 For years, scientists in the Pacific Northwest have been using GPS devices to track movements in hopes of predicting earthquakes. The GPS units measure and record the distance between different points along the Earth's surface. Using the recorded data, scientists can track changes in distance or elevation. The changes are usually a result of pressure building up along fault lines. By constantly monitoring the strain, scientists are aiming to identify the location of the future earthquake. Expanding from 20 to 450 over the past decade, the GPS units in the Pacific Northwest record movements as small as one-tenth of a millimeter. With an additional 60 units scheduled for installation this year, the scientists at Pacific Northwest Geodetic Array (PANGA) have access to highly technical GPS units that provide precise readings. If a fault moves a couple of centimeters, PANGA will be aware of the movement within five seconds. Using recorded GPS measurements, scientists discovered earthquakes that occur deep in the earth along a fault line called the Cascadia Subduction Zone. The Cascadia Subduction Zone, pictured right, runs from Vancouver Island down to Northern California. These Cascadia fault earthquakes, categorized as 'silent earthquakes,' occur about every 14 months but are so deep below the surface they went unnoticed. Although GPS units assist in identifying faults where pressure is continuously building, scientists have yet to predict the pressure's breaking point or the exact time when earthquakes will strike. However, with GPS technology constantly developing, scientists hope GPS units will eventually lead to the prediction of earthquake's time and location of eruption. | 
