Magnitude 8.2 earthquake north of Iquique, Chile, April 2014

A major earthquake struck the north of Chile yesterday (1st April 2014), with intense shaking felt in the cities of Iquique and Arica. Less intense shaking was also felt across northern Chile and in Bolivia, Peru, Brazil and Costa Rica..The USGS maintains 'did you feel it?' pages, where anyone can report shaking that they have experienced. Here's the page for the 1st April earthquake: Did you feel it?. Initial reports placed the magnitude in the region of 8.0, with subsequent analysis upgrading this to 8.2. This USGS page will continue to be updated as further information on the earthquake becomes available. For comparison, the 2010 Maule (Chile) earthquake measured 8.8, the 2011 Tohoku (Japan) earthquake registered
9.0 and the largest ever instrumentally documented earthquake (Chile, 1960) reached 9.5. Earthquake magnitudes are measured on a logarithmic scale; the USGS provides a nice little calculator to compare any two magnitudes.

  

Location of the epicentre and distribution 
of shaking USGS ShakeMap          

Location of past Chilean ruptures
(Manuela Dziggel, GFZ)

The earthquake has generated a small, but locally damaging tsunami. Wave heights close to the epicentre have been reported on Twitter at about 2m, backed up by tide gauges at Iquique and Arica. A tsunami warning was initially issued by the Pacific Tsunami Warning Centre for Chile, Peru and Ecuador with further tsunami warnings or watches issued for Colombia, Costa Rica, Panama, Nicaragua, El Salvador, Guatamala, Mexico and Honduras, Antarctica, Pitcairn and French Polynesia. At the time of writing a tsunami advisory continues to be in effect for Hawaii, though a large tsunami is not expected. Near-real time tide gauge data is available from the IOC    

The tsunami hitting the Iquique tide gauge

The earthquake occurred in what is termed a 'seismic gap'. This is a segment of the interface between two plates that has not experienced a significant earthquake in recent times and has been identified as a location that may have a higher probability of imminent failure. The last rupture in this region occurred in 1877, devastating coastal infrastructure in northern Chilean cities, including Iquique. The lack of ruptures in this area since 1877 is discussed in papers by Kelleher (1972), Comte and Pardo (1991) and Chlieh et al (2004).