By Rachel Cronin

Copyright dailyrecord

A powerful 6.9-magnitude earthquake has hit off the coast of the Philippines, with those who live near the coast in Leyte and Cebu being warned to travel inland immediately. The earthquake is believed to have erupted at around 10pm local time and to have struck underwater. Cebu Governor Pam Baricuatro has urged the public to “remain calm” following the earthquake. She said in a Facebook post: “Please move to open areas, stay away from walls or structures that may collapse, and stay alert for possible aftershocks”, reports the Mirror. Manyareas of the Asian islands have been issued a ‘brown-out’, where electrical supply is restricted, and several buildings including a church have seen significant damage from the tremor. The worst-hit areas are believed to be northern parts of the Cebu and Leyte islands. Very strong shaking from the earthquake could bring “considerable damage in poorly built or badly designed structures,” said the US Geological Survey, which added that there could be “slight to moderate damage in well-built ordinary structures.” But as the earthquake makes headlines, many are wondering just how severe a 6.9-magnitude shock is, and how much damage it could cause. Here’s everything you need to know. BBC Bitesize explains that until recently, earthquakes were measured via a system called the Richter scale. The Richter scale measures an earthquake’s magnitude, in other words, how powerful the tremor is. Magnitude is measured using a machine called a seismometer which produces a seismograph, and the Richter scale indicates how powerful the quake is on a scale of 1-10. The scale is logarithmic, meaning that an earthquake measuring magnitude 5 is ten times more powerful than an earthquake measuring 4. Earthquakes measuring 1-2 on the scale happen regularly, and they are so small that people cannot usually feel them. Earthquakes measuring upwards of 7 are less frequent but very powerful, and can cause serious destruction. Today, the magnitude of a quake is more commonly measured through the Moment Magnitude Scale – a method that uses the same logarithmic scale as Richter, but which more accurately measures the strength of larger earthquakes. According to Michigan Tech , earthquakes with a magnitude of 6.1 to 6.9 “may cause a lot of damage in very populated areas”. They also estimate that the planet sees around 100 earthquakes in this category per year. To put this recent earthquake into context, the largest quake ever recorded was in Chile in 1960, which measured 9.5 on the Richter scale, and killed well over 1,000 people. Luckily, no tsunami warning has been issued following the recent underwater earthquake in the Philippines, but tremors with a magnitude this high have been known to come with the risk of triggering a tsunami.