 So by now everyone has heard about GPS. People use it to find their local pizza store or cafe. We can use GPS to get really accurate positions on Earth and from that we can detect defamation of the continent caused by plate tectonic motion, crustal defamation and it can even tell us about earthquakes. So when an earthquake occurs there's a rupture at depth and that causes typically a surface defamation. There's all the shaking and buildings fall down and all the associated effects but it leaves a lasting trace on the surface of the Earth and with really accurate GPS positions we can measure exactly how far it moved and we can therefore determine what happened in the earthquake. We can also know in advance of an earthquake that something might happen. An earthquake occurs on a fault in the Earth and we can't see the faults but we know that they're there. Now on that fault there will be motion of two plates and the faults get locked, they get kind of stuck together and when that occurs at the further distance the plates are still moving and so it's building up stress and building up strain on the faults themselves and we can see that at the surface in the change in the motion of the sites using GPS at the surface. So if we can quantify that change we can then have some idea about what is happening at depth even though we can't see it. We can still detect it from the surface measurements and therefore we can quantify the buildup of strain on a fault and then make assumptions about how long it's been locked and that will tell us if an earthquake occurred and released all of that energy how big would it be. So we can predict not when but how big an earthquake might be. If we can identify where the locked faults are around the world then we can also identify the regions of the world that are affected by the strain buildup of faults that are locked and so that allows us to identify the particular places in the world that are at greatest risk of earthquake hazard and earthquake damage and also because we can quantify how much energy is building up we know something about how buildings need to be constructed for example what kind of building codes are necessary in order for the buildings to be able to survive whatever natural hazard might happen in that area.