A magnitude 6 earthquake struck eastern Afghanistan near the border with Pakistan just before midnight local time on Sunday, according to the United States Geological Survey. Several aftershocks followed.At least 800 people were killed and 2,500 were injured. The epicentre of the earthquake was at a depth of about 8km (5 miles), which seismologists consider shallow, making the ground shaking more intense and destructive, particularly for fragile homes and communities.Most earthquakes occur at shallow depths, and in this visual explainer, we show why those near the surface often cause more destruction than deeper ones, even when their magnitude is the same. How do earthquakes happen?An earthquake, in the simplest terms, happens when the Earth shakes.The surface of the Earth is made of kilometres of hard rock broken into a puzzle of moving pieces called tectonic plates, which sit on a sea of hot, liquid rock that rolls as it cools, pushing the plates around. Earthquakes and volcanoes occur on the surface where these plates meet.Plates are technically always in motion but are usually locked together, building stress until something underground snaps, freeing them to slide along known lines of fractured rock called faults, which can run for kilometres.When the pressure suddenly releases and the plate moves, energy explodes into the surrounding rock. How are earthquakes measured?Scientists use seismographs, which used to be wiggling needles that record the grou …
