#ShakeAlert focuses on eq shaking which is controlled by 3 main factors: magnitude, distance from the rupturing fault, and local ground conditions. These factors play a role in how hard and for how long a region will shake. (1/5)
During an earthquake, loose, soft soil will shake harder and longer than hard rock. Valleys will shake harder than mountains because of their sediment fill. Watch this video from @IRIS_EPO (2/5)
Liquefaction occurs when loosely packed, water-logged sediments at/near the surface lose their strength in response to strong ground shaking. Liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes. (3/5)
How do we find out which areas are prone to #liquefaction during a quake? One tool is a cone penetration test – in which a cone is pushed into the soil to measure resistance and calculate S-wave velocity. Weaker soils amplify #shaking and can cause considerable damage (4/5)
All USGS #ShakeAlert messages contain information about the estimated shaking a region will experience during an earthquake. The more field data we have about what the ground beneath your feet will do during a quake contributes to improving the ShakeAlert system. (5/5)
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