The United States Geological Survey recorded a Magnitude 5.1 Earthquake at a depth of 169.4 km approximately 10 km to the northeast of the town of Aratoca in Santander Department, Colombia, slightly before 8.00 am local time (slightly before 1.00 am GMT) on Monday 8 January 2018. There are no reports of any damage or casualties associated with this event, but people have reported feeling the event across much of northern Colombia and parts of western Venezuela.
The approximate location of the 8 January 2018 Santander Earthquake. USGS.
Colombia is on the west coast of South America and the western margin of the South American Plate, close to where the Nazca Plate, which underlies part of the east Pacific, is being subducted along the Peru-Chile Trench. The Nazca Plate passes under the South American Plate as it sinks into the Earth, this is not a smooth process and the plates repeatedly stick together then break apart as the pressure builds up, causing Earthquakes. As the Nazca Plate sinks further it is partially melted by the friction and the heat of the Earth's interior. Some of this melted material then rises through the overlying South American Plate, fuelling the volcanoes of Colombia and neighbouring countries.
The subduction of the Nazca Plate beneath the South American Plate, and how it causes Earthquakes and volcanoes. SIO SEARCH.
Witness accounts of Earthquakes can help geologists to understand these events, and the structures that cause them. The international non-profit organisation Earthquake Report is interested in hearing from people who may have felt this event; if you felt this quake then you can report it to Earthquake Report here.