Liquiñe-Ofqui Fault

{{Short description|Major geological fault in Northern Chile}}

{{Infobox fault

| name = Liquiñe-Ofqui Fault

| other_name = Falla de Liquiñe-Ofqui

| namedfor = Liquiñe, Ofqui

| namedby = Hervé et al.

| yeardef = 1979

| image = Falla Liquiñe-Ofqui.png

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| image_caption = Approximate extent of the Liquiñe-Ofqui Fault shown in red. Note that it is near parallel to the Peru-Chile Trench, the coastline, the Chilean Coast Range and the Andes

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| country = {{CHL}}

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| range = Andes

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| length = {{convert|1200|km|mi|abbr=on}}

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| plate = South American

| status = Active

| earthquakes = 1960 Valdivia earthquake aftershock, 2007 Aysén Fjord earthquakes

| type = Intra-arc strike-slip fault

| movement = Dextral

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| orogeny = Andean

| volcanic_arc/belt = Southern Volcanic Zone

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The Liquiñe-Ofqui Fault is major geological fault that runs a length of roughly {{convert|1200|km|mi}} in a NNE-SSW orientation and exhibits current seismicity.{{cite journal| last = Lange| first = D. |author2=Cembrano, J. |author3=Rietbrock, A. |author4=Haberland, C. |author5=Dahm, T. |author6=Bataille, K| title = First seismic record for intra-arc strike-slip tectonics along the Liquiñe-Ofqui fault zone at the obliquely convergent plate margin of the southern Andes| journal = Tectonophysics|date=April 2008| volume = 455| issue = 1–4| doi = 10.1016/j.tecto.2008.04.014| pages = 14|bibcode = 2008Tectp.455...14L | hdl = 10533/139825| hdl-access = free}}{{cite journal |last1=Pérez-Flores |first1=Pamela |last2=Cembrano |first2=José|last3=Sánchez-Alfaro |first3=Pablo|last4=Veloso |first4=Eugenio|last5=Arancibia |first5=Gloria|last6=Roquer |first6=Tomás |date=2016 |title=Tectonics, magmatism and paleo-fluid distribution in a strike-slip setting: Insights from the northern termination of the Liquiñe–Ofqui fault System, Chile |url=http://repositorio.uchile.cl/bitstream/handle/2250/141877/Tectonics-magmatism-and-paleo-fluid-distribution.pdf?sequence=1 |journal=Tectonophysics |volume=680 |pages=192–210 |doi=10.1016/j.tecto.2016.05.016 |access-date=June 1, 2018|bibcode=2016Tectp.680..192P}} It is located in the Chilean Northern Patagonian Andes. It is a dextral intra-arc strike-slip fault. Most large stratovolcanoes of the Southern Volcanic Zone of the Andes are aligned by the fault which allows for the movement of magma and hydrothermal fluids.

The fault crosses several transverse faults including the Mocha-Villarrica Fault Zone (MVFZ) and the Biobío-Aluminé Fault Zone. The fault has had periods of ductile deformation associated to pluton emplacement, be it either at great depths or by shallow intrusions.{{cite journal |last1=Adriasola |first1=Alberto C. |last2=Stockhert |first2=Bernhard |date=2008 |title=Cooling histories and deformation of plutonic rocks along the Liquiñe-Ofqui Fault Zone, Southern Chile (41°-42°15'S) |journal=Revista Geológica de Chile |volume=35 |issue=1 |pages=39–61 |doi= 10.4067/s0716-02082008000100002|doi-access=free }}

The forces that move the fault are derivative of the oblique subduction offshore Chile's coast. This leads to partition of deformation between the subduction zone, the fore-arc and the intra-arc region where the fault lies. There is evidence that the fault broke as a {{M|w|}}9.07 subevent in the 1960 Valdivia earthquake.{{cite journal |last1=Kanamori |first1=Hiroo |title=Evidence for a large strike-slip component during the 1960 Chilean earthquake |journal=Geophysical Journal International |date=July 2019 |volume=218 |issue=1 |pages=1–32 |doi=10.1093/gji/ggz113 |doi-access=free |url=https://www.researchgate.net/publication/334143123 |access-date=9 July 2022}} A portion of the fault in Aysén Region likely slipped (moved) in an aftershock a few weeks after the 1960 Valdivia earthquake.{{cite journal |last1=Kanamori |first1=Hiroo |last2=Rivera |first2=Luis |date=2017 |title=An Mw =7.7 slow earthquake in 1960 near the Ays´en Fjord region, Chile |url=https://authors.library.caltech.edu/82533/1/ggx292.pdf |journal=Geophysical Journal International |volume=211 |pages=93–106 |doi= 10.1093/gji/ggx292|doi-access=free |access-date=March 29, 2019}} This same portion slipped again in April 2007, causing earthquakes in Aysén Fjord, triggering landslides and a local tsunami.

The fault name was coined by Francisco Hervé, I. Fuenzalida, E. Araya and A. Solano in 1979.{{cite journal |last1=Hauser |first1=A. |date=1991 |title=Hans Steffen, precursor del concepto falla Liquiñe-Ofqui |url=http://www.andeangeology.cl/index.php/revista1/article/viewFile/2492/2697 |journal=Revista Geológica de Chile|language=es |volume=18 |pages=177–179 }} The existence of the fault was first inferred by Chilean government agent Hans Steffen around 1900, who referred to it as a "tectonic furrow" (Spanish: surco tectónico).