Added by Erik West on July 20, 2012
A M6.1 (magnitude 6.1) earthquake rocked the Kruil Islands on Friday at approximately 06:10UTC/GMT. Reports of damage were not immediately available.
The earthquake’s epicentre, 17km below the ocean floor, was located 138km south of Severo-Kurilsk – a city on the island of Paramushir within the archipelago. The earthquake occurred in Russian controlled territory.
The islands are the summits of 100 volcanoes,; 40 of the 100 are active volcanoes.
The region, located within the Ring of Fire – a large area of tectonic instability that encircles the Pacific Ocean – experiences a number of earthquakes each year. The region has been rocked by eight earthquakes that had magnitudes near the end of the measurable range.
The most recent high-magnitude earthquake occurred in 2006 which created a tsunami wave of about 1.5m (5ft) high and reached the California coast.
Earthquakes used to be measured using the well-known Richter scale, which was simply a number on the scale. More recently, scientists have been measuring and reporting earthquake magnitudes using a scale called the Moment Magnitude Scale (MMS) which is measured in mega-watts (Mw) of energy. The Richter and MMS scales are said to have approximately equivalent values, yet the notation changes from a magnitude on the Richter scale, to a magnitude reported in Mw.
Map images: Google Inc