| Buesaco-Aranda Fault | |
|---|---|
| Falla Buesaco-Aranda | |
  | |
| Etymology | Buesaco &vereda Aranda |
| Coordinates | 01°20′14.3″N77°11′36.8″W / 1.337306°N 77.193556°W /1.337306; -77.193556 |
| Country |  Colombia |
| Region | Andean |
| State | Nariño |
| Cities | Pasto |
| Characteristics | |
| Range | Central Ranges,Andes |
| Part of | Romeral Fault System |
| Length | 29 km (18 mi) |
| Strike | NE-SW |
| Dip | Vertical |
| Displacement | 1–5 mm (0.039–0.197 in)/yr |
| Tectonics | |
| Plate | North Andean |
| Status | Active |
| Earthquakes | 1995 Pasto (ML 5.0) |
| Type | Strike-slip fault |
| Movement | Dextral |
| Age | Quaternary |
| Orogeny | Andean |
TheBuesaco-Aranda Fault (Spanish:Falla Buesaco-Aranda) is a dextralstrike-slip fault in thedepartment ofNariño in southwesternColombia. The fault has a total length of 29 kilometres (18 mi) and runs along an average northeast to southweststrike in theCentral Ranges of the ColombianAndes. The 1995 Pasto earthquake is associated with the active fault showing high amounts of displacement. The earthquake caused seven fatalities.
The fault is named afterBuesaco andAranda, avereda of Pasto.[1] Other sources call the fault by the general name ofSilvia-Pijao Fault.[2]
The Buesaco-Aranda Fault, extends in a north-northeast to northeast direction from near theGaleras Volcano in southwestern Colombia. The Buesaco Fault is located 5 kilometres (3.1 mi) to the west of the Aranda Fault. On the eastern block of the Buesaco Fault, thebasement rock consists of basic volcanic,andesite and dark sedimentary rocks which probably developed in a marginal basin environment duringEarly Cretaceous time. On the western block of the fault are a group of low-grademetamorphic rocks which consist ofgreenschist,amphibolite,quartzite and blackschist, all ofPaleozoic age. The area is mostly covered by aPliocene blanket ofpyroclastic rocks and calc-alkaline lavas,Quaternarylahar deposits andfluvio-glacial deposits.[1]
The Buesaco-Aranda Fault has a very well-defined fault trace, with strongly deformed landforms of Pleistocene-Holocene age, clear breaks in slope along erodedfault scarps, and fault scarps facing both to the southeast or the northwest, which is a characteristic ofstrike-slip faults. Systematic right lateral deflections of some stream gullies, river channels, and ridges are visible. Offset features in confinedalluvial deposits and in recentalluvial fans have fresh scarp morphology. The net cumulative horizontal slip calculated is 188 ± 14 metres (617 ± 46 ft), with 160 ± 10 metres (525 ± 33 ft) of displacement in offset landforms along the Aranda Fault.[1] TheMorasurcovolcano is enclosed by the Buesaco and Aranda Fault segments.[3]
The last strong seismic event occurred on the Buesaco Fault near Pasto at 18:23 on March 4, 1995; the magnitude of the biggest shock was M 5.0.[4] Seven people died as a result of the earthquake and the aftershocks.[5]
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| Sources | Paris, Gabriel; Machette, Michael N.; Dart, Richard L.; Haller, Kathleen M. (2000).Map and Database of Quaternary Faults and Folds in Colombia and its Offshore Regions(PDF).USGS. pp. 1–66. Retrieved2017-06-20. Gómez Tapias, Jorge; Montes Ramírez, Nohora E.; Almanza Meléndez, María F.; Alcárcel Gutiérrez, Fernando A.; Madrid Montoya, César A.; Diederix, Hans (2015).Geological Map of Colombia.Servicio Geológico Colombiano. pp. 1–212. Retrieved2019-10-29. Various authors (2014).Enciclopedia de desastres naturales históricos de Colombia(PDF).Universidad del Quindío. pp. 1–21. Retrieved2017-06-20. | ||||||||||
