1.2|m}}. This event released energy slower and with a longer duration relative to the megathrust earthquakes of Guatemala and Costa Rica several months later; those exhibited a typical quick energy release. The study concluded that the El Salvador event displayed tsunami earthquake characteristic similar to the shock that affected Nicaragua in 1992.{{cite journal |last1=Ye|first1= Lingling|last2= Lay|first2= Thorne|last3= Kanamori|first3= Hiroo |title=Large earthquake rupture process variations on the Middle America megathrust |journal=Earth and Planetary Science Letters |date=2013 |volume=381 |pages=147–155 |doi=10.1016/j.epsl.2013.08.042 |url=https://websites.pmc.ucsc.edu/~thorne/TL.pdfs/YLK_MAT_EPSL2013.pdf |bibcode=2013E&PSL.381..147Y}}

Multiple eyewitnesses on the peninsula described the shaking as light. One compared it to a swaying boat lasting 30 to 40 seconds, another said suspended light fixtures swayed and corrugated metal roofing vibrated. A sea turtle hatchery worker at Corral de Mulas claimed the shaking persisted for two to three minutes. According to residents living in San Salvador, the earthquake was not perceived at all or it was felt weakly.{{cite news |first=Juan Andrés |last=Muñoz |title=Un sismo de magnitud 7,4 sacude El Salvador; se cancela la alerta de tsunami |trans-title=A 7.4 magnitude earthquake shakes El Salvador; tsunami warning is canceled |url=https://cnnespanol.cnn.com/2012/08/27/un-sismo-de-magnitud-74-sacude-el-salvador/ |access-date=21 April 2021 |publisher=CNN Español |date=27 August 2012 |language=es}} Servicio Nacional de Estudios Territoriales evaluated the shaking in San Salvador to be II (Weak) on the Modified Mercalli intensity scale.{{cite news |first1=R |last1=Pineapple |first2= A. |last2= Cavajal |first3=G. |last3=Melgar |title=Un fuerte terremoto de magnitud 7,4 sacude la costa de El Salvador |trans-title=A strong 7.4 magnitude earthquake shakes the coast of El Salvador |url=https://www.elmundo.es/america/2012/08/27/noticias/1346045180.html |access-date=21 April 2021 |agency=El Mundo |date=27 August 2012 |language=es}} Similarly, witnesses of the 1992 shock described weak shaking, a characteristic of tsunami earthquakes.{{cite journal |last1=Borrero|first1= J.C.|last2= Kalligeris|first2= N.|last3= Lynett|first3= P.J. |title=Observations and Modeling of the August 27, 2012 Earthquake and Tsunami affecting El Salvador and Nicaragua |journal=Pure and Applied Geophysics |date=2014 |volume=171 |issue=12 |pages=3421–3435 |doi=10.1007/s00024-014-0782-2 |bibcode=2014PApGe.171.3421B |s2cid=1554690}}

Eight minutes after the earthquake, at 22:45, the Pacific Tsunami Warning Center (PTWC) issued an advisory along the Central American coasts. They evaluated that the event as a slow earthquake at 22:47. Eleven minutes later, the PTWC raised their advisory to a tsunami warning after receiving strong evidence of its rupture characteristic. The warning was cancelled at 00:27 after there was no indication of significant damage. There was only two tide gauges at Acajutla and La Union; an amplitude of {{cvt|14|cm}} was recorded at the former location while no tsunami was detected on the latter gauge. No tide gauges were installed at the coast nearest to the epicenter. A {{cvt|40|cm}} tsunami was recorded at the Galapagos Islands three hours later.{{cite journal |author1=Francisco Gavidia-Medina |title=Field survey report of tsunami effects caused by the August 2012 offshore El Salvador earthquake |journal=Science of Tsunami Hazards |date=2015 |volume=34 |issue=4 |pages=231–255 |url=http://www.tsunamisociety.org/344Gavidia.pdf |access-date=22 April 2021}} The tsunami impacted a sparsely populated part of the Salvadorian coast, while in Nicaragua, three coastal settlements experienced {{cvt|0.5|m}} of flooding.

Along the coast of the San Juan del Gozo Peninsula, Usulután, close to the epicenter, the tsunami had greater coastal effects. Several conservationists were collecting sea turtle eggs along the beach when the tsunami struck.{{cite news |author1=DPA |title=Experts confirm that there was a tsunami in El Salvador after the August earthquake|trans-title=Expertos confirman que hubo tsunami en El Salvador tras sismo de agosto |url=https://www.emol.com/noticias/internacional/2012/09/11/560078/expertos-confirman-que-hubo-tsunami-en-el-salvador-durante-terremoto-de-agosto.html |access-date=21 April 2021 |agency=El Mercurio On-Line |date=11 September 2012 |language=es}} The Ministry of Natural Resources investigated 11 sites on the peninsula. These sites shared similar geomorphology; these beaches were steep-sloped and had black sand, atop the berm was a dune crest, and the terrain was relatively flat or slightly sloping beyond the berm. At a section of beach near La Maroma village, which hosted a sea turtle hatchery, the tsunami destroyed the walls of a ramada and tilted its wooden supports. A hatchery worker was carried by the tsunami for {{cvt|90|m}} and left suspended on a tree, while another person was swept inland. A civil protection coordinator said 40 people at the beach were injured including three who required medical treatment. The ministry also found evidence that the tsunami flooded as far as {{cvt|340|m}} inland.

A resident of El Retiro said two people and a horse were pulled down the beach by the tsunami. Another eyewitness in Corral de Mulas reported two waves with the second being the largest; they topped a fence post located {{cvt|1|m}} above the dune crest and several meters inland. Tsunami overwash and inundation was evident in the area. Similarly, the tsunami scattered debris near the beaches of Ceiba Doblada. In other parts of Ceiba Doblada, the tsunami deposited sand onto the terrain. At Isla de Mendez, the tsunami had an estimated height of {{cvt|6.32|m}} and penetrated {{cvt|350|m}} inland. A {{cvt|15|km}} stretch east and west of the area experienced {{cvt|3–6|m}} tsunami waves. Some {{cvt|25|km}} west, such as in the resort town of Costa del Sol, there was no damage.

• List of earthquakes in 2012
• List of earthquakes in El Salvador
• List of earthquakes in Nicaragua

{{Reflist}}

• [https://nctr.pmel.noaa.gov/elsalvador20120826/index.html El Salvador Tsunami, August 27, 2012 Main Event Page] (NOAA)
• [https://nctr.pmel.noaa.gov/elsalvador20120826/local.html El Salvador Tsunami, August 27, 2012 Local Impacts] (NOAA)
• {{EQ-isc-link|601626911}}

{{Earthquakes in 2012}}

Category:2012 earthquakes

Category:2012 tsunamis

Category:2012 in El Salvador

Category:Tsunami earthquakes

Category:Earthquakes in El Salvador

Category:Earthquakes in Nicaragua

Category:2012 in Nicaragua

Category:August 2012 in North America